Copper-Zinc Alloy and Synchronizer Ring Produced Therefrom

Abstract

A copper-zinc alloy is particularly suitable for forming synchronizer rings. The novel alloy contains 55 to 75 wt. % copper, 0.1 to 8 wt. % aluminum, 0.3 to 3.5 wt. % iron, 0.5 to 8 wt. % manganese, 0 to less than 5 wt. % nickel, 0 to less than 0.1 wt. % lead, 0 to 3 wt. % tin, 0.3 to 5 wt. % silicon, 0 to less than 0.1 wt. % cobalt, 0 to less than 0.05 wt. % titanium, 0 to less than 0.02 phosphorus, unavoidable impurities and the remainder zinc.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuing application, under 35 U.S.C. § 120, of copending international application PCT/EP2006/011622, filed Dec. 5, 2006, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German patent application No. DE 10 2005 059 391.7, filed Dec. 13, 2005; the prior applications are herewith incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a novel copper-zinc alloy. The invention also relates to a use of such a copper-zinc alloy for producing a synchronizer ring, as well as to a synchronizer ring.

Copper-zinc alloys or brasses are used in the plumbing and sanitary industries as well as in the electronics industry. In the automobile industry, brass rings with a high wear resistance and a high friction coefficient are employed for synchronizer rings which are used in a mechanical gearbox for synchronizing the gear wheel.

In order to be able to process a copper-zinc alloy easily, particularly by machining, a certain brittleness of the material must be achieved in order to avoid as far as possible creating long swarf during the processing, which would be difficult to transport away from the workplace and the processing tool. As is known, this brittleness desired for the mechanical processing of brasses is achieved by adding a certain proportion of lead. Lead in corresponding doses, however, disadvantageously represents a hazard to human health.

It is therefore desirable to provide mechanically processable copper-zinc alloys which have as low as possible or even no lead content. Although various European Union guidelines still permit the use of lead in brass alloys, it is nevertheless to be expected that the lead content of up to 4% allowed for brasses used in motor vehicles will be corrected downwards.

A lead-free copper-zinc alloy for applications in the plumbing industry is known from European patent EP 1 045 041 B1 and U.S. Pat. No. 6,413,330 B1. The disclosed alloy comprises 69 to 79 wt. % copper, 2 to 4 wt. % silicon, 0.1 to 1.5 wt. % aluminum and 0.02 to 0.25 wt. % phosphorus. This interaction of the components silicon, aluminum and phosphorus is intended to produce a gamma phase of the alloy, which ensures good machine processability without using lead.

Low-lead copper-zinc alloys with a high wear strength for use in a synchronizer ring are known from the commonly assigned German patents DE 29 19 478 C2, DE 37 35 783 C1 (cf. U.S. Pat. No. 4,954,187) and European patent EP 0 657 555 B1.

German patent DE 29 19 478 C2 discloses a copper-zinc alloy having 70 to 73 wt. % copper, 6 to 8 wt. % manganese, 4 to 6 wt. % aluminum, 1 to 4 wt. % silicon, 1 to 3 wt. % iron, 0.5 to 1.5 wt. % lead, 0 to 0.2 wt. % nickel, 0 to 0.2 wt. % tin and zinc as the remainder. In order to achieve the high wear strength, this alloy comprises a lattice of 60 to 85% a mixed crystal predominantly as a finely disperse distribution in the β phase. Lead is alloyed to it in a relatively small weight proportion.

German patent DE 37 35 783 C1 and its counterpart U.S. Pat. No. 4,954,187 describe a copper-zinc alloy to be used particularly for synchronizer rings, which consists of 50 to 65 wt. % copper, 1 to 6 wt. % aluminum, 0.5 to 5 wt. % silicon, 5 to 8 wt. % nickel as well as selectively 0 to 1 wt. % iron, 0 to 2 wt. % lead and zinc as the remainder. A lead proportion of less than 2 wt. % is optional. The high wear resistance is achieved in that the nickel is present predominantly as an intermetallic compound with silicon and aluminum.

