JPS6112640B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating coil used in an induction heating device and an induction melting furnace. An example of this type of induction melting furnace is shown in FIG.
In Fig. 1, 1 is a yoke, 2 is a heating coil,
3 is a crucible lining made of a heat insulating material, and 4 is a molten metal such as metal. A cylindrical coil 2 is arranged concentrically around the outer periphery of the crucible lining 3.

As can be seen from FIG. 1, the heating coil 2 has the mechanical strength to withstand the thermal expansion force of the crucible lining 3 and the weight of the molten metal 4, the moisture resistance against evaporation of water contained in the lining 3, and the molten metal. Heat resistance against heat conduction from 4 is required. Furthermore, yoke 1
electrical insulation is also required.

As a method of insulating such heating coils, a conventional method has been to wrap a varnish-treated glass cloth tape around a coil conductor to form a coil, and then impregnate the coil with varnish.

Furnace coils made by this method have sufficient electrical insulation, mechanical strength, and moisture resistance, but have a problem with heat resistance. In other words, the heat resistance of varnished glass cloth tape is limited to Class F (155°C) or Class H (180°C), and if it is used above this temperature, the insulation strength and mechanical strength will decrease and it cannot be used as an insulator. It becomes useless.

Since the conductor of induction heating coils is generally water-cooled, the temperature of the insulator is approximately 120°C under normal conditions, so it is sufficient to have heat resistance of the above H and F types. If the molten metal is accumulated in the lining 3, the molten metal will penetrate into the lining 3 due to erosion or cracks in the lining
In some cases, the molten metal may leak from the lining 3, and if such a situation occurs, the molten metal will reach the coil 2. Since the molten metal is at a high temperature, when it comes into contact with the coil 2, the insulation in a coil made by the conventional method is burned, causing an interlayer short circuit, and the coil becomes unusable. If the interlayer short circuit further progresses, the coil conductor will melt due to the short circuit current, and the cooling water flowing through the cooling water passage hole inside the conductor will leak, resulting in a secondary disaster.

This invention was made in consideration of the above-mentioned problems, and its purpose is to provide a safe induction heating coil that can prevent the above-mentioned interlayer short circuit and secondary disasters even if molten metal comes into contact with it. It is.

This invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view of a portion of the coil of the present invention. A conductor 11 is provided with a water passage hole 12 for passing cooling water. The conductor 11 is covered (taped) with an insulating layer 13 made of ceramicized silicon tape. 14 is an insulating layer made of glass cloth tape, which further covers the insulating layer 13. A coil is formed using the conductor 11 covered with the insulating layers 13 and 14, and the entire coil is impregnated with varnish to form a varnish layer 15.

When ceramicized silicone tape is used as an insulator for a heating coil, the tape becomes ceramic and maintains its insulating strength and a certain degree of mechanical strength even when high-temperature molten metal comes into contact with it, so there is no possibility that the conductor will melt due to a short circuit between the layers of the coil. Accidents such as cooling water leaking can be prevented. However, the mechanical strength of the ceramicized silicone tape is weaker than that of the varnished glass tape, so the ceramicized silicone tape alone is not suitable for use as a heating coil in terms of mechanical strength. In order to eliminate this drawback, in the present invention, as shown in FIG.
An insulating layer is formed, and a coil is formed from such a conductor and impregnated with varnish. By doing this, the surface of the coil is covered with varnished glass cloth tape, which provides sufficient electrical insulation and mechanical strength, and the impregnated varnish The layer provides sufficient moisture resistance. Furthermore, as mentioned above, since there is a ceramicized silicone tape layer inside, in the unlikely event that high-temperature molten metal leaking from the lining comes into contact with the coil, the ceramicized silicone tape will not be burned out and will be ceramicized to form the coil. maintains electrical insulation and provides sufficient heat resistance.

As described above, according to the present invention, the heating coil of an induction melting furnace or the like can be provided with sufficient mechanical strength, electrical insulation, and heat resistance, and the reliability and safety of the induction melting furnace can be greatly improved. be able to.

The present invention is applicable not only to heating coils for induction melting furnaces, but also to heating coils for induction heating devices such as billet heaters.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of an induction melting furnace, and FIG. 2 is a sectional view of a portion of an embodiment of the coil of the present invention. 2... Coil, 11... Coil conductor, 13...
...Ceramic silicone tape insulation layer, 14...
Glass cloth tape insulation layer.

Claims (1)

[Claims] 1. An induction heating coil, which is made by wrapping a ceramicized silicone tape around a conductor, wrapping a glass cloth tape over it, forming a coil with the conductor, and impregnating the entire coil with varnish.