Experimental study on microstructure and kinetics during tempering of Mn-Mo-Ni nuclear power forging steel
The mechanical properties of Mn-Mo-Ni steel can be affected greatly by different tempering processes. In the present paper, scanning electronic microscopy (SEM), differential scanning calorimetry (DSC) and hardness measurements were taken to correlate property variation with evolution of microstructure during tempering. In addition, kinetic analysis based on hardness measurements was applied to isothermal tempering at temperatures in a range 600 - 660 ℃. Decomposition of retained austenite and martensitic-austenite (M-A), precipitation and coarsening of carbides within bainitic ferrite and recrystallization of bainitic ferrite are proposed as the reasons for hardness variation during tempering. According to the kinetic analysis, the tempering transformation activation energy for Mn-Mo-Ni steel isothermally tempered at such temperatures is about 101.4KJ/mol, close to the diffusion activation energy of carbon atoms in ferrite. Finally, it is noted that the considerable precipitation and coarsening of carbides within bainitic ferrite only happens at high isothermal temperatures (generally equal to or above 660 ℃). This indicates that the tempering resistance of Mn-Mo-Ni steel is excellent.
Bainitic steel Tempering Kinetics Hardness Microstructure Carbide
Mingmin WANG Lizhan HAN Jianfeng GU
Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240,P.R. China
国际会议
北京
英文
132-137
2012-10-23（万方平台首次上网日期，不代表论文的发表时间）