Impact of inter-sheet gaps on laser overlap welding performance for galvanised steel

For overlap joints with different galvanised sheet combinations, the inter-sheet gap size and range control under different conditions were experimentally studied, and the factors affecting the inter-sheet gap range were examined. The application of a δ control method to laser welding of car door parts was explored. The results indicate that the formation and strength of weld joints initially improve and then worsen as the inter-sheet gap increases. The inter-sheet gap for different types of sheet combinations has a specific range, the value of which is related to the sheet thickness, weld pool width, welding speed, and laser beam parameters. Further, the consistency of the size of δ along the entire welding bead can be maintained by using a subsection welding method. Application of the conditions identified here, in combination with optimal technological parameters, can facilitate the high-quality welding of auto-body parts.

Laser weld of car door parts for different degrees of inter-sheet gap control.In this paper, the impact of inter-sheet gap sizes on the formation quality of a weld and on the performance of laser overlap welding has been analysed. For overlap joints with different sheet combinations, the optimal inter-sheet gaps and maximum weld gaps under different conditions were experimentally obtained. The factors affecting the optimal gaps and maximum weld gaps were then analysed. Based on the data from the experimental analysis, the application of a gap control method to the laser welding of car door parts has been explored. The experimental results indicate that the inter-sheet gap size and range control are related to sheet thickness, weld pool width, welding speed, and laser beam parameters. Within the weldable inter-sheet gap range, the variation of inter-sheet gaps has little impact on the weld appearance and mechanical properties of the joint. However, when the gap is overly small, defects, such as welding pores and spatters tend to occur during welding, and the weld strength decreases. When the gap is overly large, it is filled by the weld pool metal materials. This causes a severe depression at the upper surface of weld joints, the welding quality decreases, and a ‘false friend’ may be created owing to incomplete fusion of the upper and lower sheets. For laser welding of auto-body parts, the consistency of the gap size along the entire welding bead can be maintained by dividing the weld joint into subsections. Application of the conditions identified here, in combination with the technological parameters, including the optimal gap size, the weld appearance is improved, and high-quality welding is realized.Figure optionsDownload as PowerPoint slide