US3852121A - Process for making a novel copper base alloy - Google Patents

Abstract

A method of preparing a copper alloy is disclosed which comprises providing in the alloy about 0.8 - 2.3% iron and about 0.3 - 1.7% cobalt, such that the amount of iron plus cobalt ranges from about 1.5 - 2.5%, from about 5 - 13% zinc, balance essentially copper. The alloy is hot rolled at a temperature of at least 500*C, and cold rolled by a process which includes conducting at least one interanneal between successive cold reductions. The interanneal is conducted at temperatures ranging from about 400 to 600*C for a period of at least 15 minutes. Processing may also include a final anneal at a temperature of from 350 to 600*C conducted for at least 15 minutes. The novel alloy of this invention possesses a combination of strength and electrical conductivity which makes it a suitable replacement for the C.D.A. 400 series tin-brass alloys.

Description

United States Patent [191 Crane et al.

[ 1 Dec. 3, 1974 1 PROCESS FOR MAKING A NOVEL COPPER BASE ALLOY [73] Assignee: Olin Corporation, New Haven,

Conn.

[22] Filed: Sept. 20, 1973 [21] Appl. No.: 399,073

Related U.S. Application Data [63] Continuation-impart of Ser. No. 268,485, July 3,

1972, Pat. N0. 3,816,109.

[52] U.S. Cl 148/2, 148/l1.5 R, 148/l2.7, 148/32, 148/32.5 [51] Int. Cl. C22f l/08 [58] Field of Search 148/2, 3, 11.5 R, 12.7, 148/32, 32.5, 13.2, 160; 75/153, 157.5

[56] References Cited UNlTED STATES PATENTS 1,723,922 8/1929 Corson 75 153 1,959,509 5/1934 Tour....... 75/l57.5 2,126,827 8/1938 Smith 148/ll.5 2,147,844 2/1939 Kelly 75/153 2,155,406 4/1939 Crampton 75/157.5 X

2,169,188 8/1939 Kelly 75/157.5 X 2,295,180 9/1942 Mitchell 75/l57.5

Primary ExaminerC. Lovell Attorney, Agent, or Firm-David A. Jackson; Robert H. Bachman 5 7] ABSTRACT A method of preparing a copper alloy is disclosed which comprises providing in the alloy about 0.8 2.3% iron and about 0.3 1.7% cobalt, such that the amount of iron plus cobalt ranges from about 1.5 2.5%, from about 5 13% zinc, balance essentially copper. The alloy is hot rolled at a temperature of at least 500C, and cold rolled by a process which includes conducting at least one interanneal between successive cold reductions. The interanneal is conducted at temperatures ranging from about 400 to 600C for a period of at least 15 minutes. Processing may also include a final anneal at a temperature of from 350 to 600C conducted for at least 15 minutes. The novel alloy of this invention possesses a combination of strength and electrical conductivity which makes it a suitable replacement for the C.D.A. 40,0 series tin-brass alloys.

8 Claims, 11Drawing Figure PATENIEDBEB 31914 I l I A 700 200 300 400 500 600 ROLLED ANA/EAL/A/G TEMPERATURE, c. (1 HOUR) PROCESS FOR MAKING A NOVEL COPPER BASE ALLOY CROSS REFERENCE TO RELATED APPLICATION The present application is a continuation-in-part of copending application Ser. No. 268,485, by Jacob Crane, Sam Friedman and Michael J. Pryor for COP- PER BASE ALLOY, filed July 3, 1972, now US. Pat. No. 3,816,109.

BACKGROUND OF THE INVENTION This invention provides for the methods of processing a copper base alloy disclosed in our co-pending application Ser. No. 268,485. The novel alloys disclosed therein were found to possess a unique combination of strength and electrical conductivity which makes them suitable for use in structural electrical components. The alloy possesses sufficient ductility to be formed into intricate parts such as electrical receptacles. Since such parts are used in a variety of environments and are in a highly stressed condition, stress corrosion is highly important.

