Comparative tests of steel car body sheet welds made using CMT and MIG/MAG methods

Abstract

Results of tests on the influence of automatic welding process parameters using the cold metal transfer (CMT) method on the quality of lap joints made of 0.8 mm steel car body sheets (DC 04) were described. These joints were compared with joints executed using a traditional short arc in gas shielding (MAG). Research work included visual and metallographic inspections, microhardness measurements, and mechanical properties tests of the welded joints. It was noted that the CMT method allowed for the joining of thin workpieces at much higher velocities than previously used in arc welding in shielding gases (approximately four times faster than using MIG/MAG methods), while maintaining very good quality. Metallographic tests were also used to state the changes taking place in the joint and welded material depending on parameter changes. Additionally, attempts were made to determine a mixing factor for both upper and lower metal sheets. It was observed that increased arc length caused deeper depth of fusion of the material of the lower sheet, resulting in an incremental increase in the mixing factor.