Optimize On The Process Of Heat Treatment And Forging Of MC3 Steel For Cold Roll

In order to further improve the service life of cold rolls,In this paper,the heat treatment process and forging process in the manufacturing process of MC3 type cold roll were studied.The influence law of heat treatment and servo forging on its microstructure and properties was explored,which provided theoretical and experimental basis for the optimization of the manufacturing process of MC3 cold roll.In this paper,Jmatpro software was used to simulate the equilibrium phase diagram of MC3 steel,and heat treatment and servo forging process were formulated based on this.In this paper,the finite element analysis method was also used.The servo forging process was optimized with the help of Deform-3D software simulation analysis and verified with experiments.At the same time,The influence laws and mechanisms of quenching temperature,tempering temperature,isothermal spheroidizing temperature and servo forging reduction ratio on microstructure and properties of MC3 steel were studied by optical microscope(OM),scanning electron microscope(SEM),energy spectrometer(EDS),X-ray diffractometer(XRD),universal testing machine,impact testing machine,friction and wear testing machine,hardness tester,etc.The main conclusions are as follows:(1)The equilibrium phase diagram of MC3 steel was simulated by Jmatpro software,and the heat treatment process was developed based on it.At room temperature,the equilibrium phase composition of MC3 steel is mainly composed of ferrite(88.3%),cementite(6.64%)and carbonitride(3.82%),and its austenite critical transformation temperature A_c1 and A_cm are758.5°C and 960.8°C.(2)Combined with the formulated quenching heat treatment process,the effects of quenching treatment on microstructure and properties of hot rolled annealed MC3 steel were analyzed through experimental study.The microstructure of the quenched MC3 steel is mainly composed of crypto-acicular martensite,undissolved M₃C carbides and retained austenite.With the increase of quenching temperature,the crypto-acicular martensite gradually coarsens,the dissolved amount of carbides increases gradually,and the content of retained austenite gradually increases.When quenched at 960°C,the carbides in the MC3 steel structure are almost completely dissolved,the martensite is sharply coarsened,and the content of retained austenite is sharply increased.In terms of performance,with the increase of quenching temperature,the hardness,strength and wear resistance of MC3 steel show a trend of first increase and then decrease.When quenched at 920?,its hardness reaches the maximum value of 63.8HRC,and the compressive strength and yield strength also reach the maximum value of 3148.4MPa and 2322.4MPa,respectively.At this time,the wear resistance is the best,and the average friction coefficient and volume wear amount are 0.61 and 0.164mm3,respectively.(3)Combined with the formulated tempering heat treatment process,the effects of tempering treatment on microstructure and properties of hot rolled annealed MC3 steel were analyzed through experimental research.The microstructure of MC3 steel tempered at550?750?after quenching at 920?is all tempered sortensite.With the increase of tempering temperature,the morphology of precipitated carbides gradually changes from flakes to short rods and granules,and the distribution is more uniform and dispersed.At the same time,the?-phase matrix gradually recovers and recrystallizes,the original crypto-acicular martensite orientation disappears,and the dislocation density decreases continuously.When tempered at 750°C,the equiaxed ferrite grows and coarsens,and the granular carbides also aggregate and grow.In terms of mechanical properties,with the increase of tempering temperature,the hardness and strength of MC3 steel show a decreasing trend,while the ductility and toughness show a gradually increasing trend.When tempered at 700?,the hardness,tensile strength,yield strength,elongation and impact energy of MC3 steel reached39.2HRC,902MPa,803MPa,11.9%,and 9.8J,respectively.At this time,the comprehensive mechanical properties of MC3 steel were the best.(4)The servo forging process of MC3 steel was analyzed by finite element method,and the optimized forging process was obtained and verified by experiments.Deform-3d software was used to simulate the servo forging process.As the reduction rate increases,the average temperature of the forging after forging gradually decreases.When the reduction rate is 25%,only about 52%of the forging area is above 850?With the increase of the reduction rate,the required forging load increases gradually.When the reduction rate is 25%,the forging load increases sharply.However,with the increase of the reduction rate,the average equivalent strain of the forging gradually increases,and the equivalent strain of the core of the forging is higher than that of the edge of the forging.When the forging reduction rate is 20%,the overall equivalent strain of the forging is All reach more than 0.2,and the forgings are completely forged.(5)Combined with the formulated isothermal spheroidizing annealing heat treatment process,the effects of isothermal spheroidizing annealing on microstructure and properties of hot rolled annealed MC3 steel were analyzed through experimental study.When the annealing austenitization temperature is low(760?),there are still a lot of lamellar carbides in the structure of MC3 steel.With the increase of annealing austenitizing temperature,the spheroidization rate and spheroidization degree of carbides gradually increase.However,when the annealing austenitization temperature reaches 850°C,a small amount of flaky carbides will be formed in the structure.In terms of mechanical properties,with the increase of annealing austenitizing temperature,the overall hardness and strength of MC3 steel show a decreasing trend,while the elongation shows an increasing trend,and the change range is large between 760 and 790°C.When the isothermal temperature is between 660-720?,MC3 steel can get good spheroidized structure,and the spheroidization effect is the best when the isothermal temperature is 700?.With the increase of isothermal temperature,the hardness and strength of MC3 steel showed a downward trend as a whole,while the elongation showed a gradually increasing trend.(6)Combined with the optimized quenching and tempering heat treatment process,the effects of its on the microstructure and properties of hot forging annealed MC3 steel were analyzed through experimental research.Compared with hot-rolled MC3 steel,the MC3 steel after servo forging is more fully recrystallized,the grain size and carbide size are smaller,and the structure is more uniform.The compressive strength,yield strength and hardness of the hot-rolled annealed MC3 steel which quenched by the optimized quenching heat treatment process are 3148.4MPa,2322.4MPa,and 63.8HRC,respectively.However,the compressive strength,yield strength and hardness of hot forged annealed MC3 steel which quenched by the optimized quenching heat treatment process are 3212.0MPa,2479.9MPa,and 64.3HRC,respectively.The tensile strength,yield strength,elongation,impact energy and hardness of the hot-rolled and annealed MC3 steel which tempered by the optimized quenching and tempering process are 902MPa,803MPa,11.9%,9.8J,and 39.2HRC,respectively.While the tensile strength,yield strength,elongation,impact energy and hardness of hot forged annealed MC3 steel which tempered by the optimized quenching and tempering process are 922 MPa,861 MPa,14%,11.7J,and 40HRC.