AU725323B2

AU725323B2 - Method and apparatus for inductively heating a refractory shaped member

Info

Publication number: AU725323B2
Application number: AU60650/96A
Authority: AU
Inventors: Raimund Bruckner; Rudiger Grau; Daniel Grimm; Steve Lee
Original assignee: Didier Werke AG
Current assignee: Didier Werke AG
Priority date: 1995-07-25
Filing date: 1996-07-23
Publication date: 2000-10-12
Anticipated expiration: 2016-07-23
Also published as: ATE213678T1; DE59608780D1; DE19526967A1; EP0755740A1; EP0755740B1; ZA966009B; KR970005458A; AU6065096A; CN1146938A; JPH09122902A

Abstract

Inductive pre-heating process for a channel-like refractory body of substantially rectangular internal cross-section, uses an internal inductor (4) inserted in the interior (2) of the body and removed after heating the body. Apparatus is also claimed.

Description

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/UU/U1 285/91 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT r Application Number: Lodged: Invention Title: METHOD AND APPARATUS FOR INDUCTIVELY HEATING A REFRACTORY SHAPED MEMBER The following statement is a full description of this invention, including the best method of performing it known to us

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Method and Apparatus for Inductively Heating a Refractory Shaped Member Description The invention relates to a method of inductively heating a refractory shaped member which has a passage-shaped internal space. The invention also relates to an apparatus for carrying out the method.

Such shaped members are, in particular part of a melt discharge device or melt dispensing device of a metallurgical vessel. They are preheated in order to prevent undesired cooling down of the melt flowing through them, particularly freezing thereof.

A refractory discharge for a continuous casting installation is disclosed in DE 3842690 Al. The discharge passage is surrounded from the exterior by an induction coil with which the internal outer wall may be ••go 20 inductively heated in a controlled manner. The coil is a component of the discharge unit. This is therefore complex and expensive which is of particular significance because such refractory shaped discharge members are wear members.

Refractory shaped discharge members are commonly heated up by means of gas burners. This has the disadvantage that the carbon, which is a material component of the shaped member, can burn out. It is also unfavourable that a non-uniform temperature distribution in the shaped member can occur during the heating process. Temperature differentials of, for instance, about 400K have been observed. Furthermore, the heating process requires a considerable period of time.

It is the object of the invention to render a rapid and uniform heating of the refractory shaped member possible.

In accordance with the invention the above object is solved in a method if the type referred to above if an inner inductor is introduced into the internal space of the refractory shaped member, if the shaped member is heated by means of the inner inductor and thereafter the inner inductor is removed from the internal space.

A rapid and uniform heating of the refractory shaped member thus occurs, which is, for instance, a supply and dosing system for a Belt- or Twin- Roll- caster with .oewhich the melt discharge is to be interruptible and/or 15 controllable.

eAn increased availability of the installation is achieved by the invention because freezing problems are prevented.

The method and the apparatus are suitable not only for S 20 heating at the commencement of pouring but also for heating when pouring is interrupted in order to maintain the shaped member at a suitable temperature.

An apparatus for carrying out the method is characterised 25 in that the inner inductor is constituted by one or more S. cooled induction coils.

Advantageous embodiments of the invention will be apparent from the dependent claims and the following description of an exemplary embodiment.

The Figure shows a refractory shaped member constituting a supply passage for a Twin-Roll-Caster with an inserted inner inductor.

A supply passage of a shape known per se is a refractory shaped member comprising a ceramic, carbon-containing material which may be inductively coupled to an electrical alternating field resulting in heating. The supply passage has a passage-shaped internal space of rectangular cross-section. The supply passage is provided with a metallic outer shell in a portion of its exterior, as is frequently used when using so-called SEN changers. The metallic outer shell thus shields the supply passage from electromagnetic fields so that the supply passage would not be uniformly heatable with an external induction coil.

~In the state illustrated in the Figure, an inner inductor oo 15 is slid into the internal space of rectangular cross-section. The dimensions, and particularly the length, of the inner inductor are so matched to the internal space that it extends over the entire length of the internal space to the greatest extent 20 possible. Furthermore, its external geometry is matched to the dimensions of the internal space (2) *'*The inner inductor has a plurality of cooled induction coils which are connected to a generator 25 The internal space is electrically and/or thermally insulated with respect to the inner inductor with a layer for instance a ceramic glaze, so that the refractory shaped member does not come into contact with components conducting electric current and/or no localised overheating occurs.

In a further embodiment of the invention the outer surface of the inner inductor is electrically and/or thermally insulated from the surfaces of the internal space by means of a shaped insulation member (7) It is also advantageous to match the inner inductor (4) to different geometries or wall thicknesses such that there are different spacings between the inner inductor and the surfaces of the regions to be heated.

Differing energy densities are produced with this feature in the shaped member which improves the uniformity of the heating in the event of differing wall thicknesses.