Tin-brasses, namely, the C.D.A. 400 series alloys are commonly used for this type of application since they combine the above described properties. In general, the electrical conductivity of these 400 series alloys ranges from 28% IACS for C.D.A. Alloy 425 which is the strongest of the series, to 41% IACS for C.D.A. Alloy 405 which possesses the lowest strength of the series. Various of these alloys, particularly those containing higher tin concentrations, are difficult to manufacture, particularly with regard to casting and hot rollability.

SUMMARY OF THE INVENTION In accordance with this invention, a copper base alloy containing about 0.8 2.3% iron and about 0.3 1.7% cobalt wherein the amount of iron plus cobalt ranges from about 1.5 to 2.5%, from about 5 to 13% zinc, balance essentially copper, is prepared by a process which comprises hot rolling at a temperature of at least 500C, and cold rolling the alloy to a cross sectional area reduction of at least 50%, said cold rolling including one or more cold reduction steps followed by one or more interanneals conducted at a temperature of from 400 to 600C for at least 15 minutes.

The novel alloys processed in accordance with this invention provide electrical conductivity that is superior to those of the 400 series tin-brasses at a comparable strength to limiting bend radius ratio; or at comparable conductivity, they provide superior strength to limiting bend radius ratio.

Accordingly, it is a principal object of this invention to provide a method of processing a copper base alloy containing iron, cobalt and zinc within specific ranges which results in an alloy possessing an improved combination of strength and electrical conductivity.

It is a further object of this invention to provide a method as aforesaid which provides alloys with properties which make them suitable substitutes for the tinbrasses.

Other objects and advantages will become apparent to those skilled in the art from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWING The accompanying FIGURE is a graph of tensile strength (KS1) and electrical conductivity IACS) measured from alloy samples annealed at various temperatures for 1 hour.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with this invention, a method of processing a novel copper base alloy is disclosed which achieves a unique combination of strength and electrical conductivity in the alloy that is superior to the tinbrasses, and is less difficult to practice.

The method of this invention initially comprises providing a copper base alloy containing from about 0.8 to about 2.3% iron and from about 0.3 to about 1.7% cobalt such that the amount of iron plus cobalt ranges from about 1.5 to about 2.5%, from about 5 to about 13% zinc, balance essentially copper. Impurities may be present in amounts which do not adversely affect the properties of the above alloy.

Impurities at the following levels separately or in combination do not adversely affect the casting or hot and cold rolling characteristics of the alloy. Thus, the alloy may contain up to about 0.03% phosphorous, up to about 0.03% lead, up to about 0.05% tin, up to about 0.05% nickel, up toabout 0.10% manganese, up to about 0.10% aluminum, up to about 0.05% silver and up to about 0.10% silicon. It is preferred that the maximum total impurities be limited to less than 0.2% to minimize adverse affect on the properties of the alloys.

Melting and Casting: The copper is melted, the iron v and cobalt are added to the melt and it is then heated to about 1300C and held at that temperature until the iron and cobalt are thoroughly dissolved. The temperature of the melt is reduced to about 1200C and the zinc isthen added. The temperature at which the molten alloy is poured should be sufficiently high to assure a temperature no lower than about 1 C at the mold, in order to avoid the formation of coarse primary particles rich in iron and cobalt. Other casting parameters are in accordance with conventional practice in the art. The choice of casting method is not critical, as the alloy can be either static cast or direct chill (DC) cast.

Hot Rolling: The case alloy is soaked at a temperature of from about 800 to about 1000C and preferably from about 900 to about 950C. Soak time is not critical and may be varied as desired from a few minutes up to an hour or more. The pass schedule may, likewise, be set as desired. Pass speed is variable, as reduction can be achieved in a matter of minutes, or could be extended to hours duration depending upon the particular sequence employed by the artisan. Thus, for example, reduction of from Sinches to 0.40 inches would take of the order of minutes if done at one time, but could take hours if the alloy is permitted to cool off between passes. Pass temperature, however, should preferably be above about 500C but below the melting temperature of the alloy. It would be possible to permit the alloy to cool below 500C between passes, however, such practice is uneconomical as extensive reheating would be necessary. lt is, therefore, preferable to maintain the alloy at a temperature above 500C throughout the entire hot rolling step. The alloys of this invention have better than 75% cold rollability if the hot rolling operation is completed above 500C. Finishing temperatures of lower than 500C may be employed if some subsequent loss in cold rollability is acceptable.

