The identification of these numbers indicates the type of stainless steel: precipitation hardening stainless steel with very good forming properties and good weldability for use as an ultra-high strength material in the nuclear, aviation and aerospace industries. 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) by composition, as follows.
200 series: Cr-Mn-Ni
201 stainless steel sheet, 202 stainless steel plate, etc.: manganese instead of nickel, corrosion resistance is relatively poor, widely used in China as a cheap alternative to the 300 series
300 series: chromium-nickel austenitic stainless steel
301 stainless steel sheet,: good ductility, used for forming products. Can also be rapidly hardened by mechanical processing. Good weldability. Wear resistance and fatigue strength are better than 304 stainless steel.
302 stainless steel plate,: same corrosion resistance as 304, better strength due to relatively high carbon content.
303 stainless steel plate,: easier to machine than 304 by adding small amounts of sulphur and phosphorus.
304 stainless steel sheet,: common type; i.e. 18/8 stainless steel. Products such as: corrosion resistant containers, tableware, furniture, railings, medical equipment. The standard composition is 18% chromium plus 8% nickel. The GB grade is 0Cr18Ni9.
304 stainless steel plate, L: the same characteristics as 304, but low carbon, so more corrosion-resistant, easy to heat treatment, but mechanical poorer for welding and not easy to heat treatment of products.
304N stainless steel plate,: the same characteristics as 304, is a stainless steel containing nitrogen, nitrogen is added to improve the strength of the steel.
309 stainless steel plate,: better temperature resistance than 304, temperature resistance up to 980 ℃.
309S stainless steel plate,: with more chromium, nickel, so heat resistance, oxidation resistance is good, products such as: heat exchangers, boiler components, jet engines.
310 stainless steel plate,: excellent high temperature oxidation resistance, maximum use temperature 1200 ℃.
316 stainless steel plate,: after 304, the second most widely used steel grade, mainly used in the food industry, watches and jewelry, pharmaceutical industry and surgical equipment, the addition of molybdenum to make it obtain a special structure to resist corrosion. It is also used as a ‘marine steel’ due to its better resistance to chloride corrosion than 304, and SS316 is commonly used in nuclear fuel recovery installations. 18/10 grade stainless steel is also commonly used in this application class.
316L stainless steel sheet,: low carbon and therefore more corrosion resistant, easy to heat treat, products such as: chemical processing equipment, nuclear power generators, refrigerant storage.
321 stainless steel plate,: similar properties to 304 except that the addition of titanium reduces the risk of corrosion in the material’s welds.
347 stainless steel plate,: with the addition of the stabilising element niobium, suitable for welding aerospace components and chemical equipment.
400 series: ferritic and martensitic stainless steel, without manganese, to a certain extent an alternative to 304 stainless steel
408 stainless steel plate,: good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni.
409 stainless steel plate,: cheapest type (British and American), usually used for car exhausts, ferritic stainless steel (chromium steel).
410 stainless steel plate,: martensitic (high strength chromium steel), good wear resistance, poor corrosion resistance.
416 stainless steel plate,: the addition of sulphur improves the processing properties of the material.
420 stainless steel plate,: “Edge grade” martensitic steel, similar to Brinell high chromium steel, the earliest stainless steel. Also used for surgical knives and can be made very bright.
430 stainless steel plate,: ferritic stainless steel, used for decorative purposes, e.g. for car accessories. Good formability, but less resistant to temperature and corrosion.
440 stainless steel plate,: high strength cutting tool steel, slightly higher carbon content, after appropriate heat treatment can obtain high yield strength, hardness can reach 58 HRC, among the hardest stainless steels. The most common application example is in “razor blades”. There are three common types: 440A, 440B, 440C and also 440F (easy to machine).