Numerical Simulation Of High Strength Steel Weld Forming By Vertical-up Swing MAG

Heavy plate low-alloy high-strength steel is commonly used in the manufacture of ships,with high strength and high toughness and corrosion resistance.Double-sided double-arc welding has the advantages of high efficiency,high quality and small corner deformation in the welding of thick plates.The quality of the bottom welding is the key to determining the overall life of the weld.In this paper,the single-faced double-sided forming of the thick-walled bevel opening is accomplished by the swing MAG welding method.The influence of different groove profile factors on root penetration is studied.The optimal parameter matching is analyzed to provide guidance for the use of welding bevels in actual shipbuilding.First of all,with the X-groove and the trapezoidal groove,the shape of the swing arc is photographed.When one side stays,the arc is distributed asymmetrically,and the arc plasma flows along the inclined side of the groove to the root.Based on this,a heat source for the arc swing is established and the double ellipsoidal heat source is subjected to coordinate conversion is moved and rotated.A mathematical model of the flow field calculation was established,and the heat source and various force equations were added.Experiment design through orthogonal design tables.Three tests are selected for each groove to perform actual welding.At the same time,the root heat cycle curve is measured and the heat source is checked accurately.Using the established mathematical model,the welding process for the bottom weld of the X-groove and the trapezoidal groove is calculated.The flow of the bath in the groove and the result of the weld formation show that the main flow in the transverse section flows from the center of the weld pool where the arc is located to the root,and flows back to the surface of the bath via the fusion line.However,when the gap is small,the liquid bridge that stays on both sides will prevent the molten pool metal from flowing to the root,resulting in unfused.On the other hand,the continued flow to the roots at the two sides of the dwelling place caused a deeper penetration of the dwelling.The longitudinal section shows that the main flow is an upward tumble vortex.At the same time,the method of orthogonal design was used to calculate the root penetration and back forming under the conditions of each experimental groove.According to the orthogonal analysis,the gap is most affected by the X groove factor,while the trapezoidal groove is the blunt edge.The best groove parameter matching result of X groove is clearance 2mm,blunt edge 0mm,trapezoidal groove is gap 2mm,blunt edge 0mm,and back weld groove width is 4mm.From the perspective of heat conduction,the method for the change of the area of the melting area required for thepenetration of the root was proposed.The calculation results are consistent with the results of the orthogonal analysis.According to the shape change from the X groove to the trapezoidal groove,a new U-shaped groove is used for the welding test.The groove parameter matching adopts the factory exploration results.The obtained weld bead has a good penetration and has a very smooth surface forming and back forming.The purpose of single-sided and double-sided forming is well achieved.