Lead-free and antimony-free brass alloy

Abstract

A lead-free and antimony-free brass alloy contains from 56 to 66% by weight of Cu, from 0.1 to less than 0.5% by weight of Mg, less than 0.1% by weight of Pb, and a balance of Zn. Unavoidable impurities are also present. According to other embodiments, different amounts of As, P, AI, Sn, Cu, Mg, Pb, In and Zn may be provided as well.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is a continuation-in-part of co-pending U.S. patent application Ser. No. 17 / 874,712, filed Jul. 27, 2022, which is based upon and claims the priority under 35 U.S.C. § 119 of German Patent Application No. DE 10 2021 119 474.1, filed Jul. 27, 2021; which patent applications are each incorporated herein by reference in its entirety.FIELD AND BACKGROUND OF THE INVENTION

[0002] The invention relates to a lead-free and antimony-free brass alloy.

[0003] In the past, the machinability of brass alloys has been improved by adding Pb in an extent of up to 4 wt %. However, adding Pb is no longer allowable, due to legal stipulations.

[0004] It has been found that the addition of Pb can be replaced by an addition of Bi. It has emerged, however, that the addition of Bi leads to hot embrittlement of the brass alloy. Brass alloys of that kind have only limited capacity for hot forming. Brass alloys of these kinds, consequently, are not used for compression-molded parts.

[0005] European Patent EP 3 320 122 B1 discloses a brass alloy admixed with neither Pb nor Bi. For improving machinability, it is proposed that 0.005 to Apr. 8, 2025 11:11 PM 1.0 wt % In be added to the brass alloy. While the proposed addition of In does improve the machinability, machining is nevertheless accompanied by formation of relatively long spiral chips, which can lead to blockages as they are transported away, and to tool breakage.

[0006] European Patent Application EP 2 913 415 A1, corresponding to U.S. Patent Application Publication No. 2016 / 0362767, discloses a further lead-free and bismuth-free brass alloy which, moreover, contains no Si. The known alloy contains from 60 to 65 wt % Cu and also from 0.01 to 0.15 wt % Sb.

[0007] The addition of Sb causes hot embrittlement. Alternatively, proposed in European Patent Application EP 2 913 415 A1, corresponding to U.S. Patent Application Publication No. 2016 / 0362767, is an addition of from 0.005 to 0.3 wt % P. The proposed addition of P makes processing by continuous casting more difficult.

[0008] European Patent EP 2 467 507 B1, corresponding to U.S. Patent Application Publication No. 2012 / 0207642, discloses a lead-free brass alloy which contains Fe, Ni and Sn.

[0009] European Patent EP 2 133 437 B1, corresponding to U.S. Pat. No. 8,425,697 and U.S. Patent Application Publications Nos. 2010 / 0080731, 2009 / 0311127 and 2009 / 0311130, discloses a lead-free free-cutting brass alloy which contains from 0.6 to 2.5 wt % Mg and also from 0.15 to 0.4 wt % P. The addition of P makes processing by continuous casting more difficult.SUMMARY OF THE INVENTION

[0010] It is accordingly an object of the invention to provide a lead-free and antimony-free brass alloy, which overcomes and eliminates the hereinafore-mentioned disadvantages of the heretofore-known alloys of this general type and which has improved machinability. According to a further object of the invention, the brass alloy is to exhibit little hot embrittlement, allowing it to be processed by hot forming.

[0011] With the foregoing and other objects in view there is provided, in accordance with the invention, a lead-free and antimony-free brass alloy comprising:

[0012] from 56 to 66% by weight of Cu,

[0013] from 0.1 to 1.5, preferably from 0.1 to less than 0.5, % by weight of Mg,

[0014] less than 0.1% by weight of Pb,

[0015] a balance by weight of Zn, and

[0016] unavoidable impurities.

[0017] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises less than 0.15% by weight of As.

[0018] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises less than 0.15% by weight of P.

[0019] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises less than 0.1% by weight of Al.

[0020] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises less than 0.1% by weight of Sn.

