CA1075428A - Tundishes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Forming of skull in a tundish with an expendable inner lining of a set of slabs can be minimised or pre-vented by papering over the joints between the slabs before the tundish is filled.

Description

:1075~28 This invention relates to tundishes.
In the continuous casting o~ molten metal to form a continuously cast strand, it is necessary to interpose between the castlng ladle and the casting moulcl, an Intermediate vessel In order to maintain the head oE molten metal aboYe the casting monld substantially constant. Such an intermediate vessel is called a tundish and generally is provided with one inlet area from which it is replenished by a ladle and one or more outlet nozzles set in its base which feed one or more continuous casting moulds respectively.
On the termination of casting, the molten metal is allowed to run out of the tundish completely, whereafter the tundish needs to be cleaned of slag and solidified metal, together known as 'skull', before it can be reused for the next casting cycle.
The removal of skull from tundishes can generally only be accomplished with damage to the lining of the tundish~
- Refractory brick linings are expensive to install and maintain and accordingly, in recent years, the technique has been introduced of lining the tundish both with a permanent -refractory lining, usually made of refractory bricks, and with an inner expendable lining which is stripped out from the tundish together with the skull at the end of each casting cycle. Such an inner lining may be made of a plurality of highly thermally insulating boards fitted together to form an inner casing impermeable to molten metal. ~oints between ~l~7~ 2~1 adjacent boards are mortared by filling with refractory sealant, cement or the Like. Such an inner lLning aids in reducing heat loss from the tundish during casting. One particular system whLch has proved successFul is to provide, between the :inner expendable linLng made of a plurality of reeractory boards and the permanent lining a thin interlayer of loose-filled refractory material. This loose-filled refractory aida in securing clean separation of the inner expendable lining when the skull is removed.
One problem which arises with such systems is the tendency to finning of molten metal, particularly molten steel, into the joints between the refractory boards of the expendable lining, even though such joints are filled with sealant, cement or the like. Such finning not only makes the skull and expendable lining more difficult to remove at the end of a cast, but in addition the molten metal may, in some cases, penetrate to solidify adiacent the permanent refractory lining which tends to damage the latter on removal of the skull and expendable lining. Further-more, the occurrence of such finning adversely affects the thermal insulation provided by the expendable refractory lining and any intermediate loose-filling at that point.
Attempts to overcome this problem have been made by re-bating, half-lapping or otherwise changing the configuration of the jointing faces of adjacent slabs. These methods have not been wholly successful.
We have now found that the incidence of finning may be substantially reduced if, following assembly of the slabs, the joints are papered over.

~.~'7S9~
Thus, according to the present invention, there is provided a tundish for use in the continuous casting oE molten metal which tundish comprises a casing with a permanent refractory lining, an expendable inner llning made up oE a plurality of refractory lining slabs and, optionally, a loose-fill of particulate reEractory between the permanent reEractory lining and the expendable lining, and having over the joints between the slabs of the expendable lining, a paper covering.
The joints between the slabs of the expendable lining may be sealed by mortaring with a refractory cement, a sealant composition or the like, but preferably the ~ -mortar is omitted to provide dry joints.
Preferably the paper covering is in the form of a plurality of sealing strips applied over the joints. The paper is preferably held in place over the joints by ad-hering the paper over the joints using a refractory ce-ment or sealant, an organic gum or resin, an inorganic adhesive such as sodium silicate or any other e~fective adhesive system. If mortar is applied to the joints on assembly, excess mortar may be used to adhere the paper covering.
Both vertically running and horizontally running joints may be papered over in this way; generally it i5 more important to paper over the vertical joints than the horizontal.

. , .~

~s~
The paper used for the covering may be chosen from a wide variety oE commercially available materials, and may be a single layer paper of homogenous composition or a laminate. For example, the paper may be kraft paper of which one preEerred type is known commerLcally as Dry Wall Tape and consists of strips of white kraft paper having Eeathered edges perforated with 18 pinholes per inch of length. The strip is 53mm wide. The perforation and "feathering" is applied for the normal end use of the material, which is covering the joints between dry wall boards used instead of slurry plasters in the construction of houses and office blocks.
Alternative materials which may be used include adding machine paper and strips of newsprint. One or more layers of paper can be applied.
It is found that although the paper is eventually destroyed at steelmaking temperatures, its initial pre-sence as the tundish is filled serves to diminish the risk of finning greatly and so to prolong tundish life, particularly by protecting the permanent lining from damage. Additionally, the heat-insulation properties of the expendable lining and any loose refractory filling are retained with consequent desirable advantages in terms of the evenness of heat flow from the tundish.
Moreover, it has been found that by employing a -paper covering for the joints between the slabs of the .

` 30 ,. : . .

~)75i~
lining, in accordance with the invention~ the use of other joint:Lng techniques such as mortaring and/or the ~se of special configurations e.g. rebated or half-lapped joints, may be dispensed with, especially where the paper is adhered over the joints, and the paper covering can provide a barrier to limit penetra-tion at least as effective as when the joints are mor~
tared or the like.
In addition, when a jointing mortar is dispensed with, there can be no exudation of mortar at the back of the slabs adjacent the permanent lining. ~ccordingly, -the loose-fill of particulate reractory such as sand can occupy the areas which might otherwise have contained exuded mortar and can fill the space between the two linings and consolidate more effectively.
The invention includes a method Eor the continuous casting of a molten metal, especially steel, which method comprises supplying molten metal to feed a casting mould from a casting ladle via a tundish in accordance with the invention~
The following example serves to illustrate the invention:
As it would undoubtedly be advantageous to shorten the interval between installing an expendable lining . ~ .

~07~i428 and returnlng the lined tundish to service, it was decided to determine the effect of eliminating CORSEAL* or mortar from between the butting faces of boards. Accordingly a lining was assembled in which boards were tightly wedged totally dry. Predictably permanent lining deformity resulted in some larger than desirable crevices between the boards with consequent "fin" formation. After considering the problem it was decided to determine the value of applying a covering strip of paper over the joints. This was done by smearing CORSEAL* on the board faces either side of the joints and simply covering the joints with dry wall tape. This measure was found to stop the "finning". Repeated tests gave equally good results.

*Trademark. The products sold under the Trade Mark "CORSEAL" are refractory cements originally designed for sealing joints between and in foundry sand cores, and which are also used, as described in the present application, for sealing joints between tundish lining slabs. In the example described herein the product is used as an adhesive to bond the paper covering to the board faces and not as a sealant.

-6a-

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

1. A tundish for use in the continuous casting of molten metal, which tundish comprises a casing with a permanent refractory lining and an expendable inner lining made up of a plurality of refractory lining slabs, and having over the joints between the slabs of the expendable lining, a paper covering.

2. A tundish according to claim 1, wherein there is a loose-fill of particulate refractory between the permanent refractory lining and the expendable lining.

3. A tundish according to claim 1 wherein the paper covering is in the form of a plurality of sealing strips applied over the joints.

4. A tundish according to claim 1, wherein the paper covering is adhered over the joints by the use of a re-fractory cement or sealant.

5. A tundish according to claim 1 wherein the paper covering is adhered over the joints by the use of an organic gum or resin or an inorganic adhesive.

6. A tundish according to claim 1 wherein the paper covering comprises kraft paper.

7. A tundish according to claim 1 wherein the paper covering comprises adding machine paper and/or strips of newsprint.

8. A tundish according to claim 1 wherein the joints between the slabs of the expendable lining are dry joints.