FATIGUE-CRACK GROWTH IN LASER WELDMENTS OF A COLD-ROLLED STEEL

This paper describes the effect of laser welding process on the fatigu e crack propagation in SPCC-CQ1 cold rolled steel. The influences of w eld speed and gap width of butt joint on fatigue crack growth rate are considered. Strength of the weld joints is evaluated by a tensile Les t, while fatigue properties are investigated by fatigue crack propagat ion test based on linear elastic fracture mechanics. From the results, the added wire filler material had positive effect on the fatigue pro perties. Increasing welding speed or gap width will improve the resist ance to fatigue crack growth because of fast cooling rate and refined equiaxed microstructure in fusion zone. Also, the fatigue crack growth rate of fusion zone and heat affected zone are lower than that of bas e metal. Transgranular fracture is the typical fracture mechanism and many secondary cracks appear in the fusion zone.