US3508916A - Cu base die casting alloy - Google Patents

Description

United States Patent 3,508,916 Cu BASE DIE CASTING ALLOY George S. Foerster, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 622,456, Mar. 13, 1967. This application July 9, 1969, Ser. No. 840,537

Int. Cl. C22c 9/ 00, 9/04 U.S. Cl. 75-1575 8 Claims ABSTRACT OF THE DISCLOSURE A copper base die casting alloy containing, by weight, about 5 to 25 percent of antimony and about 1 to percent of magnesium is improved, e.g., making it more ductile and lower in cost, upon partial substitution of zinc or manganese or a mixture thereof for the antimony and magnesium content.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of copending application, Ser. No. 622,456, filed Mar. 13, 1967, now abandoned, which was copending with application Ser. No. 422,363, filed Dec. 30, 1964, now U.S. Patent No. 3,318,693.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to copper base die casting alloys, particularly such alloys containing additions of antimony and magnesium.

Description of the prior art Conventional copper base die casting alloys normally have a liquidus temperature above, for example, about 1600 F. or higher. They are, therefore, ditficult to die cast in that they cause considerable wear on the die. Known copper base alloys which, on the other hand, melt at lower temperatures are too brittle for practical use in die casting. For example, the copper base alloy containing 9.7 weight percent of magnesium melts at 1332 F. (722 C.) While the copper base alloy containing 31 weight percent of antimony melts at 1193 F. (645 C.); both alloys, however, are very brittle, that is, they have little, if any, ductility.

In copending application Ser. No. 422,363, filed Dec. 30, 1964, now U.S. Patent No. 3,318,693, a novel low melting, ductile, ternary, copper base die casting alloy is disclosed and claimed comprising from. about 5 to about weight percent antimony (Sb) and from about 1 to about 10 percent magnesium (Mg), the balance being substantially copper. The preferred ternary alloys described in said application contain large amounts of the alloying constituents such as to percent antimony and 6 to 7.5 percent magnesium. While this ternary alloy provides a ductile, low melting, die casting alloy, it is not as economical as would be desirable and in addition, melts thereof tend to oxidize to some extent if not protected.

OBJECTS OF THE INVENTION A leading object of the present invention, therefore, is to provide a novel, improved, ductile, low melting, economical copper base alloy composed of lower cost materials.

Aonther object of the invention is to provide a novel, improved, ductile, low melting copper base alloy having a reduced tendency to oxidize as a melt and which is particularly suitable for use in die casting operations.

3,508,916 Patented Apr. 28, 1970 SUMMARY OF THE INVENTION The alloy of the present invention constitutes an improvement over the above described copper base ternary alloy containing antimony and magnesium in that relatively low cost manganese and/or zinc is added thereto which permits a significant decrease in the amounts of the antimony and magnesium constituents, thereby avoiding the heretofore described oxidation problems while yet maintaining substantially the same low melting temperature range. Furthermore, particularly in the preferred embodiment alloys of the invention, a substantial increase in ductility is obtained as compared to preferred alloys in the ternary composition aforesaid. There is thus provided a more economical, low melting, ductile, copper base alloy having a degree of utility in die casting heretofore unknown, and moreover, not available in conven tional copper base die casting alloys.

The present improved copper base die casting alloy broadly comprises by Weight from about 2 to about 20 percent antimony, from about 0.5 to about 8 percent magnesium, and an alloying addition selected from thegroup consisting of zinc, manganese and mixtures thereof, said zinc and manganese when used singularly in an amount of from about 1 to about 40 percent and more preferably 10 to about 35 percent, and when used together being in total a combined amount of about 1 to about 50 percent, and more preferably 15 to 45 percent, the balance copper, said copper being present in an amount greater than any other single alloying constituent in the alloy. When Zinc and manganese are used together in a total amount of about 15 to 45 percent, preferably the amount of zinc used in the range of 5 to 30 percent of the alloy and the amount of manganese is in the range of 10 to 35 percent.

