Powder metallurgy stainless steel refers to stainless steel manufactured by powder metallurgy. The microstructure of stainless steel prepared by this method can be refined, the segregation of alloying elements can be reduced, and the properties of the material can be improved. In addition, it can also save raw materials and energy consumption to achieve low carbon, green and environmental protection.
The process of powder metallurgy stainless steel is to prepare powder – >; Forming – & gt; Sintering.
Preparation of powder is the first step in the production of stainless steel by powder metallurgy, can be water atomization, the molten stainless steel from the nozzle hole outflow, with high pressure water blowing, solidification, stainless steel powder. The bulk density of water atomized stainless steel powder is 2.5-3.2g /cm3. It can also be aerosolized. The loose density of high-pressure nitrogen atomized powder is 4.8g /cm3, and the oxygen content of powder is less than 10-4. Spheroidal stainless steel powder can also be produced by rotating electrode process.
Next comes shaping. The forming pressure is 550~830 MPa.
The next step is sintering. Because the alloy elements in stainless steel are easy to oxidize, it must be sintered in a protective atmosphere with very low oxygen content. If hydrogen or decomposed ammonia is used as a protective atmosphere, the dew point should be -45~-50℃. Vacuum sintering can also be used, sintering temperature is 1120~1150℃. These stainless steel powder can also be packed into the bag, vacuum sealing, cold isostatic pressing, and then hot isostatic pressing densification into the material, process parameters of 1050℃, pressure 2 kPa.
Compared with ordinary cast and forged stainless steel, the alloy element segregation of POWDER metallurgy stainless steel is small, the grain size is fine, the impurity inclusions are fine and evenly distributed, and the mechanical properties and corrosion resistance of powder metallurgy stainless steel are higher. In particular, the high nitrogen stainless steel produced by the powder metallurgy method is much cheaper than the high pressure smelting method. At the same time, the high nitrogen stainless steel produced by the powder metallurgy has a series of excellent properties, and the application prospect is very broad.
