Common classification of stainless steel

Stainless steel is generally classified into three types according to metallographic structure: austenitic stainless steel, ferritic stainless steel, and martensitic stainless steel. On the basis of these three basic auspicious organizations, for the specific needs and purposes, dual phase steel, precipitation hardening stainless Steel and high alloy steel with iron content less than 50% were derived.

1. Austenitic stainless steel

The base body is mainly composed of austenite structure (CY phase) of face-centered cubic crystal structure, and is non-magnetic, mainly made of stainless steel which is strengthened by cold working (and may cause certain magnetic properties). The American Iron And Steel Association uses numbers in the 200 and 300 series, such as 304.

2. Austenite - ferrite (duplex) stainless steel

The matrix has both austenitic and ferritic two-phase structure, the content of the less phase matrix is generally greater than 15%, the magnetic is stainless steel which can be enhanced by cold working, and the 329 is a typical duplex Compared with austenitic stainless steel, duplex steel has high strength, resistance to intergranular corrosion, chloride stress corrosion resistance and pitting corrosion.

3. Ferritic stainless steel

The matrix is primarily composed of a ferrite structure (a phase) of a body-centered cubic crystal structure, is magnetic, and generally cannot be hardened by heat treatment, but cold working can make it slightly defined stainless steel. The American Iron And Steel Association is marked 430 and 446.

4. Precipitation hardening stainless steel

The Base is an austenitic or martensitic structure and can be hardened by precipitation hardening. The American Iron and Steel Association uses the 600 series of numbers, such as 630, which is 17-4PH.

In general, in addition to alloys, austenitic stainless steels are superior in corrosion resistance. In environments with low corrosivity, ferritic stainless steels can be used. In mildly corrosive environments, materials are required to be high. For strength or high hardness, martensitic stainless Steel and precipitation hardened stainless steel can be used.