JPH0693360A - Al-sn bearing alloy material - Google Patents

Abstract

PURPOSE:To improve the seizing resistance of an Al-Sn bearing allay by forming the distributing shape of Sn in the Al-Sn bearing allay into a three-dimensionally reticulate one and forming the reticulate, connecting parts into Sn banks. CONSTITUTION:The bearing alloy material is constituted of an Al-Sn allay cast by a vertical casting machine. The structure of the distributing state of Sn in this alloy is formed into a one connected into a three-dimensionally reticulate shape. Then, the Al-Sn bearing allay material is incorporated with, by weight, 3.0 to 25% Sn, 0.1 to 11% Si and one or more kinds among Zr, V, Cr and Mn by 0.1 to 3.0% alone or in total as well as incorporated with 0.01 to 0.3% Ti and 0.005 to 0.05% B, and in which the ratio of Ti/B is regulated to 5 to 20. The alloy material is incorporated with 0.001 to 0.1% Sr or Sb. Moreover, 0.2 to 5% Pb is incorporated therein. In this way, the durability of the bearing can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-Sn bearing alloy material, and more specifically, it has a structure in which the distribution state of Sn in the alloy is three-dimensionally connected in a mesh-like shape, and a mesh-like connecting portion. Is a suitable Sn retention structure, and particularly relates to an Al-Sn bearing alloy material having excellent seizure resistance during high-speed / high-load operation.

[0002]

2. Description of the Related Art Recent automobile engines are fuel-efficient and high-powered, and the load applied to the bearings is accordingly increased, and the temperature of the lubricating oil is also raised, sometimes even under boundary lubrication conditions. However, the operating conditions of bearings are becoming severer. Further, in recent years, a Kelmet type high lead bronze alloy bearing that uses a lead type overlay on the surface such as using methanol as a fuel has a problem in corrosion resistance, and a more stable Al--Sn type Bearing alloys and bearings with excellent load bearing capacity have been required.

That is, a bearing having an overlay plating layer on the surface thereof is generally in accordance with JIS 5402, AJ-.
1 (10% Sn, 0.75% Cu, 0.5% Ni, Al
Bal), JIS H 5402, AJ-2 (6% S
n, 2.5% Cu, 1.0% Ni, AlBal) etc. J
IS standard, SAE780 (6% Sn, 2% Si, 1% C
u, 0.5% Ni, 0.1% Ti, AlBal) and other S
As shown in the AE standard, the bearing alloy part is made of a low Sn-Al alloy having a relatively low Sn content.
A surface area is further formed on the surfaces of these bearing alloy portions by overlay plating of a Pb-Sn alloy, and this surface area constitutes a bearing surface. However, these bearings
Under high load and high temperature use conditions in recent years, the surface layer of the surface is overwhelmed by abrasion, causing seizure, which makes it unusable. On the other hand, the surface is over
Bearings that do not form a surface area by lay plating are SAE7
83 (20% Sn, 0.5% Si, 1.0% Cu, 0.
1% Ti, AlBal), the bearing alloy portion is made of a high Sn-Al alloy having a high Sn content. However, the alloy containing a large amount of Sn, such as about 20%, has a low hardness and the Al matrix becomes weak, so that it cannot withstand a high load.

Al-S is used regardless of the Sn content.
A bearing alloy having seizure resistance by adding Pb to an n-based alloy to improve lubricity is described in, for example, "Bearing Alloy", page 139, published by Nikkan Kogyo Shimbun in 1929 by Junichi Mizuno,
This bearing alloy is 10% Sn, 1.5% Cu, 0.5% S
Al-Sn- containing i and 3% Pb
It is a Pb-based alloy.

Further, since Pb in the Al-Sn-Pb type alloy hardly forms a solid solution with Al, P which is this lubricating component.
Al-Sn-Pb with Sb added to improve the dispersibility of b
A -Sb alloy is described in Japanese Examined Patent Publication No. 52-12131, and on top of this, Al-Sn in which coarsening of Sn particles is prevented.
A -Si-Cr alloy is disclosed in Japanese Patent Publication No. 61-40297.

