Dissimilar steel-to-aluminum joint structure made in laser welding technology

Currently, the design of the car seat is made of steel, and the automotive industry itself seeks to reduce the weight of vehicles, especially passenger cars, as much as possible. Hence the concept of using aluminium alloys to create a modern skeleton structure of car seats, which would affect the minimization of the weight of the whole car. Laser welding was used due to high technological efficiency and maximum automation of the operation of this process, which determines the repeatability of making welded joints in a very short time. The paper analyses the choice of laser welding parameters of D04 steel with EN AW-6060 aluminium alloy based on the welds obtained. The aim of the structure assessment was to perform macro- and microstructural tests using scanning electron microscopy and microhardness tests of joints at the weld and native materials. The obtained results prove that the weldment of steel from aluminium is a perspective technology that can be used practically in the automotive industry. The goal of the structure analysis was to perform macro- and microstructural investigations using scanning electron microscopy and microhardness testing of weld joints including also the substrate material. Among the tested welding parameters, the most favourable weld parameters values were obtained for: laser power 800 W, weld speed 0.3 m/min, focus diameter (ϕ) 200 mm, and beam focus raised by 1 mm above the surface of the steel plate.