Copper-zinc alloy

Abstract

The invention relates to a copper-zinc alloy comprising 66.0 to 73.0 wt.% Cu, 1.5 to 2.5 wt.% Si, 0.01 to 0.15 wt.% P, at most 0.1 wt.% Pb, balance zinc and unavoidable impurities.

Description

[0001] The invention relates to a copper-zinc alloy, in particular a lead-free copper-zinc alloy.

[0002] Copper-zinc alloys and brass alloys are used, among other things, for the production of components in the plumbing sector. It is no longer permitted to add large amounts of hazardous elements, such as lead or as, to such alloys. Such brass alloys must be "lead-free," meaning they must contain no more than 0.1% lead by weight.

[0003] The previously permitted addition of lead has improved the machining properties of such brass alloys. Efforts are now underway to find lead-free brass alloys that offer machining properties similar to those of lead-containing brass alloys.

[0004] EP 3 099 832 B1 describes a conventional lead-containing brass alloy. The mandatory lead content is 0.02 to 1.00 wt.%.

[0005] EP 1 790 742 B1 discloses a lead-free brass alloy to which 0.5 to 2.5 wt.% Bi and 0.02 to 0.10 wt.% Sb are mandatory. This known brass alloy has a relatively low copper content of 61.0 to 63.0 wt.%. It is also characterized by a relatively low dezincification depth in the range of 10 to 25 µm.

[0006] JPS5838500 B2 also discloses a brass alloy with improved dezincification resistance. To improve dezincification resistance, this alloy also contains Sb. Sb, like Pb, is classified as toxic.

[0007] The object of the invention is to provide a lead-free brass alloy with improved dezincification resistance that can be produced as cost-effectively as possible. A further objective of the invention is to provide the brass alloy with good machinability. Furthermore, the alloy should be processable, if possible, by continuous casting and hot forming.

[0008] This object is achieved by a copper-zinc alloy having the features of patent claim 1. Advantageous embodiments of the invention emerge from the features of the dependent patent claims.

[0009] According to the invention, the proposed copper-zinc alloy comprises 66.0 to 73.0 wt% Cu, 1.5 to 2.5 wt% Si, 0.01 to 0.15 wt% P, maximum 0.1 wt% Pb, balance zinc and unavoidable impurities.

[0010] The proposed copper-zinc alloy requires relatively low Cu contents of up to 73.0 wt.%. It can be produced cost-effectively. The proposed addition of P improves dezincification resistance. The mandatory addition of Si improves the machinability of the proposed copper-zinc alloy. At the same time, the proposed alloy is surprisingly processable by continuous casting and hot forming.

[0011] The proposed copper-zinc alloy may optionally contain one or more of the following elements: less than 0.15 wt% As, less than 0.10 wt% Al, less than 0.25 wt% Sn.

[0012] The proposed optional addition of As, similar to the addition of P, contributes to improving dezincification resistance. The optional addition of Al promotes the formation of a covering layer and thus also contributes to improving dezincification resistance. A further optional addition of Sn improves the strength and dezincification resistance of the proposed copper-zinc alloy.

[0013] The Cu content can preferably be 68.0 to 72.5 wt.%, particularly preferably 68.5 to 71.0 wt.%. The lower the Cu content, the more cost-effectively the copper-zinc alloy can be produced.

[0014] The Si content can be 1.6 to 2.3 wt.%, preferably 2.0 to 2.3 wt.%. The proposed Si contents contribute to an improvement in the machinability of the copper-zinc alloy.

[0015] The P content is preferably 0.05 to 0.07 wt.%. This ensures sufficiently good dezincification resistance.

[0016] The proposed copper-zinc alloy preferably contains 0 to 3% β-phase, 12 to 28% γ-phase, and the remainder α-phase. The γ-phase content is preferably set at 25 to 27%.

[0017] With the proposed phase composition, excellent processability of the proposed copper-zinc alloy is achieved.

[0018] The proposed copper-zinc alloy preferably has a dezincification depth of at most 200 µm, preferably less than 70 µm.

[0019] The proposed lead-free copper-zinc alloy is particularly suitable for the production of components in the field of sanitary technology in general, especially for drinking water applications. Example alloys:

[0020] Alloy 1: Cu: 70.0 wt%, Si: 2.2 wt%, P: 0.06 wt%, Pb: 0.08 wt%, Zn: balance. Alloy 2: Cu: 69.62 wt%, Si: 2.26 wt%, P: 0.054 wt%, Pb: <0.1 wt%, Zn: balance.

[0021] The following table shows an overview of the maximum dezincification depths (ET) in [µm] and the composition in [wt.%] of two example alloys No. 2986 and No. 2987 in comparison to copper-zinc alloys according to the invention, namely Nos. 2988, 2991, 2992, 2995 and 2996. 2986 2987 2988 2991 2992 2995 2996 Cu 64,76 66,62 68,8 72,14 70,88 68,78 69,62 Pb 0,01 <0,01 <0,01 <0,01 <0,01 <0,01 <0,01 If 0,78 1,58 1,52 2,0 2,22 2,27 2,26 P 0,071 0,071 0,068 0,061 0,065 0,061 0,054 Zn Rest Rest Rest Rest Rest Rest Rest Max. ET (µm) 540 420 140 36 52 172 66

[0022] The single figure shows a reflected-light micrograph of a copper-zinc alloy according to the invention. It can be seen that the maximum dezincification depth was 66 µm.

Claims

1. A copper-zinc alloy comprising 66.0 to 73.0 wt% Cu, 1.5 to 2.5 wt% Si, 0.01 to 0.15 wt% P, at most 0.1 wt% Pb, the remainder zinc and unavoidable impurities.

2. A copper-zinc alloy according to claim 1, comprising less than 0.15 wt% As.

3. Copper-zinc alloy according to one of the preceding claims, comprising less than 0.10 wt.% Al.

4. A copper-zinc alloy according to any one of the preceding claims, comprising less than 0.25 wt% Sn.

5. Copper-zinc alloy according to one of the preceding claims, wherein the Cu content is 68.0 to 72.5 wt.%, preferably 68.5 to 71.0 wt.%.

6. Copper-zinc alloy according to one of the preceding claims, wherein the Si content is 1.6 to 2.3 wt.%, preferably 2.0 to 2.3 wt.%.

7. Copper-zinc alloy according to one of the preceding claims, wherein the P content is 0.05 to 0.07 wt%.

8. Copper-zinc alloy according to one of the preceding claims, comprising 0 to 3% β-phase, 12 to 28% γ-phase, remainder α-phase.

9. A copper-zinc alloy according to claim 8, wherein the γ-phase content is 25 to 27%.

10. Copper-zinc alloy according to one of the preceding claims, with a dezincification depth of at most 200µm.

11. Use of a copper-zinc alloy according to one of the preceding claims for the production of components for drinking water applications.

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