US3732177A - Exothermic insulating compositions comprising glass polishing residue - Google Patents

Abstract

EXOTHERMIC INSULATING COMPOUND FOR USE IN THE CASTING OF METALLS COMPRISING 50-82% FINELY DIVIDED EFACTORY MATERIAL COMPRISING AT LEAST ABOUT 10% GLASS POLISHING RESIDUE, 0 TO 72% SAND, 0 TO 20% SILICA FLOUR, AND 0 TO 20% DIATOMACEOUS EARTH, 4-12% ASBESTOS FIBER, UP TO 12% CELLULOSIC MATERIAL, UP TO 12% REACTIVE METAL, UP TO 14% METAL OXIDE, AND 3-12% BINDER RESIN.

Description

United States Patent Office 3,732,177 Patented May 8, 1973 3,732,177 EXOTHERMIC INSULATING COMPOSITIONS COM- PRISING GLASS POLISHING RESIDUE Norman F. Tisdale, Jr., Valencia, and James F. McCarthy, Mars, Pa., assignors to The Union Commerce Bank, Cleveland, Ohio No Drawing. Continuation-impart of application Ser. No. 845,046, July 25, 1969. This application Mar. 27, 1970, Ser. No. 23,509 Int. Cl. B22c 1/22; C04b 35/14; C08g 51/04, 51/18 U.S. Cl. 260-17.2 10 Claims ABSTRACT OF THE DISCLOSURE 'Exothermic insulating compound for use in the casting of metals comprising 50-82% finely divided refractory material comprising at least about 10% glass polishing residue, to 72% sand, 0 to 20% silica flour, and 0 to 20% diatomaceous earth, 412% asbestos fiber, up to 12% cellulosic material, up to 12% reactive metal, up to 14% metal oxide, and 3-12% binder resin.

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 845,046, filed July 25, 1969, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to an exotherimc insulating composition and' articles made therefrom and particularly to an insulating composition and an article for use as or in hot tops placed on the top of ingot molds dun'ng ferrous metal ingot casting operations.

In the ferrous metal industry, steels are normally melted in a refractory lined furnace and tapped into a ladle from which they are teemed into ingot molds for solidification into final ingots which are later rolled, forged or otherwise worked into a final commercial shape. During the solidification of ingots, the metal freezes in the ingot mold from the bottom upwardly and from the sidewalls toward the center leaving a generally central conical portion which hardens last or forms a pipe and into which impurities which may be present in the molten metal are concentrated by segregation or freeze separation. In order to eliminate or to reduce substantially this piping and segregation characteristic in the freezing of ingots, it is the practice to place a hot top in the form of a wall or dam around and above the opening in the top of the ingot mold to provide a reservoir for molten metal. A hot top may be prepared from metal or a refractory material or combinations of both and generally is insulated, at least in part, to cause a pool or reservoir of the molten metal to remain molten after the pouring and until a major portion of the ingot has solidified. The pool or reservoir permits molten metal to fill the forming central conical portion of the ingot to eliminate the pipe and to force segregating impurities to the hot top section of the ingot. After solidification, the portion of the ingot within the hot top many be removed readily by cropping to provide an ingot more uniform in composition and substantially void free for the performance of further work on the ingot. In this manner, many of the problems in rolling, forging and other finishing operations which are caused by non-uniform ingots are eliminated.

Many compositions have been proposed for hot tops, or for insulating at least the inner surfaces of a hot top, to overcome the characteristic difficulties of prior art materials which include too rapid heat loss, contamination of the ingot and others. Also, many of the premolded insulating materials or panels which are used for insertion as insulating surfaces inside hot tops are very fragile and are readily broken. Known premolded materials generally have little or no deformability to permit use in non-uniform hot tops and are diflicult to store and handle prior to use. Although some of these materials have met with a measure of commercial success, prior art premolded insulating inserts for hot tops have not been a complete answer to the problems.

To perform most satisfactorily, premolded insulating inserts for hot tops, or hot tops prepared at least in part from molded insulating compositions, should have good resistance tobreakage at atmospheric temperatures to permit good storage and handling; should have a measure of deformability to permit use in non-uniform applications; should have good insulating and a measure of exothermic properties to permit minimum heat loss from the reservoir of molten metal; should break down or lose structural integrity after use without contaminating the ingot to be readily removable and disposable from the ingot and hot top; and should be a low cost item to permit economy of operation. Additionally it is most desirable that the compositions process easily and rapidly into liners and panels. It is clear, therefore, that the composition and article of this invention which meet these requirements are worthwhile advance in the art.

