US2525175A - Foundry composition and method of making same - Google Patents

Description

Patented Oct. 10, 1950 FOUNDRY COMPOSITION AND METHOD MAKING SAME Naaman Henry Keyser, Los Alamos, N. Men, as-

signor, by mesne assignments, to Eastern Clay Products, Inc., Indiana, Pa., a corporation of Maryland No Drawing. Application August 13, 1947, Serial No. 768,489

4 Claims. 1

My invention relates to a method of treating compositions of matter and, in particular, concerns the treatment of foundry sands, and the production of foundry compositions, so as to impart new and improved qualities and characteristics thereto.

Among the objects of my invention is to provide a method of treating foundry sands to impart thereto such qualities that they will not burn on or stick to castings poured in molds comprised of such sand, will give rise to a predominantly reducing atmosphere during the course of pouring the molten metal into the mold, and will display high green strength and controlled reduced retained strength, with high degree of porosity; which sands, while perfectly compatible with conventional binders, require the addition of but a small quantity of such binders to adapt them admirably for practically all conditions of foundry practice giving improved tamping and flow qualities; which method is itself simple and rapid, requiring the use of but a minimum amount of manipulative steps, themselves requiring but limited skill.

All these and many other highly practical objects and advantages attend upon the practice of my invention, part of which will be obvious and part of which will be pointed out more fully hereinafter during the course of the following description.

My invention accordingly may be seen to reside in the several procedural and manipulative steps and in the association of materials, as well as in the relation and combination of each of the same with one or more of the others, as de scribed herein and set forth in the accompanying claims.

As conducive to a more thorough comprehension of my invention, it may be noted at, this point that a large number of vexatious problems are introduced in the selection and utilization of foundry sands and compositions. Practical utilization almost invariably represents some empirical compromise between incompatible and inconsistent characteristics. An ideal composition will have high green strength, low retained strength and a high degree of porosity, will be readily fiowable so as to be tamped tightly about the pattern, and will take sharp impressions and definitions from the pattern, without drying of the composition or crumbling at the edges, and

will display a high degree of recoverability for subsequent and further reuse. Additionally, such ideal composition will display little, if any, tendency to burn on or stick to the poured castings, and will greatly facilitate the production of uniform sound castings, free of surface holes and the like, and requiring a minimum of blast cleaning, grinding or further surface treatment following removal from the mold. There is the further and additional requirement of such ideal foundry compositions that they be readily and inexpensively produced with rapid, simple and inexpensive manipulative steps, minimum in number and characterized by ease of fulfillment, and which involve the use of readily attainable and inexpensive materials. In actual practice, foundry compositions which are now practically obtainable fall far short of these qualities.

The high green strength which is so necessary for sharp definition and strong molds is frequently accompanied by high dry and retained strength. This factor, in many classes of work, is undesirable, resulting in difficult breakdown and removal of the mold from about the formed castings, and perhaps setting up internal strains causing rupture or otherwise damaging the casting, with attendant high percentage of rejections. Imparting high green strength to the mold composition through the addition of a suitable refractory or non-refractory binder frequently occasions decrease in the porosity of the composition, so that the mold is unable to vent the rapid accumulation of heated vapors and gases which are evolved shortly after the pouring of the molten metal.

Moreover, ordinary foundry compositions display a tendency to stick to and burn on to the poured castings resulting in imperfect surface detail, high cleaning costs and appreciable defects in the surface finish thereof with accompanying high percentage of rejections, attended by rising production costs.

Much work has been directed over a number of years toward the solution of this latter problem. Dry pulverized pitch, dry sea coal and other dry carbonaceous materials have been added to foundry sands with the thought of producing a coating thereon such as would tend to retard the penetration thereinto of the molten metal and would prevent the sticking on and burning on of the sand to the poured castings. Moreover, it was thought that the production of a predominantly reducing atmosphere at the moment of, and slightly following the pouring of the molten metal would tend to retard such burning on and would result in castings of improved surface de- Another method of treatment giving rise to rather satisfactory castings has been to coat the particles of sand with carbonaceous material dissolved in a solvent, the treated solvent being 1ntimately mixed with the sand and the sand then being heated to drive off the solvent. In subsequent use, additional solvent was added, sufficient to make tacky the surface of the particles of sand. This process, however, leaves much to be desired due to the high costs of materials, the time involved, and the necessity of skilled labor.

