Deep-penetration welding-brazing of aluminum/steel dissimilar metal using laser-MIG arc hybrid heat source

Deep-penetration welding-brazing process without gap of steel/aluminum dissimilar metal butt joint with a thickness of 4 and 6 mm was achieved using laser-MIG hybrid heat source. The welding parameters were optimized to obtain a sound joint and the microstructure of the interfacial layer was observed by scanning electron microscopy (SEM) and experimental validation. The joint temperature distribution of three welding methods: MIG welding-brazing, laser welding-brazing, and laser-MIG hybrid deep-penetration welding-brazing were investigated by finite element method (FEM) numerical simulation. Moreover, the effect of laser deflection angle on the temperature distribution of the laser-MIG deep-penetration welding-brazed joint was investigated. The results indicated that the temperature distribution of laser-MIG hybrid deep-penetration welding-brazed joint was more uniform than MIG welding-brazing and laser welding-brazing. The temperature of the lower part of the joint was increased, which was beneficial to improve wetting and spreading of the liquid metal on the stainless steel and obtain better weld formation. In the laser-MIG hybrid deep-penetration welding-brazing process, the temperature of the lower part of the joint interface and the interface temperature gradient could be improved by adjusting the laser deflection angle, which was beneficial to the formation of uniform intermetallic compound layer. Typical welding-brazing joint characteristic with the thickness of 4 mm using laser-MIG hybrid heat source was found. The main phases of interface layer compounds were composed of Fe4Al13 and Al8Fe2Si, and the weld metal consisted of α-Al and Al-Si eutectic. The 6-mm steel/aluminum joint was also achieved by using laser-MIG hybrid heat source, but some cracks at the interface were observed.