US3539413A - Method of securing heat insulating and exothermic slabs to the inner walls of an ingot mould head - Google Patents

Description

United States Patent cc 3,539,413 METHOD OF SECURING HEAT INSULATING AND EXOTHERMIC SLABS TO THE INNER WALLS OF AN INGOT MOULD HEAD Kenneth Thomas Eccleston, Nechells, England, assignor to Foseco Trading A.G., Chur, Switzerland, a Swiss company No Drawing. Filed June 12, 1967, Ser. No. 645,466 Claims priority, application Great Britain, June 24, 1966, 28,460/ 66 Int. Cl. C093 5/06 US. Cl. l56321 6 Claims ABSTRACT OF THE DISCLOSURE Slabs of heat insulating or exothermic material to be used to line the head of an ingot mould are provided, on the mould wall contacting face, with a layer which includes a heat-settable adhesive resin, The slab may be stuck easily to the ingot mould wall and difficulties of lining ingot moulds with such slabs are thus reduced.

This invention relates to a method of assembling hot tops for ingot moulds from a plurality of slabs of heatinsulating and/or exothermic compositions.

It is well known practice to provide at the head of an ingot mould a lining which will have the effect of delaying the rate of cooling of the head metal, thus ensuring a continuous feed of molten metal to the main body of the ingot to compensate for its shrinkage as it cools.

A very large number of methods of constructing such hot tops have been described. One basic method is to provide a plurality of slabs which are fitted together in some fashion against the walls of the ingot mould in order to constitute a complete lining to the head of the ingot mould, such slabs being of heat insulating material (thus providing a barrier to loss of heat from the molten metal in the head) or of exothermic material (i.e. material which fires on contact with the molten metal to generate heat) and thus either prevent flow of heat from the molten metal or to add heat to the molten metal in the head, e.g. an aluminothermie composition may be employed for this purpose. It has further been proposed to provide such slabs which have a layer of exothermic material to face the molten metal and a backing layer of a heat-insulating material.

The actual operation of assembling such slabs to constitute a complete lining is one of considerable difficulty, especially when the ingot head opening is of large dimensions and more especially when the ingot is of the wideend-down construction, when the inner Walls of the mould taper outwardly in a downward direction. It is also difficult to arrange such slabs at varying heights in the mould to obtain varied chill lengths in the cast ingot.

Thus, a plurality of slabs being employed to make up the lining, it is necessary to hold all of the slabs, except that last inserted, in some temporary position, e.g. by clamps in approximately their desired position, the last inserted slab serving to lock the assembly together and permit removal of such temporary holding devices. A commonly employed construction, for example, where the ingot head opening is rectangular in cross section is to employ slabs which have wedging side surfaces; one such slab is located on each of the four walls and the corner slabs are inserted which make wedging action with the wall slabs. It will be appreciated that in this construction the assembly acquires no coherence as a lining until the last corner slab is inserted, thus wedging the whole assembly tightly into position as a lining against the Walls of the mould.

3,539,413 Patented Nov. 10, 1970 In our British specification No. 1,018,896 there is claimed a method of assembling a lining to the head of an ingot mould from a plurality of interfitting slabs, which comprises locating the slabs successively in their desired positions and providing, in respect of all the slabs, or in respect of some or all of those located in position before the assembly is complete, an adhesive layer between the slab and the mould wall, the said adhesive being a non-refractory plastic adhesive adapted to set sufficiently to hold the slab in position but not to set so firmly as to prevent a small degree of movement of the slab relative to the mould walls without loss of adhesion of the slab to the mould wall.

Asuitable adhesive described for the foregoing purpose is a pressure sensitive adhesive based on polyisobutylene.

The foregoing method is of limited application in that the adhesive does not of itself contribute to the fixing of the slabs, but merely holds them sufficiently while they are being assembled and fixed by some other procedure, e.g. by the provision of wedging pieces. It is an object of the present invention to provide an improved solution to the problem of fixing slabs to construct a lining to the head of an ingot mould.

