US3183562A - Production of ingots and castings - Google Patents

Description

May 18, 1965 4 FIGJ FIG-.2

R. S. MOORE PRODUCTION OF INGOTS AND CASTINGS Filed June 27, 1962 5 Nit E meeuaa 7E0 v 60/145057 IBLE M4 TEEML 7 a X07//EEM/6' MA Il W nu T D l n15 luvemoa Rov SPE NCER MOORE by:W %,/W,%JW6 W Arrvs;

United States Patent 3,183,562 PRODUTEON 0F 1NGOT AND CASTING?) Roy Spencer Moore, Cronulla, New South Wales, {hustralia, assignor to Foseco International Limited, Necheils, Birmingham, England, a British company Fiied June 27, 1962, Ser. No. 205,800 Claims priority, application Great Britain, July 5, 1961, 24,297/ 61 9 Claims. (Cl. 221) This invention relates to the production of ingots and castings from molten metal and more particularly to the construction of a hot top for a mould for use in the production of ingots and castings.

In the production of ingots and castings from molten metal, the molten metal in the mould shrinks on cooling and it is accordingly essential, in order to avoid shrinkage cavities in the ingot or casting, to provide a head of molten metal which will feed the main body of the ingot or casting and thus compensate for such shrinkage. To achieve this result it is essential to maintain the head metal in molten condition While the main body of metal solidifies. This can be done by providing a very considerable volume of head metal but this is wasteful and it is nowadays com? mon practice to provide a sleeving round the head metal which acts as a barrier to loss of heat from the head metal. Such a barrier may consist simply of arefractory heat insulating material but for many purposes this is not enough and it is the practice to provide a sleeve of a material which includes ingredients which, at the temperature of the molten metal, react exothermically. The method, I

and materials for use in the method, is described for example in British patent specification No. 627,678.

It is also common practice to employ a sleeving which is in two layers, an inner layer (which contacts the molten metal) of exothermic material and an outer, backing,

layer of a refractory heat-insulating material. The heat output of the exothermic material is then better directed to its purpose of maintaining the head metal molten.

It is possible to pre-fabricate such sleeves but where mould heads, or removable head boxes therefor, of different sizes are to be dealt with, this involves stocking a Wide range of different sizes of such pre-fabricated sleeves. It is accordingly often of advantage to form the sleeve in situ in the head of the mould or in a head box to be fitted to the mould. However, while the exothermic material is I burnt out in use, and thus is of no further value, the refractory backing, if undamaged, can be used again. The burning of the exothermic in direct contact with the refractory backing, however, often causes damage to the backing rendering its re-use impossible or less satisfactory.

It is also to be noted that if the refractory backing is desired to be re-used it is important that the exothermic layer, after'hse, should be readily removed from it. On the other hand, it is important that the exothermic layer should be keyed in some way to the refractory backing in order that it should not be displaced by the molten metal.

It is an object of the present invention to provide means whereby these desiderata may be achieved.

According to the present invention a method of constructing a sleeve or lining to the head of a mould for use in the production of ingots or castings, or to a head box for use with such a mould comprises applying to a sleeve or lining of refractory heat-insulating material present in the head of the mould or head box a layer of corrugated paper, card, or the like combustible material, with the 3,183,562 Patented May 18, 1965 "ice corrugations facing inwards (i.e. towards the interior of the mould or head box), and applying a layer of mouldable exothermic composition to the said corrugated surface.

It is found that the corrugations assist to key the exothermic composition into position. Moreover when, as preferred, the corrugations are substantially vertical, they assist in venting, from the assembly, gases generated in the exothermic reaction and may assist in providing access of air to the assembly to facilitate the burning of the exothermic composition and thus make it possible to use a lesser amount of exothermic composition than would otherwise be necessary.

Nevertheless, during the exothermic reaction which takes place when the molten metal fires the exothermic composition the layer of corrugated paper or like material is charred and perhaps partially burnt away so that, when the metal pouring operation is completed, and the ingot or casting solidified and removed from the mould, the residue of the exothermic composition can be easily stripped from the refractory backing layer, which can then be used again.

Advantageously, the corrugated paper or the like may be stuck to the refractory lining the walls of the mould or head box by means of a silicate adhesive.

The exothermic composition may be any of those mouldable exothermic compositions known per se for the production of linings for moulds and head boxes in the production of castings and ingots. Preferably, it is an aluminothermic composition, i.e. one comprising finely divided aluminium, one or more oxidising agents therefor in a quantity stoichiometrically less than is necessary to oxidise all the aluminium present, a refractory filler and, optionally, a small proportion of a fluoride. Such com positions are normally granular or powdery in character and are rendered mouldable by the inclusion of a binder which will set the composition into a desired shape.

It is a particular feature of the present invention that there may be used a granular exothermic composition containing a binder which is convertible on heating to a set condition. A particular binder of this type which has been found very suitable is a thermo-setting phenol-formaldehyde moulding powder, which is a common article of industrial use. However, any other thermosetting resin may be similarly employed. The advantage of using an exothermic composition containing such a binder is that, after a metal casting operation is completed, and the residue of the exothermic composition is removed, leaving the backing layer of heat-insulating refractory material still present as a lining in the mould or head box, the whole assembly of mould or head box and heat-insulating material is still hot. Hence, it is possible to apply the corrugated paper or like to the lining, and then to apply an exothermic composition to the corrugated layer, whereupon the heat of the said assembly causes the applied composition to set in the shape which it has thus been given. The whole operation is thus made very much simpler and is more rapidly carried out. It may be contrasted with the common method of pre-fabricating the required shape of exothermic lining and subjecting the shape thus obtained to a separate stoving operation to harden the shape. By the specific method of this invention just described no separate stoving operation is necessary and the residual heat of the mould is utilised. Of course, when starting a series of operations with a cold mould or head box, it is necessary to apply heat to set the first used layer of exothermic composition.

