JP2008256233A - Induction heating coil and induction melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating coil in which defects such as burnout by high heat, generation of gas discharge, pinhole and separation are hardly found, demonstrating sufficient insulating property. <P>SOLUTION: In this induction heating coil mainly composed of a hollow pipe 21 wound around a crucible, a surface of the pipe 21 is coated with an insulating material 22. The insulating material 22 is obtained by winding a fabric-like glass tape 23 onto the pipe 21, impregnating the glass tape 23 with liquid prepared by dispersing inorganic insulating impregnation material 24 such as alumina and silica, into a solvent, and drying. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an induction heating coil and an induction melting furnace including the induction heating coil.

  Induction melting furnaces that melt metal by electromagnetic induction generally have an induction heating coil wound around a crucible into which metal is charged. A hollow copper pipe is often used as the coil, and a coolant such as cooling water is circulated inside the copper pipe. In addition, the coil is often covered with an insulating material for insulation, and silicone rubber, glass tape, organic varnish, or the like is used as the insulating material.

However, some of these insulating materials cause thermal decomposition and release gases at high temperatures. In particular, in vacuum induction melting furnaces that perform melting in a vacuum or in an inert atmosphere under reduced pressure, these insulating materials are contained in the melting atmosphere. When the gas is released, the normal atmosphere is lost, and when the pressure rises, the dissolved metal undergoes a reaction such as oxidation, causing a reduction in quality. In addition, if the gas release increases, the possibility of causing discharge increases, and further, carbonization of the organic material occurs in a high temperature environment, so that the insulating function cannot be maintained, resulting in dielectric breakdown, and safe operation cannot be performed. In view of this, an insulating material made of inorganic ceramics has been proposed, and a bare coil that does not cover the insulating material has also been proposed (see Patent Document 1, etc.).
JP-A-8-100998

  The insulating material coated on the surface of the coil was easily burned by being exposed to high heat. In addition, although the gas emission must be reduced as much as possible, the bare coil without gas emission has insufficient insulation. In addition, the ceramic insulating material has a problem that it is difficult to obtain sufficient insulating properties due to pinholes or peeling.

  Therefore, the present invention suppresses the occurrence of burnout and outgassing due to high heat, makes it difficult to cause defects such as pinholes and peeling, and exhibits sufficient insulation, and an induction coil equipped with the induction heating coil It aims to provide a melting furnace.

  The induction heating coil of the present invention is characterized in that the surface of a wound pipe is coated with an insulating material obtained by impregnating a fabric-like base material made of an inorganic insulating material with an inorganic insulating impregnating material. As the base material made of the inorganic insulating material of the present invention, a glass tape obtained by knitting glass fibers in a tape shape is preferably used. The inorganic insulating impregnated material enters the pores of the base material and is impregnated. To make such an impregnated state, the inorganic insulating impregnated material is dispersed in a solvent and liquefied. After that, when the liquid inorganic insulating impregnating material is dried, an appropriate insulating material of the present invention can be formed on the pipe surface.

  According to the induction heating coil of the present invention, the insulating material coated on the surface of the pipe is made of an inorganic material in which a base material made of an inorganic insulating material is impregnated with an inorganic insulating impregnating material. There is no risk of burning even at high heat. In addition, the insulating material of the present invention is less likely to generate pinholes due to the structure in which the base material is impregnated with an inorganic insulating impregnated material, and is difficult to peel off even when subjected to a heat cycle. Further, since the base material and the inorganic insulating impregnated material do not undergo thermal decomposition like organic substances, they do not release gas even at high temperatures. The induction heating coil of the present invention coated with such an insulating material exhibits sufficient insulation.

  Next, the induction melting furnace of the present invention is characterized in that the induction heating coil of the present invention is wound around a crucible. The induction melting furnace of the present invention is of a type in which when a current is passed through an induction heating coil, the metal charged in the crucible is melted by induction electromagnetic action, such as a high frequency induction melting furnace or a high frequency vacuum induction melting furnace in which a high frequency current is passed. including.