DETAILED DESCRIPTION OF THE INVENTION Most preferably, the improved alloy Will contain from about 25 to about 35 weight percent of zinc, or, alternatively of manganese, whereas, if zinc and manganese are employed together, from about 10 to about 25 percent zinc with from about 15 to about 30 percent manganese, the combined total of manganese and zinc in any case being Within a range of from about 30 to about 45 percent, the balance being essentially and predominantly copper.

Alloy compositions within the present invention will in any even contain copper in an amount greater than any other single alloying constituent.

While the alloy containing about 1 percent of zinc or manganese or a combination thereof exhibits some improvement in properties according to the invention, the advantage gained by the addition of zinc and/or manganese is more substantial if an addition is made to the alloy amounting to at least 5 percent of zinc or manganese or a combination thereof. Broadly speaking the combination may contain a trace or more of the one metal, and the balance the other.

Normally, when the zinc and manganese combined concentration in the present alloy is greater than about 30 percent, the total combined concentration of antimony plus magnesium should not exceed about 15 percent. For example, in an alloy in accordance with the present invention containing 20 percent Mn and 15 percent Zn, the antimony content may be about 10 percent and about 3 percent for magnesium, the balance being predominantly copper.

A magnesium-to-antimony weight ratio of from about 0.3 to about 0.35 should be observed in the preferred alloys of the invention when the antimony concentration therein exceeds approximately 15 percent, whereas, when the antimony concentration ranges from about 10 to about 15 percent a more liberal Mg/Sb ratio of 0.2 to 0.4 may 3 be' employed. At antimony concentrations below about 10 percent, a Mg/ Sb ratio of from 0.1 to 0.6.is employed.

The very optimum alloys of the invention will normally contain, e.g., from about 2 to about 6 percent magcontraction was determined by compressing the 1 inch sections aforesaid to failure (to cracking or rupture)-then measuring the height again and calculating the percent of compression or deformation from the original 1 inch nesium, from about 5 to about 18 percent antimony, from 5 length.

- TABLE 1 I Alloy composition 1,000 p.s.i.

Percent Percent Percent Percent Melting Percent Example Mg Sb Zn 11 Other Range, F. O CYS CS Balance commercially pure copper.

about 25 to about 35 percent of either zinc or manganese, or, when employed together, from about 10 to about 25 percent zinc and 15 to 30 percent manganese, the total of zinc plus manganese employed being preferably within a range of from about 30 to about 45 percent.

The ductility of the improved alloys of the present invention is suprising in that it is generally thought in the metallurgical art that by increasing the alloying constituents the brittleness of the alloy is also increased. Such is not the case in the present invention. Moreover, when copper is alloyed with more than about 3 percent Mg or with more than 10 percent Sb, the alloys become brittle and of little practical use, whereas, when copper is alloyed with both Mg and Sb in the proper ratio, substantially larger additions may be employed together with manganese and/or zinc without embrittling the alloys.

From the data in Table I, the percent compression of the alloys shown therein indicates their ductility which together with their low melting point ranges, indicates 20 their satisfactory use in die casting as copper base alloys 30 of alloys. The metallographic structure of each was examined and characterized and listed in the following Table II along with the compositions and freezing ranges.

TABLE 11 Alloy Composition Freezing Percent Mg Percent Sb Percent Zn range, F. Metallcgraphic structure 4. l3. 5 1, 540%, 460 Hypoeutectie ca. 1 0t. 3. 9 1a 15 1, 500 Eutectic.

3 9 1, 570-1, 500 Hypoeutectic, ca. a. 4 12 20 1, 470-1, 460 Hypoeutectic, slightly. 3.75 11 25 1,5101,500 Hypereutectic, slightly. 2. 7 7 1, 510-1, 500 Hypoeutectic, slightly. c a i cmnnn 6 18 1, 410-1, 380 Hypoeutectie, ca. 14a.

* Balance commercially pure copper.

