US2206369A - Foundry sand binder - Google Patents

Description

Patented Juiy 2, id

Y QRY SAND BINDER Harold K. Salzberg, Pittsburgh, Pa.

- No Drawing. Application April 29, 1938,

Serial No. 2%,123

12 Claims.

This invention relates to foundry sand binders, methods of using the same, and to products made by the foundry use of such binders.

In the art of sand-casting metals, cores and 5 molds are employed made of foundry sand bonded with a suitable binder and baked in the desired shape. A great many metal castings .are made by pouring molten metal into molds made of sand, into which have been set preformed cores to provide openings and cavities in the casting of the requisite design. The molten metal when poured into these molds flows against inside and outside surfaces of sand, and usually surrounds the surfaces of the cores.

These cores and frequently also the molds are made by ramming a moistened mixture of foundry sand containing a small proportion of a binder into a core box or around a pattern. The molded sand and binder mixture may be left in the wet or green condition after shaping, but more often the core or mold thus formed is baked in an oven, or otherwise dried, to provide the shaped article with the necessary strength to enable it to maintain its shapeduring handling, and during pouring of the metal.

The foundry sand binder employed should readily mix with sand and should not cause the wet sand to stick to the core box or pattern. It is also desirable to use a binder which provides the wet sand originally with some strength commonly referred to as green bond strength. Where the core is to be dried or baked, the binder mustbe capable of withstanding oven temperature and must be strong enough to hold the grains of sand in the desired rm in the dry state, without employing more than a. very small percentage of binder in proportion to the amount of sand used. Too large a quantity'of binder might produce excess gassing when the casting is poured. In addition, the binder should be selected so that it will burn out of the sand at the proper ratq during the casting. operation and it should not leave the sand in and around the formed casting in such a state that it is difficult to remove from the metal. One object of my invention is to provide an economical foundry sand binder which'satisfactorily meets the requirements of the foundry art to a high degree.

Another object of this invention is to provide an economical foundry sand binder which produces high strengths in a baked sand core, even when used in extremely small amounts in proportion to the sand.

A further object of this invention is to provide baked sand foundry molds and cores having the requisite properties developed by such foundry sand binders,

Another object is to provide an improved core paste for foundry use. fOther objects will be 5 explained and will be apparent from the following description of my invention.

Seed meals, particularly those seed meals high in available protein,. are inexpensive materials whichwould be very valuable alone as foundry 10 binders if they possessed a higher binding value for sand. I have discovered that such seed meals may be greatly improved in their binding properties by the addition of a suitable conditioner or modifying agent. Outstanding among these mod- 15 ifiers are the water soluble oxalates, borates, and fluorides. The metaphosphates and sulphates also have a very advantageous effect, and such phosphates, carbonates, and chlorides as trlsodium phosphate, soda ash and sodium chloride 20 produce substantial improvements in the action of the seed meals as foundry sand binders. The modifiers employed are preferably the water soluble salts. The improved core binders of my invention may be employed in relatively small 5 amounts with the sand, thereby preventing excessive gassing during pouring of the castings. The amount of binder used will depend on the particular foundry requirements and will gener-- ally be about 1 to 2% by weight of the sand.

One of the particular advantages of my invention is the fact that these modifiers may be employed to good effect with the spent or Icy-product seed meals, i. e., the seed meals remaining after commercial extraction of the oils which these 011 3'5 bearing seeds contain in their original state.

By the term seed meals as used herein,'I intend to include those seed meals which are relatively high in protein, such as soy bean, peanut,

pea, castor bean, cottonseed and linseed meal, as 40 4 distinguished from the flours or meals of corn, wheat, barley, oats, and the like. The meals may either contain all of the original oil or have part or all of the oil extracted therefrom. For economic reasons, the latter will be preferable. 5

The foregoing seed meals useful for purposes of my invention have a protein content of more than about 20% on an oil free basis. 1

I prefer to employ those seed meals which have not been subjected to high'temperatures, because 50 this reduces the quantity of available water soluble protein in the final product; A seed meal best suited for purposes of my invention is one has not been subjected to a temperature materially above 135 F., as occurs in the hot pressing of certain seed meals to extract oils therefrom.

The seed meals employed are also preferably finely divided; in general, the finer the seed meal is ground, the higher core strength may be obtained by the used of the modified seed meal as a core binder.

With regard to the conditioner or modifying agent employed, I prefer to use the water soluble salts, and have found that the best results are obtained with an oxalate, or a borate such as borax. For example, the transverse breaking strength of standard baked test bars made with foundry core sand and 1% by weight of a binder comprising a. seed meal modified by sodium oxalate is more than double, and in some cases more than three times the strength of test bars made with the same proportion of the same seed meal alone. p

' The proportion of the modifier or conditioner added to the seed meal should be adjusted according to the grade of seed meal and the particular modifier employed. With a low grade seed meal, in general, more of the modifier is required. When a high grade seed meal is employed, i. e., a seed meal from which the oil has been extracted by a solvent. leaving a higher proportion of water soluble protein, a smaller proportion of the oxalate, preferably not more than about 6%, is employed. With such high grade meals, the maximum effect of the oxalate appears to be obtained using about 4% of an oxalate based on the weight of the seed meal. As the proportion of modifier is increased beyond thepoint of maximum effect, the strength of baked cores made with the core binders progressivelydecreases. The other salts are less effective than'the oxalate and produce their maximum effect when employed in somewhat larger amounts than the oxalates. For example, sodium metaphosphate used withsome seed meals may be required in'theproportion of 11% to produce its maximum effect, The modifiers of my invention may be employed effectively in amounts up to about 12% of the seed meal.

