US2145317A - Foundry core binder - Google Patents

Description

Patented Jan. 31, 1939 UNITED STATES FOUNDRY CORE BINDER Harold K. Salzberg, Pittsburgh, Pa., assignor to The Borden Company, poration of New Jersey New York, N. Y., a cor- No Drawing. Continuation of application Serial No. 2,199, January 17, 1935. This application June 15, 1937, Serial No. 148,306

17 Claims.

This invention relates to foundry cores, and more particularly to binding agents for use in making foundry cores. This application is a continuation of my co-pending application Serial No. 2,199, filed January 17, 1935.

More particularly, the invention relates to the binding material used, and to the method of using such material, and the product resulting from such use. While the invention is described as relating to foundry cores, in which connection it will find its largest field of use, it is nevertheless adaptable to other uses in which a binding material is used in preparing conglomerate articles from finely divided inert materials.

In the casting of metallic articles the common method involves pouring molten metal into molds formed of sand or similar material. The majority of castings are so shaped that there must be set into the mold preformed co'res, around and against which the molten metal flows and then sets, so that upon the removal of such cores from the cooled casting the necessary openings in the casting are revealed. Such foundry cores are commonly made of sand as the basic material. The procedure customarily followed in foundry core rooms is to blend, by mixing, a certain small amount of organic binder with sand, temper the mix to the right "feel with water, riddle or otherwise finely divide the wet mix, shape the core by tamping or jolting the mix into molds, commonly termed core boxes, remove the box? either wholly or partially from the shaped green core and, finally, bake the core in an oven. There are many variations in this procedure but the foregoing, in a general way, briefly describes the art of making cores.

It will be readily understood-that the variety of processes involved and the necessity of producing a firm, smooth-surfaced core of accurate shape and measurements, require that the mix, or combination of sand, water and binder, shall have completely satisfactory working properties. That is, it must be of such a nature that it will not stick to the sides of the core box nor to the 45 baking plate or pan on baking, and the green core must not sag before or during baking. Furthermore, in order that the core maker shall be able to work with speed it is desirable that the mix be of a mealy or "crumbly nature. It is also, of course, requisite that the mix contain no. ingredient which may be harmful to the handsof the core maker. A sand mix employing the binder of the present invention complies with all of these requirements.

The requirements which must be met by the baked core are equally as exacting. The baked core must possess sufficient strength 'orrigidity to withstand stresses applied during transfer, storage and placing in the mold. Its surface must be smooth and hard enough to withstand pressure of the metal during pouring. The body of the core must be relatively porous in order that the gases formed during pouring shall escape through the core. To the. end that there shall be a minimum of gas evolved during the pouring, the amount of organic binder in the sand must be maintained at a minimum. Of great importance is the ability of the core while in the mold, before pouring of the metal, to withstand weakening and deformation through action of the moisture in the molding sand. These requirements must be met in varying degree depending upon the size and shape of the core, the amount of handling it must undergo, the type and amount of metal to be poured, and its temperature. The present invention relates to a binder which, when properly combined with sand, will impart to the core such properties that these requirements will be satisfactorily met.

One object of this invention is to provide an improved baked foundry core made with a binding agent having the foregoing advantages and containing a soluble proteinaceous material and a crystallizable carbohydrate.

Another object is the provision of an improved baked core and a method of making foundry cores using-such a binding agent.

I have discovered that a core binder containing suitable proportions of a soluble proteinaceous material and a crystallizable carbohydrate material is especially suitable for making baked foundry cores.

By soluble proteinaceous material is meant a proteinaceous material which is either sufficiently soluble or solubilized so that when, a dispersion of the material in water is dried, a continuous unbroken non-granular film of solids remains. Such a proteinaceous material is also capable of producing a. marked increase in the viscosity of a solution.

Certain specific examples of core binders in accordance with my invention will be hereinafter described to illustrate the invention, but it is to be understood that the invention is in no way limited thereto. Any suitable soluble protein may be employed in combination with the carbohydrate to produce a baked core distinctly superior to cores made with either of these ingredients alone.

Proteins which are naturally soluble, such as gelatin, albumen; or hide glue, may be employed for this purpose. Normally insoluble proteins, such as casein, may be rendered satisfactory by a suitable solubilizing treatment, either prior to use or during the process of making the baked core. One particularly advantageous manner of solubilizing a protein, such as the casein found in milk, is to subject the casein to. chemical reaction with a material which is capable of producing an insolublecalcium salt, as desc ibed go in my co-pending application Serial No. 58,757. For example, fluid milk may be treated with an oxalate, fluoride, meta-phosphate or the corresponding acids prior to drying. Such a solubilizing agent may also be added to dry milk solids or casein so that solubilizing of the protein is effected as, soon as the mixture is moistened. Other solubilizing treatments may be used, however.

