Api571 API571 ICP Material & Corrosion part a

Damage Mechanisms AffectingFixed Equipment in theRefining Industry影响炼油行业固定设备的损伤机理

2013年内部培训

Charlie Chong/ Fion Zhang

中国固有领土: 钓鱼岛

Charlie Chong/ Fion Zhang

中国固有领土: 钓鱼岛

印度支那不就是 “Indo-China” 吗?, 中华人民共和国不就是 “People Republic of China”. 这 “China” 或“支那” 不是歧视字眼.“支那”是个威震四方的大国,以前郑和下西洋的“支那“这是闻之丧胆字眼,现在我们也不渐渐变成”强大支那”了吗?. 小的时候(40年前),友族,善意的叫我“中华人”,我很善意的告诉他,我叫“支那人”,虽然我只是东南亚华裔,但我永远以“支那-China" 引以为荣. 我爱中国,我爱 "China" 我爱"支那".http://news.ifeng.com/world/detail_2014_03/20/34944726_0.shtml

影响炼油行业固定设备的损伤机理-2013年内部培训

http://www.smt.sandvik.com/en/search/?q=stress+corrosion+cracking

http://www.smt.sandvik.com/en/search/?q=stress+corrosion+cracking

Speaker: Fion Zhang2013/7/4

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For API 510 ICP - API RP 571, Damage mechanisms Affecting Fixed equipment in the Refining Industry ATTN: Examination questions will be based on the following sections only:

Par. 3. – Definitions (included as a frame of reference only) 4.2.3 – Temper Embrittlement 4.2.7 – Brittle Fracture 4.2.9 – Thermal Fatigue 4.2.14 – Erosion/Erosion-Corrosion 4.2.16 – Mechanical Failure 4.3.2 – Atmospheric Corrosion 4.3.3 – Corrosion Under Insulation (CUI) 4.3.4 – Cooling Water Corrosion 4.3.5 – Boiler Water Condensate Corrosion 4.3.10 – Caustic Corrosion 4.4.2 – Sulfidation4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC) 4.5.2 – Corrosion Fatigue 4.5.3 – Caustic Stress Corrosion Cracking (Caustic Embrittlement) 5.1.2.3 – Wet H2S Damage (Blistering / HIC/ SOHIC/ SSC) 5.1.3.1 – High Temperature Hydrogen Attack (HTHA)

For API 570 ICP - API RP 571, Damage mechanisms Affecting Fixed equipment in the Refining Industry ATTN: Examination questions will be based on the following sections only:

Par. 3 – Definitions (included as a frame of reference only) 4.2.7 – Brittle Fracture 4.2.9 – Thermal Fatigue 4.2.14 – Erosion/Erosion Corrosion 4.2.16 – Mechanical Fatigue 4.2.17 – Vibration-Induced Fatigue 4.3.1 – Galvanic Corrosion 4.3.2 – Atmospheric Corrosion 4.3.3 – Corrosion Under Insulation (CUI) 4.3.5 – Boiler Water Condensate Corrosion 4.3.7 – Flue Gas Dew Point Corrosion 4.3.8 – Microbiological Induced Corrosion (MIC) 4.3.9 – Soil Corrosion 4.4.2 – Sulfidation4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC) 4.5.3 – Caustic Stress corrosion Cracking (Caustic Embrittlement) 5.1.3.1 – High Temperature Hydrogen Attack (HTTA)

BODY OF KNOWLEDGE API-510 PRESSURE VESSEL INSPECTOR CERTIFICATION EXAMINATION August 2010 (Replaces January 2009)

Valentino

高亮

API RP 571, Damage Mechanisms Affecting Fixed equipment in the Refining IndustryATTN: API 510 Test questions will be based on the following mechanisms only: Par. 3. - Definitions (included as a frame of reference only)

1. 4.2.3 – Temper Embrittlement2. 4.2.7 – Brittle Fracture3. 4.2.9 – Thermal Fatigue4. 4.2.14 – Erosion/Erosion-Corrosion5. 4.2.16 – Mechanical Failure6. 4.3.2 – Atmospheric Corrosion7. 4.3.3 – Corrosion Under Insulation (CUI)8. 4.3.4 – Cooling Water Corrosion9. 4.3.5 – Boiler Water Condensate Corrosion10. 4.3.10 – Caustic Corrosion11. 4.4.2 – Sulfidation12. 4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC)13. 4.5.2 – Corrosion Fatigue14. 4.5.3 – Caustic Stress Corrosion Cracking (Caustic Embrittlement)15. 5.1.2.3 – Wet H2S Damage (Blistering/HIC/SOHIC/SCC)16. 5.1.3.1 – High Temperature Hydrogen Attack (HTHA)

BODY OF KNOWLEDGE API-570 AUTHORIZED PIPING INSPECTOR CERTIFICATION EXAMINATION August 2010 (Replaces June 2007)

Valentino

高亮

API RP 571, Damage mechanisms Affecting Fixed equipment in the Refining IndustryATTN: API 570 Examination questions will be based on the following sections only:

Par. 3 – Definitions (included as a frame of reference only)

1. 4.2.7 – Brittle Fracture2. 4.2.9 – Thermal Fatigue3. 4.2.14 – Erosion/Erosion Corrosion4. 4.2.16 – Mechanical Fatigue5. 4.2.17 – Vibration-Induced Fatigue6. 4.3.1 – Galvanic Corrosion7. 4.3.2 – Atmospheric Corrosion8. 4.3.3 – Corrosion Under Insulation (CUI)9. 4.3.5 – Boiler Water Condensate Corrosion10. 4.3.7 – Flue Gas Dew Point Corrosion11. 4.3.8 – Microbiological Induced Corrosion (MIC)12. 4.3.9 – Soil Corrosion13. 4.4.2 – Sulfidation14. 4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC)15. 4.5.3 – Caustic Stress corrosion Cracking (Caustic Embrittlement)

Par. 3. - Definitions 4.2.3 – Temper Embrittlement 4.2.7 – Brittle Fracture 4.2.9 – Thermal Fatigue 4.2.14 – Erosion/Erosion-Corrosion 4.2.16 – Mechanical Failure 4.3.2 – Atmospheric Corrosion 4.3.3 – Corrosion Under Insulation (CUI) 4.3.4 – Cooling Water Corrosion 4.3.5 – Boiler Water Condensate Corrosion 4.3.10 – Caustic Corrosion 4.4.2 – Sulfidation 4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC) 4.5.2 – Corrosion Fatigue 4.5.3 – Caustic Stress Corrosion Cracking 5.1.2.3 – Wet H2S Damage (Blister/HIC/SOHIC/SCC) 5.1.3.1 – High Temperature Hydrogen Attack (HTHA)

Par. 3 – Definitions 4.2.7 – Brittle Fracture 4.2.9 – Thermal Fatigue 4.2.14 – Erosion/Erosion Corrosion 4.2.16 – Mechanical Fatigue 4.2.17 – Vibration-Induced Fatigue 4.3.1 – Galvanic Corrosion 4.3.2 – Atmospheric Corrosion 4.3.3 – Corrosion Under Insulation (CUI) 4.3.5 – Boiler Water Condensate Corrosion 4.3.7 – Flue Gas Dew Point Corrosion 4.3.8 – Microbiological Induced Corrosion (MIC) 4.3.9 – Soil Corrosion 4.4.2 – Sulfidation 4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC) 4.5.3 – Caustic Stress corrosion Cracking 5.1.3.1 – High Temperature Hydrogen Attack (HTTA)

2013-API510 Examination2013- API570 Examination

API510

API510

300, 400 & Duplex SS containing ferrite phases

1000oF~ 1700oFSigma-Phase Embrittlementσ相脆化

C, C- ½ Mo, 400 SSBelow DTBTTBrittle Fracture


600oF~ 1000oF885oF embrittlement 脆性

Pre-1980’s C-steels with a large grain size and C- ½ Mo

Intermediate temperatureStrain Aging 延伸时效

2 ¼ Cr-1Mo low alloy steel, 3Cr-1Mo (lesser extent), & HSLA Cr-Mo-V rotor steels

650oF~ 1070oFTempered Embrittlement回火脆性

Low alloy steel up to 9% Cr850oF ~ 1400oFSpheroidisation 碳化物球状

Plain carbon steelC- ½ Mo

800oF for C Steel875oF for C ½ Mo Steel

Graphitisation 石墨化

Mechanical and Metallurgical Failure Mechanisms机械和冶金失效机理

API510

C-Steel and low alloy steel10oF (–120C) and 350oF (175oC)

CUI

austenitic stainless steels and duplex stainless steels

140oF (60oC) and 400oF (205oC)

CS, low alloy and 300 SSH2SO4-280oF (138oC), HCL-130oF (54oC).

Flue-gas dew-point corrosion

All metals and alloys.Cold liquid impinge on hot surface

Thermal Shock 温度突然变

Carbon steel / 300 SS junctionOperating temperatureDissimilar Metal Weld (DMW) Cracking

Carbon steel and low alloy steels>1000oFSteam Blanketing 蒸汽遮盖

All fired heater tube materials and common materials of construction

>1000oFShort Term Overheating –Stress Rupture短期过热–应力破裂

All materials of constructionOperating temperatureThermal fatigues

All metals and alloys700oF ~ 1000oFCreep & stress rupture蠕变和应力断裂

High Temperature Corrosion [>400oF (204oC)]

API510

Carbon steels, low alloy steels, 300 Series SS and 400 Series SS

>600oF (316oC)Nitriding 渗氮

All metals and alloys> 700oF(371oC), varies with melting point of salts formed.

Fuel ash corrosion燃料灰腐蚀

All metals and alloys900oF ~1500oF（482oC~ 816oC）Metal dusting金属尘化

CS and low alloy steel?Decarburization 脱碳

All metals and alloys>1100oF (593oC)Carburization 渗碳

All metals and alloysIron based alloy 500oF (260oC).Others ?

Sulfidation 硫腐蚀

All metals and alloysCS - >1000oF (538oC)300SS- >1500oF (816oC).

Oxidation 氧化

今日课程:

0900~1130hrs第一篇: 第一章至第三章- 大纲与定义第二篇: 第四章- 一般损伤机制 - 所有行业

1300~1700hrs第三篇: 第五章- 炼油行业损坏机理第四篇: Q&A 问与答

FOREWORD 前言

The overall purpose of this document is to present information on equipment damage mechanisms in a set format to assist the reader in applying the information in the inspection and assessment of equipment from a safety and reliability standpoint.

本文件的总体目标从安全性和可靠性的角度, 用预设的文件格式, 提供设备损坏机理信息,以协助读者应用此信息协助设备的(1) 检查和 (2) 评估.

这份文件反映了行业信息,但它不是一个强制性的标准或规范.这作业指导“Recommended practice 571” 是作为 API 检验规范如 API 510, API 570,API 653 和执行基于风险的检验API 580/API 581提供有用的信息

本出版物中包含的综合指导,考虑的事项有:

可能会影响工艺设备的损伤机理实用信息, 设备上, 有关可以预测到的损伤类型和损害程度, 如何从这些知识帮助选择正确的选择检验方法来

发现/鉴定与检测尺寸.

This publication contains guidance for the combined considerations of:

Practical information on damage mechanisms that can affect process equipment, 影响设备损坏机理的实用信息,

Assistance regarding the type and extent of damage that can be expected, and 协助确定设备潜在的损伤类别与损伤程度,

How this knowledge can be applied to the selection of effective inspection methods to detect size and characterize damage.通过上述的知识确定如何选用真确的探测方法来对损伤定型与定量.

值得留意的是此文件 API571没提到: 材料选择作为损坏机理的防范.同样的是, 在 ASME B31.3 300(6) Compatibility of materials with the service and hazards from instability of contained fluids are not within the scope of this Code. See para. F323. 材料的兼容性对因所含流体(媒介)不稳定造成的危害,不在本规范范围内.

Table of contents 目录

1.0 Introduction and scope 简介及范围2.0 References 参考3.0 Definition of terms and abbreviations

定义,术语和缩略语4.0 General damage mechanisms – all industries

一般损伤机制 - 所有行业5.0 Refining industry damage mechanisms

炼油行业损坏机理

Appendix a – technical inquiries附录A - 技术咨询

SECTION 1.0Introduction and scope 简介及范围

1.1 Introduction 序言

ASME 和 API 加压设备的设计规范和标准-提供设计,制造,检验和测试 “新的” 压力容器,管道系统和储罐的规则. 这些规范不解决设备在服务期间设备的老化, 腐蚀,损坏等的考虑.这 RP主要针对在役设备上述信息.

在执行适用性评价(FFS),基于风险的检验 (RBI), 也提供需要的信息.因为:

进行 FFS/ API RP 579- FFS 评估第一步是确定(1) 缺陷类型和 (2) 损坏的原因. 基于风险的检验 (RBI) 第一个步骤也是正确的识别系统设备损伤机理或其他形

式的恶化原因.

当进行FFS/RBI评估时也作为重点:

观察到的或预测的损坏的原因未来进一步损坏的可能性和损坏程度

化工设施的材料/环境条件相互作用非常多样化.许多不同的处理单元各有其自身的进取过程,媒介组合,不同的温度/压力条件这些不确定因素带给FFS/RBI评估带来一些难度.

当设备观察到的缺陷时,这缺陷可能是:

使用前新建造,本来缺陷, 在职服务导致的后来缺陷.

在役服务导致的后来缺陷原因有:

设计不足的因素- (包括材料的选择和缺乏设计详细考虑) 设备运行中的腐蚀性的环境/条件引起 - (正常的服务或瞬态期间)

In general, the following types of damage are encountered inpetrochemical equipment: 化工设备一般损伤类型

1. General and local metal loss due to corrosion and/or erosion,由于腐蚀和/或侵蚀均匀与局部金属减薄

2. Surface connected cracking, 表面连接开裂3. Subsurface cracking, 内表面开裂4. Microfissuring/microvoid formation, 微裂纹/微孔形成5. Metallurgical changes. 金相变化

基于外观或形态, 损伤分类

基于引发因素, 损伤分类

SECTION 4.0GENERAL DAMAGE MECHANISMS – ALL INDUSTRIES 一般损伤机制 - 所有行业4.2 Mechanical and Metallurgical Failure Mechanisms. 机械和冶金失效机制4.3 Uniform or Localized Loss of Thickness. 均衡或局部厚度亏损4.4 High Temperature Corrosion [400°F (204°C)].高温腐蚀4.5 Environment Assisted Cracking. 环境辅助开裂

SECTION 5.0REFINING INDUSTRY DAMAGE MECHANISMS炼油工业的损伤机制5.1.1 Uniform or Localized Loss in Thickness Phenomena均匀或局部现象损失厚度5.1.2 Environment-Assisted Cracking 环境辅助开裂

General and local metal loss/ 均匀与局部减薄

General and local metal loss/均匀与局部减薄

General and local metal loss/ 均匀与局部减薄

Surface connected cracking

Surface connected cracking

Corrosion fatigue cracks have little branching

SCC cracks have highly branch

SCC or fatigue cracks nucleate at stress concentration points

subsurface cracking

Microfissuring/microvoid formation

http://www.aws.org/wj/supplement/WJ_1985_04_s91.pdfMicrofissuring/microvoid formation

Microfissuring/microvoid formation http://www.aws.org/wj/supplement/WJ_1985_04_s91.pdf

Metallurgical changes

Each of these general types of damage may be caused by a single or multiple damage mechanisms. In addition, each of the damage mechanisms occurs under very specific combinations of materials,process environments, and operating conditions.

每个损伤,可能是由一个或多个损坏机理造成.每一个损伤机制有非常具体的(1)材料 (2)过程环境和 (3)操作条件,的组合下发生.

1.2 Scope 范围

This recommended practice provides general guidance as to the most likely damage mechanisms affecting common alloys used in the refining and petrochemical industry and is intended to introduce the concepts of service-induced deterioration and failure modes. These guidelines provide information that can be utilized by plant inspection personnel to assist in identifying likely causes of damage; to assist with the development of inspection strategies; to help identify monitoring programs to ensure equipment integrity. 此规范对石油化工行业常用材料在役损蚀与失效最可能的损坏机理一般指导. 协助检验人员识别可能导致伤害的原因, 从而确定检测策略, 以确保设备的完整性.

The summary provided for each damage mechanism provides the fundamental information required for an FFS assessment performed in accordance with API 579-1/ASME FFS-1 or an RBI study performed in accordance with API RP 580. 每个损伤机理的总结作为提供RBI/FFS评估所需的基本信息.

API571,此规范对石油化工行业常用材料在役损蚀与失效最可能的损坏机理一般指导. 协助检验人员识别可能导致伤害的原因, 从而确定检测策略, 以确保设备的完整性.

1.3 Organization and Use 格式和使用

The information for each damage mechanism is provided in a set format as shown below. This recommended practice format facilitates use of the information in the development of inspection programs, FFS assessment and RBI applications.

为了协助 (1) 检验计划的开发/ (2) FFS 使用性评估 (3) RBI 基于风险分析检验的运用, 个别的损坏机理的信息提供的格式如下:

a) Description of Damage – a basic description of the damage mechanism.损伤机理的基本描述

b) Affected Materials – a list of the materials prone to the damage mechanism.受影响的材料

c) Critical Factors – a list of factors that affect the damage mechanism (i.e. rate of damage).破坏机理的影响因素列表

d) Affected Units or Equipment – a list of the affected equipment and/or units where the damage mechanism commonly occurs is provided. 受影响的单元或设备

e) Appearance or Morphology of Damage – a description of the damage mechanism, with pictures in some cases, to assist with recognition of the damage.外观或损伤形态学.

f) Prevention / Mitigation – methods to prevent and/or mitigate damage. 预防/缓解

g) Inspection and Monitoring – recommendations for NDE for detecting and sizing the flaw types associated with the damage mechanism.检查和监测

h) Related Mechanisms – a discussion of related damage mechanisms.相关的损伤机理讨论

i) References – a list of references that provide background and other pertinent information. 参考.

Damage mechanisms that are common to a variety of industries including refining and petrochemical, pulp and paper, and fossil utility are covered in Section 4.0. 通用炼油化工,纸浆和纸张,以及石化设施- 损坏机理信息

Damage mechanisms that are specific to the refining and petrochemical industries are covered in Section 5. 专门针对炼油和石化工业- 损坏机理信息

In addition, process flow diagrams are provided in 5.2 to assist the user in determining primary locations where some of the significant damage mechanisms are commonly found. 5.2 提供了一些工艺流程图主要的单元常见的一些重大损害机理.

提供损伤机理作为定性定量的信息提供损伤机理作为FFS/RBI 评估有用的信息提供损伤机理作为API510/ 570/ 653 在职设备检验有用的信息损伤机理可以分为5大类型设备损伤发现可能是源于新建或在职服务导致.

SECTION 2.0REFERENCES2.1 Standards2.2 Other References

2.1 Standards

API• API 530 Pressure Vessel Inspection Code• Std. 530 Calculation of Heater Tube Thickness in Petroleum Refineries• RP 579 Fitness-For-Service• Publ. 581 Risk-Based Inspection - Base Resource Document• Std. 660 Shell and Tube Heat Exchangers for General Refinery Service• RP 751 Safe Operation of Hydrofluoric Acid Alkylation Units• RP 932-B Design, Materials, Fabrication, Operation and Inspection

Guidelines for Corrosion Control in Hydroprocessing Reactor Effluent Air Cooler (REAC) Systems

• RP 934 Materials and Fabrication Requirements for 2-1/4 Cr-1Mo & 3Cr-1Mo Steel Heavy Wall Pressure Vessels for High Temperature, HighPressure Service

• RP 941 Steels for Hydrogen Service at Elevated Temperatures and Pressures in Petroleum Refineries and Petrochemical Plants

• RP 945 Avoiding Environmental Cracking in Amine Units

ASM• Metals Handbook Volume 1, Properties and Selection: Iron, Steels, and

High-Performance Alloys;• Volume 13, Corrosion in Petroleum Refining and Petrochemical Operations;• Volume 11, Failure Analysis and PreventionASME• Boiler and Pressure Vessel Code Section III, Division I, Rules for

Construction of Nuclear Power Plant Components; Section VIII, Division I, Pressure Vessels.

ASTM• MNL41 Corrosion in the Petrochemical Industry• STP1428 Thermo-mechanical Fatigue Behavior of MaterialsBSI• BSI 7910 Guidance on Methods for Assessing the Acceptability of Flaws in

Fusion Welded StructuresMPC• Report FS-26 Fitness-For Service Evaluation Procedures for Operating

Pressure Vessels, Tanks and Piping in Refinery and Chemical Service

NACE • Std. MR 0103 Materials Resistant to Sulfide Stress Cracking in Corrosive

Petroleum Refining Environments”• RP 0169 Standard Recommended Practice: Control of External Corrosion on

Underground or Submerged Metallic Piping Systems• RP 0170 Protection of Austenitic Stainless Steels and Other Austenitic Alloys from

Polythionic Acid Stress Corrosion Cracking during Shutdown of Refinery Equipment

• RP 0198 The Control of Corrosion Under Thermal Insulation, and Fireproofing – A Systems Approach

• RP 0294 Design, Fabrication, and Inspection of Tanks for the Storage of Concentrated Sulfuric Acid and Oleum at Ambient Temperatures

• RP 0296 Guidelines for Detection, Repair and Mitigation of Cracking of Existing Petroleum Refinery Pressure Vessels in Wet H2S Environments

• RP 0472 Methods and Controls to Prevent in-Service Environmental Cracking of Carbon Steel Weldments in Corrosive Petroleum Refining Environments

• Publ. 5A151 Materials of Construction for Handling Sulfuric Acid• Publ. 5A171 Materials for Receiving, Handling, and Storing Hydrofluoric Acid• Publ. 8X194 Materials and Fabrication

WRC• Bulletin 32 Graphitization of Steel in Petroleum Refining Equipment and

the Effect of Graphitization of Steel on Stress-Rupture Properties• Bulletin 275 The Use of Quenched and Tempered 2-1/4Cr-1Mo Steel for

Thick Wall Reactor Vessels in Petroleum Refinery Processes: An Interpretive Review of 25 Years of Research and Application

• Bulletin 350 Design Criteria for Dissimilar Metal Welds• Bulletin 409 Fundamental Studies Of The Metallurgical Causes And

Mitigation Of Reheat Cracking In 1¼Cr-½Mo And 2¼Cr-1Mo Steels• Bulletin 418 The Effect of Crack Depth (a) and Crack-Depth to Width Ratio

(a/W) on the Fracture Toughness of A533-B Steel• Bulletin 452 Recommended Practices for Local Heating of Welds in

Pressure Vessels

2.2 Other ReferencesA list of publications that offer background and other information pertinent to the damage mechanism is provided in the section covering eachdamage mechanism.

