Lead-free brass alloy and machine element produced therefrom

Abstract

The invention relates to a lead-free brass alloy, containing 55 to 59 wt % Cu, 2.0 to 2.5 wt % Mn, 0.65 to 1.5 wt % Si, less than 0.1 wt % Pb, and a remainder of Zn and unavoidable impurities. The invention additionally relates to a machine element which is produced from the lead-free brass alloy.

Description

[0001] Lead-free brass alloy and machine element made therefrom

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

[0003] In the past, lead was added to brass alloys in quantities of up to 4 wt% to improve machining. However, the addition of lead will be severely restricted in the future due to foreseeable legal requirements.

[0004] There is therefore a need for a lead-free brass alloy. Such alloys are known per se; reference is made, for example, to the following publications: EP 2 009 122 A1, EP 3272 888 A1, WO 2016 / 045770 A1 and

[0005] EP 3269 835 A1. However, the absence of lead impairs the machinability of such brass alloys.

[0006] The invention is therefore based on the object of providing a lead-free brass alloy which is easy to machine.

[0007] To solve this problem, a lead-free brass alloy having the features of claim 1 is provided.

[0008] The brass alloy according to the invention contains: 55 to 59 wt% Cu, 2.0 to 2.5 wt% Mn, 0.65 to 1.5 wt% Si, less than 0.1 wt% Pb, balance Zn and unavoidable impurities.

[0009] The brass alloy according to the invention contains less than 0.1 wt% lead and is therefore considered lead-free. It has been shown that the brass alloy according to the invention exhibits satisfactory machinability despite its low lead content of less than 0.1 wt%. In particular, no undesirable long spiral chips form during machining. Furthermore, the friction properties of the lead-free brass alloy according to the invention are comparable to those of a lead-containing brass alloy. An advantageous embodiment of the invention provides that the ratio of the weight percentages of Mn to Si conforms to the inequality 2.0 < Mn / Si < 2.9. It has been found that this ratio between manganese and silicon leads to an optimal chemical composition and the formation of manganese silicides.

[0010] In the lead-free brass alloy according to the invention, the copper equivalent is 53 to 66%.

[0011] Preferably, the lead-free brass alloy according to the invention contains less than 0.2 wt% Fe.

[0012] Preferably, the lead-free brass alloy according to the invention contains less than 0.5 wt% Sn.

[0013] The lead-free brass alloy according to the invention preferably contains 1.5 to 2.6 wt% Ni.

[0014] The following composition of the lead-free brass alloy according to the invention is particularly preferred: 57 wt% Cu, 2.3 wt% Mn, 1.0 wt% Si, 0.1 wt% Fe, 0.1 wt% Sn, 2.0 wt% Ni, less than 0.1 wt% Pb, balance Zn and unavoidable impurities.

[0015] A preferred embodiment of the invention provides that the lead-free brass alloy contains less than 0.1 wt% Al.

[0016] The lead-free brass alloy may also contain less than 0.25 wt% Cr and / or less than 0.25 wt% Ti and / or less than 0.25 wt% Co.

[0017] The invention also relates to a machine element made from the lead-free brass alloy according to the invention. Due to its good friction properties, the lead-free brass alloy is ideally suited for the production of machine elements used with a lubricant. The invention is explained below using an exemplary embodiment with reference to the drawings. The drawings are schematic representations and show:

[0018] Fig. 1 shows a chip pattern produced by machining a reference alloy; and

[0019] Fig. 2 shows a chip pattern produced by machining a lead-free brass alloy according to the invention.

[0020] An embodiment of the lead-free brass alloy has the following composition: 57 wt% Cu; 2.3 wt% Mn; 1.0 wt% Si; 0.1 wt% Fe; 0.1 wt% Sn; 2.0 wt% Ni; less than 0.1 wt% Pb; balance Zn and unavoidable impurities.

