Effect of weld line shape on laser welded joint strength of automotive high-strength steel sheets

Abstract

ABSTRACT The optimum weld line shape for the remote laser welding was investigated to improve shear strength and peel strength of the lap joints of 980 and 1180 MPa grade automotive high-tensile strength steel sheets. Lap joints were prepared with two kinds of weld line shapes that were straight line and circle. These lap joints were exposed to three different tensile tests of tensile shear test, cross tension test and L-form tension test. In tensile shear test, weld line shapes did not affect on tensile shear strength (TSS), and TSS was proportional to weld line length. In cross tension test, weld line shapes much affected on cross tension strength (CTS). CTS of the circle weld line shape joints was much higher than that of the straight weld line shape joints. In L-form tension test, the weld line shapes also much affected on L-form tension strength (LTS). LTS of continuous straight line weld joints was much higher than that of circle shape weld joints. The factors which controlled TSS, CTS and LTS were discussed by conducting FEA of the tensile tests from a viewpoint of local stress concentration considering the loading types of shear stress and tensile stress.