Cold Rolling: The hot rolled alloy is then cold rolled. As previously noted, cold reductions in excess of 75% can be achieved if the hot rolling finishing temperature is above 500C. Cold rolling to any specified finished gage may require interannealing. After suitable annealing, the alloy still possesses cold rollability in excess of 75% reduction. Where the optimum combination of strength and formability of a temper rolled product is desired, a minimum of 50% reduction should be attained prior to the last interanneal. Thus, if only one interanneal is employed between two cold reductions, the alloy should be cold rolled to at least a 50% reduction in the first cold reduction, whereas if a series of cold reductions and interanneals are employed, only the cold reduction conducted prior to the last interanneal must achieve the required minimum of at least 50% reduction.

Annealing: Annealing for softening can be performed either by bell or strip annealing. The choice of bell annealing versus strip annealing is predicated upon desired electrical conductivity. Where maximum conductivity is required, bell annealing is preferred.

As noted earlier, for the purpose of obtaining improved strength in the cold worked condition, at least one interanneal is conducted between successive cold reductions. The interanneal should be carried out for a period of at least minutes at temperatures of from about 400 to about 600C. Preferably the interanneal is conducted at a temperature ranging from about 450 to about 550C for from about 1 to about 16 hours. It has been found that this latter schedule yields more favorable results when bell annealing is conducted. At least one interanneal is required to achieve a strength potential within the scope of this invention, however,

multiple interanneals can be used between cold reductions as desired. 1

\ It has been observed that the alloy prepared by this process possesses an unexpectedly improved strength and conductivity over alloys prepared by a process which employs only cold reduction. These findings are illustrated by the results of Example I which follows.

EXAMPLE I An alloy was prepared having the following composition (in weight percent): Cu 11.3% Zn 1.6% Fe 0.5% Co. The alloy was melted at 1300C and DC cast at 1 190C. The cast alloy was hot rolled from 5 inches thick to 0.40 inch thick at a starting temperature of 960C and a finishing temperature of 690C, and was then coil milled to 0.360 inch thick to produce a clean surface. The hot rolled plate was then processed variously as follows:

PROCESS A:

cold rolled 60% PROCESS 8:

cold rolled 77% PROCESS C:

TABLE I UTS Number of In- Process Final Reduction (KSl) Process Anneals A 60 83 None B '77 88 None C 50 .91 l D 6t 96 l E 50 90 2 F 98 2 Referring to the results of Table I, it is noted that the alloy prepared by Process D, in accordance with this invention, which involved 61% cold reduction and one interanneal, possessed an ultimate tensile strength of 96 KS1, whereas the same alloy prepared by Process A, which involved a 60% cold reduction but which omitted the interannealing step, possessed an ultimate tensile strength of only 83 KSI. Likewise, the alloy prepared by Process F which involved a 75% cold reduction and two interanneals, possessed an ultimate tensile strength of 98 KSI, whereas the same alloy prepared by Process B, which involved a 77% cold reduction with no interannealspossessed an ultimate tensile strength of 88 KS1. It is clear from this comparison that the employment of at least one interanneal provides a significant improvement in the tensile strength of the cold rolled alloys which cannot be duplicated simply by increased cold reduction only.

It has also been found that the bend properties of an alloy at a given strength level are affected by the interannealing parameters employed. Thus, variation of either one or both of the temperature and duration of the interanneal can result in alloys which have different minimum bend radii. This relationship is illustrated in Example ll, below.

