EP0771239B1 - Process for the inductive heating of a fireproof moulding and a suitable moulding therefor - Google Patents

Abstract

A refractory guide member and a method for heating the refractory guide member by use of an inductor, where at least one collateral electromagnetic field located in a region spaced apart from the inductor is generated by the inductor. The mold part is made of an electrically conductive layer with several insulating interrupting slots for the controlled deflection of eddy currents from a main field generated by the inductor into a region spaced apart from the inductor.

Description

The invention relates to an inductively heatable refractory Molding.

Such a molded part is in EP-A-0 503 237 described. This molding consists of shells, from which at least one can be heated inductively. The outer Shell has a slot. Measures for inductive Heating from outside in the longitudinal direction of the molding Areas of the inductor are not provided.

In FR-A-2 670 697 there is an inductively heatable duct with several slits in the longitudinal direction described. The inductor extends over the entire length of the duct to be heated.

In EP-A-0 593 383 there is a twin roll caster with boundary plates shown by special inductors are heated.

From US-A-5 198 017 is an inductively heatable Pourer known for a melt vessel. The pouring spout carries several longitudinal tubes.

From US-PS 3 435 992 is a pouring sleeve for the continuous pouring of liquid metal, in particular Steel, known which, before contacting the liquid metal is heated inductively. The in the U.S. Pat. No. 3,435,992 has a pouring sleeve electrically conductive insert in the one essentially non-electrically conductive refractory material molded pouring sleeve. Through an induction coil, which surrounds the pouring sleeve and essentially for this is arranged coaxially, the electrically conductive Insert, which preferably consists of a graphite part, by a current of suitable frequency in the range of 3 to 50 kHz can be heated. However, only the electrically conductive use induction energy on and heats up, the heat generated by heat conduction to the actual, from the non-electrically conductive Refractory material formed pouring sleeve is transferred.

From US-PS 4 940 870 it is known to be a partial electrically surrounded by an induction sleeve conductive material with a whole or part continuous slot to provide. Through this slit is said to largely suppress the heating of this sleeve become.

FR 2 609 914 A1 shows a pouring sleeve, the The outer part can be heated inductively. Are in the outer part several pipes forming the pouring opening are used. Here, too, is generated by the induction energy Heat through heat conduction on the actual pouring opening forming pipes.

A disadvantage of the prior art shown here is that the induction heat is not direct, but only by heat conduction on the entire refractory part is transmitted. This is especially the case Case when the molded part is not completely removed from the inductor device is enclosed, but from this more or less "protrudes". Often this is not too avoid, because of space or construction reasons none other solution is possible. In such a case it will fireproof molding heated very unevenly, which too Stress cracks, etc.

It is therefore the object of the present invention a molded part with improved inductive heatability to propose.

This object is achieved by a molded part solved according to claim 1.

The molding according to the invention is quick and uniform inductively heatable, also in the area of electromagnetic Subfields. The inductor device can thus in an uncritical and constructively favorable area of the molded part can be placed and still the complete Molding be heated evenly inductively.

In an advantageous embodiment of the invention, the molded part a ceramic immersion pouring tube for the introduction of Metal melt, in a melt sump, especially in a mold for the production of thin slabs or strips. The immersion nozzle extends into the mold and dives, if the mold after casting with molten metal is filled with its lower area in the mold powder covered metal swamp. By the possibility by means of a arranged above the mold inductor device, the dip tube also in the area surrounded by the mold, the existing ones in particular with thin slabs and immersion pipes Risk of bridging between the immersion pouring tube and the mold wall avoided. In addition, the mold powder can be melted in a targeted manner be, which means the reproducibility of this process or the quality of the product produced is improved. Likewise, the danger of Cloggings reduced.

In a further advantageous embodiment of the invention, the molded part is a ceramic feed channel for the application of molten metal on a Conveyor belt.

A molded part according to the invention, which in particular for the introduction or Giving up molten metal essentially has the following features:

The molded part consisting of an electrically conductive layer is in Longitudinal direction with a continuous, uninterrupted, electrical insulated longitudinal slot. This electrically insulating longitudinal slot is advantageously with an electrically insulating, refractory ceramic Material filled out. The interior area enclosed by the molded part, through which the molten metal is introduced or abandoned is with one of the Molten metal facing, electrically insulating, refractory ceramic Provide inner layer. The remaining areas of the molded part, which are in use either immerse in the melt sump or when giving up the Metal melt on a cooled conveyor belt with the metal melt in Contact are made with an electrically insulating, refractory ceramic Layer. For the generation of an electromagnetic secondary field a molded part according to the invention has another in an intermediate region electrically insulating longitudinal slot. This longitudinal slot connects at least two in this intermediate area almost all over Circumference of the molded part, deflecting the electromagnetic field, electrically insulating cross slots. With this arrangement, eddy currents deflected and it forms alongside an electromagnetic main field additional electromagnetic secondary field, which is a more uniform heating guaranteed of the molding.

