How to choose stainless steel- Common classification
How to choose stainless steel- The most complete knowledge of stainless steel of 201、202、301、302、304 !
Stainless steel is one of the most common steel materials contacted in precision parts manufacturing. So, knowledge of stainless steel helps to help people better grasp how to choose stainless steel.
Common classification
Common stainless steels are usually classified into three categories according to their metallurgical organization: austenitic stainless steels, ferritic stainless steels, and martensitic stainless steels. In these three categories of basic metallurgical organization, based on specific needs and purposes, and derived from the duplex steel, precipitation hardening stainless steel and high alloy steel containing less than 50% iron.
1, austenitic stainless steel.
The matrix to face-centered cubic crystal structure of austenitic organization (CY phase) is dominant, non-magnetic. Mainly through cold working to make it strengthened (and may lead to a certain degree of magnetism). The American Iron and Steel Institute labels them with numbers from the 200 and 300 series, such as 304.
2. Ferrite stainless steel.
The matrix to body-centered cubic crystal structure of ferrite organization ((A phase) is dominant, magnetic. Generally can not be hardened by heat treatment, but cold working can make it slightly strengthened. American Iron and Steel Institute to 430 and 446 for the label.
3, martensitic stainless steel.
The matrix is martensitic organization (body-centered cubic or cubic), magnetic. Through heat treatment can adjust its mechanical properties. American Iron and Steel Institute to 410, 420 and 440 digital labeling. Martensite at high temperatures with austenitic organization, when cooled to room temperature at an appropriate rate, the austenitic organization can be transformed into martensite (i.e. hardened).
4, austenitic – ferritic (duplex) type stainless steel.
The matrix has both austenitic and ferrite two-phase organization, in which the content of the lesser phase matrix is generally greater than 15%, magnetic, can be strengthened by cold working stainless steel, 329 is a typical duplex stainless steel. Compared with austenitic stainless steel, duplex steel high strength, resistance to intergranular corrosion and chloride stress corrosion and pitting corrosion are significantly improved.
5, precipitation hardening stainless steel.
The matrix is austenitic or martensitic organization, which can be hardened by precipitation hardening treatment. American Iron and Steel Institute to 600 series of digital labeling, such as 630, that is, 17-4PH.
In general, in addition to alloys, the corrosion resistance of austenitic stainless steel is superior, in less corrosive environments, ferritic stainless steel can be used, in mildly corrosive environments, if the material is required to have high strength or high hardness, martensitic stainless steel and precipitation hardening stainless steel can be used.