| Dissimilar steel fillet welds composed of stainless steel and low carbon steel are widely used in petrochemical,pressure vessel,ship and other machinery parts production.However,due to the great difference in thermal conductivity,specific heat capacity and other thermal physical properties of dissimilar steel materials,the weld pool depth on both sides of the weld has a great difference,and welding defects such as cracks and edge bite are easy to occur in the welding process.Therefore,it is necessary to intervene and effectively regulate the arc heat input on both sides of the weld.Magnetic arc technology has the advantages of simple device and strong applicability,and can effectively change the arc shape and adjust the arc heat flux density by applying magnetic field.Based on this,this topic proposes to add transverse magnetic field in the welding process to adjust the arc deflection Angle,so as to change the distribution of arc heat input in the base metal on both sides of the weld,affect the heat input ratio in the input workpiece,and improve the welding quality of dissimilar steel fillet weld.The main research contents are as follows:(1)Considering material properties of dissimilar steel,a two-dimensional transient GTAW arc model of dissimilar steel fillet weld was established based on computational fluid dynamics(CFD)and heat transfer theory,and the distribution and change of transient arc temperature field under pulse current were numerically simulated.The mechanism of arc magnetic bias blowing during welding of dissimilar steel was studied and the influence of welding current on arc magnetic bias blowing was obtained.The distribution law of anode heat flow of arc under different Angle of welding torch was clarified and the regression equation between welding torch Angle and total heat flow on both sides of weld was established.(2)to explore the fillet weld dissimilar steel welding arc and weld pool,the mechanism of coupling between Angle of dissimilar steel welding is established GTAW arc-molten pool coupled three-dimensional transient model,the arc of the electric field,flow field,pressure field,temperature field and the Angle of dissimilar steel weld molten pool forming process of the coupling calculation,and experiments verify the validity of the model.The arc and weld pool of dissimilar steel fillet weld are asymmetrically distributed and deflected towards the side of mild steel due to magnetic deflecting and material property difference.The forming law of weld pool of dissimilar steel fillet weld with welding time is obtained.(3)Propose a method of using transverse magnetic field to change the arc deflection Angle,so as to realize the reasonable intervention and effective regulation of arc heat input,and improve the forming quality of dissimilar steel fillet welds.A GTAW arc-weld coupling model of dissimilar steel fillet weld under external magnetic field was established.Numerical simulation of arc and weld pool under external transverse magnetic field was carried out,and relevant tests were carried out.The arc temperature field and arc shape under different magnetic induction intensity,the temperature field distribution of molten pool and the fusion line of molten pool are obtained.The relationship between arc deflection Angle,arc temperature and applied transverse magnetic field is obtained.And the change of molten pool shape and molten pool appearance size under different magnetic field intensity;The thermal input distribution of arc anode surface was obtained by integrating and summation of the heat flux density at different magnetic induction intensities from 0 to 35 m T.The governing equation of arc heat input distribution is established.Two distribution methods of arc heat input,welding torch deflection and external transverse magnetic field,are compared.The results show that the distribution method of arc heat input with external transverse magnetic field has the advantages of large arc deflection Angle and fine adjustment. |
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