Powder Metallurgy Sintering Technology


1.The method of sintering  
Performance of different products and different sintering method
(1)According to the raw materials of different classification. Sintering can be divided into unit of sintering, multiple solid phase sintering and multicomponent liquid phase sintering

Unit of sintering is the pure metal,(such as ferrite soft magnetic materials and refractory metals ) or compounds (Al2O3, B4C, BeO, MoSi2, etc.) below the melting point temperature solid phase sintering

Multiple solid phase sintering is composed of two or more of group elements system of sintering,in which low-melting components below the melting point temperature solid phase sintering. Sintered alloys often fall into this category.Such as Cu-Ni、Fe-Ni、Cu-Au、W-Mo、Ag-Au、Fe-Cu、W-Ni、Fe-C、Cu-C、Cu-W、Ag-W.Multicomponent liquid-phase sintering to exceed the melting point of low-melting components in the system temperature of sintering.Such as the W-Cu-Ni, W-Cu, WC-Co, TiC-Ni, Fe-Cu (Cu> 10%, Fe-Ni-Al, Cu-Pb, Cu-Sn, Fe-Cu (Cu <10% ), etc.

(2)Classification according to the different feeding ways.Divided into continuous sintering and intermittent sintering

Continuous sintering.
Sintering furnace with dewaxing, presintering, sintering, cooling,Sintering and sintered material continuous or smooth, segmented to complete each phase of sintering,Continuous sintering furnace high efficiency, suitable for mass production.   Commonly used feed pusher, roller-type mesh belt type, and so on.

intermittent sintering
Parts placed in the furnace is stationary, by temperature control equipment, sintering furnace for preheating, heating and cooling cycle of operations required to complete sintering process sintering material.Intermittent sintering properties of sintered materials according to the furnace to determine the appropriate system of sintering, low production efficiency, suitable for single-piece and small-batch, commonly used in Bell-type furnace for sintering furnace, box-type furnace

2.The factors affecting the quality of products sintering
Many factors influence the properties of sintered, the character of mainly powder, forming and sintering conditions.   Sintering condition factors including time and cooling rate and heating rate, temperature, pressurized sintering atmosphere and sintering conditions and so on.
(1)The sintering temperature and time
Sintering temperature and the time affects the porosity of sintered body, density, strength, and hardness.
Sintering temperature is too high and too long, will reduce product performance, or even products over burning defects; sintering temperature too low or too short , products caused by underfiring in degraded performance.
(2)sintering atmosphere
Commonly used in powder metallurgy sintering atmosphere have a reducing atmosphere, vacuum, hydrogen, etc. Sinter atmosphere directly affects the performance of sintered body. Pressure sintering in a reducing atmosphere to prevent burning loss of billet and surface oxide can be restored.Such as iron and copper-based products often used producer gas or ammonia decomposition, tungsten carbide, stainless steel with pure hydrogen.Active metal or refractory metals (such as titanium, zirconium, beryllium, tantalum), containing TiC carbide and stainless steel by vacuum sintering.Vacuum sintering can avoid the harmful ingredients in an atmosphere (H2O, O2, H2) and other adverse effects, and can also reduce the sintering temperature (General 100~150℃ can be reduced).

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