Development of underwater welding with high power YAG laser

Underwater YAG laser welding technology has been developed by IHI. Use of optical fiber for the YAG laser welding system provides accessibility to distant or confined repair work sites. The welding system is also applicable to repair welding of reactor pressure vessels (RPV) and the internal structures of these vessels. Stable underwater welding was successfully performed using the center gas shielding method at a water pressure up to 0.4 MPa. No defects were found in welds by radiographic testing. Bead width and penetration depth became wider and shallower with increasing water pressure, respectively. The cooling rate of YAG laser welding was measured and proved to be higher than that of TIG welding. (author)