Types of stainless steel: Stainless steel can be roughly classified by use, chemical composition and metallographic structure. Classification by use: stainless steel can be divided into four categories, which are stainless steel, acid resistant stainless steel, heat resistant stainless steel, and low temperature stainless steel.

1, stainless steel, which refers to the corrosion resistant steel in the atmosphere and weak corrosive medium.

2, acid resistant stainless steel, which refers to the corrosion resistance of steel in a variety of strong corrosive media.

3, heat-resistant stainless steel, refers to high oxidation resistance at high temperature and high enough high temperature strength of stainless steel.

4, low temperature stainless steel, is suitable for 0 degrees below the application of alloy steel, can be used below minus 196 degrees Celsius known as ultra-low temperature steel.

 

Classification by chemical composition:

1. CR series: ferrite series, Martensite system column

2. Cr-ni series: Austenitic system column, abnormal series, precipitation hardening series.

1. Austenitic stainless steel: As the name implies, it is stainless steel with austenitic structure at room temperature. The stable austenite structure was obtained when the content of Ni was 8%~10%, Cr about 18% and C about 0.1%. Austenitic stainless steel is non-magnetic and has high toughness and plasticity. 201, 202, 301, 304, 316, 309, 321 are austenitic stainless steel. Austenitic stainless steel has been widely used in all walks of life because of its comprehensive and good comprehensive properties.

2. Ferritic stainless steel: It is stainless steel mainly composed of ferritic structure in use state. With body - centered cubic crystal structure, chromium content is 11%~30%. Generally does not contain nickel, sometimes contains a small amount of Mo, Ti, Nb and other elements, with large thermal conductivity, small expansion coefficient, good oxidation resistance, excellent stress corrosion resistance, etc., used in the manufacture of water vapor resistance, water resistance and oxidation acid corrosion parts.

3. Martensitic stainless steel: through heat treatment can adjust its mechanical properties of stainless steel, colloquially, is a kind of hardened stainless steel. The typical grade is Cr13. After quenching hardness is higher, different tempering temperature has different strength and toughness combination, the standard martensitic stainless steel is: 403, 410, 414, 416, 416(Se), 420, 431, 440A, 440B and 440C type.

4. Austenitic - ferrite duplex stainless steel: austenitic and ferrite structure each about half of the stainless steel. The content of Ni is 3%-10%, and the content of Cr is 18%-28%. Some steels also contain Mo, Cu, Si, Nb, Ti, N and other alloying elements. This kind of steel has the characteristics of austenitic and ferritic stainless steel, but also maintains the 475℃ brittleness of ferritic stainless steel and high thermal conductivity, has the characteristics of superplasticity. Duplex stainless steel has excellent corrosion resistance, is a nickel stainless steel.
5 precipitation hardening stainless steel: precipitation hardening stainless steel means that different types and amounts of hardening elements are added to the chemical composition of stainless steel, and different types and amounts of carbides, nitride, carbonitride and intermetallic compounds are precipitated through the precipitation hardening process. Both improve the strength of steel and maintain enough toughness of a high strength stainless steel, referred to as PH steel. Precipitate-hardened stainless steel can be divided into martensian-type, semi-austenitic type and Austenitic type according to the metallostructure of its substrate