WO2014073630A1 - Copper alloy - Google Patents

Abstract

A copper alloy having good seizure resistance is provided. The copper alloy is characterized by containing 25.0 wt% to 48.0 wt% of zinc, 1.0 wt% to 7.0 wt% of manganese, and 0.5 wt% to 3.0 wt% of silicon. The copper alloy is further characterized in that a value obtained by dividing the circumference of a circle in which the area and average value of cross-sectional areas of particles of a manganese-silicon compound are equal by the average value of the circumferences of cross sections of the particles of the manganese-silicon compound is not more than 0.5.

Description

Copper alloy

The present invention relates to a copper alloy constituting a sliding member.

A copper alloy in which particles of a Mn—Si compound are dispersed in a matrix composed of Cu and Zn is known (see Patent Documents 1 and 2). Since the Mn—Si compound particles are harder than the matrix, the wear resistance of the copper alloy can be improved.

JP 2003-42145 A JP 2003155553 A

When the mating material is slid in the copper alloys of Patent Documents 1 and 2, the softer matrix than the Mn-Si compound particles is selectively worn, and the load from the mating material is concentrated on the Mn-Si compound particles. It becomes. As a result, the frictional resistance between the Mn—Si compound particles and the counterpart material increases, and there is a problem that seizure occurs between the Mn—Si compound particles and the counterpart material.
The present invention has been made in view of the above problems, and an object thereof is to provide a copper alloy having good seizure resistance.

In order to achieve the above object, the copper alloy of the present invention contains 25.0 wt% or more and 48.0 wt% or less of Zn, 1.0 wt% or more and 7.0 wt% or less of Mn, .5 wt% or more and 3.0 wt% or less of Si, and the circumference of a circle having the same area as the average cross-sectional area of each particle of the Mn—Si compound is represented by the cross section of each particle of the Mn—Si compound. The value divided by the average value of the circumference is 0.5 or less.

The value obtained by dividing the circumference of a circle having the same area as the average cross-sectional area of each particle of the Mn-Si compound by the average value of the circumference of the cross-section of each particle of the Mn-Si compound (hereinafter, circularity) is It is 1 when the shape of each particle of the Mn—Si compound is circular. The degree of circularity decreases as the shape of each particle of the Mn—Si compound deviates from the circular shape. This is because the circumference of a figure having a certain area is the shortest when the figure is circular, and becomes longer as the figure deviates from the circle. For example, assuming a rectangular particle having a ratio of the short side length to the long side length of 1:10, the circularity of the particle is 0.51. Thus, when the ratio of the length of the short side to the length of the long side is about 1:10, it is unlikely that particles of an elongated Mn—Si compound are precipitated, and when the circularity is 0.5 or less, It can be considered that a large number of particles of the Mn—Si compound having an annular cross section having not only the inner periphery but also the outer periphery exist. In other words, it can be considered that there are a large number of particles of the Mn—Si compound having an annular cross section enclosing the inclusion portion of the Cu—Zn matrix. However, in the present invention, the Mn—Si compound having a circular cross section is not necessarily present. The presence of a large number of Mn—Si compound particles having a cyclic cross section or a Mn—Si compound having a cross section close to a ring It is sufficient that the circularity is 0.5 or less.

Since the Cu—Zn matrix is softer than the Mn—Si compound, when the counterpart material is slid on the copper alloy of the present invention, the Cu—Zn matrix is selectively worn. Therefore, the inclusion part of the Cu—Zn matrix in which the particles of the Mn—Si compound having a circular cross section are included is also selectively worn, and a recess is formed inside the particles of the Mn—Si compound having a circular cross section. Lubricating oil can be held in the recess. This is because the contact area of the lubricating oil is increased in the recess, and the affinity with the lubricating oil is increased. In addition, since the lubricating oil enters the recess surrounded by the hard Mn—Si compound, the amount of the lubricating oil scraped off by the counterpart material can be suppressed.

Since the Cu—Zn matrix is selectively worn, the Mn—Si compound particles protrude from the other portions, and the load from the counterpart material is supported by the Mn—Si compound particles. In this case, stress concentrates on the Mn—Si compound particles, and seizure is likely to occur between the Mn—Si compound particles and the counterpart material. However, since the lubricating oil can be held in the vicinity (concave portion) of the Mn—Si compound particles where stress is concentrated, the lubricating oil is continuously supplied to the contact surface between the Ni—Mn—Si compound particles and the counterpart material. be able to. Therefore, seizure can be prevented from occurring between the Mn—Si compound particles and the counterpart material.

Here, by containing 25.0 wt% or more of Zn, the strength of the Cu—Zn matrix can be enhanced, and sulfidation corrosion due to the S component in the lubricating oil can be suppressed. In particular, by containing 35.0 wt% or more of Zn, particles of the Ni—Mn—Si compound can be grown to such a size that more excellent wear resistance can be obtained. Further, by suppressing the Zn content to 48.0 wt% or less, it is possible to prevent the γ phase from being precipitated in a large amount in the Cu—Zn matrix and to prevent the copper alloy from becoming brittle.

