All are stainless steel models, precipitation hardening stainless steel:
1, 201, 202, 204 belong to the same 200 series (chromium - manganese - nickel).
2, 301 and 304 both belong to the 300 series: chromium - nickel austenitic stainless steel.
301: good ductility, used for molding products. It can also be hardened rapidly by mechanical processing. Weldability is good. Wear resistance and fatigue strength is better than 304 stainless steel.
304: General-purpose 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. It is a non-magnetic stainless steel that cannot be changed by heat treatment to change its metallurgical structure.
Expanded Information:
Stainless steel is often divided into: martensitic steel, ferrite steel, austenitic steel, austenitic - ferrite (duplex) stainless steel and precipitation hardening stainless steel and so on according to the state of the organization. In addition, according to the composition can be divided into: chromium stainless steel, chromium-nickel stainless steel and chromium-manganese-nitrogen stainless steel. There are also used for pressure vessels with special stainless steel "GB24511_2009_Stainless Steel Plate and Strip for Pressurized Equipment".
The corrosion resistance of stainless steel decreases with the increase of carbon content, therefore, most of the stainless steel carbon content is low, the maximum is not more than 1.2%, and some of the steel ωc (carbon content) is even less than 0.03% (such as 00Cr12). The main alloying element in stainless steel is Cr (chromium), only when the Cr content reaches a certain value, the steel has corrosion resistance.
Stainless steel general Cr (chromium) content of at least 10.5%. Stainless steel also contains Ni, Ti, Mn, N, Nb, Mo, Si, Cu and other elements.
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