WO2011111603A1 - Al-based bearing alloy - Google Patents

Abstract

Disclosed is an Al-based bearing alloy which comprises 1 to 15 mass% of Si. When the distance between adjacent Si particles at the surface of the sliding side of the Al-based bearing alloy is A and the major axis length of the Si particles is a, the average of A/a exceeds 1 but is 4 or less.

Description

Al base bearing alloy

The present invention relates to an Al-based bearing alloy containing Si.

Al-based bearing alloys include, for example, an Al—Sn bearing alloy to which Sn is added at about 20% by mass, an Al—Sn—Si bearing alloy to which about 10% by mass of Sn and about 3% by mass of Si are added. Used in plain bearings for industrial machinery engines. In addition, when an Al-based bearing alloy is used as a slide bearing, it is generally used by being joined to a steel plate back metal. Here, Si in the Al-based bearing alloy is a hard particle, and when it comes into contact with the mating shaft, the projection of the mating shaft is smoothed (wrapping effect). Contributes to the so-called wear resistance.

By the way, in recent automobile engines, there is a tendency to start and stop frequently in order to improve fuel consumption. For example, the weight of a housing such as a connecting rod to which a slide bearing is assembled is being reduced. However, when the thickness is reduced to reduce the weight of the housing, the rigidity of the housing is lowered, and the housing itself is easily deformed. Therefore, the housing itself is deformed by the dynamic load of the shaft supported by the Al-based bearing alloy (slide bearing), and the Al-based bearing alloy itself is easily bent and deformed, resulting in fatigue in the Al-based bearing alloy. It is easy.

As countermeasures, for example, in an Al-based bearing alloy containing Si, a mixture in which small Si particles and large Si particles are mixed at an appropriate ratio to improve wear resistance and fatigue resistance has been proposed. (For example, refer to Patent Document 1).

JP 2003-119530 A

Under the recent severe conditions of use, a material having further excellent wear resistance and fatigue resistance is required.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an Al-based bearing alloy that is further excellent in wear resistance and fatigue resistance.

The inventors of the present invention have made extensive studies focusing on the relationship between the size of Si particles contained in an Al-based bearing alloy containing 1 to 15% by mass of Si and the distance between adjacent Si particles. . As a result, the present inventors have determined that the relationship between the size of Si particles and the distance between adjacent Si particles is closely related to wear resistance and fatigue resistance, and have reached the present invention.

That is, according to the present invention, in an Al-based bearing alloy containing 1 to 15% by mass of Si, the distance between adjacent Si particles existing on the sliding surface is A, and the major axis length of the Si particles is a. The average value of A / a is more than 1 and 4 or less (Invention of Claim 1).

Here, how to obtain A / a will be described. The structure of the surface on the sliding side is photographed in an Al-based bearing alloy containing Si. The obtained image is analyzed using analysis software, and each parameter is measured.

FIG. 1 is an analysis image diagram in which the arrangement of the Si particles 1 is idealized. In FIG. 1, a line drawn between adjacent Si particles 1 is a Voronoi boundary line. In FIG. 1, the major axis length a of the Si particle 1 is the dimension of the longer side in the circumscribed rectangle surrounding the Si particle 1. Then, the distance A between the centers of gravity between the adjacent Si particles 1 is divided by the major axis length a of the Si particles 1. This is performed for each Si particle 1 within a predetermined measurement field, and the average value of A / a is obtained.

Here, when the average value of A / a is more than 1 and 4 or less, it can be determined that the Si particles are uniformly dispersed in the Al matrix at appropriate intervals. It can be expected to have the effect of lapping and wear resistance, which is a function, and the effect of fatigue resistance.

However, when the A / a value exceeds 4, the proportion of the Al matrix increases, and the effect of the lapping effect and wear resistance in particular decreases. On the other hand, when the average value of A / a is 1 or less, the Al matrix occupies a small proportion, so that the flexibility as a bearing alloy is lowered, the conformability is rapidly lowered, and the fatigue resistance is lowered. .

