Inhibition Mechanism of Crystal Crack in Copper Thick Plate He-GTA Welding by Adding Deoxidant Element Ti

He-GTA welding of 10mm thick copper plates by using independent developed welding material - CuTi alloys was investigated. The crystal crack induced by eutectic of Cu and Cu2O is disappeared completely as the addition of deoxidant element Ti. It can be concluded that the Ti inhibits the formation of Cu2O and combines with O to generate TiO2 through the thermal dynamical calculation. As the TiO2 has the characteristic of high molt point and low density, TiO2 flows upward to surface of molten pool during welding and forms as weld slag at the weld surface after cooling, then the uniform microstructure without crystal crack is obtained finally. In all GTA welding specimens tested, the failure is located in the heat affected zone and the tensile strength is similar to the base metal.