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

[0002] The coil is arranged helically around the crucible. It typically forms a helix with a constant pitch, with several coil sections stacked on top of each other. Insulating and spacer elements are inserted between the stacked coil sections to maintain the correct spacing between the coils.

[0003] From DE 26 53 315 A1, insulating and spacer bodies for the axial insulation and spacing of the conductors of coils are known, in particular for cylindrical coils for induction crucible furnaces. According to this patent, the insulating and spacer bodies have an adjustable insulating strip that only partially fills the space between the conductors to be insulated and spaced and has a curvature that can be adapted to the conductor. The insulating strip is made of a plastic, for example, a polyester, epoxy, or silicone resin. It is also known to provide the insulating strip from glass fiber reinforced plastic. The insulating strip itself is formed as a single or multi-piece connecting element, the components of which are arranged alternately.

[0004] From DE 69 31 9905 T2, an induction furnace with a crucible is known, the induction coil arrangement of which is surrounded on the outside by several yokes. The known induction coil arrangement is arranged such that it can be removed from the furnace in its entirety. US 5 987 054 A discloses another prior art induction crucible furnace.

[0005] A disadvantage of the known induction crucible furnaces is that the manufacture and dismantling of spacers and distance bodies between the coil sections are very complex, both during manufacturing and dismantling.

[0006] The invention is based on the objective 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, the problem is solved by an induction crucible furnace with the features of claim 1. The induction crucible furnace according to the invention has a refractory crucible with a coil extending helically around the crucible, which has several coil sections arranged one above the other in the longitudinal direction of the coil. 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 longitudinal direction of the coil. The insulation serves to insulate the coil sections from each other in order to prevent a short circuit. Furthermore, the induction crucible furnace has a plurality of magnetic return paths extending along the outer wall of the coil in the longitudinal direction of the coil. 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 whose longitudinal extent is greater than its transverse extent. The insulation uses a bag filled with a pourable material. This has the advantage that the bag is soft and deformable when inserted between the track sections. This allows for easy assembly and adaptation to the prevailing coil geometry. Any unevenness in the coil can thus be easily compensated for. Disassembly of the insulation is also simple: the bags are removed from the space between the coil sections, or the insulation disintegrates 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 possesses sufficient fire and heat resistance for use in the induction crucible furnace. Furthermore, as a non-Newtonian fluid, the mortar has the advantage of solidifying under pressure, thus supporting the coil sections against each other, particularly when they exert pressure on the insulation.

[0009] Advantageously, for air exchange within the crucible, two or more bags are arranged circumferentially between the coil sections. The two or more bags are spaced apart from each other, with a gap between each pair of adjacent bags. Preferably, the bag material is a textile, consisting of a knitted, woven, or crocheted fabric. The textile material is permeable to moisture that escapes, for example, during operation from the loose material inside the bag.

[0010] It has proven particularly advantageous to arrange at least some of the spaces between the coil sections in a composite structure. Within this composite, the spaces are arranged circumferentially and across the various coil sections at defined intervals, thus forming a regular composite.

[0011] The invention is described below using an exemplary embodiment. The figures shown are: Fig. 1 shows an induction crucible furnace in a schematic cross-sectional view, Fig. 2 shows a coil insulation according to the prior art, Fig. 3 shows a fully assembled coil insulation according to the invention, and Fig. 4 shows two coil insulations lying on a coil section.

[0012] Figure 1 Figure 1 is a schematic cross-sectional view of an induction crucible furnace. The induction crucible 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 at the base. Molten metal contained in the crucible 10 can be poured out via the spout 12. For this purpose, the furnace can be pivoted about its pivot point 14.

[0013] 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 longitudinally along the coil and guide the alternating magnetic field generated by the coil. The coil is supplied with an alternating electrical voltage.

[0014] Figure 2Figure 1 shows coil insulation 22 between coil sections 24. Coil section 24 consists of a rectangular waveguide with a coolant channel 26. The 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 insulating plates 28a and 28b. The layered arrangement of insulating plates 28 and 30 is the prior art solution that makes it possible to reliably insulate the coil sections from each other while simultaneously allowing moisture exchange for the crucible.

[0015] Figure 3Figure 1 shows the solution according to the invention, in which a bag 34 is placed between the spool sections. The bag 34 is spaced apart from a second bag 36, so that a gap 38 is created between the bags 34 and 36. As can be seen from the cross-section 37 of the bag, it has a flattened, compressed shape, which protrudes slightly from the sides of the spool sections.

[0016] Figure 4 Figure 1 shows two bags 40 lying along the circumference of a spool section 24, forming a space 32 between them. The bags 40 are tubular and, in their uninstalled state, have a substantially circular cross-section that can be flattened between two spool sections (not shown in Figure 2). Figure 4 ).

[0017] The tubular bags 40 can be produced by sealing one end of a tube and filling it with a pourable material. A refractory mortar, such as that used in furnace construction, can be used for this pourable material. Preferably, such a refractory mortar consists predominantly of silicon dioxide (SiO₂). Aluminum oxide (Al₂O₃) can also be added to the mortar. The mortar is largely unset, i.e., it is poured into the tube in a pourable form, for example, by extrusion.

[0018] The open end of the hose is then sealed, and it can then be installed. Natural materials such as jute or hemp can be used for the hose. However, it is also possible to use hoses made of a synthetic textile. In a preferred design, the tubular sleeves are 25 to 55 cm long with a diameter of a few centimeters.

Claims

1. An induction crucible furnace having a refractory crucible (10), a coil (16) that extends around the crucible (10) and has multiple coil portions (24) which are arranged one above the other in the coil longitudinal direction and between which insulation (22) is arranged, and having a plurality of magnetic yokes (18) which are arranged on the outer wall of the coil so as to extend in the coil longitudinal direction, characterized in that the insulation (22) comprises a plurality of elongate bags (34) filled with a pourable material.

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

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

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

5. The induction crucible furnace according to any one of claims 1 to 4, characterized in that two or more bags (34) are arranged between the coil portions (24) in the circumferential direction.

6. The induction crucible furnace according to claim 5, characterized in that the bags (34) are arranged so as to be spaced apart from one another in the circumferential direction and a gap is provided between two respectively adjacent bags (34).

7. The induction crucible furnace according to claim 6, characterized in that at least some of the gaps between the coil portions (24) are arranged in a grouping, wherein the gaps are arranged at defined distances in the circumferential directions and across the various coil portions (24).

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