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pearlitic steel
The alloy elements are mainly chromium and molybdenum, and the total amount is not more than 5%. In addition to pearlite and ferrite, there are also bainite. This kind of steel has good high-temperature strength and processing properties at 500-600 ℃, and its price is low. It is widely used to make heat-resistant parts below 600 ℃. Such as boiler steel pipe, turbine impeller, rotor, fastener and high pressure vessel, pipeline, etc. Typical steel grades are: 16mo, 15CrMo, 12Cr1MoV, 12Cr2MoWVTiB, 10cr2mo1, 25Cr2Mo1V, 20cr3mowv, etc.

martensitic steel
The chromium content is generally 7-13%. It has high temperature strength, oxidation resistance and water vapor corrosion resistance below 650 ℃, but its weldability is poor. 1Cr13 and 2Cr13, which contain about 12% chromium, and steel grades developed on this basis, such as 1Cr11MoV, 1cr12wmov, 2cr12wmonbvb, are usually used to make turbine blades, disks, shafts, fasteners, etc. In addition, 4Cr9Si2 and 4Cr10Si2Mo, which are used to manufacture exhaust valves of internal combustion engines, are also martensitic heat-resistant steels.

ferritic steel
It has good oxidation resistance and high temperature gas corrosion resistance, but it has low high temperature strength, high room temperature brittleness and poor weldability. Such as 1cr13sial, 1cr25si2, etc. It is generally used to make parts with low load and high temperature oxidation resistance.

austenitic steel
It contains a lot of austenite forming elements such as Ni, Mn and N. when the temperature is above 600 ℃, it has good high temperature strength and microstructure stability, and good welding performance. It is usually used as a thermal strength material working above 600 ℃. Typical steel grades include 1Cr18Ni9Ti (321), 1cr23ni13 (309), 0Cr25Ni20 (310S), 1Cr25Ni20Si2 (314), 2cr20mn9ni2si2n, 4Cr14Ni14W2Mo, etc.