Residual Stress Analysis Of Girth Butt Weld In Cast Steel Joint

Cast steel joints are mainly connected with hot-rolled tubes by welding.The residual stress generated by welding may reach the yield strength.It will affect the fatigue strength of the structure seriously.In recent years,the residual stress of girth butt weld has been extensively studied by scholars.The studies mainly include finite element simulation of temperature fields and stress fields,and the results are focused on the distribution of residual stress.The thickness of cast steel tubes is usually thicker than the hot-rolled tubes.Welding between cast steel tubes and hot-rolled tubes with different thickness is less studied.Based on the thermo-elastic-plastic theory,a numerical analysis model of G20Mn5 cast steel tube and Q345 hot-rolled tube with girth butt weld has been simulated and analyzed.Internal heat generation loading method was applied to simulate heat source.Lived-dead element technology was applied to simulate the whole welding process.Parametric analysis have been carried out on the hot-rolled tube's diameter to its thickness(d/t),the ratio of cast steel tube's thickness to hot-rolled tube's(T/t)and the thickness of hot-rolled tube's(t).The distribution of residual stresses along its length and circumferential direction have been pointed out.The effects of different parameters on residual stress and the residual stress range of the reference have also been provided.Following conclusions were acquired through the above analysis:(1)Internal heat generation loading method is more accurate than double ellipsoid heat source model for finite element simulation of G20Mn5 cast steel tube and Q345 hot-rolled tube with girth butt weld.(2)In the weld metal zone,with the increase of d/t,the residual compressive stresses along the length direction on inner and outer surface increased.The residual tensile stress along the circumferential direction on inner surface increased and the one on outer surface had no significant change.With the increase of T/t,the residual compressive stress along the length direction on the inner surface increased and the one on outer surface decreased.The tensile residual stress along the circumference direction on inner and outer surface had no significant change.With the increase of t,the residual compressive stress along the length direction on the inner surface increased.The residual tensile stress along the length direction on the inner surface increased.The residual tensile stress along the circumference direction on inner surface decreased and the one on the outer surface increased.(3)When the values of d/t,T/t and t were in the usual range,the maximum residual stress along the length direction on inner surface was compressive stress,the maximum range: 87.5-150N/mm2.The maximum residual stress along the length direction on outer surface was tensile stress,the maximum range: 115-155N/mm2.The maximum residual stress along the circumferential direction on outer surface was tensile stress,the maximum range: 205-245N/mm2.The maximum range of residual compressive stress along the circumferential direction on inner surface was 70-135N/mm2,the maximum range of residual tensile stress was 60-160N/mm2.