Numerical Analysis Of Residual Stress In Multi-pass Welding Of Q460High Strength Steel

As a new ultra-fine grained alloy steel, Q460high strength steel has the advantages ofanti-fatigue performance, good weld ability, high strength and good low-temperaturetoughness, whose welded thick-walled structures are widely used in construction machinery,bridge and other fields. In welding, due to uneven heating, residual stress is generated,which has significant effect on strength, fatigue restraint ability and crack. And, there existsmore complicated residual stress distribution mode in multi-layer and multi-pass welding.So far, however, the research for Q460high strength steel is focused on welding procedureand microstructure. There are few studies on welding residual stress, thus hindering thefurther application of Q460steel. In this paper, using the numerical simulation technology,the features of residual stress distribution in multi-pass welding of Q460steel areinvestigated through developing an adaptive finite element model, which provides thetechnical support and basic data for optimizing the process parameters in welding of Q460steel procedure, having an important academic and practical values.In this paper, three kinds of commonly used Q460steel welded joint modes, includingplate-plate butt-welded joint, pipe-pipe butt-welded joint and pipe-plate fillet joint, areselected to study the welding residual stress. Under different welding conditions, Q460steel welding experiments are carried out using CO2gas shielded arc welding to obtaingood weld formation, determining the optimal process parameters, and the residual stressare measured by means of hole-drilling method The moving temperature heat source modelbased on weld appearance was applied for describing the welding heat flux distributionmode. And, according to thermal-elastic-plastic theory, three dimensional finite elementmodels for multi-pass welding of Q460steel was established through ANSYS software.The residual stress fields in plate-plate butt-welding, pipe-pie butt-welding and pipe-platefillet welding were calculated and their distribution characteristics and the influence ofweld pass arrangement on them were analyzed.The results show that the calculated residual stresses in are in good agreement withexperimental data, indicating the accuracy and adaptibility of the developed model Inmulti-pass butt-welding of plates, large longitudinal tensile stresses were generated in theweld bead zone and its vicinity and their maximum peak value reaches466MPa, beinggreater than the yield stress of base meal. With distance form weld bead, tensile stressesdecrease sharply. For transverse residual stress, large compressive stresses appear in theweld zone and tensile stresses are generated near the weld toe, which have small value. And, with the increase of the weld pass, the high stress zone in plate-plate butt welding narroweddownFor multi-pass butt-welding of pipes, the difference of stress distribution along thecircumferential direction is small at other locations except arc-starting andarc-extinguishing positions. But, residual stresses on outside surface are much smaller thanthose on its inner surface.In pipe-plate fillet-welding, hoop residual stress in and near weld bead zone on outsidesurface of pipe is tensile one and axial residual stress is the compressive one. In and nearweld bead zone on inner surface of pipe, they are both tensile stress. Hoop and axialresidual stress on the surface of plate surrounded by pipe are both compressive stress,which are higher near the weld toe.