Copper-zinc alloy

Abstract

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

Description

Technical Field

[0001] The present invention relates to a copper-zinc alloy, and more particularly to a lead-free copper-zinc alloy. Background Art

[0002] Copper-zinc alloys or brass alloys are used in particular for the production of components in the sanitary sector. Here, it is no longer permitted to add large amounts of health-damaging elements such as Pb or As to such alloys. Such brass alloys must be "lead-free", ie have a Pb content of no more than 0.1% by weight.

[0003] The previously permitted addition of lead improves the machinability of such brass alloys. Efforts are now being made to find lead-free brass alloys which have machinability comparable to that of lead-containing brass alloys.

[0004] EP 3 099 832 B1 describes a conventional lead-containing brass alloy, wherein the mandatory lead content is 0.02% to 1.00% by weight.

[0005] EP 1 790 742 B1 discloses a lead-free brass alloy with mandatory additions of 0.5 to 2.5 wt. % Bi and 0.02 to 0.10 wt. % Sb. The 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 method having improved dezincification resistance. A brass alloy of 1.5 tantalum. To improve dezincification resistance, the alloy also contains Sb. Sb is classified as toxic like Pb. Summary of the invention

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

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

[0009] According to the present invention, the proposed copper-zinc alloy comprises:

[0010] 66.0 wt. % to 73.0 wt. % Cu,

[0011] 1.5 wt% to 2.5 wt% Si,

[0012] 0.01 wt% to 0.15 wt% of P,

[0013] Up to 0.1 wt.% Pb,

[0014] The balance is zinc and unavoidable impurities.

[0015] The proposed copper-zinc alloy is formed with a relatively low Cu content (maximum 73.0 wt. %). It can be produced cost-effectively. The proposed addition of P results in improved dezincification resistance. The machinability of the proposed copper-zinc alloy is improved by the mandatory addition of Si. At the same time, surprisingly, the proposed alloy can be processed by means of continuous casting and hot forming.

[0016] The proposed copper-zinc alloy may optionally contain one or more of the following elements:

[0017] Less than 0.15 wt% As,

[0018] Less than 0.10 wt% Al,

[0019] Less than 0.25 wt% Sn.

[0020] The proposed optional addition of As (similar to the addition of P) contributes to improving the dezincification resistance. The optional addition of Al promotes the formation of a cover layer and thus also contributes to improving the dezincification resistance. The optional addition of Sn also improves the strength and dezincification resistance of the proposed copper-zinc alloy.

[0021] The Cu content may preferably be 68.0 wt% to 72.5 wt%, more preferably 68.5 wt% to 71.0 wt%.The lower the Cu content, the lower the cost of producing the copper-zinc alloy.

[0022] The Si content may be 1.6% to 2.3% by weight, preferably 2.0% to 2.3% by weight. The proposed Si content contributes to improving the machinability of the copper-zinc alloy.

[0023] The P content is preferably 0.05% to 0.07% by weight, thereby achieving sufficiently good dezincification resistance.

[0024] The proposed copper-zinc alloy advantageously contains 0%-3% of β-phase, 12%-28% of γ-phase, and the remainder of α-phase. The γ-phase content is preferably 25%-27%.

[0025] The proposed phase composition achieves excellent processability of the proposed copper-zinc alloy.

[0026] The proposed copper-zinc alloy preferably has a dezincification depth of at most 200 μm, preferably less than 70 μm.

[0027] The proposed lead-free copper-zinc alloy is particularly suitable for producing components generally in the sanitary sector, more particularly for drinking water applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A reflected light micrograph of a copper-zinc alloy of the present invention is shown.

[0029] Example Alloys:

[0030] Alloy 1:

[0031] Cu: 70.0 wt%

[0032] Si: 2.2 wt%,

[0033] P: 0.06 wt%

[0034] Pb: 0.08 wt%

[0035] Zn: Remainder.

[0036] Alloy 2:

[0037] Cu: 69.62 wt%

[0038] Si: 2.26 wt%

[0039] P: 0.054 wt%

[0040] Pb: <0.1 wt%

[0041] Zn: Remainder.

[0042] The table below shows in an overview the maximum dezincification depth (ET) in [μm] and the composition in [wt %] of two exemplary alloys Nos. 2986 and 2987 compared to the copper-zinc alloys according to the invention (Nos. 2988, 2991, 2992, 2995 and 2996).

[0043] 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 here is 66 μm.

Claims

1. A copper-zinc alloy comprising: 66.0 wt. % to 73.0 wt. % Cu, 1.5 wt% to 2.5 wt% Si, 0.01 wt% to 0.15 wt% of P, Up to 0.1 wt.% Pb, The balance is zinc and unavoidable impurities.

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

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

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

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

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

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

8. The copper-zinc alloy according to any one of the preceding claims, comprising 0% to 3% of β phase, 12% to 28% of γ phase, the balance being α phase.

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

10. The copper-zinc alloy according to any one of the preceding claims, having a dezincification depth of at most 200 μm.

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

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