Heating Characteristics of TC4 Titanium Alloy in an HTS DC Induction Heater

Titanium andits alloyscan be heated using heavy oils, gases, resistance furnaces, liquid media, and conventional alternating current (AC) induction heaters. However, the novel superconducting direct current (DC) induction heater has several advantages over its AC counterpart in terms of heating time, efficiency, and heating quality. Therefore, it has gained remarkable success in the aluminum extrusion industry. The superconducting DC induction heaters can achieve efficiency by up to 90%, which is significantly higher than the AC induction heater (40-50%). In this study, experiments on the heating of Ti-6AL-4V (TC4) billets (Φ = 220 mm × L = 1,250 mm) using a high-temperature superconductor (HTS) induction heater were performed. A numerical 3D finite element method (FEM) model was developed to analyze the heating behavior of TC4 billets. The results from the simulation and experiments show a good agreement. Further, the radial temperature profile, heating power, and heating time were studied using the developed model. The results show that the penetration of the heating power decreases with the rotation speed. Hence a low radial temperature difference was achieved by applying an exceptionally low rotational speed on the DC induction heater, 100-500 rpm (corresponding to 1.7-8.3 Hz). We also found that heating power increased rapidly with the diameter of the TC4 billet. Therefore, the heating time could be substantially minimized by increasing the magnetic flux density and rotational speed, especially for a large billet with a diameter exceeding 300 mm. The results obtained in this study will be useful for industrial applications of Ti alloy pre-heating.