SUMMARY OF THE INVENTION In accordance with this invention, a new and novel composition and article are disclosed which eliminate the prior art problems. The composition has excellent insulating and exothermic properties; and when molded into shapes or forms, parts are obtained which are very resistant to cracking and spalling. Insulating parts molded from the composition have considerable deformability and resilience at ordinary temperatures which provide good resistance to breakage and damage during handling and storage. The molded composition has the quality of breaking down substantially completely after use Without contamination of the poured ingot to permit easy separation and removal from an ingot and a hot top, when used. The compositions process easily and rapidly with resultant economies in time and cost. Additionally, improved insulation properties are obtained with overall reduced composition cost.

In accordance with this invention, a composition is provided having the following parts by weight:

50-82% of finely divided refractory material, 4-l2% asbestos fiber,

012% of a cellulosic material,

012% of a powdered reactive metal,

0-14% of metal oxide, and

312% of a binder resin.

refractory material comprises about 60-79% by weight of the total composition; the glass polishing residue comprises at least about 15%, and the finely-divided sand comprises 0 to 64%. The diatomaceous earth may be any of those well known in the art. It is preferred that the finely-divided refractory material have a particle size in a range below 60 mesh, preferably below 70 mesh, i.e., less than 0.25 mm.

The glass polishing residue, which results from glass polishing operations well known in the art, contributes several important advantages to the composition. It imparts equal or better insulating properties at particle sizes substantially larger, tag. 60 or 70, than the very fine particle sizes, e.g. 200 mesh, generally required to obtain optimum insulation with materials such as finelydivided sand, silica flour, and the like. As a general rule greater porosity and, therefore, better insulation is achieved with smaller particle size refractory materials. The glass polishing residue with a larger particle size range imparts as good or better insulation properties without the disadvantages of greatly reduced filtration rates normally caused by smaller particle size refractory additives. Thus processing of the exothermic insulating compositions is considerably easier, faster, and more economical. Binder requirement for a given weight percent of refractory mix is also reduced by smaller over-all surface area of the larger particle sizes with resulting economies. In addition to excellent insulation capacity, other physical properties of the finished product are superior including resistance to cracking and spalling, resilience, resistance to breakage and damage during handling and storage, and disintegration after use.

The asbestos fiber may be any of the well known asbestos fiber materials, either substantially solid or tubular, and the length of fibers used is not critical to the invention. Any of the shorter-length, more economical fibers may be used as is desired.

The cellulosic material may be at least one of any of the Well known cellulosic materials such as Wood flour, ground-wood, pulp, shredded paper and like materials and of these it is preferred that wood flour be used.

The powdered reactive metal may be at least one selected from the group consisting of reactive metals, alloys of reactive metals, and mixtures thereof. Metals and alloys in this group comprise aluminum, boron, aluminum-silicon, boron-silicon, calcium-silicon, ferro-silicon, ferro-silicon-aluminum, and of these, aluminum, aluminum-silicon and calcium-silicon are most preferred. The particle size of the powdered reactive metal is not critical: however, for good distribution within the composition of this invention it is preferred that the particle size approximate that of the finely divided refractory material.

The metal oxide of this invention may be any metal oxide is compatible with the other components of a composition, exothermically reactive with the reactive metal at the teeming temperatures, of the molten metal being cast, and substantially non-reactive at mixing, storage and handling conditions of the exothermic insulating compositions. Those metal oxides which are preferred are manganese dioxide, iron oxides and mixtures thereof.

The binder resin may be any of the well known binder materials such as the silicates, polymers such as phenol formaldehyde, urea formaldehyde, polyvinylacetate, furfuryl alcohol, combinations thereof and mixtures thereof. As is Well known, adjustment of the pH of solutions of the compositions of this invention by the use of additives may be necessary or desirable to promote or effect the cure of the binder resin to adhere the composition in a desired shape or form.

After mixing of the desired compounds in any convenient order in suitable mixing apparatus with a carrier such as water or other, if desired, the composition of this invention 'may be formed into a desired shape for a hot top, an insulating panel, other insulating article and then dried and heated, if necessary, to cure the resin binder used to adhere the mixture.

When an insulating composition is to be used as a hot top, or a part of a hot top, suitable reinforcing such as metal, fiberglass or plastic screen, cloth or fibers may be incorporated into the article as is well known in the art. Also, when metal or ceramic hot tops are used, a composition may be prepared in a paste or slurry form for coating desired areas of the hot top or ingot mold prior to the curing of the binder.

The invention may be understood best by reference to the following examples illustrating the composition as disclosed previously in various forms and embodiments. All parts are parts by weight unless other specified.

