Austenitic stainless steel

Austenitic stainless steel is stainless steel with austenitic structure at room temperature. The stable austenitic structure can be obtained when Cr, Ni and C are about 18%, 8%~10% and 0.1% respectively. Austenitic chrome-nickel stainless steel includes the famous 18Cr-8Ni steel and the high Cr-Ni series steel developed on the basis of increasing Cr and Ni content and adding Mo, Cu, Si, Nb, Ti and other elements. Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but the strength is low, it is impossible to strengthen through phase transformation, can only be strengthened through cold processing, such as adding S, Ca, Se, Te and other elements, it has good machinability.

In addition to the corrosion resistance of oxidizing acid medium, this kind of steel can also resist the corrosion of sulfuric acid, phosphoric acid, formic acid, acetic acid and urea if it contains Mo, Cu and other elements. If the carbon content of such steel is less than 0.03% or contains Ti and Ni, the resistance to intergranular corrosion can be significantly improved. High silicon austenitic stainless steel has good corrosion resistance to concentrated nitric acid. Austenitic stainless steel has been widely used in all walks of life because of its comprehensive and good comprehensive properties

On the basis of the composition of 18-8 stainless steel evolution, there are mainly important developments in the following aspects:

• (1) Mo is added to improve pitting and crevice corrosion resistance;
• (2) C reduction or Ti and Nb are added to reduce intergranular corrosion tendency;
• (3) Ni and Cr are added to improve oxidation resistance and strength at high temperature;
• (4) Ni is added to improve stress corrosion resistance;
• (5) Precipitation hardening stainless steel

S and Se are added to improve machinability and component surface accuracy

• (1) Steel is extremely low carbonization (carbon ≤0.02%) and highly purified (as impurity elements sulfur, phosphorus, silicon, manganese content is very low).
• (2) Special purpose steel development: such as hot seawater with high molybdenum steel, high corrosion resistance and high strength high nitrogen steel (nitrogen content of 0.4%~0.6% or 0.8%~1.0%), stainless steel functional materials (memory materials, hydrogen storage materials, etc.).
• (3) New process development: stainless steel composite materials, amorphous stainless steel, etc.