CN1255167A - Grain refined tin brass - Google Patents

Abstract

There is provided a tin brass alloy having a grain structure that is refined by the addition of controlled amounts of both zinc and iron. Other metallic elements that undergo peritectic decomposition in a tin brass alloy, such as cobalt, iridium, niobium, vanadium and molybdenum may substitute for from a portion to all of the iron. Direct chill cast alloys containing from 1% to 4%, by weight of tin, from 0.8% to 4% of iron, from an amount effective to enhance iron initiated grain refinement to 20% of zinc and the remainder copper and inevitable impurities are readily hot worked. The zinc addition further increases the strength of the alloy and improves the bend formability in the ''good way'', perpendicular to the longitudinal axis of a rolled strip.

Description

Grain refined tin brass

The present invention relates to a copper alloy having high strength, good formability and higher electrical conductivity. And more particularly to grain refinement of tin brass by controlling the amount of iron, cobalt, or other elements added to initiate the peritectic reaction during solidification.

Throughout this application, all percentages are by weight unless otherwise indicated.

Industrial tin brass is a copper alloy comprising: 0.35 to 4 percent of tin, 0.35 percent of phosphorus at most, 49 to 96 percent of copper and the balance of zinc. The alloy is designated by the Copper Development Association (CDA) as Copper alloy C40400-C49080.

One industrial tin brass is C42500 copper alloy. The alloy comprises the following components: 87 to 90 percent of copper, 1.5 to 3.0 percent of tin, 0.05 percent of iron at most, 0.35 percent of phosphorus at most and the balance of zinc. Products produced from the alloy include electrical switch springs, electrodes, wire connectors, fuse clips, pen clips, weather strips, and the like.

The American society of metals Handbook (ASM Handbook) specifies a nominal conductivity for the C42500 copper alloy of 28% IACS (International Annealed copper Standard specifies a conductivity of 100% IACS for "pure" copper at 20 ℃) and a yield strength of 45 to 92ksi depending on tempering. The alloy is suitable for many circuit wiring applications, but its yield strength is below desired.

It is known that the yield strength of certain copper alloys can be increased by controlling the amount of iron added. For example, European patent office publication No. EP0769563A1, published on 4/23 1997, entitled "iron-modified phosphor bronze", discloses the addition of 1.65% to 4.0% iron to phosphor bronze. The conductivity of the alloy exceeds 30% IACS and the ultimate tensile strength exceeds 95 ksi.

Japanese patent application No. 57-68061 of Furukawa metals industries limited discloses a copper alloy containing 0.5% to 3.0% of zinc, tin and iron, respectively. Iron is disclosed to improve the strength and heat resistance of the alloy.

Although the benefits of adding iron to phosphor bronze are known, iron presents problems with the alloy. The conductivity of the alloy decreases. The formation of hair lines affects its processing. When the iron content of the alloy exceeds a critical value, hairlines are formed. This critical iron content depends on the composition of the alloy. Hairlines form and expand during mechanical deformation when pre-peritectic iron particles are precipitated from a liquid before solidification. Hairlines are detrimental because they affect the appearance of the alloy and reduce formability.

In high copper tin brass (over 85% Cu), iron is an impurity, the maximum allowable content of which is typically 0.05%. This is because iron can reduce conductivity and the resulting hair line can reduce bending characteristics.

Other metal additives of the alloy that can initiate the formation of peritectic phases during solidification can be substituted for iron, either completely or partially. One specific additive is cobalt, and other suitable additives include vanadium, niobium, iridium, and molybdenum.

Therefore, there remains a need for an iron-modified tin brass alloy that does not suffer from the aforementioned disadvantages of reduced conductivity and hair line formation.

It is therefore an object of the present invention to provide a tin brass alloy with improved strength. It is a feature of the present invention that the strength is increased by controlling the amount of the mixture of iron and zinc added. It is another feature of the present invention that the alloy is processed according to given processing steps in which the fine microstructure is maintained in the wrought alloy.

Advantages of the alloy of the present invention include increased yield strength without a decrease in electrical conductivity. The grain size of the refined cast alloy is less than 100 mu m, and when the grain size of the forged alloy is about 5-20 mu m, the microstructure is fine-grained. In addition, another advantage of the alloy is that its electrical conductivity is substantially equal to that of the C42500 copper alloy, while the yield strength is significantly improved.