EXAMPLE I A composition made up of 65 parts of finely divided glass polishing residue from a glass polishing operation, 5 parts wood flour, 8 parts of asbestos fiber, 8 parts of powdered aluminum, 9 parts of manganese dioxide and 7 parts of phenol formaldehyde was mixed thoroughly with sufiicient water to form a slurry having 15% by weight solids. Sufficient of the mixed slurry composition was added to a mold to form a rectangular hot top 12 inches square and 10 inches high and a major portion of the water was removed from the slurry by pressure. The Wet molded composition was removed from the mold and cured at a temperature of 380 F. for 2 hours 15 minutes. The prepared hot top was used under ordinary teeming operating conditions and performed effectively both for insulation and resistance to breakage.

A portion of the prepared composition was molded also into a test panel and tested for its insulating properties. It Was found to have an insulating K value of under 1.7 at 2500 F.

EXAMPLE II A composition having the following components was prepared:

Parts Glass polishing residue 63 Wood fiour 7 Powdered Ca-Si 6 M1102 9 Asbestos fiber 8 Phenol formaldehyde 7 Suificient water to form a slurry containing 13 to 20% by weight solids was added and the mixture formed into a hot top as in Example I. The hot top performed effectively and its K value was under 1.7 at 2500 F.

EXAMPLE III A hot top was formed as in Example I from the following composition:

Parts Glass polishing residue 63 Wood flour 6 Ferro-silicon-aluminum 6 M1102 9 Asbestos fiber 9 'Phenol formaldehyde 7 Water to form a slurry containing 13 to 20% by weight solids.

The hot top performed effectively and its K value was essentially the same as Example I.

EXAMPLE IV A hot top was formed as in Example I from the following composition:

Water to form a 15 by weight solids slurry.

The resulting hot top performed effectively and had a K factor substantially identical to that of Example I.

EXAMPLE V A composition identical with Example I was prepared except that the resin binder was made up of Parts Phenol formaldehyde (powered) 4 Polyvinylacetate (powered) 3 A hot top was formed as in Example I and its K value found to be substantially identical with Example I.

EXAMPLE VI A hot top was formed as in Example I having the fo1- A lowing composition:

The mixture was added to water to form a slurry of 20% by weight solids and the pH adjusted to 5 to 5.5 with sodium bisulfate. The resulting K factor was substantially the same as that of Example I.

EXAMPLE VII A hot top of the same composition as Example I was formed substituting for phenol formaldehyde a like amount of furfuryl alcohol-urea formaldehyde resin mixture. Again, the product had a K factor substantially the same as Example I.

Although certain preferred embodiments of this invention have been illustrated and described in the foregoing description, it will be understood that this invention is not limited to the preferred embodiments and may be embodied otherwise within the scope of the following claims.

We claim:

1. A composition for insulating metal castings consisting essentially by weight of about 50-82% finely-divided refractory material comprising at least about glass polishing residue, 0 to about 72% sand, 0 to about 20% silica flour, and 0 to about 20% diatomaceous earth; about 4-12% asbestos fiber; 0 to about 12% cellulosic material; 0 to about 12% of finely-divided reactive metal; 0 to 14% of metal oxide exothermically reactive with said reactive metal at the teeming temperature of the metal casting; and about 312% of a binder resin.

2. The composition of claim 1 wherein the refractory material has a maximum particle size of about 60 mesh.

3. The composition of claim 1 wherein the refractory material is about 60-79% and comprises at least about 15% glass polishing residue, 0 to about 64% sand, 0 to about 20% silica fiour, and 0 to about 20% diatomaceous earth.

4. The composition of claim 3 wherein the refractory material has a maximum particle size of mesh.

5. The composition of claim 1 wherein the reactive metal is aluminum, aluminum-silicon, calcium-silicon, or mixtures thereof.

6. The composition of claim 4 wherein the reactive metal is aluminum, aluminum-silicon, calcium-silicon, or mixtures thereof.

7. The composition of claim 5 wherein the metal oxide is manganese dioxide, iron oxide, or mixtures thereof.

8. The composition of claim 6 wherein the metal oxide is manganese dioxide, iron oxide, or mixtures thereof.

9. The composition of claim 1 wherein the binder resin is phenol formaldehyde, urea formaldehyde, furfuryl alcohol, polyvinylacetate, furfuryl alcohol-urea formaldehyde, furfuryl alcohol-phenol formaldehyde or mixtures thereof.

10. The composition of claim 4 wherein the binder resin is phenol formaldehyde, urea formaldehyde, furfuryl alcohol, polyvinylacetate, furfuryl alcohol-urea formaldehyde, furfuryl alcohol-phenol formaldehyde or mixtures thereof.

References Cited UNITED STATES PATENTS 3,123,878 3/1964 Davidson l0638.22 3,300,322 1/1967 DeGeer 1-0638.35 2,798,818 7/1957 Pletsch et al 10638.2 3,230,056

1/1966 Arant et al 106-3822 OTHER REFERENCES E. WOODBERRY, Assistant Examiner US. Cl. X.R.