Simulation Analysis Of Local Induction Tempering Process Of 30CrMnSiNi2A Thread Parts

Induction heating technology,which has a series of advantages,such as fast heating speed,high heating efficiency,environmental protection and easy to realize mechanization and automation,therefore,have been rapidly developed in recent years.The use of high frequency induction heating to replace the backward lead bath tempering process has become the development trend in the local tempering of 30CrMnSiNi2 A steel thread parts.Through the combination of numerical simulation and experimental method to determine 30CrMnSiNi2 A steel thread parts local inducrtion tempering process parameters has important implication for using environmental protection,high efficiency induction heating system instead of traditional lead bath tempering processand acquiring high comprehensive performance of 30CrMnSiNi2 A steel thread parts.In this paper,based on the numerical simulation of electromagnetic-temperature field of 30CrMnSiNi2 A steel thread parts induction heating,the numerical model for 30CrMnSiNi2 A steel thread parts local induction tempering process has been established,and the influence of process parameters on 30 CrMnSi Ni2A steel induction heating has been explored,and the optimized design of induction coil for 30CrMnSiNi2 A steel thread parts also has been carried on,finally,the process parameters of local induction tempering of 30CrMnSiNi2 A steel thread partsdetermined combination the microstructure and property of 30CrMnSiNi2 A steel during induction heating.According to the experimental analysis,the following conclusions are drawn:(1)The numerical simulation of 30CrMnSiNi2 A steel induction heating process,including the establishment of entity model and thermal physicalparameter model of 30CrMnSiNi2 A material,the meshing of solid model,boundary loading condition and solving steps setting.The comparison between the numerical simulation results and the measurement results shows that the numerical simulation results are reliable and have a certain guiding significance for practical operation.(2)The induction heating process,the workpiece surface temperature quickly reaches the phase transition temperature,after maintain a stable period in the transition point,temperature curve shows different trends;current density value is positively related with the magnetic field strength value,which directly affect the final heating temperature;the current frequency will affects the penetration depth of the material,thereby affects the temperature difference between the surface and the the center during induction heating.High frequency can rapidly improve the surface temperature of material in a very short period of time,and improve the thermal efficiency,however,the influence of high frequency increasing on temperature becomes smaller and smaller,therefore need to be comprehence consideration in frequency selection;influence of induction coil thickness on the temperature same with current density,the design of coil induction coli thickness mainly focus on theconsideration of power loss of induction system and economic sensors.(3)The induction coils of 30CrMnSiNi2 A steel thread parts local tempering were optimized,the optimized induction coils with rectangular cross section and rectangular section size is 12 × 6 mm,coil wall thickness is 1 mm,induction coils internal diameter is ?20 mm,turns number of induction coils is 2,coil 1 locationfactor 7)1 is 34.5 mm,coil 2location factor7)2is 64 mm,the interval of two coilsis 5.5 mm.(4)The microstructure morphologies of lead tempering and induction tempering are basically the same,and both microstructure keep the morphology of the tempered martensite lath,and carbides precipitate on martensite lath.The microstructure consistency provides the possibility for the induction tempering instead of lead tempering.Hardnes analysis show that the maximum surface temperature determines the hardness distribution,while the surface temperature range between 450 ℃-550 ℃,the hardness distribution is in accordance with the technological requirements;proper insulation(holding time 1-5 s)can optimize the radial hardness distribution.(5)In this paper,process parametersof 30 CrMnSi Ni2A steel thread partsinduction local tempering are: current frequency f=120KHZ,current density Js=25e6A m2?,heating time 3 s,holding time 1-5 s.