Bearing bush for a plain bearing made of a copper-zinc alloy

Abstract

Bearing bush for a plain bearing made of a copper-zinc alloy, comprising 62.5 to 64.5% Cu, 2.7 to 3.5% Mn, 1.3 to 1.9% Al, 0.8 to 1.2% Si, 0.3 to 0.6% Fe, 0 to 1.0% Pb, 0 to 1.5% Ni, 0 to 0.2% Sn, the remainder Zn and unavoidable impurities, wherein intermetallic compounds contained in the structure in the as-cast state have a size of at most 150 µm, wherein the bearing bush has a machined surface.

Description

[0001] The invention relates to a bearing bush for a plain bearing made of a copper-zinc alloy.

[0002] DE 10 2007 063 643 A1 discloses a copper-zinc alloy which is characterized by high resistance to abrasive wear.

[0003] DE 10 2005 015 467 A1 discloses another copper-zinc alloy for use as a material for a plain bearing with a composition in the following range: Cu: 59 to 73%; Mn: 2.7 to 8.5%; Al: 1.5 to 6.3%; Si: 0.2 to 4%; Fe: 0.2 to 3%; Pb: 0 to 2%; Ni: 0 to 2%; Sn: 0 to 0.4%; Zn: remainder (all values ​​in weight percent). The alloy exhibits good temperature and wear resistance.

[0004] DE 10 2005 059 391 A1 relates to a synchronizer ring and a copper-zinc alloy for producing the synchronizer ring.

[0005] DE 2 159 482 A describes a special brass for the production of sheets, strips and the like.

[0006] US 8,388,228 B2 discloses a plain bearing for use in a turbocharger, made of a copper alloy with 25 to 45% Zn, 0.3 to 2.0% Si, 1.5 to 6.0% Mn (all values ​​in weight percent).

[0007] In practice, it has been shown that the aforementioned copper-zinc alloys are only suitable to a limited extent, especially for the production of bearing bushes for turbochargers. Such bearing bushes must be manufactured with a tolerance of a few µm. Such a tolerance cannot always be maintained with conventional copper-zinc alloys because the surface roughness of machined surfaces is sometimes too high.

[0008] The object of the invention is to eliminate the disadvantages of the prior art. In particular, it is intended to provide a bearing bush for a plain bearing made of a copper-zinc alloy that allows for production with reduced surface roughness.

[0009] This object is achieved by the features of patent claim 1. Advantageous embodiments of the invention emerge from the features of patent claims 2 and 3.

[0010] According to the invention, a bearing bush for a plain bearing made of a copper-zinc alloy is proposed, comprising 62.5 to 64.5% Cu, 2.7 to 3.5% Mn, 1.3 to 1.9% Al, 0.8 to 1.2% Si, 0.3 to 0.6% Fe, 0 to 1.0% Pb, 0 to 1.5% Ni, 0 to 0.2% Sn, the remainder Zn and unavoidable impurities, wherein intermetallic compounds contained in the structure in the as-cast state have a size of at most 150 µm, wherein the bearing bush has a machined surface.

[0011] All information in “%” refers to “percent by weight”.

[0012] The proposed copper-zinc alloy exhibits excellent temperature resistance. Surfaces produced by machining exhibit significantly reduced surface roughness. The proposed copper-zinc alloy is particularly well suited for the production of bearing bushes, especially bearing bushes for turbochargers. The copper-zinc alloy can be processed by extrusion, drawing, casting, and cold and hot forming, e.g., extrusion, drawing, and stress relief annealing.

[0013] The copper-zinc alloy may contain 64.2% Cu, 2.0% Mn, 1.8% Al, 1.3% Si, 0.8% Fe, 0.8% Ni, balance Zn and unavoidable impurities.

[0014] In a particularly preferred embodiment, the alloying components Pb and / or Sn are omitted.

[0015] The copper-zinc alloy according to the invention has an electrical conductivity of preferably more than 9.0 m / Ohm mm 2Electrical conductivity correlates with thermal conductivity. The proposed alloy is characterized by a particularly high thermal conductivity of more than 60 W / mK at room temperature.

