How to avoid the defects in the production of MIM cemented carbide parts

Cemented carbide with high hardness, high strength, wear resistance, high temperature resistance, corrosion resistance and a series of advantages, is an indispensable part of the metal parts of the important material. The traditional production method of hard alloy parts (press forming) can only produce the products with simple shape, which limits the application range of the cemented carbide.

The production process of MIM products is: powder + binder, mixing, granulation, injection molding, skim (MIM), sintering (MIM sintering furnace), and subsequent treatment. In the production of MIM carbide parts in the process, any part of the selection of materials, improper operation of the hard alloy parts are likely to cause defects, then how to avoid this defect?

First, the powder selection process. MIM of cemented carbide powder metallurgy in addition to meet the requirements of its particle size distribution, particle size, purity of the powder to be high, cannot use folders impurities powder, if the powder is mixed with sulfur, phosphorus, silicon and other elements, sintering process in these substances will formation pore and cause of product defects.

Second, production of feed. Hard alloy powder in the process of mixing needs appropriate binder, mixing will hard alloy powder and binder are fully mixed, mixing process must be strict control the temperature, to avoid evaporation of binder and its uneven distribution, the mixed feed made from materials with good rheological properties and viscosity values, to avoid the occurrence of defects in the later part of.

Third, forming part of the green. The hard alloy parts production is also the key link to avoid the defects of products, need to pay attention to in the injection process reasonable control mold temperature, feeding rate, injection pressure, Paul pressure, pressure holding time, injection speed etc., can effectively avoid the defects of injection of the green.

Fourth, skim links. Hard alloy compact degreasing, in degreasing process, if the degreasing furnace heating speed too fast, will cause cracks in hard alloy parts, step by step heating method can be used for degreasing.

Fifth, sintering process. Because of the high density of the hard alloy and the gravity of the liquid phase sintering, the products are easy to deform. The appropriate supporting device can be used for the large size of the product can be selected as a supporting plate shrinkage of the material, in addition, it should be as much as possible to shorten the time of liquid sintering.

MIM can forming complex shape of hard alloy products, with defects in the control of problem solving, MIM technology gradually perfect, the application range of the hard alloy gradually expanded, greatly promoting the development of whole hard alloy industry.