US3171173A - Composite slab for hot tops - Google Patents

Description

Mach 2, 1965 F. J. INGALA 3,171,173

COMPOSITE SLAB FOR HOT TOPS I Filed May 4, 1962 INVENTOR. 6194M? 4/ A1044 United States Patent 3,171,173 COMPGSITE SLABFOR HGT TOPS Frank J. Ingala, 3323 W. 64th Place, hicago, Ill. Filed May 4, I962, Ser. No. 192,464 2' Claims. (Cl. 2214'i) The present invention relates to a heat insulating me dium, particularly designed for hot top molds, and to a method of making the same.

When molten metal is poured into a mold, the first metal that freezes against the mold wall shrinks slowly and this shrinkage is immediately filled by the molten metal in contact with it. Each succeeding layer freezing parallel to the mold surfaces shrinks similarly and takes molten metal from the center. The molten pool in the center gradually sinks downward as it feeds the shrinking walls. This continues as long as the chilling effect of the mold wall is felt in the molten pool. When this effect is no'lo'nger felt, the molten metal freezes slowly throughout and shrinks downward. The net result is a casting with sound wall, and with an axial cavity or pipe, extending a considerable distance downward.

In plants making killed steel, a hot top is placed on the top of the mold to control the depth of the pipe. In small ingot practice these hot tops usually take the form of life clay shells, which are heated as much as possible before being placed on the molds. In large ingot practice hot tops may be sectional pieces of fire clay, brick, or even lined steel castings, and the preheating is not so important because of the volume of hot metal they will contain. These hot tops are smaller in section than the mold, and are shiinnied up above the mold top so that they can float on the metal in the filled mold, thus giving ample space for shrinkage to take place without binding the hot top to the top of the mold. If such binding should occur on various types of high carbon alloy, and high speed steel, ruptured ingots might result. The space thus exposed between the mold and the hot top may be sealed with wet sand to prevent leakage as the metal rises in the hot top, or leakage may be prevented by delaying the pouring for a'short time at the joint. The volume of the hot top, depending upon the type of steel, may vary from about ten' to eighte'en'percent.

While many hot top systems have been proposed in the past, they have not always proved to be satisfactory for various reasons. The provision-of a more completely satisfactory composition for this purpose is the principal object of the present invention.

A further object of the invention is to provide an economical laminated composition for hot tops.

A further object of theinvention is to provide a method for the manufacture of compositions particularly suited for use in hot top molds.

In'general, the present invention provides a heat insulatiori medium for hot top walls which includes a laminate having a base containing a mineral insulating material, a centrally disposed block secured to the base and also containing a mineral insulating material, together with layers of a combination of smolderable vegetable material, and combustible metal'particles disposed on both sides of the block, with the layers, the block, andthe base being bonded together into aself-sustaining structure. With the arrangement described, I am able to control the cooling characteristics of the ingot more carefully with the result that the outer periphery of the casting does not solidify prematurely and thereby cause excessive shrinkage of the casting resulting in excessive pipe formation. With the preferred embodiment of the present invention, I can generate high temperatures of the order of 2200 F. in selected areas of the hot top, for periods of about ninety minutes so that a substantially uniformly cooled casting results.

The mineral insulating material of which the base and the block are preferably composed contains a mineral insulating material such as asbestos, together with combustible fibers and a resinous binder. This type of composition is specifically disclosed and claimed in my copending application Serial No. 95, 483, filed Mar. 14, 1961, now abandoned. As disclosed in that application, a preferred binder has the following composition:

Table I Ingredient Particle size Percent by weight Vegetable starch (cg. potatoes 200 to-400mesh -60 or corn starch). 7 Soy bean flour 200 to 250 mesh 10-30 Wood rosin 150 to 400 mesh 15-35 Bituminous material (e.g. 150 to 400 mesh 10-20 powdered pitch).

