Research On Laser Welding Technology Of High Strength Steel For Vehicle

Automotive lightweight is the direction of future development.Improving the strength of steel and reducing the thickness of steel is the way to achieve this goal. Therefore, high strength steel materials applied in the car will have a good application prospects. Existing resistance spot welding method has the problem of a large area of overlap, which will increase the automotive weight, and the comprehensive performance of the welded joint is weak. Meanwhile, the resistance spot welding method can’t obtain satisfactory welding quality for high strength steel. In this paper, a laser welding method is proposed to solve the problem of high strength steel welding and the research on the laser welding of DP590、D780 materials, which is about to be used in a large amount, is carried out. Taking weld appearance, hardness and tensile property as the test index, the optimization process area and the change rule are determined by orthogonal test design method and response surface method. The weld orthopedic process of DP590 will be studied on the basis of that. The abaqus software was used to simulate the process parameters and then the actual test was carried out.There are so many influencing factors in the process of laser welding that qualitative analysis of the influencing factors of welding is carring out. What are the main influencing factors will be concluded. Then the main factors affect the change of microstructure and mechanical properties of the weld joints. According to the morphology,microstructure and mechanical properties of the weld morphology, the laser butt welding process area of DP590 was determined. Based on the research of DP590 material, the technology of DP780 laser welding is studied. The main factors influence the changes of the weld appearance by using the method of single factor optimization the main, which can determine the parameters of the forming process and the parameters related to penetration of the weld. Completing Response surface analysis and optimization of process parameters by means of Design-expert software. According to the mathematical model and the target range of penetration index for further optimization, the welding seam of exceeding the strength of the base metal will be obtained in the optimized process area.After laser but welding of DP590 material, there are some deformation, and the welding seam will be corrected by laser scanning method. The temperature field of DP590 laser butt welding will be simulated by abaqus, and then the model parameters of the heat source model will be sued to the simulation of the subsequent scanning orthopedic process. The simulated numerical correction and the actual orthopedic degree will be calculated. The above results will show that the simulation parameters can be used in the actual orthopedic process and it greatly reduced the time and cost of orthopedic technology.The above research results will provide practical guidance for the future laser welding and post welding correction of DP590 and DP780 materials.