Sorting Out Stainless Steel Classification

Stainless steel is the abbreviation of stainless acid-resistant steel, air, steam, water and other weak corrosive media or stainless steel is known as stainless steel; and will be resistant to corrosion of chemical corrosive media (acids, alkalis, salts, and other chemical impregnation) corrosion of the steel is called acid-resistant steel.

Stainless steel refers to air, steam, water and other weak corrosive media and acids, alkalis, salts and other chemical corrosive media corrosion of steel, also known as stainless acid-resistant steel. In practice, often weak corrosive media corrosion-resistant steel called stainless steel, and chemical media corrosion-resistant steel called acid-resistant steel. Because of the differences in the chemical composition of the two, the former is not necessarily resistant to chemical media corrosion, while the latter are generally stainless. The corrosion resistance of stainless steel depends on the alloying elements contained in the steel.

 

Usually, according to the metallurgical organisation, the common stainless steel is divided into three categories: austenitic stainless steel, ferritic stainless steel, martensitic stainless steel. In these three categories of basic metallurgical organisation on the basis of 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-centred cubic crystal structure of austenitic organisation (CY phase) is dominated by non-magnetic, mainly through cold working to make it strengthened (and may lead to a certain degree of magnetism) of stainless steel. American Iron and Steel Institute to 200 and 300 series of numerical labels, such as 304.

2, Ferritic stainless steel. Matrix to body-centred cubic crystal structure of ferrite organization ((a phase) is dominated by magnetic, generally can not be hardened by heat treatment, but cold working can make it slightly strengthened stainless steel. American Iron and Steel Institute to 430 and 446 for the label.

3, Martensitic stainless steel. The matrix is martensitic organisation (body-centred cubic or cubic), magnetic, through heat treatment can adjust its mechanical properties of stainless steel. American Iron and Steel Institute to 410, 420, and 440 digital labelling. Martensite at high temperatures with austenitic organisation, when cooled to room temperature at an appropriate rate, the austenitic organisation can be transformed into martensite (i.e. hardened).

4, Austenitic a ferrite (duplex) type stainless steel. The matrix has both austenite and ferrite two-phase organisation, of 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 resistance to chloride stress corrosion and pitting corrosion are significantly improved.

5, Precipitation hardening stainless steel. The matrix is austenitic or martensitic organisation, and can be hardened by precipitation hardening treatment to make it hardened stainless steel. The American Iron and Steel Institute to 600 series of digital labels, such as 630, that is, 17-4PH.

In general, in addition to alloys, the corrosion resistance of austenitic stainless steel is superior, in a less corrosive environment, you can use ferritic stainless steel, in mildly corrosive environments, if the material is required to have high strength or high hardness, you can use martensitic stainless steel and precipitation hardening stainless steel.

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