Research On Thermal Effect Of Cold Stamping Deformation And Warm Forming Properties Of Automobile High Strength Steel

High strength steel in stamping simulation of springback value and the actual car there is a big difference,because the identity of the higher intensity,compared with ordinary steel,deformation heat and friction to tropical temperature rise effect is more apparent,and the traditional stamping simulation are not considered in the process of high strength steel material,the influence of the temperature rise for this article,through research in the process of punching deformation heat effect,Thermal coupling simulation method is adopted to improve the accuracy of springback simulation.In addition,there are serious springback defects in the stamping of high strength steel,which greatly affect the quality control of parts.The application of warm forming in high strength steel is less.This paper uses warm forming technology to reduce the springback problem of high strength steel and verify the feasibility of warm forming technology.In this paper,the deformation thermal effect and warm forming process of ultrahigh strength steel in cold stamping are studied.The main research contents include:(1)in this paper,the subject background significance and super-high strength steel development course of the development of the summary sheet stamping finite element simulation and stamping simulation of finite element theory,the simulation process,heat transfer equation,such as theoretical basis,summarized at home and abroad for super-high strength steel heat deformation study of friction and super-high strength(2)The typical automobile high strength steel QP980 is selected as the research line,and the temperature environment in the stamping process is simulated by using the constant temperature tensile experiment,including the warm temperature environment,to lay a foundation for the trial production of warm forming.The designed temperature of constant temperature tensile test was 20℃,60℃,100℃,150℃,200℃,300℃,400℃,450℃,500℃ and 600℃,and the experimental strain rates were set as 1×10-2s-1,1×10-3s-1 and 1×10-4s-1.N-h constitutive equation was obtained by fitting the tensile curve from 20℃ to 150℃,which can accurately describe the yield behavior of QP980 high strength steel at this temperature range.According to the experimental curve,the suitable temperature for warm forming is500℃ and 600℃.(3)The fitted N-H constitutive simulation was input into Abaqus software for tensile experiment simulation.The maximum temperature obtained appeared in the middle of the sample with the largest deformation,reaching 52.56℃,indicating that the thermal effect of deformation was relatively obvious.The comparison between the tensile curves of simulation and experiment showed that the fitted N-H constitutive was relatively accurate.(4)Select a typical high-strength steel threshold parts,carry out process design and finally obtain the finite element simulation model.Compare the results of thermal coupling simulation analysis and traditional simulation analysis considering the thermal effect,and take the springback value measured by actual stamping as the benchmark,the springback calculation accuracy is improved by 25.51%.(5)For two typical high strength steels QP980 and DP780,it is determined that 500℃ is more suitable for the warm forming of these two kinds of high strength steels,and the warm forming can reduce the rebound value,which verifies that the microstructure change of the parts after warm forming is small and the mechanical properties meet the requirements of use.