Development Of 370MPa-750MPa Grade Automotive Structural Steel

In recent years,with the rapid increase in automobile sales,the auto parts industry and the required steel have continued to increase.As the car is subjected to various stresses such as impact and torsion during driving,and the overload phenomenon is more common,as the "backbone" of the car,the service conditions of the frame are quite demanding,so the requirements for the manufacturing materials are very strict.This kind of material not only requires high strength,but also requires good plasticity,toughness and cold bend formability,and is a typical high-strength low-alloy steel.Automobile longitudinal beams,beams,suspension beams,front and rear axles and other parts are generally made of automobile frame steel.However,with the continuous improvement of market requirements,the mechanical properties and lightweight of automobile frame steel can no longer meet the current demand.Therefore,combined with Baotou Steel's process,technology and equipment conditions of2250 mm Hot Rolling Production line,through the basis and experience of 370MPa-510 MPa grade automobile steel industrial trial production,the research focuses on 600MPa-750 MPa grade high strength and light weight automobile beam steel,which provides theoretical and practical reference for the production and application of this kind of steel.In this paper,through industrial trial production,reasonable chemical composition,technological process and trial production process are formulated.The properties of SAPH370,SAPH440 and BT510 L produced not only meet the requirements of the standard,but also control the yield-strength ratio according to the special requirements of users to realize batch production.Through laboratory research,industrialized trial production and process optimization,high strength BT610 L and BT700 L beam steels with fine grain,good strength and toughness and good forming properties were successfully developed by low carbon,Nb and Ti alloying design.Through process control,the base of producing BT610 L and BT700 L steel with the same composition is realized,the production cost is reduced and the product benefit is improved.The quantities of SAPH370,SAPH440,BT510 L and BT610 L produced and sold are 428,6411,63953 and 18737 tons respectively.The qualified rate of batch production is 90%,92%,98% and 97%,which meet the acceptance criteria.