AU724697B2

AU724697B2 - Method and apparatus for inductively heating a refractory shaped member

Info

Publication number: AU724697B2
Application number: AU60649/96A
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: 2000-09-28
Anticipated expiration: 2016-07-23
Also published as: EP0755741A1; DE19526970A1; EP0755741B1; AU6064996A; DE19526970C2; JPH09122901A; ZA966008B; DE59608239D1; ATE209075T1; KR970005459A; CN1146939A

Abstract

Inductive preheating for a tubular refractory body uses an internal inductor (4) inserted in the interior (2) of the body and removed after heating the body. The appts. for the above process is also claimed.

Description

I/UU/U11 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 a a a a.

a.* The following statement is a full description of this invention, including the best method of performing it known to us 28. JUL. 2000 9:58 WATERMARK PATENT 613 98196010 NO. 1191 P. 'o 1 Method and Apparatus for Inductively Heating a Refractory ShaDed Member Description S The invention relates to a method of inductively heating a shaped member made of refractory material (refractory shaped member) which has a tubular 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 outer wall within it may be 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.

*G

Refractory shaped discharge members, particularly immersed discharges, are commonly heated 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.

U) 0-, 28/07 '00 FRI 09:59 [TX/RX NO 5079] 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 of the type referred to above if an inner inductor is introduced into the internal space, 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 component thus occurs which is, for instance, a submerged discharge or a tube of a "Tube-in-Tube" outlet system with which the outflow of the melt is to be interruptible and/or controllable.

An 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 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 in that the inner inductor is constituted by a cooled, principally helical, induction coil.

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

28. JUL. 2000 9:5 9 WATERMARK PATENT 613 98196010 NO. 119 1 P. 6 3 The Figure 'shows a submerged discharge for a metallurgical vessel with an inserted inner inductor.

A submerged discharge (immersed pouring tube) of a shape known per se is a refractory shaped member comprising a ceramic, carbon- containling material which may be inductively coupled to an electrical alternating field resulting in heating. The submerged discharge has a tubular, cylindrical internal space The submerged discharge is provided in a region of its exterior with a metallic outer shell The metallic outer shell (3) thus shields the submerged discharge from electromagnetic fields so that the submerged discharge would not be :uniformly heatable with an external induction coil.

In the state illustrated in the Figure, an inner inductor is slid into the tubular, cylindrical internal space The inner inductor has a cooled, helical induction coil which is connected to a generator The dimensions, and particularly the length, of the induction coil are so matched to the internal space that it extends over the entire length of the internal space to the greatest extent possible.

Furthermore, its diameter is matched to the diameter of the internal space The surface of memrber defining internal space is electrically and/or thermally insulated with respect to the induction coil with a layer for instance a ceramic glaze, so that the submerged discharge does not come into contact with components conducting electric current and/or no localised overheating occurs.

In a further embodiment of the invention the ex~ternal 28/07 '00 FRI 09:59 [TX/RX NO 50791 surface of the induction coil is electrically and/or thermally insulated with respect to the surfaces of the internal space by means of a tube section (7) It is also advantageous to match the induction coil to different geometries or wall thicknesses such that there are different spacings between the induction coil and the surfaces of the regions to be heated.

Different 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 tube section should be correspondingly constructed.

a.

The tube section also serves to centre the induction coil in the internal space The tube section (7) o o is pushed in a friction-locking manner onto the induction coil so that it may be replaced, if necessary. The external diameter of the tube section is so matched to the internal diameter of the internal space that it may be easily slid with the induction coil into the internal space and may be withdrawn from the internal space The construction can, however, also **be such that the tube section is firstly to be slid into the internal space and the induction coil then slid into the tube section

•I

The tube section has a flange to limit the sliding in. It is closed at the bottom by means of a floor in the exemplary embodiment.

In order to heat the submerged discharge in its broadened top region (10) also, the induction coil is provided above the flange with an additional winding (11).

The tube section comprises a highly heat-resistant, ceramic fibre or foam material.

It is not necessary that the tube section extends over the entire length of the induction coil Two or more tube sections can also be provided distributed along the length of the induction coil The tube section or the tube sections need not be withdrawable out of the internal space It is also possible to construct the tube section or the tube sections as a lining of the internal space which is then decomposed by the melt during the first useage.

