Thick plate welding with Nd:YAG laser and COIL

In the field of heavy industries, many products are made of thick metal parts. Nd:YAG laser has been recently developed up to 10kW [1]. Nd:YAG laser has the characteristics of the optical fiber transmittance and the good absorption by the metal surface, so that it is expected to apply Nd:YAG laser to thick plate welding. This study presents the thick plate welding with Nd:YAG laser and COIL (Chemical Oxygen-Iodine Laser). We have developed a coaxial beam combining system with beams of Nd:YAG laser and COIL [2,3]. The maximum average power of the combined beam was 19kW. Welding tests of 304 stainless steel plates were carried out. The effects of various welding parameters were investigated, such as the laser power and pulse modulation. As a result, it was clarified that the pulse wave has good efficiency of deeper penetration as compared to continuous wave at low welding speed. When the combined beam was used, 20mm penetration depth on the stainless steel could be obtained in high aspect ratio at welding speed of 1m/min. When the combined beams and another Nd:YAG laser beam whose power was 4kW were used, both side welding on 30mm. thickness plate could be achieved.