In a further advantageous embodiment of the invention, the molded part is in Longitudinal direction divided by an electrically insulated partition. This Partition can be in the continuous, electrically insulating longitudinal slot and the electrically insulating longitudinal slot or slots in the intermediate area be anchored. This partition can also be used as a flow divider, for example be formed in a dip tube or serve the mechanical To increase the stability of the immersion nozzle or a feed channel.

In a further advantageous embodiment of the invention, the molded part is a lateral boundary plate, as one particularly for a device for continuous pouring of molten metal between casting rolls, one so-called twin-roll caster required. The use of a In this case, the molded part according to the invention permits the inductor device not having to assemble directly at the place of action and still have an early one Solidification of molten metal in the gussets towards the casting rolls avoid. Such a molded part is a geometrically open structure with in Longitudinal side boundaries.

The following features characterize such a molded part according to the invention:

The molded part consists of an electrically conductive layer or has one such on. It is on the side facing the molten metal with a provided electrically insulating layer and points in the intermediate area at least one further electrically insulating longitudinal slot, which in Distance at least two, in this intermediate area almost over the entire Width of the molded part, interrupting the electromagnetic field Cross slots connects. Such a configuration of the molded part allows Heating also in the area of the electromagnetic secondary field.

In a further embodiment of the invention, the slots in the Intermediate area intersecting longitudinal slots, creating a targeted Redirection of eddy currents into the secondary electromagnetic field or secondary electromagnetic fields is effected.

In a special embodiment of the invention, the electrically conductive materials have a specific electrical resistance <1000 ohm mm ² / m, preferably 200 ohm mm ² / m. Experiments have shown that such materials have good coupling behavior. Particularly good results have been achieved with a carbon-bound, graphite-containing aluminum oxide material. For the electrically insulating slots and the electrically insulating inner and / or outer layer, electrically non-conductive, refractory materials, such as zirconium oxide, come into consideration.

Further advantageous embodiments of the invention result from the Subclaims and the following based on the drawings explained embodiments.

Figur 1

ein feuerfestes Formteil mit rechteckigem Querschnitt einschließlich einer Induktorvorrichtung,

Figur 2

schematisch ein Tauchgießrohr, welches Metallschmelze aus einem Verteilergefäß in eine Kokille einleitet,

Figur 3

schematisch einen Zufuhrkanal, durch welchen aus einem Verteilergefäß Metallschmelze auf eine Fördervorrichtung aufgegeben wird

Figur 4

eine seitliche Begrenzungsplatte an einem Twin-roll-caster,

Figur 5

eine Ansicht X gemäß Figur 4,

Figur 6

die Abwicklung der elektrisch leitfähigen Schicht gemäß Figur 1.

The drawings show:

Figure 1

a fireproof molded part with a rectangular cross section including an inductor device,

Figure 2

schematically an immersion pouring tube which introduces molten metal from a distribution vessel into a mold,

Figure 3

schematically shows a feed channel through which molten metal is fed onto a conveyor device from a distribution vessel

Figure 4

a side boundary plate on a twin-roll caster,

Figure 5

4 shows a view X according to FIG. 4,

Figure 6

the development of the electrically conductive layer according to FIG. 1.

Figure 1 shows a molded part (1), for example a refractory ceramic Immersion pouring tube for introducing molten metal into a mold or refractory ceramic feed channel for the application of molten metal a conveyor belt. In the area (3) the molded part (1) is one Surround inductor device (2), the main electromagnetic field (A) generated. To generate an electromagnetic secondary field (B) in the Area (4 and 5) is essentially an electrically conductive layer (6) assembled molded part (1) in the longitudinal direction with a continuous, electrically isolating longitudinal slot (7) and the other Slits (10, 11) in the intermediate area (4).

The in the intermediate area (4) almost around the entire circumference of the molded part (1) running, electrically insulating transverse slots (11) are through a also electrically insulating longitudinal slot (10) connected to each other. As a result of this design of the molded part (1), the inductor device (2) generates an electromagnetic secondary field (B) in the areas (4, 5), whereby it for inductive heating of the molded part (1) also in the areas (4, 5) is coming. To avoid the undesired coupling of molten metal in this case avoid, is the molded part (1), which essentially consists of the electrical conductive layer (6), compared to that with molten metal Provide exposed surfaces with electrically insulating layers (8, 9). These electrically insulating layers also include the end faces of the Molded part (1) insofar as they can be subjected to molten metal. The electrically insulating inner layer (8) extends over all inner surfaces of the molded part (1). The electrically insulating Outer layer (9) extends at least over the surface of the schematically illustrated melt sump. The slots (7, 10, 11) are usually with an electrically insulating, ceramic material backfilled.

