Research On Metal Transfer Behaviors Of Ultrasonic Assisted Metal Inert Gas Arc Welding In Aluminum Alloys

The ultrasonic wave was applied on the welding process of metal inert gas arcwelding (MIG) in steel. The metal transfer frequency was increased, the stability ofmetal drop transfer was improved and the available voltage range for short-circuitingtransfer was enlarged. The ultrasonic assisted metal inert gas arc welding (U-MIG) wasapplied in aluminum alloys based on that effect above. The change rules of the arcshape in aluminum alloys were gained. The Characteristics of different transfer modeswere analyzed. The comparative analysis was carried on between different phenomenaof steel and aluminum. The parabolic path in conventional MIG vertical positionwelding was changed.The reasonable technological parameter was identified. Workable welding voltageand wire speed range covering short-circuiting transfer, globular transfer and projectedspray was determined. Based on the ascertained ultrasonic parameters the effects ofshielding gas flux and electrode extension on arc shapes were discussed. The arcphenomena were observed by the high speed camera and the sensors of electric signal.The melting speed curve and static characteristic curve were drifted.The characteristic of droplet transfer in U-MIG short circuiting transfer wassystematically analyzed. Droplets with huge volume, which float above the molten poolbut don’t fall, were observed in aluminum short-circuiting transfer. The non-classicalshort circuiting transfer was believed caused by the metal stream explosion beneathaluminum magnesium alloy droplet. That different roles were played by ultrasonic indifferent welding voltage rage was analyzed bonding with the distribution mode of theacoustic field in the complicated welding environment. The comparative analysis wastaken on the positive effect of ultrasonic in the steel short circuiting transfer combiningwith different physical properties between steel and aluminum alloys.The free transfer form law and special phenomenon in aluminum U-MIG wereresearched. Ultrasonic plays an positive role in the droplet transfer’s welding parameterrange. The drop transfer frequency is increased markedly and the droplet size isminimized. The drop shape of aluminum was changed severely before detaching fromwire tip. The high vapor pressure metals magnesium, zinc and cadmium, exhibitedtransfer characteristics which were controlled by metal vaporization. The degree ofexplosiveness found in an aluminum alloy containing volatile components increased asa function of the partial pressure of the alloying element. The huge drop bubbleappeared, explosiveness rate is increased and porosity in welding bead was decreasedsignally. Ultrasonic cavitations theory was used to explained the cause of drop bubbles and the mechanism of the ultrasonic degassing on droplets. The force in molten dropdetaching from wire is much bigger in vertical position, the initial horizontal velocity isincreased, vertical displacement is decreased and the track of drop transfer is changed.