LEAD- AND ANTIMONE-FREE BRASS ALLOY

Description

[0001] The invention relates to a lead- and antimony-free brass alloy.

[0002] In the past, lead (Pb) was added to brass alloys at levels of up to 4 wt.% to improve their machinability. The addition of Pb is no longer permitted due to legal regulations.

[0003] It was found that the addition of Pb could be replaced by the addition of Bi. However, it was shown that the addition of Bi leads to hot embrittlement of the brass alloy. Such brass alloys can only be hot-formed to a limited extent. Consequently, these brass alloys are not used for pressed parts.

[0004] CN 101 161 836 A; JP H06 179 932 A; LEE DONG-BOK ET AL: "The effect of small additions of Zr, Cr, Mg, Al, and Si on the oxidation of 6:4 brass", METALS AND MATERIALS INTERNATIONAL, Vol. 8, No. 3, May 31, 2002 (2002-05-31), pages 327-332, XP093005172, Seoul and HARUHIKO ATSUMI ET AL: "Fabrication and properties of high-strength extruded brass using elemental mixture of Cu40% Zn alloy powder and Mg particle", MATERIALS CHEMISTRY AND PHYSICS, ELSEVIER SA, SWITZERLAND, TAIWAN, REPUBLIC OF CHINA, Vol. 135, No. 2, May 6, 2012 (2012-05-06), pages 554-562, XP028414791 and ADINEH MORTEZA ET AL: "Microstructure, mechanical properties and machinability of Cu-Zn-Mg and Cu-Zn-Sb brass alloys", MATERIALS SCIENCE AND TECHNOLOGY, Vol. 35, No. 12, June 19, 2019 (2019-06-19), pages 1504-1514, XP093005147, each disclose Cu-Zn alloys with a Cu content of 55 to 66% and a Mg content of 0.1 to 0.5%. These documents make no mention of the In content.

[0005] JP H08 176 707 A discloses a Cu-Zn alloy with an In content below the detection limit. The document makes no mention of the As, Al, or Sn content.

[0006] WO 2020 / 261603 A1 describes a copper alloy containing more than 61.0% and less than 65.0% Cu, more than 1.0% and less than 1.5% Si, 0.003% to less than 0.20% Pb, and more than 0.003% and less than 0.19% P. The remainder consists of Zn and unavoidable impurities. The total content of Fe, Mn, Co, and Cr is less than 0.40%, and the total content of Sn and Al is less than 0.40%.

[0007] From DE 10 2013 107 011 A1 a method for coating a Cu long product produced from a Cu material with a metallic protective layer is known, wherein the Cu material contains numerous elements.

[0008] EP 3 320 122 B1 discloses a brass alloy to which neither Pb nor Bi is added. To improve machinability, it is proposed to add 0.005 to 1.0 wt.% In to the brass alloy. While the proposed addition of In does improve machinability, relatively long spiral chips are formed during machining, which can lead to blockages during chip removal and tool breakage.

[0009] EP 2 913 415 A1 discloses a further lead- and bismuth-free brass alloy, which also contains no silicon. The known alloy contains 60 to 65 wt.% Cu and 0.01 to 0.15 wt.% Sb.

[0010] The addition of sulfur leads to hot embrittlement. Alternatively, EP 2 913 415 A1 proposes an addition of 0.005 to 0.3 wt% phosphorus. The proposed addition of phosphorus makes processing in continuous casting more difficult.

[0011] EP 2 467 507 B1 discloses a lead-free brass alloy containing Fe, Ni and Sn.

[0012] From EP 2 133 437 B1, a lead-free free-casting brass alloy is known which contains 0.6 to 2.5 wt.% Mg and 0.15 to 0.4 wt.% P. The addition of P makes processing in continuous casting more difficult.

[0013] The object of the invention is to eliminate the disadvantages of the prior art. In particular, it aims to provide a lead- and antimony-free brass alloy with improved machinability. A further objective of the invention is that the brass alloy exhibits low hot embrittlement, so that it can be processed by hot forming.

[0014] This problem is solved by the features of claim 1. Advantageous embodiments result from the features of the dependent claims.

[0015] A lead- and antimony-free brass alloy according to claim 1 is proposed.

[0016] In the context of this description, [%] refers to weight percent.

