US1688350A - Method of molding - Google Patents

Description

and has for certain Patented Oct. 23, 1928.-

UNITED STATES CLIFTON D. PETTIS, OF NEW YORK, N. Y. A

METHOD OF MOLDING.

No Drawing.

The present invention relates broadly to the art of molding, and more particularly to the art of forming metal castings in so-called permanent molds, although the utility of the invention is not limited in this respect.

At the present time it is customary in the art to which the present invention relates to provide so-called permanent molds. adapted to be repeatedly used for the production of metal castings. These molds are of such nature as to withstand the high temperature conditions produced by successive casting operations, as distinguished from temporary molds, such for example as sand molds, which are destroyed by a single casting operation.

This invention deals more particularly with molds of the sty-called permanent type,

of its objects a method of treatment of said molds in such manner as to increase their length of life, retain their molding surfaces in more nearly their orig inal state, facilitate the removal of castings, and maintain a lower average temperature of the molds.

. I have found that molds of the permanent type may effectively have their molding surfaces formed either of refractory material, such for example as silicon carbide, or of metal, it being desirable in either case to so construct the molds as to facilitate heat transfer to the outer mold Walls, and then radiation of heat therefrom at a relatively high rate to thereby maintain the Walls of the molding cavity at a temperature lowenough to prevent fusing of the molding surface. In this manner, the length of life of the mold is very materially increased. Repeated experiments, however, have demonstrated the further advantages of producing a protective coating on the molding surfaces of the mold, said coating preferably being of such nature as to preclude the pocketing of air between the coating and the mold walls. and also being ofsuch character that Application filed March 13, 1925. Serial No. 15,360.

same if successful castings are to be formed. Coating a cold mold in the'manner referred to, While possessing certain advantages, is objectionable for the reason that it provides a large amount of volatile matter which, in contact with the hot metal, rapidly vaporizes and thereby increases the volume of gases to be vented. After each casting operation, new oil coated chills have heretofore been applied, or the entire mold has been re-used in exactly the condition inwhich it was left by the previous casting operation.

In accordance with the present invention, I preferably construct a'so-called permanent mold in accordance with any established practice, either of the sectional type or of the solid type, adapted to be manipulated as required by the particular casting to be formed therein. After the mold is set up ready for. the pouring operation, it is preferably treated with a suitable substance, as for example, oil, as heretofore proposed, adapted under the influence of heat to lose certain of its more volatile constituents. Extensive investigations which I have made have proven the possibility of renewing the protective coating on the molding surfaces periodically, as for example, between successive pouring operations, Without any objection able results, and in reality With extremely beneficial results, not only as to the finish of the castings, but also as to preservation of the molding surfaces and increase in the length of life thereof.

These desirable results may be accomplished by the application of a substance, such for example as crude oil, asphalticor tar products, or the like, while the mold is hot, whereby not only is the mold cooled. to some extent, but the more volatile constituents of the substance are immediately vaporized, thereby leaving a molding surface having adhering thereto not only the residue of the substance originally applied, but also the non-"olatile portion of the substance first applied. When oil or similar material is applied to a mold While at a comparatively high temperature, I have found that this residue is apparently of a graphitic, highly refractory nature closely adhering to the mold walls, and even resisting removal by a s raping operation.

for cooling the mold to some extent, thereby maintaining a lower average mold temperature, which is below the fusing temperature of the mold. In addition to this, however, and of even greater importance, is the production of the protective film or coating of a nature such that it is highly resistant to the action of a hot metal and serves to increase the length of life of the mold by preserving the mold walls, without leaving any objectionable volatile constituents.

If desired, there may be combined with the oil a suitable amount of a refractory, heat insulating or heat resisting material, such for example as a powder of silica, clay, bauxite or the like.

I believe myself to be the first in the art to subject so-called permanent molds while in heated condition to repeated a lications of a substance adapted to form a protective tightly adhering coating or film, substantially free from volatile ingredients and having highly heat resistant and refractory properties.

