Research On Plasma-mig Hybrid Arc Welding Process For Aluminum Alloy Fuel Tank

The Plasma-MIG hybrid arc welding is one of the hybrid power weldingprocesses: first way is the variable binding of the plasma arc and ordinary MIG arccoaxial hybrid with water-cooled, and the second way is offset TIG way composite.Due to the Plasma-MIG hybrid arc’s complex coupling influence, hybrid arcpresents new technological features. The conventional MIG welding of LD10aluminum, the joint usually exist porosity, and joint soften seriously. The complexcharacteristics of the Plasma-MIG hybrid arc and its progress characteristics werestudied, which enrich the research of the Plasma-MIG hybrid arc welding process.In order to achieving the stable control of the Plasma-MIG hybrid arc welding,the Plasma-MIG hybrid arc welding control system was be optimized, which wasapplied the Mitsubishi FX2N PLC as the core component, and HMI as the I/Ocomponent.Paschen’s Law was applied to analyze and calculate the plasma arc ignitionpath, which under the circumstances of a MIG arc was established earlier. Weldingsystem has been optimized to improving the Plasma-MIG hybrid arcstarting-arc-rate.The situation which of droplet transfer shift occurs when the plasma arc shiftedto aside was studied, and the deviation direction of droplet and plasma arc was same.According to analysis the reasons of it, the optimization measures were given in thepaper.According to analysis both sides of the base metal heat cycle curve at differentplasma currents，the puddle and arc heat distribution characteristics in the lockbottom sides of the joint was concluded. By analyzing the microhardness of jointand the metallographic of the joint, the influence of the welding parameterschanging was studied.The study of the impact of Plasma-MIG hybrid welding process characteristicson weld area Metallographic, the different welding parameters was conducted in thewelding. The results showed that: As the plasma current increases, large equiaxedcrystals change to fine columnar crystals, and when the plasma ionization increasedto90A, weld metal was overheating, columnar grain increased significantly. Undera small welding speed, welding line energy was larger, and weld area formed a large equiaxed, as the welding speed boost, weld area began to appear columnar crystals,with a further increasing of welding speed, columnar crystals translated to asignificantly thinner one. The LD10-side of the fusion zone width increased withthe plasma current increases, the size and organization of the fusion zone increasedwith the plasma current increases, the defects of the fusion zone of L3-side isreduced. When the plasma current is65A, the weld fusion zone appeared finecrystals. And when the plasma current continues to increasing, the near weld fusionzone and the fusion zone appeared large equiaxed.Element distribution of LD10-L3lock bottom weld and the correspondingchanges of mechanical properties were studied. The results showed that thedistribution of elements in the weld zone is not uniform: from the fusion zone ofLD10to the side of fusion zone of L3, the distribution of aluminum elementsgradually increased, while the alloying elements gradually reduced. Causing thejoint performance gradually deteriorated.A seven-parameter regression model system was established to study theeffects of welding parameters between single and interaction of various parametersof weld. Concluded that: the impact of MIG voltage to the weld width ismaximum,i.e. the higher voltage means a wider joint width,the impact of weldingspeed was weak, and the impact of plasma current is weaker,while the impact onmelting torch height width is not significant. Plasma current has the maximumimpact to the penetration of joint, i.e. a greater plasma current means a deeperpenetration of weld, the impact of MIG voltage was weak, while the impact of thewire feed speed penetration is relatively small. MIG voltage and plasma-gasinteraction has the biggest effects on weld reinforcement, for the single factor, theimpact of plasma current has the strongest impact, i.e. high plasma current means alarger weld reinforcement.The prediction model was validated by the experiment. Experiment resultsshowed that, the prediction model can accurate guide the experiment, i.e. The weldprocess can be given accurately. The result is that the welding quality of joint hasreached a joint requirement of classⅠ.