Research On Hot Stamping Process Of High Strength FeCrNiMo Steel Box Part

High-strength FeCrNiMo steel has high strength,poor plasticity and is not easy to be formed.Hot stamping forming technology is an important method to make it formed.Hot stamping forming technology is to heat and hold the high-strength steel plate to make it completely austenitized,then put it into the mold for forming,and after forming,the cooling water channel in the mold is quenched by water for holding pressure.The material studied in this paper is high-strength FeCrNiMo steel,and the true stress-strain curve of this material at high temperature is obtained by using Gleeble3500 hot compression simulator.The Arrhenius high-temperature constitutive model is fitted to the experimental data using Origin software and its accuracy is verified.The length versus temperature curves of high-strength FeCrNiMo steel were obtained using a thermal expansion meter,and the phase transition temperature of the material was calculated.The thermal diffusion coefficient of the material was measured using a laser thermal conductivity meter and the thermal conductivity and specific heat capacity at different temperatures were calculated.The billet dimensions of the given box are designed and a simulation model of 1/4hot stamping of a box-shaped part of high-strength FeCrNiMo steel is established using ABAQUS simulation software.A combination of process parameters is selected for simulation,and the temperature field distribution,stress field distribution and thickness distribution of the sheet at different stages under this combination of process parameters are obtained.The analysis of the simulation results led to the conclusion that in the forming stage,the thickness thinning rate at the end of forming is less than 30% and the sheet does not rupture;in the quenching stage,the quenching rate is greater than the critical cooling rate,the martensite density is higher and the sheet strength meets the requirements.Simulation of hot stamping forming of box-shaped parts of high-strength FeCrNiMo steel with different process parameters was designed using the single variable method.Using the simulation scheme of ABAQUS simulation software,it is concluded that the higher the initial temperature of the sheet,the smaller the maximum equivalent force and the smaller the thickness thinning rate;the higher the initial temperature of the die,the smaller the maximum equivalent force and the smaller the thickness thinning rate;the larger the stamping speed,the smaller the maximum equivalent force and the larger the thickness thinning rate.The combination of process parameters was optimized by comparing the results.The microstructure and mechanical properties of the box parts after forming were analyzed by hot stamping experiments with the optimal process parameters of the simulation results.The experimental results show that the hardness of the box parts after hot stamping is much higher than that of the rolled steel plate,and the internal structure is transformed into strip martensite.The unidirectional tensile test proved that the tensile strength and yield strength of different parts of the box parts produced by the combination of process parameters meet the requirements.