A copper-zinc alloy having high wear resistance is furthermore known from European patent EP 0 657 555 B1, which comprises 40 to 65 wt. % copper, 8 to 25 wt. % nickel, 2.5 to 5 wt. % silicon, 0 to 3 wt. % aluminum, 0 to 3 wt. % iron, 0 to 2 wt. % manganese, 0 to 2 wt. % lead, the remainder being zinc as well as unavoidable impurities. The high wear resistance is achieved by the very high nickel and silicon contents, the effect of which is that the matrix contains a high volume content of nickel silicides. The lattice comprises no y phase and consists primarily of β phases. Lead in small amounts is considered useful with a view to good processability.

Furthermore, German patent DE 28 30 459 C3 and its counterpart U.S. Pat. No. 4,191,564 relate to a copper-nickel alloy with high wear resistance, which consists of 45 to 75 wt. % copper, 2 to 7 wt. % aluminum, 0.1 to 2 wt. % iron, 1 to 5 wt. % nickel, 0.5 to 2 wt. % silicon, 0.1 to 2 wt. % cobalt and the remainder zinc. For the high wear resistance, this alloy furthermore contains an intermetallic compound of the nickel-silicon type, into which aluminum and cobalt are also bound. It does not contain lead.

Finally, in German patent DE 38 09 994 C3 and its counterpart U.S. Pat. No. 4,995,924, a copper-zinc alloy is formed for a synchronizer ring from 20 to 40 wt. % zinc, 2 to 8 wt. % aluminum, from at least two further components which form intermetallic compounds, at least one of the components being titanium, and for the remaining part from copper and random impurities. The high wear resistance is achieved by the intermetallic compounds. Lead is unnecessary.

A feature common to the low-lead and lead-free copper-zinc alloys which have a high wear strength is that they have a high content of intermetallic phases. These intermetallic phases lead to a certain brittleness of the alloy, so that it becomes easier to machine process. The swarf breaks readily and can be transported away. For this reason, the proportion of lead can be reduced or lead can be omitted. If a high wear resistance is not required, as in U.S. Pat. No. 6,413,330 and European patent EP 1 045 041 B1, then the lead content can be reduced by stabilizing a y phase in the alloy through an interaction of silicon, aluminum and phosphorus. This alloy contains phosphorus in order to ensure a dezincing resistance of the alloy for the desired application in the sanitary industry.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a copper-zinc alloy, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides a maximally wear-resistant copper-zinc alloy which is largely lead-free and which, in particular, is suitable for use in a synchronizer ring.

With the foregoing and other objects in view there is provided, in accordance with the invention, a copper-zinc alloy which comprises 55 to 75 wt. % copper, 0.1 to 8 wt. % aluminum, 0.3 to 3.5 wt. % iron, 0.5 to 8 wt. % manganese, 0 to less than 5 wt. % nickel, 0 to less than 0.1 wt. % lead, 0 to 3 wt. % tin, 0.3 to 5 wt. % silicon, 0 to less than 0.1 wt. % cobalt, 0 to less than 0.05 wt. % titanium, 0 to less than 0.02 wt. % phosphorus, unavoidable impurities and the remainder zinc.

The invention is based on the idea of deliberately lowering the lead content below 0.1 wt. % without providing compensation in respect of the desired mechanical processability by intermetallic phases or stabilisation of a y phase. A sufficient wear resistance is ensured by the necessary alloy components aluminum, manganese, iron and silicon. Manganese, iron and silicon in the specified quantitative ranges lead to a sufficient basic proportion of intermetallic phases in the copper-zinc alloy. In particular, aluminum hardens the mixed crystal. Manganese makes a positive contribution to the wear resistance. An improvement can be achieved through the optionally mentioned further alloy components nickel and tin. It may contain cobalt and titanium up to below the specified limits. Alloying it with them beyond this, however, is unnecessary for the desired mechanical processability and for achieving the desired wear resistance. Phosphorus as an alloy component is unnecessary for improving the dezincing resistance.

Lowering the lead content below 0.1 wt. % without increasing the proportion of intermetallic phases is surprisingly possible, contrary to the previous opinion of the technical world, since it has been found after extensive studies that it is possible to machine the claimed copper-zinc alloy, particularly for producing a synchronizer ring, even without adding lead.

