Beneficial effect of low frequency pulsed MIG welding process on grain refinement of weld metal and improvement of solidification crack susceptibility for aluminium alloy

Vibration of molten puddle is achieved with the low frequency pulsed MIG welding process of new current waveform to switch over two preset unit pulse conditions alternately. The degree of this vibration depended on swiching frequency of unit pulse conditions, and there was an optimum frequency range of fa = 10-30 Hz, and moreover large difference between two pulse current values promoted the molten puddle vibration. It was made clear that the stirring effect of molten puddle was expected by this process and this resulted in the remarkable grain refinement of weld structure of commerical available Al-Mg alloy base metal and wire within the optimum frequency range, especially fa = 30 Hz. Moreover, this process had abenficial effect to improve the solidification crack susceptibility of Al-Mg alloy weld metal due to the grain refinement.