Lead-free brass alloys and bearing parts made from them

Abstract

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 balance being Zn, and unavoidable impurities. Furthermore, a bearing part or bushing manufactured from the lead-free brass alloy is proposed.

Description

[Technical Field]

[0001] The present invention relates to lead-free brass alloys. [Background technology]

[0002] Traditionally, the workability of brass alloys has been improved by adding up to 4% by weight of Pb, but in the future, legal regulations are expected to impose strict limits on lead addition.

[0003] Therefore, there is a demand for lead-free brass alloys. Lead-free brass alloys are known, including those disclosed in European Patent Application Publication Nos. 2009122 A1, 3272888 A1, WO 2016 / 045770 A1, and 3269835 A1. However, lead-free brass alloys have a negative effect on their workability. Summary of the Invention [Problem to be solved by the invention]

[0004] It is therefore an object of the present invention to provide a lead-free brass alloy that has both good machinability and good friction and wear resistance. [Means for solving the problem]

[0005] The brass alloy of the present invention is composed of 59% by weight to 62% by weight of Cu, 2.0% by weight to 2.5% by weight of Mn, 0.5% by weight to 1.5% by weight of Si, less than 0.1% by weight of Pb, the balance being Zn, and unavoidable impurities. [Effects of the Invention]

[0006] The brass alloys of the present invention contain less than 0.1 wt. % Pb and are therefore considered lead-free. It has been found that the brass alloys of the present invention exhibit satisfactory machinability despite their low lead content of less than 0.1 wt. %. In particular, machining does not result in the formation of unwanted long chips. Furthermore, the frictional properties of the lead-free brass alloys of the present invention are comparable to those of lead-containing brass alloys. [Brief explanation of the drawings]

[0007] [Figure 1] 1 shows the functional surface of the lead-free brass alloy of the present invention. [Figure 2] The shape of chips generated when machining the reference alloy is shown. [Figure 3] 1 shows the shape of chips produced when machining the lead-free brass alloy of the present invention. Detailed Description of the Invention

[0008] In one preferred embodiment of the present invention, the weight percent ratio of Mn to Si corresponds to the inequality 2.2≦Mn / Si≦3.2, which has been found to result in an optimal chemical composition and the formation of manganese silicide.

[0009] In the lead-free brass alloy of the present invention, it is particularly preferred to arrange the manganese silicide in parallel on the functional surface. This increases the proportion of manganese silicide in the functional surface and improves friction characteristics. The parallel arrangement of the manganese silicide is achieved through a manufacturing process that includes a hot forming operation.

[0010] In the lead-free brass alloy of the present invention, the Fe content is preferably less than 0.1 wt %, more preferably less than 0.07 wt %.

[0011] In the lead-free brass alloy of the present invention, the Sn content is preferably less than 0.5 wt %, more preferably less than 0.07 wt %.

[0012] The lead-free brass alloy of the present invention preferably has the following composition. It consists of 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 balance being Zn, and unavoidable impurities.

[0013] In the lead-free brass alloy of the present invention, the Ni content is preferably less than 0.2 wt %, and more preferably 0.02 to 0.2 wt %.

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

[0015] The lead-free brass alloy of the present invention may contain less than 0.25 wt% Cr, and / or less than 0.25 wt% Ti, and / or less than 0.25 wt% Co.

[0016] The present invention further relates to bearing components or bushings made from the lead-free brass alloy of the present invention. Due to its excellent friction properties, the lead-free brass alloy is suitable for making bearing components and bushings. [Example]

[0017] One example of a lead-free brass alloy has the following composition: It consists of 61.2 wt% Cu, 2.3 wt% Mn, 0.8 wt% Si, 0.07 wt% Fe, 0.07 wt% Sn, and less than 0.1 wt% Pb, the balance being Zn, and unavoidable impurities.

[0018] Lead-free brass alloys can be processed into intermediates such as plates, cylinders, and rods, from which components such as bearings and bushings can be manufactured. Figure 1 shows the functional surface of an intermediate manufactured from lead-free brass alloys. The figure shows that manganese silicide is arranged parallel to the functional surface. A relatively high proportion of manganese silicide on the functional surface improves friction properties.

[0019] The machinability of lead-free brass alloys is compared with that of reference alloys. The table below shows the compositions of lead-free brass alloys and reference alloys.

[0020] [Table 1]

[0021] Machining tests were conducted using CNMG120404FP HC5010 type indexable cutting inserts at a rotational speed of 3000 rpm, a rotational speed of 0.25 mm, and a cutting depth of 1.25 mm. Figure 2 shows the chip shape of the lead-free brass alloy. Figure 3, in comparison, shows the chip shape of the lead-containing reference alloy. It can be seen that the two alloys produced chips of approximately the same size and shape. Therefore, the chip quality of the lead-free brass alloy is satisfactory. The surface roughness of the two alloys was measured; Ra = 5.32 μm for the lead-free brass alloy and Ra = 5.61 μm for the reference alloy. Therefore, the lead-free brass alloy has a surface roughness equivalent to that of the lead-containing reference alloy.

[0022] The coefficient of friction for both alloys was determined using the same test and found to be virtually identical for both the lead-free brass alloy and the lead-containing reference alloy, approximately 0.012.

[0023] These tests demonstrated that lead-free brass alloys can be used without restriction as replacements for lead-containing reference alloys.

[0024] Lead-free brass alloys can be used, for example, to manufacture bearing components, bushings, or other components that operate in conjunction between two components.

Claims

1. 59-62% by weight of Cu, 2.0–2.5% by weight of Mn, 0.5 to 1.5% by weight of Si, Pb less than 0.1% by weight, A lead-free brass alloy consisting of the remainder being Zn and unavoidable impurities.

2. The weight percentage ratio of Mn to Si is given by the following inequality: 2.2 ≦ Mn / Si ≦ 3.2 The lead-free brass alloy according to claim 1, corresponding to the one described in claim 1.

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

4. The lead-free brass alloy according to claim 1 or 2, comprising less than 0.1% by weight, preferably 0.07% by weight, of Fe.

5. The lead-free brass alloy according to claim 1 or 2, comprising less than 0.5% by weight, preferably 0.07% by weight, of Sn.

6. 61.2% by weight of Cu, 2.3% by weight of Mn, 0.8 wt% Si, 0.07% by weight of Fe, 0.07% by weight of Sn, Pb less than 0.1% by weight, The lead-free brass alloy according to claim 1 or 2, comprising the remainder Zn and unavoidable impurities.

7. The lead-free brass alloy according to claim 1 or 2, comprising less than 0.2% by weight of Ni, preferably 0.02% by weight or more and less than 0.2% by weight.

8. The lead-free brass alloy according to claim 1 or 2, comprising less than 0.1% by weight of Al, preferably 0.01% by weight or more and less than 0.1% by weight.

9. The lead-free brass alloy according to claim 1 or 2, wherein the Cr content is less than 0.25% by weight, and / or the Ti content is less than 0.25% by weight, and / or the Co content is less than 0.25% by weight.

10. A bearing component or bushing manufactured from the lead-free brass alloy described in claim 1 or 2.

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