By composition, they can be divided into Cr system (400 series), Cr-Ni system (300 series), Cr-Mn-Ni (200 series), heat-resistant chromium alloy steel (500 series) and precipitation hardening system (600 series).
200 series: chromium-manganese-nickel
201,202, etc.: manganese instead of nickel, corrosion resistance is relatively poor, widely used in China as a cheap alternative to 300 series
300 series: chromium-nickel austenitic stainless steel
301: ductility is good for molding products. Can also be mechanically processed to make it harden quickly. Weldability is good. Wear resistance and fatigue strength is better than 304 stainless steel.
302: corrosion resistance with 304, due to the relatively high carbon content and therefore better strength.
303: by adding a small amount of sulfur and phosphorus to make it easier to cut and process than 304.
304: general type; that is, 18/8 stainless steel. Products such as: corrosion-resistant containers, cutlery, furniture, railings, medical equipment. The standard composition is 18 % chromium and 8 % nickel. The standard composition is 18 % chromium and 8 % nickel. It is a non-magnetic stainless steel that can not be altered by heat treatment to change its metallurgical structure. 0Cr18Ni9 is the GB grade.
304 L: the same characteristics as 304, but with lower carbon so it is more corrosion-resistant and easy to heat-treat, but mechanically poorer. It is suitable for welding and not easy to heat-treat products.
304 N: the same characteristics as 304, is a stainless steel containing nitrogen, nitrogen is added to improve the strength of the steel.
309: better temperature resistance than 304, temperature resistance up to 980 ℃.
309 S: with a large amount of chromium, nickel, so heat resistance, oxidation resistance is good, products such as: heat exchangers, boiler components, injection engines.
310: High-temperature oxidation resistance is excellent, the maximum operating temperature of 1200 ℃.
316: after 304, the second most widely used steel, mainly used in the food industry, watch jewelry, pharmaceutical industry and surgical equipment, the addition of molybdenum to obtain a corrosion-resistant special structure. The addition of molybdenum gives it a special structure that resists corrosion, and it is also used as a "marine steel" due to its better resistance to chloride corrosion compared to 304, while SS316 is commonly used in nuclear fuel recovery devices. 18/10 grade stainless steel is usually in line with this application level as well.
316 L: Low carbon and therefore more resistant to corrosion, easy to heat treat, products such as: chemical processing equipment, nuclear power generators, refrigerant storage lees.
321: Properties similar to 304 except that the addition of titanium reduces the risk of corrosion in the welds of the material.
347: The addition of the stabilizing element niobium makes it suitable for welding of parts of aerospace appliances 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 type (Britain and the United States), usually used as automobile exhaust pipes, ferritic stainless steel (chromium steel).
410: martensitic (high-strength chromium steel), good abrasion resistance, poor corrosion resistance.
416: added sulfur to improve the processing properties of the material.
420: "Sharpening grade" martensitic steel, similar to Brinell high-chromium steel, the earliest stainless steel. Also used for surgical knives, which can be made very bright.
430: Ferritic stainless steel, decorative, e.g. for car accessories. Good molding properties, but temperature resistance and corrosion resistance to be poor.
440: high-strength cutting edge steel, slightly higher carbon content, after appropriate heat treatment can obtain high yield strength, hardness can reach 58HRC, belong to the hardest stainless steel. The most common application example is "razor blade". There are three common types: 440A, 440B, 440C, and 440F (easy-to-machine).
500 Series: Heat-resistant chrome alloy steel.
600 Series: Martensitic precipitation hardening stainless steel.