Influence of Step-cooling Test on Microstructure and Mechanical Properties of 30Cr2Ni4MoV Steel for LP Rotor of Nuclear Power Plant

In order to solve the problem of long-term aging embrittlement of 30Cr2Ni4MoV steel of low pressure (LP) rotor, effect of step-cooling test on microstructure and mechanical properties of 30Cr2Ni4MoV steel for LP rotor of nuclear power plant was investigated by using chemical composition analysis and microstructure observation, tensile test, impact and hardness test at room temperature, as well as fracture appearance transition temperature (FATT) tests. Results show that tensile strength, hardness and the room-temperature impact values decrease, and the FATT rises up with the increase of grain size and coarsening of the carbide particles during step-cooling test. However, the decline of mechanical properties after step-cooling test is not obvious. It is concluded that the LP rotor with 30Cr2Ni4MoV steel used in this study is insensitive to aging embrittlement.