US3369893A - Copper-zinc alloys - Google Patents

Description

United States Patet 3,369,913 Patented Feb. 20, 1968 fice 3,369,893 COPPER-ZINC ALLOYS William R. Opie, Keyport, N.J., and Jan A. Paces, New York, N.Y., assignors to American Metal Climax, Inc., New York, N.Y., a corporation of New York No Drawing. Filed Dec. 28, 1964, Ser. No. 421,668 6 Claims. (Cl. '75l57.5)

The present invention relates to alloys and, more particularly, to copper-zinc alloys in which copper is the predominant ingredient.

It is well known that copper-zinc alloys, commonly called brasses and under certain circumstances bronzes, are of considerable engineering and commercial importance and are widely employed in both cast and fabricated conditions. These alloys would of course assume even greater importance if their physical or mechanical properties and/or characteristics could be improved. For example, an increase in tensile strength would permit the use of such alloys in a much wider variety of structural applications. However, oftentimes an increase in tensile strength is accompanied by a decrease in another important property or characteristic, e.g., ductility, corrosion resistance, fabricability, impact strength, electrical or thermal conductivity, etc. Thus, the art has been faced with the difficult problem of increasing the tensile strength i of copper-zinc alloys without unduly or detrimentally decreasing another valuable property and/ or characteristic. The solution of this problem is rendered even more difficult by the usual requirement that the strengthened yet ductile alloy be economically producible.

Still other problems arise in connection with the economic production of high-strength copper-zinc alloys. One of these further problems is related to the metallurgical properties and characteristics of these copper-containing alloys. For example, wrought copper alloys including the copper-zinc alloys are often subjected to a stress-relieving or annealing heat treatment. After such a stress-relieving treatment, the tensile strengths of the copper-containing alloys usually fall off considerably and disadvantageously. Accordingly, what is needed is a copper-zinc alloy that retains much of its tensile strength even after stress-relieving or annealing.

Another problem concerns modernday technological demands for copper-zinc alloys having good high temperature properties and characteristics as well as the other aforementioned properties, characteristics and advantages. This problem is somewhat related to the problem of producing copper-zinc alloys having high tensile strengths in the stress-relieved condition. Consequently, those alloys having the higher strengths in the stressrelieved state are ordinarily the alloys having the better tensile strengths at high temperatures.

The art has attacked these myriad problems in a number of ways. For example, in order to obtain the higher strength copper-zinc alloys, the art has in many cases turned to the addition of alloying element or elements thereto. Such elements may retain their elemental identity or enter into solid solution or form special constituents depending upon the specific amounts present and the remaining ingredients of the alloy. How it is hardened may be important since the properties and characteristics, particularly at high temperature, may be dependent on the strengthening means. Consequently, the proper strengthening means presents a new problem.

Although many attempts were made to overcome the foregoing difficulties and other disadvantages, none, as far as we are aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that copper-Zinc alloys having high strength and other advantageous properties and/or characteristics together with ductility may now be economically produced.

It is an object of the present invention to provide new copper-zinc alloys having a unique combination of properties and/ or characteristics.

Another object of the present invention is to provide novel copper-zinc alloys which have beneficial properties and/ or characteristics in the stress-relieved condition.

The invention also contemplates providing new copperzinc alloys having excellent strength in the wrought condition.

It is a further object of the invention to provide novel copper-Zinc alloys that are readily fabricatable.

Still another object of the instant invention contemplates new copper-zinc alloys having high strength in combination with adequate ductility.

One of the other objects of this invention is to provide novel high-strength copper-zinc alloys having good thermal and electrical conductivity.

A further object of the invention contemplates the provision of copper-zinc alloys having a unique combination of ingredients in special proportions.

Among the further objects of the present invention is the provision of a special economic process for hardening copper-zinc alloys.

