Effect Of High Temperature Austenitizing On Microstructure And Properties Of Dual Phase Steel

Duplex steel(DP)belongs to an important class of high tensile steel(AHSS).In terms of mechanical properties,DP steel exhibits no obvious yield point,high tensile strength and excellent formability.Therefore,the automobile industry continues to explore ways to improve the ductility and mechanical strength of dual-phase steels at the same time.As a result,a more suitable automotive steel for processing and forming has been developed.Dual-phase steel mainly contains two phases,one is hard martensite,and the other is soft ferrite.Ferrite acts as a matrix phase,which increases the elongation of the duplex steel.However,martensite as a reinforcing phase promotes the development of the tensile strength of duplex steel.The tensile strength and elongation of dual-phase steel are determined by the two-phase content and martensite morphology.Therefore,through optimized annealing process parameters,the dual-phase steel can exhibit good tensile strength and formability.The phenomenon that the stress-strain curve of dual-phase steel has no obvious yield point and the yield stress is relatively low is determined by the actual distribution of ferrite and martensite.In the annealing process of dual-phase steel,the austenite phase,which is the metastable phase,is transformed into martensite,while the ferrite remains unchanged,thus forming a dual-phase microstructure composed of ferrite and martensite.structure.The main goal of this paper is to prepare dual-phase steel with a good combination of mechanical strength and ductility.Therefore,the effect of high-temperature austenitization on the microstructure and mechanical properties of dual-phase steel is the main content of current research work.This research intends to obtain the DP steel annealing process parameters that have potential applications in industrial production.In the current research,the steel grade DP 780 is selected as the experimental steel,and the microscopic morphology and mechanical properties of DP steel are observed using equipment such as metallographic microscope and universal material testing machine,and through Origin and Image-Pro Plus,etc.The software extracts and analyzes the experimental data.Initial annealing,isothermal annealing,continuous annealing and rapid heating annealing are all common annealing processes.For this reason,this article explores the high-temperature austenitization phenomenon in the above four annealing methods.The microstructure of ferrite and martensite includes grain size,volume fraction,phase transformation and so on.The current research not only explored the above content,but also analyzed its influence mechanism.The tensile strength,Vickers hardness,and stress-strain curve of dual-phase steel are all affected by the annealing process design.Therefore,the current research focuses on analyzing and comparing the effects of annealing process parameters on the mechanical properties of dual-phase steel.Through current data and analysis,we can know that the austenitizing temperature should not be set too high in the actual annealing process of dual-phase steel,and the appropriate slow cooling temperature should be selected from the temperature range of 640??670?,and the overaging temperature should Control the temperature below 350 ? ?320 ?.This not only meets the comprehensive requirements of mechanical processing for tensile strength and elongation,but also ensures industrial production efficiency.The rapid heating and annealing experiment proves that reducing the grain size of DP 780 dual-phase steel can be achieved by rapid heating,and rapid heating and annealing can further improve the tensile strength of DP 780 dual-phase steel and reduce energy consumption.