核电阀门用不锈钢热变形行为研究及应用

Research and application on thermal deformation behavior for stainless steel of nuclear power valve

针对大型特厚F316H不锈钢阀门锻件易出现粗晶、混晶和探伤无底波等难题,对其高温下的流变行为进行了研究,以探索最佳的热加工变形工艺参数来指导实际生产应用。采用Gleeble-1500D热模拟试验机,在应变速率为0.001~1 s^(-1)、变形温度为950~1250℃条件下开展了热压缩变形试验。基于Arrhenius模型,建立了高温流变应力本构方程,并计算得到热变形激活能为393.857 kJ·mol^(-1)。基于DMM动态材料模型,建立了应变量为0.8的热加工图,在变形温度为1100~1150℃、应变速率为0.005~0.01 s^(-1)时,功率耗散因子达到峰值,结合微观金相分析,该变形条件下晶粒发生了充分的动态再结晶,可作为热加工的主加工区域。结合热加工图,设计了核电不锈钢阀体锻件(规格为12寸)的锻造工艺,并经生产验证得到了晶粒度、无损探伤和力学性能优异的锻件。

For the problems that coarse grains,mixed grains and without bottom wave in detection of large extra-thick F316H stainless steel valve forgings,the thermal rheological behavior at high temperature was studied to explore the best thermal working process parameters so as to guide practical production and application,and the thermal compression deformation tests were carried out by the thermal simulation tester Gleeble-1500D under the conditions of the strain rates of 0.001^(-1) s^(-1) and the deformation temperatures of 950-1250℃.Then,the constitutive equation of high temperature rheological stress was established based on the Arrhenius model,and the thermal deformation activation energy was calculated to be 393.857 kJ·mol^(-1).Furthermore,the thermal processing map with the strain of 0.8 was established based on the DMM dynamic material model,and when the deformation temperature was 1100-1150℃and the strain rate was 0.005-0.01 s^(-1),the power dissipation factor reached the peak value.Combined with microscopic metallographic analysis,the grains within this range underwent sufficient dynamic recrystallization,which could be used as the main processing area of thermal working.Finally,combined with the thermal processing map,the forging process of nuclear power stainless steel valve body forgings(12 inches in size)was designed,and the forgings with excellent grain size,non-destructive flaw detection and mechanical properties could be obtained through the production verification.