Fatigue Crack Growth in Laser Weldments of a Cold Rolled Steel

Abstract

This paper describes the effect of laser welding process on the fatigue crack propagation in SPCC-CQ1 cold rolled steel. The influences of weld speed and gap width of butt joint on fatigue crack growth rate are considered. Strength of the weld joints is evaluated by a tensile test, while fatigue properties are investigated by fatigue crack propagation test based on linear elastic fracture mechanics. From the results, the added wire filler material had positive effect on the fatigue properties. Increasing welding speed or gap width will improve the resistance 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 base metal. Transgranular fracture is the typical fracture mechanism and many secondary cracks appear in the fusion zone.