  The present invention includes an induction heating coil whose surface is coated with an insulating material that suppresses the occurrence of burnout and outgassing due to high heat, and does not cause defects such as pinholes and peeling, and exhibits sufficient insulation. There exists an effect that the induction melting furnace provided with the induction heating coil can be obtained.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
<1> High Frequency Induction Melting Furnace FIG. 1 shows an induction melting furnace according to an embodiment of the present invention. The melting furnace 1 includes a bottomed cylindrical crucible 10, an induction heating coil 20 arranged in a state of being wound around a body portion 10 a of the crucible 10, and a power supply 30 for supplying a current to the coil 20. It is equipped with. According to this melting furnace 1, an eddy current is generated in the metal charged in the crucible 10 by flowing a current from the power supply 30 to the coil 20, and the metal is heated and melted by Joule heat.

The type of the melting furnace 1 is not particularly limited. For example, a vacuum melting furnace that melts a metal in a vacuum atmosphere, or a metal melted in the crucible 10 is floated on an unmelted metal on the inner wall of the furnace. Examples include a cold crucible type melting furnace that does not contact. Further, the power source 30 has a low frequency, medium frequency, or high frequency format. The material of the crucible 10 differs depending on the type of the melting furnace 1, and generally a refractory material such as alumina (Al ₂ O ₃ ) or magnesia (MgO) is used. In a cold crucible melting furnace, the crucible 10 made of water-cooled copper is used. The metal charged in the crucible 10 and melted is iron, a non-ferrous metal, or an alloy thereof. The material of the crucible 10 and the current value passed through the coil 20 are appropriately selected according to the molten metal.

<2> Induction heating coil As shown in FIG. 2, the coil 20 is mainly composed of a hollow copper pipe 21 having a rectangular cross section. The pipe 21 is spirally wound around the body portion 10a of the crucible 10 a plurality of times with an appropriate space between the pipe portion 21 and the body portion 10a. When, for example, a high-frequency current is supplied to the pipe 21 from the power supply 30, the metal charged in the crucible 10 is dissolved, but cooling water is supplied to the hollow portion 21a of the pipe 21 in order to suppress overheating. The surface of the pipe 21 is covered with an insulating material 22 as shown in FIG.

This insulating material 22 is processed into a cloth shape having a thickness of about 0.1 to 1 mm by an inorganic insulating material such as silica (silicon dioxide: SiO ₂ ), alumina (Al ₂ O ₃ ), and is formed in a tape shape. A glass tape (inorganic insulating material) 23 is impregnated with an inorganic insulating impregnating material 24. The inorganic insulating impregnating material 24 is composed of alumina (Al ₂ O ₃ ), silica (SiO ₂ ), magnesia (MgO), titania (TiO ₂ ), zirconia (ZrO ₂ ), yttria (Y ₂ O ₃ ), and tria (ThO ₂ ). ), One kind of metal oxide such as calcia (CaO), or a mixture of plural kinds thereof. The inorganic insulating impregnating material 24 enters the pores between the fibers of the glass tape 23 to be impregnated, and is coated on the glass tape 23 with a thickness that covers the surface of the glass tape 23.

  In order to impregnate the glass tape 23 with the inorganic insulating impregnating material 24, the glass tape 23 is infiltrated with a liquid obtained by dispersing the granular or powdery inorganic insulating impregnating material 24 in a diluting solvent mixed with a liquid solvent. . Thereafter, by drying the liquid inorganic insulating impregnating material 24, the insulating material 22 in which the dried inorganic insulating impregnating material 24 is impregnated in the glass tape 23 can be obtained. As the liquid solvent, toluene, xylene, acetone, alcohol or the like and a binder are used.