SECTION 3.0DEFINITION OF TERMS AND ABBREVIATIONS3.1 Terms3.2 Symbols and Abbreviations

3.1 Terms3.1.1 Austenitic奥氏体– a term that refers to a type of metallurgical structure (austenite) normally found in 300 Series stainless steels and nickel base alloys.

3.1.2 Austenitic stainless steels 奥氏体系不锈钢– the 300 Series stainless steels including Types 304, 304L, 304H, 309, 310, 316, 316L, 316H, 321, 321H, 347, and 347H. The “L” and “H” suffixes refer to controlled ranges of low and high carbon content, respectively. These alloys are characterized by an austenitic structure.

3.1.3 Carbon steel 碳素钢– steels that do not have alloying elements intentionally added. However, there may be small amounts of elements permitted by specifications such as SA516 and SA106, for example that can affect corrosion resistance, hardness after welding, and toughness. Elements which may be found in small quantities include Cr, Ni, Mo, Cu, S, Si, P, Al, V and B.

3.1.4 Di-ethanolamine二乙醇胺 (DEA) – used in amine treating to remove H2S and CO2 from hydrocarbon streams.

3.1.5 Duplex stainless steel 双相不锈钢– a family of stainless steels that contain a mixed austenitic-ferritic structure including Alloy 2205, 2304, and 2507. The welds of 300 series stainless steels may also exhibit a duplex structure.

3.1.6 Ferritic 铁素体– a term that refers to a type of metallurgical structure (ferrite) normally found in carbon and low alloy steels and many 400 series stainless steels.

3.1.7 Ferritic stainless steels 铁素体不锈钢– include Types 405, 409, 430, 442, and 446.

3.1.8 Heat Affected Zone (HAZ) – the portion of the base metal adjacent to a weld which has not been melted, but whose metallurgical microstructure and mechanical properties have been changed by the heat of welding, sometimes with undesirable effects.

0% Nickel-Ferrite铁素体

5% Nickel-Duplex双相(铁素/奥氏体)

>8% Nickel-Austenite奥氏体

Add Nickel Add Nickel

The 1949 Schaeffler diagram

http://www.intechopen.com/books/environmental-and-industrial-corrosion-practical-and-theoretical-aspects/corrosion-behaviour-of-cold-deformed-austenitic-alloys

3.1.9 Hydrogen Induced Cracking (HIC) 氢致开裂– describes stepwise internal cracks that connect adjacent hydrogen blisters on different planes in the metal, or to the metal surface. No externally applied stress is needed for the formation of HIC. The development of internal cracks (sometimes referred to as blister cracks) tends to link with other cracks by a transgranular plastic shear mechanism because of internal pressure resulting from the accumulation of hydrogen. The link-up of these cracks on different planes in steels has been referred to as stepwise cracking to characterize the nature of the crack appearance.

3.1.10 Low alloy steel 低合金结构钢– a family of steels containing up to 9% chromium and other alloying additions for high temperature strength and creep resistance. The materials include C-0.5Mo, Mn-0.5Mo, 1Cr-0.5Mo, 1.25 Cr-0.5Mo, 2.25Cr-1.0Mo, 5Cr-0.5Mo, and 9Cr-1Mo. These are considered ferritic steels.

3.1.11 Martensitic 马氏体– a term that refers to a type of metallurgical structure (martensite) normally found in some 400 series stainless steel. Heat treatment and or welding followed by rapid cooling can produce this structure in carbon and low alloy steels.

3.1.12 Martensitic stainless steel – include Types 410, 410S, 416, 420, 440A, 440B, and 440C.

3.1.13 Methyldiethanolamine (MDEA) – used in amine treating to remove H2S and CO2 from hydrocarbon streams.

3.1.14 Monoethanolamine (MEA) – used in amine treating to remove H2S and CO2 from hydrocarbon streams.

3.1.15 Nickel base alloy– a family of alloys containing nickel as a major alloying element ( Ni>30% ) including Alloys 200, 400, K-500, 800, 800H, 825, 600, 600H, 617, 625, 718, X-750, and C276.

Valentino

附注

Ferritic stainless steels 铁素体不锈钢– include Types 405, 409,430,442 and 446.

3.1.16 Stress oriented hydrogen induced cracking (SOHIC) 应力导向氢致开裂–describes an array of cracks, aligned nearly perpendicular to the stress, that are formed by the link-up of small HIC cracks in steel. Tensile strength (residual or applied) is required to produce SOHIC. SOHIC is commonly observed in the base metal adjacent to the Heat Affected Zone (HAZ) of a weld, oriented in the through-thickness direction. SOHIC may also be produced in susceptible steels at other high stress points, such as from the tip of the mechanical cracks and defects, or from the interaction among HIC on different planes in the steel.

3.1.17 Stainless steel 不锈钢– there are four categories of stainless steels that are characterized by their metallurgical structure at room temperature: austenitic, ferritic, martensitic and duplex. These alloys have varying amounts of chromium and other alloying elements that give them resistance to oxidation, sulfidation and other forms of corrosion depending on the alloy content.

3.2 Symbols and Abbreviations

3.2.1 ACFM – alternating current magnetic flux leakage testing.3.2.2 AE – acoustic emission.3.2.3 AET – acoustic emission testing.3.2.4 AGO – atmospheric gas oil.3.2.5 AUBT – automated ultrasonic backscatter testing.3.2.6 BFW – boiler feed water.3.2.7 C2 – chemical symbol referring to ethane or ethylene.3.2.8 C3 – chemical symbol referring to propane or propylene.3.2.9 C4 – chemical symbol referring to butane or butylenes.3.2.10 Cat – catalyst or catalytic.3.2.11 CDU – crude distillation unit.3.2.12 CH4 – methane.3.2.13 CO – carbon monoxide.3.2.14 CO2 – carbon dioxide.3.2.15 CVN – charpy v-notch.

Charlie Chong/ Fion Zhang571-3

3.2.16 CW – cooling water.3.2.17 DIB – deisobutanizer.3.2.18 DNB – Departure from Nucleate Boiling.3.2.19 DEA – diethanolamine, used in amine treating to

remove H2S and CO2 from hydrocarbon streams.3.2.20 EC – eddy current, test method applies primarily to non-

ferromagnetic materials.3.2.21 FCC – fluid catalytic cracker.3.2.22 FMR – field metallographic replication.3.2.23 H2 – hydrogen.3.2.24 H2O – also known as water.3.2.25 H2S – hydrogen sulfide, a poisonous gas.3.2.26 HAZ – Heat Affected Zone3.2.27 HB – Brinnell hardness numbe3.2.28 HCO – heavy cycle oil.3.2.29 HCGO – heavy coker gas oil.3.2.30 HIC – Hydrogen Induced Cracking

3.2.31 HP – high pressure.3.2.32 HPS – high pressure separator.3.2.33 HVGO – heavy vacuum gas oil.3.2.34 HSLA – high strength low alloy.3.2.35 HSAS – heat stable amine salts.3.2.36 IC4 – chemical symbol referring isobutane.3.2.37 IP – intermediate pressure.3.2.38 IRIS – internal rotating inspection system.3.2.39 K.O. – knock out, as in K.O. Drum.3.2.40 LCGO – light coker gas oil.3.2.41 LCO – light cycle oil.3.2.42 LP – low pressure.3.2.43 LPS – low pressure separator.3.2.44 LVGO – light vacuum gas oil.3.2.45 MDEA – methyldiethanolamine.3.2.46 MEA – monoethanolamine.3.2.47 mpy – mils per year.3.2.48 MT – magnetic particle testing

3.2.49 NAC – naphthenic acid corrosion.3.2.50 NH4HS – ammonium bisulfide.3.2.51 PMI – positive materials identification.3.2.52 PFD – process flow diagram.3.2.53 PT – liquid penetrant testing.3.2.54 RFEC – remote field eddy current testing.3.2.55 RT – radiographic testing.3.2.56 SCC – stress corrosion cracking.3.2.57 SOHIC – Stress Oriented Hydrogen Induced Cracking3.2.58 SS: – Stainless Steel.3.2.59 SW – sour water.3.2.60 SWS – sour water stripper.3.2.61 SWUT – shear wave ultrasonic testing.3.2.62 Ti – titanium.3.2.63 UT – ultrasonic testing.3.2.64 VDU – vacuum distillation unit.3.2.65 VT – visual inspection.3.2.66 WFMT – wet fluorescent magnetic particle testing.

SECTION 4.0GENERAL DAMAGE MECHANISMS – ALL INDUSTRIES 一般损伤机制 - 所有行业

4.1 General 大纲4.2 Mechanical and Metallurgical Failure Mechanisms. 机械和冶金失效机制4.3 Uniform or Localized Loss of Thickness. 均衡或局部厚度亏损4.4 High Temperature Corrosion [400°F (204°C)]. 高温腐蚀4.5 Environment Assisted Cracking. 环境辅助开裂

GENERAL DAMAGE MECHANISMS – ALL INDUSTRIES 一般损伤机制 - 所有行业

GENERAL DAMAGE MECHANISMS– ALL INDUSTRIES一般损伤机制 - 所有行业


美国德克萨斯化肥厂爆炸,死亡人数攀升至35人


http://edition.cnn.com/2013/04/18/us/texas-explosion/

http://edition.cnn.com/2013/04/18/us/texas-explosion/

GENERAL DAMAGE MECHANISMS – ALL INDUSTRIES 一般损伤机制 - 所有行业.

API 571 人为的把损伤机理分类为4种作为学习;1. 机械和冶金失效机理,2. 均衡或局部厚度亏损.3. 高温腐蚀,4. 环境辅助开裂

4.2 Mechanical & Metallurgical Failure Mechanisms机械和冶金失效机理

4.3 Uniform or Localized Loss of Thickness均衡或局部厚度亏损

4.4 High Temperature Corrosion高温腐蚀

4.5 Environment Assisted Cracking 环境辅助开裂

4.2 Mechanical & Metallurgical Failure Mechanisms机械和冶金失效机制

4.2 Mechanical and Metallurgical Failure Mechanisms4.2.1 Graphitization.4.2.2 Softening (Spheroidization).4.2.3 Temper Embrittlement.4.2.4 Strain Aging.4.2.5 885°F (475°C) Embrittlement.4.2.6 Sigma Phase Embrittlement .4.2.7 Brittle Fracture.4.2.8 Creep and Stress Rupture.4.2.9 Thermal Fatigue .4.2.10 Short Term Overheating – Stress Rupture.4.2.11 Steam Blanketing.4.2.12 Dissimilar Metal Weld (DMW) Cracking.4.2.13 Thermal Shock.4.2.14 Erosion/Erosion – Corrosion.4.2.15 Cavitation.4.2.16 Mechanical Fatigue.4.2.17 Vibration-Induced Fatigue.4.2.18 Refractory Degradation.4.2.19 Reheat Cracking.4.2.20 GOX-Enhanced Ignition & Combustion

Par. 3. - Definitions 4.2.3 – Temper Embrittlement 4.2.7 – Brittle Fracture 4.2.9 – Thermal Fatigue 4.2.14 – Erosion/Erosion-Corrosion 4.2.16 – Mechanical Failure 4.3.2 – Atmospheric Corrosion 4.3.3 – Corrosion Under Insulation (CUI) 4.3.4 – Cooling Water Corrosion 4.3.5 – Boiler Water Condensate Corrosion 4.3.10 – Caustic Corrosion 4.4.2 – Sulfidation 4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC) 4.5.2 – Corrosion Fatigue 4.5.3 – Caustic Stress Corrosion Cracking 5.1.2.3 – Wet H2S Damage (Blister/HIC/SOHIC/SCC) 5.1.3.1 – High Temperature Hydrogen Attack (HTHA)

Par. 3 – Definitions 4.2.7 – Brittle Fracture 4.2.9 – Thermal Fatigue 4.2.14 – Erosion/Erosion Corrosion 4.2.16 – Mechanical Fatigue 4.2.17 – Vibration-Induced Fatigue 4.3.1 – Galvanic Corrosion 4.3.2 – Atmospheric Corrosion 4.3.3 – Corrosion Under Insulation (CUI) 4.3.5 – Boiler Water Condensate Corrosion 4.3.7 – Flue Gas Dew Point Corrosion 4.3.8 – Microbiological Induced Corrosion (MIC) 4.3.9 – Soil Corrosion 4.4.2 – Sulfidation 4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC) 4.5.3 – Caustic Stress corrosion Cracking 5.1.3.1 – High Temperature Hydrogen Attack (HTTA)

2013-API510 Examination2013- API570 Examination


600 °F~ 1000 °F885°F embrittlement

510

Exam Affected materialsTemperaturesDamage Mechanism

Ferritic, austenitic & duplex SS.Sigma forms most rapidly from the ferrite phase that exists in 300 Series SS and duplex SS weld deposits. It can also form in the 300 Series SS base metal (austenite phase) but usually more slowly.

1000 °F~ 1700 °FSigma-Phase Embrittlement

Pre-1980’s C-steels with a large grain size and C- ½ Mo

Intermediate temperatureStrain Aging


650 °F~ 1070 °FTempered Embrittlement

Low alloy steel up to 9% Cr850 °F ~ 1400 °FSpheroidisation

Plain carbon steelC, C ½ Mo

800°F~1100°F for C Steel875°F for C ½ Mo Steel

Graphitisation

All metals and alloys.Cold liquid impinge on hot surface

Thermal Shock

510/570

510/570


Carbon steel / 300 SS junction

Operating temperatureDissimilar Metal Weld (DMW) Cracking

Carbon steel and low alloy steels

>1000 °FSteam Blanketing

All fired heater tube materials and common materials of construction

>1000 °FShort Term Overheating – Stress Rupture

All materials of constructionOperating temperatureThermal fatigues

All metals and alloys700 °F ~ 1000 °FCreep & stress rupture


AllService temperatureVibration-Induced Fatigue

570

AllService temperatureMechanical fatigue570/510

AllService temperatureCavitation

AllService temperatureErosion/Erosion Corrosion

570/510

AllService temperatureRefractory Degradation

CS, 300SS, Ni BasedService temperatureReheat Cracking

AllService temperatureGOX enhances combustion


4.2.1 Graphitization石墨化(不是API510/570考试项)

Prolong Exposure800°F ~ 1100°F for C Steel>875°F for C ½ Mo Steel

4.2.1 Graphitization 石墨化4.2.1.1 Description of Damage

a) Graphitization is a change in the microstructure of certain carbon steels and 0.5Mo steels after long-term operation in the 800°F to 1100°F (427°C to 593°C) range that may cause a loss in strength, ductility, and/or creep resistance.在800°F 1100°F长期运行后

b) At elevated temperatures, the carbide phases in these steels are unstable and may decompose into graphite nodules. This decomposition is known as graphitization.碳钢/C - ½ Mo钢, 在长期受到高温度影响，钢中碳化物相变得不稳定, 从而分解成石墨结节

4.2.1.2 Affected Materials

Some grades of carbon steel and 0.5Mo steels. (普通碳钢/0.5钼钢)

碳钢/C - ½ Mo钢, 在长期受到高温度影响，钢中碳化物相变得不稳定, 从而分解成石墨结节

Graphitization Location:Areas with tubes containing carbon steel and C-Mo. Most likely in the weld heat-affected zones and high residual stress areas. 易受影响区: 碳钢或 C- ½ Mo 普通碳钢, 焊接热影响区和高残余应力区

Probable cause:Prolonged exposure to above 800°F (425°C) for carbon steels and greater than 875°F (470°C) for the carbon- ½ molybdenum alloys. In graphitized boiler components, the nucleation of graphite likely starts by the precipitation of “carbon” from super-saturated ferrite, an aging phenomenon. This nucleation is enhanced by strain, in effect a strain aging. The preferential formation of graphite within the heat-affected zone is dependent on the balance of the structure being nearly strain free. Thus the “more unstable” heat-affected zone microstructure will decompose into ferrite and graphite before the annealed ferrite and pearlite of the normalized structure will. If the base metal is cold-worked, the annealing of the weld will slow the nucleation of graphite, and the strained tube will graphitize before the heat-affected zone.

在长时间的高温影响下,蝶状珠光体(碳化铁)首先转化为粒状珠光体,然后碳从超饱和的碳化铁析出,晶核形成石墨与周边缺碳纯铁素体.

4.2.1.3 Critical Factors

a) The most important factors that affect graphitization are the chemistry, stress, temperature, and time of exposure.

b) In general, graphitization is not commonly observed. Some steels are much more susceptible to graphitization than others, but exactly what causes some steels to graphitize while others are resistant is not well understood. It was originally thought that silicon and aluminum content played a major role but it has been shown that they have negligible influence on graphitization.

c) Graphitization has been found in low alloy C-Mo steels with up to 1% Mo. The addition of about 0.7% chromium has been found to eliminate graphitization.

d) Temperature has an important effect on the rate of graphitization. Below 800°F (427°C), the rate is extremely slow. The rate increases with increasing temperature.

e) There are two general types of graphitization. First is random graphitization in which the graphite nodules are distributed randomly throughout the steel. While this type of graphitization may lower the room-temperature tensile strength, it does not usually lower the creep resistance.

f) The second and more damaging type of graphitization results in chains or local planes of concentrated graphite nodules.

• Weld heat-affected zone graphitization is most frequently found in the heat-affected zone adjacent to welds in a narrow band, is called “eyebrow,” graphitization.

• Non-weld graphitization is a form of localized graphitization that sometimes occurs along planes of localized yielding in steel. It also occurs in a chain-like manner in regions that have experienced significant plastic deformation as a result of cold working operations or bending.

Weld heat affected zone graphitization

is most frequently found in the heat-affected zone adjacent to welds in a narrow band, corresponding to the low temperature edge of the heat affected zone. In multi-pass welded butt joints, these zones overlap each other, covering the entire cross-section. Graphite nodules can form at the low temperature edge of these heat affected zones, resulting in a band of weak graphite extending across the section. Because of its appearance, this graphite formation within heat affected zones is called “eyebrow” graphitization.

Type 2: HAZ graphite nodules

eyebrow! Type2 Graphitization 焊缝热影响区石墨化现象

eyebrow! Graphitization

太厉害了,别人的肖像变成他家的版权了..NMD

eyebrow! Type 2 Graphitization焊缝热影响区现象

Non-weld graphitization is a form of localized graphitization that sometimes occurs along planes of localized yielding in steel. It also occurs in a chain-like manner in regions that have experienced significant plastic deformation as a result of cold working operations or bending. 显著地塑性变形区域, 石墨化可能以链状方式形成.

Type 2: Non Weld Chains or local planes of concentrated graphite nodules

4.2.1.4 Affected Units or Equipment

a) Primarily hot-wall piping and equipment in the FCC, catalytic reforming and coker units.

b) Bainitic grades are less susceptible than coarse pearlitic grades.c) Few failures directly attributable to graphitization have been reported in the

refining industry. However, graphitization has been found where failure resulted primarily from other causes.

d) Several serious cases of graphitization have occurred in the reactors and piping of fluid catalytic cracking units, as well as with carbon steel furnace tubes in a thermal cracking unit and the failure of seal welds at the bottom tube sheet of a vertical waste heat boiler in a fluid catalytic cracker. A graphitization failure was reported in the long seam weld of a C 0.5Mo catalytic reformer reactor/inter-heater line.

e) Where concentrated eyebrow graphitization occurs along heat-affected zones, the creep rupture strength may be drastically lowered. Slight to moderate amounts of graphite along the heat-affected zones do not appear to significantly lower room or high-temperature properties.

f) Graphitization seldom occurs on boiling surface tubing but did occur in low alloy C-0.5Mo tubes and headers during the 1940’s. Economizer tubing, steam piping and other equipment that operates in the range of temperatures of 850°F to 1025°F (441°C to 552°C) is more likely to suffer graphitization.

4.2.1.5 Appearance or Morphology of Damage

1. Damage due to graphitization is not visible or readily apparent and can only be observed by metallographic examination (Figure 4-1 and Figure 4-2).

2. Advanced stages of damage related to loss in creep strength may include micro-fissuring / microvoid formation, subsurface cracking or surface connected cracking.

0.5μm

Figure 4-1 – High magnification photomicrograph of metallographic sample showing graphite nodules. Compare to normal microstructure shown in Figure 4-2.

Figure 4-2 – High magnification photomicrograph of metallographic sample showing typical ferrite-pearlite structure of carbon steel.

4.2.1.6 Prevention / Mitigation 预防/缓解

Graphitization can be prevented by using chromium containing low alloy steels for long-term operation above 800°F (427°C).

The addition of about 0.7% chromium has been found to eliminate graphitization.

0.7% chromium以消除石墨化.

4.2.1.7 Inspection and Monitoring

a) Evidence of graphitization is most effectively evaluated through removal of full thickness samples for examination using metallographic techniques. Damage may occur mid-wall so that field replicas may be inadequate.

b) Advanced stages of damage related to loss in strength include surface breaking cracks or creep deformation that may be difficult to detect.

4.2.1.8 Related Mechanisms

Spheroidization (see 4.2.2) and graphitization are competing mechanisms that occur at overlapping temperature ranges. Spheroidization tends to occur preferentially above 1025°F (551°C), while graphitization predominates below this temperature.

Spheroidization (see 4.2.2) and graphitization are competing mechanisms that occur at overlapping temperature ranges. Spheroidization tends to occur preferentially above 1025°F (551°C), while graphitization predominates below this temperature.

Graphitization can be prevented by using chromium containing low alloy steels for long-term operation above 800°F (427°C).

Affected Materials: Some grades of carbon steel and 0.5Mo steels. Graphitization has been found in low alloy C-Mo steels with up to 1% Mo. The addition of about 0.7% chromium has been found to eliminate graphitization.

Creep Type: Microvoid formation & jointing of ligament between voids

Typical ferrite-pearlite structure of carbon steel.

Typical martensitic structure of carbon steel.

Figure 13: Lower bainite generated by isothermal transformation of 52100 steel at 230C for 10h

http://www.msm.cam.ac.uk/phase-trans/2011/Bearings/index.htm l

Random graphitization

http://davidnfrench.com/Graphitization.html

Chain graphitization

Graphitization of A Cast Iron Main

>800°F

石墨化,学习重点:

1. 高温现象: 800°F to 1100°F2. 受影响材料: 碳钢(不包括低合金钢), ½ Mo钢3. 损伤模式: (1) 无规则石墨化(仅仅影响室温抗拉)与 (2) HAZ/平面石墨化

(较为严厉,影响室温抗拉高温蠕变性能)4. 注意项: ½ Mo钢,抗拒性较强,敏感温度为 875°F高于碳钢 800°F5. 添加 0.7%Cr 有效阻止石墨化. 6. 不是API 510/570考试学习项.

http://www.chasealloys.co.uk/steel/alloying-elements-in-steel/#chromium

4.2.2 Carbide Spheroidization碳化物球化(不是API510/570考试项)

SpheroidizationProlong Exposure850°F ~ 1400°F

4.2.2 Softening (Spheroidization) 碳化物球化

4.2.2.1 Description of DamageSpheroidization is a change in the microstructure of steels after exposure in the 850°F to 1400°F (440°C to 760°C) range, where the carbide phases 碳化物 in carbon steels are unstable and may agglomerate from their normal plate-like form to a spheroidal form, or from small, finely dispersed carbides in low alloy steels like 1Cr-0.5Mo to large agglomerated carbides. Spheroidization may cause a loss in strength and/or creep resistance.