[0021] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises from 57 to less than 60% by weight Cu.

[0022] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises from 57.5 to 58.5% by weight of Cu.

[0023] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises from 0.1 to less than 0.5% by weight of Mg.

[0024] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises from 0.05 to 0.09% by weight of Pb.

[0025] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises less than 0.005% by weight of IN.

[0026] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy comprises from 40 to 42.5% by weight of Zn.

[0027] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy consists of:

[0028] from 56 to 66% by weight of Cu;

[0029] from 0.1 to less than 0.5% by weight of Mg;

[0030] less than 0.1% by weight of Pb;

[0031] from 40 to 42.5% by weight of Zn; and

[0032] unavoidable impurities.

[0033] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy consists of:

[0034] from 57 to less than 60% by weight of Cu;

[0035] from 0.1 to less than 0.5% by weight of Mg;

[0036] less than 0.1% by weight of Pb;

[0037] from 40 to 42.5% by weight of Zn; and

[0038] unavoidable impurities.

[0039] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy consists of:

[0040] from 57.5 to 58.5% by weight of Cu;

[0041] from 0.1 to less than 0.5% by weight of Mg;

[0042] less than 0.1% by weight of Pb;

[0043] from 40 to 42.5% by weight of Zn; and

[0044] unavoidable impurities.

[0045] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy consists of:

[0046] from 56 to 66% by weight of Cu;

[0047] less than 0.5% by weight of Mg;

[0048] less than 0.1% by weight of Pb;

[0049] from 40 to 42.5% by weight of Zn; and

[0050] unavoidable impurities.

[0051] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy consists of:

[0052] from 56 to 66% by weight of Cu;

[0053] from 0.1 to less than 0.5% by weight of Mg;

[0054] from 0.05% to 0.09% by weight of Pb;

[0055] from 40 to 42.5% by weight of Zn; and unavoidable impurities.

[0056] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy consists of:

[0057] from 56 to 66% by weight of Cu;

[0058] from 0.1 to less than 0.5% by weight of Mg;

[0059] less than 0.1% by weight of Pb;

[0060] less than 0.15% by weight of As;

[0061] less than 0.15% by weight of P;

[0062] less than 0.1% by weight of Al;

[0063] less than 0.1% by weight of Sn;

[0064] less than 0.005% by weight of In;

[0065] from 40 to 42.5% by weight of Zn; and

[0066] unavoidable impurities.

[0067] In another embodiment of the lead-free and antimony-free brass alloy of the invention, the alloy consists of:

[0068] from 56 to 66% by weight of Cu;

[0069] from 0.1 to less than 0.5% by weight of Mg;

[0070] from 40 to 42.5% by weight of Zn; and unavoidable impurities.

[0071] According to another embodiment of the invention, a lead-free and antimony-free brass alloy, consists of:

[0072] from 56 to 66% by weight Cu;

[0073] from 0.1 to less than 0.5% by weight Mg;

[0074] less than 0.1% by weight Pb;

[0075] a balance by weight of Zn; and unavoidable impurities.

[0076] For the purposes of the present invention, [%] is understood to be percent by weight.

[0077] It has surprisingly emerged that through the addition of from 0.1 to less than 0.5% Mg as proposed in the invention, the Pb content can be established at less than 0.1% without undesirable formation of long spiral chips during machining. The proposed brass alloy is notable not only for improved chip breaking but also for little hot embrittlement. It may be processed by hot forming.

[0078] According to the invention a “lead-free and antimony-free brass alloy” is understood to be an alloy which contains less than 0.1% Pb and less than 0.001% Sb.

[0079] According to one advantageous embodiment of the invention, the alloy may contain less than 0.15% As and / or less than 0.15% P and / or less than 0.1% Al and / or less than 0.1% Sn. Sn stabilizes the B solid solution. As leads to improved corrosion resistance of the alloy, with As in particular counteracting removal of zinc. The addition of P improves the machinability of the alloy.

