Research On High-speed Tig Welding Arc Behavior And Weld Formation Mechanism Under Longitudinal Magnetic Fields

The current manufacturing puts forward the development direction of the weldingtechnology which includes high efficiency, high quality, low consumption, automation.TIG welding has many advantages such as arc stability, good weld forming, pureappearance small heat-affected zone and no spatter, which can fit for almost all metalmaterials welding. Nevertheless, TIG welding arc energy distribution is dispersed whichlead to a smaller weld penetration and a lower productivity. High speed welding causesanode spot delayed and arc dragged backwards seriously. As a result, the defects such asundercut and convex edge are generated. Longitudinal magnetic fields could be applied tocontrol the motion of arc and the shape of arc which influences heat transfer characteristic,flow law and weld penetration and width. The research on arc radial pressure and analysisof magnetic control mechanism under different magnetic parameters were studied whichcould take good control of the energy distribution of arc plasma effectively and improvewelding speed.In this paper, the research on arc radial pressure distribution and arc shape underdifferent magnetic parameters were measured by high-speed camera and anodewater-cooled copper plate device. The welding parameters as follow: welding current90A,argon gas flow rate10L/min, magnetic induction60mT. The experiment results showedthat arc central pressure decreased from0.36kPa to-0.05kPa. The behavior of arc pressurechanged from unimodal to annular bimodal distribution. When magnetic frequency isbetween60Hz~65Hz, the behavior of arc pressure changed from annular bimodal tounimodal distribution. The arc did rotary motion at a high speed. Arc shape changed fromfan shape to the bell shape. Arc central pressure had increasing tendency, Maximum arcpressure appeared in frequency of1200Hz~1500Hz in high frequency magnetic fields.Comparing with common TIG arc shape, the rotational radius decreased. Welding and metallographic experiments indicated that weld structure became smalland well-distributed under an additional alternating longitudinal magnetic field. Moreover,weld formation could be obtained in adaptive magnetic parameters. It had a range offrequency which could get a deeper penetration at magnetic induction50mT. It couldimprove welding speed in high frequency magnetic fields. With parameters of weldingcurrent90A, argon gas flow rate10L/min, magnetic induction50mT and magneticfrequency1200Hz, the highest speed could reach3.5m/min.