Lead-free brass alloy and bearing member made therefrom

Abstract

The present invention relates to a lead-free brass alloy comprising: 59 to 62% by weight of Cu, 2.0 to 2.5% by weight of Mn, 0.5 to 1.5% by weight of Si, less than 0.1% by weight of Pb, the remainder being Zn and unavoidable impurities. The invention further relates to a bearing element or bushing, which is produced from a lead-free brass alloy.

Description

Technical Field

[0001] The invention relates to a lead-free brass alloy. Background Art

[0002] In the past, up to 4% by weight of lead was added to improve the machinability of brass alloys. However, due to foreseeable legal regulations, the amount of lead added will be strictly limited in the future.

[0003] Therefore, a lead-free brass alloy is needed. Such alloys are known per se, for example, refer to the following documents: EP 2009 122 A1, EP 3 272 888 A1, WO 2016 / 045770 A1 and EP 3 269 835 A1. However, the lack of lead affects the cutting performance of such brass alloys. Summary of the invention

[0004] The object of the present invention is therefore to provide a lead-free brass alloy which is easy to cut and has good friction resistance.

[0005] To achieve this object, a lead-free brass alloy having the features of claim 1 is provided.

[0006] The brass alloy according to the present 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, and the balance is Zn and inevitable impurities.

[0007] The brass alloy according to the invention has less than 0.1% by weight of Pb and is therefore considered lead-free. It has been shown that, despite the small lead content of less than 0.1% by weight, the brass alloy according to the invention exhibits satisfactory cutting properties. In particular, no undesirable long spiral chips are formed during cutting. In addition, the tribological properties of the lead-free brass alloy according to the invention are comparable to those of lead-containing brass alloys.

[0008] An advantageous embodiment of the invention provides that the weight percentage ratio of Mn to Si satisfies the inequality 2.2≤Mn / Si≤3.2. It has been found that this ratio of manganese to silicon achieves an optimal chemical composition and leads to the formation of manganese silicide.

[0009] In the lead-free brass alloy according to the invention, it is particularly preferred that the manganese silicide is arranged in parallel on the functional surface. As a result, the proportion of manganese silicide on the functional surface is increased and the friction properties are improved. The parallel arrangement of the manganese silicide is achieved by a production process in which hot forming is performed.

[0010] Preferably, less than 0.1 wt. % Fe, preferably 0.07 wt. % Fe, is contained in the lead-free brass alloy according to the invention.

[0011] Preferably, less than 0.5 wt. % Sn, preferably 0.07 wt. % Sn, is contained in the lead-free brass alloy according to the invention.

[0012] 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, the remainder being Zn and unavoidable impurities.

[0013] Preferably, the lead-free brass alloy according to the present invention contains less than 0.2 wt. % Ni, preferably 0.02 wt. % to less than 0.2 wt. % Ni.

[0014] A preferred embodiment of the present invention provides that the lead-free brass alloy contains less than 0.1 wt % Al, preferably 0.01 wt % to less than 0.1 wt % Al.

[0015] It can also be provided that the lead-free brass alloy contains less than 0.25 wt. % Cr and / or less than 0.25 wt. % Ti and / or less than 0.25 wt. % Co.

[0016] Furthermore, the invention relates to a bearing element or a bushing which is produced from the lead-free brass alloy according to the invention. Due to their good tribological properties, lead-free brass alloys are optimally suitable for producing bearing elements and bushings.

[0017] The invention is explained below with the aid of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are schematic illustrations and in which:

[0019] Figure 1 The functional surface of the lead-free brass alloy according to the present invention is shown;

[0020] Figure 2 shows the chip pattern produced by cutting a control alloy; and

[0021] Figure 3 The chip pattern produced by cutting a lead-free brass alloy according to the present invention is shown. DETAILED DESCRIPTION

[0022] One example of a 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, and the balance being Zn and unavoidable impurities.

[0023] Lead-free brass alloys 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 then be produced. Figure 1 The functional surface of a semi-finished product made of a lead-free brass alloy is shown. It can be seen that parallel-arranged manganese silicides are located on the functional surface. The relatively high surface proportion of manganese silicide on the functional surface improves its friction properties.

[0024] The cutting performance of the lead-free brass alloy was compared with that of the control alloy. The compositions of the lead-free brass alloy and the control alloy are shown in the table below:

[0025]

[0026] In the cutting test, an indexable insert of the CNMG120404FP HC5010 type was used, the rotation speed was 3000 rpm, the feed per revolution was 0.25 mm, and the cutting depth was 1.25 mm. Figure 2 shows the chip pattern of a lead-free brass alloy, Figure 3 The chip pattern of the leaded control alloy is shown for comparison. It can be seen that the two alloys produce chips of approximately the same size and type. Therefore, the cutting quality of the lead-free brass alloy is normal. The surface roughness was measured for both alloys. In the lead-free brass alloy, Ra = 5.32 μm, while in the control alloy Ra = 5.61 μm. Therefore, the lead-free brass alloy has a comparable surface roughness to the leaded control alloy.

[0027] The coefficient of friction was determined for both alloys in the same test. It was found that the lead-free brass alloy and the lead-containing control alloy had almost the same coefficient of friction. The coefficient of friction was approximately 0.012.

[0028] These tests have demonstrated that lead-free brass alloys can be used as replacements for lead-containing control alloys without restriction.

[0029] Lead-free brass alloys can be used, for example, to produce bearing elements, bushings or other components in which a relative movement occurs between two components.

Claims

1. A lead-free brass alloy comprising: 59 to 62 wt% Cu, 2.0 to 2.5 wt.% Mn, 0.5 to 1.5 wt% Si, <0.1 wt% Pb, The balance is Zn and inevitable impurities.

2. The lead-free brass alloy according to claim 1, wherein the weight percentage ratio of Mn to Si satisfies the following inequality: 2.2≤Mn / Si≤3.

2.

3. The lead-free brass alloy according to claim 1 or 2, wherein the manganese silicide is arranged in parallel on the functional plane.

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

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

6. A lead-free brass alloy according to any one of the preceding claims, comprising: 61.2 wt% Cu, 2.3 wt% Mn, 0.8 wt% Si, 0.07 wt% Fe, 0.07 wt% Sn, <0.1 wt% Pb, The balance is Zn and inevitable impurities.

7. The lead-free brass alloy according to any one of the preceding claims, comprising less than 0.2 wt. % Ni, preferably 0.02 wt. % to less than 0.2 wt. % Ni.

8. The lead-free brass alloy according to any one of the preceding claims, comprising less than 0.1 wt% Al, preferably 0.01 wt% to less than 0.1 wt% Al.

9. The lead-free brass alloy according to any one of the preceding claims, comprising less than 0.25 wt. % Cr and / or less than 0.25 wt. % Ti and / or less than 0.25 wt. % Co.

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

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