Thermal analysis of variable cross section cylinder induction heating by half open anti-profiling coil: Simulation and experimental validation

Resistance heating for variable cross-section cylinders before quenching results in the coarsening of austenite grains in the thin-wall segment, and inevitably leads to nonhomogeneous hardness and inferior properties after quenching. In this study, a half open anti-profiling coil is designed for induction heating of the workpiece before hardening. A numerical model is established, coupling the electromagnetic-thermal field and the rotary motion of the variable cross section cylinder to investigate the system heating efficiency and heating quality. The calculated data reveal the high efficiency of induction heating system, although the heating efficiency decreases significantly as the magnetic permeability rapidly drops at high temperature periods. Additionally, the temperature distribution along the axial, circumferential, and radial directions fluctuate in different parts at the end of heating time. Narrower air gap improves the heating efficiency and axial direction heating quality, albeit at the expense of reduced radial direction heating quality. An induction heating experiment validated the simulation results with an error range of 1.61% to 7.59%. These results suggest that to improve heating quality while ensuring high heating efficiency, it is crucial to design a suitable air gap that accommodates various wall thickness segments of the workpiece. Moreover, incorporating insulation measures is essential to reduce temperature distribution difference caused by surface heat dissipation. This study presents a promising technical solution for upgrading the current heat treatment process.