The Al-based bearing alloy of the present invention is manufactured as follows.
First, an Al-based alloy plate-like billet (cast plate) is manufactured by using, for example, a continuous casting machine using Al and Si and necessary additives. Then, rolling is repeated until the billet has a predetermined thickness. At this time, rolling is performed at a high rolling reduction twice or more. Specifically, the first rolling reduction is 40 to 80%. The second rolling reduction is 30 to 70%. The n + 1th rolling reduction is preferably lower than the nth rolling reduction. Thus, by rolling at a high rolling reduction twice or more, the crystal grains of the Al matrix that becomes the parent phase in the Al-based alloy are eliminated. In this case, the disappearance of crystal grains is defined as the fact that the crystal grain boundaries are too dense to confirm the Al crystal grain boundaries on the cross-sectional etching structure. It is considered that Si particles can be uniformly dispersed in the Al matrix by rolling the Al matrix so that the crystal grains disappear.

After this, Al is recrystallized by heat treatment. As a result, the Si particles are dispersed as uniformly as possible in the Al matrix, and the shape of the Si particles is considered to be moderate.

The Al-based bearing alloy according to claim 2 of the present invention is characterized in that the average aspect ratio of the Si particles present on the surface on the sliding side is 1 or more and 2.5 or less.
The aspect ratio of the Si particles is a value obtained by dividing the length (long axis) of the longer side of the circumscribed square of the Si particle 1 in FIG. 1 by the length (short axis) of the shorter side. As the aspect ratio is closer to 1, the shape of the Si particles becomes closer to a circle or a square, and as the aspect ratio increases, the shape of the Si particles becomes longer and thinner.

The shape of the Si particles is closely related to the fatigue resistance of the bearing alloy. That is, the aspect ratio of the Si particles indicates the degree of anisotropy of the shape of the Si particles. When the aspect ratio is large, a force is preferentially applied to Si particles having an anisotropic shape, and the bearing alloy tends to be deformed, so that the fatigue resistance tends to be lowered. The average value of the aspect ratio of the Si particles is preferably 1 or more and 2.5 or less.

In the Al-based bearing alloy of the present invention, when the billet is repeatedly rolled until it reaches a predetermined thickness, the first rolling reduction is set to 50 to 70%. It can be rolled and manufactured at 40 to 60%. The (n + 1) th rolling reduction is preferably set to a rolling reduction that is 10% lower than the nth rolling reduction. For example, when the n-th reduction ratio is 60%, the (n + 1) -th reduction ratio is set to 50%.

Further, it has arbitrary specific Si particles present on the surface on the sliding side, A is the distance to the Si particles adjacent to the specific Si particles on the surface on the sliding side, and the long axis of the specific Si particles When the length is a, the nearest Si particle adjacent to the specific Si particle in the thickness direction has a radius r centered on the center of gravity of the specific Si particle: r = B × (A / a) (μm)
a / 2 <B ≦ 20
(Invention of claim 3).

This will be described with reference to the image diagram shown in FIG. The direction D in FIG. 2 is the thickness direction. Along with the distribution of Si particles 11, 12, 13, and 14 present on the surface 10 on the sliding side, the distance to the nearest Si particles 21, 22, and 23 adjacent in the thickness direction is closely related to the wear resistance. Yes. That is, if the distance from any specific Si particles 11, 12, 13, 14 existing on the sliding surface 10 to the nearest Si particles 21, 22, 23 adjacent in the thickness direction is greater than or equal to a predetermined value, the resistance is further improved. Abrasion is improved. On the other hand, if the distance from the specific Si particles 11, 12, 13, 14 to the nearest Si particles 21, 22, 23 adjacent in the thickness direction is too large, the wear resistance tends to be lowered. Therefore, the nearest Si particles 21, 22, 23 adjacent to the specific Si particles 11, 12, 13, 14 existing on the surface 10 on the sliding side in the thickness direction are from the specific Si particles 11, 12, 13, 14 The region 30 is within a range defined by a circle having a predetermined radius r. Thereby, progress of wear can be eased, avoiding fracture of material.

