Austenitic stainless steel is a steel series obtained by adding austenite forming elements such as nickel, manganese, and nitrogen to w(Cr) such as 18% stainless steel, among which w(Cr)18%-w(Ni)8 % type is the most basic - class. The Cr-Ni-Mn or Cr-Ni-Mn-N stainless steel obtained by replacing part of the nickel with manganese or nitrogen belongs to the nickel-nickel type steel. American AI-SI300 series belongs to austenitic stainless steel. The steel type maintains the austenite structure at room temperature or high temperature, and cannot be heat-treated. Usually, it is used in a solid solution state. The stainless steel forgings have the best plasticity, toughness, and good forming performance, and also have good corrosion resistance. And antioxidant properties, can also obtain high strength through cold deformation. Therefore, austenitic stainless steels are generally used for forgings that require corrosion resistance, oxidation resistance or work at higher temperatures, have less stringent strength requirements, and are used at lower temperatures. The problem that should be noticed for this type of stainless steel is the tendency of intergranular corrosion after sensitization treatment at 600-860°C. In addition, there is also the sensitivity of stress corrosion and hydrogen embrittlement such as improper processing and use environment.
Ferritic stainless steel is a body-centered cubic (bcc) structure. Chromium is dissolved in a body-centered cubic α-Fe solid solution. The cut w (Cr) is generally in the range of 13% to 30%, and no phase change occurs. In general, it is inferior to austenitic stainless steel, but it is superior to austenitic stainless steel in stress corrosion resistance. However, due to improper control of gap elements, it can exhibit brittleness, brittleness, and high-temperature brittleness at 475°C (heating above 950°C. When advanced smelting processes are used, the mass fraction of carbon-nitrogen can be reduced below 100×10-6 to avoid the above The emergence of brittleness will, from the development trend, replace some of the austenitic steels, but for ferritic stainless steel smelted by air, when selecting the forging deformation process parameters, the above “three brittleness” and grain growth are sharp Sex must be noted.