Specification of professional terms for stainless steel

According to use, there are nitric acid resistance stainless steel, sulfuric acid resistance stainless steel, seawater resistance stainless steel and so on. According to corrosion resistance type, it can be divided into pitting resistance stainless steel, stress corrosion resistance stainless steel, intergranular corrosion resistance stainless steel and so on. According to the functional characteristics of the classification can be divided into non-magnetic stainless steel, free cutting stainless steel, low temperature stainless steel, high strength stainless steel and so on. Stainless steel has been widely used in heavy industry, light industry, household goods industry and building decoration industry because of its excellent corrosion resistance, formability, compatibility and strength and toughness in a wide temperature range.

Austenitic stainless steel

Stainless steel with austenitic structure at normal temperature. The stable austenitic structure is obtained when Cr, Ni and C are about 18%, 8%~10% and 0.1%, respectively. Austenitic chromium-nickel stainless steel includes the famous 18CR-8Ni steel and the high Cr-Ni series steel developed by adding elements such as Mo, Cu, Si, Nb, Ti and so on. Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but the strength is low, it can not be strengthened by phase transformation, only by cold working. Such as adding S, Ca, Se, Te and other elements, it has good machinability. In addition to the corrosion resistance of oxidizing acid medium, if the steel contains Mo, Cu and other elements, it can also resist sulfuric acid, phosphoric acid, formic acid, acetic acid, urea and other corrosion. If the carbon content of these steels is less than 0.03% or containing Ti and Ni, the intergranular corrosion resistance can be significantly improved. High silicon austenitic stainless steel concentrated nitric acid has good corrosion resistance. Because of its comprehensive and good comprehensive properties, austenitic stainless steel has been widely used in all walks of life.

Ferritic stainless steel

In the use of the state of the ferrite structure of stainless steel. It has a body-centered cubic crystal structure with 11%~30% chromium content. This kind of steel generally does not contain nickel, sometimes also contains a small amount of Mn, Ti, Nb and other elements, this kind of steel with high thermal conductivity, small expansion coefficient, good oxidation resistance, excellent stress corrosion resistance and other characteristics, mostly used in the manufacture of atmospheric, water vapor, water and oxidizing acid corrosion parts. The defects of this kind of steel, such as poor plasticity, reduced plasticity and corrosion resistance after welding, restrict its application. The application of AOD or VOD technology can greatly reduce the gap elements such as carbon and nitrogen, so this kind of steel has been widely used.

Austenite – ferrite duplex stainless steel

It is a stainless steel with about half austenite and half ferrite structure. When the content of C is low, the content of Cr is 18%~28%, and the content of Ni is 3%~10%. Some steels also contain Mo, Cu, Si, Nb, Ti, N and other alloying elements. This kind of steel has the characteristics of austenite and ferritic stainless steel, compared with ferritic, higher plasticity, toughness, no room temperature brittleness, intergranular corrosion resistance and welding performance are significantly improved, but also maintain the 475℃ brittleness of ferritic stainless steel and high thermal conductivity, with superplasticity and other characteristics. Compared with austenitic stainless steel, its strength is high and its resistance to intergranular corrosion and chloride stress corrosion is obviously improved. Dual phase stainless steel has excellent corrosion resistance and is also a nickel saving stainless steel.

Martensitic stainless steel

Stainless steel whose mechanical properties can be adjusted by heat treatment is generally said to be a kind of hardened stainless steel. Typical brand is Cr13 type, such as 2Cr13, 3Cr13, 4Cr13, etc. It has high hardness after quenching, and has different combination of strength and toughness at different quenching temperatures. It is mainly used for steam turbine blades, tableware and surgical instruments. According to the difference of chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chrome-nickel steel. According to the different structure and strengthening mechanism, it can also be divided into martensitic stainless steel, martensitic and semi-austenitic (or semi-martensitic) precipitation hardening stainless steel and maraging stainless steel. 


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