Further, by containing 1.0 wt% or more of Mn and 0.5 wt% or more of Si, it is possible to deposit Ni—Mn—Si compound particles sufficient to improve the wear resistance. On the other hand, by suppressing the Mn content to 7.0 wt% or less and the Si content to 3.0 wt% or less, it is possible to prevent the toughness from being lowered due to the precipitation of an excessive Mn—Si compound.

Here, the copper alloy of the present invention may contain Ni in a content such that the mass ratio to Si is 0.06 or more and 0.30 or less. Then, a part of Ni may constitute Ni—Mn—Si compound particles, and another part of Ni may be dissolved in the Cu—Zn matrix. As a result, Ni—Mn—Si compound particles, which are Mn—Si compounds further combined with Ni, can be dispersed in the Cu—Zn matrix. Since the particles of the Ni—Mn—Si compound are harder than the particles of the Mn—Si compound not combined with Ni, the wear resistance of the copper alloy can be improved. Since particles of Ni—Mn—Si compound are harder to break than particles of Mn—Si compound that are not compounded with Ni, the particles are fine even when the load from the counterpart material is concentrated on the particles of Ni—Mn—Si compound. Can be prevented.

Furthermore, the Ni—Mn—Si compound that is not taken in by Ni dissolves in Cu, so that the Cu—Zn matrix can be strengthened by solid solution. That is, when Ni dissolves in Cu, the crystal lattice of the Cu—Zn matrix is distorted, and the movement of transition in plastic deformation can be suppressed. Therefore, the Ni—Mn—Si compound particles can be prevented from plastic flow in the Cu—Zn matrix, and the Ni—Mn—Si compound particles can be prevented from falling off the copper alloy. Therefore, wear resistance can be maintained.

Note that the wear resistance of the copper alloy was insufficient when the mass ratio of Ni to Si was less than 0.06 and when the mass ratio of Ni to Si was greater than 0.30. This is because when the mass ratio of Ni to Si is less than 0.06, Ni is insufficient with respect to Si, and Ni—Mn—Si compound particles are not precipitated to an amount that improves wear resistance. On the other hand, when the ratio of the mass of Ni to Si is larger than 0.30, Ni is excessive with respect to Si, and on the contrary, the precipitation of Ni—Mn—Si compound particles is hindered and the wear resistance is improved. The particles of the Ni—Mn—Si compound do not grow up to the size (size that does not easily drop from the Cu—Zn matrix). On the other hand, when the ratio of the mass of Ni to Si is 0.06 or more and 0.30 or less, Ni—Mn—Si compound particles grown to a size that improves the wear resistance can be obtained. It can be deposited in an amount that improves. In addition, by setting the mass ratio of Ni to Si to be 0.06 or more and 0.30 or less, Ni that cannot be incorporated into the Ni—Mn—Si compound can be present and incorporated into the Ni—Mn—Si compound. The Cu—Zn matrix can be solid solution strengthened by the Ni that has not been formed. The mass ratio of Ni to Si means a value obtained by dividing the mass of Ni contained in the copper alloy by the mass of Si contained in the copper alloy.

Here, the copper alloy of the present invention may contain 1.0 wt% or more and 10.0 wt% or less of Bi. By containing 1.0 wt% or more of Bi, it is possible to improve the seizure resistance and the foreign matter burying property. Moreover, it can prevent that intensity | strength and toughness fall by suppressing content of Bi to 10 wt% or less. Furthermore, by suppressing the Bi content to 10.0 wt% or less, it is possible to prevent the Bi particles from becoming coarse due to the coarsening of the Bi particles and to prevent seizure from occurring in the portion where the Bi distribution is sparse. .

Furthermore, the copper alloy of the present invention is not limited to containing only the above-described components, but Fe, Al, Sn, Cr, Ti, Sb, and B are added so that the total content is 5.0 wt% or less. You may contain. By containing Fe, Al, Sn, Cr, Ti, Sb, and B, the mechanical properties of the Cu—Zn matrix can be enhanced. In particular, by including Al and Cr, the corrosion resistance of the copper alloy can be improved. Moreover, the copper alloy of the present invention may contain inevitable impurities.

It is a perspective view of a radial bearing. (2A) to (2C) are cross-sectional photographs of the radial bearing. (3A) is a schematic diagram for explaining a wear test, (3B) is a schematic diagram for explaining a wear volume, and (3C) is a diagram showing a worn copper alloy. It is a graph which shows the relationship between Ni / Si and hardness. It is a cross-sectional photograph of the radial bearing of other embodiment.