According to the present invention, a copper alloy is provided. The alloy comprises the following basic components: 1-4% by weight of tin, 0.8-4.0% by weight of iron, the content of zinc ranging from a content effective to promote iron to initiate grain refinement to 20% by weight, up to 0.4% by weight of phosphorus, the remainder being copper and unavoidable impurities. The grain refining alloy has an average grain size of less than 100 μm and an average grain size after machining of about 5 to 20 μm.

The above objects, features and advantages will become more apparent from the following description and the accompanying drawings.

FIG. 1 is a flow chart of a method of processing an alloy of the present invention.

The effect of iron content on yield strength is given by the curve of figure 2.

The effect of iron content on the ultimate tensile strength is given by the curve of figure 3.

The effect of tin content on yield strength is given by the curve of fig. 4.

The effect of tin content on ultimate tensile strength is given by the curve of fig. 5.

The effect of zinc content on yield strength is given by the curve of figure 6.

The effect of zinc content on ultimate tensile strength is given by the curve of figure 7.

The copper alloy of the present invention is iron modified tin brass. The alloy comprises the following basic components: 1 to 4 percent of tin, 0.8 to 4.0 percent of iron, 5 to 20 percent of zinc, 0.4 percent of phosphorus at most, and the balance of copper and inevitable impurities. The average grain size of the as-cast grain refined alloy is less than 100 μm.

When the alloy is cast by direct chill casting, preferred embodiments include: 1.5 to 2.5 percent of tin and 1.6 to 2.2 percent of iron. The critical minimum value of iron content to obtain the as-cast grain refining effect was found to be 1.6%. The most preferred iron content is 1.6% to 1.8 iron.

Tin (Sn)

Tin may increase the strength of the alloys of the present invention and may increase their resistance to stress relaxation.

The stress relaxation resistance is described by ASTM (American Society for Testing and materials) as: in the cantilever condition, the panel specimens were pre-stressed to a percent residual stress of 80% of yield strength. The panels were heated to 125℃ for a given time and the test was repeated periodically. The time to measure this property at 125 ℃ is up to 3000 hours. The higher the residual stress, the better the usability of a given composition in terms of springs.

However, the increase in strength and resistance to stress relaxation is offset by the decrease in conductivity, as shown in table 1. Further, tin makes alloy processing, especially hot processing, more difficult. When the tin content exceeds 2.5%, the processing cost of the alloy may be too high for certain industrial uses. With tin contents below 1.5%, the alloy does not have sufficient strength and resistance to stress relaxation for spring applications.

TABLE 1

Composition of	Conductivity (% IACS)	Yield strength (ksi) (MPa)
			88.5％Cu 9.5％Zn 2％Sn 0.2％P	26	75 517
87.6％Cu 9.5％Zn 2.9％Sn 0.2％P	21	83 572
			94.8％Cu 5％Sn 0.2％P	17	102 703

The preferred tin content of the alloys of the present invention is from about 1.2% to about 2.2%, with a tin content of from about 1.4% to about 1.9% being most preferred.

Iron

Iron can refine the as-cast alloy microstructure and improve strength. The refined microstructure is characterized by an average grain size of less than 100 μm. The average grain size is preferably 30 to 90 μm, and the most preferred average grain size is 40 to 70 μm. This refined microstructure facilitates mechanical deformation at elevated temperatures, such as rolling at 850 ℃.

When the iron content is less than about 1.6%, the grain refining effect is reduced and coarse grains having an average grain size of the order of 600 to 2000 μm are formed. When the iron content exceeds 2.2%, very much hairlines are generated in the hot working.

The effective range of iron is 1.6% to 2.2%, unlike the range of iron in the alloy disclosed in EP0769563a1, which considers that grain refining is not optimal until the iron content exceeds about 2%. The ability to refine the grain structure at lower iron levels in the alloyof the invention is unexpected and is believed to be due to the shift in phase equilibrium caused by the introduction of zinc. In order for this phase shift to be effective, a minimum zinc content of about 5% is required.

When the iron content exceeds about 2.2%, large hairlines exceeding about 200 μm in length are generated. Large hairlines affect not only the appearance of the alloy surface, but also the surface characteristics, electrical properties and chemical properties. The large hairline can change the weldability and electroplatability of the alloy.

In order to maximize the grain refining and strength enhancing effects of iron without the formation of detrimental hair streaks, the iron content should be maintained at about 1.6% to 2.2%, with a preferred iron content of about 1.6% to 1.8%.

Zinc

The addition of zinc to the alloys of the present invention is desirable to provide a moderate increase in strength while reducing some of the conductivity. However, as shown in table 2, it was unexpected that the grain refining ability of the iron additive was significantly enhanced when the minimum amount of zinc was 5%, as shown in table 3.