Other objects and advantages will become apparent from the following description:

Generally speaking, the present invention contemplates the production of unique copper-base alloys which have high strength and adequate ductility even when stressrelieved or annealed at temperatures as high as 350 C. or higher. The alloys of this invention contain, in weight percentages, about 0.05% to about 0.35%, e.g., about 0.1%, beryllium, about 0.08% to about 0.5%, e.g., about 0.2%, titanium, up to about 0.5% chromium, up to about 10% aluminum, e.g., about 7%, and from about 10% to about 45% zinc with the sum of the aluminum and zinc percentages lying between about 10% and 45%. The remaining ingredient of these alloys apart from incidental elements, including impurities and residual deoxidizers, is copper in amounts of at least about 54.5%. The alloys of this invention containing the aforemetnioned ingredients in the aforementioned proportioned amounts are characterized by a high recrystallization temperature, refined grain structure and resistance to grain growth at elevated temperatures, e.g., 300 C., 500 C. or even higher.

Another unique feature of the alloys within the scope of the present invention is that high strengths are obtained without any detrimental decrease in electrical and/ or thermal conductivity.

The alloys according to this invention contain copper, zinc, titanium and beryllium in specially controlled amounts and each of these elements in combination with each other element plays an important part in controlling the properties and/ or characteristics of the alloy. For example, the beryllium content is in the range of about 0.05% to about 0.35%, e.g., about 0.1%, and, advantageously, between about 0.05% and 0.085% by Weight of the alloy. The inclusion of beryllium in the amounts specified in the copper-zinc alloys of this invention aids in improving the tensile strength when appropriate amounts of titanium are copresent. Furthermore, the beryllium inclusion in combination with the remaining ingredients beneficially raises the recrystallization temperature and permits the alloy to be employed in high temperature applications. Thus, with the higher recrystallization temperature, by grain growth is retarded and the alloy remains stronger at the more elevated temperatures, e.g., 500 C., than when beryllium is not present. In addition to its other functions, the beryllium may act as a deoxidizer. When used as a deoxidizer, enough beryllium should be employed to assure that the copper-zinc alloy contain beryllium in the amounts hereinbefore set forth. However, if too much beryllium is used (more than about 0.35%), the ductility of the resulting alloy is very low and is quite diflicult to work. Furthermore, the inclusion of beryllium in amounts above 0.35% may be undesirable it cost is an important factor. For optimum strength and workability in combination with low cost, the maximum amount of beryllium is about 0.085%. It too little beryllium is used, e.g., less than about 0.05 the strengths of the copper-zinc alloys sufier.

It was found that titanium, when used in the amounts hereinbefore set forth in combination with the beryllium in the copper-zinc alloys of this invention, has an effect similar to that of beryllium. For example, the titanium (together with beryllium) aids in the strengthening or hardening of copper-zinc alloys. However, the combined use of beryllium and titanium yields an even stronger alloy than is expected. Like beryllium, if too much is used, e.g. more than about 0.5% by weight of the alloy, the ductility and fabricability detrimentally decreases and if too little is used, e.g. less than about 0.08% the strength detrimentally decreases. Also like beryllium, the titanium may have a deoxidizing effect when desired. In this situation, it is important that enough titanium be employed to insure that the copper-zinc alloy contains quantities of titanium within the range hereinbefore set forth. Titanium also has at least two other important functions. Firstly, titanium substantially inhibits zinc-fuming, i.e., the volatilization of zinc. Secondly, titanium apparently prevents the copper-zinc alloys containing beryllium from somewhat losing a portion of their strength at the more elevated temperatures, e.g., 300 C. Advantageously, the titanium content is between about 0.08% to about 0.12% by weight of the alloy for optimum properties and characteristics.

The zinc content should be kept within the specified range of from to 45% in order to provide the desired results. If the zinc content is too high, the ductility is appreciably and undesirably reduced. If the zinc content is below about 10%, the strength of the copper-zinc alloys of this invention are adversely affected. Part of the zinc may be replaced by aluminum when still higher strengths or greater oxidation resistance is desired. However, as is known, these higher strengths and oxidation resistance are achieved at the expense of castability, workability and conductivity. In this connection, the alloy may contain up to about 10% aluminum which replaces zinc in an amount equal to the amount of aluminum added. However, the alloys of this invention must always contain at least about 10% zinc and the sum of the aluminum and zinc percentages does not exceed about 45%. Advantageously, particularly where the soldering of the alloys is an important factor, the aluminum content is up to about 5% since aluminum, particularly in the higher end of the range, tends to form an oxide film which is detrimental during the fluxing phase of the soldering process.

