Cracking prevention in laser welding of high-restraint joints

Abstract

High power lasers have been widely used to weld a variety of products in industries. One of the most popular applications is laser welding of transmission components in the automotive industry such as gear clusters, splines, couplings and clutches. However, they are high-restrained joint configurations and solidification cracking is one of the most-often encountered problems. Cracking prevention is a major concern in laser welding of such joint configurations. In this study, cracking mechanism in laser welding was reviewed and the methods to prevent cracks in laser welding of a high-restraint joint (gear to shaft) were investigated. Although several kinds of cracks were observed in the high-restraint welds such as centerline and transverse cracks, the cracks in the joints are solidification cracking in nature that occurred in the fusion zone near the end of solidification under tension stresses. To prevent the solidification cracking in laser welding of the high restraint gear/shaft joint, several joint designs and welding methods were tested, including use of stress-relief grooves, pre-heating, optimization of welding parameters, use of filler wires, discontinuous welds. The results indicated that proper joint designs could avoid solidification cracking effectively in laser welding of the high-restraint joint.High power lasers have been widely used to weld a variety of products in industries. One of the most popular applications is laser welding of transmission components in the automotive industry such as gear clusters, splines, couplings and clutches. However, they are high-restrained joint configurations and solidification cracking is one of the most-often encountered problems. Cracking prevention is a major concern in laser welding of such joint configurations. In this study, cracking mechanism in laser welding was reviewed and the methods to prevent cracks in laser welding of a high-restraint joint (gear to shaft) were investigated. Although several kinds of cracks were observed in the high-restraint welds such as centerline and transverse cracks, the cracks in the joints are solidification cracking in nature that occurred in the fusion zone near the end of solidification under tension stresses. To prevent the solidification cracking in laser welding of the high restraint gear/shaft joint, several joint d...