According to the composition, it can be divided into Cr series (400 series), Cr-Ni series (300 series), Cr-Mn-Ni (200 series), heat-resistant chromium alloy steel (500 series) and precipitation hardening series (600 series). 200 series: Chromium-Manganese-Ni 201, 202, etc.: Substituting manganese for nickel, poor corrosion resistance, widely used as a cheap substitute for 300 series in China 300 series: Chromium-nickel austenitic stainless steel 301: good ductility, used for Molded products. It can also be hardened by mechanical processing. Good weldability. Wear resistance and fatigue strength are better than 304 stainless steel. 302: The corrosion resistance is the same as 304, but the strength is better due to the relatively higher carbon content. 303: By adding a small amount of sulfur and phosphorus, it is easier to cut than 304. 304: Universal model; i.e. 18/8 stainless steel. Products such as: corrosion-resistant containers, tableware, furniture, railings, and medical equipment. The standard composition is 18% chromium plus 8% nickel. It is a non-magnetic stainless steel whose metallographic structure cannot be changed by heat treatment. The GB grade is 06Cr19Ni10. 304 L: The same characteristics as 304, but low carbon, so it is more corrosion-resistant and easy to heat treat, but has poor mechanical properties. It is suitable for welding and products that are not easy to heat treat. 304 N: It has the same characteristics as 304. It is a nitrogen-containing stainless steel. Nitrogen is added to improve the strength of the steel. 309: It has better temperature resistance than 304, with a temperature resistance of up to 980°C. 309 S: Contains a large amount of chromium and nickel, so it has good heat resistance and oxidation resistance. Products such as: heat exchangers, boiler components, and jet engines. 310: Excellent high temperature oxidation resistance, maximum use temperature 1200℃. 316: After 304, it is the second most widely used steel type. It is mainly used in the food industry, watch jewelry, pharmaceutical industry and surgical equipment. The addition of molybdenum element gives it a special corrosion-resistant structure. Because it has better resistance to chloride corrosion than 304, it is also used as "marine steel". SS316 is usually used in nuclear fuel recovery devices. Grade 18/10 stainless steel is also generally qualified for this application grade. 316 L: Low carbon, so it is more corrosion-resistant and easy to heat treat. Products such as: chemical processing equipment, nuclear power generators, and refrigerant storage tanks. 321: Except for the addition of titanium, which reduces the risk of material weld corrosion, other properties are similar to 304. 347: Adding the stabilizing element niobium, suitable for welding aircraft parts and chemical equipment. 400 series: ferritic and martensitic stainless steel, no manganese, can replace 304 stainless steel to a certain extent. 408: good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni. 409: The cheapest model (British and American), commonly used as automobile exhaust pipes, ferritic stainless steel (chromium steel). 410: Martensite (high-strength chromium steel), good wear resistance, poor corrosion resistance. 416: The addition of sulfur improves the material's processing properties. 420: "Cutting tool grade" martensitic steel, similar to Brinell high chromium steel, the earliest stainless steel. Also used in surgical knives, which can be made very shiny. 430: Ferritic stainless steel, used for decoration, such as car accessories. Good formability, but poor temperature resistance and corrosion resistance. 440: High-strength cutting tool steel with slightly higher carbon content. After appropriate heat treatment, it can obtain a higher yield strength. The hardness can reach 58HRC, which is among the hardest stainless steels. The most common application example is "razor blades". There are three commonly used models: 440A, 440B, 440C, and 440F (easy-to-process type). 500 Series: Heat-resistant chromium alloy steel. 600 Series: Martensitic precipitation hardening stainless steel.