Numerical Simulation And Experimental Study On Welding Temperature And Stress Field Based On T-joint MAG Welded High Strength Steel

High-strength steel is widely used in various welding structures and has an increasing demand for application in other fields owing to its unique properties-high strength and good ductility.However,On account of its high alloy content as well as metallurgical properties,the high strength steel is harder to be welded compared to the plain steel.Furthermore,the high strength steel weld bead occur to failure frequently,which severely limit its application in the engineering field.In this study,in order to improve the welding quality of high strength steel,numerical simulation and experiments are performed to investigate the T-joint fillet MAG welding temperature and stress field based on high strength steel welding procedure.In this paper,numerical simulation of T-joint fillet high-strength steel welding is carried out based on thermal elastic plastic finite element method.Welding thermal cycle curve along with welding stress and deformation are analyzed.Experiments are performed to investigate the T-joint fillet MAG welding temperature and stress field by thermocouple measuring.After that the simulation results are compared with the obtained experimental results.It turns out that FEM results agree well with experimental results,thus confirming the accuracy and preciseness of numerical simulation.Effects of different welding parameters on welding temperature field are further compared and investigated,identifying that welding speed,current and voltage are three key factors.Orthogonal experiments indicate the optimum combination of welding parameters,which provides theoretical basis for the evaluation and optimization of high-strength steel welding.Analysis of numerical simulation and experimental results are as follows:(1)Simulation results of the welding peak temperature and welding thermal cycle curve are consistent with experimental measurements,thus verifying the reasonableness of the selected heat source model and welding procedure before welding and confirming the accuracy and preciseness of numerical simulation model established for welding temperature field and stress field.Under the influence of a moving heat source,the heated and welded metal experienced cycle with dramatic changes of time and space.The peak temperature of the thermal cycle exceeds the material's melting point and it is up to 1580 centigrade,the front isotherm being intensive,while the rear isotherm being sparse.(2)Welding procedure has a certain impact on the temperature field,the effective stress and deformation of high strength steel.Under certain conditions where other procedure parameters are constant,welding speed,welding current and voltage produced a great impact on temperature distribution of the welding zone.By orthogonal experiment,it has been proved that the best welding process combination is 110A(welding current),25V(welding voltage),8mm/s(welding speed),45�(welding gun angle).Taking the operability of the engineering into account,parameter values should be close to the optimal values.(3)Along the welding direction,the effective stress of selected nodes moves up and down over time.After the welding process,welding effective stress gradually stabilized,remaining at a relatively stable value(about 300MPa).It can be known from the normal stress of X,Y and Z directions that on the vertical direction of the welding,tensile stress makes the most impact,the maximum tensile stress reaching 449MPa.While at the beginning and end of the weld bead,the steel under the compressive stress,the maximum reaching 471 MPa.