  In order to cover the surface of the pipe 21 with the insulating material 22, first, a glass tape 23 is wound around the surface of the pipe 21 shown in FIG. 3 (a) as shown in FIG. 3 (b). As shown in FIG. 4, the glass tape 23 may be wound in a spiral shape so that there is a gap and the surface of the pipe 21 is not exposed, or may be wound in a plurality of layers. As the number of layers to be wound increases, the thickness increases and the insulation performance improves. However, the thickness is appropriately determined in consideration of cracks due to thermal expansion. Next, the liquid inorganic insulating impregnating material 24 dispersed in the diluting solvent as described above is applied and impregnated on the glass tape 23 as shown in FIG. Thereafter, the liquid inorganic insulating impregnating material 24 is dried to obtain the insulating material 22 in which the glass tape 23 is impregnated with the inorganic insulating impregnating material 24.

  In order to apply the liquid inorganic insulating impregnating material 24 to the glass tape 23, a method such as application by brush or application by spraying is employed. Further, the drying is performed by heating to about 300 ° C., so that the diluting solvent is surely volatilized in a short time, and the insulating material 22 can be made of only the glass tape 23 and the inorganic insulating impregnated material 24. As a heating method for drying, an appropriate heating means such as a heater may be used, and heating can also be performed by flowing an electric current through the pipe 21 to bring the melting furnace 1 into an operating state.

  If possible, a wet insulating material 22 is first prepared by impregnating a glass tape 23 with a liquid inorganic insulating impregnating material 24. The insulating material 22 is wound around the pipe 21, and then dried. There are also a method of covering the insulating material 22 on 21 or a method of impregnating the inorganic insulating material while winding a glass tape. However, the method in which the glass tape 23 is first wound around the pipe 21 and then impregnated with the inorganic insulating impregnating material 24 as described above is preferable from the viewpoint of easy winding of the glass tape 23 and the like.

  FIG. 5 shows another embodiment of the present invention, in which the coil 20 according to the present invention is used to directly heat the material to be heated 11 instead of the melting furnace. This is because the coil 20 directly heats the material to be heated 11 to a predetermined temperature. The object to be heated 11 is a desired metal, an alloy, or graphite. In this case, the coil is directly radiated from the material to be heated and the coil surface is exposed to a high temperature. However, the coil 20 of the present invention can be used without problems even when repeatedly receiving 1000 ° C. radiation.

  The above is the coil 20 of the present embodiment. According to this coil 20, the insulating material 22 coated on the surface of the pipe 21 is impregnated with the inorganic insulating impregnating material 24 in the glass tape 23 made of the inorganic insulating material 22. Since the insulating material 22 is made of an inorganic material, there is no possibility that the insulating material 22 will burn out even when the heat is increased. Further, the insulating material 22 has an advantage that a pinhole is hardly generated and is not easily peeled off even when subjected to a heat cycle due to the structure in which the glass tape 23 is impregnated with the inorganic insulating impregnating material 24. Further, since the glass tape 23 and the inorganic insulating impregnating material 24 do not undergo thermal decomposition like organic substances, they do not release gas even at high temperatures. And the induction heating coil of this invention coat | covered with such an insulating material 22 fully exhibits insulation.

It is side surface sectional drawing of the induction melting furnace which concerns on one Embodiment of this invention. It is sectional drawing of the pipe which comprises the induction heating coil which concerns on one Embodiment. It is sectional drawing which shows the process which coat | covers an insulating material to a pipe in order of (a)-(c). It is a side view of the pipe in the state where the glass tape is wound. It is the side view which showed the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Induction melting furnace 20 ... Induction heating coil 21 ... Pipe 22 ... Insulating material 23 ... Glass tape (base material)
24. Inorganic insulating impregnating material

Claims (4)

  An induction heating coil, wherein a surface of a wound pipe is covered with an insulating material obtained by impregnating a cloth-like base material made of an inorganic insulating material with an inorganic insulating impregnating material.   The inorganic insulating impregnating material is impregnated into the base material as a liquid dispersed in a solvent, and then the liquid inorganic insulating impregnating material is dried to be formed on the insulating material. Item 2. The induction heating coil according to Item 1.   The induction heating coil according to claim 1 or 2, wherein the substrate is a glass tape.   An induction melting furnace in which the induction heating coil according to any one of claims 1 to 3 is wound around a crucible.

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