Research On The Control Of Microstructure And Properties Of F45MnVS Non-quenched And Tempered Steel Half Shaf

The rapid development of the automotive industry has brought enormous pressure to energy,and energy conservation and consumption reduction are inevitable trends in automotive production.The use of energy-saving and environmentally friendly steel for automotive production is an effective method of energy conservation and consumption reduction.Non quenched and tempered steel,without undergoing quenching and tempering treatment in the production process,can effectively save energy,reduce emissions,and reduce costs,making it a research hotspot in the current automotive field.As one of the core components of the automotive transmission system,the quality and performance of the half shaft have a crucial impact on the safety and performance of the vehicle.Non quenched and tempered steel,as a high-quality steel with high strength and toughness,can effectively improve the load-bearing capacity of the half axle,and its application in automotive half axles is becoming increasingly widespread.In this paper,a kind of F45Mn VS non quenched and tempered steel for automobile half axle is studied.F45Mn VS is a ferritic+pearlitic non-quenched and tempered steel,it lays a foundation for the optimization of the hot working process of F45Mn VS non quenched and tempered steel and the application of F45Mn VS non quenched and tempered steel in the manufacturing of automobile half shafts.By comparing the microstructure and properties of non quenched and tempered steel half shafts at home and abroad,the key influencing factors on the static torsional properties of F45Mn VS non quenched and tempered steel half shafts were studied.Research has found that the strength of the core matrix structure and the depth of the quenched layer of the half shaft are key factors for quality control of the half shaft parts;After quenching the surface of the half shaft,there is a significant layering of microstructure and properties.The layering parameters have a significant impact on the static torsional performance of the half shaft.The weak point of the half shaft torsional failure is located at the junction of the quenching transition zone and the core matrix structure,and the strength of this area will significantly affect the static torsional performance of the half shaft;The transition fillet between the half shaft spline and the rod has stress concentration,which decreases with the increase of the fillet.The maximum stress position does not occur at the tangent point between the transition arc and the rod,but at a certain position within the transition arc.The phase transformation law and grain growth behavior of F45Mn VS steel were studied through heat treatment experiments and hardness testing.The phase transformation temperature A_c1 of F45Mn VS steel is about 725℃and A_c3 is about 775℃.The grain growth behavior of F45Mn VS steel is mainly affected by the heating temperature,and the grain size significantly increases with the increase of heating temperature.The grain growth model of F45Mn VS is=800.476·^0.04183·0)^-38004.13/,which has high prediction accuracy.The relationship between the microstructure and properties of F45Mn VS non-quenched and tempered steel was studied through heat treatment experiments.The results showed that the microstructure of F45Mn VS non-quenched and tempered steel in the half shaft is usually ferrite+pearlite+sorbite,troostite.The microstructure ratio is the main factor affecting its strength and hardness,and the microstructure ratio is mainly affected by the cooling rate.With the increase of cooling rate,the content of ferrite and pearlite decreases,sorbite and troostite increase,and the strength and hardness of the experimental steel increase,the plastic change is relatively small;The size of pearlite clusters has a certain impact on the mechanical properties of experimental steel.As the austenitizing temperature increases,the original austenite grains grow,and the corresponding size of pearlite clusters also increases.The strength and hardness of experimental steel increase,while the elongation and cross-sectional shrinkage decrease.The surface decarburization behavior of F45Mn VS steel was studied through heat treatment experiments,and the influence of hot working conditions on the surface decarburization of F45Mn VS steel was revealed.The results show that at lower heating temperatures,the thickness of the decarburization layer increases with the increase of temperature,reaching its maximum value at 1200℃.After increasing the heating temperature to 1250℃,the decarburization layer thickness decreases due to the intensification of surface oxidation of the experimental steel at high temperatures;The insulation time has little effect on the thickness of the decarburization layer on the surface of the experimental steel.The decarburization layer thickness shows a parabolic relationship with the insulation time,gradually increasing with the extension of the insulation time,and the increasing speed gradually slows down.The final rolling process of F45Mn VS steel and obtained the dynamic CCT curve of the experimental steel was studied through thermal simulation experiments.The results showed that the final rolling temperature and post rolling cooling rate have a significant impact on the microstructure and properties of F45Mn VS non-quenched and tempered steel.The increase in final rolling temperature leads to an increase in the size of pearlite clusters,a decrease in the content of ferrite and pearlite P,an increase in the content of sorbite and sorbite,and an increase in hardness;The increase in cooling rate after rolling gradually reduces the size of ferrite and pearlite,while also reducing the content of ferrite and pearlite and increasing hardness;When the cooling rate is increased to 2℃/s or above,the experimental steel begins to precipitate bainite.The high temperature deformation behavior of F45Mn VS steel was studied through thermal simulation experiments,and the influence of hot deformation conditions on the microstructure and properties of the experimental steel was revealed.The decrease of initial heating temperature,low deformation rate and high deformation temperature will promote the dynamic recrystallization of the experimental steel;The thermal deformation conditions affect the grain morphology by affecting the degree of dynamic recrystallization,leading to changes in the microstructure proportion of the experimental steel and affecting its mechanical properties;The decrease of the initial heating temperature,the increase of the deformation amount and the decrease of the deformation temperature make the experimental steel pearlite cluster size decrease,the ferrite and pearlite content increase,the soxhite and taustenite decrease,and the hardness decrease;the increase of the deformation rate will make the experimental steel pearlite cluster size decrease significantly,but it has no significant effect on the hardness of the experimental steel.