Laser spot weld bonding of mild steel

Laser spot weld bonding (LSWB) is a new joining process, which combines laser spot welding with a layer of structural adhesive in a single joint. The purpose of this paper is to introduce a new LSWB process with a special pulsed laser. With this method, the impact of adhesive gas on molten pool is weakened, and the gas can exhaust from the gap of the metal sheets. The carbon decomposed from the adhesive diffuses into the molten pool and changes the microstructure of the weld joint. The joint is mainly composed of martensite and bainite, and twinned martensite is found in the interface between the adhesive layer and metal sheet. In tensile shear test, LSWB specimens give the highest energy absorption compared with laser spot welded samples and adhesive bonded samples.