Lead-free brass alloy and bearing component produced therefrom

Abstract

The invention relates to a lead-free brass alloy, containing 59 to 62 wt % Cu, 2.0 to 2.5 wt % Mn, 0.5 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 bearing element or a bushing which is produced from the lead-free brass alloy.

Description

[0001] Lead-free brass alloy and bearing component 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 and has good frictional wear resistance.

[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: 59 to 62 wt% Cu, 2.0 to 2.5 wt% Mn, 0.5 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 2.2 < Mn / Si < 3.2. 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, it is particularly preferred that manganese silicides are arranged parallel on a functional surface. This increases the proportion of manganese silicides on the functional surface and improves the friction properties. The parallel arrangement of the manganese silicides is achieved through a manufacturing process that involves hot forming.

[0011] Preferably, the lead-free brass alloy according to the invention contains less than 0.1 wt% Fe, preferably 0.07 wt% Fe.

[0012] The lead-free brass alloy according to the invention preferably contains less than 0.5 wt% Sn, preferably 0.07 wt% Sn.

[0013] The following composition of the lead-free brass alloy according to the invention is particularly preferred: 61.2 wt% Cu, 2.3 wt% Mn, 0.8 wt% Si, 0.07 wt% Fe, 0.07 wt% Sn, less than 0.1 wt% Pb, balance Zn and unavoidable impurities.

[0014] The lead-free brass alloy according to the invention preferably contains less than 0.2 wt% Ni, preferably 0.02 wt% to less than 0.2 wt% Ni.

[0015] A preferred embodiment of the invention provides that the lead-free brass alloy contains less than 0.1 wt% AI, preferably 0.01 wt% to less than 0.1 wt% AI.

[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 bearing element or bushing 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 bearing elements and bushings.

[0018] The invention is explained below using an exemplary embodiment with reference to the drawings. The drawings are schematic representations and show:

[0019] Fig. 1 shows a functional surface of a lead-free brass alloy according to the invention;

[0020] Fig. 2 shows a chip pattern produced by machining a reference alloy; and

[0021] Fig. 3 shows a chip pattern produced by machining a lead-free brass alloy according to the invention.

[0022] An embodiment of the lead-free brass alloy has the following composition: 61.2 wt% Cu, 2.3 wt% Mn, 0.8 wt% Si, 0.07 wt% Fe, 0.07 wt% Sn, less than 0.1 wt% Pb, balance Zn and unavoidable impurities.

[0023] The lead-free brass alloy can be processed into semi-finished products such as plates, tubes, or rods, from which components such as bearing elements, bushings, or the like can be manufactured. Fig. 1 shows a functional surface of a semi-finished product made from the lead-free brass alloy. It can be seen that parallel manganese silicides are arranged on the functional surface. The comparatively high surface area of ​​manganese silicides on the functional surface improves its friction properties.

[0024] 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:

[0025] 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. Fig. 2 shows the chip pattern of the lead-free brass alloy, while Fig. 3 shows a comparison with the chip pattern of the lead-containing reference alloy. 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. The surface roughness was measured for both alloys. This was Ra = 5.32 pm for the lead-free brass alloy and Ra = 5.61 pm for the reference alloy. The lead-free brass alloy therefore has a comparable surface roughness to the lead-containing reference alloy.

[0026] 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.

[0027] These tests have shown that the lead-free brass alloy can be used without restrictions as a replacement for the lead-containing reference alloy.

[0028] The lead-free brass alloy can be used, for example, for the production of bearing elements, bushings or other components where relative movement occurs between two components.

Claims

Patent claims 1. Lead-free brass alloy containing: 59 to 62 wt% Cu, 2.0 to 2.5 wt% Mn, 0.5 to 1.5 wt% Si, < 0.1 wt% Pb, Rest Zn and unavoidable impurities.

2. Lead-free brass alloy according to claim 1, wherein the ratio of the weight percentage of Mn to Si corresponds to the following inequality: 2.2 < Mn / Si < 3.

2.

3. Lead-free brass alloy according to claim 1 or 2, wherein manganese silicides are arranged in parallel on a functional surface.

4. Lead-free brass alloy according to one of the preceding claims, containing less than 0.1 wt% Fe, preferably 0.07 wt% Fe.

5. Lead-free brass alloy according to one of the preceding claims, containing less than 0.5 wt% Sn, preferably 0.07 wt% Sn.

6. Lead-free brass alloy according to one of the preceding claims, containing: 61.2 wt% Cu, 2.3 wt% Mn, 0.8 wt% Si, 0.07 wt% Fe, 0.07 wt% Sn, < 0.1 wt% Pb, Rest Zn and unavoidable impurities.

7. Lead-free brass alloy according to one of the preceding claims, wherein less than 0.2 wt% Ni, preferably 0.02 wt% to less than 0.2 wt% Ni, is contained.

8. Lead-free brass alloy according to one of the preceding claims, wherein less than 0.1 wt% Al, preferably 0.01 wt% to less than 0.1 wt% Al is contained.

9. 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.

10. Bearing element or bushing made of a lead-free brass alloy according to any one of claims 1 to 9.

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