TABLE 2

Composition of	Conductivity (% IACS)	Tensile Strength (MPa) (ksi) (MPa)
			1.8Sn 2.2Fe The balance being Cu	33	99 683
1.8Sn 2.2Fe 5Zn The balance being Cu	29	99 683
			1.8Sn 2.2Fe 10Zn The balance being Cu	25	108 683

(tensile Strength measured after the reduction of Cold Rolling reached 70%)

TABLE 3

Composition of	Grain size
		1.9Fe 1.8Sn 0.04P The balance being Cu	Coarse
5Zn 1.9Fe 1.8Sn 0.04P The balance being Cu	Medium and high grade
		7.5Zn 1.9Fe 1.8Sn 0.04P The balance being Cu	Thin and thin
10Zn 1.9Fe 1.8Sn 0.04P The balance being Cu	Thin and thin
		15Zn 3.3Co 1.8Sn 0.04P The balance being Cu	Thin and thin

The preferred zinc content is from a level effective to promote grain refinement of the iron to about 20%, more preferably from about 5% to about 15%, most preferably from about 8% to about 12%.

Peritectic reaction of as-cast grain refinement

It is believed that the grain refining effect of the iron additive is due to the fact that during solidification iron is first separated from the melt as a large number of relatively fine dendritic face-centered cubic gamma iron particles. As cooling continues, these first-peritectic iron particles effectively become the core of the alloy's as-cast grains through peritectic solidification reactions:

effectively improve the nucleation rate and also lead to the refinement of the as-cast crystal grains.

For other metallic elements, such as those which can produce similar peritectic decomposition reactions in tin brass by their elementary primary peritectic particles or intermetallic primary peritectic particles, a prerequisite is attached: the peritectic component does not require such a large amount of additives that the desired properties of the tin brass, such as processability, conductivity or bending formability, are greatly reduced. Cobalt may suitably replace iron wholly or partly. As shown in table 4.

TABLE 4

Composition of	Grain size
		10Zn 2.7Co 1.8Sn 0.04P The balance being Cu	Coarse
10Zn 3.0Co 1.8Sn 0.04P The balance being Cu	Coarse
		10Zn 3.3Co 1.8Sn 0.04P The balance being Cu	Thin and thin

As can be seen from Table 4, the cobalt content should exceed about 3.0% when used as a primary grain refiner. The preferred cobalt content is about 3.2% to 4.4%, with the most preferred cobalt content being 3.2% to 3.6%. Excessive cobalt content should be avoided because of the rough hairline that may result in excessive peritectic cobalt particles and may degrade alloy properties.

The addition of cobalt may partially replace the iron. The effect of cobalt refining the grain structure of the alloy of the invention is slightly poor, and the substitution should satisfy the equation:

fe + MCo-the range of iron givenabove

M is 0.45 to 0.65, preferably 0.5 to 0.6. Most preferably in the higher range, for lower cobalt contents, M is about 0.6; for higher cobalt contents, M is about 0.5; the approximate range between the lower and higher levels of cobalt is 2%.

Other suitable peritectic particle-forming elements include: iridium in an amount of about 10% to 20%, preferably about 11% to 15%; niobium in an amount of about 0.01% to about 5%, preferably about 0.1% to about 1%; vanadium in an amount of about 0.01% to about 5%, preferably about 0.1% to about 1%; the molybdenum content is about 0.5% to about 5%, preferably about 1% to about 3%.

One or more of these other peritectic reaction initiators may completely or partially replace cobalt or iron.

Other additives

Phosphorus is added to the alloy for conventional reasons to prevent the formation of copper oxide and tin oxide precipitates and to promote the formation of iron phosphide. Phosphorus causes problems in the processing of alloys, particularly hot rolling. It is believed that the iron additive can counteract the detrimental effects of phosphorus. At least a minimum amount of iron must be used to counteract the effect of phosphorus.

Suitable phosphorus levels are any amount not greater than about 0.4%, preferably from about 0.03% to about 0.3%.

When the copper alloy solidifies, the total amount of other elements in solution can be up to 20%, and zinc can be partially or completely replaced in an atomic ratio of 1: 1. Those ranges specifically for zinc are preferred ranges for the content of these solid soluble elements. Among these preferred elements are manganese and aluminum.

Less preferred elemental additives are those that affect the properties of the alloy. Although less preferred, such elements alsoinclude additives such as nickel, magnesium, beryllium, silicon, zirconium, titanium, chromium, and mixtures thereof.