The wear resistance and the abrasion strength of the copper-zinc alloy can be improved when the copper-zinc alloy advantageously comprises aluminum in a proportion of from 0.5 to 2.5 wt. %, iron in a proportion of from 0.3 to 1 wt. %, manganese in a proportion of from 0.5 to 5 wt. %, nickel in a proportion of from 0.5 to less than 5 wt. %, tin in a proportion of from 0 to 1.5 wt. % and silicon in a proportion of from 0.3 to 2 wt. %.

In an alternative advantageous embodiment of the invention, the copper-zinc alloy comprises a higher proportion of aluminum and is distinguished in that it comprises aluminum in a proportion of from 3 to 8 wt. %, iron in a proportion of from 1 to 3 wt. %, manganese in a proportion of from 5 to 8 wt. %, nickel in a proportion of from 0 to less than 0.5 wt. %, tin in a proportion of from 0 to less than 0.5 wt. % and silicon in a proportion of from 1 to 4 wt. %. Such a material has the mechanical properties necessary for a synchronizer ring.

The copper-zinc alloy is suitable for producing a synchronizer ring—also referred to as a synchronizing ring—particularly by machining.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is described herein as embodied in copper-zinc alloy and synchronizing ring produced therefrom, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments and examples.

BRIEF DESCRIPTION OF THE DRAWING

The sole figure of the drawing is a perspective view of a synchronizer ring according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figure of the drawing in detail there is shown a synchronizer ring—also referred to as a synchronizing ring—as can be produced in particular by machining from a copper-zinc alloy. The synchronizer ring 1 has an inner surface 3, which is intended for friction pairing with a conical friction partner. Teeth 2, which engage with corresponding slots on a mating slotted sleeve, are arranged on the outer circumference of the synchronizer ring 1. In order to improve the oil run-off, the inner surface 3 has oil channels 4 fitted in an axial direction, which rapidly transport away the oil present in the case of friction pairing.

EXAMPLES

Four alloys were studied in all, each pair of alloys differing only in its lead content. Alloy 1A contains 57.9 wt. % copper, 1.65 wt. % aluminum, 0.4 wt. % iron, 1.95 wt. % manganese, 0.55 wt. % lead, 0.6 wt. % silicon and the remainder zinc. Alloy 1 B differs from this alloy 1A in that lead is absent from it, i.e. it contains lead only at an unavoidable impurity level of 0.02 wt. %. Alloy 2β contains 69.7 wt. % copper, 5.2 wt. % aluminum, 1.1 wt. % iron, 7.8 wt. % manganese, 0.8 wt. % lead, 1.8 wt. % silicon and the remainder zinc as well as unavoidable impurities. Alloy 2B differs from alloy 2A in that it contains lead only at an unavoidable level of 0.05. Alloys A are comparative alloys containing lead, which are suitable in respect of their wear resistance and processability for synchronizer rings. The alloys B are embodiments of the invention.

Example 1

For the said alloys, the wear strength in km/g and the friction coefficient are determined in a Reichert friction-and-wear balance with a sliding speed of 1.65 m/sec and a load of 52 N/mm² over a total traveled distance of 2500 m. To this end a brass pin made of the respective test alloy with a diameter of 2.7 mm is pressed with the specified load onto a revolving steel ring. The wear strength and the friction coefficient are determined from the weight loss of the brass pin after the specified running distance. The result is summarized in the following table:

	Wear strength
Alloy, Number	(km/g)	Friction coefficient
1A	201	0.12
1B	235	0.12
2A	1215	0.11
2B	1458	0.11

It can be seen that the wear strength and the friction coefficient of the lead-free alloys B are not inferior relative to the alloys A containing lead, but on the contrary have increased.

Example 2

Cutting tests are carried out with the said alloys. To this end a screw thread with a thread depth of 0.37 mm, a pitch of 0.65 mm and a flank angle of 60° is cut into synchronizer rings according to FIG. 1, which are made of the test alloys. The thread groove is run through five times in all; i.e. there are five thread chases. A hard metal material of quality K20 according to DIN 4990 is used as the thread cutting material. After a defined number of thread grooves cut with the cutting tool, the tool wear is measured. To this end the difference in the cross-sectional area of the thread pitch before and after carrying out the test is determined. The following result is obtained:

	Number of thread
Alloy, Number	grooves cut	Tool wear in mm2
1A	6846	0.0226
1B	14670	0.0085
2A	10273	0.0015
2B	10273	0.0005

The test was stopped after 6848 thread grooves for alloy 1A, since significant tool wear had already taken place here. It can be established that the tool wear with the lead-free alloys B turns out to be less than with the alloys A containing lead.

