Abstract
Surfacing on aluminum alloy has been investigated by gas metal arc welding (GMAW) process using a newly developed Al-Cu seamless type cored electrode wire of 1.2 mm in diameter. Two types of cored wires were tested, one is copper sheath type with alminum solid wire as inside core, and the other alminum sheath type. Their chemical compositions were both 30Al-70%Cu.
Investigation were performed on metal droplet transfer phenomena, microstructure and hardness distribution versus arc current, effect of weld heat input on porosity formation, analysis of hydrogen gas from porosities.
The copper sheath cored wire showed far superior quality to the aluminum sheath one. It has excellent arc stability, uniform and stable metal transfer, uniform hardness distribution in the surfacing weld metal. The overlay hardness 220-280 HV decreased with increasing weld heat input. Hydrogen gas causes porosity formation, which is reduced by increasing weld heat input readily to a low level of total area 1% in transverse cross section of surfacing weld metal.
The porosities were very small in size, mostly less than 0.2 mm in diameter. Oxygen also seems to cause porosity formation.
