| In light of environmental and energy problems,people are increasingly paying attention to how to achieve more lightweight automobiles.The application of low density high strength steel in automobile design is considered as a solution to meet the requirements of automobile safety and lightweight.However,the manufacture of such low-density and high-strength steels(Fe-Mn-Al-C series steels with high Al content)steel plates can not meet the requirements of the future automotive industry by using traditional cold stamping processes.The reasonable hot stamping process parameters of steel have also become a top priority.In this paper,the hot stamping process research on Fe-16Mn-10Al-1C low density high strength steel bonding theory,numerical simulation and related experiments.(1)Hot rolling and cold rolling tests were carried out on the experimental raw materials to make Fe-16Mn-10Al-1C low-density high-strength steel plate reach the thickness of 1.2mm required by subsequent tests,and the preparation of experimental materials was completed.(2)The thermal tensile tests of Fe-16Mn-10Al-1C low-density high-strength steel under different conditions were carried out,and the stress-strain relationship between the strain rate of 0.01s-1?1s-1 and the deformation temperature of Fe-16Mn-10Al-1C at650??950?was analyzed.It is concluded that the deformation stress decreases with the decrease of strain rate and the increase of temperature.At the same time,Johnson-Cook theoretical model and Arrhenius hyperbolic sinusoidal model were established on the basis of experimental data to study the rheological relations at high temperature of Fe-16Mn-10Al-1C low density and high strength steel.By comparison,the hyperbolic sinusoidal form of Arrhenius can describe the constitutive relations at high temperature of Fe-16Mn-10Al-1C low density and high strength steel to a better extent than the Johnson-Cook theoretical model.(3)Through the hot stamping test of Fe-16Mn-10Al-1C low-density high-strength steel at a stamping speed of 30mm/s and a temperature of 650??950?,it is found that its springback angle is much smaller than that under high temperature stamping conditions.For cold stamping,the rebound angle above 850°C is lower than 3°and far less than 12°,and the thickness is uniform,and the dimensional accuracy is high.(4)The finite element model of hot stamping process of low density high strength Fe-16Mn-10Al-1C steel U-shaped parts was established by using DEFORM finite element software.The effect of initial temperature,stamping speed and die temperature of Fe-16Mn-10Al-1C steel blank on the forming process was analyzed by finite element method.The analysis shows that the bottom temperature of the Fe-16Mn-10Al-1C hot stamping forming part is lower at the end of forming,the side wall temperature is higher,and the stress value of the forming part at the corners of the convex and concave molds is higher.Comprehensively considering the production cost,forming performance and dimensional accuracy of Fe-16Mn-10Al-1C hot stamping parts,it is concluded that when the initial temperature of the blank is 850?,the stamping speed is 30mm/s,and the initial temperature of the mold is 20?,satisfactory results can be obtained by hot stamping of Fe-16Mn-10Al-1C low density high strength steel. |
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