1.Introduction

Powder metallurgy stainless steel is made by powder metallurgy method. It is a kind of powder metallurgy material and can be made into steel or parts. Its advantages are to reduce alloy element segregation, refine microstructure, improve performance, save raw materials, save energy consumption and reduce costs.

stainless steel powdermetallurgy related enterprises are mainly applicable to the production and research of spare parts in the automotive industry, equipment manufacturing industry, metal industry, aerospace, military industry, instruments and meters, hardware tools, electronic appliances and other fields, the production of related raw materials and auxiliary materials, and the manufacture of various powder preparation equipment and sintering equipment. Products include bearings, gears, carbide tools, molds, friction products, etc.

2.Process

The process flow of stainless steel powder metallurgy is powder preparation → forming → sintering

1. Preparation of powder: It can be water atomization, and the molten stainless steel flows out from the nozzle leak hole, blown away with high-pressure water, and solidified to obtain stainless steel powder. The bulk density of water atomized stainless steel powder is 2.5~3.2 g/cm3. It can also be gas atomized. The bulk density of the high-pressure nitrogen atomized powder is 4.8 g/cm3, and the oxygen content of the powder is less than 10-4. Spherical stainless steel powder can also be produced by rotating electrode powder making method.

2. Forming: the forming pressure is 550~830 MPa.

3. Sintering:

Since the alloy elements in stainless steel are easy to oxidize, they must be sintered in a protective atmosphere with very low oxygen content. If hydrogen or decomposed ammonia is used as the protective atmosphere, the dew point should be - 45 to - 50 ℃. Vacuum sintering can also be used, and the sintering temperature is 1120~1150 ℃. These stainless steel powder can also be put into the sheath, vacuumed and sealed, cold isostatic pressing, and then hot isostatic pressing densification into material. The process parameter is 1050 ℃, and the pressure is 2 kPa.

Compared with ordinary cast and forged stainless steel, the segregation of alloy elements in stainless steel powder metallurgy is small, the grain size is fine, the impure inclusions are small and evenly distributed, and the mechanical properties and corrosion resistance are high. In particular, the cost of high-nitrogen stainless steel produced by powder metallurgy is much lower than that of high-pressure smelting. At the same time, powder metallurgy high-nitrogen stainless steel has a series of excellent properties, and its application prospects are very broad.

Relevant metals used for stainless steel powder metallurgy mainly include 316L, 304L, H13, 17-4PH, 440CN, etc.

The physical pictures and electron microscope pictures of some metal powders are as follows (Changsha TIJO Metal Materials Co., Ltd.)

1.

Brand:17-4PH stainless steel powder

Features: high strength, high toughness, high corrosion resistance and excellent weldability

Purposes: It is used in the manufacture of shafts, 3D printing, metal injection molding, hot isostatic pressing, etc.

2.

Brand:H13 hot working die steel powder

Features: high toughness, excellent thermal cracking resistance, medium wear resistance

Purposes: thermal spraying, 3D printing, metal injection molding