For example, nickel additives can drastically reduce conductivity. Thus, the less preferred additive is preferably present in an amount less than about 0.4%, and most preferably in an amount less than about 0.2%. The sum of all these less preferred alloying additions is most preferably present in an amount of less than about 0.5%.

Process of manufacture

The alloy of the present invention is preferably processed according to the flow diagram of fig. 1. The ingot is cast 10 by conventional means such as direct chill casting, the ingot being an alloy of the composition described herein. The 12 alloy is hot rolled at a temperature in the range of about 650 c to 950 c, preferably about 825 c to 875 c. The alloy is optionally heated 14 to maintain the desired hot rolling 12 temperature.

The hot rolling reduction by thickness is typically no more than 98%, preferably about 80% to 95%. The hot rolling process may be one pass or multiple passes as long as the ingot temperature is maintained above 650 ℃.

After hot rolling 12, the alloy may optionally be water quenched 16. The strip is then mechanically rolled to remove surface oxides. And then cold rolling 18 is carried out, the reduction is calculated according to the thickness from the size after the hot rolling step 12 is finished, the cold rolling reduction is at least 60%, and the cold rolling can be single-pass or multi-pass. The preferred reduction for cold rolling 18 is about 60% to about 90%.

The strip is then annealed at a temperature of about 400 c to about 600 c for about 0.5 to about 8 hours to recrystallize the alloy. Preferably, the temperature of the first recrystallization annealing is about 500 ℃ to 600 ℃ and the annealing time is 3 to 5 hours. These times are for example for a hood-type annealing in an inert atmosphere of nitrogen or in a reducing atmosphere of a mixture of hydrogen and nitrogen.

The strip may also be strip annealed, for example, at a temperature of about 600 ℃ to 950 ℃ for 0.5 to 10 minutes.

The primary recrystallization anneal 20 produces precipitates of iron and iron phosphide. During this and subsequent annealing, these precipitates control the grain size, they increase the strength of the alloy by dispersion strengthening, and they improve the electrical conductivity by desolventizing iron from solid solution from the copper matrix.

The strip is then subjected to a secondary cold rolling 22 to a reduction in thickness of about 30% to 70%, preferably about 35% to 45%.

The strip then undergoes a second recrystallization anneal 24 that takes the same time and temperature as the first recrystallization anneal. After two recrystallization anneals, the average grain size is 3-20 μm. The average grain size of the alloy after treatment is preferably 5-10 μm.

The alloy is then cold rolled 26 to final gauge, typically on the order of 0.25mm (0.010 inch) to 0.38mm (0.015 inch). The elastic state (springemper) of the final cold rolling is equivalent to that of the C51000 copper alloy.

The alloy is then optimized for resistance to stress relaxation by stress relief annealing 28. One exemplary stress relief anneal is a hood anneal in an inert atmosphere at a temperature of about 200 ℃ to about 300 ℃ for a time of 1 to 4 hours. Another exemplary stress relief anneal is a strip anneal at a temperature of about 250 ℃ to about 600 ℃ for a time period of about 0.5 to about 10 minutes.

After annealing 28 by relieving internal stress, the copper alloy strip can be used to produce a target product such as a spring or a connector in a circuit.

The following examples will highlight the advantages of the alloys of the present invention.

Examples of the invention

Example 1

A copper alloy was prepared according to fig. 1, the composition of which included: 10.5 percent of zinc, 1.7 percent of tin, 0.04 percent of phosphorus, 0 to 2.3 percent of iron and the balance of copper. The yield strength and ultimate tensile strength of the 51mm (2 inch) gauge specimen were measured at room temperature (20 ℃) after stress relief annealing 28.

The yield strength and tensile strength at 0.2% set were measured on a tensile tester. The tensile tester was manufactured by Tinius Olsen, Willow Grove, Pa.

As shown in fig. 2, increasing the iron from 0% to 1% resulted in a significant increase in yield strength. Further increasing the iron content has only a minimal effect on the strength, but the likelihood of hairline formation increases.

The curves in fig. 3 illustrate a similar relationship between iron content and ultimate tensile strength.

Example 2

A copper alloy is processed according to fig. 1, the composition of which comprises: 10.4 percent of zinc, 1.8 percent of iron, 0.04 percent of phosphorus, 1.8 to 4.0 percent of tin and the balance of copper. After annealing 28 to eliminate internal stress, the yield strength and ultimate tensile strength of the specimen were measured.

