Defects formation mechanisms in laser welding and their suppression methods

The significant problems of laser welding, particularly by a pulsed laser, are formation of various welding defects such as porosity, cracking and undercutting. In order to reduce these defects, the authors have developed a special laser with pulse shaping function. The paper describes the effects of pulse shaping on reduction of porosity and weld cracking of spot welding of difficult materials such as Al-alloys and stainless steels. By the selection of optimum pulse shape the defects can be drastically reduced and the sound weld is possible to obtain.