Here, embodiments of the present invention will be described in the following order.
(1) Configuration of radial bearing:
(2) Radial bearing manufacturing method:
(3) Experimental example:
(4) Other embodiments:

(1) Configuration of radial bearing:
FIG. 1 is a perspective view of a radial bearing 1 (floating bush) formed of a copper alloy according to an embodiment of the present invention. For example, in a turbocharger for an internal combustion engine, the radial bearing 1 supports in the radial direction a load acting on a rotating shaft 2 (broken line) provided with turbine blades and compressor blades at both ends in the axial direction. The radial bearing 1 is formed in an annular shape whose inner diameter is larger than the outer diameter of the rotating shaft 2 by a predetermined amount, and an oil film of engine oil as lubricating oil is formed between the radial bearing 1 and the rotating shaft 2. Although not shown, the thrust bearing that supports the load acting on the rotary shaft 2 in the thrust direction may also be formed of the same copper alloy as the radial bearing 1.

Hereinafter, the copper alloy on which the radial bearing 1 is formed will be described. The copper alloy constituting the radial bearing 1 contains 41.3 wt% Zn, contains 4.98 wt% Mn, contains 1.57 wt% Si, and has a mass ratio of 0.15 to Si. The content of Ni (0.23 wt%) is contained, 4.0 wt% Bi is contained, and the balance is composed of Cu and inevitable impurities. Inevitable impurities are Mg, Ti, B, Pb, Cr and the like, which are impurities mixed in refining or scrap. The content of inevitable impurities is 1.0 wt% or less as a whole. The mass of each element in the copper alloy was measured with an ICP emission spectroscopic analyzer.

FIG. 2A shows a photograph of a cross section of the radial bearing 1. As shown in the figure, Ni—Mn—Si compound particles and Bi particles were uniformly dispersed in the Cu—Zn matrix. In FIG. 2A, the Bi particles are lighter in color and have a nearly circular shape than the Ni—Mn—Si compound particles. The color of the Cu—Zn matrix is lighter than the color of Bi particles and Ni—Mn—Si compound particles. Further, Ni—Mn—Si compound particles having an annular cross section existed, and the Cu—Zn matrix inclusion portion was included in the particles having the annular cross section. The inclusion part of the Cu—Zn matrix refers to a part of the same component as the Cu—Zn matrix included in the particles of the Ni—Mn—Si compound having a circular cross section in the cross section. This refers to the part separated from the Cu—Zn matrix outside the grain.

The average equivalent circular diameter of each particle of the Ni—Mn—Si compound in the cross section of the radial bearing 1 was 8.7 μm. That is, the average area of each particle of the Ni—Mn—Si compound in the cross section of the radial bearing 1 was 18.92 × π μm ² . The area ratio of each particle of the Ni—Mn—Si compound in the cross section of the radial bearing 1 was 10.6%. The circularity of each particle of the Ni—Mn—Si compound was 0.30. On the other hand, the average equivalent circle diameter of each encapsulated portion of the Cu—Zn matrix in the cross section of the radial bearing 1 was 4.1 μm. That is, the average area of each inclusion portion of the Cu—Zn matrix in the cross section of the radial bearing 1 was 4.20 × π μm ² . The area ratio of each inclusion portion of the Cu—Zn matrix in the cross section of the radial bearing 1 was 0.4%, and the number of inclusion portions of the Cu—Zn matrix was 12.

Hereinafter, a method for analyzing the cross section of the radial bearing 1 will be described. First, an arbitrary observation visual field range (rectangular range of 0.184 mm in length × 0.244 mm in width) having an area of 3.66 × 10 ⁴ mm ^{2 in} the cross section of the radial bearing 1 is obtained with a metal microscope at an optical magnification of 400 times. Image data of an observation image was obtained by taking a picture. Then, the observation image was input to an image analysis apparatus (Lusex II manufactured by Nireco Co., Ltd.), and images of each particle and each inclusion portion existing in the observation image were extracted. Edges (boundaries that differ in lightness, saturation, and hue angle by a predetermined value or more) exist at the outer edges of the images of the respective particles and the included portions. In view of this, the region closed by the edge was extracted from the observation image as an image of each particle or each inclusion portion by the image analysis device.

Further, a substance present in a portion on the cross section of the radial bearing 1 corresponding to each particle and each inclusion portion image in the observation image is analyzed with a wavelength dispersion type X-ray analyzer (JXA-8100, manufactured by JEOL Ltd.) and X-ray diffraction. It was specified by an analyzer (SmartLab manufactured by Rigaku). As a result, Ni—Mn—Si compound particles and Bi particles exist on the cross section of the radial bearing 1, and the Ni—Mn—Si compound particles having a circular cross section are the same as the Cu—Zn matrix. It was confirmed that the inclusion part of the component was present.

