AZ31B镁合金搅拌摩擦焊焊接工艺研究

采用搅拌摩擦焊对AZ31B镁合金板材进行了焊接试验，研究了搅拌头旋转速度、焊接速度和搅拌头轴肩下压量对焊接接头成形质量的影响。结果表明，搅拌头转速过快或焊接速度过慢时，焊缝会出现局部过热甚至熔化现象；反之，当搅拌头转速不够或焊接速度过快时，材料不能充分流动，会形成隧道型缺陷或表面沟槽。当搅拌头轴肩下压量过小时，焊缝内部组织疏松或出现孔洞、隧道型缺陷，焊缝表面出现沟槽，甚至使焊缝金属液外溢；搅拌头轴肩下压量过大，会造成摩擦力及搅拌头前移阻力增大、焊缝凹陷及出现飞边。当搅拌头转速为1200～1500r／min、焊速为30～60mm／min，搅拌头轴肩下压量为1．5～2．0mm时，可得表面成形良好、内部无孔洞和隧道的焊缝。

Research on the Welding Process of Friction Stir Welding for AZ31B Magnesium Alloy Plates

In this paper, the welding experiment on AZ31B magnesium alloy sheet was performed with the method of friction stir welding. The effects of the rotation speed of the stir head, the welding speed and the pressing distance of the stir head axial shoulder on the processing quality of the welded joint were investigated. The results show that if the rotation speed of the stir head was too fast or the welding speed was too slow, the local overheating and even fusion of the welded joint could happen. In contrast, if the rotation speed of the stir head was not enough or the welding speed was too fast, the material could not fully flow, and these result in the formation of the tunnel type defects or the grooves on the surface. And when the pressing distance of the axial shoulder was too small, the internal structures of the welded joint were not compact or the holes and tunnel type defects maybe appear, meanwhile the grooves on the surface of the welded joint appeared, and even the weld metal could overflow. When the pressing distanee of the axial shoulder was excessive, the friction force and the resistance of the stir head to move forward increased, and defects on the welding zone and the fins could appear. When the rotation speed of the stir head was between 1 200 r/min and 1 500 r/min, the welding speed was between 30 mm/min and 60 mm/min and the pressing distance of the axial shoulder was between 1.5mm and 2.0mm, the welding zone with excellent surface quality and no internal holes and tunnels could be obtained.