反应堆压力容器接管安全端焊接残余应力模拟及其焊接参数优化研究

Simulation of Welding Residual Stress at Safety End of Reactor Pressure Vessel Nozzle and Optimization of Welding Parameters

目的针对反应堆压力容器接管安全端焊接残余应力较大易导致应力腐蚀开裂的问题,探究焊接工艺参数对焊接残余应力的影响,并寻找最佳工艺参数。方法利用有限元参数化建模方法建立反应堆压力容器接管安全端的三维热-力耦合模型,模拟其焊接过程,研究焊接残余应力的变化情况。采用正交试验设计法分析了焊接电流、焊接速度及层间冷却时间对焊后最大等效应力的影响,建立了焊后最大等效应力与焊接电流、焊接速度及层间冷却时间的二次回归模型,基于该模型利用遗传算法寻优焊接参数。结果焊接残余应力峰值靠近熔合区位置,残余应力较高,超过了材料的屈服应力;各参数按对焊后等效残余应力峰值的影响由大到小的顺序依次为焊接速度、焊接电流、层间冷却时间。正交试验所得最佳工艺参数如下:焊接电流为610 A,焊接速度为20 mm/s,层间冷却时间为400 s,经遗传算法进一步优化后所得的最佳参数如下:焊接电流为610 A,焊接速度为23 mm/s,层间冷却时间为427 s。通过仿真验证遗传算法优化结果,得到焊接残余应力的峰值为373 MPa,比未优化前减小了44 MPa。结论优化后的工艺参数有效降低了焊接残余应力,提高了反应堆压力容器接管安全端服役过程中的安全性,该研究方法可为实际焊接生产提供一定的参考。

The work aims to explore the influence of welding process parameters on the welding residual stress at the safety end of reactor pressure vessel nozzle and optimize the welding process parameters,so as to solve the issue of large welding residual stress at the safety end of the reactor pressure vessel which is likely to lead to stress corrosion cracking.A three-dimensional thermal-mechanical coupling model for the safety end of the reactor pressure vessel was established to simulate the welding process and study the change of welding residual stress by finite element parametric modeling.With the orthogonal test design table,the influence degrees of welding current,welding speed and interlayer cooling time on the maximum post-weld equivalent residual stress were analyzed,and a quadratic regression model of the maximum post-weld equivalent residual stress on the welding current,welding speed and interlayer cooling time was obtained.Based on the quadratic regression model,the genetic algorithm was utilized to optimize the welding parameters.The results showed that the peak weld residual stress was close to the fusion zone.The residual stresses exceeded the yield stress of the material.The order of influence of each parameter on the peak equivalent residual stress after welding was welding speed,welding current,interlayer cooling time.The optimal process parameters obtained by the orthogonal test were as follows:welding current 610 A,welding speed 20 mm/s,interlayer cooling time 400 s.The best parameters obtained after further optimization with the genetic algorithm were as follows:welding current 610 A,welding speed 23 mm/s,and interlayer cooling time 427 s.The peak residual stress of the weld obtained from the optimization with genetic algorithm was 373 MPa,which was 44 MPa less than that before the optimization through simulation.The optimized process parameters can effectively reduce the welding residual stress,and improve the safety at the safety end of the reactor pressure vessel receiver in service.The research method can provide a certain reference for the actual welding production.