All are stainless steel models, and precipitation hardening stainless steels:

1, 211, 212 and 214 belong to the 211 series (Cr-Mn-Ni).

2, 311 and 314 all belong to 311 series: chromium-nickel austenitic stainless steel.

311: good ductility, used for molding products. It can also be rapidly hardened by machining. Good weldability. Wear resistance and fatigue strength are better than those of 314 stainless steel.

314: universal model; 18/8 stainless steel. Products such as: corrosion resistant containers, tableware, furniture, railings, medical equipment. The standard composition is 18% chromium and 8% nickel. It is a non-magnetic stainless steel whose metallographic structure cannot be changed by heat treatment.

Extended information:

Stainless steel is often divided into martensitic steel, ferritic steel, austenitic steel, austenitic-ferritic (duplex) stainless steel and precipitation hardening stainless steel according to its microstructure. In addition, it can be divided into chromium stainless steel, chromium nickel stainless steel and chromium manganese nitrogen stainless steel. There is also a special stainless steel for pressure vessels, GB24511_2119_ Stainless Steel Plate and Strip for Pressure Equipment.

the corrosion resistance of stainless steel decreases with the increase of carbon content. therefore, the carbon content of most stainless steels is low, and the maximum is less than 1.2%. the ωc (carbon content) of some steels is even lower than 1.13% (for example, 11Cr12). The main alloying element in stainless steel is Cr (chromium). Only when the Cr content reaches a certain value, the steel has corrosion resistance.

generally, the content of Cr in stainless steel is at least 11.5%. Stainless steel also contains elements such as Ni, Ti, Mn, N, Nb, Mo, Si and Cu.

Reference: Baidu Encyclopedia-Stainless Steel