According to the present invention there is provided a method of securing slabs of heat-insulating and/ or exothermic material to the inner walls of the head of an ingot mould which comprises applying to at least part of the faces of the slabs which are to contact the walls a layer comprising a heat-settable adhesive resin, locating the coated slabs in the desired positions and heating them to cause the adhesive resin to melt, bond to the wall of the ingot mould and set to form a rigid bond.

The heating of the slabs may conveniently be effected by residual heat in the ingot mould itself. The invention further includes slabs of heat-insulating and/or exothermic material having on at least part of the face of the slab which is to contact the ingot mould walls a layer comprising a heat-settable adhesive resin.

In one form of the invention the heat-settable adhesive resin is in the form of fusible particles, suspended in a viscous liquid medium, and according, therefore, to a specific feature of the invention, there is provided a method of securing slabs of heat-insulating and/or exothermic material to the inner walls of the head of an ingot mould which comprises applying to the faces of the slabs which are to contact the walls a layer comprising a particulate fusible, heat-settable adhesive resin in a viscous liquid medium, locating the coated slabs in the desired positions and heating them to cause the adhesive resin to melt, bond to the wall of the ingot mould and set to form a rigid bond.

The invention further includes slabs of heat-insulating and/ or exothermic material having a coating thereon of a composition comprising a particulate fusible, heatsettable adhesive resin in a viscous liquid medium. Such slabs may differ in the nature of the viscous liquid medium according to the manner in which they are to be used. Where the slabs are intended to be applied to a cold mold it is important that the viscous liquid medium should have some adhesive properties to hold the slabs in position up to the time when the mould is heated by the pouring into it of molten metal. In this case, it is preferred that the medium should be an adhesive of the type described in British patent specification No. 1,018,896, e.g. a pressure sensitive adhesive, preferably one based on polyisobutylene. Where, however, the slabs are intended to be applied to a hot mold it is not necessary to provide such a temporary adhesive since on contact with the hot mould Wall the heat-settable particulate fusible adhesive resin will melt, bond and set rigid.

In this case the viscous liquid medium may be for example a natural gum solution, e.g. of gum arabic or gelatin.

In either event the presence of the particulate heatsettable resin tends to reduce the overall tackiness of the coating so that it is possible, within the scope of the invention, to provide slabs with coatings of so low a tackiness that it is not necessary to provide a protective layer over the coating as is necessary for the coated slabs of British patent specification No. 1,018,896 to facilitate their handling and transport.

The heat-settable resin may be of any type. Particularly good results have been obtained by the use of phenolformaldehyde resins.

The coating containing the heat-settable resin need not extend over the whole face of the slabs which is to be juxtaposed to the mould wall. It is sufiicient to provide a coating the form of strips or a grid, or isolated patches but preferably the coating is present at least near to the margin of the slab. The bond made by the resin between the slab and the mould wall should be sufficiently strong to prevent liquid metal entering between the slabs and the mould wall, i.e. suificient to prevent floating" of the slabs.

The quantity of heat-settable resin is, of course, selected having regard to its bonding properties and the weight of the slab which it is to support.

Further heat-settable resins of use in the present invention are arrested epoxy resins. Arrested epoxy resins are formed by mixing the epoxy resin and hardener together, usually with a quantity of filler, and subsequently cooling the pasty composition formed. The material subsequently forms a tacky composition which slowly turns hard and brittle. This arrested epoxy resin may be melted by heating to about 70 C. or over and when so heated thermosets.

In the present invention, the epoxy resin and hardener are preferably heated to 80-100 C. and then mixed together with a filler. The resulting pasty composition is then extruded into a cold water-bath to form ribbons of tacky material. This tacky material may be stuck directly to the appropriate face of the slab, Where it adheres and subsequently turns brittle.

If the ribbon is allowed to become brittle prior to aflixing to the slab, the ribbon may be spot-welded to the slab. The arrested epoxy resin composition preferably contains a proportion, generally up to of a fibrous material such as asbestos, glass-fibre or cotton, to minimise the risk of breaking, cracking or flaking off of the arrested epoxy resin when it turns brittle. The amount of filler used, which may be for example, silica flour, sand or fly ash is preferably up to 80% by weight of the composition.

Preferred resins are those consisting of a pre-condensate of epichlorohydrin and bisphenol A, the hardener of choice being diaminodiphenylmethane.

