Research On Quenching Process Key Parameters Of Hot Stamping And Design The Temperature Control System

Hot stamping with ultra-high strength steel is the innovative technology and one of important ways to reduce vehicle weight and achieve energy conservation without sacrificing safety.The quenching process affected by many factors of hot stamping is the core of deciding the microstructure transformation and quality of parts,and the quenching tools is the basis of carrying out the right process.The ultra high strength steel B1500 HS was selected in this paper.The design of hot stamping die,quenching key parameters and the develop of the automatic cooling temperature control system were researched by theory and experiments,besides,the quenching process key parameters include holding press,holding time and cooling water velocity.(1)The mathematical model of the key structure parameters of die was set up based on the heat transfer theory,besides,the key structure parameters of die include the diameter of cooling pipe d and the distance between center of pipe and die surface H.The coupled thermal–mechanical simulation model for multiple stamping cycles was set up to predict and analyze the cooling ability of die designed by the mathematical model.The results show that the parameters of water channel can meet the use requirements when d is 10 mm and H is 20 mm.(2)An adjustable press and on-line temperature measuring device was developed to research the quenching process parameters including holding pressure,holding time and cooling water velocity during hot stamping.The influence rule and optimal range of the quenching process parameters were got depend on quality about mechanical properties and microstructure after quenching.The results show that holding pressure is no less than 0.5MPa to get fully martensite and greater than or equal to 15 MPa to get high efficiency for 1.2mm B1500 HS.In order to improve the production efficiency,the optimal holding time is 10 s when the initial deformation temperature is 850 ?.In order to meet the requirement of the critical rate and maintain the temperature dynamic balance,the cooling water flow rate is at least 5L/min.(3)According to the requirement of cooling rate of blank,and in order to improve the cooling uniformity and the versatility of cooling system,an automatic temperature control system with high precision temperature closed loop control for hot stamping was developed.The results show that the system can guaranteed fully martensite transformation and get quenching uniformity.The hardness of part is500 HV after quenching,which meets the requirements of hot stamping parts.