Keyhole laser spot welding

Physical mechanisms and quality criteria of keyhole laser spot welding partially differ from continuous laser welding, demanding separate investigations. A survey on progress in laser spot welding will be given, encompassing first welds with a ruby laser in the early sixties, various industrial applications, and high speed X-ray imaging of the keyhole and mathematical modeling nowadays. Numerous experimental investigations focus on parameter optimization of the pulsed laser beam in order to obtain a proper weld geometry. Besides, fundamental experimental and theoretical studies have been conducted to improve understanding of the complex physical process behavior of weld defects like pore formation, cracks, spatter and undercut. To control and prevent the above defects different strategies have been studied like pulse shaping or welding in the absence of ambient pressure or gravity, respectively. Recently X-ray observation of the keyhole collapse in liquid Zn accompanied by transient modeling revealed some fundamentals of pore formation.