Experiment Al Research On Hot Forming Key Process Parameters Of Ultrahigh Strength Steel B1500HS

With the increase of the international oil price as well as the concept “Energy Conservation and Emissions Reduction” putting forward, the whole society has urgent demand for automotive light weighting. Ultra high strength components of hot stamping can ensure the safety of vehicle performance, and it can also realize the demand of light weighting. The hot stamping technology is an effective way to relieve the energy crisis,reduce the environment pollution and achieve energy conservation and emissions reduction. Hot stamping technology is the process that ultra high strength steels are heat above the austenitizing temperature and keep some time, then quickly move to the die for forming and quenching. The forming components can achieve absolutely martensite microstructure and above 1500 MPa tensile strength, which reduces the weight of the parts greatly under the condition of guaranteeing security.The reasonable design of process parameters in hot stamping can improve the mechanical property of the part and eliminate the defects such as uneven thickness distribution, wrinkle, cracking and springback, which guarantee the qualified rate and stability of the stamping parts. It is necessary to study and optimize the process parameters in hot stamping to obtain high quality parts. The key process parameters in hot stamping include: heating process parameters, stamping process parameters and pressure quenching process parameters. The main contents of this paper are as follows:1) The experiments were conducted to study the heating parameters(austenitizing temperature and holding time) of ultra high strength steel B1500 HS. It was researched that the influence rules of the austenitizing temperature and holding time on tensile strength, hardness, and microstructure of ultra high strength steel after quenched. The results showed that when the austenitizing heating temperature was 910 ℃ and the holding time was 4 minute,the sheets after quenching obtained uniform lath martensite,which had the best mechanical properties.2) The experiments were conducted to study the stamping parameters(initial deformation temperature) of ultra high strength steel B1500 HS. The influence rules of initial deformation temperature on the limit drawing ratio(LDR) and cup drawing value(IE) were studied. What’s more, the influence rules of initial deformation temperature on on tensile strength, hardness, microstructure of ultra high strength steel after quenched were studied. The results showed that when initial deformation temperature was 700℃,ultra high strength steel had the best forming performance, and the ultra high strength steels after quenching obtained the mechanical properties which satisfied the requirement of practical hot stamping production.3) The experiments were conducted to study the quenching parameters(quenching cooling rate) of ultra high strength steel B1500 HS. The relationship between quenching cooling rate and water flow rate during continuous hot forming process was studied through the use of temperature control system set up. The influences of the quenching cooling rate on tensile strength, hardness, microstructure of ultra high strength steel after quenched were studied. It was showed that the reasonable quenching cooling rate was from 43.09℃/s to 45.3℃/s.