A number of materials may be used as carbohydrates, including sucrose, dextrose, lactose, and, in some instances, dextrine may be used. These carbohydrates may be employed in either the pure or commercial forms. I prefer to employ a. crystallizable carbohydrate because such carbohydrates give to the core an improved resistance to moisture, which is important when the cores are to be placed in green sand molds and left over night or longer before the castings are poured.

The use of binder material consisting solely of soluble carbohydrate, as for example, cane sugar, glucose, lactose, etc., or mainly composed of such carbohydrate, as for example molasses, syrups, whey, or concentrations of naturally occurring sugar juices or liquors, e:tc., is disadvantageous for several reasons. Because of the relatively high solubility of such sugars they tend to migrate within the core during its baking, moving from the interior parts towards the outer surfaces where concentration is efiected. While this effect is, in itself, a desirable one, the use of a binder consisting principally of soluble carbohydrate, with the ensuing migration as mentioned, results in the production of a core which is unsatisfactory in that such a core is largely but a shell, the binder, and consequently the strength and hardness of core, being concentrated almost entirely at the core surfaces.

The approximate concentration of binder at various depths in a baked core prepared with 1% by weight of cane sugar in the sand, has been determined by actual test, the results of which show a concentration of binder in the surface layer to almost 2% with practically no binder remaining in the core interior. Similar results are obtained by using molasses, corn syrup or other material largely composed of soluble carbohydrate substance as the sole binder in the sand.

It should be emphasized that while the shell effect is desirable, a core which has a shell structure, with little or no binder remaining in its interior, is not desirable. Such a core offers but little resistance to stresses tending to deform or break the core during handling. Furthermore, the use of such a core in the mold is attended by danger in that the core shell is relatively greatly weakened by moisture absorption from the molding sand with the probability that the shell will collapse on meeting the pressure of the metal.

The shell effect, if not present in an extreme form, is desirable inthe pouring process for several reasons. A shell core has a high degree of permeability and therefore provides more efiicient venting of gases than a solid core; it will the core with strength throughout its cross-section without eliminating the shell'structure, (2)- greatly increases the surface hardness of the core, (3) greatly increases the core strength when measured by applying a load transversely and (4) provides a core relatively much more resistant to the deteriorating effects of moisture in the mold. One major advantage in the use of the compound binder is that the extreme shell effect is reduced to a moderate and safe structure and, by varying the ratio of carbohydrate to protein, the shell effect can either be accentuated or diminished at will. The protein ingredient of such combinations can be best described as serving as the binder for the body of the core, giving cohesion and strength to the inner lying layers of sand.

I prefer to employ a ratio of protein to carbohydrate such that at least about one part of one of the ingredients is present for each four parts of the other ingredient. By way of example, one core binder in accordance with my invention is a combination of substantially equal parts of gelatin and sucrose. A given quantity of a core binder composed of equal parts gelatin and sucrose gives greatly improved results in making baked sand cores as compared with the same quantity of either of these ingredients alone. For example, baked cores made with 0.5% sucrose, and 0.5% gelatin have distinctly superior transverse breaking strength, resistance to abrasion, and resistance to moisture, compared with cores made with 1% sucrose or cores made with 1% gelatin.

Further examples of mixtures for core binders in accordance with my invention are compositions, containing soluble casein and lactose in the proportions of about 20% of soluble casein with about 80% of lactose, or in the proportions of about 80% soluble casein with about 20% lactose. Each of these compositions provides baked cores with unusually good properties. While proportions of soluble protein to carbohydrate of at least one part of one ingredient to each four parts of the other ingredient are preferred, I have found that the best results are obtained by maintaining these ingredients within the proportions of 40 to 60% of soluble protein and 40 to 60% of carbohydrate.

Another example of core binders in accordance with my invention is a combination of solubilized casein and lactose. Casein and lactose occur naturally in satisfactory proportions in milk. Thus, fluid milk in which the casein has been solubilized, or dry milk solids in which the casein has been solubilized, or to which a solubilizing ingredient is added are suited for making improved baked cores in accordance with my invention.

