Stainless steel with ferrite organization in the service condition. The content of chromium in 11% to 30%, with a body-centered cubic crystal structure. This kind of steel generally does not contain nickel, sometimes also contains a small amount of Mo, Ti, Nb and other elements, this kind of steel with a large thermal conductivity, small expansion coefficient, good oxidation resistance, excellent stress corrosion resistance and other characteristics, mostly used in the manufacture of atmospheric, water vapor, water and oxidizing acid corrosion parts. This type of steel has poor plasticity, plasticity and corrosion resistance after welding is significantly reduced and other disadvantages, thus limiting its application. The application of off-furnace refining technology (AOD or VOD) can make carbon, nitrogen and other interstitial elements are greatly reduced, so that this type of steel is widely used.