All of these bearing alloy technologies are intended to relatively increase the matrix strength of the alloy and secure the fatigue resistance by reducing and dispersing the lubricating component. However, the increase in the strength of these alloys and the improvement in the wear resistance, and thus the improvement in the seizure resistance are inherently largely due to the addition of Si, and among Al-Sn alloys, Al-Sn alloys and Al alloys It should be distinguished from the -Sn-Si system, and the effect of Si addition should be sufficiently distinguished and understood.

Incidentally, a conventional example (Japanese Patent Publication No. 61-4029)
No. 7), Sn and Sn by adding Cr and Si.
It is said that the particles are refined and the hardness is improved. As a result, there is almost no movement and growth of Sn in a high temperature state, and the decrease in high temperature hardness is small.

That is, the flow of conventional bearing alloys is summarized as follows: Al-Sn binary system, which is a soft alloy system containing 40 to 20 wt% of Sn and having an extremely high lubricating power, with a reduced Sn content and added Si or the like. , The matrix has been strengthened. What we should pay attention to here is how we have dealt with the problem that the lubrication force must be reduced due to the strengthening of the matrix. It is the fact that Cr was added, and the dispersion of Sn was measured by doing so.

Further, as a conventional example, Japanese Patent Publication No. 2-352020 and Japanese Patent Laid-Open No. 62-21853 disclosed by the applicant of the present invention.
According to Japanese Patent Laid-Open No. 8 (1994), a small amount of Sr or Sb is added to an Al-Sn alloy containing Si to uniformly deposit Si particles, which are matrix strengthening elements, in a spherical shape, an elliptical shape, or a shape close to the spherical shape. There is known a technique for improving seizure resistance without lowering the lubrication force by allowing the formed Si particles to exist on the surface of the matrix and the Sn—Pb alloy particles in the vicinity of the Si particles. There is. However, there is a problem that the lubricating effect of Sn of these Al-Sn based alloys is not sufficient.

[0010]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and specifically, it is possible to impart maximum seizure resistance with a small amount of Sn component in an Al-Sn alloy material. An object is to provide a Sn-based bearing alloy material.

[0011]

The present invention is an Al-Sn bearing alloy material cast by a vertical casting machine, in which the distribution state of Sn in this alloy is three-dimensionally connected in a mesh structure. And has a structure in which the mesh-shaped connecting portion is an appropriate Sn retention.

The present invention makes a basic study on the way of lubrication of such Al--Sn system Sn, and in view of the prior art that merely focuses on the dispersion effect of Sn, a more effective S
The seizure resistance is improved by determining the distribution state of n.

The structure and operation of the means of the present invention will now be described in detail with reference to the drawings.

That is, the present invention has sought a fundamental solution as to what method should be taken to secure the maximum seizure resistance with a small amount of lubricating components.

FIG. 1 is an explanatory view showing a relationship between a bearing material in a lubricated state and a shaft, FIG. 2 is a schematic view of a structure model for explaining the structure of the bearing alloy material of the present invention, and FIG. 3 is according to the present invention. A
FIG. 5 is a schematic diagram of a microstructure model during casting of an 1-Sn alloy material, FIG. 4 is a schematic diagram of a solidification model of vertical casting, and FIG.
Is a schematic diagram of a solidification model of horizontal casting, and FIG.
It is a schematic diagram of the tissue model explaining the cross section of a Sn type | system | group communication pipe part, FIG. 7 is a schematic diagram which heat-processed FIG. 6, and FIG. 8 is A.
9 is an explanatory diagram showing the relationship between l and Sn wetting properties, FIG. 9 is an explanatory diagram when the wetting property of FIG. 8 is good, and FIG. 10 is an explanatory diagram when the wetting property of FIG. 8 is bad. Reference numeral 1 is an axis, 2 is an S
n, 3 are Al-Sn type bearing alloys, 4 is back metal, 6 is Sn perspiration part, 10 is carbon mold, 11 is liquid phase (Sn),
12 is a solid-liquid interface, 13 is a solid phase, 31 is a communicating tube part, 32 is Sn retention, 33 is an Al matrix part, 34 is a petal-like tissue (Al), and 35 is a grown crystal.

