MB8镁合金激光-MIG复合焊接分析

Primary study of laser-MIG hybrid welding for MB8 magnesium alloy

实现了10mm厚MB8镁合金的激光-MIG(metal inert gas)复合焊接,并对其工艺稳定性、接头形貌特征、微观组织和力学性能进行了分析.在激光电弧相互作用下,镁合金复合焊接内的MIG电弧燃烧和熔滴过渡稳定性显著提高,并获得饱满均匀的复合焊缝.在文中试验条件下,复合焊接速度比单独激光焊接高25%.因为表面凹坑缺陷的消除,复合焊接接头抗拉强度远高于激光焊接接头,达到母材的87.2%.此外,复合焊缝熔合区中心区域组织为等轴晶,靠近熔合线区域为柱状晶.在复合焊缝内,相对较低的凝固速度,上半部分宽大电弧区的晶粒尺寸明显大于下半部分细窄激光区.结果表明,激光-MIG复合焊接是MB8镁合金的有效焊接方法.

Laser-MIG hybrid welding for MB8 magnesium alloy with 10 mm thickness was carried out and the process stability,appearance of weld,microstructure and tensile strength were studied.The results demonstrate laser-MIG hybrid welding is an effective welding method for MB8 magnesium alloy.By the laser-arc interaction,the stabilities of MIG arc burning and droplet transfer are improved during hybrid welding and the obtained weld is full and even.Under the used welding parameters,hybrid welding increases the welding speed by 125 % in comparison of single laser welding.Because of the disappearance of surface pit defect,the tensile strength of hybrid weld is far higher than that of laser weld and reaches 87.2% of substrate.For the hybrid weld,the microstructure in the center of fusion zone is equiaxed grain but that nearby fusion line is columnar grain.Owing to relatively slow solidification speed,the wide upper part has obvious coarser grain size than the narrow lower part.