JPH03280387A - Manufacture of induction heating coil - Google Patents

Abstract

PURPOSE:To accomplish stable operation with the continuous injection clad forming method and reduce maintenance works by wrapping a coil conductor with an electric insulative material consisting of mica tape pinched between glass cloth tapes, and thereover laying a castable refractory substance as protector. CONSTITUTION:A three-ply tape 2 is formed by pinching a mica tape 22 between glass cloth tapes 21 and wound on the periphery of a coil conductor 1, and further thereover a castable refractory substance 3 of alumina type is laid as covering to achieve an induction heating coil. Mica which ensures electric insulation at a high temp. is not flexible, and it has been difficult to wind it on a coil conductor, but this construction as mentioned imparts flexibility to enable winding spirally on a coil in tight contact therewith. Further the maintenance works can be reduced to a great extend owing to this construction in which the outermost layer is covered with a refractory substance having a low thermal conductivity as well as low coefficient of thermal expansion, equipped with excellent resistance against heat shocks, and having low reactivity with molten glass, slag, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an induction heating coil for heating a good electrical conductor such as metal.

<Prior Art> Coils of various shapes using high-purity electrical copper pipes or plates as conductive materials are used to inductively heat metals and the like. These coils range from those that are used as conductors without coating to those that are wrapped with glass tape or asbestos around the conductor and further coated with alumina paste, and have different heat resistance depending on the usage situation. A coated coil is used.

<Problems to be Solved by the Invention> The distance between the induction heating coil and the heated material is set as small as possible in order to increase heating efficiency, but as a result, deformation of the heated material during heating occurs. The material to be heated comes into contact with the heat-resistant coating of the induction heating coil and damages the heat-resistant coating,
Furthermore, conduction due to insulation degradation may occur. In addition, especially when the material to be heated is a material whose surface is coated with glass, as in the continuous injection cladding method, or when the cladding material is manufactured by injecting molten metal,
The glass coating may melt due to the heat of the heated material that has been heated to a high temperature by induction heating, and may scatter or adhere to the induction heating coil, or the molten metal may scatter or adhere to the induction heating coil, thereby reducing the heat resistance of the induction heating coil. In some cases, the protective coating deteriorates due to chemical reactions or cracks occur due to repeated heating and cooling, resulting in deterioration and peeling, and in some cases, a significant drop in insulation or complete conduction may occur.

<Means for Solving the Problems> The above problems of the conventional coils can be solved by the following means. That is, it is an induction heating coil in which an electric insulating material is wound around the outer periphery of a coil conductor, and the outer periphery is further protected with a heat insulating refractory material. In the present invention, a three-layer tape consisting of a mica tape sandwiched between two glass cloth tapes is used as the electrical insulating material, and a castable refractory is used as an insulating refractory around the outer periphery of the tape. Sometimes I do.

Function> As shown in FIGS. 1 and 2, the induction heating coil according to the present invention has three layers on the outer periphery of a coil conductor 1 with a mica tape 22 sandwiched between two glass cloth tapes 2. It has a structure in which a structural tape 2 is wound and the outer periphery is further covered with a castable refractory material 3. In order to ensure the electrical insulation properties of coil conductors, coating them with mica is often used, but when using only mica tape, it is not flexible and
When winding it around a coil conductor, the mica thin layer peels off or breaks, so it has been difficult to wind it tightly around the coil conductor. In the method of the present invention, in order to eliminate such drawbacks of mica tape, l! ! By sandwiching the tape between glass cloth tapes, visibility can be imparted, the tape can be brought into close contact with the coil conductor, and the electrical insulation effect can be enhanced. Although the glass cloth tape can be used on one side rather than on both sides, some effect can be obtained, but since the mica tape may be damaged depending on the curved surface of the coil conductor, double-sided tape is preferable. Although it is possible to cut it and adhere it to the coil conductor, it is more preferable to wind it spirally around the coil conductor in order to impart electrical insulation properties. Furthermore, in the method of the present invention, the outermost periphery of the coil conductor wrapped with a three-layer tape is coated with a castable refractory material to increase heat resistance.1 The castable material used in the present invention has a low thermal conductivity. It requires properties such as low coefficient of thermal expansion, thermal shock resistance, and low reactivity with molten glass, slag, and molten metal, and it is necessary to cover the coil with a thin wall. Good moldability is required. From this point of view, alumina-based materials are preferred as the castable material. In particular, alumina-based materials are most suitable for applications such as the continuous injection cladding method, where the heated object is at a high temperature and molten metal and molten glass are scattered or adhered.

<Examples> Examples of the present invention will be described in detail below. In this embodiment, an induction heating coil as shown in FIG. 1 was used in a continuous injection cladding method as shown in FIG. 3. In the continuous injection cladding method, a graphite-based buffer mold 33 having an inner hole coaxial with the heating mold is disposed at the bottom of a refractory heating mold 32 surrounded by a main induction heating coil 31, and a coaxial The hollow cooling molds 34 are integrally stacked to form a combination mold. A solid or hollow base material 35 to become the inner layer of the roll is vertically inserted into this combination mold. Next, a separately prepared molten metal 36 to become the outer layer of the roll is injected into the gap 37 between the base material 35 and the combination mold, and the base material 35 is intermittently lowered. Then, the molten metal 36 is sequentially cooled and solidified by the graphite-based buffer mold 33 and the hollow cooling mold 34 while being welded to the surface of the base material 35, thereby forming a build-up layer 38. In this case, the outer periphery of the base material 35 is coated with silicic acid glass powder in advance.
39, and a preheating electromagnetic induction heating coil 40 is placed above the refractory heating mold 32 so as to surround the base material 35.
is placed, preheating the in'35 with the coil 40, and melting and firing the glass powder wave M39 to clean the surface of the base material 35 and completely weld the fleshy metal to the base material 35. be.

A coil according to the present invention was used as the preheating induction heating coil 40. The inner diameter of the coil conductor was 365 am, and a three-layer tape with a width of 19 mm and a thickness of 0 and 5 sm was spirally wrapped around the outer periphery, and the outer periphery was coated with a castable material made of alumina and alumina cement mixed. 3. Also, the base material used was a steel material with a diameter of 325 mm and whose surface was coated with silicate glass powder. As a result, while conventional coils required partial or complete repair after approximately 20 uses, the coils of the present invention were able to react with molten glass, slag, and molten metal even after being used more than 350 times, causing peeling and cracks. did not occur at all.

[Effects of the invention] As described above, the induction heating coil according to the method of the present invention is very effective against reactions with molten glass, slag, and molten metal, peeling, and cracking, and is suitable for the operating conditions of the continuous injection cladding method. It has the effect of providing sufficient durability against changes in the temperature and contributing to operational stability and reduced maintenance.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a coil according to the present invention, FIG. 2 is a cross-sectional view of a three-layer tape used in the present invention, and FIG. 3 is a cross-sectional view of a main part of the induction heating coil of the present invention in use. In the diagram: 1: Coil conductor 2: Three-layer tape castable refractory 1 Glass cloth tape 2 Mica tape

Claims (1)

[Claims] 1. An induction heating coil characterized in that an electrical insulating material is wound around the outer periphery of a coil conductor, and the outer periphery is further protected with a heat insulating refractory. 2. The induction heating coil according to claim 1, wherein the electrical insulating material wound around the outer periphery of the coil conductor is a three-layered tape having a structure in which a mica tape is sandwiched between two glass cloth tapes. 3. The induction heating coil according to claim 1 or 2, wherein the heat insulating refractory that protects the outer periphery of the coil is a castable refractory.