Since the arrested epoxy resin in its brittle state must be heated to at least about 70 C. before melting and consequent tackiness takes place, slabs having only a coating or strips of arrested epoxy thereupon are only useful in hot ingot moulds. When it is desired to use such slabs in cold moulds, a low-temperature adhesive must also be present. The preferred adhesive for this purpose is one based on polyisobutylene, as described, for example, in British Pat. No. 1,018,896.

The present invention includes the method hereinbefore set forth, coated slabs as herein described and ingot moulds having the head lined with slabs by the method herein described.

The following examples in which all parts and percentages are by weight will serve to illustrate the invention:

EXAMPLE 1 There is applied to the surface of slabs of heat-insulating material a coating of a composition comprising equal parts by weight of powdered phenol-formaldehyde heatsettable resin and liquid phenol-formaldehyde resin. The slabs are applied to the cold walls of the head of an ingot mould. On heating, the composition sets to a hard infusible solid bonding the slabs to the mould wall.

EXAMPLE 2 There is applied to the surface of slabs of heat-insulating material a coating of a composition comprising equal parts by weight of powdered phenol-formaldehyde heatsettable resin and isopropyl alcohol. The applied composition is dried down at 7080 C. This prevents the slabs from sticking together but without impairing the adhesive properties of the composition to a hot mould wall.

The coated slabs are applied with the coated sides towards the walls of the head of an ingot mould which is at a temperature of 15 0400 C. The composition rapidly hardens and sets, bonding the slabs to the mould wall.

EXAMPLE 3 Ground epoxy resin particles were dispersed in a 2% aqueous solution of gelatin and the resulting viscous liquid applied to heat insulating slabs in strips 2.5 cm. wide x 5 mm. thick. These slabs were suitable for application to moulds at temperatures from 70 to 400 C.

EXAMPLE 4 Ground epoxy resin particles were dispersed in polyisobutylene to give a composition of pasty consistency. Strips of this composition 2.5 cm. wide by 5 mm. thick adhered strongly to slabs of heat insulating material. Slabs having such strips adhering on one side were usable in moulds at any temperature from room temperature up to about 400 C.

EXAMPLE 5 A mixture was made up of:

Parts Epoxy resin (Epikote 828XAShell Chemicals Ltd.) Silica flour 285 and to this was subsequently added 27 parts of diaminodiphenylmethane (Hardener B.250BASF). The resulting paste was extruded in ribbon form through a cold water bath and subsequently cut into strips which, when tacky, were applied to the surfaces of slabs. These slabs could be used immediately on hot or cold ingot moulds or, if the resin were allowed to become brittle, only on moulds above about 70 C.

I claim as my invention:

1. In a method of securing slabs of heat-insulating and exothermic material to the inner walls of the head of an ingot mould, the steps of applying to at least part of the faces of the slabs which are to contact the walls a layer comprising a heat-settable adhesive resin, applying the coated slabs to said walls in the desired positions with the coated faces of the slabs in contact with said walls, and heating said walls to cause the adhesive resin to melt, bond to the wall of the ingot mould and set to form a rigid bond between said slabs and said walls.

2. A method according to claim 1 wherein the heating of the slabs is effected by residual heat present in the mould walls.

3. A method according to claim 1 wherein the heatsettable adhesive resin is selected from the group consisting of phenol-formaldehyde resins and epoxy resins.

4. A method according to claim 1 wherein the heatsettable resin is applied to the slab in the form of a dispersion of the resin in a pressure-sensitive adhesive.

5. A method according to claim 1 wherein the heatsettable resin is applied to the slab in the form of a dispersion of the resin in a viscous liquid medium.

6. In a method of securing slabs of heat-insulating and exothermic material to the inner Walls of the head of an ingot mould the steps of applying to the faces of the slabs which are to contact the Walls a layer comprising a particulate fusible, heat-settable adhesive resin in a viscous liquid medium, applying the coated slabs to said 5 melt, bond to the wall of the ingot mould and set to form 10 a rigid bond between said slabs and said walls.

References Cited UNITED STATES PATENTS 10/1953 Heintz 1566O 12/1965 Gaston et a1 156291 X US. Cl. X.R. 156330, 335