Study On High Temperature Deformation And Continuous Cooling Of Non-quenched And Tempered Steel 49MnVS3

Non-quenched and tempered steel 49MnVS3 can achieve or better than the properties of quenched and tempered steel without tempering treatment.As an energy-efficient and energy-saving steel,it has the advantages of reducing energy consumption and saving energy.In order to optimize the rolling and cooling process,this study used a Gleeble-3500 thermal simulation tester to perform a thermal compression test on49MnVS3 steel,by controlling different cooling rates,combing with analysis of microstructure and mechanical properties.The deformation resistance model was plotted and the processing drawing and the dynamic continuous cooling transformation curve of49MnVS3 steel?hereinafter referred to as"CCT curve"?was obtained.Based on the results of thermal simulation experiments,the experimental parameters were optimized.The two-high mill was used to control rolling and control cooling.The influence of deformation temperature,deformation degree and cooling rate on the microstructure and properties of 49Mn VS3 steel was obtained.The deformation process of steel provides a more complete theoretical basis and technical parameters.The main conclusions are:The stress-strain curve of 49MnVS3 steel obtained by thermal compression test.As the deformation temperature decreased and the deformation rate increased,the deformation resistance increased.With the increase of the deformation rate,the transformation time of austenite to ferrite and pearlite is shortened,and the grain of the microstructure is refined and the size is reduced.At lower deformation temperatures and higher rates of deformation,dynamic recrystallization occurs more easily.The nonlinear deformation resistance model of 49MnVS3 steel was constructed using the Inoue Katsuro model,Hensel-Spittel model and Zhou Jihua-Guan Kezhi model.Among them,using the Zhou Jihua-Guan Kezhi model obtained the highest degree of fit between theoretical and measured values of deformation resistance,and the fitting value is 0.95.The deformation activation energy of the 49Mn VS3 steel is calculated as 342.5kJ/mol.The flow stress predicted by the established constitutive equation is basically consistent with the experimental data.The thermal processing map is plotted.The instability regions are mainly distributed in the high-temperature and low-strain regions,while the maximum power dissipation regions are mainly distributed in the upper-middle region of the thermal processing map.The results show that the optimal deformation process parameters of 49MnVS3 steel are deformation temperature of 820⁸50°C and strain rate of 40-50 s^-1.Ac₁ and Ac₃ of the 49Mn VS3 steel's CCT curve are 741°C and 803°C,respectively,and the"nose tip"temperature is 550°C.Continuous cooling in the temperature range from 800°C to 550°C results in lamellar pearlite and ferrite structure;only pearlite forms from 550°C to 510°C;bainite forms from 410°C to 320°C;and martensite forms from300°C to 180°C.As the cooling rate increases,the hardness increases slowly and then increases linearly.49MnVS3 steel at deformation temperature of 850°C,deformation degree of 30%,cooling rate of 10°C/s for hot compression,its uniform distribution of the organization,the steel ferrite content is less.Rolling at 850°C with 30%deformation and 10¹2°C/s cooling rate yields a small amount of island-like ferrite and fine pearlite structure with room-temperature tensile yield strength of about 650 MPa,tensile strength 900 MPa,elongation of about 16%,its comprehensive mechanical properties than the original sample increased by 6%.The best controlled rolling and cooling process of 49MnVS3steel is as follows:the sample is heated to 1100°C,kept for 10 minutes,then cooled to850°C at a cooling rate of 5°C/s,the deformation is 30%;after the final rolling,it is10¹2°C/s cool down to room temperature.