4.2.2.2 Affected MaterialsAll commonly used grades of carbon steel and low alloy steels including C-0.5Mo, 1Cr-0.5Mo,1.25Cr-0.5Mo, 2.25Cr-1Mo, 3Cr -1Mo, 5Cr-0.5Mo, and 9Cr-1Mo steels.

高温现象: 在长期高温下,细分散或板状碳化物形成球状形式.涵盖了普通碳钢, 0.5Mo钢, 低合金钢,

Figure 9: The microstructures near the OD surface were mostly decarburized. The remaining carbides were highly spheroidized and agglomerated along the ferrite grain boundaries. The microstructure 90° from the rupture and at the tube end is shown.(Nital etch, Mag. 500X)

Figure 10: The microstructures near the ID surface consisted of partially and highly spheroidized and agglomerated carbides along the ferrite grain boundaries. The microstructure 90° from the rupture and at the tube end is shown. (Nital etch, Mag. 500X)

http://www.met-tech.com/short-term-overheat-rupture-of-t11-superheater-tube.html

Differences

Softening (Spheroidization), at prolong exposure to high temperature carbide phases in carbon steels are unstable and may agglomeratefrom their normal plate-like form to a spheroidal form, or from small, finely dispersed carbides in low alloy steels like 1Cr-0.5Mo to large agglomerated carbides. 在长期高温工作下,低合金碳钢,碳化物相变得不稳定, 导致正常板状形式凝聚成一个球状形式.

Graphitisation, the carbide phases in carbon/Molydenum steels are unstable and may decompose into graphite nodules.在高温长期工作下,普通碳钢/0.5钼钢中的化物相变得不稳定,这碳化物分解成石墨结节.

影响的材料差别为;

(1) 普通碳钢/受石墨化影响(2) 低合金含铬钼高强度,高温钢受碳化物球化

Spheroidization 球化in physical metallurgy, a process consisting in the transition of excess-phase crystals into a globular (spheroidal) form. The transition occurs at relatively high temperatures and is associated with a decrease in the interfacial energy高温下界面的能量减少. Of particular importance is the spheroidization of the cementite plates contained in pearlite. In this process, the lamellar pearlite is converted into granular pearlite片状珠光体转变为粒状珠光体. As a result, the hardness and the strength of the metal are significantly decreased, but the ductility is increased.

Carbide Spheroidization 碳化物球化

Figure 2. Etched sample of a section of non-corroded material (200X Original Magnification with Nital Etch)

Figure 1. Corroded sheath exterior (0.85X Original Magnification)

http://www.matter.org.uk/steelmatter/forming/4_5.html

Graphitisation and spheroidization both were high temperature phenomenon.石墨化与球化都是材料高温效应

Graphitisation affect normal carbon steel. It is a break down of carbides into ferrite and free graphite (carbon) nodules.石墨化是高温下,碳化物分解为铁素体和游离石墨/碳.

Spheroidization affect Cr-Mo low carbon steel up to 9%Cr. It is a agglomeration of carbides forming spheroidal carbides. 球化是高温下,界面

的能量减少导致片状珠光体转变为粒状珠光体

Spheroidization affect Cr-Mo low carbon steel up to 9% Cr. It is a agglomeration of carbides forming spheroidal carbides 影响达 9%Cr 低合金碳钢,高温下界面的能量减少,片状珠光体转变为粒状珠光体 (片状碳化物集聚形成球状碳化物).

含9% Chromium 碳化物球化影响范围.

Residual stress & cold works accelerated graphitization.残余应力和冷工程加速石墨化.

For spheroidisation coarse-grained steels are more resistant than fine-grained. Fine grained silicon-killed steels are more resistant than aluminum killed.

粗粒度的钢比细粒度更抗拒碳化物球化.

细晶硅镇静钢比铝镇静更抗拒碳化物球化.

Susceptibility to Spheroidization 球化易感性

• Annealed steels 退火钢材 are more resistant to spheroidization than normalized steels.

• Coarse-grained steels 粗粒度钢材 are more resistant than fine-grained.

• Fine grained silicon-killed steels are more resistant than aluminum-killed.

• The loss in strength 强度损失 may be as high as about 30% but failure is not likely to occur except under very high applied stresses.

Plain carbon steel

C, C ½ Mo

800°F~1100°F for C Steel

875°F for C ½ Mo Steel

GraphitisationNO

Low alloy steel up to 9% Cr.850°F ~ 1400°FSpheroidisationNO

Some grades of carbon steel and 0.5Mo steels.

Exam Affected materialsTemperaturesDM

All commonly used grades of carbon steel and low alloy steels including C-0.5Mo, 1Cr-0.5Mo,1.25Cr-0.5Mo, 2.25Cr-1Mo, 3Cr-1Mo, 5Cr-0.5Mo, and 9Cr-1Mo steels.

Spheroidization (see 4.2.2) and graphitization are competing mechanisms that occur at overlapping temperature ranges. Spheroidization tends to occur preferentially above 1025°F (551°C), while graphitization predominates below this temperature.Discussion: Graphitization occurs on some carbon steel and 0.5Mo steels only.

Spheroidization is a change in the microstructure of steels after exposure in the 850°F to 1400°F (440°C to 760°C) range, where the carbide phases in carbon steels are unstable and may agglomerate from their normal plate-like form to a spheroidal form.

碳化物球化学习重点:1. 高温现象 – 850°F to 1400°F,2. 原理: 低合金碳钢,高温下界面的能量减少,片状珠光体转变为粒状珠光

体 (片状碳化物集聚形成球状碳化物),3. 受影响材质:涵盖了普通碳钢, 0.5Mo钢,低合金钢至 9Cr1Mo钢,4. 粗粒度的钢比细粒度更抗拒碳化物球化,5. 细晶硅镇静钢比铝镇静更抗拒碳化物球化,6. 不同于石墨化,碳化物还是碳化物只不过高温下聚集成为球状,7. 非API 510/570考试题非API 510/570考试题

4.2.3 Temper Embrittlement回火脆化

API510-Exam

650oF~ 1070oF

API510-Exam


650°F~ 1070°FTempered Embrittlement回火脆化

0.5Mo Steel, Low alloy steel up to 9 % Cr

850°F ~ 1400°FSpheroidization碳化物球化

Plain carbon steel / 0.5Mo Steel

800°F~1100°F for C Steel875°F for C ½ Mo Steel

Graphitization石墨化

API510-Exam

4.2.3 Temper Embrittlement 回火脆化4.2.3.1 Description of Damage

Temper embrittlement is the reduction in toughness due to a metallurgical change that can occur in some low alloy steels as a result of long term exposure in the temperature range of about 650°F to 1100°F (343°C to 593°C) . This change causes an upward shift in the ductile-to-brittle transition temperature as measured by Charpy impact testing. Although the loss of toughness is not evident at operating temperature, equipment that is temper embrittled may be susceptible to brittle fracture during start-up and shutdown.

2¼ Cr-1Mo ~ 3Cr-1Mo量低合金钢在650°F to 1100°F工作下,导致受影响材质,

韧脆转变温度向上移位. 工作状态下,设备不会受到此损伤机理任何影响,但在关机,重启时的低温下,材料会因回火脆性的损伤机理导致产生设备受压母材脆裂.

API510-Exam

Temper embrittlement is the reduction in toughness due to a metallurgical change that can occur in some low alloy steels as a result of long term exposure in the temperature range of about 650°F to 1100°F (343°C to 593°C) . 2¼ Cr-1Mo~ 3Cr-1Mo钢材在650°F to 1100°F 工作下,导致受影响材质,韧脆转变温度向上移位.

API510-Exam


a) Primarily 2 ¼ Cr-1Mo (P5A) low alloy steel, 3Cr-1Mo (P5A) (to a lesser extent), and the high-strength low alloy Cr-Mo-V (P5C) rotor steels.

b) Older generation 2 ¼ Cr-1Mo materials manufactured prior to 1972 may be particularly susceptible. Some high strength low alloy steels are also susceptible.

c) The C- ½ Mo (P3) and 1 ¼ Cr- ½ Mo (P4) alloy steels are not significantly affected by temper embrittlement. However, other high temperature damage mechanisms promote metallurgical changes that can alter the toughness or high temperature ductility of these materials.

主要是对 2¼ Cr-1Mo~ 3Cr-1Mo低合金钢, Cr-Mo-V轴钢受影响.

API510-Exam

3Cr-1Mo (to a lesser extent) The C-0.5Mo, 1Cr-

0.5Mo and 1.25Cr-0.5Mo alloy steels are not significantly affected.

Primarily 2.25Cr-1Mo low alloy steel. and the high-strength low alloy Cr-Mo-V rotor steels.

Temper Embrittlement 回火脆性易感性

API510-Exam

API510-Exam

[Embrittlement temperature 650°F~1070°F]

韧脆转变温度

API510-Exam

韧脆转变温度向上移位

API510-Exam

API510-Exam

脆性转变温度向上移位.另个特征是回火脆化,不会对脆性转变点上搁架冲击功有任何影响.

SEM fractographs of tempered embrittled material show primarily intergranular cracking due to impurity segregation at grain boundaries 材料的回火脆化,主要

是由于晶界杂质偏聚导致是沿晶开裂

API510-Exam

http://www.twi.co.uk/news-events/bulletin/archive/1999/january-february/welding-and-fabrication-of-high-temperature-components-for-advanced-power-plant-part-1/

API510-Exam

4.2.3.3 Critical Factors 关键因素

a) Alloy steel composition, thermal history, metal temperature and exposure time are critical factors. 受热历史,金属温度和受感时间是关键因素

b) Susceptibility to temper embrittlement is largely determined by the presence of the alloying elements manganese and silicon, and the tramp elements phosphorus, tin, antimony, and arsenic. The strength level and heat treatment/fabrication history should also be considered. 回火脆化敏感性很大程度上决定于锰/硅与杂元素(磷/锡/锑和砷)含量.

c) Temper embrittlement of 2.25Cr-1Mo steels develops more quickly at 900°F (482°C) than in the 800°F to 850°F (427°C to 440°C) range, but the damage is more severe after long-term exposure at 850°F (440°C). 高温下易感性较大,但在低温下伤害较为严重.

API510-Exam

d) Some embrittlement can occur during fabrication heat treatments, but most of the damage occurs over many years of service in the embrittling temperature range. 有的损伤是因建造热处理引发,但一般上大多数受感于长期在敏感温度下操作引发的.

e) This form of damage will significantly reduce the structural integrity of a component containing a crack-like flaw. An evaluation of the materials toughness may be required depending on the flaw type, the severity of the environment, and the operating conditions, particularly in hydrogen service. 含裂纹状缺陷的部件会减弱结构完整性. 特别是氢服务设备,应在考虑缺陷的类型, 处理工艺的严峻性与操作条件,进行材料的韧性评估.

API510-Exam


a) Temper embrittlement occurs in a variety of process units after long term exposure to temperatures above 650°F (343°C). It should be noted that there have been very few industry failures related directly to temper embrittlement.

b) Equipment susceptible to temper embrittlement is most often found in hydroprocessing units, particularly reactors, hot feed/effluent exchanger components, and hot HP separators. Other units with the potential for temper embrittlement include catalytic reforming units (reactors and exchangers), FCC reactors, coker and visbreaking units.

c) Welds in these alloys are often more susceptible than the base metal and should be evaluated.

受影响的设备主要是用于高温处理单元,例如加氢装置,催化重整装置,催化裂化反应器,炼焦器,减粘裂化单元,等. 焊接部位受感性比母材强,这位应当作为评估考虑部位.

API510-Exam

API510-Exam

http://www.twi-global.com/technical-knowledge/job-knowledge/defects-

imperfections-in-welds-reheat-cracking-048/

http://en.wikipedia.org/wiki/Welding_defect

API510-Exam


a) Temper embrittlement is a metallurgical change that is not readily apparent and can be confirmed through impact testing. Damage due to temper embrittlement may result in catastrophic brittle fracture. 外观变化不明显,需要通过冲击试验证实.

b) Temper embrittlement can be identified by an upward shift in the ductile-to-brittle transition temperature measured in a Charpy V-notch impact test, as compared to the non-embrittled or de-embrittled material (Figure 4-5). Another important characteristic of temper embrittlement is that there is no effect on the upper shelf energy.夏比V型缺口冲击试验证实韧性- 脆性转变温度向上移位.另个特征是回火脆化,不会对脆性转变点上搁架冲击功有任何影响.

c) SEM fractographs of severely temper embrittled material show primarily intergranular cracking due to impurity segregation at grain boundaries.主要为晶间开裂

API510-Exam

API510-Exam

Intergranular CrackingAPI510-Exam

Intergranular Cracking

API510-Exam

Cr5C2/ Cr3C2 precipitated

Low Cr grain boundary

Progressive crack

Metal surface

Crack initiation & growth

API510-Exam

Tensile stress

Grain boundary decohesion-Crack initiation pt.

Cr depleted grain boundaryPPT as Cr5C2/Cr3C2

Embrittlement Mechanism

Grain Boundary

4.2.3.6 Prevention / Mitigation

a) Existing Materials

1. Temper embrittlement cannot be prevented if the material contains critical levels of the embrittling impurity elements and is exposed in the embrittling temperature range.

2. To minimize the possibility of brittle fracture during startup and shutdown, many refiners use a pressurization sequence to limit system pressure to about 25 percent of the maximum design pressure for temperatures below a Minimum Pressurization Temperature (MPT). Note that MPT is not a single point but rather a pressure temperature envelope which defines safe operating conditions to minimize the likelihood of brittle fracture.

API510-Exam

3. MPT’s generally range from 350°F (171°C) for the earliest, most highly temper embrittled steels, down to 125°F (52°C) or lower for newer, temper embrittlement resistant steels (as required to also minimize effects of hydrogen embrittlement).

4. If weld repairs are required, the effects of temper embrittlement can be temporarily reversed (de-embrittled) by heating at 1150°F (620°C)[compared: embrittlement temperature 650°F~1070°F] for two hours per inch of thickness, and rapidly cooling to room temperature. It is important to note that re-embrittlement will occur over time if the material is re-exposed to the embrittling temperature range.

API510-Exam

API510-Exam

Heating at 1150°F (620°C) [compared: embrittlement temperature 650°F~1070°F (343°C to 593°C) ] for two hours per inch of thickness, and rapidly cooling to room temperature.

Existing Material: De-embrittlement treatment.

b) New Materials

The best way to minimize the likelihood and extent of temper embrittlement is to limit the acceptance levels of manganese, silicon, phosphorus, tin, antimony, and arsenic in the base metal and welding consumables. In addition, strength levels and PWHT procedures should be specified and carefully controlled. 最好的缓解方法是控制母材/焊材的锰,硅,磷,锡,锑,砷的成分.

Acceptance Level of Mn, Si, P, Sn, Sb, As.

API510-Exam

Susceptibility to temper embrittlement

A common way to minimize temper embrittlement is to limit the "J*" Factor for base metal and the "X" Factor for weld metal, based on material composition as follows:

J* = (Si + Mn) x (P + Sn) x 104 {elements in wt%}X = (10P + 5Sb + 4Sn + As)/100 {elements in ppm}

API510-Exam

Typical J* and X factors used for 2.25 Cr steel are a maximum of 100 and 15, respectively. Studies have also shown that limiting the (P + Sn) to less than 0.01% is sufficient to minimize temper embrittlement because (Si + Mn) control the rate of embrittlement.

J* : 100 Max. (Base metal)X : 15 Max. (Weld metal)

API510-Exam

API510-Exam


a) a) A common method of monitoring is to install blocks of original heats of the alloy steel material inside the reactor. Samples are periodically removed from these blocks for impact testing to monitor/establish the ductile-brittle transition temperature. The test blocks should be strategically located near the top and bottom of the reactor to make sure that the test material is exposed to both inlet and outlet conditions.

b) Process conditions should be monitored to ensure that a proper pressurization sequence is followed to help prevent brittle fracture due to temper embrittlement.


Not applicable.

API510-Exam

Figure 4-5 – Plot of CVN toughness as a function of temperature showing a shift in the 40-ft-lb transition temperature.

API510-Exam

Temper embrittlement is inherent in many steels and can be characterized by reduced impact toughness. The state of temper embrittlement has practically no effect on other mechanical properties at room temperature. Figure 1 shows schematically the effect of temperature on impact toughness of alloy steel which is strongly liable to temper embrittlement. Many alloy steels have two temperature intervals of temper embrittlement. For instance, irreversible temper brittleness may appear within the interval of 250-400°C and reversible temper brittleness, within 450°C-650°C.http://www.keytometals.com/Articles/Art102.htm

API510-Exam

API510-Exam

irreversible temper brittleness may appear within the interval of 250-400°C

reversible temper brittleness, within 450°C-650°C.

Metallurgy of Mo in alloy steel & ironTemper embrittlement may occur when steels are slowly cooled after tempering through the temperature range between 450 and 550°C. This is due to the segregation of impurities such as phosphorus, arsenic, antimony and tin on the grain boundaries. The molybdenum atom is very large relative to other alloying elements and impurities. It effectively impedes the migration of those elements and thereby provides resistance to temper embrittlement.http://www.imoa.info/molybdenum_uses/moly_grade_alloy_steels_irons/tempering.php

API510-Exam

Other/ 其他阅读

Other reference: http://www.twi.co.uk/technical-knowledge/faqs/material-faqs/faq-what-is-temper-embrittlement-and-how-can-it-be-controlled/

回火脆化学习重点:1. 高温现象: 650°F to 1100°F,2. 原理: 材料的回火脆化,主要是由于晶界杂质偏聚导致是沿晶开裂3. 受影响材质:, 2.25Cr1Mo ~ 3Cr1Mo低合金钢与轴钢,不涵盖普通碳钢,4. 最好的缓解方法是控制母材/焊材的锰,硅,磷,锡,锑,砷的成分,5. 其他缓解方法: 控制材料强度(?)与热处理受感温度,6. 这种脆化现象不能在高于受感温度热处理逆转恢复.7. 除了低温冲击功,不影响其他高低温机械性能.

Valentino

高亮

4.2.4 Strain Aging时效伸张(不是API510/570考试项)

Intermediatetemperature


600°F~ 1000°F885oF embrittlement

pre-1980’s carbon steels with a large grain size and C-0.5 Mo



650°F~ 1070°FTempered Embrittlement

Plain carbon + Low alloy steel up to 9% Cr

850oF ~ 1400oFSpheroidization

Plain carbon steel800°F for C Steel875°F for C ½ Mo Steel

Graphitisation

受影响的材质是那些老工艺的炼钢方法的普通碳钢与0.5Mo钢 – 含有高成分的关键杂质元素与粗晶粒.

4.2.4 Strain Aging 伸张时效

4.2.4.1 Description of DamageStrain aging is a form of damage found mostly in older vintage carbon steels and C-0.5 Mo low alloy steels under the combined effects of deformation and aging at an intermediate temperature. This results in an increase in hardness and strength with a reduction in ductility and toughness.

4.2.4.2 Affected MaterialsMostly older (pre-1980’s) carbon steels with a large grain size and C-0.5 Mo low alloy steel.

When susceptible materials are plastically deformed and exposed to intermediate temperatures, the zone of deformed material may become hardened and less ductile.

一般上受影响的是1980年或更早前的碳钢(特别是大粒径 / C- ½ Mo), 当这些敏感的材料, 经过塑性变形和接触中间温度作业时，这变形材料区可能变硬和延展性与韧性降低。

http://link.springer.com/article/10.1007%2Fs11668-006-5014-3#page-1http://link.springer.com/article/10.1007%2FBF02715166#page-1http://matperso.mines-paristech.fr/Donnees/data03/386-belotteau09.pdf

Most of the effects of cold work on the strength and ductility of structural steels can be eliminated by thermal treatment, such as stress relieving, normalizing, or annealing. However, such treatment is not often necessary.伸张时效对强度和韧性的影响能以热处理逆转恢复.

韧性减低/抗拉曾强

AISC- Guide to Design Criteria for Bolted and Riveted Joints

拉力

4.2.4.3 Critical Factors关键因素

a) Steel composition and manufacturing process determine steel susceptibility.b) Steels manufactured by the Bessemer or open hearth process contain

higher levels of critical impurity elements than newer steels manufactured by the Basic Oxygen Furnace (BOF) process.

c) In general, steels made by BOF and fully killed with aluminum will not be susceptible. The effect is found in rimmed and capped steels with higher levels of nitrogen and carbon, but not in the modern fully killed carbon steels manufactured to a fine grain practice.

受感性强材质: 含有高成分的关键杂质元素的转炉或平炉炼钢法(老炼钢法), 含大量的氢与碳元素的压盖钢/半镇静钢/沸腾钢

不受影响材质:

碱性氧气转炉炼钢法, 铝镇静钢,细晶粒实践钢.

d) Strain aging effects are observed in materials that have been cold worked and placed into service at intermediate temperatures without stress relieving. 冷加工件(无热处理)用于中等温度服务.

e) Strain aging is a major concern for equipment that contains cracks. If susceptible materials are plastically deformed and exposed to intermediate temperatures, the zone of deformed material may become hardened and less ductile. This phenomenon has been associated with several vessels that have failed by brittle fracture. 塑性变材料当接触到中等温度时, 变形的区域会变硬与减少韧性,如这材料带裂缝时会导致设备脆性断裂.

f) The pressurization sequence versus temperature is a critical issue to prevent brittle fracture of susceptible materials.加压顺序与温度是预防时效伸张开裂的关键方法.

g) Strain aging can also occur when welding in the vicinity of cracks and notches in a susceptible material. 焊接加热也会加剧带裂纹的受感材料.

Bessemer Process

Open hearth Process

Open hearth Process 平炉炼钢法

Basic Oxygen Process碱性氧气转炉炼钢法

Basic Oxygen Process

http://metallurgyfordummies.com/steelmaking-technology/

Metallurgy for Dummies

Capped Steel半镇静钢,加盖钢:

It has characteristics similar to those of rimmed steels but to a degree intermediate between those of rimmed and semi-killed steels.

A deoxidizer may be added to effect a controlled running action when the steel is cast. the gas entrapped during solidification is in excess of that needed to counteract normal shrinkage, resulting in a tendency for the steel to rise in the mould.

The capping operation caused the steel to solidify faster, thereby limiting the time of gas evolution, and prevents the formation of an excessive number of gas voids within the ingot.

Capped steel is generally cast in bottle-top moulds using a heavy metal cap.

