Abstract: The weathering steel Q450NQR1 was welded separately by using the deep penetration GMAW and pulse MAG. The welding current, voltage and the corresponding arc image during the welding was collected. The relationship between the dynamic behavior of the welding arc and the weld formation was analyzed by processing arc image. At the same time, the influence of the different welding current and welding speed under the deep penetration GMAW on the arc behavior and the weld formation was researched. The results showed that compared with pulsed MAG, deep penetration GMAW has more concentrated arc energy, lower heat source position, increased weld penetration, and good weld geometric symmetry; during deep penetration welding, as the welding current increases and the welding speed decreases, the arc area decreases, the arc edge perimeter becomes shorter, the arc centroid position drops, and the penetration depth of the weld increases; When the welding current is 315 A and welding speed is 650 mm/min, the welding arc is the most stable, and the weld seam forming quality is also the best. The single-side welding and double-side forming ofQ450NQR1 steel sheet with 12 mm thickness is completed by the optimized welding process, the weld is well formed, and there is no softening and embrittlement in each area of the joints.

Key words: deep penetration GMAW, high speed camera, arc behavior, image processing, weld formation