As shown in FIG. 1, Al-Sn bearing alloy 3
On the verge of seizure on the shaft 1, that is, in the state under boundary lubrication, to secure the lubricity by Sn indicated by reference numeral 2 means that the lubrication component is present at the interface under the metal contact between the shaft 1 and the bearing alloy 3. A certain amount of Sn is supplied, iron of shaft 1 and bearing alloy 3
This means that aluminum adhesion is avoided.
In other words, improving the seizure resistance means improving the supply capability of Sn (liquid phase) to the seizure interface. That is, the Al-Sn bearing alloy 3 having improved seizure resistance means that the distribution state of Sn in the Al-Sn alloy is S on the surface.
It can be said that the bearing is in an excellent state of supplying n.

Looking back, in the conventional Al-Sn bearing alloy, in order to secure matrix strength, Sn is rather divided, granulated and further subdivided. In this state, only the Sn particles existing on the outermost surface of the bearing contribute to the seizure property, and the Sn inside has no meaning at all.

The distribution state of Sn described in the present invention means that Sn phases are three-dimensionally connected in a mesh shape as shown in FIG. An appropriate Sn residue 32 that serves as a source of Sn is connected to the communication pipe section 3
Must have 1. Here, the appropriate Sn retention means a portion having a larger cross-sectional area than at least the communicating tube portion and having a sufficient volume to supply a large amount of Sn liquid phase to the surface during Sn melting. It is necessary to combine these two conditions. When the surface causes metal contact and locally reaches a critical situation that exceeds the melting point of Sn, Sn melts and at the same time causes a sweating phenomenon, through a three-dimensional network,
The Sn liquid phase is supplied and avoids fatal seizure.

Such an ideal Sn distribution state is represented by Al-
It is within the scope of the present invention how the Sn distribution state of this bearing alloy should be made to appear in the plain bearing of the Sn alloy.

That is, Sn in the final bearing product
The distribution of S is originally S in AS CAST (as-cast casting)
This is a form resulting from the synergistic effect of Sn behavior in the subsequent rolling and heat treatment steps on the n-phase precipitation state, and the Sn distribution in the state where Sn is connected in the final product at any stage and Sn residue 32 is present. Therefore, what kind of manufacturing method is appropriate should be examined.

First, in the casting structure, a three-dimensionally uniform Sn network structure and an appropriate Sn retention 32
The optimum casting conditions for the provision of Ti are, as shown in FIG.
Growing petal-like crystals using -B as a nucleating agent,
A relatively large Sn retention 32 around the petal-like tissue 34
It has been found that controlled coagulation is suitable for the uppermost conditions so that Moreover, in order to solidify such free crystals without directivity, a casting by a vertical casting machine is suitable, and a casting using a general casting machine of a horizontal type is inevitably a directional casting with a strong directivity. The same three-dimensional network regardless of the cross section like vertical casting.
It is difficult to obtain a textured Sn distribution structure.

The difference between the vertical casting method and the horizontal casting method is not limited to the formal dimension of the method of pulling the casting vertically from the carbon mold shown in FIG. 4 and the method of pulling the casting horizontally as shown in FIG. , The solidification morphology inside the mold is completely different, and in particular, in the alloy system containing a large amount of solute such as Sn and Pb as in the alloy system of the present invention, a completely different morphology is observed as a result.

That is, in the vertical casting method, the solidification direction of the liquid phase 11 and the casting direction are on the same vertical axis, and the mold 10 is used.
The heat removal from the mold is also symmetrical, and since the casting that has become the solid phase 13 immediately after solidification due to the solidification shrinkage of the casting separates from the mold 10,
The grown crystal 35 at the solid-liquid interface 12 becomes a free crystal (having no directivity). On the other hand, in the horizontal casting method, the solidification direction of the liquid phase 11 and the casting direction are not on the same axis, the lower surface of the casting is kept in contact with the mold 10 immediately after solidification, and a void is formed in the upper surface of the mold 10. Therefore, the cooling from the lower surface is prioritized, so that the morphology of the grown crystal 35 also becomes directional.