The copper-zinc alloys of this invention containing controlled amounts of beryllium and titanium may include up to 0.5%, e.g., up to about 0.1%, chromium by weight of the alloy. Advantageously, the alloy does contain chromium in amounts of between 0.015% and 0.02% since chromium contributes to the strength of the alloy while l atfording some increase in the corrosion resistance of the alloys of this invention.

The alloys of this invention may also contain incidental elements such as up to about 0.5 silicon, up to about 1.5% iron, up to about 0.05% phosphorous, up to about 0.5% magnesium, up to about 1% tin, up to about 0.5 zirconium, up to about 2% manganese, up to about 0.5% lead, up to about 1% nickel and up to about 1% cobalt provided that the sum of such incidental elements is below about 3%, e.g. 1%. In this connection, when the alloys of this invention contain one or more of the aforementioned incidental elements, the amounts present are at the expense of the zinc content on a weight-per-weight basis. However, even when such element or elements are persent, the minimum zinc is still at least about 10% by weight of the alloy. Accordingly, the sum of zinc, aluminum and incidental ingredients is between about 10% and about Advantageously, the incidental elements are kept, below their solubility limits in the copper-zinc alloys of this invention. In particular, tin should be kept below about 1% by weight of the alloy since it has a tendency to form a phase having the appearance of the brittle delta phase of the copper-tin series. However, its inclusion in amounts of less than about 1% may afford some additional resistance to oxidation. Iron, while its inclusion may be desirable as a grain refiner, should be kept below about 1.5% since the iron-rich constituent is preferentially attacked in corrosive media. As is well known, lead is included to improve machinability but it seriously weakens the alloy and its inclusion in the alloys of this invention should be minimized. Nevertheless, the fact that the alloys of this invention can tolerate up to about 0.5% lead, e.g., up to about 0.25%, is a quite important practical advantage since it permits the use of scrap in melting the alloy. Manganese additions increase the amount of any iron present that may go into solution. In addition, it can be present in greater amounts, e.g., about 3% with the higher aluminum contents, e.g., from about 5% to about 10%, since it appears to extend the range of ductile copper-zinc alloys containing aluminum. The alloys of this invention may also tolerate up to about 0.1% lithium although care should be taken to see that the uppermost portion of the range is not exceeded since lithium adversely afiects workability and fabricability. Advantageously, each of the aforementioned incidental elements is kept below about 0.3% in order to achieve optimum properties and characteristics in the alloy and below about 0.1% where conductivity is an important factor.

In carrying the invention into practice, particularly unexpected results are obtained when the alloys contain, in weight percentages, about 0.05 to about 0.085% beryllium, about 0.08% to about 0.12% titanium, about 0.015% to about 0.02% chromium, up to about 5% aluminum, about 15% to about 40% zinc with the sum of the aluminum and zinc percentages being about 15% to about 40% and the balance, apart from incidental elements including magnesium, lead, tin, iron, zirconium, nickel and manganese in amounts up to about 1.5% in all, being copper in amounts of at least about 60%. Such alloys have a superior combination of physical, mechanical and/ or metallurgical properties and/ or characteristics. For example, the alloys have a transverse ultimate tensile strength (U.T.S.) of at least about 100,000 pounds per square inch (p.s.i.) in the 60% cold-worked condition and a transverse U.T.S. of at least about 50,000 p.s.i. after stress-relieving at about 450 C. for about one hour.

