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Anglicky v odbornch pedmtech"Support of teaching technical subjects in EnglishTutorial: Engineering technology

Topic: Hot forming

Prepared by: Ing. Elena Nov

Projekt Anglicky v odbornch pedmtech, CZ.1.07/1.3.09/04.0002je spolufinancovn Evropskm socilnm fondem a sttnm rozpotem esk republiky.

Hot forming

Recrystallization temperature Is a temperature at which starts regeneration of deformed grains originated at cold forming without lattice change.Division of forging technologies according to temperature is:1.Cold forging (under recrystallization temperature when temperature is under 30% under melting point of forged material)Hot forming

2. Forming is above recrystallization temperature, recrystallization speed is so high that hardening disappear already during forming or immediately after. Hot forming

Hot forming temperature is above 70% of the formed material melting point. Material is not strengthened, the actual forming require force 10x smaller than needed for cold forming. At higher temperatures is deformation accompanied by recovery and recrystallization. Hot forming

At hot forming a texture might or might not be initiated but surface is not of good quality due to scales, furthermore grain become coarser, which can influence next technological operations. Whole process is time consuming and expensive, on the other side bubbles, tears, etc. are eliminated.Hot forming

Undesired effect of Hot Forming is formation of a fibrous structure. Fibrous structure is impossible to change by heat treatment or subsequent forming. Fibrous structure influence mechanical properties and anisotropy. Is initiated by impurities on grain surface. Hot forming

Influence of grain size on cut quality:

Small grain Large grainHot forming

At recovery starts drop of internal stress. Recovery speed is dependent on temperature and time. Grain size dependence on timeHot forming

strojirenstvi.studentske.cz/2008/10/kontrola-vady-odlitk.html/www.ksp.tul.cz/cz/kpt/obsah/vyuka/skripta_tkp/sekce/01.htmUsed literature