S 15 In order to prevent the submerged discharge 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. This improves the rapid and uniform heating of the submerged discharge.

If the submerged discharge is to be heated up, the inner inductor is slid with its tube section into the internal space and the generator is switched on.

The submerged discharge is thus inductively heated rapidly and uniformly substantially over its entire length. After reaching the desired temperature the inner inductor is retracted from the submerged discharge.

The latter is then preheated and ready for pouring operation. The inner inductor may be used for many heating processes on many submerged discharges. Its possibilities for use are therefore independent of the wear of the submerged discharge. The tube section (7) may be withdrawn from the induction coil when it is 28. JUL. 2000 9:59 WATERMARK PATENT 613 98196010 NO. 119 1 P. 7/ worn, and replaced by a new tube section- In the event of different internal. diameters of submerged discharges, tube sections with correspondingly different external diameters may be kept in readiness. it is thus possible S always to slide the induction coil in centred, even with different diameters of the internal space.

The terms "comprise", "comprises", "comprised" and comprising" when used in this specification -are taken to specify the presence of stated features, integers, steps or components but does not preclude, the presence or addition of one or mrore other features, integers, steps, components or groups thereof.

a a a 9 a 9 t a.

7v\AN\ 28/07 '00 FRI 09:59 [TX/RX NO 5079]

Claims

28. JUL. 2000 9:59 WATERMARK PATENT 613 98196010 NO. 1191 P. 8 7 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method of inductively heating a shaped member made of refractory material which has a tubular internal space, characterised in that an inner inductor is introduced into the internal space, that an electrically and/or thermally insulating layer is provided between the inductor and the shaped member within the internal space, that the inductor is centered in the internal space in the shaped member or that the spacing of the inductor from the surfaces of the regions to be heated of the shaped member is so adjusted that different amounts of energy may be transferred, that the shaped member is heated by means of the inner inductor and that thereafter the inner inductor is removed from the internal space. 2. A method as claimed in claim 1, characterised in that the shaped member is an immersed pouring tube made of refractory material. :i 3. An apparatus when used for carrying out the method as claimed in claim 1 or 2, characterised in that the inner inductor is constituted by a cooled, principally helical, induction coil. S 4. An apparatus as claimed in claim 3, characterised in that the dimensions of the induction coil are matched to the dimensions of the internal space in the shaped member. i An apparatus as claimed in claim 3 or 4, characterised in that for the purpose of centering the induction coil includes at least one tube section which aligns the induction coil centrally within the internal space in the shaped member, 6. An apparatus as claimed in claim 5, characterised in that the tube section or the tube sections is/are slidable onto the induction coil. 28/07 '00 FRI 09:59 [TX/RX NO 5079] 28. JUL. 2000 9:59 WATERMARK PATENT 613 98196010 NO. 1191. P. 9 8 7. An apparatus as claimed in claim 5 or 6, characterised in that the tube section or the tube sections on the induction coil is/are replaceable. 8. An apparatus as claimed in one of claims 5 to 7, characterised in that the tube section or the tube sections comprise(s) an electrically and/or thermally insulating material. 9. An apparatus as claimed in one of claims 5 to 8, characterised in that the tube section or the tube sections comprise(s) a highly heat-resistant, ceramic fibre material or ceramic foam material. An apparatus as claimed in one of claims 5 to 9, characterised in that the i: tube section or the tube sections is/are arranged in the internal space in the shaped member at least as a partial lining thereof. S: 11. An apparatus as claimed in claim 10, characterised in that the lining in the S: :internal space in the shaped member is decomposable after the heating process. 12. An apparatus as claimed in one of claims 3 to 11, characterised in that the shaped member has an external insulation, preferably of ceramic fibre material or ceramic foam material. 13. An apparatus according to claim 3 and substantially as hereinbefore described with reference to the Figure. DATED this 27h day of July 2000 DIDIER-WERKE AG WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA IAS/JPF/MEH P10987AUOO 00;. t^P"lU f) oj 28/07 '00 FRI 09:59 [TX/RX NO 5079]