JPS5550957A - Arc heating method of steel ingot or the like - Google Patents

Abstract

PURPOSE:To put each electrode in an optimum discharge state without using any earth wire by detecting the voltage of each phase and the phase differences of voltages and currents and relatively controlling the electrode to be controlled and other electrodes by an arithmetic detecting unit at the time of arc heating of steel ingots, etc. CONSTITUTION:The discharging electrodes 4R, 4S, 4T disposed on the steel ingot 1 in a mold 3 are subjected to elevation driving controlling by an arithmetic unit 9 and control unit 12. More specifically, at the starting, e.g., the electrode 4R of R phase is first lowered to drop the voltage VR until the voltage VR becomes zero voltage E0. After a fixed time after this, the voltages of the electrodes 4S, 4T of S phase and T phase are lowered to make the voltage VS and VT to zero voltage E0. Further after a fixed time, the electrodes 4S, 4T are simultaneously boosted and the boosting is stopped at the place of the initial discharge voltage E1. After a fixed time, the electrode 4R is similarly boosted and where it becomes voltage E1, the boosting is stopped. Where all the phases have become the voltage E1, the electrodes 4 with all of the phases R, S, T are boosted and when the normal discharge voltage E2 is reached, the boosting is stopped to complete starting and make arc discharging among the electrodes 4R, 4S, 4T, thereby heating the upper part of the steel ingot 1.