Then, an image of each particle of the Ni—Mn—Si compound was extracted from the observed image, and the projected area circle equivalent diameter (measurement parameter: HEYWOOD) was measured for each particle of the Ni—Mn—Si compound by an image analyzer. The projected area equivalent circle diameter is the diameter of a circle having an area equal to the cross-sectional area of the Ni—Mn—Si compound particles, and the diameter of the circle having an area equal to the area of the Ni—Mn—Si compound particles. Is the diameter converted to the actual length based on the optical magnification. Further, the arithmetic average value (total value / number of particles) of the projected area equivalent circle diameter of each particle of the Ni—Mn—Si compound was measured as the average equivalent circle diameter. Further, by multiplying the area of a circle having a diameter equal to the average equivalent circle diameter of each particle of the Ni—Mn—Si compound by the number of each particle of the Ni—Mn—Si compound existing in the observation visual field range, the radial is obtained. The total area of Ni—Mn—Si compound particles present on the cross section of the bearing 1 was calculated. Then, the area ratio of the Ni—Mn—Si compound particles was measured by dividing the total area of the Ni—Mn—Si compound particles by the area of the observation visual field range.

The average equivalent circle diameter and the area ratio of each inclusion part of the Cu—Zn matrix present on the cross section of the radial bearing 1 were measured by the same method. Note that when the projected area equivalent circle diameter is less than 1.0 μm, the reliability of the projected area equivalent circle diameter and the specific reliability of the substance are lowered, so that each particle of the Ni—Mn—Si compound and the Cu—Zn matrix It was decided not to consider when calculating the average equivalent circle diameter for each inclusion.

Furthermore, the actual circumference (measurement parameter: PRIME) of each particle of the Ni—Mn—Si compound was measured by an image analysis apparatus. The actual circumference is the circumference obtained by converting the length of the edge of the image of the Ni—Mn—Si compound particles into the actual length based on the optical magnification. The length of the edge of the image of the Ni—Mn—Si compound particles having a circular cross section was obtained by summing the length of the outer peripheral edge and the length of the inner peripheral edge. Further, the arithmetic average value (total value / number of particles) of the actual circumference of each particle of the Ni—Mn—Si compound was measured as the average actual circumference. Further, the circumference of a circle having a diameter equal to the average equivalent circle diameter of each particle of the Ni—Mn—Si compound was measured as the average equivalent circle circumference. Further, the circularity was calculated by dividing the average equivalent circumference of each particle of the Ni—Mn—Si compound by the average actual circumference.

Here, the average equivalent circle diameter is the average value of the projected area equivalent circle diameter, which is the diameter of a circle having an area equal to the cross-sectional area of each particle of the Ni—Mn—Si compound. That is, the average equivalent circle diameter means the diameter of a circle having the same area as the average cross-sectional area of each particle of the Ni—Mn—Si compound. Accordingly, the average equivalent circle circumference, which is the length of the circumference of a circle having a diameter equal to the average equivalent circle diameter of each particle of the Ni—Mn—Si compound, is the cross-sectional area of each particle of the Ni—Mn—Si compound. It means the circumference of a circle whose area is equal to the average value. That is, the circularity is the circumference of a circle having the same area as the average cross-sectional area of each particle of the Ni—Mn—Si compound (average circle equivalent circumference), and the circularity of each particle of the Ni—Mn—Si compound. It means the value divided by the average value of the actual circumference (average actual circumference).

Further, the elements present at each position on the cross section of the radial bearing 1 were analyzed by an electron beam microanalyzer (JXA-8100 manufactured by JEOL). As a result, Ni was detected in the entire region of the Cu—Zn matrix including the inclusion portion, and it was confirmed that Ni was uniformly dissolved in the Cu—Zn matrix. Note that the portion of the Cu—Zn matrix is a portion where Ni—Mn—Si compound particles and Bi particles do not exist.

When the shape of each particle of the Ni—Mn—Si compound is circular, the average equivalent circle circumference and the average actual circumference are the same, and the circularity is 1. The degree of circularity becomes smaller as the shape of each particle of the Ni—Mn—Si compound deviates from the circular shape. This is because the circumference of a figure having a certain area is the shortest when the figure is circular, and becomes longer as the figure deviates from the circle. For example, assuming a rectangular particle having a ratio of the short side length to the long side length of 1:10, the circularity of the particle is 0.51. Thus, the possibility of precipitation of elongated Ni—Mn—Si compound particles having a ratio of the short side length to the long side length of about 1:10 is low, and the circularity is 0.5 or less. In this case, it can be considered that a large number of Ni—Mn—Si compound particles having an annular cross section having not only the inner periphery but also the outer periphery exist. That is, a small circularity means that there are a large number of Ni—Mn—Si compound particles having an annular cross section. In addition, the number of inclusion portions of the Cu—Zn matrix can be regarded as the number of Ni—Mn—Si compound particles having an annular cross section. Therefore, a large number of inclusions in the Cu—Zn matrix means that a large number of Ni—Mn—Si compound particles having an annular cross section exist.

2B and 2C are enlarged views of the cross section of the Ni—Mn—Si compound particles. As shown in FIG. 2B, a straight line connecting the geometric center of gravity G of the cross section of the Ni—Mn—Si compound particle having the annular cross section and the point Y on the Ni—Mn—Si compound particle is drawn. In addition, the straight line passes through the inclusion part of the Cu—Zn matrix. In addition, as shown in FIG. 2C, the geometric gravity center G of the cross section of the Ni—Mn—Si compound particle having a cross section that is not circular but has a ring-like shape, and the Ni—Mn—Si compound particle Even when a straight line connecting the point Y is drawn, the straight line passes through the Cu—Zn matrix.

