| 摘要 |
PURPOSE:To reduce electric power consumption and equipment cost by heating an iron or steel material from an ordinary temp. up to a Curie point by induction heating then heating the same up to a prescribed heating temp. by direct electrical heating in succession thereby heating the same efficiently. CONSTITUTION:A steel material 1 is heated from an ordinary temp. up to a curie point in a region l1 in an induction heater 4 operated with an electric power source 5 of about 1,000-50,000Hz frequency while said material is advanced in an arrow direction in a continuous hardening device. In succession, the material is heated from the Curie point up to a specified hardening temp. by direct electroheating in a region l2 by connecting electrodes 6, 7 for power supply installed on the inlet side of the heater 4 and in a cooling tank 8 for hardening to an electric power source 9 for resistance heating. The induction heating is accomplished with high efficiency by the above-mentioned method in the low temp. region of a ferromagnetic material region of the curie point or below, whereby magnetic permeability is decreased sharply. The resistance heating is accomplished efficiently by direct conduction of electricity in the high temp. region where the intrinsic resistance value increases. |