A suitable exothermic composition may contain, for example, in parts by weight:

Percent Aluminum (powder, turnings, or other finely divided form) 16-50. Oxidising agents (nitrates, chlorates, iron oxide, manganese dioxide) 5-15. Fluoride 0-15.- Binder (e.g. thermo-setting phenolformaldehyde resin), 2-6. Refractory filler (e.g. grog, chamotte, sand or the like) Remainder The actual shaping of the layer of exothermic material is conveniently effected by locating a core in the head box or mould and ramming the exothermic composition between this core and the corrugated layer. To assist in removal of the core without damage to the shaped lining of exothermic material, one or more thin metal sheets may be provided between the core and the exothermic composition. The core can then be removed without difficulty and the thin metal sheet or sheets peeled away from the layer of exothermic composition to which they remain lightly adherent.

Specific embodiments of the invention are illustrated in the accompanying drawings, in which:

FIG. 1 is a sectional side elevation of a head box for (but removed from) an ingot mould.

FIG. 2 is a sectional side elevation showing the top portion of a common billet mould.

Referring to FIG. 1, a head box 3 as used in connection with the casting of steel ingots, when removed from the ingot mould after use, is very hot. When the assembly has cooled to a suitable temperature, for instance 250 C., and after the removal of any burnt-out exothermic lining, it is placed over a sheet metal former or core 4. Hung on the four fiat sides of this core are four thin metal sheets 5. A layer of exothermic powder is poured into the cavity 6, to a suitable depth (in this case about 2") so that a complete seal against entry of molten metal will be obtained. Taking each of the four faces in turn, a suitably shaped piece of corrugated paper 7 is placed in position in contact with the refractory backing 8 and retained there temporarily by any convenient means (the paper may have been stuck to that face at an earlier stage in the process); further powder is then poured into the cavity 6, thus permanently retaining the corrugated paper in the desired position. After all four sides have been. so treated, suflicient powder to fill the cavity 6 to the required depth is added and levelled. After an appropriate waiting period, during which time the hardening action takes place, the inner former 4 may be readily removed and the four sheets 5 then each peeled away in turn. The wires 9 are, if desired, inserted while the powder is being poured,

and are therefore rigidly held in position after that powder.

4.. mould is used while still hot from a previous use. The mould 11 iscounterbored (12) to an enlarged diameter to accommodate the exothermic lining to a suitable depth. The inner surface for the lining moulding space is formed by an assembly consisting of a plug 13 (supported on rods 14) surrounded by a thin sheet metal cylinder 15 (which is merely a curved metal sheet, which need not be joined in any way). The powder is poured into the counterbore space 12. Aftera suitable hardening period, the plug 13 is removed, and the metal sheet 15 removed with a peeling action. is an important aspect of this form of the invention that a smooth, continuous and uniform contour of the casting to be made may readily be obtained, such a contour being of considerable advantage in the subsequent operations to be performed on these billets.

I claim as my invention:

1. A method for the production of lined mould heads, head boxes and the like used for casting metals which comprises applying to a lining of heat-insulatingrefractory material present therein a layer of corrugated combustible material having its corrugations facing inwards and applying a layer of mouldable exothermic composition to the said corrugated surface.

2. A method according to claim 1 wherein the corrugated combustible material is paper.

3. A method according to claim 1 wherein the corrugations of the corrugated material are disposedvertically.

4. A method according to claim 1 wherein the exothermic composition is a granular composition containing a heat-settable binding agent.

5. A method according to claim 1 wherein the exothermic composition is a granular composition containing, asbinding agent, a thermo-settable phenol-formaldehyde resin.

6. A method according toclaim 1 wherein the exethermic composition is a granular composition containing a heat-settable binding agent and is applied to the corrugated surface While the whole assembly is hot.

7. Lined moulds, head boxes and the like in which the lining comprises a layer of refractory heat-insulating material, a layer of corrugated combustible material adherent to the inner face of said refractory material, with the corrugations facing inwards, and a layer of moulded exothermic composition adherent to said corrugated surface. 8. Lined moulds, head boxes and the like according to claim 7 wherein the corrugatedmaterial is of paper.

9. Lined moulds, head boxes and the like according to claim 7 wherein the corrugations are substantially vertical.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 1/41 France. 10/53 Sweden.

MICHAEL V. BRINDISI, Primary Examiner. MARCUS U. LYONS, Examiner.

Claims (1)

1. A METHOD FOR THE PRODUCTION OF LINED MOULD HEADS, HEAD BOXES AND THE LIKE USED FOR CASTING METALS WHICH COMPRISES APPLYING TO A LINING OF HEAT-INSULATING REFRACTORY MATERIAL PRESENT THEREIN A LAYER OF CORRUGATED COMBUSTIBLE MATERIAL HAVING ITS CORRUGATIONS FACING INWARDS AND APPLYING A LAYER OF MOULDABLE EXOTHERMIC COMPOSITION TO THE SAID CORRUGATED SURFACE.

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