Process Research And Applicatiton Exploration Of Integrated Circular Triple-wire Cooperative Control Pluse GMAW

Multi-wire welding is one of the effective methods to achieve high-efficiency gas metal arc welding(GMAW),which has been widely concerned and studied.This paper proposes a new triple-wire welding process—Integrated Circular Triple-wire Cooperative Control Pluse GMAW.The research focuses on the process characteristics of the triple-wire welding and its application in high-strength steel for engineering and aluminum alloy for rail transit.It combines high-speed camera technology,welding current and voltage acquisition technology,Gleeble thermal simulation technology,welding numerical simulation technology,and welding microstructure and performance testing technology,and focuses on comprehensive research on arc stability,droplet transfer form,welding of Q960E high-strength steel,welding of 6082-T6 aluminum alloy,prediction of welding microstructure and performance,optimization of thewelding process,etc.The main results are shown as follows:In terms of arc and droplet transfer,arc blow and droplet offset transfer were the essential of the triple-wire welding.The pulse phase angle was an important factor that affected the arc behavior and droplet transfer mode.The arc below was derived from the electromagnetic effect of the surrounding arcs and the droplet offset,and severe arc blow can easily cause arc break.The arc blow changed the anodic area where the arc adhered to the droplet,which caused the electromagnetic force on the droplet to change from vertical downward to oblique downward.In the welding process,arc blow and droplet offset interacted and developed dynamically.By analyzing the welding processes at the typical pulse phase angles(0°,120°,180°),it was found that the 120°phase angle was the most ideal.Its welding process was stable,and the weld seam was beautiful.Three arcs were alternately pulsed with very slight arc blow,and the droplet transferred evenly with one pulse to drop.Taking Q960E high-strength steel for construction machinery with a thickness of12 mm as the welding object,this study explores the triple-wire pulse GMAW welding of high-strength steels using different heat inputs of 0.79 k J/mm～1.51 k J/mm.It was found that when the heat input was 1.01 k J/mm～1.25 k J/mm,the weld microstructure was side lath ferrite+acicular ferrite,and the microstructure of heat affected zone(HAZ)coarse-grained zone was lath martensite+lath bainite.The comprehensive mechanics of the weld joint showed good performance,which indicated that this welding method is suitable for high-strength steel.In addition,a way to predict the joint’s microstructure and performance was proposed.The SH-CCT diagram of Q960E high-strength steel was first obtained by Gleeble thermal simulation,and then the thermal welding process was simulated by ANSYS software.The combination of the two can accurately predict the microstructure and hardness of the HAZ.The triple-wire pulse welding was applied to the welding of 6082-T6 aluminum alloy for rail transit,and low-frequency modulated pulses were added based on it to obtain another new welding process—triple-wire double-pulse MIG welding.Research on ordinary triple-wire pulse welding and triple-wire double-pulse welding with double pulse frequencies f_d of 1 Hz,3 Hz,and 5 Hz found that the arc length of triple-wire pulse welding was during the welding process unchanged.In contrast,the arc length of triple-wire double-pulse welding changed periodically.The smaller the double pulse frequency,the greater the fluctuation of the arc length,and the wider the fish-scale pattern of the weld.Compared with ordinary triple-wire pulse welding,low-frequency triple-wire double-pulse welding(f_d=3 Hz)can obtain better quality weld joints,with uniformer and more beautiful fish scales on the weld surface,fewer weld pores,and greater tensile strength.