Capped steel may also be cast in open-top moulds, by adding aluminum or ferro-silicon on the top of molten steel, to cause the steel on the surface to lie quietly and solidify rapidly.

4) Rimmed Steel 沸腾钢,不脱氧钢:

In rimmed steel, the aim is to produce a clean surface low in carbon content. Rimmed steel is also known as drawing quality steel.

The typical structure results for a marked gas evolution during solidification of outer rim.

They exhibit greatest difference in chemical composition across sections and from top to bottom of the ingot.

They have an outer rim that is lower in carbon, phosphorus, and sulphurthan the average composition of the whole ingot and an inner portion or core that is higher the average in those elements.

In rimming, the steel is partially deoxidized. Carbon content is less than 0.25% and manganese content is less than 0.6%.

They do not retain any significant percentage of highly oxidizable elements such as Aluminum, silicon or titanium.

A wide variety of steels for deep drawing is made by the rimming process, especially where ease of forming and surface finish are major considerations.

These steel are, therefore ideal for rolling, large number of applications, and is adapted to cold-bending, cold-forming and cold header applications.

应变时效学习重点:

1. 中等温度现象 – ?°F to ?°F,2. 受感材质:含有高成分的关键杂质元素的转炉或平炉炼钢法,未经过热处

理冷加工件.粗晶粒钢.3. 受感设备: 高厚度非热处理受感材质设备.4. 碱性氧气转炉炼钢法,铝镇静钢,细晶粒实践钢不受影响.5. 蓝脆性为别名.6. 非API 510/570考试题非API 510/570考试题

4.2.5 885°F (475°C) embrittlement885°F 脆化-铁素体不锈钢/双相钢(不是API510/570考试项)

885°F (475°C) embrittlement 600°F~ 1000°F

300*, 400 & Duplex SS containing ferrite phases

600°F~ 1000°F885°F embrittlement

pre-1980’s carbon steels with a large grain size and C-0.5 Mo



650°F~ 1070°FTempered Embrittlement

Plain carbon + Low alloy steel up to 9% Cr

850oF ~ 1400oFSpheroidization

Plain carbon steel800°F for C Steel875°F for C ½ Mo Steel

Graphitisation

受影响的材质:含铁素土的不锈钢.* 锻与铸件奥氏体不锈钢.

4.2.5 885°F (475°C) Embrittlement4.2.5.1 Description of Damage

885°F (475°C) embrittlement is a loss in toughness due to a metallurgical change that can occur in stainless steel containing a ferrite phase, as a result of exposure in the temperature range 600°F~1000°F (316°C to 540°C).


a) 400 Series SS- ferritic & martensitic (e.g., 405, 409, 410, 410S, 430, and 446).

b) Duplex stainless steels such as Alloys 2205, 2304, and 2507.c) Wrought and cast 300 Series SS containing ferrite, particularly welds and

weld overlay.

高温现象: 600°F to 1000°F含有铁素体相不锈钢 (铁素体/马氏体/双相/奥氏体-全包含)由于冶金的变化韧性的损失现象.

http://www.keytometals.com/page.aspx?ID=CheckArticle&site=kts&LN=CN&NM=102

885°F (475°C) embrittlement

Embrittlement of stainless steels containing ferrite phase upon extended exposure to temperatures between 730°F and 930°F (400°C and 510°C ). This type of embrittlement is caused by fine, chromium-rich precipitates that segregate at grain boundaries: time at temperature directly influences the amount of segregation. Grain-boundary segregation of the chromium-rich precipitates increases strength and hardness, decreases ductility and toughness, and changes corrosion resistance. This type of embrittlement can be reversed by heating above the precipitation range.

885°F 脆化,这种类型的脆化是由于富含铬的析出物在晶界处偏析出.晶界偏析的富含铬的析出增加强度和硬度,降低塑性和韧性和耐腐蚀变化(减弱).这种脆化现象能在高于析出温度热处理逆转恢复.

Most refining companies limit the use of ferritic stainless steels to non-pressure boundary applications because of this damage mechanism.

885°F embrittlement is a metallurgical change that is not readily apparent with metallography but can be confirmed through bend or impact testing (Figure 4-6).

The existence of 885°F embrittlement can be identified by an increase in hardness in affected areas. Failure during bend testing or impact testing of samples removed from service is the most positive indicator of 885°F embrittlement.

885°F embrittlement is reversible by heat treatment to dissolve precipitates, followed by rapid cooling. The de-embrittling heat treatment temperature is typically 1100°F (593°C) or higher and may not be practical for many equipment items. If the de-embrittled component is exposed to the same service conditions it will re-embrittle faster than it did initially.


a) The alloy composition, particularly chromium content, amount of ferrite phase, and operating temperature are critical factors.铬,铁素体相的数量和操作温度

b) Increasing amounts of ferrite phase increase susceptibility to damage when operating in the high temperature range of concern. A dramatic increase in the ductile-to-brittle transition temperature will occur.越来越多的铁素体相的增加损伤的易感性(韧脆转变温度显著提高)

c) A primary consideration is operating time at temperature within the critical temperature range. Damage is cumulative and results from the precipitation of an embrittling intermetallic phase that occurs most readily at approximately 885°F (475°C). Additional time is required to reach maximum embrittlement at temperatures above or below 885°F (475°C). For example, many thousands of hours may be required to cause embrittlement at 600°F (316°C). 损伤是因在受感温度操作时,金属间项(intermetallic phase)的溢出/沉淀在晶间导致的.

d) Since 885°F embrittlement can occur in a relatively short period of time, it is often assumed that susceptible materials that have been exposed to temperatures in the 700°F to 1000°F (371°C to 538°C) range are affected.受感温度一般上定义为700°F至1000°F 之间

e) The effect on toughness is not pronounced at the operating temperature, but is significant at lower temperatures experienced during plant shutdowns, startups or upsets.对韧性的影响体现在较低于操作温度例如在停机,启动和颠覆状态时.

f) Embrittlement can result from tempering at higher temperatures or by holding within or cooling through the transformation range. 在受感温度回火热处理或当冷却时在受感(转变)温度停留会导致885°F脆化.

Fig. 2—Microstructure of solution-annealed 304LN stainless steel

Fig. 3—Oxalic acid etched microstructures of 304LN stainless steel sensitized for (a) 1 h, (b) 25 h, (c) 50 h, and (d) 100 h.


a) Impact or bend testing of samples removed from service is the most positive indicator of a problem.

b) Most cases of embrittlement are found in the form of cracking during turnarounds, or during startup or shutdown when the material is below about 200°F (93°C) and the effects of embrittlement are most detrimental.

c) An increase in hardness is another method of evaluating 885°F embrittlement.

Impact energy and brinell hardness as function of time exposure qt 475°C475oC Embrittlement in a Duplex Stainless Steel UNS S31803

475oC Embrittlement in a Duplex Stainless Steel UNS S31803http://www.scielo.br/scielo.php?pid=S1516-14392001000400003&script=sci_arttext

http://www.sciencedirect.com/science/article/pii/S0921509309000197

885°F (475°C) Embrittlement of stainless steels in alloys containing a ferrite phase (Ferritic/Martensitic/Duplex stainless steel and ferrite phases in austenitic stainless steel e.g. weld areas) 影响材质: 含铁素

体的不锈钢

Grain-boundary segregation of the chromium-rich precipitates increases strength and hardness, decreases ductility and toughness, and changes corrosion resistance (lower). 含富铬金属间(intermetallic)在晶间溢出导致脆化.

This type of embrittlement can be reversed by heating above the precipitation range.可以通过加热逆转恢复

Impact testing/bend test & hardness testing used to evaluate susceptibility. 冲击试验,弯曲试验,硬度试验作为易感性的评估.

Restrict the used of ferritic steel to non-pressure boundary application. 限制铁素体不锈钢用于非受压用途.

4.2.6 Sigma-Phase Embrittlement“西格玛”相脆化

(不是API510/570考试项)

Sigma-Phase Embrittlement1000oF~1700oF


1000°F~ 1700°FSigma phase embrittlement

300*, 400 & Duplex SS containing ferrite phase

600°F~ 1000°F885°F embrittlement

受影响的材质:含铁素体的不锈钢, * 锻与铸件奥氏体不锈钢

4.2.6 Sigma Phase Embrittlement4.2.6.1 Description of Damage

Formation of a metallurgical phase known as sigma phase can result in a loss of fracture toughness in some stainless steels as a result of high temperature exposure.


a) 300 Series SS wrought metals, weld metal, and castings. Cast 300 Series SS including the HK and HP alloys are especially susceptible to sigma formation because of their high (10-40%) ferrite content.

b) The 400 Series SS and other ferritic and martensitic SS with 17% Cr or more are also susceptible (e.g., Types 430 and 440).

c) Duplex stainless steels.

受影响的材质: 铁素体不锈钢,含铁素体的马氏体,奥氏体不锈钢和双相不锈钢.脆化原因: 在受感温度下,西格玛相形成,在铁素体项析出导致脆化.

http://www.hindawi.com/journals/isrn.metallurgy/2012/732471/


Sigma-Phase Embrittlement 西格玛相脆化

Description: Embrittlement of iron-chromium alloys caused by precipitation at grain boundaries of the hard, brittle intermetallic sigma phase σ during long periods of exposure to temperatures between approximately 565oC and 980oC (1050oF and 1800oF). Sigma phase embrittlement results in severe loss in toughness and ductility and can make the embrittled material structure susceptible to intergranular corrosion.

在长时间暴露在温度约 565oC ~ 980oC (1050oF ~ 1800oF)之间,硬而脆的金

属间化合物(σ相)在铁素体晶界处析出, σ相脆化导致的韧性和延展性严重损失与导致易受晶间腐蚀.


a) Alloy composition, time and temperature are the critical factors. 化学成分, 时间, 温度都是关键因素.

b) In susceptible alloys, the primary factor that affects sigma phase formation is the time of exposure at elevated temperature. 易感材料;时间与经历温度为主要因素.

c) Sigma phase occurs in ferritic (Fe-Cr), martensitic (Fe-Cr), austenitic (Fe-Cr-Ni) and duplex stainless steels when exposed to temperatures in the range of 1000°F to 1700°F (538°C to 927°C). Embrittlement can result by holding within or cooling through the transformation range. 铁素体,马氏体,奥氏体,双相钢,当停留或冷却途径1000°F to 1700°F 温度时,产生σ相析出.

d) Sigma forms most rapidly from the ferrite phase that exists in 300 Series SS and duplex SS weld deposits. It can also form in the 300 Series SS base metal (austenite phase) but usually more slowly. σ相以较快的速度在铁素体相析出,但也会在奥氏体项较慢的速度析出.

e) The 300 Series SS can exhibit about 10% to 15% sigma phase. Castaustenitic stainless steels can develop considerably more sigma.σ 相在奥氏体不锈钢以10%~15%表现出来,铸件可能还高.

f) Formation of sigma phase in austenitic stainless steels can also occur in a few hours, as evidenced by the known tendency for sigma to form if an austenitic stainless steel is subjected to a post weld heat treatment at 1275°F (690°C). σ相在奥氏体的析出只需几个小时,这脆化趋向可以从1275°F焊接热处理后,出现σ相的到证明.

g) The tensile and yield strength of sigmatized stainless steels increases slightly compared with solution annealed material. This increase in strength is accompanied by a reduction in ductility (measured by percent elongation and reduction in area) and a slight increase in hardness.σ相脆化后,抗拉强度.硬度相比固溶退火材料略有增加, 同时,延展性与韧性减少.

http://www.intechopen.com/books/metallurgy-advances-in-materials-and-processes/homogenization-heat-treatment-to-reduce-the-failure-of-heat-resistant-steel-castings

Σ(σ)phase in austenitic matrix

Σ(σ)phase in austenitic matrix

h) Stainless steels with sigma can normally withstand normal operating stresses, but upon cooling to temperatures below about 500°F (260°C) may show a complete lack of fracture toughness as measured in a Charpy impact test. Laboratory tests of embrittled weld metal have shown a complete lack of fracture toughness below 1000°F (538°C)一般上材料在正常操作温度时不受西格玛相脆化影响,但是当材料温度降至500°F材料完全缺乏韧性(实验室导致完全缺乏韧性的温度可能高至1000°F).

i) The metallurgical change is actually the precipitation of a hard, brittle intermetallic compound that can also render the material more susceptible to intergranular corrosion. The precipitation rate increases with increasing chromium and molybdenum content.缺乏韧性是因硬脆性金属间化合物沉淀在晶间.随着铬和钼含量提高,沉淀率相应加速.

Cr% & Mo%铬和钼含量增加

The precipitation rate increases σ 相析出增加

σ相脆化- 缺乏韧性是因硬脆性金属间(intermetallic-sigma phase)化合物沉淀在晶间.随着铬和钼含量提高,沉淀率相应加速.


a) Common examples include stainless steel cyclones, piping ductwork and valves in high temperature FCC (fluidized catalytic cracking )Regenerator service.

b) 300 Series SS weld overlays and tube-to-tubesheets attachment welds can be embrittled during PWHT treatment of the underlying CrMo base metal.

c) Stainless steel heater tubes are susceptible and can be embrittled.

FCC (fluidized catalytic cracking )Regenerator service

http://www.phxequip.com/plant.73/fluid-catalytic-cracker-unit.aspx


Stainless steel heater tubes

tube-to-tubesheets attachment

4.2.6.5 Appearance or Morphology of Damage 损伤外观形态

a) Sigma phase embrittlement is a metallurgical change that is not readily apparent, and can only be confirmed through metallographic examination and impact testing. (Tables 4-1 and 4-2)外观上不能体现损伤,只能依靠金相分析和冲击试验

b) Damage due to sigma phase embrittlement appears in the form of cracking, particularly at welds or in areas of high restraint. σ相脆化一般上以开裂的形态出现特别是在焊缝与高抑制区域.

c) Tests performed on sigmatized 300 Series SS (304H) samples from FCC regenerator internals have shown that even with 10% sigma formation, the Charpy impact toughness was 39 ft-lbs (53 J) at 1200°F (649°C).材料: 304H敏化度: 10%σ相温度/冲击功: 649°C / 53J

设备:催化裂化再生器材料: 304H敏化度: 10%σ相温度/冲击功: 649°C / 53J

新材料的机械性能:SPECIFICATION FOR HEAT-RESISTINGCHROMIUM AND CHROMIUM-NICKEL STAINLESSSTEEL PLATE, SHEET, AND STRIP FORPRESSURE VESSELSASTM SA-240

SPECIFICATION FOR HEAT-RESISTING CHROMIUM AND CHROMIUM-NICKEL STAINLESS STEEL PLATE, SHEET, AND STRIP FOR PRESSURE VESSELS ASTM SA-240

d) For the 10% sigmatized specimen, the values ranged from 0% ductility at room temperature to 100% at 1200°F (649°C). Thus, although the impact toughness is reduced at high temperature, the specimens broke in a 100% ductile fashion, indicating that the wrought material is still suitable at operating temperatures. See Figures 4-7 to 4-11.敏化材料的室温延展性或许降至为零.但在1200°F材料的延展性可能不受任何的影响.

e) Cast austenitic stainless steels typically have high ferrite/sigma content (up to 40%) and may have very poor high temperature ductility.铸造奥氏体不锈钢敏化都可能高至40%的σ相,这导致很差的高温塑性/延展性.

Evaluation of Sigma Phase Embrittlement of a Stainless Steel 304H Fluid Catalyst Cracking Unit Regenerator Cyclone 不锈钢

304H催化裂化再生旋风器σ相脆化评价.Authors: Ali Y. Al-Kawaie and Abdelhak KermadABSTRACTTesting was performed on a 304H stainless steel sample removed from a Fluid Catalyst Cracking Unit (FCCU) regenerator cyclone after 25 years of service to check for sigma phase formation. Sigma phase is a nonmagnetic inter-metallic phase composed mainly of iron and chromium (Fe-Cr), which forms in ferritic and austenitic stainless steels during exposure at the temperature range 1,050 °F to 1,800 °F (560 °C to 980 °C), causing loss of ductility and toughness. Cracking may also occur if the component was impact-loaded or excessively stressed during shutdown or maintenance work. This article discusses the effect of sigma phase embrittlement on the FCCU regenerator cyclone after extended high temperature service.

http://www.saudiaramco.com/content/dam/Publications/Journal%20of%20Technology/Spring2011/Art%2012%20-%20JOT%20Internet.pdf

Table 2. Impact testing (Test Method: ASTM E23)

Table 3. Micro-hardness testing. Test load: 200 g,Calibration Block Hardness: 256 + 10 HV, Measured Hardness of the calibration block: 258 VHN.

Fig. 1. Cyclone sample, as received.

Fig. 2. Micrograph showing carburized layer at the outer (top) surface, 100x (As received).

Fig. 3. Micrograph showing the microstructure at the outer (top) surface, 100x (Heat treaded).

Note: solution annealing at 1,066 °C for four hours, followed by a water quench before testing.

Fig. 4. Micrograph showing sigma formation at the center of the sample. Estimated volume fraction 7%, 100x (As received).

Fig. 5. Micrograph showing the microstructure at the center of the heat treated sample, 100x (Heat treated).


Fig. 6. Micrograph showing sigma phase at the inner (bottom) surface of the original sample, 100x (As received).

Fig. 7. Micrograph showing the microstructure at the inner surface of the heat treated sample, 100x (Heat treated).


Fig. 8a. SEM fractography showing the brittle fracture surface (Top - As received)

Fig. 8b. SEM fractography showing the ductile fracture (Bottom - Heat treated) of the impact tested samples.


a) The best way to prevent sigma phase embrittlement is to use alloys that are resistant to sigma formation or to avoid exposing the material to the embrittling range. 最好的预防方法是不用易敏材料与避免使材料暴露在脆化温度范围作业(这牵涉到设定合适的IOW)

b) The lack of fracture ductility at room temperature indicates that care should be taken to avoid application of high stresses to sigmatized materials during shutdown, as a brittle fracture could result. 室温断裂韧性不足是σ相脆化损伤机理的特点. 这显著地影响设备在启动,关断与瞬态状态的使用; 在设备处于低温状态时避免设备受到高应力(设备随着温度提高增加设备受压).*

c) The 300 Series SS can be de-sigmatized by solution annealing at 1950°F (1066°C) for four hours followed by a water quench. However, this is not practical for most equipment. σ相脆化损伤可以可以通过加热逆转恢复(温度1950°F固溶退火). 然而这往往并不是在役设备实用的修护方案.

Note* 注意设备压力试验时可能导致低温脆裂的危险.

d) Sigma phase in welds can be minimized by controlling ferrite in the range of 5% to 9% for Type 347 and somewhat less ferrite for Type 304. The weld metal ferrite content should be limited to the stated maximum to minimize sigma formation during service or fabrication, and must meet the stated minimum in order to minimize hot short cracking during welding. 奥氏体不锈钢铁素体含量的控制用于减少σ相脆化的形成.

e) For stainless steel weld overlay clad Cr-Mo components, the exposure time to PWHT temperatures should be limited wherever possible.铬钼覆盖层焊后热处理尽量减少暴露时间.

What causes knife-line attack? For stabilized stainless steels and alloys, carbon is bonded with stabilizers (TiC or NbC) and no weld decay occurs in the heat affected zone during welding. In the event of a subsequent heat treatment or welding (above 1200oC), however, first the TiC / NbC may dissociated into free Ti, Nb and C, on cooling precipitation of chromium carbide Cr23C6 is possible and this leaves the narrow band adjacent to the fusion line susceptible to intergranular corrosion.

What causes weld decay? As in the case of intergranular corrosion, grain boundary precipitation, notably chromium carbides in non-stabilized stainless steels, is a well recognized and accepted mechanism of weld decay. In this case, the precipitation of chromium carbides is induced by the welding operation when the heat affected zone (HAZ) experiences a particular temperature range (550oC~850oC). The precipitation of chromium carbides consumed the alloying element - chromium from a narrow band along the grain boundary and this makes the zone anodic to the unaffected grains. The chromium depleted zone becomes the preferential path for corrosion attack or crack propagation if under tensile stress.

Anodic site

4.2.6.7 Inspection and Monitoring 检验与监测

a) Physical testing of samples removed from service is the most positive indicator of a problem. 设备采样机械试验时最好的方法确认损伤机制.

b) Most cases of embrittlement are found in the form of cracking in both wrought and cast (welded) metals during turnarounds, or during startup or shutdown when the material is below about 500°F (260°C) and the effects of embrittlement are most pronounced. σ相脆化开裂失效模式一般出现于设备温度处于低于500°F (260°C) 状态例如当设备周转,启动,关断时.

4.2.6.8 Related Mechanisms 相关机制

Not applicable.不适用

Figure 10: Shaeffler diagram showing the embrittlement region of theσphase [33].http://www.hindawi.com/journals/isrn.metallurgy/2012/732471/

http://www.metalconsult.com/failure-analysis-furnace-tubes.html

http://www.metallograf.de/start-eng.htm?/untersuchungen-eng/sigmaphase/sigmaphase.htm

http://www.industrialheating.com/articles/90371-sigma-phase-embrittlement

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1517-70762009000300017

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1517-70762009000300017

Table 4: Chemical composition of ferrite austenite and sigma phases at 900oC

Polishing markings

Improperly etched specimen showing little or no sign of sigma phase

NaOH etched

Oxalic acid etched-Duplex SS

Sigma-phase embrittlement

高温现象:1000oF~1700oF 影响材质:铁铬合金原理:σ相脆化损伤机理: 是当铁铬合金暴露在高温下, 硬,脆性的σ相金属间

化合物晶界沉淀引起的脆性现象. 解决方法: σ相脆化损伤可以可以通过加热逆转恢复(温度1950°F固溶退火).

然而这往往并不是在役设备实用的修护方案. 非 API 510/570考试项

4.2.7 Brittle Fracture脆性破裂API 510/570考试学习科目

API510/570-Exam

Brittle FractureBelow DTBTTDTBT: Ductile to brittle transition temperature.

API510/570-Exam

No shear lip, little micro void coalescence, little deformation

API510/570-Exam

4.2.7 Brittle Fracture 脆性断裂4.2.7.1 Description of Damage 损伤描述

Brittle fracture is the sudden rapid fracture under stress (residual or applied) where the material exhibits little or no evidence of ductility or plastic deformation. 脆性断裂- 在应力(残余或应用)作用下突然快速断裂.材料表现出很少的延展性, 塑性变形.

4.2.7.2 Affected Materials 受影响材质

Carbon steels and low alloy steels are of prime concern, particularly older steels. 400 Series SS are also susceptible. 受影响的材质有; 碳钢, 低合金钢与铁素体/马氏体不锈钢

Affected Materials Ferritic/Martensitic STEELS 只对铁素体/马氏体钢材影响

API510/570-Exam


a) When the critical combination of three factors is reached, brittle fracture can occur:1. The materials’ fracture toughness (resistance to crack like flaws) as

measured in a Charpy impact test;断裂韧性2. The size, shape and stress concentration effect of a flaw;

应力的形状与大小3. The amount of residual and applied stresses on the flaw.

