The chromium content is 12% to 30%, and the body-centered cubic lattice of ferrite is used as the matrix structure of stainless steel at high temperature and normal temperature. This type of steel generally does not contain nickel, and some contain a small amount of molybdenum, titanium or niobium and other elements, and has good oxidation resistance, corrosion resistance and resistance to chloride corrosion cracking.
According to the chromium content, ferritic stainless steel can be divided into three categories: low chromium, medium chromium and high chromium. According to the purity of the steel, especially the content of carbon and nitrogen impurities, it can be divided into ordinary ferritic stainless steel and ultra-pure ferritic stainless steel. .
Ordinary ferritic stainless steel has shortcomings such as low temperature and room temperature brittleness, notch sensitivity, high intergranular corrosion tendency, and poor weldability. Although this type of steel developed earlier, its industrial application has been greatly limited. These deficiencies of ordinary ferritic stainless steel are related to the purity of the steel, especially the high content of interstitial elements such as carbon and nitrogen in the steel.
As long as the carbon and nitrogen in the steel are low enough, for example, not more than 150×10~250×10, the above disadvantages can basically be overcome. After the 1970s, due to the development of smelting technology, especially vacuum metallurgy and secondary refining process, high-purity ferritic stainless steel with carbon + nitrogen ≤ 150~250 × 10 has been produced, making this type of steel widely used in industry. .