For the purpose of giving those skilled in the art a better understanding of the invention and a better appreciation of the advantages of the invention the following examples are set forth. In these examples, a series of castings having varying copper and zinc contents Were prepared. Charges of copper were melted and the otherv alloying constituents were added to the respective charges as master alloys, e.g., copper-titanium, copper-beryllium and copper-chromium. However, as those skilled in the art will readily appreciate, the alloying additions may be plunged into the melt in their element state. Finally, zinc was added to the melt and the alloys were cast into a graphite mold at 1050 C. The compositions of these that of the conventional brass subjected to identical treatment. In other words, the strength of the conventional brass Was more than doubled by additions of controlled amounts of beryllium and titanium. Furthermore, the conductivity of the higher strength copper-zinc alloys of alloys in weight percentages are set forth in Table I. 5 this invention is similar to that of the conventional 70:30

TABLE I brass. Alloy Copper Zinc Beryllium Titanium Chromium The alloys of the present invention, by virtue of their (percent) (percent) (percent) (percent) (percent) hrgh strength even after a relatively high-temperature 6M 30 M81 0 12 (L016 stress-relief, permit a greater use to be made of coppersas 40 0.03 0.11 0.019 zinc alloys in more severe structural applications, in- 58% i8 8:8? 8: cluding high temperature applications. In view of these I properties and/ or characteristics, the alloys of the present contamed M21 magnesmm (mental element) invention can be used in high pressure radiators and other The resulting slabs W re scalped, prehe d at about high strength applications necessitating the use of solder. 00 C- f r a t 30 minu s and h t W r o an In this connection, it is important to bear in mind that intermediate thickness of about 0.1". After stressrelievthe resistance to softening of the alloys during stressing of annealing at about fOf about one hour, relieving at elevated temperature permits the use of the alloys were Cold rolled in Spring hardnfiss, i. 60% cheaper and stronger solders over those previously used reduction (which contain too much tin) to join the copper-zinc Table II lists the results of mechanical testing after alloys to similar or dissimilar metals. Moreover, their use about 60% cold Work (spring hard) and after stressin electrical applications is not in any manner restricted relieving at various temperatures for various times in particularly when compared with the conventional 70:30 hours (hrs.). In addition, Table II includes testing to brass since the conductivity of the alloys of the present determine the conductivity in relation to the International 25 invention is similar to the aforementioned conventional Annealed Copper Standard (I.A.C.S.). brasses. Furthermore, the uses for the alloys is greatly TABLE II Transverse Transverse Hardness Conductivity Alloy Condition U.T Elongation (Rockwell (percent (p.s.i.) (percent) B) I.A.C.

A Spring Hard (311)...- 131,000 3 97 26 3400.,4hrs 129,000 1 100 26 SH+450 0., 1 hr 120, 000 5 93 27 SH+500 0., 1 hr 83, 000 20 80 27 SH+550 0., 1 hr. 74,000 25 73 27 SH 137,000 3 98 30.5 sH+340 0., 4 hrs. 92, 000 20 SH+450 0., 1 hr 34, 000 23 70 28 SH+550 0., 1 hr 76,000 30 28 SH 140,000 3 90 30 sH+340 0.,4hrs. 110,000 3 30 SH+450 0., 1 hr- 61,000 36 .93 31 SH+550 0., 1 hr 55, 000 44 31 D SH 107,000 2 84 30.5 D SH+450 0.,1hr 97, 500 5 79 34 By comparison, the corresponding properties obtained enhanced by virtue of their low cost in combination with a conventional 70:30 brass nominally containing, with their remarkably high strengths. This low cost is by Weight, about 70% copper, about 30% zinc and less directly attributable to the low amount of alloying inthan 0.05% incidental elements, including impurities, gredients necessary to attain high strengths. As a matter when subjected to the same treatment as applied to alloys of fact, high strengths can be obtained with alloying ad- A, B, C and D, are shown in Table III. ditions of about 0.13% consisting of about 0.05 beryl- TABLE In lium and about 0.08% titanium.