[0016] Furthermore, the proposed copper-zinc alloy is characterized according to the invention in that the intermetallic compounds contained in the as-cast structure have a maximum size of 150 µm. The small size of the intermetallic compounds advantageously contributes to the production of a surface with reduced surface roughness during machining. According to a further development of the invention, the proposed copper-zinc alloy is used to manufacture a turbocharger bearing bush.

[0017] An example of the proposed copper-zinc alloy is explained in more detail below.

[0018] The copper-zinc alloy can have the following composition: Cu 64.2% Mn2.0% Al 1.8% Si 1.3% Fe 0.8% Ni 0.8% Zn Rest

[0019] The following table shows the mechanical properties of the copper-zinc alloy. Table 1: R m (N / mm 2 ) R p0,2 (N / mm 2 ) A(%) Hardness (HBW 2.5 / 62.5) 515 286 25 167

[0020] The copper-zinc alloy has the physical properties shown in the table below. Table 2: Characteristic Density g / cm 3 8,1 Electrical conductivity m / Ohm mm 2 9,3 E-modulus kN / mm 2 131 Coefficient of thermal expansion 15,7 Poisson's ratio 0,39

[0021] The hot tensile strength of the copper-zinc alloy is about 321 N / mm at 350°C 2The copper-zinc alloy is characterized by excellent softening behavior. To determine the softening behavior, the alloy was exposed to temperatures of up to 500°C for an annealing time of one hour. It was found that up to a temperature of 500°C, no reduction in hardness was observed compared to the hardness at room temperature. Even with a temperature treatment of 600°C, the reduction in hardness was less than 10% of the initial hardness at room temperature.

[0022] An embodiment of the invention is explained in more detail below with reference to the drawings. They show: Fig. 1 a microstructure of the copper-zinc alloy according to the invention, Fig. 2 a cross-sectional view of a machined surface of the copper-zinc alloy and Fig.3 a cross-sectional view of a machined surface of a conventional copper-zinc alloy.

[0023] Fig. Figure 1 shows a micrograph of the copper-zinc alloy according to the invention. It can be seen that the maximum size of the intermetallic compounds (dark crystals) in the longitudinal direction of the crystals is 150 mm.

[0024] Fig. Figure 2 shows a cross-sectional view through a surface of a component made of the copper-zinc alloy, wherein the surface has been machined. As can be seen from Fig. As can be seen in Figure 2, surface deviations occur in the area of ​​intermetallic compounds. The deviations have a maximum depth of approximately 2.55 µm.

[0025] Fig.For comparison, Figure 3 shows a cross-sectional view through a machined surface of a component made from a conventional copper-zinc alloy (70.5% Cu, 7.8% Mn, 5.2% Al, 2.0% Si, 1.0% Fe, balance Zn and avoidable impurities). Here, surface deviations with a depth of more than 20 µm occur.

[0026] The copper-zinc alloy according to the invention can therefore be used to produce components that exhibit significantly smaller surface deviations during machining than components made from a conventional copper-zinc alloy. Bearing bushings with improved surface quality can be produced using the copper-zinc alloy according to the invention, particularly during machining. Due to its excellent thermal properties, the copper-zinc alloy according to the invention is particularly suitable for the production of bearing bushings for turbochargers.

Claims

[1] Bearing bush for a plain bearing made of a copper-zinc alloy, comprising 62.5 to 64.5% Cu, 2.7 to 3.5% Mn, 1.3 to 1.9% Al, 0.8 to 1.2% Si, 0.3 to 0.6% Fe, 0 to 1.0% Pb, 0 to 1.5% Ni, 0 to 0.2% Sn, balance Zn and unavoidable impurities, wherein intermetallic compounds contained in the structure in the as-cast state have a size of at most 150 µm, wherein the bearing bush has a machined surface. [2] Bearing bush according to claim 1, wherein the copper-zinc alloy comprises 64.2% Cu, 2.0% Mn, 1.8% Al, 1.3% Si, 0.8% Fe, 0.8% Ni, balance Zn and unavoidable impurities. [3] Bearing bush according to claim 1 or 2, wherein the bearing bush is a turbocharger bearing bush.

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