US3749628A

US3749628A - Hot topping an ingot mould by adhesively bonding slabs to the mould wall

Info

Publication number: US3749628A
Application number: US00069462A
Authority: US
Inventors: J Nancarrow; P Jones; P Clark
Original assignee: Foseco Trading AG
Current assignee: Foseco Trading AG
Priority date: 1969-10-16
Filing date: 1970-09-03
Publication date: 1973-07-31
Anticipated expiration: 1990-07-31
Also published as: CA932927A; FR2064370A1; SE355506B; FR2064370B1; BE757132A; DE2050996A1; ES383974A1; BR7022022D0; JPS4838058B1; NL7015235A; AT310963B; LU61880A1

Abstract

INGOT MOULD HOT TOP SLABS ARE ADHERED IN PLACE VIA A SOFT, DIFFICULTLY FLAMMABLE, DEFORMABLE LAYER BETWEEN THE SLABS AND THE MOULD WALL, WHICH ACTS TO MATCH THE CONTOURS TOGETHER AND TO TAKE UP IRREGULARITIES. THE SOFT LAYER IS ADHERED TO THE MOULD WALL VIA A LAYER OF ADHESIVE.

Description

July 31, 1973 1 NANCARROW ET AL HOT TOPPlNG AN lNGU'l MOULD BY ADHESIVELY BONDING SLABS TO THE MOULD WALL Filed Sept. 3, 1970 United States Patent Olfice 3,749,628 Patented July 31, 1973 U.S. Cl. 156-309 15 Claims ABSTRACT OF THE DISCLOSURE Ingot mould hot top slabs are adhered in place via a soft, diflicultly flammable, deformable layer between the slabs and the mould wall, which acts to match the contours together and to take up irregularities. The soft layer is adhered to the mould wall via a layer of adhesive.

This invention relates to the provision of hot topping linings in ingot moulds. For simplicity of expression the term ingot moulds is used throughout, but it IS to be understood that this term, both in the following descr1ption and in the claims, includes head boxes for such moulds, as the invention is equally applicable to the provision of hot topping linings in head boxes.

Many methods are known for fixing hot toppmg slabs or other elements in the head portion of ingot moulds. Methods involving the use of extra apparatus, e.g. clips, nails, rods, ties, are generally cumbersome and no particular such method has gained any widespread acceptance.

Various adhesive systems for attaching lining slabs to mould walls have been proposed, but none has given consistently satisfactory results, principally due to the inability of the adhesive satisfactorily to perform its function under the conditions normally experienced in steelworks practice.

The walls of ingot moulds are often uneven and contain cracks, pits, and crazing, so that when a slab of lining material, which is usually fiat compared to the ingot mould wall, is pressed against the wall, contact is only established at a few places. Thus the face of the slab bearing a layer of adhesive will only be bonded to the wall at a few points of contact. Furthermore, the surface of the walls of the ingot mould is often not coherent, but consists of loosely adherent particles of iron oxide, or refractory residues from materials used as linings of anti-piping compounds in previous ingot casting operations. Lining slabs cannot be fixed to the walls using known adhesive systems without first brushing down the walls in order to remove the residues.

In addition to this small-scale unevenness, the walls of ingot moulds are rarely flat; they usually have a camber, and the lining slab must be matched to this camber in use. Thus, a flat lining slab must be deformed to shape, and any adhesive attachment system must be able to withstand the tendency of a resilient lining slab to return to a flat configuration.

Known adhesives suffer from several disadvantages: non-refractory adhesives tend to perform their desired function inadequately when subjected to the heat experienced both before and during pouring and in quantity are liable to combustion or even explosion; refractory adhesives tend to leave an adherent residue on the ingot mould walls after the ingot has been stripped. If build-up of deleterious residue over successive operations is to be avoided the residue must be removed.

Thus the use of known adhesives has tended to create the need for more meticulous cleaning of the moulds than the application of an air blast or wire brush as is normally practised. This extra cleaning is both time consuming and inconvenient.

The invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a schematic view and showing a method of hot topping an ingot mould in accordance with the present invention utilizing strips of a soft layer and FIG. 2 is a view similar to FIG. 1, except illustrating the use of a continuous soft layer with an ingot mould having an irregular inner surface which has been exaggerated for sake of clarity.