Using milk solids, either dry or liquid, in which the casein has been solubilized, produces baked cores of greatly superior transverse strength and resistance to abrasion compared with cores made with ordinary fluid milk or dry milk solids. Similarly, a mixture of lactose and solubilized casein gives a superior baked core compared with the use of the same quantities of lactose and commercial or insoluble casein.

In the foregoing description, reference has been made to the use of 1% core binder with 99% sand. This invention is not limited to the use of 1% core binder however, and in fact, the ratio of core binder to sand may vary Within wide limits in commercial practice. It is to be understood, therefore, that greater or lesser quantities than 1% of the core binder may be employed. For example, quantities of a core binder in accordance with my invention of less than 1% of the amount of sand may be employed with distinctly improved results.

Core binders of my invention may also be mixed with other materials. Various fillers which do not detract from the valuable properties of the core binders of my invention may be employed to good advantage. A finely divided seed meal, such as soybean meal, peanut meal, or other seed meals are especially suitable for this purpose. Such seed meals are commonly obtained by grinding the residue left after the fat has been removed from oil bearing seeds. Other filler materials which are suitable for this purpose are such materials as sawdust, wood flour, whey powder and the like. The blending of fillers with the core binders of my invention is useful in promoting thorough mixing of the binder with the sand.

Any suitable quantity of filler material may be employed with the soluble protein and carbohydrate. I prefer to employ a composition of core binder containing at least about by weight of soluble protein and carbohydrate to about 90% of filler material. For example, a core binder composed of about 80% soybean meal and of the mixture of soluble protein and carbohydrate, or a binder composed of about 70% soybean meal and 30% of the mixture of soluble protein and carbohydrate are very suitable. Other materials such as whey may be substituted in part or entirely for the soybean meal or other filler employed. When a core binder containing a large quantity of filler is used, a correspondinely greater proportion of the binder should be employed with the sand in making cores.

The usefulness of this binder is not limited to the application of the binder to core sand alone for its characteristics will be equally demonstrable when used in molding sand, particularly in the making of dry sand molds which pass essentially through the same molding and baking processes as the cores. Furthermore, the usefulness is not limited to the application of the binder to sand alone but includes also its application to other inert material of the order of fineness of sand which might be used in making foundry" cores and molds.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

I claim:

1. A binder for finely divided inert material, including soluble crystallizable carbohydrate material and-soluble protein material in the ratio of not less than one part of either ingredient to four parts of the other ingredient.

2. A binder for finely divided inert material, including finely divided sucrose and soluble protein material in the ratio of not less than one part of either ingredient to four parts of the other ingredient/ 3. A binder for finely divided inert material, including approximately equal parts of soluble protein and soluble crystallizable carbohydrate materials.

4. A foundry core binder comprising substantial amounts of soluble proteinand crystallizable carbohydrate.

about 10% of a mixture of soluble protein and carbohydrate, and the balance composed principally of filler material.

10. A foundry core comprising a body of finely divided inert material made by mixing said material with water and a binder comprising soluble crystallizable carbohydrate and soluble protein in the ratio of not less than one part of either ingredient to four parts of the other ingredient, shaping said mixture into a core, and baking said core.

11. A foundry core comprising a body of finely divided inert material made by mixing said material with water and a binder comprising soluble crystallizable carbohydrate and soluble protein, shaping said mixture into a core, and baking said core.

12. A foundry core comprising a body of finely divided inert material made by mixing said material with water and a binder comprising soluble casein, lactose, and filler material, shaping said mixture into a core, and baking said core.

13. The method of making foundry cores consisting in mixing sand, finely divided soluble crystallizable carbohydrate material and finely divided soluble protein material, the latter two ingredients being present in the ratio of not .less than one part of either ingredient to four parts of the other ingredient, moistening the mix with water, forming a green core with said mix, and

' baking said green core.

14. The method defined in claim. 13, the percentages of sand, soluble crystallizable carbohydrate material and soluble protein material used being approximately 99%, 0.5%, and 0.5%, respectively.

15. The method of making foundry cores consisting of mixing sand, finely divided sucrose, and finely divided soluble protein material, moistening the mix with water, forming a green core with said mix, and baking said green core.

16. In a. methd of making baked foundry cores, the steps of mixing finely divided inert material with a binder comprising soluble protein and crystallizable carbohydrate, moistening and shaping the mix into a core, and baking said core.

17. In a method of making baked foundry cores, the steps of mixing finely divided inert material with a binder comprising soluble casein, lactose, and filler material, moistening and shaping the mix into a core, and baking said core.

HAROLD K. SALZBERG.