EXAMPLE II Two alloys of composition (in weight percent) Cu [2.2% Zn 1.7% Fe 0.6% Co, and Cu l0.0% Zn 1.7% Fe 0.5% Co, respectively, were melted at l300C and Durville cast at 1175C. The alloys were hot rolled from 1 inches thick to approximately 0.35 inch thick at starting temperatures of about 950C and a finishing temperature of about 625C; surface milled to produce a clear surface; cold rolled to 0.080 inch gage; annealed at various temperatures for various times; cold rolled to 0.020 inch gage.

The tensile strength and minimum bend radius of the 0.020 inch gage metal measured with the bend axis parallel to the rolling direction (bad way bend), and 90 to the rolling direction good way bend) are shown in Table 11, below.

31% IACS. Thus, as shown in the FIGURE, the preparation of a finally annealed alloy possessing a particular combination of tensile strength and conductivity can be controlled by the careful selection of the final annealing temperature.

' Referring again to the FIGURE, the strength and conductivity of the as-rolled alloy were also measured For final gage annealing of cold metal, a range of about 350 to about 600C is desirable. The annealing temperature within this range may be varied depending upon the strength and electrical conductivity properties desired in the alloy. Thus, for maximum conductivity, annealing is preferably conducted in the range of about 350 to about 450C, whereas if major softening is desired, annealing in the range of about 400 to about 600C is preferred. Final gage annealing is normally conducted for at least minutes, and is preferably conducted for a period of from about I to about 8 hours. The employment of the final gage anneal in the above-described manner is illustrated in Example 111, below.

EXAMPLE 111 An alloy of composition Cu 1 1.9% Zn 1.5% Fe 0.5% Co was melted at 1300C and DC cast at 1 175C. The alloy was then hot rolled from 3 inches thick to approximately 0.40 inch thick at a starting temperature of 975C and a finishing temperature of about 400C. The

hot rolled alloy was then surface milled to product a clean surface; cold rolled to 0.080 inch gage; annealed at 500C for 1 hour; and cold rolled to 0.020 inch final gage. The samples thus prepared were then finally annealed at various temperatures for 1 hour.

The electrical conductivities and tensile strengths of the variously annealed samples were measured, and the resulting data is presented in the graph in the accompanying FIGURE, wherein electrical conductivity and tensile strength have been plotted as functions of annealing temperature.

Referring to the FIGURE, it can be seen that, in the range of 350 450C, an optimum combination of strength and conductivity is attained that results in alloys suited for a wide variety of electrical uses. Also, as stated earlier, temperatures of between 350 and 450C yield maximum conductivity, as conductivities of between about 35 to about 37% IACS are shown. Likewise, if further softening is desirable, temperatures ranging from 400 to 600C could be employed with only a minor loss of conductivity, i.e. levels of 33 to and plotted. The resulting data demonstrates that high tensile strength and acceptable conductivity are attainable by the employment of an interannealing step during the cold rolling of the alloy, in accordance with the process of this invention.

When cast in accordance with the methods of this invention, the copper alloy possesses a microstructure characterized by an average grain diameter in the order of 0.1 mm and an iron-cobalt rich phase with a particle size in the order of 0.01 mm, more or less uniformly V distributed throughout the copper matrix. The said particles tend to have angular boundaries, with the exception of some particles which may exhibit dendritic form with short dentrite arms.

The microstructure resulting from annealing the cold worked metal in the temperature range of about 450 to about 650C is characterized by fine, equiaxed grains which resist significant growth. The average recrystallized grain diameter remains less than 0.010 mm in diameter over the aforementioned temperature range. The approximate equiaxed iron-cobalt rich particles that exist in the cast structure, are elongated in the rolling direction, the extent of the elongation being dependent upon the total percent reduction of the main body of metal. x

The alloys prepared by the process of this invention have particular application in structural electrical components such as electrical contacts, electrical receptacles, electrical connectors and the like.

All of the compositions specified in this application by percentage are given in percentage by weight.

