Induction crucible furnace having a refractory crucible

Abstract

The invention relates to an induction crucible furnace having a refractory crucible, a coil extending around the crucible and having a plurality of coil sections which are arranged one above the other in the coil longitudinal direction and between which an insulation is arranged, and having a plurality of magnetic return elements which are arranged on the outer wall of the coil so as to extend in the coil longitudinal direction, wherein the insulation has a plurality of bags in an elongate form which are filled with a pourable material.

Description

[0001] Induction crucible furnace with a refractory crucible

[0002] The present invention relates to a crucible induction furnace with a refractory crucible, a coil extending around the crucible with several coil sections arranged one above the other in the coil longitudinal direction.

[0003] The coil is arranged helically around the crucible. It typically forms a helix with a constant pitch, with several coil sections arranged one above the other. Insulation and spacer elements are inserted between the stacked coil sections to maintain the coil spacing.

[0004] DE 26 53 315 A1 discloses insulation and spacing bodies for axially insulating and spacing the conductors of coils, particularly for cylindrical coils for crucible induction furnaces. Accordingly, the insulation and spacing bodies have an adjustable insulation strip that only partially fills the space between the conductors to be insulated and spaced and has a curvature that can be adjusted to the conductor. The insulation strip is made of a plastic, for example, a polyester, epoxy, or silicone resin. It is also known to provide the insulation strip from glass-fiber-reinforced plastic. The insulation strip itself is formed as a single-piece or multi-piece connecting part whose components are arranged alternately.

[0005] DE 69 31 9905 T2 discloses an induction furnace with a crucible whose induction coil arrangement is surrounded by several yokes on the outside. The known induction coil arrangement is arranged in such a way that it can be removed from the furnace in its entirety. A disadvantage of the known crucible induction furnaces is that the manufacture and disassembly of spacers and distance elements between the coil sections is very complex, both during manufacture and disassembly.

[0006] The invention is based on the object of providing an induction crucible furnace in which insulation between the coil sections can be produced and renewed using simple means.

[0007] According to the invention, this object is achieved by a crucible induction furnace having the features of claim 1. The crucible induction furnace according to the invention has a refractory crucible with a coil extending helically around the crucible, which has a plurality of coil sections arranged one above the other in the coil's longitudinal direction. This means that the coil extending around the crucible sweeps an angle of more than 360°. Insulation is arranged between the coil sections arranged one above the other in the coil's longitudinal direction. The insulation serves to insulate the coil sections from one another in order to prevent short circuits. Furthermore, the crucible induction furnace has a plurality of magnetic return paths extending along the outer wall of the coil in the coil's longitudinal direction. According to the invention, the insulation comprises a plurality of elongated bags filled with a pourable material.The bags are preferably designed in the form of a tube, with a longer length than a wider width. The insulation uses a bag filled with loose material. This has the advantage that when the bag is inserted between the track sections, it is soft and malleable. This allows for simple assembly and easy adaptation to the locally prevailing coil geometry. Any coil irregularities can thus be easily compensated. The insulation can also be easily disassembled by removing the bags from the space between the coil sections or by allowing the insulation to disintegrate during the pyrolysis required for coil repair.

[0008] In a preferred embodiment, a refractory mortar is used for the pourable material. This has the advantage that the insulation has sufficient fire and heat resistance for use in the crucible induction furnace. Furthermore, as a non-Newtonian fluid, the mortar has the advantage of solidifying under pressure, thus supporting the coil sections against each other, especially when they press against the insulation.

[0009] For air exchange in the crucible, two or more bags are advantageously arranged circumferentially between the coil sections. The two or more bags are spaced apart from one another, with a gap provided between each two adjacent bags. The bag is preferably made of a textile material consisting of a knitted, woven, or warp-knitted fabric. The textile material is permeable to moisture that escapes, for example, from the pourable material inside the bag during operation.

[0010] It has proven particularly useful to arrange at least some of the spaces between the coil sections in a composite. The spaces are arranged at defined intervals in the circumferential direction and across the various coil sections, thus forming a regular composite.