残余或外加应力

b) Susceptibility to brittle fracture may be increased by the presence of embrittling phases. 晶体脆化相存在会增加脆裂易感性

c) Steel cleanliness and grain size have a significant influence on toughness and resistance to brittle fracture.钢的纯净度和晶粒大小显著地影响材料韧性和断裂抗拒能力.

API510/570-Exam

d) Thicker material sections also have a lower resistance to brittle fracture due to higher constraint which increases triaxial stresses at the crack tip.较厚的材料因更高的应力约束,增加了在裂纹尖端的三轴应力;导致较低的断

裂阻力

d) In most cases, brittle fracture occurs only at temperatures below the Charpy impact transition temperature (or ductile-to-brittle transition temperature), the point at which the toughness of the material drops off sharply. 一般上脆裂发生在低于韧脆转变温度.

API510/570-Exam

Definition of Brittle Fracture 脆性断裂定义

a steel member may experience a brittle fracture. Three basic factors contribute to a brittle-cleavage type of fracture. They are;

• a triaxial state of stress, • a low temperature, and • a high strain rate or rapid rate of loading.

All these factors need not be present. Crack often propagates by cleavage –breaking of atomic bonds along specific crystallographic planes (cleavage planes), propagate rapidly without further increase in applied stress (applied or residual) with little indication of plastic deformation.

In contrast, a ductile fracture occurs mainly by shear, usually preceded by considerable plastic deformation.

API510/570-Exam

API510/570-Exam

API510/570-Exam

Figure 7: The fracture examination using a SEM on C1 and C2 revealed features typical of transgranular fracture (left and middle) and signatures of intergranular cracking (left and right). The presence of both intergranular and transgranular features indicates a mixed-mode fracture morphology.http://www.drillingcontractor.org/tubular-fracturing-pinpointing-the-cause-14544

API510/570-Exam

In Case 2 from Oklahoma, the pin connection twisted off while making up the pin connection of a saver sub.http://www.drillingcontractor.org/tubular-fracturing-pinpointing-the-cause-14544

API510/570-Exam

Figure 4: The fracture on the Case 1 sub showed a grainy texture and “chevron marks” that point toward the initiation site, which is typical morphology for brittle cracking

API510/570-Exam

Figure 5: The fracture on C3 exhibited a small fatigue region that was followed by brittle fracture. The fracture surface had a grainy appearance and presented a minuscule shear lip, which is also typical of a brittle fracture

API510/570-Exam

Various stages during ductile fracture 韧性断裂 are schematically shown in above figure.

(a) Necking, 缩颈(b) Cavity formation (microvoid), 微孔形成(c) Cavity coalescence to form a crack (microvoid coalescence), 微孔的聚结(d) Crack propagation, 裂缝蔓延(e) Fracture (shear fracture). 断裂 (剪切断裂)

API510/570-Exam

API510/570-Exam

Brittle fracture of a shaft caused by a small fatigue crack close to the keyway. The fatigue would be expected to start at the keyway root but actually began at a surface defect.http://www.surescreen.com/scientifics/library-of-failures.php

API510/570-Exam

API510/570-Exam

http://www.wermac.org/misc/pressuretestingfailure2.html

4.2.7.4 Affected Units or Equipment 受影响的单元或设备

a) Equipment manufactured to the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, prior to the December 1987 Addenda, were made with limited restrictions on notch toughness for vessels operating at cold temperatures. However, this does not mean that all vessels fabricated prior to this date will be subject to brittle fracture. Many designers specified supplemental impact tests on equipment that was intended to be in cold service. ASME锅炉和压力容器规范1987年12月前,因为对低温操作设备缺乏材料韧性要求的限制,这些设备可能有脆裂的隐患. 然而虽然不是规范要求,有的设计会因设备低温操作,对材质附加低温冲击要求.

b) Equipment made to the same code after this date were subject to the requirements of UCS 66 (impact exemption curves). 引用ASME VIII DIV1 UCS 66 对材料冲击要求宽松条款的设备.

API510/570-Exam

c) Most processes run at elevated temperature so the main concern is for brittle fracture during startup, shutdown, or hydrotest/tightness testing. Thick wall equipment on any unit should be considered. 在设备因周转,启动,停机时低温状态

d) Brittle fracture can also occur during an auto-refrigeration event in units processing light hydrocarbons such as methane, ethane/ethylene, propane/propylene, or butane. This includes alkylation units, olefin units and polymer plants (polyethylene and polypropylene). Storage bullets/spheres for light hydrocarbons may also be susceptible. 蒸发自动冷却服务.

e) Brittle fracture can occur during ambient temperature hydrotesting due to high stresses and low toughness at the testing temperature. 室温试压时

API510/570-Exam

ASME VIII Div.1- Charlie Chong/ Fion Zhang

UCS-66 MATERIALS.

UCS-66

The main material property that API 510 / ASME VIII is concernedwith is that of resistance to brittle fracture. The fundamental issue is therefore whether a material is suitable for the minimum design metal temperature (MDMTdesign) for which a vessel is designed. This topic is covered by clause UCS-66 of ASME VIII.

ASME VIII Div.1- Charlie Chong/ Fion Zhang UCS-66

Steps:

1. UG-20 for exemption on impact testing.2. UCS-66.

• Identified material Group A,B,C,D. • Figure UCS-66 to determine the allowable MDMT.• Figure UCS-66.1 to determine the reduction in MDMT based on

coincident ratio.

3. UCS-68(c) to determine on further reduction in MDMT.


Figure UCS 66.1 Coincident Ratio

The Coincident Ratio is based on a vessel’s extra thickness due to its design calculations which were based on its Maximum Temperature.Meaning that; As metal’s temperature increases its strength decreases, hotter means weaker, therefore the allowable stress is decreased during calculations resulting in vessel that requires thicker walls when hot than when it is operating at its coldest temperature, the MDMT.

This ratio takes credit for the extra wall thickness that is present, but not needed to resist pressure at the MDMT. The following graphic will help. Usually when there is a drop in temperature there is also a drop in the pressure. The two operating conditions are calculated and the Ratio is determined. This Ratio is given on the exam and you need only use the table to apply this rule.


How to use FIG. UCS-66 & FIG. UCS-66.1 to determine allowable impact test value (MDMTallowable)


Steps:1. Determine material group.2. Determine MDMT allowable on

the graph.3. If Design MDMT higher than

MDMT allowable, no test requires.4. If MDMT allowable is higher than

design MDMT goto FIG. UCS-66.1


Steps:5. If the coincident ratio is 0.70

reduction of 30oF from the MDMT allowable. The revised MDMT’ allowable = 59oF.

6. If the revised MDMT’allowable is higher than the design MDMT, check on item 7.

7. If material is P1, UCS-68(c) If postweld heat treating is performed when it is not otherwise a requirement of this Division, a reduction of 30oF. The resulting MDMT allowable may be colder than -55oF.


Once the MDMT allowable had been ascertained, further reductions are possible by within -55ºF capping with exception

1. Low coincident stress ratio

2. postweld heat treating is performed when it is not otherwise a requirement of this Division on P1 materials.

- 55oF


UCS-66 (b2) For minimum design metal temperatures colder than -55ºF (-48ºC), impact testing is required for all materials, except as allowed in (b)(3) below and in UCS-68(c).

UCS-66 (b3) When the minimum design metal temperature is colder than -55ºF (-48ºC) and no colder than -155ºF (-105ºC), and the coincident ratio defined in Fig. UCS-66.1 is less than or equal to 0.35, impact testing is not required.


UCS-66 (b2) For minimum design metal temperatures colder than -55ºF (-48ºC), impact testing is required for all materials, except as allowed in (b)(3) below and in UCS-68(c).

UCS-68(c) If postweld heat treating is performed when it is not otherwise a requirement of this Division, a 30ºF (17ºC) reduction in impact testing exemption temperature may be given to the minimum permissible temperature from Fig. UCS-66 for P-No. 1 materials. The resulting exemption temperature may be colder than -55ºF (-48ºC).



a) Cracks will typically be straight, non-branching, and largely devoid of any associated plastic deformation (no shear lip or localized necking around the crack) (Figure 4-6 to Figure 4-7).宏观:直,不分枝,并在很大程度上没有任何相关的塑性变形.

b) Microscopically, the fracture surface will be composed largely of cleavage, with limited intergranular cracking and very little microvoid coalescence.微观: 主要为分裂(少量的沿晶开裂?)与非常小的微孔聚合

API510/570-Exam

API510/570-Exam

Crack propagation (cleavage) in brittle materials occurs through planar sectioning of the atomic bonds between the atoms at the crack tip.

API510/570-Exam

API510/570-Exam

API510/570-Exam


a) For new equipment, brittle fracture is best prevented by using materials specifically designed for low temperature operation including upset and auto-refrigeration events. Materials with controlled chemical composition, special heat treatment and impact test verification may be required. Refer to UCS 66 in Section VIII of the ASME BPV Code. 低温设备选材合适冲击要求材料

b) Brittle fracture is an “event” driven damage mechanism. For existing materials, where the right combination of stress, material toughness and flaw size govern the probability of the event, an engineering study can be performed in accordance with API 579-1/ASME FFS-1 , Section 3, Level 1 or 2. 脆裂为“事件”驱动的损伤机制(因素:应力, 韧性和裂纹尺寸)应用FFS-1适用性分析,评估设备完整性.

c) Preventative measures to minimize the potential for brittle fracture in existing equipment are limited to controlling the operating conditions (pressure, temperature), minimizing pressure at ambient temperatures during startup and shutdown, and periodic inspection at high stress locations. 维持 IOW 操作参数,周转期间启动,关断设备受压与温度控制与在高应力区的定期检查.

API510/570-Exam

d) Some reduction in the likelihood of a brittle fracture may be achieved by: 缓解行动有;

1. Performing a post weld heat treatment (PWHT) on the vessel if it was not originally done during manufacturing; or if the vessel has been weld repaired/modified while in service without the subsequent PWHT. 焊后热处理

2. Perform a “warm” pre-stress hydrotest followed by a lower temperature hydrotest to extend the Minimum Safe Operating Temperature (MSOT) envelope. 周转期间水压试验/温度控制.

API510/570-Exam


a) Inspection is not normally used to mitigate brittle fracture. 检验不能用来缓解脆性开裂

b) Susceptible vessels should be inspected for pre-existing flaws/defects. 易感容器的存在缺陷的监测

4.2.7.8 Related Mechanisms 相关机理

Temper embrittlement (see 4.2.3), strain age embrittlement (see 4.2.4), 885oF (475oC) embrittlement (see4.2.5), titanium hydriding (see 5.1.3.2) and sigma embrittlement (see 4.2.6).

脆性破裂作为形态定义时, 上述损坏机理, 破断形态可以归类为”脆性破裂”

Temper embrittlement

API510/570-Exam

API510/570-Exam

Ductile fracture (non creep type)

Valentino

高亮

Microvoid due to plastid yielding & ductile fracture (non creep type)

API510/570-Exam

Further reading:

http://www.sut.ac.th/engineering/metal/pdf/MechMet/14_Brittle%20fracture%20and%20impact%20testing.pdf

http://lecture.civilengineeringx.com/structural-analysis/structural-steel/brittle-fracture/

http://www.keytometals.com/articles/art136.htm

http://people.virginia.edu/~lz2n/mse209/Chapter8.pdf


http://www.techtransfer.com/resources/wiki/entry/3645/

API510/570-Exam

API510/570-Exam

Brittle Fracture

低温现象:室温/低于400oF, 影响材质:铁素体/马氏体钢, 焊后热处理作为预防与缓解方法, 周转期间设备处于低温状态时的受压控制(MSOT), 应用FFS-1合适性分析,评估带缺陷的设备可用性, 导致脆性开裂的因素有; (1) 低韧性铁素体钢材, (2) 服务导致脆化,例如; 回火

脆化,应变时效脆性,885oF脆化,钛氢化,西格玛的脆化.

4.2.8 Creep & Stress Rupture 蠕变和应力断裂非API 510/570考试科目

Creep & Stress Rupture 700oF ~ 1000oF

300, 400 & Duplex SS containing ferrite phases1000oF~ 1700oFSigma-Phase Embrittlement

300, 400 & Duplex SS containing ferrite phases600oF~ 1000oF885oF embrittlement

All metals and alloys700oF ~ 1000oFCreep & stress rupture


Pre-1980’s C-steels with large grain size and C- ½Mo

Intermediate temperature

Strain Aging


650oF~ 1070oFTempered Embrittlement

Low alloy steel up to 9% Cr850oF ~ 1400oFSpheroidization

Plain carbon steel

C- ½ Mo

800oF for C Steel

875oF for C ½ Mo Steel

Graphitisation

4.2.8 Creep and Stress Rupture 蠕变和应力开裂4.2.8.1 Description of Damage 描述

a) At high temperatures, metal components can slowly and continuously deform under load below the yield stress. This time dependent deformation of stressed components is known as creep.

b) Deformation leads to damage that may eventually lead to a rupture.

在高温和载荷低于屈服应力下,金属部件缓慢, 持续下的变形.这变形导致损伤,最终可能破裂.

4.2.8.2 Affected Materials 受影响的材料

All metals and alloys.所有的金属和合金。

http://www.ejsong.com/mdme/memmods/MEM30007A/properties/Properties.html

4.2.8.3 Critical Factors 蠕变和应力断裂关键因素

a) The rate of creep deformation is a function of the material, load, and temperature. The rate of damage (strain rate) is sensitive to both load and temperature. Generally, an increase of about 25°F (12°C) or an increase of 15% on stress can cut the remaining life in half or more, depending on the alloy. 影响蠕变的因素: (1) 材质易感性, (2) 负载和 (3) 温度, 例子: 25°F(12°C)或15%应力增加一般上导致使用寿面减半.

b) Table 4-3 lists threshold temperatures above which creep damage is a concern. If the metal temperature exceeds these values, then creep damage and creep cracking can occur. 表 4-3 列出不同材料的易感温度

c) The level of creep damage is a function of the material and the coincident temperature/stress level at which the creep deformation occurs. 蠕变破坏依赖温度与应力的组合影响.

d) The life of metal components becomes nearly infinite at temperatures below the threshold limit (Table 4-3) even at the high stresses near a crack tip. 低于易感温度时,甚至在高应力的使用下,材料几乎是无限的不受蠕变的影响.

e) The appearance of creep damage with little or no apparent deformation is often mistakenly referred to as creep embrittlement, but usually indicates that the material has low creep ductility.不是所有的蠕变失效具有明显的外表变形.低延展性蠕变在外观上不容易被识别.

f) Low creep ductility is:低延展性蠕变

1) More severe for higher tensile strength materials and welds. 高强材料2) More prevalent at the lower temperatures in the creep range, or low

stresses in the upper creep range. 普遍于(1)蠕变低温度范围或 (2)低应力高温度范围.

3) More likely in a coarse-grained material than a fine-grained material.粗晶材料

4) Not evidenced by a deterioration of ambient temperature properties. 低温机械性能不显著地退化.

5) Promoted by certain carbide types in some CrMo steels. 某些碳化物促进破坏

g) Increased stress due to loss in thickness from corrosion will reduce time to failure.腐蚀厚度损失加剧蠕变破坏

不是所有的蠕变失效具有明显的外表变形!低延展性蠕变

Is all creep failure associated with apparent deformation?The appearance of creep damage with little or no apparent deformation is often mistakenly referred to as creep embrittlement, but usually indicates that the material has low creep ductility.经常被误称蠕变脆化其实是低延展性蠕变

4.2.8.4 Affected Units or Equipment 受影响的设备

a) Creep damage is found in high temperature equipment operating above the creep range. Heater tubes in fired heaters are especially susceptible as well as tube supports, hangers and other furnace internals.一切高温设备,特别是加热器的加热管,管支架,吊架和炉内附件等.

b) Piping and equipment, such as hot-wall catalytic reforming reactors and furnace tubes, hydrogen reforming furnace tubes, hot wall FCC reactors, FCC main fractionator and regenerator internals all operate in or near the creep range. 催化裂化反应器的管道,罐壁,氢转化炉炉管,炉管等.

c) Low creep ductility failures have occurred in weld heat-affected zones (HAZ) at nozzles and other high stress areas on catalytic reformer reactors. Cracking has also been found at long seam welds in some high temperature piping and in reactors on catalytic reformers.催化重整反应器焊缝与热影响区

d) Welds joining dissimilar materials (ferritic to austenitic welds) may suffer creep related damage at high temperatures due to differential thermal expansion stresses.异种材料的焊接接合(例如:铁素体/奥氏体)经历因热膨胀差异导致的应力与高温蠕变.

4.2.8.6 Prevention / Mitigation 预防与缓解

a) There is little that inspectors or operators can do to prevent this damage once a susceptible material has been placed into creep service, other than to minimize the metal temperature, particularly with fired heater tubes. Avoiding stress concentrators is important during design and fabrication. (1) 温度控制与 (2) 设计时避免应力集中点.

b) Low creep ductility can be minimized by the careful selection of chemistry for low alloy materials. Higher post weld heat treatment temperatures may help minimize creep cracking of materials with low creep ductility such as 1.25Cr-0.5Mo.低合金钢的低延性蠕变; (1) 通过焊后热处理, (2)材料化学成分控制.

c) Creep damage is not reversible. Once damage or cracking is detected much of the life of the component has been used up and typically the options are to repair or replace the damaged component. Higher PWHT in some cases can produce a more creep ductile material with longer life.蠕变损伤是不可逆转

1. Equipment – Repair of creep damaged catalytic reformer reactor nozzles has been successfully accomplished by grinding out the affected area (making sure all the damaged metal is removed), re-welding and careful blend grinding to help minimize stress concentration. PWHT temperatures must be carefully selected and may require a higher PWHT than originally specified.催化重整反应器管口修护例子: (1) 磨出受影响的区域, (2) 修补焊接填充, (3) 打磨平滑减少应力集中, (4) 高于原设计的焊后热处理.

c2 Fired Heater Tubes 炉管

Alloys with improved creep resistance may be required for longer life.改进的抗蠕变性合金管

Heaters should be designed and operated to minimize hot spots and localized overheating (Figure 4-19). 减少热点和局部过热

Visual inspection followed by thickness measurements and or strap readings may be required to assess remaining life of heater tubes in accordance with API 579-1/ASME FFS-1.目视,捆扎法(测量外径变化)以识别受影响的管道.运用合适性分析法 FFS,评估受影响的管道是否能继续的使用.

Minimizing process side fouling/deposits and fire side deposits/scaling can maximize tube life.减少工艺侧的污垢/堆积,火侧的堆积/氧化皮加厚


a) Creep damage with the associated microvoid formation, fissuring and dimensional changes is not effectively found by any one inspection technique. A combination of techniques (UT, RT, EC, dimensional measurements and replication) should be employed. Destructive sampling and metallographic examination are used to confirm damage. 蠕变体现为微孔,裂隙与尺寸变化.当个无损探伤方法或许不容易探测到蠕变破坏. 综合考虑运用多种探伤方法与晶相模塑法(in-situ replication)或切片晶相微观观察.

b) For pressure vessels, inspection should focus on welds of CrMo alloys operating in the creep range. The 1 Cr-0.5Mo and 1.25Cr-0.5Mo materials are particularly prone to low creep ductility. Most inspections are performed visually and followed by PT or WFMT on several-year intervals. Angle beam (shear wave) UT can also be employed, although the early stages of creep damage are very difficult to detect. Initial fabrication flaws should be mapped and documented for future reference. 铬钼材质特别是焊缝区域是检验关注点. 多数的检验步骤为; (1) 外观目视 (2) PT/WFMT (2+)斜束剪切波UT. (提防建造缺陷导致误判)

c) Fired heater tubes should be inspected for evidence of overheating, corrosion, and erosion as follows:炉管检验

1. Tubes should be VT examined for bulging, blistering, cracking, sagging and bowing. 目视观察;鼓,起泡,开裂和弯曲与垂落.

2. Wall thickness measurements of selected heater tubes should be made where wall losses are most likely to occur. 厚度检测

3. Tubes should be examined for evidence of diametric growth (creep) with a strap or go/no go gauge, and in limited cases by metallography on in place replicas or tube samples. However, metallography on the OD of a component may not provide a clear indication of subsurface damage. 检测外径变化(上下限制测量规),现场晶相模塑法(replica)

4. Retirement criteria based on diametric growth and loss of wall thickness is highly dependent on the tube material and the specific operating conditions. 基于直径生长和损失的壁厚的报废准则很大程度上依赖于管材与具体操作条件.

4.2.8.8 Related Mechanisms 相关机理

a) Creep damage that occurs as a result of exposure to very high temperatures is described in 4.2.10. (Overheating stress rupture过热的应力破裂)

b) Reheat cracking (see 4.2.19) is a related mechanism found in heavy wall equipment.再热裂纹- 厚壁的设备发现的相关机理

Figure 4-17 – Pinched Alloy 800H pigtail opened up creep fissures on the surface.

Figure 4-18 – Creep rupture of an HK40 heater tube.

Figure 4-19 – Creep Failure of 310 SS Heater Tube Guide Bolt after approximately 7 years service at 1400°F (760°C). a.) Cross-section at 10X, as-polished.

a

b

Figure 4-19 – Creep Failure of 310 SS Heater Tube Guide Bolt after approximately 7 years service at 1400°F (760°C). b) Voids and intergranular separation characteristic of long term creep, 100X, etched.

a

b

蠕变和应力开裂学习重点:

1. 温度: 高温,2. 原理:在高温和载荷低于屈服应力下,金属部件缓慢, 持续下的变形.这变

形导致损伤,最终可能破裂.3. 易感材质:全部工程材料.4. 易感设备:一切高温设备,特别是加热器的加热管,内构件.5. 非API 510/570考试题非API 510/570考试题

4.2.9 Thermal Fatigue 热疲劳

API510/570-Exam

Thermal FatigueOperating Temp.

API510/570-Exam

All metals and alloys700oF ~ 1000oFCreep & stress rupture

300, 400 & Duplex SS containing ferrite phases1000oF~ 1700oFSigma-Phase Embrittlement

300, 400 & Duplex SS containing ferrite phases600oF~ 1000oF885oF embrittlement

All metals and alloysOperating temp.Thermal fatigues


Pre-1980’s C-steels with large grain size and C- ½Mo

Intermediate temperature

Strain Aging


650oF~ 1070oFTempered Embrittlement

Low alloy steel up to 9% Cr850oF ~ 1400oFSpheroidization

Plain carbon steel

C- ½ Mo

800oF for C Steel

875oF for C ½ Mo Steel

Graphitisation

API510/570-Exam

4.2.9 Thermal Fatigue 热疲劳4.2.9.1 Description of Damage 损伤描述

Thermal fatigue is the result of cyclic stresses caused by variations in temperature. Damage is in the form of cracking that may occur anywhere in a metallic component where relative movement or differential expansion is constrained, particularly under repeated thermal cycling.热疲劳开裂是由温度变化引起循环应力引起的开裂.

