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Tutorial: Engineering technology Topic: Sintered metallic materials Prepared by: Ing. Elena Nov Projekt Anglicky v odbornch pedmtech, CZ.1.07/1.3.09/04.0002 je spolufinancovn Evropskm socilnm fondem a sttnm rozpotem esk republiky.

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Sintered metallic materials

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Sintered materials Are produced from metallic powders steel / copper / tin / aluminum, which are pressed under great power into required shapes and in next process sintering are bonded into a new material with very high strength.

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Advantages of powder metallurgy: Possibility to create complicated shapes (geared wheels, shapes, parts of absorbers etc.) Possibility to make self greasing / benefit of porosity / sliding gears Dimensional accuracy gain by precision tools for pressing and calibration Complete usage of entry material (without waste) High efectivity in manufacturing of large series

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Disadvantages of sintering technology Great press force is required Press moulds are expensive Size of products is limited due to pressing force and smaller net densening inside large products Shape difficult parts with transversal holes or threads are not possible to press out.

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Technological process: 1. Production of metals powder 2. Mixing of press mixtures to achieve required chemical-physical properties of final product 3. Pressing pressed powder has geometrical shape of the final product 4. Sintering is made in an Oven with protective atmosphere at max. temp. 1140 deg. 5. Final operation depends on product applicability: - calibration - conservation - saturation - honing - machining

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Powder manufacturing Powders are produced as follows - Physical milling and crushing, is used mainly for Cu, Fe, Al, Cr, Mn - atomization of liquid metal by air or water mainly for Pb, Zn, Sn, Al, Fe - steam condensation used mainly for Zn, Cd - chemically based on ore reduction is used with Cu, Ag, Fe, Ni, Co, W, Mo, Ti.

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Powders treatment Mostly by - powder reduction after their manufacture by spraying air - powder drying off after their manufacture by spraying of water - screening and classification of powder according to size of particles - addition of other parts in accordance with production special requirements - grease addition to improve pressing

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Powder pressing Purpose is to achieve partly compact basic shape of final product before sintering. Pressures therefore move in a range of 200 to 2000 Mpa. Strait-forward pressing can be - one sided (pic. a) - both sided (pic. b) - from all sides (pic. c)

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At rolling - powder from holder entry between rolls, which press and compact it. Product are rods or strips At extrusion through calibrated opening produce semi-products of rods shape.

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Powder Sintering Sintering we understand a heat influencing on semi-product made in previous operation compacting. Sintering temperature depends on composition of coupled material. In a case of semi-product sintering made from a single material, the chosen temperature is about 80% of its melting temperature. Joining of powder particles is by diffusion.

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Sintering Due to danger of oxidation is sintering made in protective atmosphere. Calibration Sintered products have satisfactory dimensional accuracy and surface quality. At a very high accuracy requirements a high precision calibration form is used.

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What is a sintering? What steps are used for manufacturing of sintered products? How accurate are sintered products? Advantages of sintering materials? Disadvantages of sintering materials?

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Name!

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