Method of casting
US 3118225 A
Description (OCR text may contain errors)
Jan. 21, 1964 J. MCANDREWS 3,118,225
METHOD OF CASTING Filed March 14, 1960 III ///A L/Z 5 INVENTOR.
ILQMW ATTORNEY United States Patent 0 3,118,225 METHTBD 3F CASTING Anthony .l. McAnrlrews, Elmira, N.Y., assignor to General Twisters Corporation, Detroit, Mich a corporation of Delaware Filed Mar. 14, E63, Ser. No. 14,929 2 Claims. (1. 2 529) This invention relates to die casting and more particularly to a method of die casting tubular articles for use in conveying fluids from light metals such as aluminum and magnesium.
Die casting methods may be used to efficiently cast large quantities of articles from aluminum, magnesium, zinc and the like. Castings produced by typical die casting procedures inherently have dense and fluid-tight surface portions and porous internal portions. The dense surface layer is formed by reason of the cast metal contacting the relatively cool surface of the die metal.
In general tubular articles may be formed by conventional die casting techniques which involve suitably positioning a core in the die cast cavity and then die casting the body portion of the article about the core. If the tubular article to be die cast involves a relatively long passage of relatively small diameter, it may be impossible to provide a long, slender core which will withstand the force of the casting metal entering the die cavity at high pressure. Accordingly in the die casting of articles of this type, it is conventional practice to cast the article in solid form and subsequently to drill out the desired conduit passage. The latter method has serious shortcomings in that the solid die cast arti les, although having a relatively dense and fiuid-tight skin or surface which is formed adjacent the die cavity have a relatively porous central or core portion with the result that when the conduit is bored through the central portions of the article, a leaky conduit may result, particularly if it is necessary to machine away portions of the outer dense skin layer as is frequently the situation.
It is the object of this invention to provide a die cast, light metal tubular article which is characterized by having a dense, non-porous inner wall portion as well as a dense, non-porous outer wall portion. It is a further object of this invention to provide a method of die casting tubular articles of aluminum, magnesium and the like which have a dense, non-porous inner wall portion.
These and other objects of the invention are accomplished by first die casting an elongated chill of, for example, aluminum which has the general shape of the conduit to be subsequently formed. This chill, formed by a conventional die casting technique, has a surface which is relatively dense and interior portions which are relatively porous. The elongated chill is next positioned in a die cast cavity in a manner such that it occupies the space corresponding to the opening of the article to be cast. Next, the aluminum article is cast about the aforesaid aluminum chill positioned in the die cavity. In this casting operation the molten aluminum metal striking the aluminum chill forms a relatively dense surface adjacent the chill. The molten aluminum striking the die casting cavity surface similarly forms into a relatively dense, nonporous skin. Finally, after the casting is removed from the die cavity, the porous portion of the chill is removed by drilling with the result that the dense aluminum skin of the chill and the dense aluminum skin of the aluminum body cast thereagainst together form a relatively thick, dense conduit inner surface.
These and other objects or" the invention will appear from the following detailed description, reference being bad to the accompanying drawings in which:
FTGURE l is a die cast aluminum chill core;
FIGURE 2 is a fragmentary, cross-sectional View of die casting dies of a conventional type showing the chill core of FIGURE 1 positioned therein;
FIGURE 3 is the chill core of FIGURE 1 having the conduit body member cast thereabout; and
FIGURE 4 is a tubular conduit.
The present invention is concerned with the manufacture of tubular articles from light metals such as aluminum, magnesium, zinc or the like by die casting. The invention is further concerned with the manufacture of tubular articles of aluminum, magnesium, zinc and the like by die casting techniques of tubular articles which involve passages which are too thin to be formed by conventional casting techniques.