Here, the nearest Si particles 21, 22, and 23 are not limited to the entire region but are at least partially included in the region 30 defined by the circle having the radius r from the specific Si particles 11, 12, 13, and 14. It only has to be.

The arrangement of the Si particles in the thickness direction can be controlled as follows.
The manufactured billet is rolled at least twice. Specifically, the first rolling reduction is 40 to 80%, preferably 50 to 70%. The second rolling reduction is set to 60 to 9.5% of the first rolling reduction. Thereby, the crystal grains of the Al matrix in the Al-based alloy disappear, and the arrangement of the Si particles adjacent in the thickness direction is controlled. It is preferable that the n + 1th rolling reduction be 60 to 9.5% of the nth rolling reduction.

The coefficient B is defined to be larger than the value of a / 2 and 20 or less. However, in the measurement practice, the value of a when identifying the value of a / 2 is determined by each major axis in a predetermined measurement field of view. The average value from the length a is used.

It is more preferable from the viewpoint of improvement in wear resistance and fatigue resistance when the nearest Si particles are present in a range surrounded by 2a / 3 ≦ r ≦ 15 × (A / a). Here, in the measurement practice, the average value from each major axis length a in the predetermined measurement field is used as the value a when identifying the value 2a / 3.

Furthermore, the radius r defining the region 30 is preferably 2 μm or more and 50 μm or less from the viewpoint of manufacturing.
The distance between the center of gravity of the specific Si particle and the center of gravity of the nearest Si particle is 5 μm or more, which is advantageous for improving the fatigue resistance, and it is advantageous for improving the wear resistance of 30 μm or less.

The Al-based bearing alloy according to claim 4 of the present invention is characterized by containing one or more of the following (1) to (3).
(1) The total amount of one or more elements selected from Cu, Zn, and Mg is 0.1 to 7% by mass
(2) 0.01 to 3% by mass in total of one or more elements selected from Mn, V, Mo, Cr, Co, Fe, Ni and W
(3) Total amount of one or more elements selected from B, Ti and Zr is 0.01 to 2% by mass
The reasons for limiting the composition of each of the components (1) to (3) will be described as follows.

The selective elements (Cu, Zn, Mg) listed in (1) above are additive elements that improve the strength of the Al matrix, and can be forcibly dissolved in the Al matrix by solution treatment. By aging, a fine compound can be precipitated. The effect cannot be expected if the content is less than 0.1% by mass, and if it exceeds 7% by mass, the compound becomes coarse. The total content is preferably 0.5 to 6% by mass.

The selective elements (Mn, V, Mo, Cr, Co, Fe, Ni, W) listed in (2) above are either dissolved in the Al matrix alone or crystallized as a multi-component intermetallic compound. And improve fatigue resistance. If the content is less than 0.01% by mass, the effect cannot be obtained. From the viewpoint of conformability as a bearing alloy, 3% by mass or less is desirable. The preferred content is 0.02 to 2% by mass.

The selective elements (B, Ti, Zr) mentioned in the above (3) do not contribute to the formation of Al—Si—Fe intermetallic compounds, but are dissolved in the Al matrix to increase the fatigue strength of the bearing alloy. have. If the content is less than 0.01% by mass, the effect is not obtained. From the viewpoint of brittleness as a bearing alloy, 2% by mass or less is desirable. The preferred content is 0.02 to 0.5% by mass.

Analysis image diagram with idealized Si particle arrangement Analysis image diagram of Si particle arrangement idealized in cross section in thickness direction Side view showing schematic configuration of rolling process Schematic showing the conditions of the wear test Schematic diagram showing fatigue test conditions The figure which shows the test result of the example product and the comparative product

In order to confirm the effect of the Al-based bearing alloy of the present invention, slide bearing samples using the Al-based bearing alloy containing Si (Example product and Comparative product) were manufactured, and wear tests were performed on these samples. And fatigue tests were performed.

