熔滴冲击方向对焊缝质量的影响

Effect of the Direction of Droplet Impingement on the Bead Quality

为探究熔滴冲击方向对焊缝飞溅、焊缝轮廓、显微组织及显微硬度等的影响,采用脉冲型熔化极气体保护焊工艺,通过倾斜焊枪在6061铝合金薄板上开展了堆焊实验.结果表明:当焊枪倾斜时,焊接飞溅产生在与焊枪倾斜的同侧,且飞溅量显著增加;熔滴冲击能够细化焊缝下部的晶粒.以熔滴向右冲击进入熔池为例,焊缝上部因受非对称熔池驱动力的作用,最高点与焊缝下部中心线偏离量达焊缝最大宽度的20.1%,焊缝右侧热影响区及显微硬度分布区间均显著大于左侧;气孔和裂纹分别大量分布在焊缝的左、右两侧,这与焊枪倾斜时熔滴驱动液态金属在熔池内的流动形式相关,熔滴冲击决定的流体流动抑制了左侧气孔的逃逸,同时促进了右侧裂纹的出现.

Bead-on-plate welding was conducted on a 6061 aluminum alloy sheet by pulsed gas metal arc welding (P-GMAW) with welding torch inclined in transverse plate, in order to investigate the effect of droplet impingement direction on spatters, profile of welding pool, microstructure, porosities and cracks. Results show that when the torch is inclined, the spatter is dramatically increased and is on the same side with the inclined torch. Meanwhile, the grains can be refined by the effect of droplet impingement. Taking the welding torch inclined to right-hand as an example, because of an asymmetric driving forces within the molten pool, the highest point of the bead does not coincide with the center line of the lower penetration;the biggest deviation from the bottom center line is 20.1% of the maximum bead width. Heat affected zone and the micro-hardness zone are wider on the right side that the left. Porosity and crack distribute separately on the two sides of the bead, respectively. Most pores are formed and trapped on the left side, while a substantial number of cracks emerge on the right side. This distribution of porosity and crack is attributed to the molten metal flow pattern which is driven by droplet impingement. The molten metal flow prevents the air hole from escaping on the left side,but facilitates the cracks to appear on the right side.