The invention will now be described in greater detail in terms of manufacturing an aluminum fuel oil line. First, an aluminum core member or chill 10 as shown in FIGURE 1 is die cast. This core member consists of a relatively slender, elongated portion 11, an angular projection 12 at one end thereof which is to be used as a core print or as a means for supporting the core within the die cavity and an enlarged portion 14 at the opposite end thereof having a recess 16 therein. As is inherent in light metal die cast articles, the external surface of the casting is chilled during the casting procedure as the molten metal strikes the die cavity surface with the result that a dense, relatively impermeable surface layer or skin of aluminum metal is formed.
The aluminum core 10 is positioned in the cavity 13 formed by the complementary die casting dies 26 and 22. These die members are of the usual type which are supported by die shoes which are adapted for reciprocating movement in a well known manner. The apparatus shown in FIGURE 2 is, of course, a fragmentary cross-sectional view of the die portions of a die cast ng apparatus. The core 10 is supported within the die cavity 18 by means of the projection 12 inserted in a recess 19 of the die member 12 and by means of a die pin 24 having its end positioned within the recess 16 of the core 16. Ejection pins (not shown) are provided in the die member 2% for removing the casting from the die cavity. The die member 22 is provided with a sprue opening 26 through which molten aluminum is delivered under pressure to the die cavity 18 in a well known manner.
After the core ll) has been positioned in the die cavity 18 as indicated above, the apparatus is operated whereby molten aluminum is delivered through the sprue 26 into the die cavity formed between the die members and the core Til to form the casting shown in FIGURE 3. This casting includes the core or chill portion 10 and the outer body portion 28 cast about the chill portion 10. The body member 23 as cast has an outer surface 39 as well as an inner surface 32 which have been cast against relatively cool metal surfaces or chills, the outer surface 39 being cast against the die cavity walls and the inner surface 32 being cast against the chill ill. The body member 23, therefore, has relatively dense, impermeable inner and outer surface layers 36 and 32. Since the outer surface 13 of the core 113 is also relatively dense and impermeable as described above, the surface layers 13 and 32 form, side by side, dense and impermeable inner layers of substantial thickness, The shrinkage of the casting 28 about the chill core it; provides an effective seal against any leakage which may result along the boundary between the chill core 1% and the casting 28 due to imperfections in either the dense layers 13 or 32 of the casting.
Finally, as shown in FIGURE 4, an opening 34 is drilled longitudinally through the core It) to form the finished fuel oil line. It is to be noted that the opening 34 is bored centrally of and entirely within the relatively porous central portions of the core 1% whereby the dense, impermeable inner layers Ii3 and 32 of the casting are not damaged. The outer surfaces of the casting may be machined or surface finished without impairing the fluidtight character of the conduit. The opening 34 is drilled through the casting so as to communciate With the depression 16 of the casting. The depression 16 is prefrably threaded or otherwise adapted for receiving another conduit member in fluid-tight relationship. Similarly, the opposite end 36 of the opening 34 is adapted for connection to another conduit or apparatus in connection with which it is to be used in a manner such that a fluidtight relationship is established with the inner core portion 32 of the casting.
The terms aluminum, magnesium and zinc as used herein intended, of course, to include various alloys of these metals useful in die casting procedures. The process of this invention may be beneficially used in die casting conduits or the like of any metal which tends to form porous articles in normal die casting.
While the present invention has been described by means of a specific embodiment, it will be understood that the scope of the invention is not to be limited thereby except as defined by the following claims.
1. A method of die casting a fluid-tight conduit of a light metal such as aluminum or the like which comprises the steps of die casting a core member having a dense substantially fluid-tight outer surface layer, then die casting a body member about said core member having a dense subi stantially fluid-tight outer surface layer, thereafter drilling a passage through said core member, said passage being confined substantially Within th surface layer of said core member, and forming connecting means at the of said passage.
2. A method of die casting a fluid-tight tubular member of aluminum which comprises the steps of die casting an elongated aluminum core having a dense substantially fluid-tight outer surface layer, then die casting an aluminum body member about said core member having a dense substantially fluid-fig; t outer surface layer and then drilling out the central portion oi said core interiorly oi the dense outer layer thereof.
References (fitted in the file of this patent UNITED STATES FATENTS