Analysis of the Low Cycle Fatigue Behavior of DP980 Steel Gas Metal Arc Welded Joints

Dual phase (DP) steels have high strength, while maintaining outstanding elongation capacities. This is possible using a well-controlled thermomechanical process that produces perfect combination in the DP microstructures. However, automotive makers are required to weld steels, which generates soft zone microstructure. In this work, 1.6 mm-thick DP980 steel sheets were welded by gas metal arc welding analyze response of cyclic loading conditions. Conducted macrographic and metallography analyses revealed good quality appearance joints, with complete fusion joint without presence discontinuities. Low cycle fatigue tests joints conducted under constant amplitude strain control mode. The experienced life reduction respect ~16% at amplitudes 0.2, 0.3, 0.4%. For larger than 0.6%, was reduced 39%. Weld thermal cycles combined analysis indicated tempered martensite during responsible for soft-zone formation poor response.