[0080] According to another advantageous embodiment of the invention, from 57 to less than 60%, preferably from 57.5 to 58.5%, of Cu is present. The proposed alloy is more cost-efficient because of the relatively lower Cu content.

[0081] According to another embodiment of the invention there is less than 0.5% Mg, preferably 0.4 or less %. The Mg content proposed herein contributes to improved machinability.

[0082] According to another embodiment of the invention Pb content is suitably in the range from 0.05 to 0.09%. The In content is less than 0.005%.

[0083] According to another advantageous embodiment of the invention, it is proposed that the Zn content be 40 to 42.5%. An alloy having the proposed Zn content displays good machining properties.

[0084] The proposed lead-free and antimony-free brass alloy additionally enables good processing qualities in the continuous casting process.

[0085] Although the invention is illustrated and described herein as embodied in a lead-free and antimony-free brass 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.

[0086] 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.BRIEF DESCRIPTION OF THE FIGURES

[0087] FIG. 1 shows a chip depiction after longitudinal turning of a first example alloy;

[0088] FIG. 2 shows a chip depiction after longitudinal turning of a second example alloy;

[0089] FIG. 3 shows a chip depiction after longitudinal turning of a third example alloy;

[0090] FIG. 4 shows a chip depiction after longitudinal turning of a fourth example alloy;

[0091] FIG. 5 is a picture of the surface of a cast billet with up to 0.10% by weight Mg;

[0092] FIG. 6 is a picture of the surface of a cast billet with up to 0.20% by weight Mg;

[0093] FIG. 7 is a picture of the surface of a cast billet with up to 0.28% by weight Mg; and

[0094] FIG. 8 is a picture of the surface of a cast billet with up to 0.30% by weight Mg.DETAILED DESCRIPTION OF THE INVENTION

[0095] Referring now to FIGS. 1-4 of the drawings in detail, there are seen chip depictions which were produced in each case by subjecting alloys to longitudinal turning at a rotary speed of 850 rpm. An indexable cutting insert was used with the identification KNMX160405 R8IC907. The scale bar included in FIGS. 1 to 4 is 5 mm in each case.

[0096] FIG. 1 shows a chip depiction after longitudinal turning of a first example alloy. The first example alloy is a reference alloy. The first example alloy contains 58% Cu and 42% Zn, meaning that the first example alloy contains no addition of Mg.

[0097] As can be seen from FIG. 1, the longitudinal turning of the example alloy 1 produces long spiral chips. Such spiral chips are unwanted when machining. They may lead to blockages when being transported away, and to tool breakage.

[0098] FIG. 2 shows a chip depiction after the longitudinal turning of a second example alloy. The second example alloy contains 58% Cu, 41.5% Zn and 0.5% Mg. It is apparent that the chips generated during longitudinal turning are shorter than the chips shown in FIG. 1.

[0099] FIG. 3 shows a chip depiction after the longitudinal turning of a third example alloy. The third example alloy is formed of 58% Cu, 41% Zn and 1% Mg. It is clearly apparent that the chips produced are again shorter than the chips generated by the longitudinal turning of the second example alloy.

[0100] FIG. 4 shows a chip depiction after the longitudinal turning of a fourth example alloy. The fourth example alloy is formed of 58% Cu, 40.5% Zn and 1.5% Mg. The chips generated during turning of the fourth example alloy are again smaller than the chips generated by the longitudinal turning of the third example alloy.

[0101] Various horizontal casting attempts were made to improve the surface of a cast billet comprising an alloy according to the invention. In addition to a higher casting temperature, the Mg content was increased step by step. The casting temperature was on average around 1090° C. (1990° F.) and thus slightly higher than for former casting attempts. The Mg content was increased step by step from 0 to 0.31%.

[0102] Overall, the following results could be drawn from the casting attempts:

[0103] Up to 0.10% by weight Mg, the underside of the billet is of good quality, as shown in FIG. 5.

