According to composition, stainless steel can be divided into CR system (400 Series), Cr Ni system (300 Series), Cr Mn Ni system (200 Series) and precipitation hardening system (600 Series). 200 series Cr Ni Mn austenitic stainless steel. 300 series – Cr Ni austenitic stainless steel 301 – good ductility, used for molding products. It can also be hardened rapidly by machining. Good weldability. The wear resistance and fatigue strength are better than 304 stainless steel. The corrosion resistance of 302 is the same as that of 304, and its strength is better due to its relatively high carbon content. 303 – by adding a small amount of sulfur and phosphorus, it is easier to cut than 304. 304 – 18 / 8 stainless steel. GB grade 0Cr18Ni9. 309 – has better temperature resistance than 304. 316 – the second most widely used steel after 304, which is mainly used in food industry, pharmaceutical industry and surgical equipment. Adding molybdenum element makes it obtain a special corrosion-resistant structure. Compared with 304, it has better corrosion resistance, so it is also used as “marine steel”. SS316 is usually used in nuclear fuel recovery devices. Grade 18 / 10 stainless steel generally meets this application grade. Stainless steel bucket model 321 – in addition to adding titanium element to reduce the risk of weld corrosion, other properties are similar to 304. 400 series Ferritic and martensitic stainless steels. 408 – good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni. 409 – the cheapest model (British and American), usually used as automobile exhaust pipe, belongs to ferritic stainless steel (chromium steel). 410 martensite (high strength chromium steel), good wear resistance, poor corrosion resistance.