4.2.9.2 Affected Materials 受影响的材料

All materials of construction. 所有施工材料

API510/570-Exam

API510/570-Exam


a) Key factors affecting thermal fatigue are the magnitude of the temperature swing and the frequency (number of cycles). 温度摆动的幅度和频率

b) Time to failure is a function of the magnitude of the stress and the number of cycles and decreases with increasing stress and increasing cycles.故障时间有赖于(1)温度摆动的幅度 (2)频率 (3)应力的大小

c) Startup and shutdown of equipment increase the susceptibility to thermal fatigue. There is no set limit on temperature swings; however, as a practical rule, cracking may be suspected if the temperature swings exceeds about 200°F (93°C). 周转/启动/停机增加热疲劳的易感性. 作为一个实际的规则大于200°F摆动幅度作为热疲劳损伤怀疑点.

API510/570-Exam

d) Damage is also promoted by rapid changes in surface temperature that result in a thermal gradient through the thickness or along the length of a component. For example: cold water on a hot tube (thermal shock); rigid attachments and a smaller temperature differential; inflexibility to accommodate differential expansion.促进因素:沿着管道长度或厚度的温度偏差,自由膨胀阻碍(缺少弹性的设计)

e) Notches (such as the toe of a weld) and sharp corners (such as the intersection of a nozzle with a vessel shell) and other stress concentrations may serve as initiation sites. 缺口-焊趾处, 尖锐点 (应力集中点).

API510/570-Exam


a) Examples include the mix points of hot and cold streams such as hydrogen mix points in hydroprocessing units 加氢装置, and locations where condensate comes in contact with steam systems, such as de-superheating or attemporating equipment 减温装置 (Figures 4-20 and 4-23). 不同温度流体混合点.

b) Thermal fatigue cracking has been a major problem in coke drum shells. Thermal fatigue can also occur on coke drum skirts where stresses are promoted by a variation in temperature between the drum and skirt (Figure 4–21 and Figure 4–22).焦炭鼓裙边与塔壁. (考试题)

c) In steam generating equipment, the most common locations are at rigid attachments between neighboring tubes in the superheater and reheater. Slip spacers designed to accommodate relative movement may become frozen and act as a rigid attachment when plugged with fly ash.蒸汽发生装置(过热器和再热器管路)

API510/570-Exam

Figure 4-20 – Thermal fatigue cracks on the inside of a heavy wall SS pipe downstream of a cooler H2 injection into a hot hydrocarbon line.

API510/570-Exam

Figure 4-21 – Bulging in a skirt of a coke drum.

API510/570-Exam

Figure 4-22 –Thermal fatigue cracking associated with bulged skirt shown in Figure 4-21.

API510/570-Exam

Figure 4-23 – Thermal fatigue of 304L stainless at mix point in the BFW preheaterbypass line around the high temperature shift effluent exchanger in a hydrogen reformer. The delta T is 325°F (181°C) at an 8 inch bypass line tying into a 14 inch line, 3 yrs after startup.

API510/570-Exam

Figure 4-24 – In a carbon steel sample, metallographic section through a thermal fatigue crack indicates origin at the toe of an attachment weld. Mag. 50X, etched.

API510/570-Exam

Figure 4-25 – Older cracks fill with oxide, may stop and restart (note jog part way along the crack), and do not necessarily require a change in section thickness to initiate the crack. Mag. 100X, etched.

API510/570-Exam

d) Tubes in the high temperature superheater or reheater that penetrate through the cooler water-wall tubes may crack at the header connection if the tube is not sufficiently flexible. These cracks are most common at the end where the expansion of the header relative to the water-wall will be greatest.穿过水冷冷却器壁的过热器,再热器管路.

d) Steam actuated soot blowers may cause thermal fatigue damage if the first steam exiting the soot blower nozzle contains condensate. Rapid cooling of the tube by the liquid water will promote this form of damage. Similarly, water lancing or water cannon use on water-wall tubes may have the same effect. (1) 蒸汽驱动的吹灰器接触冷凝液的热管路, (2) 其他接触冷凝液的热管路服务.

API510/570-Exam

API510/570-Exam

http://www.slashgear.com/bill-gates-helping-china-build-super-safe-nuclear-reactor-08200894/

API510/570-Exam

4.2.9.5 Appearance or Morphology of Damage 破坏外观形貌

a) Thermal fatigue cracks usually initiate on the surface of the component. They are generally wide and often filled with oxides due to elevated temperature exposure. Cracks may occur as single or multiple cracks.表面发起点, 开裂表面氧化,裂缝可能为单个或多个裂纹延伸.

b) Thermal fatigue cracks propagate transverse to the stress and they are usually dagger-shaped, transgranular, and oxide filled (Figure 4-24 and 4-25). However, cracking may be axial or circumferential, or both, at the same location. 应力方向横向开裂, 穿晶,氧化,刀纹状(?),开裂方向为; 轴向或圆周向或并存.

API510/570-Exam

c) In steam generating equipment, cracks usually follow the toe of the fillet weld, as the change in section thickness creates a stress raiser. Cracks often start at the end of an attachment lug and if there is a bending moment as a result of the constraint, they will develop into circumferential cracks into the tube.在蒸汽发生装置, 通常开裂起点在焊道应力集中点,周圆的延伸.

d) Water in soot blowers may lead to a crazing pattern. The predominant cracks will be circumferential and the minor cracks will be axial. (Figure 4-26 to 4-27). 水助吹灰器的裂纹一般上体现为纹状.

API510/570-Exam

Figure 4-26 – Metallographic cross-section of a superheated steam outlet that failed from thermal fatigue. Unetched.

Figure 4-27 – Photomicrograph of the failed superheated steam outlet shown in Figure 4-26.Etched.

API510/570-Exam


a) Thermal fatigue is best prevented through design and operation to minimize thermal stresses and thermal cycling. Several methods of prevention apply depending on the application.

1. Designs that incorporate reduction of stress concentrators, blend grinding of weld profiles, and smooth transitions should be used. 减少应力集中,焊缝节点疲劳处理,圆滑过渡.

2. Controlled rates of heating and cooling during startup and shutdown of equipment can lower stresses. 周转(开机,关机)控制加热和冷却速率.

3. Differential thermal expansion between adjoining components of dissimilar materials should be considered.设计阶段考虑异种材料之间的差热膨胀.

API510/570-Exam

b) Designs should incorporate sufficient flexibility to accommodate differential expansion. 设计时考虑具有足够的灵活性

1. In steam generating equipment, slip spacers should slip and rigid attachments should be avoided.滑动垫片.

2. Drain lines should be provided on soot-blowers to prevent condensate in the first portion of the soot blowing cycle.吹灰器安装排水线避免冷凝液聚集.

3. In some cases, a liner or sleeve may be installed to prevent a colder liquid from contacting the hotter pressure boundary wall 安装衬垫或套用于防止冷液体接触热的压力边界墙

API510/570-Exam

4.2.9.7 Inspection and Monitoring 检查和监督

a) Since cracking is usually surface connected, visual examination, MT and PT are effective methods of inspection.由于裂缝通常是表面连接 MT/PT是有效的检查方法.

b) External SWUT inspection can be used for non-intrusive inspection for internal cracking and where reinforcing pads prevent nozzle examination.切波角度超声可以用于非侵入性检查,例如:被补强板妨碍的容器/管口区域.

c) Heavy wall reactor internal attachment welds can be inspected using specialized ultrasonic techniques.厚壁反应器内部连接焊缝运用切波角度超声探测法

4.2.9.8 Related Mechanisms 相关机制

Corrosion fatigue (see 4.5.2) and dissimilar metal weld cracking (see 4.2.12).腐蚀疲劳,异种金属焊缝开裂.

API510/570-Exam

Charlie Chong/ Fion Zhang571-4

API510/570-Exam

API510/570-Exam

热疲劳学习重点:

a) 易感温度: 高温b) 原理:热疲劳开裂是由温度变化引起循环应力引起的开裂,c) 易感材质: 一切工程材料,d) 易感设备:蒸汽发生装置,蒸汽驱动的吹灰器等,高温设备,e) API 510/570考试题.

4.2.10 Short Term Overheating Stress Rupture 短期过热应力开裂非API 510/570考试题

Short Term Overheating Stress RuptureLocal over-heating.

4.2.10 Short Term Overheating – Stress Rupture4.2.10.1 Description of Damage 损伤描述

Permanent deformation occurring at relatively low stress levels as a result of localized overheating. This usually results in bulging and eventually failure by stress rupture.

4.2.10.2 Affected Materials 影响材质

All fired heater tube materials and common materials of construction.一切建造材料


a) Temperature, time and stress are critical factors. 温度,时间,应力

a) Usually due to flame impingement or local overheating.火焰冲击或局部过热

b) Time to failure will increase as internal pressures or loading decrease. However, bulging and distortion can be significant at low stresses, as temperatures increase. 失效时间随着内部压力或负载减少增长.

c) Local overheating above the design temperature.局部过热

d) Loss in thickness due to corrosion will reduce time to failure by increasing the stress.由于腐蚀厚度损失增加易感性.

4.2.10.4 Affected Units or Equipment受影响的单元或设备

a) All boiler and fired heater tubes are susceptible.所有锅炉和加热炉管

b) Furnaces with coking tendencies such as crude, vacuum, heavy oilhydroprocessing and coker units are often fired harder to maintain heater outlet temperatures and are more susceptible to localized overheating.焦化倾向的设备

c) Hydroprocessing reactors may be susceptible to localized overheating of reactor beds due to inadequate hydrogen quench or flow mal-distribution.氢反应器-易受局部过热加反应器床

d) Refractory lined equipment in the FCC, sulfur plant and other units may suffer localized overheating due to refractory damage and/or excessive firing.催化裂化,硫磺厂与其他可能遭受局部过热的耐火材料衬里的设备.

4.2.10.5 Appearance or Morphology of Damage 破坏外观形貌

a) Damage is typically characterized by localized deformation or bulging on the order of 3% to 10% or more, depending on the alloy, temperature and stress level.损坏的典型特征是局部变形或膨胀(3%~10% 或更多)

b) Ruptures are characterized by open “fishmouth” failures and are usually accompanied by thinning at the fracture surface (Figure 4-28 to 4-31).破裂的特点是在变薄断裂面 “鱼嘴”形象的开裂的特征.


a) Minimize localized temperature excursions. 减少局部温度漂移b) Fired heaters require proper burner management and fouling/deposit

control to minimize hot spots and localized overheating.火焰加热器需要适当的燃烧器管理/污垢和沉积控制以减少局部过热.

c) Utilize burners which produce a more diffuse flame pattern.d) In hydroprocessing equipment, install and maintain bed thermocouples in

reactors and minimize the likelihood of hot spots through proper design and operation.

e) Maintain refractory in serviceable condition in refractory lined equipment.

短期过热应力开裂学习重点:

a) 易感温度: 高温b) 原理:热疲劳开裂是由温度变化引起循环应力引起的开裂,c) 易感材质: 一切工程材料,d) 易感设备:蒸汽发生装置,蒸汽驱动的吹灰器等,高温设备,e) 非API 510/570考试题.

4.2.11 Steam Blanketing 蒸汽封

Steam Blanketing Local over-heating.

4.2.11 Steam Blanketing4.2.11.1 Description of Damage

The operation of steam generating equipment is a balance between the heat flow from the combustion of the fuel and the generation of steam within the waterwall or generating tube. The flow of heat energy through the wall of the tube results in the formation of discrete steam bubbles (nucleate boiling) on the ID surface. The moving fluid sweeps the bubbles away. When the heat flow balance is disturbed, individual bubbles join to form a steam blanket, a condition known as Departure From Nucleate Boiling (DNB). Once a steam blanket forms, tube rupture can occur rapidly, as a result of short term overheating, usually within a few minutes.


Carbon steel and low alloy steels.

individual bubbles join to form a steam blanket, a condition known as Departure From Nucleate Boiling (DNB).

Heat transfer and mass transfer during nucleate boiling has a significant effect on the heat transfer rate. This heat transfer process helps quickly and efficiently to carry away the energy created at the heat transfer surface and is therefore sometimes desirable - for example in nuclear power plants, where liquid is used as a coolant.The effects of nucleate boiling take place at two locations:

• the liquid-wall interface• the bubble-liquid interface

http://en.wikipedia.org/wiki/Nucleate_boiling


a) Heat flux and fluid flow are critical factors.b) Flame impingement from misdirected or damaged burners can provide a

heat flux greater than the steam generating tube can accommodate.c) On the water side, anything that restricts fluid flow (for example, pinhole

leaks lower in the steam circuit or dented tubes from slag falls) will reduce fluid flow and can lead to DNB conditions.

d) Failure occurs as a result of the hoop stress in the tube from the internal steam pressure at the elevated temperature.


All steam-generating units including fired boilers, waste heat exchangers in sulfur plants, hydrogen reformers and FCC units. Failures can occur in superheaters and reheaters during start-up when condensate blocks steam flow.


a) These short-term, high-temperature failures always show an open burst with the fracture edges drawn to a near knife-edge (Figure 4-32).

b) The microstructure will always show severe elongation of the grain structure due to the plastic deformation that occurs at the time of failure.

Figure 4-32 – Short-term high-temperature failures from DNB are wide-open bursts with the failure lips drawn to a near knife edge. They are ductile ruptures. Mag. 25X.


a) When a DNB condition has developed, tube rupture will quickly follow. Proper burner management should be practiced to minimize flame impingement.

b) Proper BFW treatment can help prevent some conditions that can lead to restricted fluid flow.

c) Tubes should be visually inspected for bulging.


Burners should be properly maintained to prevent flame impingement.

Causes of Caustic CrackingCaustic is a boiler water additive. It is added to preserve the thin film of iron oxide to protect the boiler from corrosion. The

following are the causes of concentration of caustics:

1. Small bubbles of steam nucleated at the metal surface in minute concentrations of solids in the boiler water would be deposited on the metal surface. As the solids are formed they are simultaneously removed from the metal surface by water which re-dissolves them. However, when the rate of bubble formation exceeds the rate of dissolution of the solids, concentration of caustics would begin to increase.

2. The deposits of solids shield the metal from the back water. Steam forms under the deposits and escapes leaving behind a caustic residue.

3. Caustic also concentrates by evaporation if a water line exists.

MechanismConcentrated caustic dissolves the protective magnetite oxides

http://faculty.kfupm.edu.sa/ME/hussaini/Corrosion%20Engineering/04.10.01.htm

蒸汽封学习重点:

a) 易感温度: 高温b) 原理:当热流量平衡被打破，单个气泡的加入形成蒸汽毛毯，一种被称

为偏离泡核沸腾,c) 易感材质:碳钢和低合金钢,d) 易感设备:所有蒸汽发电机组包括锅炉,硫磺厂余热换热器,制氢转化炉和

催化裂化装置,e) 预防/缓解: 锅炉热管理(火焰,锅炉水管理), 锅炉管目视检验.f) 非API 510/570考试题.

4.2.12 Dissimilar Weld Cracking 异种钢焊接开裂

4.2.12 Dissimilar Metal Weld (DMW) Cracking4.2.12.1 Description of Damage

Cracking of dissimilar metal welds occurs in the ferritic (carbon steel or low alloy steel) side of a weld between an austenitic (300 Series SS) and a ferritic material operating at high temperature.


The most common are ferritic materials such as carbon steel and low alloy steels that are welded to the austenitic stainless steels as well as any material combinations that have widely differing thermal expansion coefficients.


a) Important factors include the type of filler metal used to join the materials, heating and cooling rate, metal temperature, time at temperature, weld geometry and thermal cycling.

b) Cracking can occur because of the different coefficients of thermal expansion between ferritic and austenitic (e.g. 300 Series stainless steel or nickel-base alloys) which differ by about 25 to 30% or more. At high operating temperatures, the differences in thermal expansion leads to high stress at the heat-affected zone on the ferritic side (Table 4-4).

c) As the operating temperature increases, differential thermal expansion between the metals results in increasing stress at the weldment,particularly if a 300 Series SS weld metal is used. Ferritic/austenitic joints can generate significant thermal expansion/thermal fatigue stresses at temperatures greater than 510°F (260°C).

Table 4-4: Coefficients of Thermal Expansion for Common Materials

Ferritic/austenitic joints can generate significant thermal expansion/thermal fatigue stresses at temperatures greater than 510°F (260°C).

> 510°F

d) Thermal cycling aggravates the problem. Stresses during start up and shut down can be significant.

e) Stresses acting on the weldment are significantly higher when an austenitic stainless steel filler metal is used. A nickel base filler metal has a coefficient of thermal expansion that is closer to carbon steel, resulting in significantly lower stress at elevated temperatures.

f) For dissimilar welds that operate at elevated temperatures, the problem is aggravated by the diffusion of carbon out of the heat-affected zone of the ferritic material and into the weld metal. The loss of carbon reduces the creep strength of the ferritic material heat-affected zone, thereby increasing the cracking probability (Figure 4-35). The temperature at which carbon diffusion becomes a concern is above 800°F to 950°F (427°C to 510°C) for carbon steels and low alloy steels, respectively.

Figure 4-35 – High magnification photomicrograph of a DMW joining a ferritic alloy (SA213 T-22) used in high temperature service. Creep cracks (black specks) can be observed in the ferritic alloy heat-affected zones. Mag. 50X, etched.

Austenitic Steel Ferritic Steel

Creep void due to loss of Carbon at HAZ

g) Dissimilar metal welds on a ferritic steel that are made with a 300 Series SS weld metal or a nickel based filler metal result in a narrow region (mixed zone) of high hardness at the toe of the weld, near the fusion line on the ferritic steel side. These high hardness zones render the material susceptible to various forms of environmental cracking such as sulfide stress cracking or hydrogen stress cracking (Figures 4-36 and 4-37). PWHT of the weldment will not prevent environmental cracking if the weld is exposed to wet H2S conditions.(?)

h) DMW’s for high temperature service in hydrogen environments must be carefully designed and inspected to prevent hydrogen disbonding (Figures 4-38 to 4-41).

Figure 4-36 – Weld detail used to join a carbon steel elbow (bottom) to a weld overlaid pipe section (top) in high pressure wet H2S service. Sulfide stress cracking (SSC) occurred along the toe of the weld (arrow), in a narrow zone of high hardness.

Environmental Cracking – Ambient service

Figure 4-37 – High magnification photomicrograph of SSC in pipe section shown in Figure 4-36.

Environmental Cracking – Ambient service

Figure 4-38 – Failure of DMW joining 1.25Cr-0.5Mo to Alloy 800H in a Hydro-dealkylation(HAD) Reactor Effluent Exchanger. Crack propagation due to stresses driven at high temperature of 875°F (468°C) and a hydrogen partial pressure of 280 psig (1.93 MPa).

Blister

High temperature service

Blister

Figure 4-39 – High magnification photomicrograph of the crack in Figure 4-38 showing blistering and disbondment along the weld fusion line interface.


Figure 4-40 – High magnification photomicrograph of the crack shown above in Figure 4-39. Plastic deformation of the grain structure can be found at the vicinity of the blister.


Figure 4-41 – Failure of nickel alloy DMW joining HP40 (Nb modified) tube to 1.25Cr-0.5Mo flange in a Steam Methane Reformer due to cold hydrogen disbonding of the buttering layer. Process temperature 914°-941°F (490o to 505°C), Pressure (2.14 MPA), H2 content 10-20% (off-gas).


i) In environments that promote liquid ash corrosion, weld cracking problems may be accelerated by stress-assisted corrosion. The ferritic heat-affected zone will preferentially corrode due to the large thermal strain. The results are long, narrow, oxide wedges that parallel the fusion line of the weld (Figure 4-42).

j) Poor geometry of the weld, excessive undercut, and other stress intensification factors will promote crack formation.

Figure 4-42 – When both liquid phase coal ash corrosion and a DMW exists, stress assisted corrosion of the 2.25 Cr-1Mo heat-affected zone may occur. Note that there is a lack of creep damage at the crack tip. Mag. 25X, etched.

Intergranular liquid metal embrittlement (coal ash corrosion)


a) Dissimilar metal welds are utilized in special applications in refineries and other process plants.

b) Examples of DMW’s include:

Welds used to join clad pipe in locations such as transitions inhydroprocessing reactor outlet piping from overlaid low alloy CrMo nozzles or piping to solid 300 Series stainless steel pipe.

Hydroprocessing exchanger inlet and outlet piping. Alloy transitions inside fired heaters (e.g. 9Cr to 317L in a crude furnace) Hydrogen reformer furnace 1.25 Cr inlet pigtails to Alloy 800 sockolets or

weldolets on Hydrogen reformer tubes Hydrogen reformer furnace Alloy 800 outlet cones to CS or 1.25 Cr

refractory lined transfer lines.

Alloy transitions inside fired heaters (e.g. 9Cr to 317L in a crude or vacuum furnace)

Welds joining clad pipe sections to themselves or to unclad carbon or low alloy steel pipe (e.g. Alloy C276 clad CS piping in crude unit overhead system)

Nickel base alloy welds joining socket weld valves in 5 and 9 Cr piping systems

300 series SS weld overlay in numerous refinery reactors and pressure vessels

Similar DMWs have been used in FCCU reactors and regenerator vessels and in Coker Units.

c) All superheaters and reheaters that have welds between ferritic materials (1.25Cr-0.5Mo and 2.25Cr-1Mo) and the austenitic materials (300 Series SS, 304H, 321H and 347H).


a) In most cases, the cracks form at the toe of the weld in the heat-affected zone of the ferritic material (Figure 4-36 to Figure 4-42).

b) Welds joining tubes are the most common problem area, but support lugs or attachments of cast or wrought 300 Series SS to 400 Series SS are also affected.


a) For high temperature applications, nickel base filler metals which have a coefficient of thermal expansion closer to carbon steel and low alloy steels may dramatically increase the life of the joint, because of the significant reduction in thermal stress acting on the steel (ferritic) side of the joint. Refer to API 577 and API 582 for additional information on filler metal selection, welding procedures and weld inspection.

b) If 300 Series SS welding electrodes are used, the dissimilar metal weld should be located in a low temperature region.

c) Consider buttering the ferritic side of the joint with the SS or nickel base filler metal and perform PWHT prior to completing the DMW to minimize the hardness of the mixed weld zone in order to minimize susceptibility to environmental cracking. See Figure 4-34 and 4-35.(Figure 4-33 and 4-34)

d) On buttered joints, the thickness of the weld metal should be a minimum of 0.25 inch (6.35 mm) after the bevel is machined. Figure 4-35.(Figure 4-34)

Figure 4-33 – Two primary DMW configurations.a ) Ferritic steel pipe (left) welded to clad or weld overlaid pipe (right)

b) Solid Stainless steel pipe (left) welded to clad or weld overlaid pipe (right)

Figure 4-34 – Schematic of typical weld detail used to join a solid stainless steel pipe to a clad or weld overlaid pipe. The sequence is: 1) Butter the weld bevel on the ferritic steel side, 2) Perform PWHT of the ferritic side prior to making dissimilar weld, 3) Complete the dissimilar weld using alloy filler metal, 4) Do not PWHT the completed dissimilar weld.

e) In steam generating equipment, the weld at the high temperature end should be made in the penthouse or header enclosure, out of the heat transfer zone.

f) For high temperature installations, consider Installing a pup piece that has an intermediate thermal expansion coefficient between the two materials to be joined.


a) The following elements should be considered for non-destructive examination of critical dissimilar butt welds before they are put into service:

• 100% PT after buttering and completion• 100% UT on butter layer after PWHT (check bonding)• 100% RT• 100% UT – recordable• PMI

b) For dissimilar welds in fired heater tubes, RT and UT shear waveinspection should be performed.

c) Environmental cracking will also result in surface breaking cracks initiating on the ID surface exposed to the corrosive environment, which can be detected using WFMT or external SWUT methods.


