AZ91D镁合金/Q345钢MIG焊对接接头组织与力学性能研究

Study on Welding Structure and Properties of MIG Butt Welded Joint of AZ91D alloy/Q345 Steel Dissimilar Metal

采用熔化极惰性气体保护电弧焊（MIG）方法对AZ91D合金/Q345钢异种金属进行了焊接,研究了焊接电流和焊接速度对接头显微组织和抗拉强度的影响。结果表明在不同的焊接电流和焊接速度下焊缝区都为α-Mg等轴晶,AZ91D侧熔合区组织为晶粒尺寸不均的α-Mg晶粒,整体晶粒尺寸较为细小,而热影响区的晶粒尺寸较为粗大。在AZ91D/Q345接头连接处形成一定厚度的过渡层。随着焊接电流的增加,焊接接头晶粒尺寸逐渐增大,抗拉强度呈现先增加而后略降低的趋势;随着焊接速度的增加,焊接接头晶粒尺寸减小,异种金属焊接接头的抗拉强度也呈现先略增加而后降低的特征。

The dissimilar metal AZ91 D alloy/Q345 steel was welded by the method of MIG welding, the effects of welding current and welding speed on the microstructure and tensile strength of the welded joint were studied. The results show that, under different welding currents and welding speeds, the weld area is α-Mg equiaxed grain. The microstructure of fusion zone at AZ91 D side is α-Mg grain with uneven grain sizes. The grain size of fusion zone is small. The grain size of heat affected zone is relatively coarser. A transition layer with a certain thickness is formed at the AZ91 D/Q345 welded joint. With the increase of welding current, the grain size of welded joint increases gradually, the tensile strength increases first and then decreases a little. With the increase of welding speed, the grain size of welded joint decreases, the tensile strength of dissimilar metal welded joint also increases a little first and then decreases.