核压力容器用SA508Gr.4N钢组织遗传性的消除

采用可控速热处理炉对核压力容器用SA508Gr.4N钢消除组织遗传性现象进行研究。为模仿大锻件锻后不同位置晶粒尺寸差异较大现象,对试验钢进行不同温度预粗化处理。设计了A和B两种方案消除试验钢的组织遗传性,结果表明:经方案A即等温退火+亚温正火+正火处理后,得到细小且均匀的晶粒,晶粒等级由2~9级细化为7.5~8.0级,该方案可有效消除SA508Gr.4N钢的组织遗传性现象。观察了等温退火、亚温正火和高温回火后试验钢组织的变化,分析了微观组织变化对消除试验钢组织遗传性的影响。

Structure inheritance removing of SA508Gr.4N steel for nuclear reactor pressure vessels

By using heat treatment furnace,the cooling rate of which was controllable,the elimination of structural heredity for SA508Gr.4N steel was experimentally investigated.To simulate the difference of grain size among different positions of heavy forging,pre-coarsening treatment of experimental steel was carried out at different temperatures.Subsequently,two schemes named A and B were designed to remove structure heredity of SA508Gr.4N steel.The results show that after heat treatment of scheme A,consisting of isothermal annealing,inter-critical normalizing and normalizing,fine and homogenous grain can be obtained and the ASTM grain size grade transforms from 2-9 to 7.5-8.0,thus the structural heredity of SA508Gr.4N steel can be successfully eliminated.In addition,to investigate the effect of microstructure change on structural heredity removing of experimental steel,the microstructure of this steel after different heat treatment was observed.