Explanation

After heat treatment, the matrix structure is mainly martensitic heat resistant steel. The high-temperature creep strength of quenching martensite structure is low, so tempering shall be carried out at a temperature 50-100 ℃ higher than the service temperature, so that a certain amount of fine and dispersed carbide particles that are stable at high temperature can be precipitated to improve the high-temperature strength. This type of steel is cheaper than austenitic heat-resistant steel and has a smaller coefficient of thermal expansion. However, its oxidation resistance and high temperature strength will be significantly reduced when used at temperatures above 650 ° C, so its use temperature is generally limited to below 650 ° C. Mainly used for steam turbine blades and nozzles, engine valves, high-temperature bolts, etc.

Classification