- Sep 16, 2017 -
1.austenitic stainless steel
Austenitic stainless steel is a face centered cubic structure, which represents 304, 321 and 316 steel grades. The main features are:
Under normal heat treatment conditions, the matrix structure of steel is austenite, and in the absence of proper heat treatment or different heating conditions, a small amount of carbide and ferrite structure may exist in the austenite matrix.
Austenitic stainless steel can not change its mechanical properties by heat treatment, so it can only be strengthened by cold deformation.
By adding molybdenum, copper, silicon and other alloying elements, suitable for various conditions of use of different steel grades, such as 316L, 304Cu and so on.
Non-magnetic, good low temperature performance, easy forming and weldability are important characteristics of this kind of steel.
2.Ferritic stainless steel
Ferritic stainless steel is a body centered cubic structure, which represents 409 and 430 of steel. The corrosion resistance of stainless steel is less than that of austenitic stainless steel. The main features are:
Resistance to stress corrosion cracking is superior to austenitic stainless steel;
Strong magnetism at normal temperature;
Heat treatment does not harden, and has excellent cold workability.
3.Martensitic stainless steel
Martensitic stainless steel has martensite structure at room temperature, which represents 410 and 420 of steel. The main features are:
Martensitic stainless steel at room temperature has a strong magnetic properties, generally speaking, its corrosion resistance is not prominent, but high strength, used in high strength structural steel.
Under high temperature, there is a stable austenite structure, which is transformed into martensite phase under air cooling or oil cooling, and has complete martensitic structure at normal temperature.
4.duplex stainless steel
Medium high Cr, high N, at room temperature has austenite and ferrite mixed phase, representing the steel is 2304, 2205, 2507. The main features are:
At elevated temperatures, ferrite is the basic structure, and has a 30-50% ferrite + austenite duplex phase at room temperature.
High yield strength, super resistance to pitting corrosion and stress corrosion resistance, easy to form and weld.
5.precipitation hardening stainless steel
Precipitation hardening stainless steel according to the structure can be divided into martensite precipitation hardening stainless steel (represented by 0Crl7Ni4Cu4Nb), semi austenitic precipitation hardening stainless steel (0Crl7Ni7Al and 0Crl5Ni25Ti2MoVB) and austenite and ferrite precipitation hardening stainless steel (PH55A, B, C). This kind of material is the use of heat treatment, aging precipitation of Cu, Al, Ti, Nb and other metal compounds to improve the strength of the material. The main features are:
This type of stainless steel can be adjusted by means of heat treatment to make it easy to process and easy to shape in the process of steel forming and equipment manufacturing. Semi austenitic precipitation hardening stainless steel through martensitic transformation and precipitation hardening, austenitic and martensitic precipitation hardening stainless steel by precipitation hardening treatment, so that it has a high strength and good toughness.
The content of chromium is about 17%, plus the elements such as nickel and molybdenum. Therefore, the corrosion resistance of stainless steel is close to that of 18-8 austenitic stainless steel.