[0011] The invention is illustrated below using an exemplary embodiment. Fig. 1 shows a crucible induction furnace in a schematic cross-sectional view,

[0012] Fig. 2 shows a coil insulation according to the state of the art,

[0013] Fig. 3 a fully assembled coil insulation according to the invention and

[0014] Fig. 4 two coil insulations lying on a coil section.

[0015] Figure 1 is a schematic cross-sectional view of a crucible induction furnace. The crucible induction furnace has a non-metallic, ceramic or graphite-containing, refractory, hollow-cylindrical crucible 10. The crucible 10 has a hollow-cylindrical shape, with the hollow cylinder tapering conically in the base area. A melt contained in the crucible 10 can be poured through the pouring spout 12. For this purpose, the furnace can be pivoted about its pivot point 14.

[0016] A circular-cylindrical coil 16 is arranged around the crucible 10. The coil 16 itself can, for example, consist of an electrical waveguide connected to a coolant supply. Magnetic return paths 18 are provided on the outer surface of the coil sections 24 and are held by a clamping device 20. The magnetic return paths 18 extend in the longitudinal direction of the coil and conduct the alternating magnetic field generated by the coil. The coil is supplied with an alternating electrical voltage.

[0017] Figure 2 shows coil insulation 22 between coil sections 24. Coil section 24 consists of a rectangular waveguide with a coolant channel 26. Insulation 22 consists of GRP plates 28a, 28b, and 30, with a gap 32 provided between plates 28a and 28b. The gap 32 is covered by a plate 30, which in turn creates gaps above the insulator plates 28a, 28b. The layered arrangement of insulator plates 28, 30 is the prior art solution that makes it possible to reliably insulate the coil sections from one another while simultaneously enabling moisture exchange for the crucible.

[0018] Figure 3 shows the inventive solution, in which a bag 34 is placed between the coil sections. The bag 34 is spaced apart from a second bag 36, creating a gap 38 between the bags 34 and 36. As can be seen from the cross-section 37 of the bag, it has a flattened, compressed shape that protrudes slightly from the coil sections at the sides.

[0019] Figure 4 shows two bags 40 that lie along the circumference of a coil section 24 and form a gap 32 between them. The bags 40 are tubular and, in the uninstalled state, have a substantially circular cross-section that can be flattened between two coil sections (not shown in Figure 4).

[0020] The tubular bags 40 can be produced by closing a tube at one end and filling it with a loose material. A refractory mortar, such as that used in furnace construction, can be used for the loose material. Such a refractory mortar preferably contains predominantly silicon dioxide (SiO2). Aluminum oxide (Al2O3) can also be added to the mortar. The mortar is generally not set here, i.e., is added to the tube in loose form, for example by extrusion. The tube is then closed at its open end and can then be installed in this way. Natural materials such as jute or hemp can be used as the material for the tube. However, it is also possible to use tubes made of a plastic textile.In a preferred embodiment, the tubular sheaths have a length of 25 to 55 cm and a diameter of a few centimeters.

Claims

Claims:

1. Induction crucible furnace with a refractory crucible (10), a coil (16) extending around the crucible (10) with several coil sections (24) arranged one above the other in the longitudinal direction of the coil, between which an insulation (22) is arranged, and with a plurality of magnetic return points (18) which are arranged on the outer wall of the coil extending in the longitudinal direction of the coil, characterized in that the insulation (22) has a plurality of bags (34) filled with a pourable material in an elongated shape.

2. Induction crucible furnace according to claim 1, characterized in that at least one bag (34) is designed in the form of a tube, the longitudinal extent of which is greater than the transverse extent.

3. Induction crucible furnace according to claim 1 or 2, characterized in that the bag (34) consists of a textile material which is permeable to moisture from the pourable material.

4. Induction crucible furnace according to one of claims 1 to 3, characterized in that the pourable material comprises a refractory mortar.

5. Induction crucible furnace according to one of claims 1 to 4, characterized in that two or more bags (34) are arranged circumferentially between the coil sections (24).

6. Induction crucible furnace according to claim 5, characterized in that the bags (34) are arranged spaced apart from each other in the circumferential direction and a space is provided between two adjacent bags (34). Induction crucible furnace according to claim 6, characterized in that at least a part of the spaces between the coil sections (24) are arranged in a composite, wherein the spaces are arranged at defined intervals in the circumferential direction and across the various coil sections (24).

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