US1962490A - Article and method of casting the same - Google Patents

Description

June 12, 1934. 51; FAHLMAN 1,962,490

ARTICLE AND METHOD OF CASTING THE SAME Filed Oct. 12. 1931 2 Sheets-Sheet 1 INVENTOR T 5, Everett GCFahlman, i BY ATTORNEYS June 12, 1934. E. G. FAHLMAN 1,962,490

ARTICLE AND METHOD OF CASTING THE SAME Filed Oct. 12, 1931 2 Sheets-Sheet 2 INVENTOR Everett G. Fa/hlman Em i Mk ATTORNEY 5 Patented June 12, 1934 UNITED STATES PATENT OFFICE ARTICLE AND METHOD OF CASTING THE SAME poration of Ohio Application October 12, 1931, Serial No. 568,294

10 Claims.

., a method of forming the same.

The casting of aluminum and alloys thereof in permanent (usually iron) molds involves many problems due to the high crystallization shrinkage of aluminum and to the relatively.

.rapid chilling of the casting metal in the permanent mold. The difiiculties are intensified when the casting to be formed has portions of relatively thin section and other portions of relatively heavy section, and particularly when the changes in section are relatively abrupt, due to the difiiculty of feeding the heavy section during solidification thereof, and the tendency for the formation of cracks and shrinks at the portions of the casting adjacent the junctions of the heavy and thin sections. Such feeding has ordinarily been accomplished by locating sprues conveniently adjacent to the heavy section whereby molten metal readily may be transmitted from the sprue cavity to said heavy section during the solidification of the metal therein. In certain cases, however, it has been difficult or impossible, due to the shape of the casting, to part the mold and hence to locate sprues adjacent saidheavy sections, wherefore it has not been feasible or possible to produce such castings in permanent molds.

An object of this invention is to provide a new and novel casting of aluminum or alloys thereof having improved mechanical and physical characteristics.

A further object is to provide a new and novel composite cast article whereby aluminum castings of hitherto diflicultly cast shapes readily may be formed.

Another object is to provide an aluminum or alloy casting having heavy and thin sections, and having a homogeneous exterior of uniform fine grain structure.

A further object is to provide an aluminum or alloy casting having abrupt changes from light to heavy section and having improved characteristics of strength, solidity and homogeneity.

A further object is to provide .a chill cast composite aluminum or alloy casting of integral uniform exterior and of great structural soundness.

Another object of my invention is to provide an advantageous method of forming from alumi- .num and alloys thereof castings having relatively abrupt changes from thin to heavy section.

A,- further object is to provide an improved method of casting aluminum or alloys thereof in permanent molds to form castings of nonuniform section.

Another object is to provide a method of forming in permanent molds, without the aid of feeding sprues, aluminum or alloy castings of widely variant section and of solid non-porous fine-grained metal.

Other objects of the invention will be apparent to those skilled in the art from the disclosures herein made.

My invention contemplates the formation from aluminum or alloys thereof of composite castings wherein a metal insert of substantially the same composition as the remainder of the casting forms the bulk of the interior mass of an enlarged or heavy section of the casting, and wherein the exterior of the cast article is unitary and substantially encloses the insert. The casting is formed by suitably supporting the insert in the casting cavity of a permanent mold, and by pouring the casting metal which is to define the exterior of the casting around said insert to enclose the same and embody said insert within the casting. The insert is preferably of substantially the same composition as the exterior of the casting in order that the entire casting may be homogeneous and in order that the casting may be treated as and may act as a unitary structure, and furthermore in order that the expansion and contraction of the casting may be uniform. Furthermore, the insert preferably is formed in a permanent mold in order that it may have a grain structure and mechanical characteristics closely approximating that of the remainder of the casting, although in certain cases inserts formed otherwise, such as by sand-casting or as by pressing, forging, rolling, etc. may be satisfactorily employed.

The insert is preferably of such dimensions that the thickness of the casting metal enclosing the insert and the thickness of the casting metal forming the remainder of the cast article, will be of substantially the same order of magnitude. Thus, the metal to be cast in the final casting operation will be of relatively uniform section, and the finished article, although of non-uniform section and having abrupt changes of section, will be actually formed by an exterior casting of substantially uniform section, with the resulting advantage of uniform fine grain structure and correspondingly increased mechanical and physical properties.

The metal insert furthermore constitutes also a chill to assist in cooling uniformly the metal cast around the insert, whereby the metal forming the exterior casting may be relatively uniformly chilled throughout its extent. The insert and the metal cast therearound thus constitute together for all practical purposes a unitary cast construction of unusual solidity and rigidity.

