Numerical Simulation And Experimental Study Of Double Wire Welding Of Low Alloy High Tensile Steel Thick Plates

As a structural steel with good toughness,plasticity,welding performance and energy saving and weight reduction,low alloy high strength steel is widely used in large engineering structures,In the field of ships,aviation,construction,thick plates are being used more and more,and thick plate structures have higher requirements for welding quality as welding stress and deformation will occur during the welding process.Double wire welding is a highly efficient welding method,which has a high welding speed and melt rate,and can independently adjust the process parameters of the front and rear wire and the distance between the front and rear wire,which better meets the requirements of thick plate for large melt depth welding technology.Through the method of numerical simulation,different process parameters of the thick plate double wire welding process of post-weld residual stress and deformation analysis,can provide data support for the optimization of the actual double wire welding process parameters.This paper addresses the residual stresses and deformations generated in the double wire welding process of thick plate steel,with 30mm thick Q390 low alloy high strength steel as the research object,the finite element simulation of double wire welding process was carried out by ANSYS finite element software.For the double fillet welding double heat source loading theory,using APDL command flow and raw death unit technology to write two double ellipsoidal heat source loading and moving procedures,by setting the heat source loading position so that the heat source is applied to the weld one after the other.Firstly,the temperature field of the backing welding layer of thick plate double wire welding is simulated and calculated,and the influence of process parameters such as heat input,preheating temperature and double wire spacing on the temperature field of double wire welding is clarified.Secondly,according to the calculation results of backing welding,the simulation process parameters of multi-layer multi-pass welding are determined,and the evolution law of temperature field and the change of thermal cycle curve under different paths are analyzed.The study result show that the thermal cycle curve of the temperature field of the double wire welding process has two peaks,the change in process parameters will affect the peak temperature,but does not change the trend of the heat curve.In the process of multi-layer and multi-pass welding,the peak temperature increases with the increase of welding layers.On the basis of the temperature field,the indirect coupling method is used to calculate the stress and deformation fields of the double wire welding process based on the thermo-elasticity theory,and to analyse the distribution of residual stress after welding in the double wire welding process of thick plates.Further,the study of different process parameters under the stress field and deformation field distribution laws,to clarify the process parameters on the vertical and parallel to the stress and deformation on the weld.The results show that:whether vertical or parallel to the weld direction longitudinal stress is much greater than transverse stress,equivalent residual stress to tensile stress exists,with the increase in the number of layers of welding equivalent stress value will decrease,the depth direction of the residual stress is much larger than the material yield strength;heat input changes to the transverse residual stress has a greater impact on the longitudinal residual stress is smaller;residual stress with the preheating temperature of Increase in preheating temperature is first reduced and then increased trend,the model should not be preheated before welding temperature exceeds 200℃,double wire spacing of 15 mm when the residual stress value is small,the welding forming effect is better.The optimised process obtained by simulation was used to carry out double wire welding tests on Q390 low alloy high tensile steel plate butt structures.Through mechanical properties test and metallographic organization observation of welded j oints,it was found that the welded joints performed well;the blind hole method was used to test the residual stresses in the vertical and parallel weld directions,and the measured results were found to be consistent with the simulation calculations,which indicated the plausibility of the parameters of the finite element model and the double heat source model of double wire welding.In summary,this paper provides a systematic study of the stress and deformation of Q390 low-alloy high-strength steel twin-wire welded joints by means of numerical analysis,revealing the influence of different process parameters on the twin-wire welded stress and deformation fields,and verifying them experimentally,providing a mathematical method for the in-depth study of the twin-wire welding process.