Mechanical properties of laser-welded and adhesive-bonded ultra-high-strength steel lap joints

Abstract

The need to manufacture lightweight structures from ultra-high-strength steels is forcing industry to look for new joining technologies. Hybrid joints are one of the new ways to join materials. This paper investigates joining ultra-high strength steel plates using laser welding and adhesive bonding. Steel used in this paper was abrasion resistant steel (AR600) with tensile strength (Rm) ≥ 2 GPa. Three different epoxy adhesives were used in the experiments. The weld morphologies were investigated using optical microscopy. The mechanical properties of the lap joints were evaluated by hardness measurements and tensile shear tests. Examining the profiles of the joints, it became clear that the adhesive causes an air gap between the plates, which affects the morphology of the joint. The air gap caused by the adhesive increased the width of the weld at the interface of the plates. The width of the weld at the interface was approximately 25% larger in the adhesive-bonded joint. Based on shear strength tests, the use of adhesive in addition to the laser weld significantly improved the shear strength of the lap joint. The shear strength of the best laser-welded and adhesive-bonded joint was approximately 84% higher than that of laser-welded joint.