[0104] At 0.20% by weight Mg, first adhesions formed on the underside of the billet, as shown in FIG. 6. The quality is still acceptable overall. At 0.28% by weight Mg, heavy adhesions formed on the underside of the billet; as shown in FIG. 7. The quality is no longer acceptable. At 0.30% by weight Mg, strong adhesions formed on the underside of the billet; as shown in FIG. 8. Melt partially escapes at the stroke marks. The quality is very poor.

[0105] The adhesions consist of oxides of zinc and partly magnesium. If these become too large, they lead to scoring in the cast bolt, and this in turn leads to poor quality rods after pressing. If these adhesions quickly come off again, then this is not a problem. However, if the magnesium content is too high, these adhere tightly to the casting mold, which results in scoring and cracks.

[0106] It is believed that the high friction between the underside of the billet and the mold in combination with Mg contents from 0.2% by weight significantly affects the billet quality locally.

[0107] Example images are shown in FIGS. 5-8 with increasing Mg content and the resulting bolt cracks (the images show different bolts with increasing Mg content steps, as described above):

[0108] A series of strand cooling optimizations increased the critical Mg content before cracks occurred. However, increasing the content to 0.5 wt-% and higher still resulted in poor billet surface quality.

[0109] The poor bolt surfaces lead to defective semi-finished products due to oxide inclusions in the downstream process steps (extrusion and drawing) and must therefore be avoided. For this reason, an Mg content of less than 0.5 wt % is considered advantageous.

[0110] Therefore, through the proposed addition of from 0.1 to less than 0.5% by weight Mg to a lead-free and antimony-free brass alloy, considerably improved chip breaking can be achieved. The proposed brass alloy is notable, moreover, for little hot embrittlement. It may be processed by hot forming, particularly in a continuous casting process.

Claims

1. A lead-free and antimony-free brass alloy, consisting of:from 56 to 66% by weight of Cu;from 0.1 to less than 0.5% by weight of Mg;less than 0.1% by weight of Pb;from 40 to 42.5% by weight of Zn; andunavoidable impurities.

2. The lead-free and antimony-free brass alloy according to claim 1, which consists of:from 57 to less than 60% by weight of Cu;from 0.1 to less than 0.5% by weight of Mg;less than 0.1% by weight of Pb;from 40 to 42.5% by weight of Zn; andunavoidable impurities.

3. The lead-free and antimony-free brass alloy according to claim 2, which consists of:from 57.5 to 58.5% by weight of Cu;from 0.1 to less than 0.5% by weight of Mg;less than 0.1% by weight of Pb;from 40 to 42.5% by weight of Zn; andunavoidable impurities.

4. The lead-free and antimony-free brass alloy according to claim 1, which consists of:from 56 to 66% by weight of Cu;less than 0.5% by weight of Mg;less than 0.1% by weight of Pb;from 40 to 42.5% by weight of Zn; andunavoidable impurities.

5. The lead-free and antimony-free brass alloy according to claim 1, which consists of:from 56 to 66% by weight of Cu;from 0.1 to less than 0.5% by weight of Mg;from 0.05% to 0.09% by weight of Pb;from 40 to 42.5% by weight of Zn; andunavoidable impurities.

6. A lead-free and antimony-free brass alloy, consisting of:from 56 to 66% by weight of Cu;from 0.1 to less than 0.5% by weight of Mg;less than 0.1% by weight of Pb;less than 0.15% by weight of As;less than 0.15% by weight of P;less than 0.1% by weight of Al;less than 0.1% by weight of Sn;less than 0.005% by weight of In;from 40 to 42.5% by weight of Zn; andunavoidable impurities.

7. A lead-free and antimony-free brass alloy, which consists of:from 56 to 66% by weight of Cu;from 0.1 to less than 0.5% by weight of Mg;from 40 to 42.5% by weight of Zn; andunavoidable impurities.

8. A lead-free and antimony-free brass alloy, comprising:from 56 to 66% by weight of Cu;from 0.1 to less than 0.5% by weight of Mg;less than 0.1% by weight of Pb;a balance by weight of Zn; andunavoidable impurities.

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