The shaped insulation member should be correspondingly constructed.

The shaped insulation member also serves to centre the inner inductor in the internal space The shaped insulation member is pushed in a frictionlocking manner onto the induction coil so that it may be replaced, if necessary. The external geometry of the shaped insulation member is so matched to the internal space that it may be easily slid with the 20 inner inductor into the internal space and may be withdrawn from the internal space The construction can, however, also be such that the shaped insulation 0 member is firstly to be slid into the internal space and the inner inductor then slid into the shaped 25 insulation member (7) The insulating shaped member has a flange at the top to limit the sliding in. It is open at the bottom.

With other applications, e.g. with supply passages with lateral discharge openings, the insulated shaped member can be closed by means of a floor.

In order to heat the supply passage in its broadened top region also, the inner inductor is provided above the flange with an additional winding The insulated shaped member comprises a highly heatresistant, ceramic fibre material or ceramic foam material.

It is not necessary that the insulated shaped member (7) extends over the entire length of the inner inductor Two or more insulating spaced members can also be provided.

The insulating shaped member or the insulating shaped members need not be withdrawable out of the internal space It is also possible to construct the insulating shaped member or the insulating shaped members as a lining of the internal space In order to prevent the supply passage radiating, i.e. losing, heat to the exterior during the heating process, it can be provided with an external insulation preferably of ceramic fibre material or ceramic foam material. This improves the rapid and uniform heating of the supply passage.

If the supply passage is to be heated up, the inner 25 inductor is slid with the insulating shaped member into the internal space and the generator is switched on. The supply passage is thus inductively heated rapidly and uniformly substantially over its entire cross-section. After reaching the desired temperature the inner inductor is retracted from the supply passage. The latter is then preheated and ready for pouring operation. The inner inductor may be used for many heating processes on many supply passages.

Its possibilities for use are therefore independent of the wear of the supply passage. The insulating shaped member may. be withdrawn from the inner inductor when it is worn, and replaced by a new insulating shaped member. In the event of supply passages of different cross-sections, insulating shaped members with correspondingly differing dimensions may be kept in readiness. It is thus possible always to slide the inner inductor in centred, even with differing geometries of the internal space.

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Claims

1. Method of inductively heating a refractory shaped member which has a passage-shaped internal space of substantially rectangular cross-section, characterised in that an inner inductor is introduced into the internal space that the shaped member is heated by means of the inner inductor and thereafter the inner inductor is removed from the internal space (2) 15 2. Method as claimed in claim 1, characterised in that the shaped member is a refractory supply passage for molten metal, particularly steel, in or on a molten metal sump.

3. Method as claimed in claim 2, characterised in that the shaped member has an external metallic shell at least over a region. o

4. Apparatus for carrying out the method as claimed in S 25 one of claims 1 to 3, characterised in that the inner inductor is constituted by one or more cooled induction coils Apparatus as claimed in claim 4, characterised in that the dimensions of the inner inductor are matched to the dimensions of the internal space in the refractory shaped member (1)

6. Apparatus as claimed in claim 4 or 5, characterised 8 in that an electrically and/or thermally insulating layer (12) is provided between the inner inductor and the internal space (2)

7. Apparatus as claimed in one of claims 4 to 6, characterised in that the spacing of the inner conductor from the surfaces of the regions to be heated of the refractory shaped member is so adjusted that different amounts of energy may be transferred.

8. Apparatus as claimed in any one of claims 4 to 7, characterised in that the inner inductor is centred in the internal space in the shaped member (1)

9. Apparatus as claimed in one of claims 7 or 8, characterised in that the centring/spacings is/are predetermined by a shaped insulating member of an electrically and/or thermally insulating material. 20 10. Apparatus as claimed in one of claims 7 to 9, characterised in that the insulating shaped member is of highly heat-resistant, ceramic fibre material or ceramic foam material.

11. Apparatus as claimed in one of claims 8 to .,characterised in that the insulating shaped member (7) may be slid onto the inner inductor

12. Apparatus as claimed in one of claims 8 to 11, characterised in that the insulating shaped member on the inner inductor is replaceable.

13. Apparatus as claimed in one of claims 4 to 12, characterised in that the insulating shaped member (7) Ir- 9 and the refractory shaped member or the inner inductor are simply releasable from one another after the heating process.

14. Apparatus as claimed in one of Claims 8 to 12, characterised in that the insulating shaped member is arranged in the internal space in the shaped member at least as a partial lining thereof.

15. Apparatus as claimed in Claim 14, characterised in that the insulating shaped member decomposes after the heating process.

16. Apparatus as claimed in one of Claims 3 to 15 characterised in that the shaped member has an external insulation preferably of ceramic fibre o material or ceramic foam material. '0V4 DATED this 23rd day of July 1996. DIDIER-WERKE AG 0* 0 WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN. VIC. 3122.