S11306铁素体不锈钢厚板焊后热处理特性

Post weld heat treatment characteristics of S11306 stainless steel thick plate

研究了焊接过程及两种工艺热处理后S11306铁素体不锈钢厚板的残余应力、微观组织及力学性能。盲孔法被用于表征热处理前后的焊接残余应力。双椭球热源及顺序耦合法被用于表征焊接的温度场和应力场。使用光学显微镜研究了热处理前后的微观组织演变规律。结果表明,热源模拟的焊接温度场误差可控制在10%以内,顺序耦合获得的应力结果与试验值的差值不超过23%;热处理过程能显著降低焊缝区域的峰值残余应力;820℃热处理相较770℃对焊缝周边100 mm区域的残余应力消除作用更加显著;更高的热处理温度在降低母材马氏体含量的同时,也促进了热影响区的晶粒生长,同时焊缝区下贝氏体和马氏体复合相(LB/M)的含量增加至47.6%;母材、热影响区的硬度在热处理后呈现下降趋势,而焊缝区的硬度增加了33 HV0.05。

Residual stress,microstructure and mechanical properties of S11306 ferritic stainless steel thick plates were examined after welding and two heat treatment processes.The welding residual stress was determined both before and after heat treatment by using the blind hole method.The sequential coupling method and double ellipsoidal heat source were utilized to characterize the temperature and stress fields during welding.The microstructure evolution both before and after heat treatment was studied by using optical microscope.The results show that the error of the welding temperature field simulated by the heat source can be controlled within 10%.The difference between the stress results obtained through sequential coupling and the experimental values shall not exceed 23%.The heat treatment process can significantly reduce the peak residual stress in the weld zone.Compared to 770℃,the heat treatment temperature of 820℃provides a greater residual stress-relieving impact on the 100 mm area surrounding the weld zone.The higher heat treatment temperature not only reduces the martensite content of the base metal,but also promotes the grain growth of the heat affected zone,concurrently the content of lower bainite and martensite composite phase(LB/M)in the weld zone is increased to 47.6%.The hardness values of the base metal and heat affected zone show a decreasing trend after heat treatment,while the hardness value of weld zone is increased by 33 HV0.05.