Stainless steel is generally a general term for stainless steel and acid resistant steel. Stainless steel is resistant to atmospheric, steam and water and other weak media corrosion of steel, and acid-resistant steel is resistant to acid, alkali, salt and other chemical corrosion medium corrosion of steel. Stainless steel since the beginning of the last century, to now has 90 years of history. The invention of stainless steel is a major achievement in the history of metallurgy in the world. The development of stainless steel has laid an important material and technical foundation for the development of modern industry and scientific and technological progress. Heilongjiang stainless steel a lot of different properties, it is in the development process gradually formed several categories. According to the organizational structure, divided into martensitic stainless steel (including precipitation hardening stainless steel), ferritic stainless steel, austenitic stainless steel and austenitic ferritic two-phase stainless steel and other four categories; according to the main chemical composition of steel Stainless steel, chromium-nickel-molybdenum stainless steel, low-carbon stainless steel, high-molybdenum stainless steel, high purity stainless steel, etc .; according to the performance characteristics of steel and use classification, divided into nitric acid resistant to nitric acid Stainless steel, resistant to sulfuric acid stainless steel, resistant to pitting corrosion stainless steel, stress-resistant stainless steel, high strength stainless steel, etc .; according to the functional characteristics of steel classification, divided into low temperature stainless steel, non-magnetic stainless steel, easy cutting stainless steel, superplastic stainless steel. At present, the commonly used classification method is classified according to the structural characteristics of steel and the chemical composition of steel and the combination of the two methods. Generally divided into martensitic stainless steel, ferritic stainless steel, austenitic stainless steel, duplex stainless steel and precipitation hardening stainless steel, etc., or divided into two categories of chromium stainless steel and stainless steel.