According to a first feature of the present invention there is provided a method of hot topping an ingot mould by adhering preformed hot top lining slabs therein which comprises providing on at least one of the surfaces which are to be adhered together a soft layer of diflicultly flammable material, locating the lining slabs in the ingot mould and urging them against the wall thereof, thereby to deform the soft layer, the soft layer being adhered to the surface of the ingot mould by means of an intermediate layer of adhesive. This intermediate thin layer is not a fire risk and does act satisfactorily.

According to a particular feature of the present invention there is provided a method of hot topping an ingot mould which comprises attaching a hot top lining slab to the walls of the ingot mould via a deformable sealing material to which both the lining slab and the wall are adhered by an adhesive. This deformable sealing material constitutes, in such a case, the difficultly flammable soft layer just referred to.

This method overcomes the'disadvantages associated with known adhesive systems, and allows firm attachment of hot top lining slabs to ingot mould walls, despite the possible roughness of the walls and their camber.

It is to be observed that this effect could not be obtained by merely using a thick layer of some organic adhesive, since such a thick layer would constitute a considerable fire risk. By using a soft layer of low flammability, coated with a thin layer of adhesive, good adhesion and good mechanical matching may both be obtained at the same time.

Preferably the soft layer is located first on the hot top lining slab though it may be adhered to the wall of the mould or head box and have the slub adhered thereto afterwards. An ingot mould lined with hot top lining slabs as has been herein described is illustrated in the figures. In FIG. 1, an ingot mould 10 is lined with a hot top lining slab 12 having a primer layer 14 thereon via strips of soft layer 16 and adhesive 18. In FIG. 2, an ingot mould 20 having an irregular inner surface (exaggerated for sake of illustration) is lined with a hot top lining slab 22 via a soft layer 24 with an adhesive layer 26 interposed between the soft layer 24 and the irregular inner surface of the ingot mould 20. The soft layer preferably has a thickness which is of the order of the unevenness of the mould wall, e.g. 0.8 mm. to 1.5 mm. The soft layer may be formed in a wide variety of ways, and a wide variety of materials may be used for its construction. The material may be soft and resilient, for example polyurethane foam, unvulcanised neoprene sheet or sponge polypropylene or it may be non-resilient, for example, a pasty or putty like composition, or a mastic. In some cases, e.g. certain putties or mastics, the material of the soft layer may itself be sulficiently adhesive to hold itself on the slab prior to assembly of the slab on the wall, but in others, for example foam polyurethane, an intermediate adhesive layer may be employed. The soft layer may, in some cases, be made of material similar to that of which the hot top lining slab is made. The hot top lining slab is generally 0.5-5 cm. thick, though thinner facing slabs are also known and may also be applied by the method of the invention.

In use, the presence of the soft layer allows the unevenness in the ingot mould wall to be taken up, and also, in many cases, encapsulates particles of scale, dirt and the like and is adhered fast to the solid wall of the mould itself. The adherence between slab and mould wall is effected by pressing the slab onto the mould wall. When that pressure is released, the movement of the slab away from the wall is taken up in the soft material and the adhering surfaces are not pulled apart.

The soft layer need not extend over the whole of the surface of the slab or ingot mould wall, but may be present thereon as a number of discrete areas, e.g. in the form of strips or beads of soft layer.

In order to minimise absorption of adhesive, or the material of the soft layer itself, into the slab, it is often advantageous to prime or size the slab suitably.

A number of other considerations should be borne in mind in the selection of the material for the soft layer. Preferably, the soft layer is:

(a) capable of absorbing vibration or impact shock;

(b) readily capable of deformation when pressure is applied to the hot top lining slabs being positioned in the ingot mouldgreater contact area is achieved as the soft layer conforms to micro-irregularities and geometric unevenness of the mould wall;

(c) able to maintain its functional soft condition in extremes of humidity and temperature which may be experienced in its storage;

((1) of sufficiently high tensile and shear strength to support the weight of the hot top lining slabs at ambient and elevated temperatures;

(e) possessed of sufficiently high internal shear strength at elevated temperatures, i.e. temperatures which it will experience during the casting of steel so that the viscosity of the material does not deteriorate to a sufficient extent to weaken the bond between ingot mould and lining slab by flowing;

(f) compatible with any adhesive used to adhere it to the slab or mould wall; e.g. the material of the soft layer should not cause the adhesive to form a readily detachable skin or film or absorb adhesive or otherwise adversely affect the adhesive properties thereof;

(g) capable of being sufficiently thermally degraded to make it possible easily to remove the residue from the mould after use. However, the rate of degradation should be such that adhesion between the lining and the mould wall is not affected until a skull of solidified head metal has formed within the hot top; it should not be ignited at any stage.