Example 3

The swarf removed in the cutting tests carried out according to Example 2 was observed. It was established that although the swarf of the lead-free alloys B was longer compared with the alloys A containing lead, it did not form in such a way as to interlink and tangle together. Contrary to expectation, the swarf can be transported away without problems during machining.

The lead-free alloys are suitable particularly for producing a synchronizer ring. The need for the addition of lead to improve the mechanical processability is therefore obviated.

Claims

1. A copper-zinc alloy, comprising:

55 to 75 wt. % copper;

0.1 to 8 wt. % aluminum;

0.3 to 3.5 wt. % iron;

0.5 to 8 wt. % manganese;

0 to less than 5 wt. % nickel;

0 to less than 0.1 wt. % lead;

0 to 3 wt. % tin;

0.3 to 5 wt. % silicon;

0 to less than 0.1 wt. % cobalt;

0 to less than 0.05 wt. % titanium;

0 to less than 0.02 wt. % phosphorus;

unavoidable impurities; and

a remainder zinc.

2. The copper-zinc alloy according to claim 1, which contains nickel in an amount of less than 5 wt. % nickel, lead in an amount of less than 0.1 wt. %, tin in an amount of up to 3 wt. %, cobalt in an amount of less than 0.1 wt. %, titanium in an amount of less than 0.05 wt. %, and phosphorus in amount of less than 0.02 wt. %.

3. The copper-zinc alloy according to claim 1, which contains aluminum in a proportion of from 0.5 to 2.5 wt. %, iron in a proportion of from 0.3 to 1 wt. %, manganese in a proportion of from 0.5 to 5 wt. %, nickel in a proportion of from 0.5 to less than 5 wt. %, tin in a proportion of from 0 to 1.5 wt. %, and silicon in a proportion of from 0.3 to 2 wt. %.

4. The copper-zinc alloy according to claim 1, which contains aluminum in a proportion of from 3 to 8 wt. %, iron in a proportion of from 1 to 3 wt. %, manganese in a proportion of from 5 to 8 wt. %, nickel in a proportion of from 0 to less than 0.5 wt. %, tin in a proportion of from 0 to less than 0.5 wt. %, and silicon in a proportion of from 1 to 4 wt. %.

5. The copper-zinc alloy according to claim 1, which contains at least one of the following components: nickel in an amount of less than 5 wt. %, lead in an amount of less than 0.1 wt. %, tin in an amount of up to 3 wt. %, cobalt in an amount of less than 0.1 wt. %, titanium in an amount of less than 0.05 wt. %, and phosphorus in amount of less than 0.02 wt. %.

6. The copper-zinc alloy according to claim 1, which contains at least two of the following components: nickel in an amount of less than 5 wt. %, lead in an amount of less than 0.1 wt. %, tin in an amount of up to 3 wt. %, cobalt in an amount of less than 0.1 wt. %, titanium in an amount of less than 0.05 wt. %, and phosphorus in amount of less than 0.02 wt. %.

7. The copper-zinc alloy according to claim 1, which contains at least three of the following components: nickel in an amount of less than 5 wt. %, lead in an amount of less than 0.1 wt. %, tin in an amount of up to 3 wt. %, cobalt in an amount of less than 0.1 wt. %, titanium in an amount of less than 0.05 wt. %, and phosphorus in amount of less than 0.02 wt. %.

8. The copper-zinc alloy according to claim 1, which contains at least four of the following components: nickel in an amount of less than 5 wt. %, lead in an amount of less than 0.1 wt. %, tin in an amount of up to 3 wt. %, cobalt in an amount of less than 0.1 wt. %, titanium in an amount of less than 0.05 wt. %, and phosphorus in amount of less than 0.02 wt. %.

9. A synchronizer ring consisting of a copper-zinc alloy according to claim 1.

10. A method of producing a synchronizer ring, which comprises:

providing a copper-zinc alloy according to claim 1; and

forming a synchronizer ring from the copper-zinc alloy.

11. The method according to claim 10, wherein the forming step comprises machining the synchronizer ring from the copper-zinc alloy.