Numerical Simulation Research On Marine High-strength Steel Hybrid Laser-arc Welding

Hybrid laser-arc welding has great advantages compared with single laser welding or arc welding.It has a promising application prospect in the field of domestic marine high-strength steel welding.However,it will cost too much to study the technology of hybrid laser-arc welding based on experimental researches due to variable process parameters.Therefore,it is of great scientific value to study the marine steel hybrid laser-arc welding technology using numerical simulation technology.This dissertation conducts researches on hybrid laser-arc(MIG)welding of marine high-strength steel NV E690 using numerical simulation technology based on experiments.The temperature field and stress field of both hybrid single-pass welding and double-pass welding and the heat treatment after hybrid welding are realized with numerical simulation technology.The main research work of this dissertation is as follows:The experiments of hybrid laser-arc(MIG)welding of marine high-strength steel NV E690 with a thickness of 15 mm are carried out.The geometry of the weld cross-section and the residual stress on the surface of the weldment are measured,which are used to verify the accuracy of temperature field and stress field obtained by numerical simulation.The finite element simulation model of hybrid welding temperature field is established,and the simulation results of two kinds of heat-source model are compared.The temperature field of both hybrid single-pass welding and double-pass welding of the marine high-strength steel are obtained with the combined heat-source"uniform cone heat-source + column Gauss heat-source" which has more practical results.The simulation results are in accordance with the cross-section shape of the actual welding head.The temperature field of welding process is also studied.The finite element simulation model of hybrid welding stress field is established based on hybrid welding temperature field.The stress field of both hybrid single-pass welding and double-pass welding of the marine high-strength steel are obtained.The simulation results are verified by comparison with the experiment results and theory.The distribution of residual stress and the stress evolution of the welding process are analyzed.The differences of stress field between single-pass welding and double-pass welding are compared too.The heat treatment process for marine steel after hybrid welding has been developed and simulated by using numerical simulation technology,which effectively reduces the residual stress and deformation of the marine high-strength steel after hybrid laser-arc welding.The marine steel NV E690 hybrid laser-arc hybrid welding technology obtained in this dissertation has practical significance on the application of hybrid laser-arc welding in marine high-strength steel welding field.The established finite element model,such as combined heat-source mode,has guiding significance in the application of numerical simulation technology used in hybrid welding process researches.The temperature field and stress field obtained has reference value to the theoretical research of hybrid laser-arc welding.The heat treatment process can also be used as a reference for the optimization of the marine steel hybrid laser-arc welding process.