The manufacturing method of the Example product is as follows.
First, a billet of an Al-based bearing alloy containing Si was cast with a continuous casting machine. Specifically, the composition shown in FIG. 6 was used as a melting material for producing an Al-based bearing alloy, and a plate-like Al-based alloy billet having a thickness of about 15 mm was obtained.

Thereafter, the billet was cold rolled a plurality of times until a predetermined thickness (for example, 1 mm) was obtained to obtain a thin plate-like Al-based bearing alloy. As shown in FIG. 3, the rolling process is performed by passing a plate-shaped billet 111 between a pair of upper and lower rollers 112 and 113 and applying pressure while rotating these rollers 112 and 113. In this rolling step, in order to eliminate Al matrix crystal grains that are the parent phase in the Al-based alloy, in this embodiment, rolling at a high reduction rate is performed at least twice. The first rolling reduction is about 70%, and the second rolling reduction is about 50%, which is slightly lower.

Thereafter, the obtained Al-based bearing alloy is brought into pressure contact with the steel plate constituting the back metal layer to produce a bearing forming plate. At this time, as a pretreatment when the Al-based bearing alloy is pressure-contacted, the maximum height roughness of the surface of the steel sheet on the bonding side may be set to about 5 to 40 μm to secure the adhesive force. After pressure welding, annealing is performed to increase the adhesive force and to remove strain. Thereafter, the obtained plate material for forming a bearing was machined into a semi-cylindrical shape to obtain a half bearing. This was made into the Example goods.

The manufacturing method of the comparative example product is different from the manufacturing method of the example product in the following points. That is, after producing a 15 mm billet of an Al-based alloy with a continuous casting machine using the same material as the example product, the billet is rolled a plurality of times until it reaches a predetermined thickness (1 mm) in the rolling process. The rolling reduction in one rolling at this time is 25% or less at the maximum as usual. Thereafter, the obtained Al-based bearing alloy is brought into pressure contact with the steel plate constituting the back metal layer in the same manner as in the example product to produce a bearing forming plate. After pressure welding, annealing is performed to increase the adhesive force and to remove strain. Thereafter, the obtained plate material for forming a bearing was machined into a semi-cylindrical shape to obtain a half bearing. This was a comparative product.

For the example product and the comparative product, the sliding side surface and the thickness direction cross section of the Al-based bearing alloy were photographed with an optical microscope, and the obtained images were analyzed with analysis software (Image-Pro Plus (Version 4.). 5) (trade name): manufactured by Planetron Co., Ltd.), the major axis length a of each Si particle and the distance A between adjacent Si particles are measured, and the average value of A / a, etc. Asked. Further, the major axis length and minor axis length of each Si particle were measured, and the average value of the aspect ratio (major axis length / minor axis length) was determined. As a result, the average value of A / a exceeded 4 in the comparative product. On the other hand, in the example product, the average value of A / a was more than 1 and 4 or less. Here, the measurement was performed in a 300 μm × 400 μm measurement visual field.

In addition, an abrasion test and a fatigue test were performed on the example product and the comparative product. The conditions for the wear test are shown in FIG. 4, and the conditions for the fatigue test are shown in FIG. In the wear test, a static load is applied to the inner surface of the bearing, starting and stopping are repeated, and after a predetermined time has elapsed, the amount of wear (μm) is measured. This evaluated abrasion resistance. In the fatigue test, a dynamic load was applied to the inner surface of the bearing, and the maximum surface pressure (MPa) that did not fatigue in a predetermined test time was evaluated as fatigue resistance. The evaluation results are shown in FIG.

