Stainless steel is generally a general term for stainless steel and acid-resistant steel. Stainless steel refers to steel that is resistant to corrosion by weak media such as atmosphere, steam, and water, while acid-resistant steel refers to steel that is resistant to chemical corrosion media such as acid, alkali, and salt. Stainless steel has a history of more than 90 years since it came out at the beginning of the last century. The invention of stainless steel is a major achievement in the history of world metallurgy. The development of stainless steel has laid an important material and technological foundation for the development of modern industry and technological progress. There are many types of stainless steel in Heilongjiang, with different properties. It has gradually formed several categories in the development process. According to the organizational structure, it is divided into four categories: martensitic stainless steel (including precipitation hardening stainless steel), ferritic stainless steel, austenitic stainless steel and austenitic plus ferritic duplex stainless steel; according to the main chemical composition of steel Or some characteristic elements in steel are classified into chromium stainless steel, chromium nickel 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 and use of steel, it is divided into nitric acid resistance Stainless steel, sulfuric acid-resistant stainless steel, pitting-resistant stainless steel, stress-corrosion-resistant stainless steel, high-strength stainless steel, etc.; according to the functional characteristics of steel, it is divided into low-temperature stainless steel, non-magnetic stainless steel, free-cutting stainless steel, superplastic stainless steel, etc. At present, the commonly used classification method is to classify according to the characteristics of steel structure and chemical composition of steel and the combination of the two. 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: chromium stainless steel and nickel stainless steel.