Although the present invention has been described in Trans- Trans- Hardness Conduoconjunction with preferred embodiments, it is to be undercondition qg f gfi gi 6mg stood that modifications and variations may be resorted (p.s.i.) tion I.A.C.S.) to without departing from the spirit and scope of the (Percent) invention, as those skilled in the art Will readily under- S H d 103 000 2 95 26 stand. For example, it is advantageous to use high-purity r g g a 601000 40 51 28 copper, e.g., oxygen-free copper, and high purity Zinc sr1+450 0., 1hr 50,000 44 28 particularly where high electrical conductivity is an important factor. Such modifications and variations are con- When stress-relieved at 550 C. for about one hour, the S}dered to be Wlthin 'f purview and Scope of t in conventional :30 brass was dead soft. 5 and appe nded clalms- By comparing alloy A with the conventional 70:30 What 15 c1a1med1:, brass of Table III, it is clear that the alloys of the in- An alloy conslstmg essentially of, y welght, about vention have much the superior tensile properties particu- 005% {lbout 035% berylhumr about (108% to about larly after stress-relieving thus indicating the high tem- 05% tltamflmr 1]P to about 05% Chromlum, P abOllt perature utility of the alloys of the present invention. 7 10% alummufn about 9 to about 45% zlnc Wlth 1116 AS a matter f f t alloy A (Within the scope f the sum of alummum and Zmc being about 10% to about invention and containing amounts of copper and zinc 45%, less than about 01% lithium and the balance, apart comparable with the amounts contained in the convenfrom incidfintzll elements, being pp in ts f a tional brass) exhibited over a higher transverse least about 54.5%. tensile strength after being stress-relieved at 450 C. over 7 2. An alloy consisting essential of, by weight about 7 0.05% to about 0.1% beryllium, about 0.08% to about 0.2% titanium, up to about 0.1% chromium, up to about 7% aluminum, about 10% to about 45% zinc with the sum of aluminum and Zinc being about 10% to about 45%, less than about 0.1% lithium and the balance essentially copper in amounts of at least about 54.5%.

3. An alloy consisting essentially of, by Weight, about 0.05% to about 0.085% beryllium, about 0.08% to about 0.12% titanium, up to about 0.1 chromium, up to about aluminum, about to about 45% zinc with the sum of the aluminum present and Zinc being about 10% to about 45%, less than about 0.1% lithium and the balance essentially copper in amounts of at least about 54.5%.

4. An alloy consisting essentially of, by weight, about 0.05% to about 0.085% beryllium, about 0.08% to about 0.12% titanium, about 0.015% to 0.02% chromium, up to about 5% aluminum, about to about zinc With the sum of the aluminum present and zinc being about 15% to about 40% and the balance, apart from incidental elements, being copper in amounts of at least about 60%.

5. A high'strength copper-zinc alloy having good conductivity consisting essentially of, by Weight, about 0.05

8 to about 0.35% eryllium, about 0.08% to about 0.5% titanium, up to about 0.5% chromium, about 10% to about zinc with the balance, apart from incidental elements in amounts of less than about 0.3%, being copper in amounts of at least about 54.5%.

6. A high-strength copper-zinc alloy having good conductivity consisting essentially of, by Weight, about 0.05% to about 0.085% beryllium, about 0.08% to about 0.12% titanium, up to about 0.1% chromium, about 15% 10 to about 40% Zinc with the balance, apart from incidental elements in amounts of less than about 0.1%, being copper in amounts of at least about References Cited FOREIGN PATENTS 683,122 11/1952 Great Britain. 954,288 4/ 1964 Great Britain.

96,603 6/ 1960 Norway.

CHARLES N. LOVELL, Primary Examiner.

Claims (1)

1. AN ALLOY CONSISTING ESSENTIALLY OF, BY WEIGHT, ABOUT 0.05% TO ABOUT 0.35% BERYLLIUM, ABOUT 0.08% TO ABOUT 0.5% TITANIUM, UP TO ABOUT 0.5% CHROMIUM, UP TO ABOUT 10% ALUMINUM, ABOUT 10% TO ABOUT 45% ZINC WITH THE SUM OF ALUMINUM AND ZINC BEING ABOUT 10% TO ABOUT 45% LESS THAN ABOUT 0.1% LITHIUM AND THE BALANCE, APART FROM INCIDENTAL ELEMENTS, BEING COPPER IN AMOUNTS OF AT LEAST ABOUT 54.5%.