Further, since the specific gravity of Sn and Pb is several times larger than that of Al and tends to settle on the lower surface during solidification, Sn and Pb are easily segregated on the lower surface in the horizontal casting method, and the directional growth described above occurs. Large segregation is created at the grain boundaries of crystals. On the other hand, vertical castings are Sn, P
Since the sinking direction of b and the casting direction are the same, such S
Segregation of n and Pb does not occur, and Sn and Pb are solidified in a uniform and three-dimensionally connected state in the gap of the uniformly solidified free crystal. That is, the structure required by the present invention requires the structure of this vertical casting.

The three-dimensionally connected structure is originally formed in the solidification process of free crystals. That is, in the nucleated free crystal, ideally several dendrite cells gather,
The appearance is spherical. The spherical aluminum crystal also contains a thin Sn phase in the cell-to-cell gap in the cross section, but most of the remaining Sn phase is extruded to the front surface of the spherical dendrite cell aggregate, and as a final solidification part. It will solidify in the space between the spheres. Therefore,
The communicating tube portion in FIG. 2 is a portion where the cross section of the Sn phase that fills the gap between the spheres is narrow, and when the solidification morphology is a free crystal, three-dimensionally dispersed nuclei are generated, so the final The Sn phases in the solidified portion are connected and exist.

On the other hand, the Sn connecting pipe portion 31 connecting the Sn staying 32 and the Sn staying 32 has a triangular cross-section as shown in FIG. 6, and rolling and heat treatment are repeated. Each time it is returned, the behavior of Sn such that the corners degenerate and the surface area decreases as shown in FIG. 7 is observed. In the present invention, attention was paid to the behavior of Sn of the communicating pipe portion 31, and as a result of repeated experiments, the degree of degeneration of the communicating pipe portion 31 of Sn and the Sn
It was found that there was a correlation with the amount of the sweating part 6 of No. 3, and the degree of degeneration thereof was due to the wetting property (wet angle) of the aluminum matrix 33 and Sn. That is, as shown in FIG. 8, FIG. 9 and FIG. 10, the wettability with the Sn liquid phase differs depending on the third additive element shown in Table 1 which constitutes the aluminum matrix 33, and the continuity depends on the size of the wettability. It was found that the degree of shrinkage of the tube portion was different, and as a result, the starting force for pushing the Sn liquid phase onto the bearing surface was obtained.

Further, this aluminum matrix and S
The same can be said of the problem of wettability of n during solidification of a casting. In the relationship between the aluminum cell nucleated as a primary crystal and the Sn liquid phase, the third additive element (Zr, V, Cr, Mn, etc.)
When added within the solid solubility limit of aluminum, the wettability with the Sn liquid phase deteriorates, so the Sn liquid phase that tends to grow spherically and stay in the gap between the cells should be pushed out to the front more strongly. Therefore, the structure which is three-dimensionally connected and has an appropriate Sn retention is promoted even in the casting stage.

[0028]

[Table 1]

That is, the wetting property of the Sn phase and the aluminum matrix obtained in the range of the present invention is liable to be easily tin-sweated (the direction of increasing the degree of degeneration of the communicating pipe portion).
It was confirmed that Zr, V, Cr, Mn, etc. were confirmed as the third additive element that works for the. Therefore, when the bearing surface is damaged and the bearing itself is exposed to high temperature due to frictional heat,
The phenomenon of extruding Sn on the surface, which is observed during the heat treatment, occurs. That is, the Sn staying of the bearing alloy and the communicating pipe portion connected to the bearing alloy are degenerated in an attempt to reduce the surface area, and as a result, Sn is squeezed out. The purpose of the present invention is to reduce the surface area of the alloy, that is, the change in the alloy to reduce the surface area by the third additive element in the form of wettability so as to make the movement of Sn more effective. Is. The reasons for limiting the addition amounts of the respective elements that make the above effects effective are as follows.

First, it is ideal that the third additive element is not a compound but is in a solid solution state. The solid solution limit of each element in aluminum is 0.28% Zr and 0.37 V.
%, Cr 0.77%, Mn 1.82%, Mn
The solid solution limit of is relatively large, but it is not necessary to add it up to the maximum solid solution limit in order to avoid formation of a compound contained in the Al alloy and inevitably present in Fe. In the present invention, the addition range that can most effectively improve the wettability of Sn is sufficient, and one or two or more of these are set to a range of 0.1 to 3.0% as a simple substance or a total amount.

