Numerical Simulation Of Continuous Moving Induction Hardening With The Dual-loop Coil

Surface hardening is one of the important ways of heat treatment for automobile die,which can effectively improve the surface hardness and wear resistance of the die,and its quality will directly affect the service life of the die.Induction hardening has the advantages of high heating efficiency,small deformation and good surface finish,which is expected to replace the traditional flame hardening and become the most common way of surface heat treatment for automobile die.The coil shape selected for induction hardening is crucial to the efficiency of heating.In order to realize the mechanized operation of induction hardening for automobile die,firstly,the advantages and disadvantages of the inductor used in current induction hardening are compared and analyzed,and a dual-loop coil used for induction heating with high heating efficiency and high flexibility is designed and produced.Secondly,the relationship between thermophysical parameters and temperature of GGG70L mold material was obtained,and the material model was established.Based on the theory of electromagnetic field and temperature field,the induction heating model of the dual-loop coil continuously moving on the surface of the die was established by using finite element software.The temperature distribution of the shaping surface and cutting edge of die during the induction heating with a dual-loop coil was studied.Finally,based on the induction heating model,the influence of different process parameters on the heating effect of double loop route was investigated,and the original process parameters were improved according to the technical requirements of die surface hardening.The results show that the induction heating area of the dual-loop coil is mainly concentrated under the coil with an ellipse shape,and the maximum temperature will lag behind the coverage area of coil,but the hysteresis phenomenon is not obvious.In 2 seconds,the maximum temperature of the workpiece surface can reach the maximum value,and then the maximum temperature fluctuates in a small range and keeps a relatively stable state.When the shaping surface of the die is quenched with the dual-loop coil,the temperature distribution in the heating area is uniform.The heat in the skin depth mainly comes from joule heat generated by the induction eddy current,and its temperature rise curve shows a double-peak curve with preheating,while the heat outside the skin depth mainly comes from heat conduction in the high temperature region,and its temperature rise curve shows a singlepeak curve.When the cutting edge of the die is quenched,its temperature rise curve shows a single-peak curve.The sharp angle effect results in more dense eddies at the edge,and the uniformity of temperature distribution in the heating area decreases.When the shaping surface and the cutting edge of the die are quenched by dual-loop coil,their surface hardness can meet the quenching specification.