Next, the mechanical characteristics of the radial bearing 1 will be described. The hardness of the copper alloy constituting the radial bearing 1 of the present embodiment was 2180 N / mm ² . The hardness was measured by forming indentations on the surface of a test piece formed under the same conditions as the copper alloy constituting the radial bearing 1 with an ultra-fine indentation hardness tester (ENT-1100a manufactured by Elionix). Specifically, an indentation is formed on the surface of the test piece by applying a load of 1000 mgf (9.80665 × 10 ⁻³ N) with a Barkovic indenter (triangular pyramid indenter) at room temperature (15 to 30 ° C.). The hardness was measured based on the size of.

Further, the specific wear amount of the copper alloy constituting the radial bearing 1 of the present embodiment was 1.0 × 10 ⁻¹⁰ mm ² / N. FIG. 3A is a schematic diagram illustrating a cylindrical flat plate type frictional wear tester used for measuring the specific wear amount. In the abrasion test, the cylindrical mating shaft A is rotated while being partially immersed in engine oil (liquid paraffin) F as a lubricating oil, and a test piece T is applied so that a predetermined test load acts on the mating shaft A. Was brought into contact with the mating shaft A. The test piece T was formed under the same conditions as the copper alloy constituting the radial bearing 1. The mating shaft A was formed of the same material as the rotating shaft 2 that the radial bearing 1 supports, and was specifically formed of SCM415 (chromium molybdenum steel) that had been subjected to quenching treatment. The length a of the test piece T in the rotation axis direction of the mating shaft A was 10 mm, and the radius r of the bottom surface of the mating shaft A was 20 mm. The rotational speed of the mating shaft A was controlled so that the relative movement speed b of the mating shaft A with respect to the test piece T at the sliding portion was 200 mm / sec. The test load W was 139 N, the temperature of the lubricating oil was room temperature, and the test time c was 3600 sec (1 hour). After performing the wear test under the above conditions, the profile of the depth of the sliding portion of the test piece T with the mating shaft A was measured by a surface roughness meter (SE3400, manufactured by Kosaka Laboratory). And the difference in depth between the flat part (non-wear part) and the deepest part in the depth profile was measured as the wear depth d. Further, in the wear test, seizure did not occur between the test piece T and the counterpart shaft A.

　Ｌは摺動距離であり、摩耗試験において試験片Ｔ上を摺動した相手軸Ａの表面の長さである。摺動距離Ｌは、相対移動速度ｂに試験時間ｃを乗算した値（ｂ×ｃ）である。Ｖは、摩耗試験において摩耗した試験片Ｔの体積（摩耗体積）である。（１）式に示すように、非摩耗量Ｋとは、試験片Ｔに単位荷重（１Ｎ）を作用させた場合に、単位摺動距離（１ｍｍ）あたりに摩耗した試験片Ｔの体積を意味する。 Further, the specific wear amount K was calculated by the following equation (1).

L is a sliding distance, which is the length of the surface of the mating shaft A slid on the test piece T in the wear test. The sliding distance L is a value (b × c) obtained by multiplying the relative movement speed b by the test time c. V is the volume (wear volume) of the test piece T worn in the wear test. As shown in the equation (1), the non-wear amount K means the volume of the test piece T worn per unit sliding distance (1 mm) when a unit load (1 N) is applied to the test piece T. To do.

Next, the wear volume V will be described. FIG. 3B is a schematic diagram illustrating the wear volume V. FIG. As shown by hatching in FIG. 3B, the shape of the worn portion of the test piece T can be considered to be the shape of the portion of the counterpart shaft A that has entered the test piece T at the end of the wear test. Enters most deeply mating shaft A in the radial CP ₀ perpendicular from the center C of the circular bottom of the mating shaft A the sliding surface of the test piece T, in the radius CP ₀ depth that penetrates the mating axis A The wear depth is d. Here, on the circumference of the bottom surface of the mating shaft A, when the lower limit points of the portions that have entered the test piece T at the end of the wear test are respectively expressed as P ₁ and P ₂ , the wear volume V is the mating shaft A. Can be obtained by multiplying the area of the portion surrounded by the arc P ₁ P ₂ and the string P ₁ P ₂ by the length a of the test piece T. The area of the bottom surface of the counterpart axis A surrounded by the arc P ₁ P ₂ and the chord P ₁ P ₂ is the sector area S ₁ surrounded by the arc P ₁ P ₂ and the radii CP ₁ and CP _2. From this, the area S _{2 of} the triangle surrounded by the chord P ₁ P ₂ and the radii CP ₁ and CP ₂ is subtracted. Therefore, the wear volume V can be calculated by the following equation (2).

