Lead-free brass alloys and machine parts made from them

Abstract

A lead-free brass alloy comprising 55% by weight to 59% by weight of Cu, 2.0% by weight to 2.5% by weight of Mn, 0.65% by weight to 1.5% by weight of Si, less than 0.1% by weight of Pb, the balance being Zn, and unavoidable impurities. Furthermore, a mechanical part manufactured from the lead-free brass alloy is proposed.

Description

[Technical Field]

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

[0002] Traditionally, the machinability 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 need for lead-free brass alloys. Lead-free brass alloys are known, including those disclosed in European Patent Applications 2009122 A1, 3272888 A1, WO 2016 / 045770 A1, and 3269835 A1. However, lead-free brass alloys have a negative impact on their machinability. 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.

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

[0006] The brass alloy of the present invention is composed of 55% by weight to 59% by weight of Cu, 2.0% by weight to 2.5% by weight of Mn, 0.65% 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]

[0007] 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]

[0008] [Figure 1] -The shape of chips generated when machining the reference alloy is shown. [Figure 2] 3 shows the shape of chips produced when machining the lead-free brass alloy of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are schematic diagrams, and the following points should be noted.

[0010] In one preferred embodiment of the present invention, the weight percent ratio of Mn to Si corresponds to the inequality 2.2≦Mn / Si≦2.9, which has been found to result in an optimal chemical composition and the formation of manganese silicide.

[0011] In the lead-free brass alloy of the present invention, the copper equivalent is 53 to 66%.

[0012] In the lead-free brass alloy of the present invention, the Fe content is preferably less than 0.2 wt %.

[0013] In the lead-free brass alloy of the present invention, the Sn content is preferably less than 0.5 wt %.

[0014] In the lead-free brass alloy of the present invention, the Ni content is preferably 1.5 to 2.6 wt %.

[0015] The lead-free brass alloy of the present invention preferably has the following composition. It consists of 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, the balance being Zn, and unavoidable impurities.

[0016] In one preferred embodiment of the present invention, the lead-free brass alloy contains less than 0.1 wt. % Al.

[0017] 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.

[0018] The present invention further relates to a machine part manufactured from the lead-free brass alloy of the present invention. Due to its excellent friction properties, the lead-free brass alloy is suitable for manufacturing machine parts to be used in combination with lubricating oils. [Example]

[0019] One example of a lead-free brass alloy has the following composition: It consists of 57 wt% Cu, 2.3 wt% Mn, 1.0 wt% Si, 0.1 wt% Fe, 0.1 wt% Sn, 2.0 wt% Ni, and less than 0.1 wt% Pb, the balance being Zn, and unavoidable impurities.

[0020] The copper equivalent (CuEq) of lead-free brass alloys ranges from 53 to 66%, and is calculated based on the alloy composition as follows: (1)Si free =Si·3.26-(Fe+Mn)<0 and Si free2 =Si·3.26-(Fe+Mn+Ni)<0,

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[0021] The abbreviations in the formula have the following meanings: Cu: weight percent of copper Fe: weight percent of iron Mn: manganese weight percent Si: weight percent of silicon Ni: weight percent of nickel

[0022] Lead-free brass alloys can be processed into intermediate shapes such as plates, cylinders, and rods, from which mechanical parts can be manufactured that are used in conjunction with lubricants. One example is axial piston pump parts that are subject to friction. Lead-free brass alloys have good friction properties due to their manganese silicide content.

[0023] 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. [Table 1]

[0024] The machining tests were carried out using CNMG120404FP HC5010 type indexable cutting inserts at a rotation speed of 3000 rpm, a rotational speed of 0.25 mm, and a cutting depth of 1.25 mm. Figure 1 shows the chip shape of the alloy containing the reference amount of lead. In comparison, Figure 2 shows the chip shape of the lead-free brass alloy. It is clear that the two alloys produce chips of approximately the same size and shape, and therefore the chip quality of the lead-free brass alloy is quite satisfactory.

[0025] 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.

[0026] These tests demonstrated that lead-free brass alloys can be used without restriction as replacements for lead-containing reference alloys.

[0027] Lead-free brass alloys can be used to manufacture a variety of machine parts, especially those that are subject to friction and lubrication, such as axial piston pumps, pump components, or sliding blocks.

Claims

1. Cu, 55% by weight or more and 59% by weight or less 2.0% by weight or more and 2.5% by weight or less of Mn, Si, 0.65% by weight or more and 1.5% by weight or less 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: 2.0 ≤ Mn / Si ≤ 2.9 The lead-free brass alloy according to claim 1, corresponding to the one described in claim 1.

3. A lead-free brass alloy according to claim 1 or 2, wherein the copper equivalent is 53% or more and 66% or less.

4. A lead-free brass alloy according to claim 1 or 2, comprising less than 0.2% by weight of Fe.

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

6. A lead-free brass alloy according to claim 1 or 2, comprising 1.5% by weight or more and 2.6% by weight or less of Ni.

7. 57% by weight of Cu, 2.3% by weight of Mn, 1.0 wt% Si, 0.1% by weight of Fe, 0.1% by weight of Sn, 2.0% by weight of Ni, 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.

8. A lead-free brass alloy according to claim 1 or 2, containing less than 0.1% by weight of Al.

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

10. A machine part manufactured from the lead-free brass alloy described in claim 1 or 2.

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