Thermal fatigue (see 4.2.9), corrosion fatigue (see 4.5.2), creep (see 4.2.8), and sulfide stress cracking(see 5.1.2.3.)

异种钢焊接开裂学习重点:

a) 易感温度: 室温与高温两种b) 原理: (1) 室温感应- 铁素体混合区高强度导致环境开裂与氢裂, (2) 高温

感应- 铁素体热影响区脱碳导致高温强度降低与蠕变强度.c) 易感材质: 铁素体/奥氏体异种焊接,d) 非 API510/570考试题

4.2.13 Thermal Shock 热冲击

4.2.13 Thermal Shock 温度突变4.2.13.1 Description of Damage

A form of thermal fatigue cracking – thermal shock – can occur when high and non-uniform thermal stresses develop over a relatively short time in a piece of equipment due to differential expansion or contraction. If the thermal expansion/contraction is restrained, stresses above the yield strength of the material can result. Thermal shock usually occurs when a colder liquid contacts a warmer metal surface.

当的液体接触一个高温的金属表面时, 在很短的时间, 高和非均匀的热应力发生.如果热膨胀/收缩受到抑制, 可能会导致材料的屈服强度以上的应力.


All metals and alloys.


a) The magnitude of the temperature differential and the coefficient of thermal expansion of the material determine the magnitude of the stress.

b) Cyclic stresses generated by temperature cycling of the material may initiate fatigue cracks.

c) Stainless steels have higher coefficients of thermal expansion than carbon and alloy steels or nickel base alloys and are more likely to see higher stresses.

d) High temperature exposure during a fire.e) Temperature changes that can result from water quenching as a result of

rain deluges.

f) Fracture is related to constraint on a component that prevents the component from expanding or contracting with a change in temperature.

g) Cracking in cast components such as valves may initiate at casting flaws on the ID and progress through the thickness.

h) Thick sections can develop high thermal gradients.


a) FCC, cokers, catalytic reforming and high severity hydroprocessing units are high temperature units where thermal shock is possible.

b) High temperature piping and equipment in any unit can be affected.

c) Materials that have lost ductility, such as CrMo equipment (temper embrittlement) are particularly susceptible to thermal shock.

d) Equipment subjected to accelerated cooling procedures to minimize shutdown time.


Surface initiating cracks may also appear as “craze” cracks.


a) Prevent interruptions in the flow of high temperature lines.b) Design to minimize severe restraint.c) Install thermal sleeves to prevent liquid impingement on the pressure

boundary components.d) Minimize rain or fire water deluge situations.e) Review hot/cold injection points for potential thermal shock.


a) This type of damage is highly localized and difficult to locate.b) PT and MT can be used to confirm cracking.


Thermal fatigue (see 4.2.9).

高温突变学习重点:

a) 易感温度: 高温b) 原理:当冷液体接触高温的金属表面时,高和非均匀的热应力发生.在热膨

胀/收缩受到抑制下形成屈服强度以上的应力,导致材料开裂.c) 易感材质: 一切工程材料,d) 易感设备:高温设备,e) 非API 510/570考试题

4.2.14 Erosion/ Erosion Corrosion 冲刷腐蚀

API510/570-Exam

4.2.14 Erosion/Erosion – Corrosion 冲蚀/冲蚀-腐蚀4.2.14.1 Description of Damage

a) Erosion is the accelerated mechanical removal of surface material as a result of relative movement between, or impact from solids, liquids, vapor or any combination thereof.

b) Erosion-corrosion is a description for the damage that occurs when corrosion contributes to erosion by removing protective films or scales, or by exposing the metal surface to further corrosion under the combined action of erosion and corrosion.

• 冲蚀 - 当材料表面(固体, 液体, 气体或它们的任何组合) 之间的相对运动/撞击的影响而加速材料表面机械去除.

• 冲蚀-腐蚀 - 腐蚀导致侵金属表面保护膜/氧化皮的丢失, 冲蚀机表面去除,冲蚀-腐蚀的协作效应加深便面损坏.


All metals, alloys and refractory.

API510/570-Exam

API510/570-Exam


a) In most cases, corrosion plays some role so that pure erosion (sometimes referred to as abrasive wear) is rare. It is critical to consider the role that corrosion contributes.

b) Metal loss rates depend on the velocity and concentration of impacting medium (i.e., particles, liquids, droplets, slurries, two-phase flow), the size and hardness of impacting particles, the hardness and corrosion resistance of material subject to erosion, and the angle of impact.

c) Softer alloys such as copper and aluminum alloys that are easily worn from mechanical damage may be subject to severe metal loss under high velocity conditions.

d) Although increasing hardness of the metal substrate is a common approach to minimize damage, it is not always a good indicator of improved resistance to erosion, particularly where corrosion plays a significant role.

API510/570-Exam

e) For each environment-material combination, there is often a threshold velocity above which impacting objects may produce metal loss. Increasing velocities above this threshold result in an increase in metal loss rates as shown in Table 4-5. This table illustrates the relative susceptibility of a variety of metals and alloys to erosion/corrosion by seawater at different velocities.

f) The size, shape, density and hardness of the impacting medium affect the metal loss rate.

g) Increasing the corrosivity of the environment may reduce the stability of protective surface films and increase the susceptibility to metal loss. Metal may be removed from the surface as dissolved ions, or as solid corrosion products which are mechanically swept from the metal surface.

h) Factors which contribute to an increase in corrosivity of the environment, such as temperature, pH, etc., can increase susceptibility to metal loss.

API510/570-Exam


a) All types of equipment exposed to moving fluids and/or catalyst are subject to erosion and erosion corrosion. This includes piping systems, particularly the bends, elbows, tees and reducers; piping systems downstream of letdown valves and block valves; pumps; blowers; propellers; impellers; agitators; agitated vessels; heat exchanger tubing; measuring device orifices; turbine blades; nozzles; ducts and vapor lines; scrapers; cutters; and wear plates.

b) Erosion can be caused by gas borne catalyst particles or by particles carried by a liquid such as a slurry. In refineries, this form of damage occurs as a result of catalyst movement in FCC reactor/regenerator systems in catalyst handling equipment (valves, cyclones, piping, reactors) and slurry piping (Figure 4-43); coke handling equipment in both delayed and fluidized bed cokers (Figure 4-44); and as wear on pumps (Figure 4-45), compressors and other rotating equipment.

API510/570-Exam

c) Hydroprocessing reactor effluent piping may be subject to erosion-corrosion by ammonium bisulfide. The metal loss is dependent on several factors including the ammonium bisulfide concentration, velocity and alloy corrosion resistance.

d) Crude and vacuum unit piping and vessels exposed to naphthenic acids in some crude oils may suffer severe erosion-corrosion metal loss depending on the temperature, velocity, sulfur content and TAN level.

API510/570-Exam


a) Erosion and erosion-corrosion are characterized by a localized loss in thickness in the form of pits, grooves, gullies, waves, rounded holes and valleys. These losses often exhibit a directional pattern.

b) Failures can occur in a relatively short time.

API510/570-Exam


a) Improvements in design involve changes in shape, geometry and materials selection. Some examples are: increasing the pipe diameter to decrease velocity; streamlining bends to reduce impingement; increasing the wall thickness; and using replaceable impingement baffles.

b) Improved resistance to erosion is usually achieved through increasing substrate hardness using harder alloys, hardfacing or surface-hardening treatments. Erosion resistant refractories in cyclones and slide valves have been very successful.

API510/570-Exam

c) Erosion-corrosion is best mitigated by using more corrosion-resistant alloys and/or altering the process environment to reduce corrosivity, for example, deaeration, condensate injection or the addition of inhibitors. Resistance is generally not improved through increasing substrate hardness alone.

d) Heat exchangers utilize impingement plates and occasionally tube ferrules to minimize erosion problems.

e) Higher molybdenum containing alloys are used for improved resistance to naphthenic acid corrosion.

API510/570-Exam


a) Visual examination of suspected or troublesome areas, as well as UT checks or RT can be used to detect the extent of metal loss.

b) Specialized corrosion coupons and on-line corrosion monitoring electrical resistance probes have been used in some applications.

c) IR scans are used to detect refractory loss on stream.


Specialized terminology has been developed for various forms of erosion and erosion-corrosion in specific environments and/or services. This terminology includes cavitation, liquid impingement erosion, fretting and other similar terms.

API510/570-Exam

Figure 4-43 – Erosion Corrosion of a 1.25Cr 300 # valve flange on an FCC Catalyst withdrawal line.

API510/570-Exam

Figure 4-44 – Erosion of a 9Cr-1Mo coker heater return bend.

API510/570-Exam

Figure 4-45 – Erosion-Corrosion of is ASTM A48 Class 30 Cast Iron Impeller in recycle water pump.

定义: Corrosion 腐蚀 – 化学现象Erosion 冲蚀 - 机械现象Erosion- corrosion 冲蚀-腐蚀- 化学与机械组合现象

API510/570-Exam

金属可能从表面以 (1) 溶解离子腐蚀或作为 (2) 固体机械扫冲蚀

API510/570-Exam

API510/570-Exam

API510/570-Exam

Flow DirectionFlow DirectionFlow DirectionFlow Direction

API510/570-Exam

Flow Direction

API510/570-Exam

API510/570-Exam

Flow Direction

Impingement point

API510/570-Exam

冲蚀/冲蚀-腐蚀学习重点:

a) 易感温度: 操作温度,b) 原理: 设备溶液流动(液体,气体,固体或其组合)导致机械磨损与通过保护

性氧化膜机械去除加剧表面腐蚀.c) 易感材质: 一切工程材料,d) 易感设备: ,e) API 510/570考试题.

API510/570-Exam

4.2.15 Cavitation气穴现象

4.2.15 Cavitation4.2.15.1 Description of Damage

• 当液体受压波动, 在压力的快速变化时, 小气空会在低压区域产生, 这无数小气泡形成, 瞬间在高压区域崩溃.上述的崩溃的气泡产生严重的局部冲击力,可导致金属损失的侵蚀现象, 这叫做气穴现象.

a) Cavitation is a form of erosion caused by the formation and instantaneous collapse of innumerable tiny vapor bubbles.

b) The collapsing bubbles exert severe localized impact forces that can result in metal loss referred to as cavitation damage.

c) The bubbles may contain the vapor phase of the liquid, air or other gas entrained in the liquid medium.


• Most common materials of construction including copper and brass, cast iron, carbon steel, low alloy steels, 300 Series SS, 400 Series SS and nickel base alloys.


a) In a pump, the difference between the actual pressure or head of the liquid available (measured on the suction side) and the vapor pressure of that liquid is called the Net Positive Suction Head (NPSH) available. The minimum head required to prevent cavitation with a given liquid at a given flow rate is called the net positive suction head required. Inadequate NPSH can result in cavitation.

b) Temperatures approaching the boiling point of the liquid are more likely to result in bubble formation than lower temperature operation.

c) The presence of solid or abrasive particles is not required for cavitation damage but will accelerate the damage.


a) Cavitation is most often observed in pump casings, pump impellers (low pressure side) and in piping downstream of orifices or control valves.

b) Damage can also be found in restricted-flow passages or other areas where turbulent flow is subjected to rapid pressure changes within a localized region. Examples of affected equipment include heat exchanger tubes, venturis, seals and impellers.


Cavitation damage generally looks like sharp-edged pitting but may also have a gouged appearance in rotational components. However, damage occurs only in localized low-pressure zones (see Figure 4-46, Figure 4-47 to Figure 4-49).


a) Resistance to cavitation damage in a specific environment may not be significantly improved by a material change. A mechanical modification, design or operating change is usually required.

b) Cavitation is best prevented by avoiding conditions that allow the absolute pressure to fall below the vapor pressure of the liquid or by changing the material properties.

Examples include:

1. Streamline the flow path to reduce turbulence.2. Decrease fluid velocities.3. Remove entrained air.4. Increase the suction pressure of pumps.5. Alter the fluid properties, perhaps by adding additives.6. Use hard surfacing or hardfacing.7. Use of harder and/or more corrosion resistant alloys.

c) Attack is accelerated by the mechanical disruption of protective films at the liquid-solid interface (such as a protective corrosion scale or passive films). Therefore, changing to a more corrosion resistant and/or higher hardness material may not improve cavitation resistance. Excessively hard materials may not be suitable if they lack the toughness required to withstand the high local pressures and impact (shear loads) of the collapsing bubbles.


a) Cavitating pumps may sound like pebbles are being thrashed around inside.

a) Techniques include limited monitoring of fluid properties as well as acoustic monitoring of turbulent areas to detect characteristic sound frequencies.

a) Visual examination of suspected areas, as well as external UT and RT can be used to monitor for loss in thickness.


Liquid impingement or erosion (see 4.2.14).

气穴腐蚀学习重点:

a) 易感温度: 操作温度b) 原理:当液体受压波动, 在压力的快速变化时, 小气空会在低压区域产生,

这无数小气泡形成, 瞬间在高压区域崩溃.上述的崩溃的气泡产生严重的局部冲击力,可导致金属损失的侵蚀现象, 这叫做气穴现象.

c) 易感材质: 一切工程材料,d) 易感设备:泵,限流通道或其他湍流流动设备与管道.e) 预防/缓解: 更改设计以减少湍流,提高泵的吸入压力,改变流体的性质如

通过加入添加剂, 增加材料硬度等.f) 非API 510/570考试题.

4.2.16 Mechanical Fatigue机械疲劳

API510/570-Exam

4.2.16 Mechanical Fatigue 机械疲劳4.2.16.1 Description of Damage

a) Fatigue cracking is a mechanical form of degradation that occurs when a component is exposed to cyclical stresses for an extended period, often resulting in sudden, unexpected failure. 长期的循环应力造成破坏.

b) These stresses can arise from either (1) mechanical loading or (2) thermal cycling and are typically well below the yield strength of the material. 通常低于屈服强度的机械载荷或循环热应力


• All engineering alloys are subject to fatigue cracking although the stress levels and number of cycles necessary to cause failure vary by material.

API510/570-Exam

API510/570-Exam


Geometry, stress level, number of cycles, and material properties (strength, hardness, microstructure) are the predominant factors in determining the fatigue resistance of a component.

a) Design: Fatigue cracks usually initiate on the surface at notches or stress raisers under cyclic loading. For this reason, design of a component is the most important factor in determining a component’s resistance to fatigue cracking. Several common surface features can lead to the initiation of fatigue cracks as they can act as stress concentrations. Some of these common features are:

1. Mechanical notches (sharp corners or groves);2. Key holes on drive shafts of rotating equipment;3. Weld joint, flaws and/or mismatches;4. Quench nozzle areas;5. Tool markings;6. Grinding marks;7. Lips on drilled holes;8. Thread root notches;9. Corrosion.

API510/570-Exam

b) Metallurgical Issues and Microstructure

1. For some materials such as titanium, carbon steel and low alloy steel, the number of cycles to fatigue fracture decreases with stress amplitude until an endurance limit reached. Below this stress endurance limit, fatigue cracking will not occur, regardless of the number of cycles.

2. For alloys with endurance limits, there is a correlation between Ultimate Tensile Strength (UTS) and the minimum stress amplitude necessary to initiate fatigue cracking. The ratio of endurance limit over UTS is typically between 0.4 and 0.5. Materials like austenitic stainless steels and aluminum that do not have an endurance limit will have a fatigue limit defined by the number of cycles at a given stress amplitude.

3. Inclusions found in metal can have an accelerating effect on fatigue cracking. This is of importance when dealing with older, “dirty” steels or weldments, as these often have inclusions and discontinuities that can degrade fatigue resistance.

4. Heat treatment can have a significant effect on the toughness and hence fatigue resistance of a metal. In general, finer grained microstructures tend to perform better than coarse grained. Heat treatments such as quenching and tempering, can improve fatigue resistance of carbon and low alloy steels.

For alloys with endurance limits, there is a correlation between Ultimate Tensile Strength (UTS) and the minimum stress amplitude necessary to initiate fatigue cracking. The ratio of endurance limit over UTS is typically between 0.4 and 0.5. Materials like austenitic stainless steels and aluminum that do not have an endurance limit will have a fatigue limit defined by the number of cycles at a given stress amplitude.

疲劳极限合金: 引发疲劳开裂最小应力振幅和材料抗拉强度存在相关性, 这通常在0.4和0.5UTS之间.

奥氏体不锈钢和铝材料, 没有引发疲劳开裂极限的最小应力振幅.

API510/570-Exam

API510/570-Exam

API510/570-Exam

c) Carbon Steel and Titanium: These materials exhibit an endurance limit below which fatigue cracking will not occur, regardless of the number of cycles.

d) 300 Series SS, 400 Series SS, aluminum and most other non-ferrous alloys:

1. These alloys have a fatigue characteristic that does not exhibit an endurance limit. This means that fatigue fracture can be achieved under cyclical loading eventually, regardless of stress amplitude.

2. Maximum cyclical stress amplitude is determined by relating the stress necessary to cause fracture to the desired number of cycles necessary in a component’s lifetime. This is typically 106 to 107 cycles.

API510/570-Exam


a) Thermal Cycling

1. Equipment that cycles daily in operation such as coke drums.2. Equipment that may be auxiliary or on continuous standby but sees intermittent

service such as auxiliary boiler.3. Quench nozzle connections that see significant temperature deltas during operations

such as water washing systems.

b) Mechanical Loading

1. Pressure Swing Absorbers on hydrogen purification units.2. Rotating shafts on centrifugal pumps and compressors that have stress concentrations

due to changes in radii and key ways.3. Components such as small diameter piping that may see vibration from adjacent

equipment and/or wind. For small components, resonance can also produce a cyclical load and should be taken into consideration during design and reviewed for potential problems after installation.

4. High pressure drop control valves or steam reducing stations can cause serious vibration problems in connected piping.

API510/570-Exam

a) Thermal Cycling

API510/570-Exam

Am

plitu

deb) Mechanical Loading

API510/570-Exam


a) The signature mark of a fatigue failure is a “clam shell” type fingerprint that has concentric rings called “beach marks” emanating from the crack initiation site (Figure 4-50 and Figure 4-51). This signature pattern results from the “waves” of crack propagation that occur during cycles above the threshold loading. These concentric cracks continue to propagate until the cross-sectional area is reduced to the point where failure due to overload occurs.

b) Cracks nucleating from a surface stress concentration or defect will typically result in a single “clam shell” fingerprint (Figure 4-52 to Figure 4-56).

c) Cracks resulting from cyclical overstress of a component without significant stress concentration will typically result in a fatigue failure with multiple points of nucleation and hence multiple “clam shell” fingerprints. These multiple nucleation sites are the result of microscopic yielding that occurs when the component is momentarily cycled above its yield strength.

API510/570-Exam

Figure 4-50 – Schematic of a fatigue fracture surface showing “beach marks”.

API510/570-Exam

Figure 4-51 – Compressor rod fracture surface showing “beach marks”

API510/570-Exam

Figure 4-52 – Higher magnification view of figure above showing “beach marks”.

API510/570-Exam

Figure 4-53 – Fatigue fracture surface of a carbon steel pipe.

API510/570-Exam

Figure 4-54 – Fatigue crack in a 16-inch pipe-to-elbow weld in the fill line of crude oil storage tank after 50 years in service.

API510/570-Exam

Figure 4-55 – A cross-section through the weld showing the crack location.

API510/570-Exam

Figure 4-56 – The surface of the fracture faces of the crack shown in Figure 4-54 and Figure 4-55.

API510/570-Exam

The signature mark of a fatigue failure is a “clam shell 蛤壳” type fingerprint that has concentric rings called“beach marks”emanating from the crack initiation site

API510/570-Exam

API510/570-Exam

API510/570-Exam

http://www.efunda.com/formulae/solid_mechanics/fatigue/fatigue_lowcycle.cfm

159159

530.352 Materials Selection530.352 Materials Selection530.352 Materials Selection

Lecture #23 FatigueTuesday November 8th, 2005

http://www.me.jhu.edu/hemker/MatSel/lectures/23%20Fatigue.ppt

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Failure even at low StressesFailure even at low StressesFailure even at low Stresses

Failure often occurs even when:Failure often occurs even when:appliedapplied < < fracturefracture and and appliedapplied < < yielding yielding

90% of all mechanical failures are 90% of all mechanical failures are related torelated to dynamic loading.dynamic loading.

Dynamic Loading Dynamic Loading --> Cyclic Stresses> Cyclic Stresses

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Examples of Fatigue FailuresExamples of Fatigue FailuresExamples of Fatigue Failures

Plastic Tricycle:

162162

Examples of Fatigue FailuresExamples of Fatigue FailuresExamples of Fatigue FailuresDoor Stop:

163163

Examples of Fatigue FailuresExamples of Fatigue FailuresExamples of Fatigue Failures

Railway Accidents:

Versailles 1842Versailles 1842 first fatigue problemfirst fatigue problem axial failureaxial failure

TodayToday flaws in 10% of flaws in 10% of

rails.rails.

164164

Types of FatigueTypes of FatigueTypes of Fatigue

Fatigue of uncracked componentsFatigue of uncracked components No preNo pre--cracks; initiation controlled fracturecracks; initiation controlled fracture Examples : most small components: pins, gears, Examples : most small components: pins, gears,

axles, ...axles, ... High cycle fatigueHigh cycle fatigue

fatiguefatigue < < yieldyield ; N; Nff > 10,000> 10,000

Low cycle fatigueLow cycle fatigue fatiguefatigue > > yield yield ; N; Nff < 10,000< 10,000

165165

Types of Fatigue:Types of Fatigue:Types of Fatigue:

Fatigue of cracked structures–Pre-cracks exist: propagation

controls fracture–Examples : most large components,

particularly those containing welds: bridges, airplanes, ships, pressure vessels, ...