I Other improvements effected by using modified seed meals in accordance with my invention over the use of seed meals alone are the great increases obtained in dry tensile strength, resistance to 1 abrasion, and green bond strength in the sand cores. Any suitable foundry sand may be employed in accordance with my invention.

' The improvements obtained by using a mixture of a seed meal with a modifying agent as a core binder are not limited to the use of the seed meal and modifier alone,-but'these improvements also are obtained when the seed meals are used in sand containing other binders, such as flour, waste sulfite liquor, molasses and the like. The presence of these other ingredients does not exclude the enhancing effect of the oxalate or other modifier on the seed meal employed.

A particularly advantageous and unique mixture of binders is a core binder comprising a mixture ofmilk solids with a seed meal and a modifier in accordance with-this invention. The

combination of a seed meal and milk solids with seed meal-and modifier and of the milk solids 75 and modifier alone. This unusual eflect is obseed meals in virtually any proportions.

I II III Skim milk powder 80 20 Soy bean flour. 20 80 Sodium oxalate. 4 5 6 The amount of modifier used with these mixtures should be based on the total weight of seed meal and/or milk solids instead of on the quantity of seed meal alone. By milk solids" I mean either dried milk solids such as skim, partially skimmed or whole milk powders, the corresponding fluid milk products in a natural or condensed state, or mixtures thereof.

' I prefer to employ a dry mixture of the foregoing ingredients, although the modifying agent may be added to the sand before or after the seed meal flour is added, or the modifying agent may be added to the water used in tempering the sand, or with water which is swabbed or sprayed on theformed core or mold before it is baked. v

While I do not wish to be limited by any theory of the operation of these modifying agents,

I believe that the nature of the action on the" seed meals is a peptizing of the protein content thereof. The action of the'modifying'agents on the milk solids may be of a different or of the same character. v

In general, .the strengths of the baked core produced using-a mixture of milk solids with a seed meal and modifying agent arehigher, the greater the proportion of milk solids employed. The particular proportion of these ingredients may be adjusted depending upon the strengths desired and the costs of the two ingredients.

A small amount of the order of 1 to 3% of an oil, such as a low viscosity mineral oil, may be added with good eflect to a core binder in accordancewith my invention. This has some value in eliminating dusting of the product and removing stickiness of the sand and core binder mixture after-it, has been moistenedt The workability of the moistened sand and binder mixture is also improved by this addition.

The core binders of this invention may also be employed in combination with a core oil where free flowing. characteristics of thesand are desired, as in the use of automatic core making machines. Under these conditions, I prefer to add a salt of. nickel or iron to'the mixed core binder in order to take full advantage of the greatly increasedstrengths obtained by the core binders of my invention. The use of a mixture-for example, of 1% of an ordinary core oil and V of 1% of a binder in accordance with my invention produces a free flowing sand. The ingredients of my seed meal binders however, have an inhibiting effect on the drying of the core oil, thereby resulting in lower core strengths than should be obtained with such mixtures. The addition of a small percentage of an honor nickel salt which may be organic or inorganic, oil or water solubl'e these metals appear to have some catalytic action and may be included in any core binderof my invention whether or not it is actually used with a core oil, since they do not submantially injure the strength of such binders when used in small amounts of the order of or less. If desired, the oxalate or other modifying radical may be included in the iron or nickel salt, although only such combinations as are water soluble should be employed. Ferric oxalate or ferric ammonium oxalate are examples of useful salts of this nature.

A-preferred composition of core binder in accordance with my invention is as follows:

Parts by weight Roller dried skim milk powder 40 Soybean flour 60 Sodium oxalate- 6 Preservative (Dowicide) a Mineral oil 2 Ferric sulfate 3 The core binders of my invention, particularly those including milk solids, also are useful as a core paste. The above composition, or'other modified se'ed metal binders, may be as a paste directly upon admixture withwater for sticking parts of cores together. The usefof this material as a core paste is greatly enhancedhow- I Parts' Silica flour (finely ground) '75 Skim milk powder l5 Soybean meal fiour Sodium oxalate"; 1% Ground rosin 5 Borax--- 1 Mineral oil 1 In such a paste, the inert material, whichmay be clay. or silica flour, lends heat resistance to the joint, providing higher joint strength during and after pouring of the metal. The addition of rosin improves the water resistance of the Joint and makes the paste formed with water a little thick,- er. The sodium oxalate and bore: act, as previously' described, to improve the effect of the skim milk powder and seed metal. The mineral oil serves to reduce the dustinessof the dry paste and also provides a smoother product for brush- When employing the composition of my invention as a core paste, about two parts of the solids may be mixed with one to two parts water. The particular amount of water will probably vary, depending on the particular use for the paste.

a A highly fluid paste is desired when ease of application is required, as when mechanical means are employed for applying. the paste. On the other hand, a very thick putty may be needed especially when sealing the core joints. A wide range of consistency of paste is possible by merely regulating the ratioof water to dry material.