As a heterogeneous nucleating agent, addition of Ti-B, which is effective for producing a petal-shaped casting structure, the compounds serving as nuclei (TiAl ₃ and TiB ₂ ) are uniformly dispersed and a coarse compound is formed. In order to prevent growth, the Ti content should be 0.01-
0.3%, B content 0.005-0.05%, and Ti /
It is most effective to keep the ratio of B within the range of 5 to 20. When the ratio of Ti and B is reversed or when B is contained in an amount of 0.05% or more, a coarse high-melting point Ti-B compound is generated, and each of Al-Ti and Ti-B compounds that should form fine nuclei. Aggregation is promoted, which rather inhibits the formation of uniform petaloid nucleus in the present invention.

The amount of Sn required for the bearing alloy is 3%.
In the following, it is difficult to form a communicating pipe according to the present invention, and if it is 25% or more, Sn retention becomes continuous in a network structure with too much Sn, and the matrix strength cannot be maintained. And

The amount of Si is basically in the hypoeutectic range, and in order to finely disperse Si in the aluminum matrix, the range of 0.1 to 11% is the preferred range of the present invention.

That is, according to the present invention, in order to improve the seizure resistance of the Al--Sn type bearing material, it is not necessary that the structure of Sn is merely dispersed, but in the use condition of being assembled in the engine,
As a structure capable of supplying Sn to the surface of the bearing, a structure having a three-dimensional network structure and a connecting pipe portion connecting Sn retentions is proposed. As a solution means, alloy casting by a vertical casting method is essential. Is the condition.

Further, (1) Ti and B are added to improve the precipitation morphology of Sn in the cast structure. (2) Zr, V, Cr, and Mn are selectively configured as a wetting modifier for Sn and aluminum matrix. (3) Add Pb as a lubricating component. (4) Add 0.001 to 0.1% by weight of Sr or Sb. In this case, the essential constitution of Si and Pb is very effective in improving the seizure resistance.

The addition of a small amount of Sr or Sb causes the Si particles, which are the matrix-strengthening element, to be uniformly precipitated in a spherical shape, an elliptical shape or a shape close thereto, and the precipitated S
It is possible to improve the seizure resistance without lowering the lubrication force because i-particles are present on the surface of the aluminum matrix and Sn-Pb alloy particles are present in the vicinity of the Si particles. In this case, the addition amount of Si is 1.0 to 11% because Sr or Sb acts on Si.
Is desirable.

Although the addition amount of Sr or Sb is effective even if the amount is very small, the lower limit is 0.001% for control purposes, and the upper limit is 0.1% at which the same effect is sustained and no negative side appears. By configuring in addition to (1) and (2),
An Al-Sn bearing material having more desirable seizure resistance can be obtained.

[0038] Next, examples of the present invention will be explained, but all% in the specification are shown by weight%.

[0039]

EXAMPLE First, an Al—Sn bearing alloy having the composition shown in FIG. 2 was manufactured as a cast billet material (plate material) by a horizontal casting machine for a conventional product, and a vertical casting machine was manufactured for the product of the present invention. A cast billet material (plate-shaped material) was manufactured by the above method, and the upper and lower surfaces of each cast billet were chamfered, and then cold-rolled to about 2 mm. In this state, heat treatment was performed to remove the strain, and thereafter, it was pressed onto the iron plate of the back metal through a thin plate of pure Al to obtain a bearing material having a thickness of 1.5 mm.

Of these bearing materials, Sample No. 1 to N
o. Reference numeral 10 is a conventional test material manufactured by a horizontal casting machine and containing no B or Sr. Sample No. 11-No. Two
6 is a test material according to the present invention, which was cast by a vertical casting machine. Sample No. 11-No.
14 and Sample No. 19-No. Sample No. 22 contains Ti and B. 15-No. 18 and sample No.
23-No. No. 26 is formed by adding Ti, B and Sr or Sb.