Table II Ingredient Range Preferred,

percent Asbestos -65% by wcight 55 Combustible fibers 20-40% Granulated rosin to 240% 5 mesh, M.P. -180" 0.). a

The binder and the dry ingredients are mixed in a clay mixer until the mass assumes a homogenous consistency. The mud-like mass thus produced is then poured into a form and pressed to a self-sustaining compact; Finally, the compact is removed from the form and dried in aii oven at 200 F. for about two hours.

The'compact which results consists of the combustible fibers, suchas paper, horsehair, of the like, uniformly dispersed throughout the asbestos and the various binding agents. The compact has" an excellent heat retaining property. As the combustible fibers burn in the compact, the heat is retained in the mass. v

The smolderabl'e vegetable material which is used in the course of the present invention is preferably composed of crushed olive stones, normally measuring from about to inch in maximum dimension. Alternatively, material such as walnut shells or the like can be employed, but I have fourid that olive stones possess sub stantially better properties for this use than other types of vegetablematter.

The hot top composition also includes" particles of a combustible metal of which aluminum is the preferred example, although zinc can also be used For the purposes of this invention, it is desirable to keep" the particle size of the combustible metal in the range'from about 12" mesh to about 30 mesh. I

Together with the combustible metal, I prefer to add a diluent such as a completely oxidized material which tempers the oxidation of the metal and thereby prevents the build up of excessive and uncontrolled amounts of heat. For this purpose, I prefer to use ferric oxide having a particle size of about 300 mesh.

I11 general, the relative proportions of the ingredients will lie within the following ranges:

A further description of the present invention will be made in conjunction with the attached sheet of drawings, which illustrate the preferred embodiment thereof.

In the drawings:

FIGURE 1 is a view in elevation of the base;

FIGURE 2 is a view in elevation illustrating the manner in which the centrally disposed block is formed over the base;

FIGURE 3 is a view illustrating the manner in which the layers of vegetable material, combustible metal, and diluent are arranged about the centrally disposed block;

FIGURE 4 is a fragmentary view illustrating the manner in which the laminated structure is compressed and consolidated by heating; and

FIGURE 5 is a fragmentary view in perspective of the finished hot top mold composition.

As shown in the drawings:

In FIGURE 1, reference numeral indicates generally the base which is employed for the hot top composition. As mentioned previously, the base 10 preferably includes a mixture of asbestos fibers and the like, together with suitable binding agents and combustible fibers. The base 10 is self-sustaining by virtue of the action of the binders and the heat supplied to the composition in its formation, all of which is discussed in a preceding portion of this specification.

In [the form of the invention shown in the drawings, a centrally disposed block 11 (FIGURE 3) is provided over the base 10 by depositing a moldable mass 12 over the base and then applying pressure by means of a forming plate 13. The mass 12 is preferably of the same composition as the base 10, that is, contains a mixture of asbestos, combustible fibers, and a resinous binder which preferably includes granulated rosin, a bituminous material such as pitch and vegetable flour. After molding the mass 12 into the configuration of the block 11, a layer of olive stones 14 is disposed over the base on both sides of the centrally disposed block 11. Then, a layer of a mixture of aluminum and ferric oxide, indicated at numeral 16 is disposed over the layer of olive stones 14. The aluminum or other metal should be thoroughly mixed with the diluent in order to modify the burning properties of.the combustible metal sufficiently for the purposes of this invention. Finally, an additional insulating layer 17 composed preferably of the same material as contained in the block 11 and the base 10 is applied over the layer 16 containing the combustible metal and the diluent. After this laminated structure tis built up, a ram 18 is brought down on the surface of the mass to consolidate it further, whereupon the pressed mass is subjected to a temperature of about 400 F. in a steam oven for a period of time of about one and a half hours. Under these conditions, the binders present in the block 11 and the insulating layer 17 are softened and diffuse through the layers to form a self-sustaining structure when the heat is removed.

As illustrated in FIGURE 5, the composite hot top composition of the present invention has several areas of varying heat transfer characteristics. The central area, represented by the block 11 is essentially a heat insulator although some heat is generated therein by the combustion of the combustible fibers, when they are used in the composition of the base 10 and in the block 11. The areas on both sides of the block 11 are essentially heat generating areas by virtue of the presence of the combustible metal particles and the smolderable olive stones 14, as well as the combustible fibers which are disposed in the base and in the overlying insulating layer 17. With this combination, the areas of the ingot outwardly from the center are kept hot for substantial periods of time so that premature chilling and the resultant formationof pipe is minimized.

