Study On Arc Physical Characteristics And Welding Technology Of (AC) TIG-MIG Hybrid Welding

In traditional gas shielded welding, good weld appearance can be obtained by TIG welding, however, its production efficiency is quite low. MIG welding has higher production efficiency, but when adopting Ar as shielded gas, the weld process is unstable and the welding appearance is bad. Moreover, common welding defects, like the undercut and irregular weld seam, can be easily occurred when employed high welding current and welding speed in gas shielded welding. High efficiency, high quality and low energy consumption is always required during welding, so in present paper, alternative current (AC) TIG-MIG hybrid welding is applied to improve the welding efficiency on the premise good weld appearance.Previous research on TIG-MIG hybrid welding at home and abroad are used in the double direct current (DC), and (AC) TIG is adopted instead of (DC) TIG in this paper. The experiment of (AC) TIG-MIG hybrid arc surfacing low carbon steel is studied. Using the electrical parameter-graph synchronous data acquisition system, the characteristic of hybrid arc, drop transfer, the flow of weld pool and the weld appearance are analyzed. Based on the weld appearance under different welding parameters, the effect mechanism of welding parameters on the welding process is also obtained.The dynamic behavior of hybrid arc in (AC) TIG-MIG hybrid welding process is clarified. The variation of morphology of hybrid arc and electrical parameters with different wire-tungsten distance is also studied. The research shows that the arc polarity changes of TIG make the two arc periodic attractive and repulsive, and the typical standard wave characteristics appear during the decrease of the positive half wave current of the (AC) TIG arc. The influence of MIG arc on the physical characteristics of (AC) TIG arc, the influence of (AC) TIG arc on the physical characteristics of MIG arc and the influence of wire-tungsten distance on the physical properties of (AC) TIG arc and MIG arc are analyzed in detail. The arc electron emission mechanism is employed to explain the increased current and decreased voltage of positive (AC) TIG arc semiwave, the constant current and voltage of negative (AC) TIG arc semiwave, and the increased MIG arc elongation. And the control system of MIG arc is also used to reveal the reason why the current of MIG arc increased during TIG-MIG hybrid welding.The phenomenon of MIG drop transfer during (AC) TIG-MIG hybrid welding is further analyzed, and it is found that the liquid metal flow in the front of MIG welding wire is periodically oscillating under the action of Lorenz force of TIG arc. The reasons why the undercut and damping is effectively suppressed during (AC) TIG-MIG hybrid welding are discussed. The formation of different weld appearance under different wire-tungsten distance and different (AC) TIG arc current is explored. The suitable combinations of MIG welding parameters and (AC) TIG welding parameters and wire-tungsten distance (≥4mm) with good weld appearance are obtained which expands the range of welding parameters.Under the condition that the current of TIG is less than MIG, the (AC) TIG-MIG hybrid welding, compared with the (DC) TIG-MIG hybrid welding, has a relatively large adjustable wire-tungsten distance range with good weld appearance are obtained. TIG-MIG hybrid welding available range of welding parameters is enlarged.