FIG. 2 shows a mold (1) used as a dip tube (16) shown. A distributor vessel (18) is used as a dip tube (16) formed molded part (1) metal melt introduced into a mold (12). The molded part (1) is over a schematically shown inductor device (2) heated inductively. By designing the molded part (1) according to the invention this can also be done in the bath level of the melt sump heat. Except for the smaller one caused thereby The molded part (1) is also sensitive to thermal shock when cast on Danger of bridging, as is the case especially with thin slab casting exists, through the possibility of inductive heating of the molded part (1) in Area of the bath level reduced during the pouring process.

Figure 3 shows an arrangement analogous to Figure 2, wherein the molten metal is not in a mold, but is placed on a conveyor (13). In In this case, the molded part (1) designed as a feed channel (17) does not submerge or only to a very small extent in the molten metal. Accordingly, an electrically insulating outer layer (9) can be made narrower.

FIG. 4 schematically shows a twin roll caster with a boundary plate (15) shown for lateral limitation. By means of an inductor device (2) and the insulating plate (7, 11), the limiting plate (15) also heat inductively in the lower area. With this measure it can unwanted freezing of molten metal in the gussets, which from the Casting rolls and the or the boundary plates are formed, and what to destruction of the casting rolls or poor strip quality, be avoided.

Figure 5 shows a boundary plate (15) according to the invention, which in essentially of an electrically conductive slotted layer (6) and a electrically insulating inner layer (8). The whole plate is preferably covered with an electrically insulating layer (9).

In Figure 6 is a development of the molded part shown in Figure 1 (1) reproduced. This development includes the electrically conductive layer (6) interrupted by the electrically insulating longitudinal and transverse slots (10 and 11). The inductor device (2) is used for inductive coupling in area (3) and due to the special design in the intermediate area (4) a course of the eddy currents outlined in area (5).

Claims (12)

1. Refractory, inductively heatable shaped member, which is electrically conductive or has an electrically conductive layer (6), including at least one electrically insulating longitudinal slot (7), which is acted upon in a region (3) by an electromagnetic main field (A) of an inductor (2), characterised in that in an intermediate region (4) adjoining the said region (3) in the longitudinal direction the shaped member or its electrically conductive layer (6) has electrically insulating transverse slots (11) which extend around nearly the entire periphery or over nearly the entire breadth of the shaped member (1) such that the eddy currents induced in the region (3) of the shaped member are deflected around this intermediate region (4) into a subsequent region (5) of the shaped member.
2. Shaped member as claimed in claim 1, characterised in that the shaped member (1) is a ceramic submerged pouring tube (16) for introducing molten metal into a pool of molten metal, particularly in a mould (12).
3. Shaped member as claimed in claim 1, characterised in that the shaped member (1) is a ceramic supply passage (17) for supplying molten metal onto a conveyor device (13), particularly a conveyor belt.
4. Shaped member as claimed in one of claims 1 to 3, characterised in that the shaped member (1) has an electrically conductive layer (6) with an electrically insulating longitudinal slot (7), which is continuous in the longitudinal direction, and an electrically insulating inner layer (8), which is directed towards the molten metal, that the shaped member (1) has an electrically insulating outer layer (9) on a region (5), which is also in contact externally with molten metal, so that the electrically conductive layer (6) does not come into contact with molten metal, and that in the intermediate region (4) the shaped member (1) has at least one further electrically insulating longitudinal slot (10), which connects at least two electrically insulating transverse slots (11) which extend in this intermediate region (4) nearly around the entire periphery of the shaped member (1).
5. Shaped member as claimed in claim 4, characterised in that it is divided in the longitudinal direction by an electrically insulated partition (14).
6. Shaped member as claimed in claim 1, characterised in that the shaped member (1) is a boundary plate (15) for an apparatus for continuously casting molten metal.
7. Shaped member as claimed in claim 6, characterised in that the shaped member (1) has an electrically conductive layer (6) and an electrically insulating inner layer (8) directed towards the molten metal, that in an intermediate region (4) the shaped member (1) has at least one further electrically insulating longitudinal slot (10), which connects at least two electrically insulating transverse slots (11), which extend in this intermediate region (4) nearly over the entire breadth of the shaped member (1).
8. Shaped member as claimed in one of claims 4,5 or 7, characterised in that the slots (10,11) in the intermediate regions (4) are intersecting slots.
9. Shaped member as claimed in one of claims 4,5,7 or 8, characterised in that further slots are present for deflecting the electrical eddy currents.
10. Shaped member as claimed in one of claims 4,5 or 7 to 9, characterised in that the development of the electrically conductive layer (6) constitutes a closed surface such that electrical eddy currents can develop there.
11. Shaped member as claimed in one of claims 4,5 or 7 to 10, characterised in that the electrically conductive layer (6) has a specific electrical resistance <1000 Ohm mm²/m, preferably <200 Ohm mm²/m.
12. Shaped member as claimed in one of claims 4,5 or 7 to 11, characterised in that the electrically conductive layer (6) comprises carbon-containing, refractory material, particularly carbon bonded, graphite-containing Al₃0₃ and that the electrically insulating inner and/or outer layer (8,9) comprises electrically non-conductive, refractory materials, particularly Zro₂.

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