Abstract
The change in arc sound with burn through in MAG welding was measured, being related with the welding current. Also, we observed the change in arc morphology with the burn through by a CCD camera. The welding current was 300 A and the welding speed was 5 mm/s, that is, the welding was carried out only in the spray transfer region. We made holes in the workpiece with diameters of 4-9 mm in advance of welding and intentionally produced the burn through.
Two types of burn through were observed. One of them was the stagnation type in which molten metal temporally stands on the hole before the burn through. In the other, the molten metal does not stagnate. In the stagnation type, the arc sound instantly becomes low immediately before the burn through and increases suddenly at the same time when the burn through occurs.