The following specific example points out the manner in which the improved structure of the present invention is manufactured.

In producing a block measuring 13 inches by 13 inches by 2 inches, a base measuring about /2 inch thick and composed of asbestos mixed with a resinous binder is employed. The block 11 is then molded to provide a final thickness of about 2 inches. For this type of structure, about four pounds of crushed olive stones, 1 and /2 pounds of aluminum pigment powder, and /2 pound of ferric oxide are employed. The aluminum particles and the ferric oxide are premixed before application over the layer of olive stones. After pressing and heating, as above described, it is advisable to dust some Portland cement over the top of the laminated structure and wet trowel over the surface to serve as an additional heat retainer.

It should be evident that various modifications can be made of the described embodiment without departing from the scope of the present invention.

1 claim as my invention:

1. A heat insulating medium for hot top molds consisting of a laminate including a base and a centrally disposed block of lesser width secured to said base, both said base and said block consisting essentially of a binder containing from 30 to 60% by weight vegetable starch, 10 to 30% by weight soy bean flour, 15 to 35% wood rosin, and 10 to 20% powdered bituminous material, in combination with a mixture of 35 to 65% by weight asbestos, 20 to 40% by weight of combustible fibers and 2 to 10% by weight rosin, and alternating layers consisting essentially of crushed olive stones and aluminum particles disposed on both sides of said block, said base, said block, and said layers being bonded together into a selfsustaining structure, said olive stones constituting from 10 to 40% by weight of the final product and said aluminum particles constituting from 5 to 25% by weight of the final product.

2. The heat insulating medium of claim 1 which also includes a ferric oxide diluent in admixture with said aluminum particles in an amount of from 3 to 18% by weight of the final product.

References Cited by the Examiner UNITED STATES PATENTS 1,819,364 8/31 Firth 22147 2,462,256 2/49 Charman et al 22--147 2,791,816 5/57 Pletsch et a1. 22147 2,925,637 2/60 Edmonds et a1 22-147 FOREIGN PATENTS 828,190 2/ 60 Great Britain. 868,599 5/61 Great Britain.

MICHAEL V. BRINDISI, Primary Examiner.

MARCUS U. LYONS, Examiner,

Claims (1)

1. A HEAT INSULATING MEDIUM FOR HOT TOP MOLDS CONSISTING OF A LAMINATE INCLUDING A BASE AND A CENTRALLY DISPOSED BLOCK OF LESSER WIDTH SECURED TO SAID BASE, BOTH SAID BASE AND SAID BLOCK CONSISTING ESSENTIALLY OF A BINDER CONTAINING FROM 30 TO 60% BY WEIGHT VEGETABLE STARCH, 10 TO 30% BY WEIGHT SOY BEAN FLOUR, 15 TO 35% WOOD ROSIN, AND 10 TO 20% POWDERED BITUMINOUS MATERIAL, IN COMBINATION WITH A MIXTURE OF 35 TO 65% BY WEIGHT ASBESTOS, 20 TO 40% BY WEIGHT OF COMBUSTIBLE FIBERS AND 2 TO 10% BY WEIGHT ROSIN, AND ALTERNATING LAYERS CONSISTING ESSENTIALLY OF CRUSHED OLIVE STONES AND ALUMINUM PARTICLES DISPOSED ON BOTH SIDES OF SAID BLOCK, SAID BASE, SAID BLOCK, AND SAID LAYERS BEING BONDED TOGETHER INTO A SELFSUSTAINING STRUCTURE, SAID OLIVE STONES CONSTITUTING FROM 10 TO 40% BY WEIGHT OF THE FINAL PRODUCT AND SAID ALUMINUM PARTICLES CONSTITUTING FROM 5 TO 25% BY WEIGHT OF THE FINAL PRODUCT.

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