Laser welding applied to advanced high strength steels for automotive applications

The use of Advanced High Strength Steels (AHSS) in the car industry is permitting to improve vehicle safety while reducing structural weight. This is possible thanks to their very high mechanical properties. Nowadays, steels with tensile strength up to 800MPa are widely spread in industrial applications. However the use of AHSS for cold stamping with tensile strength between 1000MPa and 1500MPa is not so extended. Furthermore, when used, these steels are usually joined to other parts by resistance spot welding, the most established joining process in car industry. The work presented is focused on laser welding of dual phase and martensitic steels with tensile strength between 600MPa and 1500MPa. The aim of this work was to acquire the knowledge needed when designing new components of AHSS including laser seams. The geometries studied were butt joints, overlap joints and TWB joints with sheet thickness between 1mm and 2mm. Aspects such as microstructure, hardness, mechanical strength, fatigue strength and forming behaviour will be presented.