In the drawings, Figure 1 is a perspective view partly broken away, of a casting formed in accordance with this invention;

Fig. 2 is a plan view partly in section, of a casting shown in Fig. 1;

Fig. 3 is a section on line 3-3 of Fig. 2;

Fig. 4 is a plan view of the insert shown in Figs. 1 and 2;

Fig. 5 is an elevation of the insert shown in Fig. 4;

Fig. 6 is a vertical section through a permanent mold showing the insert in place for the casting operation;

Fig. 7 is a horizontal sectional view through the mold illustrated in Fig. 6 showing the insert;

Fig. 8 is a plan view illustrating a modified form of casting contemplated by my invention;

Fig. 9 is a sectional view taken on line 99 of Fig. 8;

Fig. 10 is a fragmentary sectional view corresponding to Fig. 6 showing a modified form of insert Fig. 11 is a horizontal section through the mold shown in Fig. 10 showing the insert;

', tively abrupt.

Fig. 12 is a perspective View of the insert shown in Figs. 8 to 11;

Fig. 13 is a sectional view similar to Fig. 9 showing another modified form of insert; and

Fig. 14 is a fragmentary plan view of a casting embodying the insert shown in Fig. 13.

In Figs. 1, 2 and 3 I have shown a cast article 1 such as contemplated by my invention formed from an aluminum alloy in a permanent mold. The casting 1 is shown as having a portion 2 of relatively thin section and relatively great extent. Well away from the edges of the casting is shown a switch box mounting 3 of relatively heavy section, the change in section from the mounting 3 to the portion 1 being rela- The heavy section forming the mounting 3 is shown as comprising an aluminum alloy insert 4 and an outer layer 5 integral with the remainder of the casting. In the mounting 3 are shown apertures 6 and '7 arranged to receive pins, screws or the like, said apertures 6 and 7 being formed by the apertures 6 and '7 in the insert 4, and apertures 6 and 7 in the outer layer 5. The insert 4, as shown, is a permanent mold casting of the same composition as the remainder of the casting 1, and as shown is of substantially the same shape as the exterior of the mounting 3 and of substantially uniformly smaller dimension, such that the thickness of the outer layer is of about the same thickness as that of the portion 1.

In Figs. 6 and 7, I have illustrated the manner of casting the article 1. Thus, the mold sections 8 and 9 are shown as shaped to define the casting cavity 10, sprue cavity 11, and communicating gate 12. The mold section 8 is shown as carrying the pins 13 and 14 which extend into the supplemental recess 15. The pins 13 and 14 are arranged to engage with the apertures 6 and '7 in the insert 4 to support the said insert in molding position to form the casting 1. The pins 13 and 14 serve the double purpose of holding the insert 4 in the proper position within the mold, and also serve as cores so that the finished casting may be provided with the apertures 6 and '7. The casting metal is poured into the spure cavity 11 to fill the casting cavity 10, the casting metal surrounding the insert 4 and incorporating the same within the casting.

In Figs. 9 to 12, inclusive, I have shown a modification of the invention wherein in the finished casting the insert extends to the outer surface of the casting. Thus, I have shown a portion of the casting 16 having a relatively thin section 17 and a heavy boss section 18 disposed relatively remote from the edges of the casting 16. The boss section 18 is shown as comprising an insert 19 and an outer portion 20. The insert 19 is shown as comprising a substantially pyramidal base portion and an extension 22.

The method of forming the casting 16 is indicated in Figs. and 11 wherein the mold sections 23 and 24 are shown as recessed to define a casting cavity 25 including a recess 26 in the mold section 23 to form the boss 18. A recess 27 is further provided in the mold section 23 to receive the extension 22 of the insert 19 to support said insert in molding position. After the casting operation has been completed the extension 22 may be removed in any suitable manner such as by sawing or grinding, to form the casting as indicated in Fig. 8.

A modified form. of insert is shown in Figs. 13 and 14 wherein the truncated insert 28 is provided with the pin extensions 29 which may be removed. after the casting operation flush with the remainder of the boss portion of the casting 16.

In carrying out my invention the metal surrounding the insert is, of course, chilled by the metal mold on one side and by the metal of the insert on the other. The size of the insert for any given case is preferably made such that the metal surrounding the insert will chill and solidify at approximately the same rate as the metal constituting the remainder of the casting. The actual proportions of the insert will therefore vary to some extent, depending upon the actual size and mass of the insert, and the mass and thickness of section of the casting as a whole. In general, the smaller the mass of the insert the smaller the chilling effect thereof. Consequently, the smaller the heavy section of the casting is which is to be provided with an insert, the more closely the insert may approximate or approach the outer dimension of said heavy section, and consequently the thinner may be the section of metal which is to be cast around the insert. For an average case,

however, the thickness of the metal to be cast around the insert may be approximately the thickness of the adjacent thin section of the casting.