　ここで、θは、半径ＣＰ₁，ＣＰ₂が相手軸Ａの底面の中心Ｃにてなす角度の半分を表す。なお、角度θは、以下の（４）式を満足する。

　一方、前記三角形の面積Ｓ₂は図形の対称性から以下の（５）式によって算出できる。

The fan-shaped area S ₁ can be calculated by the following equation (3).

Here, θ represents half the angle formed by the radii CP ₁ and CP ₂ at the center C of the bottom surface of the counterpart axis A. The angle θ satisfies the following expression (4).

On the other hand, the area S ₂ of the triangle can be calculated by the following equation (5) from the symmetry of the graphic.

As described above, the radial bearing 1 of the present embodiment has a hardness of 2180 N / mm ² and a specific wear amount of 1.0 × 10 ⁻¹⁰ mm ² / N. High wear resistance can be demonstrated during operation. This is because the Ni—Mn—Si compound particles are hard. In addition, since the Ni—Mn—Si compound particles are difficult to break, the wear resistance can be maintained. Further, Ni that has not been taken into the Ni—Mn—Si compound is dissolved in Cu, whereby the Cu—Zn matrix can be strengthened by solid solution. Accordingly, it is possible to prevent the Ni—Mn—Si compound particles from plastically flowing in the Cu—Zn matrix, and to prevent the Ni—Mn—Si compound particles from falling off the radial bearing 1. Therefore, wear resistance can be maintained.

FIG. 3C is a schematic view showing a cross section of the test piece T after the wear test cut perpendicularly to the wear surface. As shown in the figure, since the Cu—Zn matrix (L) is softer than the Ni—Mn—Si compound (Q), the Cu—Zn matrix is selectively worn. Therefore, the Cu—Zn matrix-encapsulated portion in which the Ni—Mn—Si compound particles having an annular cross section are encapsulated is also selectively worn, and a recess (D) is formed inside the Ni—Mn—Si compound particles having an annular cross section. It is formed. The engine oil (F) can be held in the recess. This is because the contact area of the engine oil is increased in the recess, and the affinity between the engine oil and the test piece T is increased. In addition, since engine oil enters the inside of the recess surrounded by the hard Ni—Mn—Si compound, the amount of engine oil scraped off by the mating shaft A can also be suppressed.

Since the Cu—Zn matrix is selectively worn, the Ni—Mn—Si compound particles protrude from the other portions and the Ni—Mn—Si compound particles support the load from the counterpart axis A. . In this case, stress concentrates on the Ni—Mn—Si compound particles, and seizure is likely to occur between the Ni—Mn—Si compound particles and the counterpart shaft A. However, since engine oil can be held in the vicinity (concave portion) of Ni—Mn—Si compound particles where stress is concentrated, engine oil is applied to the contact surface between the Ni—Mn—Si compound particles and the mating shaft A. Can be supplied continuously. Therefore, the radial bearing 1 of the present embodiment can achieve both hardness and seizure resistance.

(2) Radial bearing manufacturing method:
In the present embodiment, the radial bearing 1 includes a. Melting, b. Continuous casting, c. Cutting, d. It is manufactured by performing each process of machining in order. Hereinafter, each step will be described.

a. Melting First, Ni (0.195 wt%) containing 42.0 wt% Zn, 4.0 wt% Mn, 1.3 wt% Si, and having a mass ratio to Si of 0.15 Each raw material is weighed and prepared so that a copper alloy containing 4.0 wt% Bi and the balance of Cu and inevitable impurities can be formed. For example, a Cu ingot, a Zn ingot, a Bi ingot, a Cu—Mn ingot, a Cu—Si ingot, and a Cu—Ni ingot are respectively prepared by weighing. Here, a raw material having a mass corresponding to the mechanical characteristics (hardness, specific wear amount, and seizure resistance) of the target radial bearing 1 may be prepared. The target mechanical characteristics of the radial bearing 1 are determined according to, for example, the mechanical characteristics of the rotating shaft 2 as a counterpart material. Next, each prepared raw material is heated to 1250 degreeC with a high frequency induction furnace. Thereby, each ingot melts. Thereafter, bubbles of Ar gas are dispersed and ejected to remove hydrogen gas and inclusions.

b. Continuous casting Next, a molten copper alloy material is poured into a mold, the copper alloy is continuously drawn out from the opening of the mold in the casting direction, and cooled to room temperature as it is, thereby forming a copper alloy continuous casting rod. . For example, casting is performed at 1060 ° C. with a mold made of carbon, and the continuous casting rod is formed by drawing at a drawing speed of 160 mm / min. Ni—Mn—Si compound particles and Bi particles precipitate in the copper alloy that solidifies during continuous casting. Note that the diameter of the copper alloy continuous casting rod is set to be larger than the outer diameter of the radial bearing 1 by the amount of cutting in machining.

c. Cutting Next, the continuous casting rod of copper alloy is cut for each thickness of the radial bearing 1 (thickness in the length direction of the rotating shaft 2).

d. Finally, the radial bearing 1 is completed by cutting or pressing the continuous cast bar of the copper alloy after cutting. Here, a through hole having an inner diameter larger than the outer diameter of the rotating shaft 2 by a predetermined amount is formed, and cutting is performed so that the outer diameter of the radial bearing 1 matches the design value.