An important object of my invention is to diminish in large measure the disadvantages and defects as heretofore incurred and now existing, and in so doing to provide a method of producing foundry sands and compositions which is simple, efficient, economical and rapid in itself, involving a minimum number of manipulative steps, using only inexpensive materials, requiring a limited quantity of labor of moderate skill, and resulting in sands and foundry compositions which display high green strength coupled with high degree of porosity and with moderate and controlled dry strength, resist detrimental drying out and sharply retain the details of the pattern.

Another important object is to permit ready recovery of used foundry compositions with but little loss of material, and reconditioning the same for subsequent use with but minimum additives of carbonaceous ingredients.

Basically, my invention may be envisioned as comprising suspending a suitable carbonaceous material, non-thermal setting in nature, in a water-bentonite vehicle. I find swelling western bentonite to be satisfactory. The bentonite, present in but extremely small proportion, serves to hold the carbonaceous material, not in solution, but in suspension in the composition thus produced. In the absence of the bentonite, the carbonaceous material would promptly settle out from the water. The suspended material is then intimately mixed with foundry sand, whereupon the carbonaceous materials uniformly coat each particle of the sand with a thin coating of determined thickness. This coated sand is then dried in any convenient manner to fix the coating on the grains. Conventional bonding clays are added as may be required.

The sands thus coated display admirable re sistance to penetration of the finished mold formed thereof by the molten metal, and at the same time effectively resist substantially all tendency towards burning on or sticking of the sand to the poured casting. The carbonaceous material contributes toward this result by insuring a predominantly reducing atmosphere at and shortly after the time of pouring the casting from the molten metal. It is found that by using foundry sands thus treated, the flow and lay of the molten metal is substantially unretarded. The coating does not impair in any way the green strength of the sand, nor does it appreciably increase the dry strength thereof. The porosity of the sand is substantially unimpaired, whereby all gases and vapors flashed at the time of pouring are quickly vented without danger, either to the mold or to the casting.

Finally, concerning the general description of my invention, I find that while the addition of kerosene to ordinary foundry sands o1- foundry sands treated in the ordinary manner has the tendency to weaken the green strength of the sands to the point where they are substantially unusable; quite on the contrary, the add t on of small quantities of kerosene or other luck-,

greatly increases the green strength of the treated sands to the point where substantially lesser quantities of binders are required. This increases the porosity and permeability of the foundry compositions, a most highly advantageous result. Moreover, tamping and flow qualities of the composition are improved, and the composition responds faithfully to the detail of the pattern. Since there is less tendency of the kerosene-treated sands to dry out, crumbling at the edges of the mold is appreciably lessened.

Referring now more particularly to an illustrative embodiment of my invention, I provide an admixture of about 43% resin, water and about 2% of bentonite. The resin may be any suitable heavy hydro-carbon residue with the prerequisite that the same be non-thermal setting in nature. As typical illustrations of suitable petroleum products may be listed asphaltites, hydro-carbons, carbonaceous resins and the like. In the preferred embodiment, the resin should be a high-carbon, low-hydrogen, hydro-carbon such as that produced from Venezuela crude oil and known under the trad name of Vanadiset. The high carbon content with low hydrogen content I find particularly desirable in resisting scaling of the casting and buming on of the sand.