166166

Cyclic LoadingCyclic LoadingCyclic Loading

Weight

+

-

time

167167

Basic Fatigue Terminology:Basic Fatigue Terminology:Basic Fatigue Terminology:

+

-time

mean

max

min

0

maxmin

mean maxmin

amplitudemaxmin

N = number of fatigue cycles

Nf = number of cyclesto failure

168168

High Cycle FatigueHigh Cycle FatigueHigh Cycle Fatigue

Apply controlled Apply controlled appliedapplied < ~ < ~ 22//33 yieldyield

Stress is elasticStress is elasticon gross scale.on gross scale.

Locally the metal Locally the metal deforms plasticallydeforms plastically..

50

40

30

10

0105 106 107 108 109

Nfailure

Stre

ssAl alloys

Mild SteelFatigue limit

S-N Curves

169169

Low Cycle FatigueLow Cycle FatigueLow Cycle Fatigue

Apply controlled amounts of Apply controlled amounts of totaltotal total total = = elastic elastic + + plasticplastic

Empirical Observations and RulesEmpirical Observations and Rules CoffinCoffin--Manson LawManson Law

MinerMiner’’s Rules Rule

170170

Coffin-Manson LawCoffinCoffin--Manson LawManson LawFor low cycle fatigue:

log pl

log Nfailure

y=y/E

~104

plastic Nfailure1/2 = Const.

171171

Miner’s RuleMinerMiner’’s Rules Rule

Rule of Accumulative damage:

N1 N2 N3 = 1NiNfailure @ i

Fraction of life time @ i

172172

The Fatigue ProcessThe Fatigue ProcessThe Fatigue Process Crack initiationCrack initiation

early development of damageearly development of damage Stage I crack growthStage I crack growth

deepening of initial crack on shear planesdeepening of initial crack on shear planes Stage II crack growthStage II crack growth

growth of well defined crack on planes normal growth of well defined crack on planes normal to maximum tensile stressto maximum tensile stress

Ultimate FailureUltimate Failure

173173

Crack initiationCrack initiationCrack initiation

Alternate stresses -> slip bands -> surface rumpling

Cracks start at:• Surfaces• Inclusions• Existing

cracks

174174

Crack Initiation:Crack Initiation:Crack Initiation:

175175

Crack GrowthCrack GrowthCrack Growth

Striation indicatingsteps in crack advancement.

176176

Propagation in Cracked Structures

Propagation in Cracked Propagation in Cracked StructuresStructures

ao ~ adetectible < acritical

ao -> acritical = FAILURE !!!

K = Kmax - Kmin

= (a)1/2

da = A1 Km

dNlog K

log

da/

dN

Fast

frac

ture

thre

shol

d

linear

177177

Real world comparisons:Real world comparisons:Real world comparisons:

log K

log

da/

dN

Fast

frac

ture

thre

shol

d

linear

178178

Fracture surfaces:Fracture surfaces:Fracture surfaces:

179179

Fracture Surfaces:Fracture Surfaces:Fracture Surfaces:Initiationsite

Fatigue Fatigue crackingcracking Final fracture

机械疲劳学习重点:

a) 易感温度: 操作温度,b) 原理:长期的循环应力造成破坏.c) 易感材质: 一切工程材料,d) 易感设备: 温度循环设备,机械振动设备,e) 预防/缓解: 通过设计减少振动与温度循环.f) API 510/570考试题.

API510/570-Exam

4.2.17 Vibration Induced Fatigue振动疲劳

API 570-Exam

4.2.17 Vibration-Induced Fatigue 振动引起的疲劳4.2.17.1 Description of Damage

A form of mechanical fatigue in which cracks are produced as the result of dynamic loading due to vibration, water hammer, or unstable fluid flow.


All engineering materials.


a) The amplitude and frequency of vibration as well as the fatigue resistance of the components are critical factors.振动的振幅和频率

b) There is a high likelihood of cracking when the input load is synchronous or nearly synchronizes with the natural frequency of the component. 共鸣(同步)频率

c) A lack of or excessive support or stiffening allows vibration and possible cracking problems that usually initiate at stress raisers or notches.局部应力集中或缺口

API 570-Exam


a) Socket welds and small bore piping at or near pumps and compressors that are not sufficiently gusseted.

b) Small bore bypass lines and flow loops around rotating and reciprocating equipment.

c) Small branch connections with unsupported valves or controllers.

d) Safety relief valves are subject to chatter, premature pop-off, fretting and failure to operate properly.

e) High pressure drop control valves and steam reducing stations.

f) Heat exchanger tubes may be susceptible to vortex shedding.

API 570-Exam


a) Damage is usually in the form of a crack initiating at a point of high stress or discontinuity such as a thread or weld joint (Figure 4-57 and Figure 4-58).

b) A potential warning sign of vibration damage to refractories is the visible damage resulting from the failure of the refractory and/or the anchoring system. High skin temperatures may result from refractory damage.

API 570-Exam


a) Vibration-induced fatigue can be eliminated or reduced through design and the use of supports and vibration dampening equipment. Material upgrades are not usually a solution.

b) Install gussets or stiffeners on small bore connections. Eliminate unnecessary connections and inspect field installations.

c) Vortex shedding can be minimized at the outlet of control valves and safety valves through proper side branch sizing and flow stabilization techniques.

d) Vibration effects may be shifted when a vibrating section is anchored. Special studies may be necessary before anchors or dampeners areprovided, unless the vibration is eliminated by removing the source.

API 570-Exam


a) Look for visible signs of vibration, pipe movement or water hammer.

b) Check for the audible sounds of vibration emanating from piping components such as control valves and fittings.

c) Conduct visual inspection during transient conditions (such as startups, shutdowns, upsets, etc.) for intermittent vibrating conditions.

d) Measure pipe vibrations using special monitoring equipment.

e) The use of surface inspection methods (such as PT, MT) can be effective in a focused plan.

f) Check pipe supports and spring hangers on a regular schedule.

g) Damage to insulation jacketing may indicate excessive vibration. This can result in wetting the insulation which will cause corrosion.

API 570-Exam


Mechanical fatigue (see 4.2.16) and refractory degradation (see 4.2.18).

API 570-Exam

Figure 4-57 – Vibration induced fatigue of a 1-inch socket weld flange in a thermal relief system shortly after startup.

API 570-Exam

Figure 4-58 – Cross-sectional view of the crack in the socket weld in Figure 4-57.

API 570-Exam

API 570-Exam

振动引起的疲劳学习重点:

a) 易感温度: 操作温度b) 原理:热疲劳开裂是由振动引起循环应力引起的开裂,c) 易感材质: 一切工程材料,d) 易感设备: 小口径管路,高压力差管路,e) 预防/缓解: 设计控制,振动阻尼装置,支撑,f) API 570考试题.

4.2.18 Refractory Degradation耐火垫退化

4.2.18 Refractory Degradation 耐火材料退化4.2.18.1 Description of Damage

Both thermal insulating and erosion resistant refractories are susceptible to various forms of mechanical damage (cracking, spalling and erosion) as well as corrosion due to oxidation, sulfidation and other high temperature mechanisms.


Refractory materials include insulating ceramic fibers, castables, refractory brick and plastic refractories.


a) Refractory selection, design and installation are the keys to minimizing damage.

b) Refractory lined equipment should be designed for erosion, thermal shock and thermal expansion.

c) Dry out schedules, cure times and application procedures should be in accordance with the manufacturer’s specifications and the appropriate ASTM requirements.

d) Anchor materials must be compatible with thermal coefficients of expansion of the base metal.

e) Anchors must be resistant to oxidation in high temperature services.

f) Anchors must be resistant to condensing sulfurous acids in heaters and flue gas environments.

g) Refractory type and density must be selected to resist abrasion and erosion based on service requirements.

h) Needles and other fillers must be compatible with the process environment composition and temperature.


a) Refractories are extensively used in FCC reactor regenerator vessels, piping, cyclones, slide valves and internals; in fluid cokers; in cold shell catalytic reforming reactors; and in waste heat boilers and thermal reactors in sulfur plants.

b) Boiler fire boxes and stacks which also use refractory are affected.


a) Refractory may show signs of excessive cracking, spalling or lift-off from the substrate, softening or general degradation from exposure to moisture.

b) Coke deposits may develop behind refractory and promote cracking and deterioration.

c) In erosive services, refractory may be washed away or thinned, exposing the anchoring system. (Figure 4-59)


Proper selection of refractory, anchors and fillers and their proper design andinstallation are the keys to minimizing refractory damage.


a) Conduct visual inspection during shutdowns.

b) Survey cold-wall equipment onstream using IR to monitor for hot spots to help identify refractory damage.


Oxidation (see 4.4.1), sulfidation (see 4.4.2) and flue gas dew point corrosion (see 4.3.7).

Figure 4-59 – Damaged refractory and ferrules.

耐火材料退化学习重点:

a) 易感温度: 高温b) 原理:机械或腐蚀引起退化,c) 易感材质:耐火材料,d) 易感设备:耐火材料设备,e) 预防/缓解:锚杆材料必须与基体金属的热膨胀系数相兼容,锚栓必须耐高

温氧化,f) 非API 510/570考试题.

4.2.19 Reheat Cracking再热裂纹

4.2.19 Reheat Cracking4.2.19.1 Description of Damage

由于再次受热产生的应力松弛的金属开裂Cracking of a metal due to stress relaxation during Post Weld Heat Treatment (PWHT) or in service at elevated temperatures. It is most often observed in heavy wall sections.

4.2.19.2 Affected MaterialsLow alloy steels as well as 300 Series SS and nickel base alloys such as Alloy 800H. (ferritic & Austenitic)

4.2.19.8 Related MechanismsReheat cracking has also been referred to in the literature as “stress relief cracking” and “stress relaxation cracking”.应力松弛开裂

再热裂纹

Reheat cracking occurs at elevated temperatures when creep ductility is insufficient to accommodate the strains required for the relief of applied or residual stresses. The grain size has an important influence on the high temperature ductility and on the reheat cracking susceptibility.

A large grain size result in less ductile heat affected zones, making the material more susceptible to reheat cracking.

在升高的温度下, 再热裂纹发生; 当蠕变延性不足以容纳,所需的”应用” 或”残余应力”松弛变化. 大粒径的晶粒, 焊接热影响区韧性较差，这造成焊接热影响易受再热开裂.


Important parameters include the type of material (chemical composition, impurity elements), grain size, residual stresses from fabrication (cold working, welding), section thickness (which controls restraint and stress state), notches and stress concentrators, weld metal and base metal strength, welding and heat treating conditions. From the various theories of reheat cracking for both 300 Series SS and low alloy steels, cracking features are as follows:

a) Reheat cracking requires the presence of high stresses and is therefore more likely to occur in thicker sections and higher strength materials.

b) Reheat cracking occurs at elevated temperatures when creep ductility is insufficient to accommodate the strains required for the relief of applied or residual stresses. 蠕变延性不足以适应 (1) 应用或 (2) 残余应力缓减,所需的伸张.

c) In the first half of 2008, numerous cases of reheat cracking occurred during 2 ¼ Cr-1 Mo-V reactor fabrication. The cracks were in weld metal only, transverse to the welding direction, and in only SAW welds. It was traced to a contaminant in the welding flux.

d) Reheat cracking can either occur during PWHT or in service at high temperature. In both cases, cracks are intergranular and show little or no evidence of deformation.

e) Fine intragranular precipitate particles make the grains stronger than the grain boundaries and force the creep deformation to occur at the grain boundaries.

f) Stress relief and stabilization heat treatment of 300 Series SS for maximizing chloride SCC and PTASCC resistance can cause reheat cracking problems, particularly in thicker sections.

http://www.hydrocarbonprocessing.com/Article/2764339/How-to-fabricate-reactors-for-severe-

service.html

https://etd.ohiolink.edu/ap/0?0:APPLICATION_PROCESS%3DDOWNLOAD_ET

D_SUB_DOC_ACCNUM:::F1501_ID:osu1188419315%2Cinline

http://www.staff.ncl.ac.uk/s.j.bull/mmm373/WFAULT/sld017.htm


a) Reheat cracking is most likely to occur in heavy wall vessels in areas of high restraint including nozzle welds and heavy wall piping.

b) HSLA steels are very susceptible to reheat cracking.


a) Reheat cracking is intergranular and can be surface breaking or embedded depending on the state of stress and geometry. It is most frequently observed in coarse-grained sections of a weld heat affected zone.

b) In many cases, cracks are confined to the heat-affected zone, initiate at some type of stress concentration, and may act as an initiation site for fatigue. Figure 4-60 to 4-63.

Figure 4-60 – Samples removed from a cracked 12-inch NPS 321SS elbow in hot recycle H2 line that operated at 985°F in hydrocracker.

Figure 4-61 – Crack at weld from SS321 elbow shown in the Figure 4-60.

Figure 4-62 – Cross-section through the weldment showing the crack in Figure 4-61.

Figure 4-63 –Photomicrographs of the weldment area.


a) Joint configurations in heavy wall sections should be designed to minimize restraint during welding and PWHT. Adequate preheat must also be applied.

b) The grain size has an important influence on the high temperature ductility and on the reheat cracking susceptibility. A large grain size results in less ductile heat-affected zones, making the material more susceptible to reheat cracking.

c) Metallurgical notches arising from the welding operation are frequently the cause of heat-affected zone cracking (at the boundary between the weld and the heat-affected zone).

d) In design and fabrication, it is advisable to avoid sharp changes in cross section, such as short radius fillets or undercuts that can give rise to stress concentrations. Long-seam welds are particularly susceptible to mismatch caused by fitup problems.

e) For 2 ¼ Cr-1 Mo-V SAW weld materials, prequalification screening tests for reheat cracking such as high temperature (650oC) Gleeble tensile tests should be considered.

f) For Alloy 800H, the risk of in-service cracking can be reduced by using base metal and matching weld metal with Al+Ti <0.7%.

g) For Alloy 800H which will operate >540oC, the material may need to be purchased with a thermal stabilization heat treatment, and with PWHT of welds and cold worked sections. Welds should be made with matching Alloy 800H filler material and should be stress relieved. Refer to ASME Section VIII, Div. 1 Code in UNF-56(e) for additional information.

h) For thick-wall SS piping, PWHT should be avoided whenever possible.


a) Surface cracks can be detected with UT and MT examination of carbon and low alloy steels

b) UT and PT examination can be used to detect cracks in 300 Series SS and nickel base alloys.

c) Embedded cracks can only be found through UT examination.d) Inspection for reheat cracking in 2 ¼ Cr-1 Mo-V reactors during

fabrication is typically done with TOFD or manual shear wave UT with the demonstration block having defects as small as 3 mm side drilled holes


Reheat cracking has also been referred to in the literature as “stress relief cracking” and “stress relaxation cracking”.

http://www.twi-global.com/technical-knowledge/job-knowledge/defects-

imperfections-in-welds-reheat-cracking-048/

http://www.staff.ncl.ac.uk/s.j.bull/mmm373/WFAULT/sld017.htm

再热裂纹学习重点:

a) 易感温度: 高温b) 原理:蠕变延性不足以适应 (1) 应用或 (2) 残余应力缓减,所需的伸张引

起的开裂,c) 易感材质: 铁素体,奥氏体,厚壁钢材,d) 易感设备:高温服务,厚壁设备,e) 非API 510/570考试题.

4.2.20 GOX-Enhanced Ignition & Combustion气化氧-增强燃烧

4.2.20 Gaseous Oxygen-Enhanced Ignition and Combustion气态氧增强的点火和燃烧4.2.20.1 Description of Damage

Many metals are flammable in oxygen and enriched air (>25% oxygen) services even at low pressures, whereas they are non-flammable in air. The spontaneous ignition or combustion of metallic and nonmetallic components can result in fires and explosions in certain oxygen-enriched gaseous environments if not properly designed, operated and maintained. Once ignited, metals and non-metals burn more vigorously with higher oxygen purity, pressure and temperature


a) Carbon steels and low alloy steels are flammable in low pressure oxygen, greater than about 15 psig (0.103 MPa). With special precautions, these materials are safely used in high pressure oxygen.

b) Austenitic stainless steels (300 series) have better resistance to low pressure oxygen and are generally difficult to ignite at pressures below about 200 psig (1.38 MPa).

c) Copper alloys (with >55% copper) and nickel alloys (with >50% nickel) are very fire resistant and are generally considered non-flammable. Because of their excellent oxygen “compatibility” they are often selected for impingement and turbulent services such as valves and instrumentation (Figure 4-69). Alloy 400 is highly resistant.

d) Although widely used for oxygen cylinders and in oxygen manufacturing plants, aluminum is usually avoided for flowing oxygen. If ignited it burns quickly and with a large energy release.

e) The easiest materials to ignite are plastics, rubbers, and hydrocarbon lubricants and these are minimized in oxygen systems.

f) Titanium alloys are generally avoided in oxygen and oxygen-enriched service because they have low ignition energies and release a large amount of energy during combustion. Tests indicate that titanium can sustain combustion at oxygen pressure as low as 7 kPa (1 psi) absolute. Most industry documents caution against the use of titanium in oxygen systems (References 6 and 7).

Note: These are general guidelines and should not be considered for design.


a) Many factors affect the likelihood of combustion and ignition in oxygen services including the system pressure, oxygen content of the stream, line velocity, component thickness, design and piping configuration, cleanliness and temperature.

b) The primary concern under high velocity oxygen flow conditions is the entrainment of particulate and their subsequent impingement on asurface, such as at a pipe bend. Oxygen velocities in carbon steel and stainless steel piping should comply with industry limits as shown in Reference 1. Allowable velocity is a function of pressure and flow condition (direct impingement or non-impingement).

c) The temperature of a material affects its flammability. As temperature increases, a lower amount of additional energy is required for ignition and sustained combustion. The minimum temperature at which a substance will support combustion, under a specific set of conditions is referred to as the ignition temperature. Published ignition temperatures for most alloys are near the alloy’s melting temperature. However, these are measured in non-flowing conditions. Actual systems can suffer ignition and combustion at room temperature (and lower) due to particle impact and other mechanisms.

d) System cleanliness is important for the safe operation of oxygen systems. Contamination of with metallic fines or hydrocarbons such as oils and greases during construction or maintenance activities can lead to fires during subsequent start up of the unit. These materials are easy to ignite and can lead to a large fire and breach of the system.

e) Impingement areas such as sharp elbows, tees and valves have a higher risk of ignition than straight pipe. Particles in the flowing oxygen can strike these areas and cause ignition. Operation of valves and regulators (opening / closing) cause high turbulence and impingement and only components selected and cleaned specifically for oxygen service should be used.


a) These guidelines apply to any unit that uses oxygen or enriched air for combustion or other process reasons.

b) Oxygen is sometimes used in sulfur recovery units (SRU) and fluid catalytic cracking units (FCCU), Gasification, and Partial Oxidation (POX) units. Figures 4-64 to 4-66.

c) Oxygen piping systems especially valves, regulators, and other impingement areas are potentially vulnerable. Non-metals such as those used for seats and seals, are easier to ignite than metals (Figure 4-69).


a) In some cases a small component will burn, such as a valve seat, without kindling other materials and without any outward sign of fire damage. It is noticed when the component is removed because it is not functioning properly. Figure 4-67 to 4-68.

b) Also, external heat damage (glowing pipe or heat tint) is a strong indication of an internal fire. This can be caused by accumulation of flammable debris at a low point or other location and combustion or smoldering of the debris.

c) The worst situation is when the pressure envelope is breached because of fire. Oxygen fires can cause significant burning of metal components and extensive structural damage (Figure 4-68).


Refer to industry recommended guidelines included in the references listed below. Some general considerations are as follows:

a) Oxygen fires are a sudden occurrence and not a progressive degradation or weakening of the material. Prevention is best accomplished be keeping systems clean, or cleaning them after maintenance or inspections.

b) Maintain velocity within recommended limits. If practical, avoid velocities that are nominally above 100 feet/second (30 m/sec) in gaseous oxygen.

c) Ensure that replacement components are suitable for oxygen service.

d) Oxygen systems should be thoroughly cleaned after maintenance.

e) Minimize lubricants and use only “oxygen compatible” lubricants.

f) Do not unnecessarily open oxygen systems for visual or other inspections as this could introduce contamination.

g) A thorough review is needed before modifying oxygen systems to operate at higher pressures, temperatures, or velocities.

h) Minimize sudden changes in pressure in the system. If high pressure oxygen suddenly enters a system initially at low pressure by quick operation of a valve, the “dead end” of that system experiences heating from adiabatic compression of the oxygen. Adiabatic compression heating can ignite plastics and rubbers, but will not ignite metals. Valve seats, seals, non-metallic hoses, etc can be ignited by this mechanism.

i) Do not use plastic pipe in oxygen piping systems.j) Personnel activities near oxygen piping and systems should be minimized

during start ups.


a) Most commercial oxygen is dry and non-corrosive at normal ambient temperatures. Because of the sudden catastrophic ignition of metals under certain conditions this type of damage is difficult to inspect for in advance.

b) Tell-tale signs of a minor fire such as external heat damage, or signs of malfunctioning valves or other components containing non-metallic components may be indicative of a problem.

c) Blacklights can be used to check for hydrocarbon contamination.


Not applicable.

Figure 4-64 – Thermal combustor on the front end of a reaction furnace on a sulfur recovery unit.

Figure 4-65 – Same as figure above after damage due to oxygen combustion resulting from oxygen injection into the thermal combustor on the front end of the reaction furnace.

Figure 4-66 – Same as figure above when viewed from a different angle.

Figure 4-67 – Photograph of a burned 304 SS elbow. The fire started in an upstream stainless steel wire filter (due to particle impact) and the burning filter material impacted the elbow and ignited it. Thin stainless steel components (e.g., filter) are much more flammable than thicker SS. Thin SS (<1/8”) is usually avoided in oxygen systems.

Figure 4-68 – Photograph illustrating burn through of a brass pressure gage. Brass is generally suitable for oxygen service. However, the gauge was not was not intended for oxygen service and was not “oil free”. Hydrocarbon contamination, probably from manufacture, caused the fire.

Figure 4-69 – Burn-through of a PTFE-lined stainless steel hose in high pressure gaseous oxygen (GOX) service. Grease contamination ignited and penetrated the hose.

气化氧-增强燃烧学习重点:

a) 易感温度: 操作温度b) 原理:氧气导致燃烧,c) 易感材质: 铁素体,奥氏体,其他,d) 易感设备:气态氧设备,e) 预防/缓解: 正确材料选择, 清洁度, 流速(避免冲击),外来固体,f) 非API 510/570考试题.

Api571 API571 ICP Material & Corrosion part a

Engineering

Transcript of Api571 API571 ICP Material & Corrosion part a