First, in order to examine the effect of A / a on wear resistance and fatigue resistance, Example Product 8 and Comparative Product 1 are compared. In Example Product 8, the average value of A / a is A / a = 3.8. This example product 8 had a maximum surface pressure of 80 MPa without fatigue and a wear amount of 18 μm. On the other hand, in the comparative example product 1, the average value of A / a is A / a = 4.3. The comparative product 1 had a maximum surface pressure at which fatigue did not occur was 60 MPa, and the amount of wear was 25 μm. From the comparison between the product of Example 8 and the product of Comparative Example 1, it can be seen that when A / a is 4 or less, the wear resistance and fatigue resistance are superior to those having A / a larger than 4. . As described above, it was confirmed that the example products 1 to 8 having an average value of A / a exceeding 1 and 4 or less have improved wear resistance and fatigue resistance as compared with the comparative example product 1.

Next, in order to examine the influence of the aspect ratio of the Si particles on the fatigue resistance, Example Product 7 and Example Product 8 are compared. Example product 7 has an aspect ratio of Si particles of 2.3. This example product 7 had a maximum surface pressure of 90 MPa, which does not fatigue, indicating fatigue resistance. On the other hand, in Example Product 8, the aspect ratio of Si particles was 2.6, and the maximum surface pressure without fatigue was 80 MPa as described above. From the comparison between the example product 7 and the example product 8, when the aspect ratio of the Si particles is 2.5 or less, the fatigue resistance is better than that having an aspect ratio of more than 2.5. I understand. Thus, it was confirmed that the fatigue resistance was improved by setting the aspect ratio of the Si particles to 1 or more and 2.5 or less.

Furthermore, Example Product 5 and Example Product 6 are compared in order to examine the influence of Si particles adjacent in the thickness direction on wear resistance. In Example Product 5, Si particles adjacent to each other in the range of radius r = B × (A / a) in the thickness direction from the specific Si particles on the surface on the sliding side are “present”. In this example product 5, the amount of wear indicating wear resistance was 12 μm. On the other hand, in Example product 6, Si particles adjacent in the range of radius r = B × (A / a) in the thickness direction from specific Si particles on the surface on the sliding side are “existing”. is there. In Example Product 6, the amount of wear indicating wear resistance was 15 μm. From the comparison between Example Product 5 and Example Product 6, the presence of Si particles that are adjacent in the thickness direction is superior in wear resistance to those that do not have Si particles. I understand. Thus, it was confirmed that the wear resistance was improved by the presence of Si particles adjacent to each other within the radius r in the thickness direction.

As described above, from the results of these wear tests and fatigue resistance tests, it was confirmed that the example products were superior in wear resistance and fatigue resistance compared to the comparative example products.

Claims (4)

1. In an Al-based bearing alloy containing 1 to 15 mass% of Si, when the distance between adjacent Si particles existing on the surface on the sliding side is A and the major axis length of the Si particles is a, A / a An Al-based bearing alloy having an average value of more than 1 and 4 or less.
2. The Al-based bearing alloy according to claim 1, wherein an average aspect ratio of the Si particles existing on the surface on the sliding side is 1 or more and 2.5 or less.
3. Near Si particles having arbitrary specific Si particles present on the surface on the sliding side, and adjacent to the specific Si particles in the thickness direction,
   A radius r centered on the center of gravity of the specific Si particle, where A is the distance to the Si particle adjacent to the specific Si particle on the surface on the sliding side and a is the major axis length of the specific Si particle. R = B × (A / a) (μm)
   a / 2 <B ≦ 20
   The Al-based bearing alloy according to claim 1, wherein the Al-based bearing alloy is present in a range of
4. The Al-based bearing alloy according to claim 1, 2 or 3, characterized by containing one or more of the following (1) to (3).
   (1) The total amount of one or more elements selected from Cu, Zn, and Mg is 0.1 to 7% by mass
   (2) 0.01 to 3% by mass in total of one or more elements selected from Mn, V, Mo, Cr, Co, Fe, Ni and W
   (3) The total amount of one or more elements selected from B, Ti, and Zr is 0.01 to 2% by mass.

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