How to distinguish stainless steel and stainless iron materials

austenitic stainless steel

Stainless steel with austenitic structure at room temperature. When the steel contains about 18% Cr, 8-10% Ni, and 0.1% C, it has a stable austenite structure. Austenitic chromium nickel stainless steel includes the famous 18Cr-8Ni steel and the high Cr Ni series steel developed by increasing Cr and Ni content and adding elements such as Mo, Cu, Si, Nb, Ti, etc. Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but its strength is low and cannot be strengthened through phase transformation. It can only be strengthened through cold working. If elements such as S, Ca, Se, Te are added, it has good machinability. In addition to being resistant to oxidative acid corrosion, this type of steel can also withstand corrosion from sulfuric acid, phosphoric acid, formic acid, acetic acid, urea, and other elements such as Mo and Cu. If the carbon content in this type of steel is less than 0.03% or contains Ti or Ni, its resistance to intergranular corrosion can be significantly improved. High silicon austenitic stainless steel with concentrated nitric acid has good corrosion resistance. Due to its comprehensive and excellent properties, austenitic stainless steel has been widely used in various industries.

Ferritic stainless steel

Stainless steel with a predominantly ferritic structure in use. The chromium content is between 11% and 30%, and it has a body centered cubic crystal structure. This type of steel generally does not contain nickel, and sometimes contains small amounts of elements such as Mo, Ti, Nb, etc. It has the characteristics of high thermal conductivity, low expansion coefficient, good oxidation resistance, and excellent stress corrosion resistance. It is often used to manufacture components that are resistant to atmospheric, steam, water, and oxidative acid corrosion. This type of steel has disadvantages such as poor plasticity, significantly reduced post weld plasticity and corrosion resistance, which limits its application. The application of external refining technology (AOD or VOD) can greatly reduce interstitial elements such as carbon and nitrogen, thus making this type of steel widely used.

Austenitic ferritic duplex stainless steel

It is a stainless steel with austenite and ferrite structures each accounting for about half. In the case of low C content, the Cr content is between 18% and 28%, and the Ni content is between 3% and 10%. Some steels also contain alloying elements such as Mo, Cu, Si, Nb, Ti, N, etc. This type of steel combines the characteristics of austenitic and ferritic stainless steel. Compared with ferritic stainless steel, it has higher plasticity and toughness, no room temperature brittleness, significantly improved intergranular corrosion resistance and welding performance. At the same time, it maintains the 475 ℃ brittleness and high thermal conductivity of ferritic stainless steel, and has characteristics such as superplasticity. Compared with austenitic stainless steel, it has higher strength and significantly improved resistance to intergranular corrosion and chloride stress corrosion. Dual phase stainless steel has excellent resistance to pitting corrosion and is also a nickel saving stainless steel.