This invention may be employed in other forms or carried out in other ways without departing from the spirit or .essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What is claimed is:

l. A method of preparing copper alloys consisting essentially of about 0.82.3% iron and about 0.3-1.7%

cobalt, such that the amount of iron plus cobalt ranges from about l .5 to 2.5%, from to l3% zinc and the balance essentially copper, to provide improved strength, bend properties, and electrical properties which comprises:

a. hot rolling the alloy at a temperature of at least 500C. but below its melting temperature; and

b. cold rolling to at least 50% cold reduction wherein said cold rolling includes successive cold reductions and at least one interanneal conducted there between at temperatures ranging from about 400 to 600C for a period of at least minutes.

2. The method of claim 1 wherein the cold reduction conducted prior to the last interanneal yields a cross sectional area reduction of at least 50%.

3. The method of claim 1 wherein said interanneal is conducted at temperatures ranging from about 450 to 500C for from l to 4 hours 4. The method of claim 1 wherein said alloy is melted at a temperature of from about 1200 to l300C, and cast at a temperature such that the resultant mold temperature is at least 1 175C.

5. The method of claim I wherein, prior to hot rolling, the alloy is soaked at a temperature of from 800 to l000C for a period of up to 1 hour.

6. The method of claim 5 wherein said alloy is soaked at a temperature of from 900 to 950C.

7. The method of claim 1 wherein the cold rolled alloy is finally annealed at a temperature of 350 600C for at least 15 minutes.

8. The method of claim 7 wherein the final anneal is conducted at a temperature of from 350 to 450C for from 1 to 8 hours.

RUTH C. MASON "UNITED STATES PATENT OFFICE I CERTIFECATE OF CORRECTION Patent No. 3,852,121 Dated December 3, 197

Inventor(s) Jacob Crane, Sam Friedman and Michael J. Pryor It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Colume 8', corresponding to Claim 3, line 1, after "to", please delete the number "500C" and insert in its place 550C signed and sealed this 11th day of March- 1975.

(SEAL) Attest:

C. MARSHALL DANN Commissioner of Patents Attesting Officer and' Trademarks

Claims (8)

1. A METHOD OF PREPARING COPPER ALLOYS CONSISTIG ESSENTIALLY OF ABOUT 0.8-2.3% IRON AND ABOUT 0.3-1.7% COBALT, SUCH THAT THE AMOUNT OF IRON PLUS COBALT RANGES FROM ABOUT 1.5 TO 2.5%, FROM 5 TO 13% ZINC AND THE BALANCE ESSENTIALLY COPPER, TO PROVIDE IMPROVED STRENGTH, BEND PROPERTIES, AND ELECTRICAL PROPERTIES WHICH COMPRISES: A. HOT ROLLING THE ALLOY AT A TEMPERATURE OF AT LEAST 500*C, BUT BELOW ITS MELTING TEMPERATURE; AND B. COLD ROLLING TO AT LEAST 505 COLD REDUCTION WHEREIN SAID COLD ROLLING INCLUDES SUCCESSIVE COLD REDUCTIONS AND AT LEAST ONE INTERNNEAL CONDUCTED THEREBETWEEN AT TEMPERATURES RANGING FROM ABOUT 400 TO 600*C FOR A PERIOD OF AT LEAST 15 MINUTES.

2. The method of claim 1 wherein the cold reduction conducted prior to the last interanneal yields a cross sectional area reduction of at least 50%.

3. The method of claim 1 wherein said interanneal is conducted at temperatures ranging from about 450 to 500*C for from 1 to 4 hours.

4. The method of claim 1 wherein said alloy is melted at a temperature of from about 1200 to 1300*C, and cast at a temperature such that the resultant mold temperature is at least 1175*C.

5. The method of claim 1 wherein, prior to hot rolling, the alloy is soaked at a temperature of from 800 to 1000*C for a period of up to 1 hour.

6. The method of claim 5 wherein said alloy is soaked at a temperature of from 900 to 950*C.

7. The method of claim 1 wherein the cold rolled alloy is finally annealed at a temperature of 350 - 600*C for at least 15 minutes.

8. The method of claim 7 wherein the final anneal is conducted at a temperature of from 350 to 450*C for from 1 to 8 hours.

Images