1.Austenitic stainless steel

The matrix is mainly austenite structure (CY phase) with a face-centered cubic crystal structure. It is non-magnetic and is mainly strengthened by cold working 

(and may lead to certain magnetism). The American Iron and Steel Institute uses numbers in the 200 and 300 series, such as 304.

2. Ferritic stainless steel

The matrix is mainly made of ferrite structure (a phase) with a body-centered cubic crystal structure. It is magnetic and generally cannot be hardened by heat treatment, 

but cold working can make it slightly strengthened. The American Iron and Steel Institute is labeled 430 and 446.

3.Martensitic stainless steel

The matrix is a martensitic structure (body-centered cubic or cubic), which is magnetic and its mechanical properties can be adjusted through heat treatment. The American 

Iron and Steel Institute uses numbers 410, 420 and 440. Martensite has an austenite structure at high temperatures, and when cooled to room temperature at an appropriate 

rate, the austenite structure can transform into martensite (i.e., hardened).

4. Austenitic-ferritic (duplex) stainless steel

The matrix has both austenite and ferrite two-phase structures, of which the content of the smaller phase matrix is generally greater than 15%. It is a stainless steel that is 

magnetic and can be strengthened by cold working. 329 is a typical duplex stainless steel. Compared with austenitic stainless steel, duplex steel has high strength, and its 

resistance to intergranular corrosion, chloride stress corrosion and pitting corrosion is significantly improved.

5. Precipitation hardened stainless steel

Stainless steel whose matrix is austenite or martensite and can be hardened through precipitation hardening. The American Iron and Steel Institute uses 600 series numbers, 

such as 630, which is 17-4PH.

Generally speaking, in addition to alloys, austenitic stainless steel has excellent corrosion resistance. In less corrosive environments, ferritic stainless steel can be used. In 

mildly corrosive environments, if the material is required to have high For strength or high hardness, martensitic stainless steel and precipitation hardened stainless steel can 

be used.