As a substitute for the substances referred to, either to be used separately therefrom, or in combination therewith, I may utilize a mixture comprising fire clay with a suitable amount of sodium silicate and water, together with a desirable proportion of pulverized silica. This mixture may be applied locally to certain portions of the molding surface, as for example, directly opposite the pouring gate, as a protective means. The mixture is adapted to be applied with the molds either in heated condition as left by a previous casting operation, or when the molds are cold, as at the beginning of a pour. This mixture forms a volatile substance within the meaning of my claims. \Vhere the mixture has been applied to a cold mold, the volatile constituents may be driven off in any desired manner. When applied to a heated molding surface the volatile or vaporizable constituents are immediately driven off, leaving a'closely adherent protective coating. Where such a mixture is applied only locally, the hydrocarbon base oil may be subsequently applied to form the completed protective coating as hereinbefore referred to.

The advantages of the present invention arise from the method of cooling molds by subjecting them to the cooling action of a partly volatile substance.

Still further advantages of the invention arise from the formation of a protective heat resistant coating on heated molding surfaces at repeated intervals. during the use of the mold.

I claim:

1. In the method of casting, the step consisting of applying to a molding surface a mixture of fire clay with silica, and thereafter applying oil to said surface and said mixture.

2. In a method of casting, the step consisting of applying to a molding surface a mixture of fire clay with sodium silicate and silica, and thereafter spraying oil onto said surface.

3. In the method of casting, the step consisting of applying to a molding surface a mixture of fire clay with sodium silicate, water and silica, and thereafter impregnating said mixture with a partly volatile refractory material.

4:. In the method of forming metal castings, V

the step consisting of providing closely adherent protective layers of different natures on a molding surface while in heated condition from'a previous casting operation and at substantially the temperature imparted by such previous casting operation.

5. In the method of forming metal castings, the steps consisting of applying a partly volatile substance to a molding surface while at substantially the temperature imparted thereto by a previous casting operation, and thereafter applying to the molding surface a partly volatile substance of a different nature.

6. In the method of forming metal castings, the steps consisting of applying a partly volatile substance to a molding surface while at substantially the temperature'imparted thereto by a previous casting operation, and thereafter applying to the molding surface an impregnating substance of a volatile nature.

7 In the method of forming metal castings, the steps consisting of applying a coating of fire clay and silica to a molding surface, and thereafter spraying a. partly volatile substance onto the molding surface and said coating while the molding surface is at substantially the temperature imparted thereto by a previous casting operation.

8. In the method of forming metal castings,

the steps consisting of applying a coating of fire clay and silica to a molding surface, and thereafter spraying an impregnating substance of a volatile nature onto the molding surface and said coating.

9. In the method of forming metal castings, the steps consisting of cooling and coating a mold by spraying oil under pressure onto a molding surface between successive casting operations.

10. In the method of forming metal castings, the step consisting of spraying oil under pressure onto a molding surface between successive casting operations and while the surface is at substantially the temperature imparted by a previous casting operation.

11. In the method of forming metal castings, the steps consisting of providing a closely adherent protective coating on a molding surface while at substantially the temperature imparted by a previous casting operation, renewing the coating after at least some of the successive casting operations while the mold is at substantially said temperature, and applying to such coating a further coating having different characteristics.

12. In the method of forming metal cast- I ings, the steps consistingof providing a close- 1y adherent protective coating on a molding surface While at substantially the temperature imparted by a previous casting operation, renewing the coating after at least some of the successive casting operations While the mold is at substantially said temperature, and applying to such coat-ing a further coating having" different characteristics and of pregnating nature.

13. In the method of forming metal castings, the steps consisting of cooling and coating a mold by applying oil under pressure to a molding surface after the removal of a casting from contact therewith to effect partial volatilization of such substance and the production of a highly heat resistant coating on the molding surface.

l l. In the method of forming metal castings, the step consisting of applymg oil under an impressure to a molding surface While at substantially the temperature imparted thereto by a previous casting operation to effect partial volatilization of such substance and the production of a highly heat resistant coating on the molding surface.

15. In the method of casting, the steps consisting of applying to a moldin surface a mixture of fire clay with silica, an thereafter applying to said surface and mixture a volatile impregnatin substance.

16. In the method of casting, the steps consisting of a plying to a molding surface a mixture ofv re ,clay with sodium silicate and silica, and thereafter applying a volatile impregnating substance to said surface.

In testimony where I have hereunto set my hand. A

CLIFTON D. PETTIS.