圆圈形运丝方式下温度影响MIG焊接头组织与断裂位置的规律

以圆圈形运丝为研究对象，利用数值模拟与试验相结合的方法研究了在MIG焊接过程中的温度场分布规律，讨论了温度峰值影响接头显微组织及断裂位置的规律.结果表明，对于圆圈形摆动工艺来说，由于熔池区内左侧的材料经历了周期性的二次加热，导致焊缝左侧及热影响区材料经历的温度峰值均高于右侧；摆动工艺的熔池区温度峰值高于不摆动工艺.与直线运丝相比较，摆动焊焊道内的等轴晶较大，而相邻焊道界面处的柱状晶较小.不同工艺下拉伸试样的断裂位置与焊缝区经历的热循环密切相关.

Effects of temperature on microstructure and fracture position of MIG welded joints using circled wire-feeding mode

Based on the circled wire-feeding mode, the temperature distribution during the MIG welding process was studied by numerical simulation and experimental investigation and the effect of the peak temperature on the microstructure and fracture position was discussed. Results showed that for the circled weaving welding process, the materials in the left side of the weld and thermo-affected zone experience higher peak temperature because the material in the left side of the molten pool underwent periodic reheating process. The temperature of the molten pool using the weaving welding process is higher than that of the linear welding process. Compared with linear wire-feeding mode, the equiaxed grains in the weld bead using the weaving welding process are larger, while the columnar grains at the interface of the adjacent weld bead are smaller. The fracture position of the tensile samples under these two processes is closely related to the heat cycle in the weld zone.