The alloys of this invention may all be generally characterized as primarily melting below a temperature of approximately 1500 F., that is, well below the melting point of conventional copper base die casting alloys.

In preparing the alloys herein, conventional melting and alloying techniques may be employed. A particularly good technique is to melt the copper base constituent in a crucible of an induction unit, the zinc being melted therewith as Muntz metal (copper base plus percent Zn), with the manganese added as the metal, whereupon the antimony and then the magnesium are added to the melt. The antimony may also be melted with the copper base metal if desired.

The following examples are provided to further illustrate the present invention but are not to be construed as limiting it thereto.

A number of alloys were prepared in accordance with the present invention by first melting down the copper base metal, zinc (added as Muntz metal which is copper containing about 40 percent Zn) and the manganese constituents in an induction furnace. The antimony and mag nesium constituents were then added to the molten charge Each melt was separated into two parts, one part being molded into a inch cylinder in a graphite mold while the other part was poured into another crucible, whereupon, a thermocouple was inserted below the melt surface at the center of the melt and its cooling curve automatically plotted to determine the freezing range.

A sample about 1 inch long was cut from the center of the cylinder and tested in compression to determine compressive yield strength using a 0.2 percent offset (CYS), ultimate compressive strength (CS) and ductility by calculating percent contraction percent C.). Percent The alloy containing additions of manganese instead of zinc exhibits substantially the properties listed in Table II when similar amounts of manganese are used.

Very minor amounts of other alloying additions not affecting the basic characteristics of the present alloy may be added thereto, such amounts not exceeding about 1 percent per element added nor about 2 to 3 percent combined total if more than one element is added, apart from impurities present at normal levels for commercially pure metals and metalloids. Examples of other elements which may be added in a minor amount include silicon, beryllium, aluminum, tin, lead, iron, nickel, cobalt and titanium.

What is claimed is:

1. A low melting, ductile, copper base die casting allo consisting essentially of, by weight, from about 2 to about 20 percent antimony, from about 0.5 to about 8 percent of magnesium, and an alloying addition selected from the group consisting of zinc, manganese and mixtures thereof, said zinc and manganese when used singularly being present in an amount of from about 1 to about 40 percent, and when present together being in total a combined amount of about 1 to about 50 percent, the balance copper, said copper being present in an amount greater than any other single alloying constituent in the alloy.

2. The die casting alloy of claim 1 wherein the zinc and manganese when used singularly are present in the alloy in an amount of from about 10 to about 35 percent, and when used together are present in a'total combined amount of from about 15 to about 45 percent, the zinc content being about 5 to 30 percent of the alloy and the manganese content being about 5 to 35 percent of the alloy, the balance being essentially and predominantly copper.

3. The die casting alloy of claim 1 wherein from about to about percent zinc and from about 15 to about percent of manganese are present in the alloy when containing both zinc and manganese.

4. The die casting allow of claim 1 wherein the zinc and manganese when used singularly are present in the alloy in an amount of from about 25 to about percent, and when used together are present in a total combined amount of from about 30 to about percent, the zinc content being about 10 to 25 percent of the alloy and the manganese content being about 15 to 30 percent of the alloy, the balance being essentially and predominantly copper.

5. The die casting alloy of claim 1 wherein the magnesium and antimony constituents are in a ratio of from about 0.3 to 0.35 when the total concentration of antimony in the alloy is within a range of from about 15 percent to about 20 percent.

6. The die casting alloy of claim 1 wherein the magnesium and antimony constituents are in a ratio of from about 0.2 to 0.4 when the total antimony concentration is within a range of from about 10 to about 15 percent.

7. The die casting alloy of claim 1 wherein the magnesium and antimony constituents are in a ratio of from about 0.1 to about 0.6 when the total antimony concentration is within a range of from about 2 to about 10 percent.

8. The die casting alloy of claim 1 wherein the total amount of magnesium and antimony does not exceed about 15 percent.

References Cited UNITED STATES PATENTS CHARLES N. LOVELL, Primary Examiner US. Cl. X.R. 153, 161