Vanadiset is a non-thermal setting petroleum pitch which is substantially free of products that are volatile below about 550 F. It is black in the mass, fractures conchoidally and gives a brown streak on porcelain. The specific gravity at 77 F. is about 1.12 and the molecular weight about 3200. It softens at 170 F. to 340 F. and is soluble in carbon disulphide, benzene and other aromatic solvents. Vanadiset" essentially consists of asphaltenes 20% to 70%, as-

phaltic resins 5% to 15%, and oil constituents 26% to 51%, with carbenes not over about 1%. Chemical analysis reveals that it contains about 21% to 64% unsaturated hydrocarbons, with the fixed carbon content amounting to about 36% to 18% and the hydrogen content about 9% or less. The ash content is less than of which vanadium is the principal constituent. (See, United States Patent 2,409,437 and the Bulletin of October 1, 1947, of the Wilson Carbon Company, Inc., East 42nd Street, New York 17,

New York.)

In preparing my treatin agent, bentonite is first mixed with water, so that a colloidal solution is provided. The bentonite serves as a carrier' for the subsequent petroleum additive, suspending the latter intimately in the aqueous vehicle without tendency of the additive to precipitate out. At the same time, analysis shows that no chemical reaction takes place between the petroleumadditive and the other elements. The small percentage of bentonite is found, however, to insure wide dispersion of the petroleum residue throughout the aqueous solution. Thus, the carbonaceous material is brought into intimate contact with any sands or the like through which it is caused to mix, and will deposit thereon in intimately clinging and uniform coating.

Following the preparation of a suspension of the type described, I find that a suspension of asphaltite with bentonite gives best results. I add the suspension to the sand, intimately mixing the same therewith in a quantity sumcient to bring about a deposit oi carbonaceous material on the sand to the extent of about 1-3% by weight of sand. This sand is then dried in any convenient manner. Any conventional binder may be added.

Sands treated in accordance with my invention are found to have appreciable green strength with required moderate retained strength. They display ready flow and tamping qualities, and being flowable, take sharp impressions. Tendency towards marginal crumbling is resisted. The carbonaceous coating resists the penetration of the molten metal into the body of the mold; and perhaps due to the reducing atmosphere which is achieved in the region of and at the time of pouring the molten metal, prevents the burning on and sticking of the sand particles to the surface of the castings. Cleaner, sharper castings are produced, free from surface scale and other defects, and requiring but a minimum of subsequent grinding and pickling to bring them into condition for use. A uniform coating of the sand particles is achieved.

My process is much cheaper than where a petroleum product is dissolved in a solvent. No

loss of solvent is involved, and the manufacturing cost in preparing a solution is avoided. On the other hand, the method is much superior to dry mixing the carbonaceous material with the foundry sands, since a uniform coating is achieved rather than the occasional and spotty contact resulting from the dry method.

As previously noted, the addition of kerosene or some similar light petroleum product to the coated sands gives rise to further desirable results. about 1% by weight of the bentonite-water suspension to about 25% by weight. The preferred proportion I find to be about 15 While the foundry sands produced by the foregoing procedure display the characteristic highly advantageous properties hereinbefore recited, I find that there are instances in which other specialized properties are desired. In this connection, I find that the treated sands are entirely compatible with the usual binders and find, for example, that any of the usual binders may be added as may be necessary for the strength and qualities which are required. Asa typical instance, I may add about 2-4% by Weight of southern bentonite, 2 -5% by weight of western bentonite, or 612% by weight of fire clay. Cereal binders, silica flour, wood flour, or other sand conditioning agents may be added, as desired. Increased green strength resulting from the use of such binders attends upon such practice.

It is to be noted that in no instance is the quantity of clay additive sufficient to effect detrimentally the porosity of the mold or to objectionably increase the dry strength of the latter. The

molds readily break up and the resulting sand is subject to screening and subsequent reuse.

I find that in practice, a, substantial quantity Such kerosene additive may vary from of the petroleum coating remains on the sand,

subsequent to use, so that upon the admixture of" but a small additional quantity of resin thereto, I

the used and screened sands are thoroughly conditioned for reuse.

used sand, intimately admixing the same there- Y a'I admix about one.) tenth to three-fourths of one percent of a suit with and thereby conditioning the same .for sate isfactory reuse.