It will be readily understood that by my invention inserts may be utilized and heavy sections formed in castings in locations where in many cases it would not be feasible, and in cases indeed where it would be impossible, to locate feeding sprues to compensate for the heavy shrinkage involved in the casting of heavy casting sections adjacent to thin casting sections.

It will further be seen that I have provided by my invention a composite cast aluminum alloy casting of unitary exterior and possessing the advantages of solidity and homogeneity.

It will further be noted that by my invention aluminum castings of irregular and unusual shape readily may be made to form cast articles of solid and homogeneous. section and having a uniform exterior free from cracks, shrinks, and other imperfections frequently accompanying the casting of articles of irregular section.

It will further be noted that I have provided an advantageous method of solving the difficult problem of casting articles having sudden changes from thick to thin sections by forming a composite casting of an entirely unitary exterior.

Furthermore, it is to be understood that the particular forms of apparatus shown and described, and the particular procedure set forth, are presented for purposes of explanation and illustration and that various modifications of said apparatus and procedure can be made without departing from my invention as defined in the appended claims.

What I claim is:

1. As a new article of manufacture, an aluminum alloy permanent-mold casting of generally thin section having a thick section projecting from the thin section, said article having V a unitary homogeneous exterior of substantially uniform thickness and fine grain structure, and

a metal insert of substantially the same composition as the exterior of the casting embedded in the projection, said projection being substantially completely surrounded by the exterior unitary cast metal.

2. As a new article of manufacture, a composite permanent-mold cast article comprising a cast aluminum alloy insert and an exterior aluminum alloy portion cast around said insert to provide a thickened section, and extending beyond said insert to provide a thinner section, the thickness of the metal about said insert being of the same order as the thickness of the metal extending beyond the insert whereby to provide approximately uniform thickness having a homogeneous fine grain structure, the interior of said thick section comprising an insert closely surrounded by metal having the same composition and substantially the same thickness as the metal forming the exterior portion and rigidly engaged by the outer cast portion to form a rigid homogeneous cast article having an exterior of superior surface characteristics and metallurgical structure.

" i 4. As a new article of manufacture, an aluminum or aluminum alloy permanent-mold casting of generally thin section having a heavy section projecting therefrom, said article having a unitary exterior formed of aluminum or an aluminum alloy of substantially uniform thickness said insert being of similar metallurgical characteristics to that of the thin section, particularly as to grain size.

5. The method of casting articles having thin and thick sections from a metal having relatively high shrinkage characteristics, which comprises providing a permanent mold having a comparatively thin casting cavity of substantially uniform cross section and a recess communicating therewith, supporting an insert of substantially the same composition as the casting metal in said recess so as to provide a cavity surrounding said insert, and casting metal in the cavity having the thin cross section and in the cavity surrounding said insert to form an article having a relatively thin section and a relatively thick section.

6. The method of casting articles having thin and thick sections from aluminum or its alloys, which comprises providing a permanent mold having a comparatively thin casting cavity of substantially uniform cross section and a recess communicating therewith, supporting an insert of substantially the same composition as the casting metal in said recess so as to provide a cavity surrounding said insert, and casting metal in the cavity having the thin cross section and in the cavity surrounding said insert to form an article having a relatively thin section and a relatively thick section.

7. The method of casting articles having thin and thick sections from a metal having relatively high shrinkage characteristics, which comprises providing a permanent mold having a thin casting cavity of substantially uniform cross section and a recess communicating therewith, supporting an insert of substantially the same composition as the casting metal in said recess so as to define a casting cavity around said insert in which casting metal may be as effectively chilled as the metal in the thin casting cavity and casting metal in the thin cross section and causing it to flow in the recess surrounding said insert to form an article having a relatively thin section and a relatively thick section.

8. The method of casting articles having thin and thick sections from aluminum or aluminum alloys, which comprises providing a permanent mold having a thin casting cavity of substantially uniform cross section and a recess communicating therewith, supporting an insert of substantially the same composition as the casting metal in said recess in such a manner that the cavity surrounding the insert is of substantially the same cross section as the thin casting cavity, and casting metal in the thin casting cavity and around said insert to form an article of unitary exterior and non-uniform section.

9. The method of casting articles having thin and thick sections from aluminum or aluminum alloys, which comprises providing a permanent mold having a thin casting cavity of substantially uniform cross section and a recess communicating therewith, supporting an insert having substantially the same composition as the casting metal in said recess in spaced relationship to the walls thereof, said recess having substantially the same contour but being uniformly smaller than the thick section desired, and casting metal in the thin cavity and around the walls of said insert to form an article of unitary so as to provide a cavity surrounding said insert, and casting metal in the cavity having the thin cross section and in the cavity surrounding said insert to form an article having a relatively thin section and a relatively thick section.

EVERETT G. FAI-ILMAN.

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