Patent Application
20250019797
This application claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 10 2023 118 693.0, filed Jul. 14, 2023; the prior application is herewith incorporated by reference in its entirety.
The invention relates to a copper-zinc alloy, more particularly a lead-free copper-zinc alloy.
Copper-zinc alloys or brass alloys have uses including the production of components in the sanitary sector. Here it is no longer permissible nowadays for such alloys to have additions of substantial amounts of elements that pose a hazard to health, such as Pb or As, for example. Such brass alloys are required to be “lead-free”, thus having a maximum Pb content of 0.1% by weight.
The formerly permissible addition of Pb did produce an improvement in the machining properties of such brass alloys. Efforts are now underway to find lead-free brass alloys which have similarly good machining properties to lead-containing brass alloys.
European patent EP 3 099 832 B1 describes a conventionally lead-containing brass alloy. The mandatory lead content in this case is 0.02% to 1.00% by weight.
European patent EP 1 790 742 B1 discloses a lead-free brass alloy with mandatory additions of 0.5% to 2.5% by weight of Bi and also 0.02% to 0.10% by weight of Sb. The known brass alloy has a relatively low copper content, of 61.0% to 63.0% by weight. It is also notable for a relatively low dezincification depth, in a range from 10 to 25 μm.
Japanese patent JPS5838500 B2 likewise discloses a brass alloy featuring improved dezincification resistance. To improve the dezincification resistance, this alloy likewise contains Sb. Sb—similarly to Pb—is classed as toxic.
It is an object of the invention to specify a lead-free brass alloy with improved dezincification resistance that can be produced very cost-effectively indeed. According to a further objective of the invention, the brass alloy is to be notable for good machinability. Moreover, the alloy is to be workable as far as possible by means of continuous casting and hot forming.
This object is achieved by a copper-zinc alloy having the features of the independent claim. Practical configurations of the invention are evident from the features of the dependent claims.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a copper-zinc alloy, 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 when read in connection with the accompanying drawings.
The single figure of the drawing is an illustration showing a reflected-light micrograph of a copper-zinc alloy according to the invention.
In accordance with the invention, the proposed copper-zinc alloy contains:
The proposed copper-zinc alloy operates with relatively low Cu contents, of at most 73.0% by weight. It can be produced cost-effectively. The proposed addition of P produces an improved dezincification resistance. As a result of the mandatory addition of Si, the machinability of the proposed copper-zinc alloy is improved. At the same time, surprisingly, the proposed alloy can be worked by means of continuous casting and hot forming.
The proposed copper-zinc alloy may electively contain one or more of the following elements:
The proposed elective addition of As—similarly to the addition of P—contributes to improving the dezincification resistance. The optional addition of Al promotes the formation of an outer layer and so also contributes to improving the dezincification resistance. A further-optional addition of Sn produces an improvement in the strength and dezincification resistance of the proposed copper-zinc alloy.
The Cu content may be preferably 68.0% to 72.5%, more preferably 68.5% to 71.0% by weight. The lower the Cu content, the more cost-effectively the copper-zinc alloy can be produced.
The Si content may be 1.6% to 2.3%, preferably 2.0% to 2.3% by weight. The proposed Si contents contribute to an improvement in the machinability of the copper-zinc alloy.
The P content is preferably 0.05% to 0.07% by weight. With this, sufficiently good dezincification resistance is achieved.
The proposed copper-zinc alloy usefully contains 0% to 3% β-phase, 12% to 28% y-phase, balance a-phase. The y-phase content is established preferably at 25% to 27%.
The phase composition proposed achieves outstanding workability of the proposed copper-zinc alloy.
The proposed copper-zinc alloy preferably has a dezincification depth of at most 200 μm, preferably less than 70 μm.
The lead-free copper-zinc alloy proposed is especially suitable for producing components generally in the sector of sanitary engineering, more particularly for drinking-water applications.
Example alloys:
Alloy 1:
Alloy 2:
The table below shows, in an overview, the maximum dezincification depths (DD) in [μm] and also the composition in [% by weight] of two example alloys, numbered 2986 and 2987, in comparison to copper-zinc alloys of the invention, these being numbered 2988, 2991, 2992, 2995 and 2996.
Referring now to single figure of the drawing there is shown a reflected-light micrograph of a copper-zinc alloy according to the invention. From this it is evident that the maximum dezincification depth of the copper-zinc alloy here was 66 μm.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2023 118 693.0 | Jul 2023 | DE | national |