The curves of fig. 4 illustrate that increasing the tin content results in an increase in yield strength. While figure 5 illustrates that the tin additive has the same effect on ultimate tensile strength.

Since as the tin content increases, the strength monotonicity increases and the conductivity decreases, a trade-off should be made between the desired strength and conductivity to determine the tin content.

Example 3

A copper alloy is processed according to fig. 1, the composition of which comprises: 1.9 percent of iron, 1.8 percent of tin, 0.04 percent of phosphorus, 0 to 15 percent of zinc and the balance of copper. After annealing 28 to eliminate internal stress, the yield strength and ultimate tensile strength of the specimen were measured.

Fig. 6 shows that when the zinc content is less than about 5%, the strength of the alloy is not improved, and as mentioned above, it does not promote the grain refining ability of the iron. When the zinc content is more than 5%, although the conductivity may be decreased, the alloy strength is increased.

The same effect of the zinc additive on the ultimate tensile strength of the alloy is depicted in figure 7.

Example 4

Table 5 shows a series of alloys processed according to figure 1. Alloy a is a published alloy of the EP0769563a1 type. Alloys B and C are alloys produced by the present invention. Alloy D is a conventional C510 copper alloy. All properties were measured in an elastic state after cold rolling at a reduction of 70%.

TABLE 5

Alloy (I)	Composition of	Conductivity% IACS	Tensile strength (ksi) MPa	Yield strength (ksi) MPa
					A	1.8Sn 2.2Fe 0.06P The balance being Cu	33％	(99) 682	(96) 662
B	1.8Sn 2.2Fe 0.06P 5.0Zn The balance being Cu	29％	(99) 682	(94) 648
					C	1.8Sn 2.2Fe 0.06P 10.0Zn The balance being Cu	25％	(108) 745	(101) 696
D	4.27Sn 0.033P The balance being Cu	17％	(102) 703	(96) 662

Table 5 shows that the addition of 5% zinc does not increase the strength of the alloy, but only slightly reduces the conductivity. The addition of 10% zinc had a good effect on strength.

The benefit of the zinc addition is evident from table 6, where the relationship between strength and reduction can be compared.

TABLE 6

Alloy (I)	％Red.	YS	TS	MBR/t GW	MBR/t BW
						A	25	552(80)	572(83)	1.0	1.3
C	25	579(84)	607(88)	0.8	1.6
A	33	572(83)	593(86)	1.0	1.3
						C	33	614(89)	648(94)	0.9	2.1
						A	58	662(96)	683(99)	1.7	3.9
C	60	662(96)	703(102)	1.6	6.4
A	70	690(100)	717(104)	1.9	6.3
						C	70	696(101)	745(108)	1.9	≥7

% Red ═ gauge reduction after final cold rolling step (reference numeral 26 in FIG. 5)

YS yield strength in MPa and (ksi)

TS tensile strength in MPa and (ksi)

MBR/t (GW) is bent by 180 DEG along the curvature radius in a good manner (good way)

MBR/t (BW) is bent 180 DEG along the curvature radius in a bad way (bad way)

An additional benefit of the addition of zinc is that it improves the good mode bending behaviour, which result is obtained with alloy C. Bend formability was measured by bending a 12.7mm (0.5 inch) wide strip 180 ° along a drum of known radius of curvature. The minimum roll value at which the strip material is bent along the roll without causing cracks or "orange peel" is taken as the value of the bending formability. "good mode" bending, that is bending in the plane of the sheet and in the longitudinal direction (rolling direction) perpendicular to the thickness of the strip as it is rolled down. "bad mode" is bending parallel to the longitudinal direction. The bend formability is reported as MBR/t, the minimum bend radius without cracking or orange peel, divided by the strip thickness.

In general, the strength is increased and the bending formability is decreased. However, with the alloy of the present invention, the addition of 10% zinc not only increases the strength but also increases the good mode bending performance.

Example 5

Table 7 shows the composition of the alloy processed from fig. 1, with the remainder of the composition being copper. Table 7 illustrates the effect of cobalt partially replacing iron in the tin brass alloy of the present invention.

