Weldability of titanium sheet for plate type heat exchanger by Nd:YAG laser

Pure titanium and its alloys have excellent corrosion resistance in seawater, high specific strength and creep properties in high temperature. For these reasons, the application is expanded into the field of marine as the heat exchanger plate, marine plant, and so on. Conventional plate type heat exchanger has prevented fluid leakage with gaskets between the plates by mechanical joining method, but gaskets are hardened in high temperature and pressure. Thus, LPG re-condenser which is always in high temperature and pressure, is jointed its plates by welding. Arc weldment has large HAZ and possibility of distortion because of large heat input. And EBW and diffusion bonding make high quality welds, but it should be done in vacuum conditions. Hence, laser welding is applied to get sound beads with small heat input and high aspect ratio in the air. In this study, weld properties of CP titanium were investigated by pulsed and CW Nd:YAG lasers. And welds without porosity, humping, crack, spatter and oxidation were accepted and the best welding conditions were applied to LPG reliquifaction system.