To examine the seizure resistance of these composite bearing materials, a Suzuki type seizure limit load tester was used to carry out the test. The results are shown in Table 2 together with the composition.

[0042]

[Table 2]

Next, the test method will be described.

The seizure test conditions are as follows. Friction speed 4m / sec Phase material Material S45C Hardness HRC55 Surface roughness 0.8-1.0S Oil used SAE 20W-40 Oil temperature 150 ° C ± 5 ° C Baking load 20Kgf to 10Kgf Surface pressure every 15 minutes in steps Was raised, and the surface pressure at which seizure occurred was taken as the seizure load. Note that the temperature of the material is 180 ° C for the judgment of seizure
Or the frictional force exceeded 25.5 Kgf.

According to the test results, the sample No. 11-N
o. 26 of the present invention show good seizure resistance as compared with the conventional example, Ti and B are added by the vertical casting method, and further, Cr, Mn, V which are aluminum matrix strengthening elements, Zr is more effective than conventional products in S
It can be understood that the n-structure acts as a good lubricating structure. Further, it is shown that a better lubricating state can be obtained by adding Sr or Sb.

[0046]

As described above, the present invention is an Al-Sn bearing alloy material cast by a vertical casting machine, and the distribution state of Sn in this alloy is three-dimensionally connected in a mesh shape. It is characterized by having the above-mentioned structure and having a structure in which the mesh-like connecting portion is an appropriate Sn retention.

Assembling the bearing alloy material of the present invention into an engine,
Even when the oil film is broken due to contact with the shaft during high load operation, Al containing the same amount of Sn as the conventional product
Compared to the -Sn alloy, the Sn component in the Al-Sn bearing alloy has an original function of Al-S so that it has seizure resistance.
Since the structure of the n-based alloy material is a three-dimensional structure and is easily supplied to the surface of the bearing alloy material, the effect of improving seizure resistance is also the result of improving the durability of the bearing.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between a bearing material in a lubricated state and a shaft.

FIG. 2 is a schematic diagram of a microstructure model for explaining the microstructure of the bearing alloy material of the present invention.

FIG. 3 is a schematic diagram of a microstructure model during casting of an Al—Sn alloy material according to the present invention.

FIG. 4 is a schematic diagram of a solidification model of vertical casting.

FIG. 5 is a schematic diagram of a solidification model of horizontal casting.

FIG. 6 is a schematic diagram of a tissue model for explaining a cross section of an Al—Sn system communication pipe portion.

FIG. 7 is a schematic view of FIG. 6 after heat treatment.

FIG. 8 is an explanatory diagram showing the relationship between the wettability of Al and Sn.

FIG. 9 is an explanatory diagram when the wetting property of FIG. 8 is good.

FIG. 10 is an explanatory diagram when the wetting property of FIG. 8 is poor.

[Explanation of symbols]

 1 shaft 2 Sn 3 Al-Sn bearing alloy 4 back metal 6 Sn sweating part 10 carbon mold 11 liquid phase (Sn) 12 solid-liquid interface 13 solid phase 31 communicating pipe part 32 Sn retention 33 Al matrix part 34 petal Structure (Al) 35 grown crystal

Claims (4)

[Claims] 1. An Al-Sn bearing alloy material cast by a vertical casting machine, wherein the distribution state of Sn in the alloy is 3 or less.
An Al-Sn based bearing alloy material having a three-dimensionally meshed structure and having a structure in which the mesh-shaped connecting portion is an appropriate Sn retention. 2. The Al-Sn bearing alloy material contains at least 1% or more of 3.0 to 25% Sn, 0.1 to 11% Si, and Zr, V, Cr, and Mn in weight%. It contains 0.1 to 3.0% by weight or in a total amount, and 0.
The Al-Sn bearing alloy material according to claim 1, which contains 01-0.3% Ti and 0.005-0.05% B, and has a Ti / B ratio of 5-20. 3. The Al—Sn based bearing alloy material according to claim 2, wherein the Al—Sn based bearing alloy material contains 0.001 to 0.1% by weight of Sr or Sb. 4. The Al-Sn based bearing alloy material according to claim 2 or 3, wherein the Al-Sn based bearing alloy material contains 0.2 to 5% by weight of Pb.