Study On The Integration Processes Of Hot Stamping- Quenching And Carbon Partitioning Of The Steel With The High Product Of Strength And Elongation

One of the effective approaches to increase the fuel efficiency and safety of automobile is reducing the weight of a vehicle. High-strength steel, which requires the use of hot stamping processes, is the most important material of weight reduction for the automobile industry. However, the existing hot-formed steel is unsatisfied for parts that request good crashworthiness. As a result, the present project aims at the development of automotive steels with a product of strength and elongation greater than 20,000MPa% and related forming-quenching integration processes.This paper was based on previous work.In order to fit the actual process, two factors that the amount of deformation(compression deformation after austenitizing) and the cooling rate were added. Therefore, the combination of independent research and development of experimental steel(94 #) developed two hot stamping- quenching partitioning integration process: Hot Stamping-Quenching Online Partitioning(HSQOP) and Hot Stamping-Quenching Dynamic Partitioning(HS-QDP). It focued on exploring the relationship from microstructure to properties depend on different deformation of the cooling rate and the performance of the steel treated by the HS-QDP. Results are as follows:The 94 steel were treated by forming-quenching integration processes using a physical simulation test machine Gleeble3500.The microstructure in 94 steel treated by forming-quenching integration processes was characterized by means of OM, SEM, EPMA, TEM and EBSD and its mechanical properties were investigated by tensile testing at room temperature.The Specimens treated by HS-QOP process the grain refinement with increasing deformation and thinning. Compared with the sample treated by previous process, the product of strength and elongation(PSE) of the samples treated by HS-QOP process can increase from 20088MPa?% to 26245MPa?%. When 15% strain deformation exist in the samples that PSE were up to 28783 MPa ?%. Higher content of the residual austenite in this process and it was characterized by thick massive, slender and fine granular film-like. With different deformation of samples tensile strength and elongation changed.HS-QDP process specimens major microstructure was the quenched martensite lath, its morphology and the diffraction pattern can be determined the presence of retained austenite.With dynamic partitioning to increase the cooling rate the martensite laths edge becomes curved, the width of the increased, the length of the shorter.Retained austenite primarily of a narrow film.Specimen of carbon-rich region between the martensite laths obvious. The optimum for the 9th(HS-QDP-15%-1 ℃ / s), 16.57% elongation, tensile strength of 1610 MPa, strong plastic product for 26678 MPa ?% more than 20000 MPa ?%.XRD detection methods for the content of retained austenite.94 steel stability and the carbon content of retained austenite steels have a close relationship. The average carbon content of austenite at the time of 1.10 wt.% Can be retained to room temperature, retained austenite TRIP effect under these conditions is remarkable. Follow in different condition the yield strength dissimilar, and the yield strength of the Specimens HS ~ QOP below HS ~ QDP. Specimen elongation and residual austenite conversion rate proportional relationship presents. Hot stamping the actual member, 22MnB5 parts of its strong plastic product for 10320 MPa ?%, only 10% elongation. After 94 # hot forming, the highest value of the product of strong plastic 16807 MPa ?%, elongation rate of 13.1%, compared 22MnB5 enhance the effect is remarkable.These conclusions show that the combination of self-designed experiments steel(94 #) developed by HS-QOP technology and HS-QDP process used in hot stamping field potential, compatibility, and high mechanical properties.