Materials which have been formed especially for use as the soft layer are, for example, extruded sheets or ribbons of compositions comprising one or more powdered fillers such as powdered calcium carbonate or precipitated chalk, or talc and binders such as plasticised synthetic resins, non-drying alkyd resins, blended vegetable oils or compounded mixtures of any of these. Alternatively, the binder may be a drying vegetable oil, such as a linseed oil (e.g. stand oils, blown oils or bodied blown oils) to which an antioxidant has been added. The viscosity range of the oils used may be, for example, 40-3000 poises at 25 C. The oils may also contain other additives such as viscosity stabilisers, oxidation and polymerisation catalysts, bodying agents (e.g. bentone clays) and polyisobutylones (to increase elongation). These compositions may also contain a proportion of fibrous material such as fiberized newsprint or kraft paper, asbestos, glass wool or slag wool to improve the tensile and shear strength of the composition. Further the filler may be precoated e.g. with a resin or a stearate to prevent excess absorption of the resin binder.

Any adhesive used to secure the soft material either to the hot top lining slab or to the ingot mould wall should preferably;

(a) be a pressure-sensitive material which has a high degree of tack.

(b) remain tacky and not deteriorate under extremes of humidity and temperature.

(c) provide a flexible/ resilient film when dry.

(d) operate at temperatures between 15 and +400 C.

(e) be compatible with the material of the soft layer and with the primer or size if used.

(f) be degraded or carbonised during the casting operation so as not to leave any nndecomposed portion of the adhesive on the ingot mould wall to the possible detriment of subsequent lining or casting operations.

The primer and/or size (when used) is applied to the hot topping element slab (which may be insulating or exothermic, flexible or rigid) to prevent excessive absorption of adhesive by the hot topping composition. The primer or size should be flexible or resilient when dry, preferably non-inflammable and render the hot top lining element surface substantially non-permeable. It preferably contains a filler or pigment (such as titania, China clay, gypsum or other commonly used paint fillers) which assists in leveling the surface of the hot top lining slab so as to present a smoother surface to which is applied the adhesive and then the layer of soft material. The primer base may be, for example, an aqueous emulsion of polyvinyl acetate or of Z-ethyl hexyl acrylate. A dilute emulsion of the adhesive which will be used may be employed if desired. A suitable commercially available size is Dunlop Chemical Products Divisions Politone.

In practice, the primer and soft layers are preferably applied to the surface of the hot topping slabs which are to be stuck to the ingot mould wallthis may be in a series of strips or beads, or it may cover the whole face of the element. A particularly preferred arrangement is that of a number of spaced parallel strips each /22 wide, spaced /2-2 apart. It is very preferable to apply the soft layer along at least that edge of each slab which will be lowest in use.

In a very convenient manner of performing the invention, the soft material is employed as strips of an extruded composition having a layer of adhesive applied to both faces. The adhesive/soft material sandwich may then be protected by the application of a leaf of conventional release paper to each face. The adhesive/ soft material sandwich is applied to the primed areas of the hot topping element after removal of one of the release papers. The second release paper is removed immediately prior to fixing the slab in the ingot mould. By applying pressure to the hot top lining slab it is caused to adhere firmly to the mould wall, and the soft material is deformed to accommodate all the surface irregularities of the mould wall. The soft material may in some cases flow and tend to encapsulate any loose particles which may be adhering to the mould wall, and allow the adhesive to penetrate between the particles themselves. The technique may be employed successfully with ingot moulds at temperatures ranging from -15 to +400 C. Naturally, it is unnecessary to use release papers if the adhesive/soft material sandwich is applied directly to the hot topping slab.

Hot topping slabs of particular suitability for use in the present invention are those described and claimed in our copending US. application Ser. No. 24,021, now abandoned, assigned to a common assignee.

