Research On Warm Drawing Process Of Q390A High-strength Steel V-shaped Stiffeners

The strength of high-strength steel is more than 500 MPa,compared with ordinary steel,the strength of high-strength steel has obvious strength advantages,it has a good application prospect in improving resource shortage,environmental pollution and improving safety of car body.High-strength steel at room temperature has bad plasticity and poor formability,forming parts often appear wrinkle,cracking and other defects,the application of high-strength steel material in car body structure is restricted.The paper research on the problems of wrinkling and cracking in cold forming of Q390 A high-strength steel V-shaped stiffeners,the warm drawing technology is put forward,and the V-shape stiffeners with excellent quality was obtained by raising temperature and improving the material plasticity.In order to study the influence of temperature on the properties of Q390 A material,the high temperature tensile test at 400? ~ 800? was carried out by using high temperature tensile equipment and Gleeble-1500 D equipment.The changes of stress-strain curves of materials under different temperature and tensile rate are analyzed,and the influence of temperature and tensile rate on stress-strain curves is obtained;through the observation of fracture morphology at different temperatures,the influence of temperature on the fracture mechanism of materials was analyzed.In addition,the microstructure and surface quality of the materials at different temperatures were analyzed,and the influence of temperature on the properties of Q390 A materials was analyzed.The forming die was designed with 3D drawing software,and the process parameters and the local fillet size of the punch were optimized by the finite element simulation software.According to the simulation results in the temperature range of 400? ~ 800?,and combined with the actual forming equipment conditions,the die pressing edge device was designed,and a complete set of V-shaped stiffeners forming die was prepared.Before forming,the law of heating and cooling need to be known,so as to control the forming temperature effectively.Through the current heating experiments,it is concluded that in the range of 7.3 ~ 8.5A/mm2 current density range,the sheet temperature can be controlled between 530? ~ 720?,the proportional relationship between the input current density and the equilibrium temperature.By measuring the cooling temperature curve of sheet,the temperature change of sheet at different temperature is mastered.Using the self-made die in the temperature range of 400? ~ 700? for forming experiment,the stiffeners under different conditions are obtained.The surface oxidation,crack,sheet warping degree,sectional thickness distribution,tensile strength,elongation and microstructure of V-shaped stiffeners were analyzed,it is concluded that when the forming temperature is controlled at 600?,the quality of V-shaped stiffeners is good,in addition,other problems in the forming process are analyzed.