汽车用镁/钢异种金属冷金属过渡点焊工艺特性

采用冷金属过渡的方法对AZ31B变形镁合金和镀锌钢板进行搭接点焊试验,运用正交试验法优化工艺参数,同时利用光学显微镜、扫描电镜和万能拉伸试验机对焊接接头的微观组织和力学性能进行研究.结果表明,运用冷金属过渡方法能够获得成形美观和性能良好的焊接接头;工艺参数显著性顺序为镀锌钢板孔径大小、送丝速度、点焊时间;接头为典型的点熔钎焊接头,由钎焊结合区和熔焊结合区组成;接头的抗拉剪载荷可达3.12 kN,远大于相同尺寸下镁镁点焊试样的抗拉剪载荷,接头的断裂方式为剪切型断裂和撕裂型断裂.

Process characteristics of cold metal transfer spot welding for automotive dissimilar metals between magnesium and steel

The magnesium alloy AZ31B sheet and galvanized steel sheet were lapped by cold metal transfer spot welding. Using orthogonal test method to optimize process parameters and at the same time,by means of optical microscope,scanning electron microscopy and universal tensile testing machine,the microstructure and mechanical properties of welding joint were studied. The results show that satisfied weld appearance and properties can be obtained. The important sequence of process parameters are followed,size of hole on the galvanized steel sheet,wire feed speed,spot welding time. The joints are typical spot welding-brazing joint,which are composed by the brazing zone and the welding zone. The tensile shear load of joint can reach 3.12 kN,which is larger than that of Mg-Mg spot welding joints. The shear fracture and tear fracture dominate the fracture mode of the joint.