(3) Experimental example:
Table 1 shows the results of measurement of hardness, specific wear, and the like for samples 1 to 12 prepared for each combination of the contents of each element constituting the copper alloy. Further, samples 1 to 12 of the copper alloy were prepared under the conditions described in the manufacturing method described above.

As shown in Table 1, the lower limit (25.0 wt%) and upper limit (48.0 wt%) of the Zn content, the lower limit (1.0 wt%) and upper limit (7.0 wt%) of the Mn content %), Lower limit (0.5 wt%) and upper limit (3.0 wt%) of the Si content, and lower limit (0.06) and upper limit (0) of the ratio of the mass of Ni to the mass of Si Samples 1 to 12 were prepared for each combination of. However, in the combination of the lower limit value of Mn content (1.0 wt%) and the upper limit value of Si content (3.0 wt%), a brittle γ phase is formed in the Cu—Zn matrix, and the radial bearing 1 As necessary toughness cannot be secured, it was excluded from the experiment.

In Table 1, in any of the samples 1 to 12, a hardness of 1050 N / mm ² or more was obtained, and it was confirmed that the specific wear amount could be suppressed to 4.5 × 10 ⁻¹⁰ mm ² / N or less. In Samples 1 to 12, the average equivalent circle diameter of each particle of the Ni—Mn—Si compound is 4.2 to 11.5 μm, and Ni— of an appropriate size is required to achieve good hardness and wear resistance. It can be said that particles of the Mn—Si compound are precipitated. In Samples 1 to 12, the area ratio of the Ni—Mn—Si compound particles was 4.0 to 14.3%, and an appropriate amount of Ni—Mn was used to achieve good hardness and wear resistance. It can be said that particles of -Si compound are precipitated.

　また、図４は、表２の試料１３～１８の硬さを示すグラフである。図４の横軸はＳｉの質量に対するＮｉの質量の比（Ｎｉ／Ｓｉ）を示し、縦軸は硬さを示す。同図に示すように、Ｓｉの質量に対するＮｉの質量の比が０．１５の試料１６（実施形態）において最大の硬さ（２１８０Ｎ／ｍｍ²）が得られた。また、０．１５よりも大きい範囲においてＳｉの質量に対するＮｉの質量の比が大きくなるほど、硬さが小さくなる。Ｓｉの質量に対するＮｉの質量の比が大きくなりすぎると、過剰なＮｉによってＮｉ－Ｍｎ－Ｓｉ化合物の生成、成長を阻害され、適切な大きさのＮｉ－Ｍｎ－Ｓｉ化合物の粒子が形成できないためと推測される。また、０．１５よりも小さい範囲においてＳｉの質量に対するＮｉの質量の比が小さくなるほど、硬さが小さくなる。Ｓｉに対してＮｉが不足するにより耐摩耗性を向上させる量までＮｉ－Ｍｎ－Ｓｉ化合物の粒子が析出しないからである。上述した実施形態のラジアル軸受１を構成する銅合金は、試料１６に近い組成を有しているため、極めて良好な硬さ、すなわち耐摩耗性を得ることができた。 By the way, the hardness of the copper alloy constituting the radial bearing 1 of the above-described embodiment is 2180 N / mm ² , which is much larger than the samples 1 to 12. The reason will be described below. Table 2 shows the results of measuring the hardness of samples 13 to 18 prepared by changing the ratio of the mass of Ni to the mass of Si.

FIG. 4 is a graph showing the hardness of samples 13 to 18 in Table 2. The horizontal axis of FIG. 4 represents the ratio of Ni mass to Ni mass (Ni / Si), and the vertical axis represents hardness. As shown in the figure, the maximum hardness (2180 N / mm ² ) was obtained in the sample 16 (embodiment) in which the ratio of the mass of Ni to the mass of Si was 0.15. In addition, the hardness decreases as the ratio of Ni mass to Si mass increases in a range larger than 0.15. If the ratio of Ni mass to Si mass becomes too large, the formation and growth of Ni—Mn—Si compounds are hindered by excessive Ni, and Ni—Mn—Si compound particles of an appropriate size cannot be formed. It is guessed. In addition, the hardness decreases as the ratio of Ni mass to Si mass decreases in a range smaller than 0.15. This is because the Ni—Mn—Si compound particles do not precipitate to an amount that improves wear resistance due to the lack of Ni relative to Si. Since the copper alloy which comprises the radial bearing 1 of embodiment mentioned above has the composition close | similar to the sample 16, extremely favorable hardness, ie, abrasion resistance, was able to be acquired.

Furthermore, as shown in Table 2, the Bi content in Samples 13 to 18 is changed, but it can be understood that the Bi content does not significantly affect the hardness. Therefore, by containing 1.0 wt% or more and 10.0 wt% or less of Bi, it is possible to improve the seizure resistance and the foreign matter embedment property and to achieve good hardness.

