S 355J 2W+N激光-电弧复合焊接头微观组织及疲劳性能研究

Study on microstructure and fatigue of laser-arc hybrid welding for S355J2W+N

采用MAG电弧与激光复合热源对6 mm钝边、30°坡口的对接接头进行焊接,观察激光-电弧复合焊焊接接头的焊缝区、粗晶区、重结晶区、不完全重结晶区的微观组织,并分析其各区域特点。根据复合热源特点将焊接接头上部称为电弧区,下部称为激光区,并结合接头的多次热循环,阐述焊缝下部激光区因柱状晶对生生长导致焊缝中心位置成为整个焊接接头薄弱区域的原因。采用130 MPa、330 MPa、340 MPa、350 MPa、360 MPa、370 MPa六种应力级别进行试验,形成S-N曲线,并通过疲劳试验数据、结合电镜下疲劳断口的微观形貌,分析裂纹扩展过程中各个阶段形貌及裂纹源出现的原因。

The butt joints with 6 mm edge and 30°groove were welded by arc and laser hybrid heat source,and the microstructure of the weld zone,coarse crystal zone,recrystallization zone and incomplete recrystallization zone of the laser-arc hybrid welding joint were observed,and the characteristics of each zone were analyzed. According to the characteristics of hybrid heat source,the upper part of the joint is called the arc zone,and the lower part is called the laser zone. The stress levels of 130 MPa、330 MPa、340 MPa、350 MPa、360 MPa and370 MPa were used in the test to form the S-N curve and analyze the crack morphology and the cause of crack source at various stages during the crack propagation process by combining the fatigue test data and the microscopic morphology of the fatigue under the electron microscope.