[0021] The copper equivalent (CuEq) of the lead-free brass alloy is between 53% and 66% and can be calculated based on the alloy components as follows:

[0022] 1) If: Sif r i = Si 3.26 - (Fe+Mn) < 0 and Sif re i2 = Si 3.26 - (Fe+Mn+Ni) < 0 then

[0023] Cu

[0024] CuEq =

[0025] 2) If Sifrei = Si 3.26 - (Fe+Mn) > 0 and Sif re i2 = Si 3.26 - (Fe+Mn+Ni) < 0

[0026] Cu_

[0027] 100 — Fe — Mn — Si — Ni + [|Si - e i2 | x (-1.9)] 100

[0028] 3) If Sifrei = Si 3.26 - (Fe+Mn) > 0 and Sif rei2 = Si 3.26 - (Fe+Mn+Ni) > 0

[0029] Cu

[0030] CuAq =

[0031] The abbreviations mean:

[0032] Cu: wt% copper Fe: wt% iron

[0033] Mn: wt% manganese

[0034] Si: wt% silicon

[0035] Ni: wt% nickel

[0036] The lead-free brass alloy can be processed into semi-finished products such as plates, tubes, or rods, from which machine elements can be manufactured that are used with a lubricant. One example is friction-loaded components of axial piston pumps. The lead-free brass alloy contains manganese silicides, which are responsible for its good friction properties.

[0037] The machinability of the lead-free brass alloy is compared with a reference alloy. The following table shows the compositions of the lead-free brass alloy and the reference alloy:

[0038] In the machining test, a CNMG120404FP HC5010 indexable insert was used. The speed was 3,000 rpm, the feed per revolution was 0.25 mm, and the cutting depth was 1.25 mm. Figure 1 shows the chip pattern of the lead-containing reference alloy. Figure 2 shows the chip pattern of the lead-free brass alloy in comparison. It can be seen that both alloys produce chips of approximately the same size and type. The chip quality of the lead-free brass alloy is therefore acceptable.

[0039] The coefficient of friction was determined for both alloys in identical tests. It was found that both the lead-free brass alloy and the lead-containing reference alloy have almost identical coefficients of friction. The coefficient of friction is approximately 0.012. These tests showed that the lead-free brass alloy can be used without restrictions as a replacement for the lead-containing reference alloy.

[0040] The lead-free brass alloy can be used to manufacture various machine components, particularly those subject to friction and used with a lubricant. Examples include components of axial piston pumps and sliding shoes.

Claims

Patent claims Lead-free brass alloy containing: 55 to 59 wt% Cu, 2.0 to 2.5 wt% Mn, 0.65 to 1.5 wt% Si, < 0.1 wt% Pb, The balance is Zn and unavoidable impurities. A lead-free brass alloy according to claim 1, wherein the ratio of the weight percentages of Mn to Si corresponds to the following inequality: 2.0 < Mn / Si < 2.

9. Lead-free brass alloy according to claim 1 or 2, wherein the copper equivalent is between 53 and 66%. Lead-free brass alloy according to any one of the preceding claims, wherein less than 0.2 wt% Fe is contained. Lead-free brass alloy according to any one of the preceding claims, wherein less than 0.5 wt% Sn is contained. Lead-free brass alloy according to any one of the preceding claims, wherein 1.5 to 2.6 wt% Ni is contained. Lead-free brass alloy according to any one of the preceding claims, containing: 57 wt% Cu, 2.3 wt% Mn, 1.0 wt% Si, 0.1 wt% Fe, 0.1 wt% Sn, 2.0 wt% Ni, < 0.1 wt% Pb, The remainder is Zn and unavoidable impurities. Lead-free brass alloy according to one of the preceding claims, containing less than 0.1 wt.% Al. Lead-free brass alloy according to one of the preceding claims, containing less than 0.25 wt.% Cr and / or less than 0.25 wt.% Ti and / or less than 0.25 wt.% Co. A machine element made from a lead-free brass alloy according to one of claims 1 to 9.

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