Effect of Welding Speed on Fatigue Property of Laser Welded Dual-Phase Steel

It was observed that the laser welding at low speed or medium speed did not deteriorate the fatigue property significantly, with a drop of about 9-12% in fatigue limit, compared to the parent material. Further, at a high stress amplitude, all samples survived almost similar numbers of fatigue cycles because of similar type of cyclic hardening-softening effect. However, at low stress amplitude, the cyclic softening of martensite was dependent on the magnitude of residual stress. For the joints fabricated at higher welding speed of 0.1 m/s, a decline of 28% in fatigue limit was observed in comparison with that of the parent material. Additionally, faster crack propagation was visible for high speed laser welded sample at both high and low stress amplitudes. It was proposed that the presence of detrimental {001} cleavage plane and high residual stress might have restricted the cyclic softening phenomena for any stress amplitude.