The worker in the art from the foregoing that can readily appreciate my new method is sim--. 75 sand to coat the discrete particles of the same,

- residue,

pie, certain and entirely predictable in results.

'I'hepetroleum residue is'thoroughly carried in,

ried onto the sand particles isnegligible and does not in any way detrimentally afiect the functioning of the latter. No decrease in porosity is observed therefrom. Inasmuch asthe heavy petroleum residue employed is non-thermal setting in nature, it does not case-harden" in operation, and the sand particles maintain their desirable properties for reuse.

Substantial resistance is displayed to tendency of the sand to burn on or stick to the castings, so that perfect castings are readily obtained with minimum number of rejects, and requiring but limited surface cleaning and grinding. The method is extremely rapid,- the coating suspension is prepared readily and simply with mimmum requirement or time and with minimum use of materials, and these simple and inexpensive in themselves. Similarly, the admixture of the coating suspension to the sand is likewise carried out with a minimum of complexity, the sands being completely coated in rapid and efficient manner. Reclaiming and reconditioning the sands for repeated reuse is readily accomplished. All these and many other highly practical and advantageous results follow upon the practice of my invention.

It is apparent from the foregoing that many modes of realization will readily suggest themselves to those skilled in the art, once the present procedure is disclosed, and that similarly, many modifications of the present embodiment will likewise suggest themselves, all'falling within the scope and sphere of my invention. Accordingly, I intend that the foregoing disclosure be viewed as an illustration and not as a limitation.

I claim:

1. Treated foundry sands possessing nonburning-on properties, comprising discrete particles of silica sand, and a dried coating on the surface of the sand particles initially amounting to about 2% by weight of sand and itself consisting of about 2% bentonite, 43% powdered vanadiset and 55% water from which the water is removed. I

2. Treated foundry sands possessing nonburning-on properties, high green strength and strength, comprising admixing slightly less than one-half by weight of powdered vanadiset with slightly more than one-half by weight of water and a small amount of bentonite, to place the vanadiset in intimate suspension, mixing with kerosene added to the 7 8 then drying the coated sand, and adding kero- REFERENCES CITED sene to the coated and dried sand. I

4. A foundry mold composition having high"""" z g ig g gzf gg are of record m m green strength, reduced dry strength, good porosity and minimum burn-on properties comprising 5 UNITED STATES PATENTS discrete particles of treated silica sand having Numb r Name Dat coatings thereon consisting of powdered vfl fl- 729,617 Link June 2, 1903 diset," bentonite and water, said coatin s 1,127,523 Roy Feb, 9, 1915 amounting to about 2% by weight or the sand 1,5 1,95 Thomas 17, 1925 and being substantially uniformly dew-s d On 10 2,159,952 Jones May 23, 1939 the surfaces or the individual sand pa ti l s. n 2,162,059 Chedic June 13, 1939 a binder selected from the group consisting of 2,230,939 Dunbeck Feb. 1; 1941 about 2% to 4% by W ght of Southern be 2,409,437 Lacrosse Oct. 15', 1946 tonite, about 2 4% to 5% by weight of w r 2,432,702 Wallace Dec. 16, 1947 bentonlte, and about 6% o 12% by wei ht of fir 15 2,444,413 Weston July 6, 194a clay, intimately mixed with said treated silica sand.

NAAMAN HENRY KEYSER.

Claims (1)

1. TREATED FOUNDRY SANDS POSSESSING NONBURNING-ON PROPERTIES, COMPRISING DISCRETE PARTICLES OF SILICA SAND, AND A DRIED COATING ON THE SURFACE OF THE SANDD PARTICLES INITIALLY AMOUNTING TO ABOUT 2% BY WEIGHT OF SAND AND ITSELF CONSISTING OF ABOUT 2% BENTONITE, 43% POWDERED "VANADISET" AND 55% WATER FROM WHICH THE WATER IS REMOVED.