Stainless Steel Grade Decoding

   
    You will definitely feel confused when facing numbers such as 304, 316, and 430. In fact, they are the "identity cards" of stainless steel. The stainless steel grade is the "concentrated code" of its material, performance and applicable scenarios.
    Stainless steel can be divided into five categories according to its organizational structure: austenite, ferrite, martensite, duplex and precipitation hardening, each category corresponding to different corrosion resistance, strength and processing properties.
    Austenitic stainless steel (such as 304, 304L, 316, 316L, 201, 202, 301) has a crystal structure of γ Fe, is non-magnetic, has good corrosion resistance, and is widely used in food, medical, chemical and other fields.
    Ferritic stainless steel (such as 430, 446, 439) is mainly composed of Cr, has good magnetic properties and heat resistance, and is often used in kitchen utensils and decorative parts.
    Martensitic stainless steel (such as 410, 420, 420J1, 420J2, 431) contains a high amount of C and can be heat treated to obtain high strength, making it suitable for high-strength components such as cutting tools, pumps and valves.
    Duplex stainless steel (such as 2205, 2507) has a duplex structure of austenite + ferrite, which combines high strength and excellent corrosion resistance and is often used in marine and petrochemical equipment.
    Precipitation hardening stainless steel (such as 321, 347, 904L) adds elements such as Ti and Nb to the austenite matrix to form a precipitate phase, which improves the high-temperature strength and is suitable for high-temperature furnaces and aircraft engine components.
    In Chinese standards, commonly used grades are accompanied by corresponding chemical designations, such as 0Cr18Ni9 (equivalent to 304) and 1Cr18Ni9Ti (304Ti), to facilitate material selection and quality inspection. The main differences between grades lie in the content of alloying elements such as Cr, Ni, Mo, Mn, and C, which determine their corrosion resistance, strength, and processing properties.