　また、上述した製造方法に記載した条件で銅合金の各試料１９～２９を作成した。表３に示すように、概ねＮｉ－Ｍｎ－Ｓｉ化合物の各粒子の円形度は０．５以下となった。Ｎｉ－Ｍｎ－Ｓｉ化合物の粒子は連続鋳造時において析出する。さらに、連続鋳造時において、Ｎｉ－Ｍｎ－Ｓｉ化合物の各粒子が粒子間の隙間が埋まり切らない程度に凝集することにより、環状になると推定される。１６０ｍｍ／ｍｉｎの引抜速度で引き抜いて連続鋳造棒を形成することにより、Ｎｉ－Ｍｎ－Ｓｉ化合物が析出し、凝集が可能な温度帯（９００℃程度）において適度な保持時間を確保することができたものと推定される。 Table 3 shows the state of each particle of the Ni—Mn—Si compound and the Ni—Mn—Si compound particles included in the samples 19 to 28 prepared for each combination of the contents of each element constituting the copper alloy. The result of investigating the state of each inclusion part of the Cu—Zn matrix is shown.

Further, samples 19 to 29 of copper alloy were prepared under the conditions described in the manufacturing method described above. As shown in Table 3, the circularity of each particle of the Ni—Mn—Si compound was approximately 0.5 or less. Ni—Mn—Si compound particles are precipitated during continuous casting. Further, during continuous casting, each particle of the Ni—Mn—Si compound is presumed to be in an annular shape by agglomerating to such an extent that the gaps between the particles are not filled. By forming a continuous cast rod by drawing at a drawing speed of 160 mm / min, it is possible to secure an appropriate holding time in a temperature zone (about 900 ° C.) where Ni—Mn—Si compound is precipitated and can be agglomerated. Estimated.

Regarding Table 3, when the correlation between the content of each element and the circularity was investigated, the strongest positive correlation (correlation coefficient 0.47) was found between the Zn content and the circularity. That is, it can be estimated that the greater the Zn content, the greater the degree of circularity, and the smaller the Zn content, the more likely the shape of each particle of the Ni—Mn—Si compound to be cyclic. Since Samples 19 to 28 were prepared with a Zn content close to the upper limit of 48.0 wt% of the Zn content of the present invention, Ni- having an annular cross section within the Zn content range of the present invention. It is considered that each particle of the Mn—Si compound can be formed. Further, almost no correlation was found between the elements other than Zn and the circularity. Therefore, it is considered that each particle of the Ni—Mn—Si compound having a circular cross section can be formed even if the contents of Mn, Si, and Ni are changed within the scope of the present invention.

(4) Other embodiments:
In the said embodiment, although the example which formed the radial bearing 1 with the copper alloy of this invention was shown, you may form another sliding member with the copper alloy of this invention. For example, a gear bush for a transmission, a piston pin bush, a boss bush, or the like may be formed from the copper alloy of the present invention. The copper alloy of the present invention may contain Fe, Al, Sn, Cr, Ti, Sb, and B so that the total content is 5% wt or less.

Moreover, the copper alloy of the present invention does not necessarily contain Ni. This is because each particle of the Mn—Si compound which is cyclic and harder than the Cu—Zn matrix can be formed without containing Ni. That is, even if Ni is not contained, the engine oil can be held in the recesses formed inside the particles of the Mn—Si compound having an annular cross section as shown in FIG. 3B. FIG. 5 shows a photograph of a cross section of a copper alloy not containing Ni. The copper alloy whose cross-sectional photograph is shown in FIG. 5 contains 43.4 wt% Zn, contains 4.5 wt% Mn, contains 1.45 wt% Si, and contains 3.7 wt% Bi. The balance consists of Cu and inevitable impurities. As shown in FIG. 5, it was found that even when Ni was not contained, particles of the Mn—Si compound having an annular cross section were formed.

DESCRIPTION OF SYMBOLS 1 ... Radial bearing, 2 ... Rotating shaft, A ... Opposite shaft, T ... Test piece.

Claims (3)

Containing 25.0 wt% or more and 48.0 wt% or less of Zn,
Containing 1.0 wt% or more and 7.0 wt% or less of Mn,
Containing 0.5 wt% or more and 3.0 wt% or less of Si,
The value obtained by dividing the circumference of a circle having the same area as the average cross-sectional area of each particle of the Mn-Si compound by the average value of the cross-sectional circumference of each particle of the Mn-Si compound is 0.5 or less.
A copper alloy characterized by that. In the cross section, a Cu—Zn matrix is encapsulated inside the particles of the Mn—Si compound.
The copper alloy according to claim 1. Containing Ni having a mass ratio to Si of 0.06 or more and 0.30 or less,
A part of Ni constitutes particles of a Ni—Mn—Si compound, and another part of Ni is dissolved in the Cu—Zn matrix.
The copper alloy according to claim 1 or 2.

Images