I have also found that the foundry sand. bind;- ers of my invention, and more particularly binders containing finely divided inert material such as the product obtained by using the above formula for core paste are useful as a base for coatings for cores and molds. Such coatings'are commonly referred to as washes. A thin suspension of the material in water, for example, one pint of dry paste solids to two pints of water,

can be used to advantage in brushing or swabbing cores or molds. The purpose of such coatings is to provide a surface more resistant than the bare sand surface to the heat of the metal, and their use makes for a smoother finish on the casting. The wash prepared with the materials of the above mixture exhibits the eflfect of the chemicals on the mixture of milk solids and seed meal flour in providing a hard, non-chalky, strongly adherent coating.

The purpose of the borax in this formula becomes twofold when the suspension is thin If enough for use as a wash. In addition to improving the adhesive power of the mixture of milk powder and seed meal flour, borax also acts as a suspending agent for the silica particles, thus overcoming the natural tendency of the silica to settle out and to form a hard sediment when the suspension is allowed to stand undisturbed for long periods of time. For this reason, I prefer to employ borax, with or without some other modifying agent, when the foundry binders of my invention are used with a thin suspension of'flnely divided inert material such as silica.

By the term foundry sand binder I intend to include such foundry uses for the products of my invention as core binders, core pastes, and core or mold washes for which these products are particularly well suited. 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 foundry sand binder comprising finely divided seed meal containing more than about protein on an oil free basis, milks solids, and an effective amount up to about 12% ofthe combined'weight of milk. solids and seed meal of a soluble salt: of the class consisting of oxalates, borates, fluorides, phosphates, sulfates, carbonates anckchlorides.

2. A foundry'sand binder comprising a finely divided seed meal of the group consisting of soy bean, peanut, pea, castor bean, cottonseed, and linseed meals. m lk solids, and a small amount not more than about 10% by weight of a. water soluble oxalate.

3. A foundry core binder comprising finely divided soy bean'meal, milk solids and a water soluble oxalate in the proportion of about 2 to.

6% of the total weight of soy bean meal plus milk solids.

4. A foundry sand binder comprising finely divided seed meal containing more than about 20% protein on-an oil free basis, a small amount of a salt of a metal of the group consisting of iron and nickel, and an effective amount up to about 12% of a "water soluble salt of the class consisting of oxalates, borates, fluorides, phosphates, sulfates, carbonates and chlorides.

5. A foundry sand binder comprising finely divided seed meal containing morethan about 20% protein on an oil free basis, milk solids, a small amount of a salt of a metal of the group consisting of iron and nickel, and an eflective 4 aaoasea 10% of the total weight of seed meal and milk amount up to about 12% of a water soluble salt of the class consisting of oxalates, borates, fluorides, phosphates, sulfates, carbonates and chlorides.

6. A foundry sand binder comprising finely divided seed meal containing more than about 20% protein on an oil free basis, milk soilds, core oil, a small amount not greater than about 5% of an iron salt, and an effective amount up to about of a water soluble oxalate.

7. A foundry core paste composition comprising principally finely divided inert material, a smaller proportion of a finely divided seed meal containing more than about 20% protein on an oil free basis, milk solids, and a water soluble oxalate in an amount not substantially greater than 10% of the combined amount of milk solids and seed meal.

8. A foundry core wash composition comprising principally finely divided inert material, finely divided seed meal containing more than about 20% protein on an oil free basis, milk solids, and a small amount of borax.

9. The method of preparing material for foundry use comprising working into a substantially uniform plastic mixture finely divided inert material, seed meal containing more than about 20% protein on an oil free basis, milk solids, and a water soluble salt of the class consisting of oxalates, in an amount not greater than about solids.

10. The method of preparing material for foundry use comprising working into a substantially uniform plastic mixture finely divided inert material, seed meal containing more than about 20% protein on an oil free basis, milk solids and a water soluble oxalate, the oxalate being present in an amount of about 2 to 6% of the combined weight of seed meal and milk solids.

11. A process of making a foundry core comprising preparing a moistened mix of foundry sand and a binder comprising finely divided seed meal containing more than about 20% protein on an oil free basis and milk solids modified by a water soluble salt from the class consisting of oxalates, borates, fiu'orides, phosphates, sulfates, carbonates and chlorides, shaping said mix to form a core and baking said core.

12. A baked foundry core comprising foundry sand held together in a coherent mass by a binder resulting from baking a moistened foundry sand mix containing finely divided seed meal containing more than about 20% protein on an oil free basis and milk solids modified by a water soluble salt from the class consisting of oxalates, borates, fluorides, phosphates, sulfates, carbo nates and chlorides. I

HAROLD K. SALZBERG.