Effect of Laser Beam Offset and Filler Wire on Laser Lap-Fillet Welding of Al–Si-Coated 22MnB5 Steel

Abstract

Laser lap-fillet welding was used to weld Al–Si-coated 22MnB5 steel. The effect of laser beam offset and filler wire on microstructure and mechanical properties of the joint was investigated. Weld depression was observed with the low laser beam offset. Increasing the laser beam offset or adding filler wire was beneficial to good weld appearance. The fusion zone (FZ) consisted of martensite (in Al-deficient regions) and $\delta$-ferrite (in Al-rich regions). The amount of $\delta$-ferrite with filler wire was less than that without filler wire when the other welding parameters were the same. Three different zones existed in the heat-affected zone (HAZ) with microstructures of martensite (inner HAZ), mixed martensite and ferrite (middle HAZ) as well as tempered martensite (outer HAZ). The outer HAZ with tempered martensite exhibited the minimum hardness (about 250HV_0.1). After the tensile test, the specimens with low laser beam offset were fractured at the FZ of the upper sheet, while the specimens with high laser beam offset (more than − 1 mm with filler wire and 1 mm without filler wire) were fractured at the HAZ (the soften zone, outer HAZ). The maximum tensile force was 9581 N with the laser beam offset of 2 mm and with addition of filler wire.