The following example will serve to illustrate the invention: For use as the soft materials a mastic composition was prepared from the mixture of two parts by weight of precipitated chalk and one part by weight of a nondrying alkyd resin. This composition was extruded into ribbons /2" wide and thick. Each face of the ribbon was coated with a 50% aqueous emulsion of poly 2 ethyl hexyl acrylate and allowed to dry. A suitable coating Weight is 5-50 gms. of emuision per square foot, a coating weight of -30 gms. per square foot being preferred. Each face was then protected with a strip of siliconetreated release paper. Insulating hot top slabs were then prepared to receive the adhesive sandwich by painting the rear faces (i.e. those which were to be remote from the cast metal when functioning as hot topping insulators) with a primer consisting of a partly hydrolised polyvinyl acetate emulsion containing a china clay filler. The release paper was removed from one face of a strip of the adhesive/mastic sandwich which was then applied along the bottom edge of the rear face of one of the insulating slabs. Further strips were then applied to the slab, parallel to the first strip, and spaced at /2 intervals, over the complete face of the slab. The remaining slabs were prepared for use in a similar Way. The slabs were then easily fixed in position in the head of an ingot mould by merely removing the second release paper and pressing the slabs into the appropriate position.

It will be appreciated that, although reference has been made to as many as three separate components (primer, adhesive and soft material), it may sometimes be possible to incorporate two or all of these components into one composite material. For example, it may be possible to use a soft material which is also sufiiciently adhesive to perform the function of adhering to the hot top-ping slab. It may also be possible to incorporate an impermeable layer during the manufacture of the hot topping element and thereby obviate the need for a primer application.

It is to be understood that the present invention includes not only the method set out above, but also the materials for carrying out such a method. In particular, the invention includes the strips of soft material of the type noted coated each side with a pressure-sensitive adhesive, and also includes ingot moulds or hot top slabs, sleeves or the like having such strips adhered thereto.

We claim as our invention:

1. In the method of hot topping an ingot mould having a nonuniform surface by adhering preformed hot top lining slabs to the head portion surface of the mould, the improvement which comprises providing lining slabs having a soft layer of ditficultly flammable material covering at least part of one surface of the lining slabs and adhered thereto with the other surface of the soft layer being free, providing an adhesive on at least one of the head portion and free surfaces, said difficultly flammable material being capable of being deformed to conform to the surface of the head portion, locating the lining slabs adjacent the head portion of the mould with the soft layer next to the head portion surface and urging the lining slabs against the head portion to deform the soft layer to conform to the head portion surface and adhesively bond the lining slab to the head portion surface.

2. A method according to claim 1 wherein both the hot top lining slabs and the head portion surface of the mould are adhered by an adhesive to the soft layer.

3. A method according to claim 1 wherein the thickness of the soft layer is 0.8-1.5 mm.

4. A method according to claim 1 wherein the soft layer comprises a number of discrete strips of material.

5. A method according to claim 1 wherein the face of each of the hot top lining slabs having the soft layer thereon has been primed.

6. A method according to claim 5 wherein the hot top lining slabs are treated with an emulsion of a polymeric film-forming material containing a material selected from the group consisting of pigments and fillers.

7. A method according to claim 1 wherein the adhesive is a polymer of 2 ethyl hexyl acrylate.

8. A method according to claim 1 wherein the soft layer comprises a mixture of a powdered filler and a fluid binder selected from the group consisting of plasticised synthetic resins, non-drying alkyd resins and vegetable oils.

9. A method according to claim 8 wherein the filler is a member selected from the group consisting of precipitated chalk, fibrous talc and talc.

16. A method according to claim 1 wherein the soft layer is a polyurethane foam.

11. A method according to claim 1 wherein the soft layer is an unvulcanized neoprene sheet.

12. A method according to claim 1 wherein the soft layer is a sponge polypropylene.

13. A method according to claim 1 wherein the soft layer is a putty.

14. A method according to claim 1 wherein the soft layer is a mastic.

15. In the method of hot topping an ingot mould having a nonuniform surface by adhering preformed hot top lining slabs to the head portion surface of the mould, the improvement which comprises providing a soft layer of difiicultly flammable material capable of being deformed to conform to the surface of the head portion, adhering the soft layer to the head portion, providing lining slabs, adhering one surface of the lining slabs to the soft layer, the soft layer covering at least part of the adhered surface of the lining slabs, an adhesive being provided on at least one of the heat portion and the surface of the lining slabs which is adhered to the soft layer and urging the lining slabs against the head portion to deform the soft layer to conform to the head portion surface and adhesively bond the lining slab to the head portion surface.

References Cited UNITED STATES PATENTS 1,838,658 12/1931 Chapin 106251 2,864,882 12/1958 Snell 260-33.6 AQ 3,320,108 5/1967 Lande 156-219 3,484,073 12/ 1969 Pusch 249 -201 ROBERT D. BALDWIN, Primary Examiner US. Cl. X.R.