Tutorial: Engineering technology Topic: Sintered metallic materials Prepared by: Ing. Elena Nová Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/ je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

Sintered metallic materials

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.

 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

 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.

 Technological process:  1. Production of metal’s 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 deg.  5. Final operation – depends on product applicability:  - calibration - conservation - saturation - honing - machining

 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.

 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

 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)

 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 rod’s shape.

 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.

 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.

 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?

 Name!

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