[0017] Surprisingly, it has been shown that the addition of 0.1 to 1.5% Mg, as proposed in the invention, allows the Pb content to be reduced to less than 0.1% without the undesirable formation of long, spiral chips during machining. The proposed brass alloy is characterized not only by improved chip breakage but also by low hot embrittlement. It can be processed by hot forming.

[0018] According to the invention, a "lead- and antimony-free brass alloy" is understood to be an alloy which contains less than 0.1% Pb and less than 0.001% Sb.

[0019] The alloy contains 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 β-solid solution. As improves the alloy's corrosion resistance, particularly by counteracting dezincification. The addition of P improves the alloy's machinability.

[0020] According to a further advantageous embodiment, the alloy contains 57% to less than 60%, preferably 57.5% to 58.5% Cu. The proposed alloy is more cost-effective due to the relatively lower Cu content.

[0021] In a further formulation, the material contains more than 0.5% Mg. The proposed Mg content contributes to improved machinability.

[0022] The lead content is appropriately in the range of 0.05 to 0.09%. The inhalant content is less than 0.005%.

[0023] Finally, according to an advantageous embodiment, it is proposed that the Zn content be between 40 and 42.5%. An alloy with the proposed Zn content exhibits good machinability.

[0024] Furthermore, the proposed lead- and antimony-free brass alloy allows for good processability in continuous casting.

[0025] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. The drawings show: Fig. 1 shows a chip pattern after longitudinal turning of a first example alloy, Fig. 2 shows a chip pattern after longitudinal turning of a second example alloy, Fig. 3 shows a chip pattern after longitudinal turning of a third example alloy and Fig. 4 shows a chip pattern after longitudinal turning of a fourth example alloy.

[0026] The chip patterns according to the Fig. 1 bis 4 Each part was manufactured by longitudinal turning of alloys at a speed of 850 rpm. An indexable insert with the identification KNMX160405-R8IC907 was used. The part in the Fig. 1 bis 4 The displayed scale is 5 mm in each case.

[0027] Fig. 1 This shows a chip pattern after longitudinal turning of a first example alloy. The first example alloy is a reference alloy. It contains 58% Cu and 42% Zn, meaning it contains no added Mg.

[0028] As from Fig. 1 As can be seen, long spiral chips are formed during the longitudinal turning of the example alloy 1. Such spiral chips are undesirable in machining. They can lead to blockages in the chip removal process and to tool breakage.

[0029] Fig. 2 Figure 1 shows a chip pattern after longitudinal turning of a second example alloy. The second example alloy contains 58% Cu, 41.5% Zn, and 0.5% Mg. It is evident that the chips produced during longitudinal turning are shorter than those shown in Figure 2. Fig. 1 shown shavings.

[0030] Fig. 3 The figure shows a chip pattern after longitudinal turning of a third example alloy. The third example alloy consists of 58% Cu, 41% Zn, and 1% Mg. It is clearly visible that the produced chips are again shorter than the chips produced by longitudinal turning of the second example alloy.

[0031] Fig. 4 The figure shows the chip formation after longitudinal turning of a fourth example alloy. This fourth example alloy consists of 58% Cu, 40.5% Zn, and 1.5% Mg. The chips produced when turning this fourth example alloy are even smaller than those produced by longitudinal turning of the third example alloy.

[0032] The proposed addition of 0.1 to 1.5% Mg to a lead- and antimony-free brass alloy can therefore achieve significantly improved chip breaking. Furthermore, the proposed brass alloy is characterized by low hot embrittlement. It can be processed by hot forming, particularly by continuous casting.

Claims

1. Lead- and antimony-free brass alloy containing (in wt%) 56 to 66% Cu, 0.1 to 1.5% Mg, less than 0.1% Pb, less than 0.001% Sb, less than 0.15% As, less than 0.15% P, less than 0.1% Al, less than 0.1% Sn, less than 0.005% In, balance Zn and also unavoidable impurities.

2. Lead- and antimony-free brass alloy according to any of the preceding claims, containing 57 to less than 60%, preferably 57.5 to 58.5% Cu.

3. Lead- and antimony-free brass alloy according to any of the preceding claims, containing more than 0.5% Mg.

4. Lead- and antimony-free brass alloy according to any of the preceding claims, containing 0.05 to 0.09% Pb.

5. Lead- and antimony-free brass alloy according to any of the preceding claims, containing 40 to 42.5% Zn.