Study On Heat Treatment Process Of Medium Manganese TRIP Steel

With the development of the automotive industry,more and more attention has been paid to the lightweight and safety of automobiles,and the third-generation advanced high-strength automotive steel with high strength and plasticity came into being.In this paper,Fe-7Mn-2Al-0.2C medium manganese steel is designed to study the effect of different rolling methods and different heat treatment processes on the microstructure and mechanical properties of the experimental steel.After the hot-rolled experimental steel is subjected to different quenching temperatures,the structure is composed of lath martensite,ferrite and residual austenite.The available tensile strength of 920-1310 MPa and elongation of more than 21%.As the quenching temperature increases,the tensile strength gradually increases,the elongation increases first and then decreases,and the strong plastic product also shows a trend that increases first and then decreases.After the hot-rolled steel undergoes different quenching and holding times,the tensile strength of the steel is 1180?1200 MPa,and the elongation range is 32?44%.With the extension of the holding time,the elongation increases first and then decreases,and the strong plastic product also shows the same trend.After the hot-rolled steel undergoes different quenching and holding time at 720?,ferrite,metastable austenite and a small amount of martensite structure are obtained.A better heat treatment process is to hold at 720? for 1 h,then quench and temper.The residual austenite volume fraction is about 34%,the tensile strength of hot-rolled steel is 1180 MPa,the elongation is 44%,and the strong plastic product reaches 52 GPa%.After the cold-rolled medium-manganese steel undergoes different annealing temperatures,the structure is composed of retained austenite,ferrite and variable temperature martensite.Obtained a tensile strength of 920?1200 MPa and an elongation of 21?51%.With the increase of annealing temperature,the tensile strength showed a gradual increase trend,and the elongation and strong plastic product showed a trend of increasing first and then decreasing..After the cold-rolled steel has undergone different holding times at 700?,the tensile strength obtained does not change much,and the elongation and strong plastic product show a trend of rising first and then decreasing.The cold rolled medium manganese steel adopts the austenite reverse transformation heat treatment process.The preferred heat treatment process is to incubate at 700? for 1 hour and then air-cool to room temperature.After heat treatment,ferrite and retained austenite islands are obtained.The volume fraction of retained austenite is 29%.The best mechanical properties of cold-rolled steel are tensile strength of 1100 MPa,elongation of 51%,and strong plastic product of reaches 56 GPa%.