Zn	Sn	Fe	Co	P	As-cast grain size	CR22％(RA) YS/UTS/EL (MPa/MPa/％) (ksi/ksi/％)	CR65(RA) YS/UTS/EL (MPa/MPa/％) (ksi/ksi/％)
								10.4	1.80	1.5	0.5	0.04	Thin and thin	572/600/7 (83/87/7)	696/745/4 (101/108/4)
10.4	1.80	1.78	-	0.04	Thin and thin	558/586/11 (81/85/11)	703/795/2 (102/108/2)
								10.4	1.80	1.5	-	0.04	Coarse	-	-

Yield strength of YS ═ yield strength

UTS ═ ultimate tensile strength

Elongation (EL)

CR cold rolling

Annealing for relieving internal stress

Table 8 shows that the magnetic permeability of the hot rolled sheet produced with tin brass containing cobalt is higher than that of the same alloy produced with equal amounts of iron (the relationship between the amounts of iron and cobalt is 0.6Co ═ Fe).

Zn	Sn	Fe	Co	P	As-cast grain size	Magnetic permeability (Hot rolled plate)
							10.2	1.87	2.02	-	0.03	Thin and thin	1.05-1.10
10.5	1.80	-	3.3	0.04	Thin and thin	1.2

Although the foregoing relates specifically to direct chill casting, the alloys of the present invention may be cast by other methods. Alternative processes have higher cooling rates, such as spray casting (spincasting) and strip casting. Higher cooling rates reduce the size of the first peritectic iron particles and are believed to shift the critical maximum iron content to higher values, such as 4%.

It is apparent that there has been provided in accordance with the present invention an iron-modified phosphor bronze which fully satisfies the aims, means, and advantages set forth hereinbefore. While the invention has been described in conjunction with embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the broad scope of the appended claims.

Claims (18)

1. A copper alloy, characterized in that it essentially consists of: 1 to 4 weight percent tin; the zinc is in a content of 20% by weight from the content effective for promoting grain refinement by peritectic generation; up to 0.4% by weight phosphorus; the mixture of iron and cobalt quantitatively satisfies the equation: 0.8-0.4% of Fe + MCo (weight percentage), wherein M is 0.45-0.65; the balance being copper and unavoidable impurities, the refined as-cast average grain size of the alloy being less than 100 μm.

2. The copper alloy of claim 1, wherein said zinc content is between 8% and 12% by weight.

3. The copper alloy of claim 2, wherein Fe + MCo is 1.6% to 2.2%.

4. The copper alloy of claim 2, wherein one or more peritectic reaction initiators selected from iridium, niobium, vanadium and molybdenum are substituted for a portion of said iron + cobalt.

5. The copper alloy according to any one of claims 1 to 4, wherein an element selected from the group consisting of aluminum, manganese and mixtures thereof replaces said zinc in a 1: 1 atomic ratio.

6. The copper alloy of claim 5, wherein said tin content is 1.2% to 2.2%.

7. The copper alloy of claim 6, wherein said phosphorus content is between 0.03% and 0.3%.

8. The copper alloy of claim 6 wherein said alloy further comprises an additive selected from the group consisting of nickel, magnesium, beryllium, silicon, zirconium, titanium, chromium, and mixtures thereof, wherein each component of said additive is present in an amount less than 0.4% by weight.

9. The copper alloy of claim 6, wherein said alloy is mechanically deformable to a thickness of from 0.13mm (0.05 inch) to 0.38mm (0.015 inch) and has an average final nominal grain size of 3 to 20 μm.

10. An electrical circuit connector produced from the copper alloy of claim 6.

11. A spring produced from the copper alloy of claim 9.

12. The copper alloy of claim 5, wherein said alloy contains no more than an impurity level of cobalt.

13. A copper alloy, characterized in that it consists essentially of: 1 to 4 weight percent tin; a peritectic reaction initiator in an amount effective to provide said copper alloy with a fine-grained microstructure without unduly degrading electrical conductivity and strength, the initiator being selected from the group consisting of cobalt, iridium, vanadium and molybdenum and mixtures thereof; zinc in an amount from that effective to promote peritectic induced grain refinement to 20% by weight; up to 0.4 wt% phosphorus; the balance being copper and unavoidable impurities, the alloy having a refined as-cast average grain size of less than 100 μm.

14. The copper alloy of claim 13, wherein said peritectic reaction initiator is cobalt and is present in an amount of about 3.2% to about 4.4%.

15. The copper alloy of claim 13, wherein said peritectic reaction initiator is iridium and is present in an amount of about 10% to about 20%.

16. The copper alloy of claim 13, wherein said peritectic reaction initiator is niobium and is present in an amount of about 0.01% to about 5%.

17. The copper alloy of claim 13, wherein said peritectic reaction initiator is vanadium and is present in an amount of about 0.01% to about 5%.

18. The copper alloy of claim 13, wherein said peritectic reaction initiator is molybdenum in an amount of about 0.5% to about 5%.

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