Small Batch Laser Welding Using Light Fasteners and Laser Tack Welding

Laser welding is known for its low heat input compared to arc welding methods. This could enable laser welding of sheet metals with lighter fastening solutions and less time-consuming tack welding alternatives. A feasibility study was carried out to study four different corner joint types for 2 mm thick cold rolledcold-rolled steel sheet by using filler-free laser welding. The aim of the research was to get more experimental knowledge about the laser welding of corner joints. Also possible benefits concerning faster manufacturing times and smaller costs by developing fastening applications for small batch laser welding was to be studied in practice. The 170 mm long joints were welded without air gap or pressing. All corner joint types proved to be weldable with a continuous wave Yb:YAG diode-pumped disk laser. It was also found during the With the experiment it was also found out that laser welding enables the use of light and inexpensive fasteners such as magnetic holders in steadinstead of traditional clamps and fixturing. With some joint types, the insufficient fastening power of magnetic fasteners against distortions was compensated by making a spot-like laser tack weld toat the end of the weld before welding the actual seam. This showed that it is possible to make precise and small tack welds with a laser and to use laser -tacking in sheet metal assembly.

Analysis of circumferentially welded thin-walled cylinders to study the effects of tack weld orientations and joint root opening on residual stress fields

In recent years, the demand for resilient welded structures with excellent in-service load-bearing capacity has been growing rapidly. The operating conditions (thermal and/or structural loads) are becoming more stringent, putting immense pressure on welding engineers to secure excellent quality welded structures. The local, non-uniform heating and subsequent cooling during the welding processes cause complex thermal stress—strain fields to develop, which finally leads to residual stresses, distortions, and their adverse consequences. Residual stresses are of prime concern to industries producing weld-integrated structures around the globe because of their obvious potential to cause dimensional instability in welded structures, and contribute to premature fracture/failure along with significant reduction in fatigue strength and in-service performance of welded structures. Arc welding with single or multiple weld runs is an appropriate and cost-effective joining method to produce high-strength structures in these industries. Multi-field interaction in arc welding makes it a complex manufacturing process. A number of geometric and process parameters contribute significant stress levels in arc-welded structures. In the present analysis, parametric studies have been conducted for the effects of a critical geometric parameter (i.e. tack weld) on the corresponding residual stress fields in circumferentially welded thin-walled cylinders. Tack weld offers considerable resistance to the shrinkage, and the orientation and size of tacks can altogether alter stress patterns within the weldments. Hence, a critical analysis for the effects of tack weld orientation is desirable.