Effect of Ti on hot cracking and mechanical performance in the gas tungsten arc welds of copper thick plates

The new welding material – ERCuTi alloys filler metals were developed for gas tungsten arc welding (GTAW) of copper. The cracking susceptibility of the welds with ERCuTi and ERCu separately in GTAW of 10 mm copper thick plates was investigated. The formation causes of hot cracking was researched by using ERCu and the suppression mechanism of hot cracking when using ERCuTi alloy filler was proposed. It has been found that, when element Ti is added into the welding pool, the Ti will combine with O preferentially rather than Cu to generate TiO2, which process can suppress the formation of Cu2O. The hot cracking force and the hot ductility of the welds in brittle temperature range (BTR) could be improved effectively by adding Ti in filler metal compared with that of the welds without Ti. But the degree of addition of Ti (2–4 wt%) is critical when the susceptibility of cracking is to be suppressed. If the level is allowed to exceed 4 wt%, more low-melting point eutectics (β-TiCu4 and TiCu2) will be formed in the welds, and cracking susceptibility will be increased again. Results of mechanical properties tests show that although adding Ti increases the hardness and strength of the weld compared to the base metal, the impact ductility and the plastic properties are not decreased significantly.