JPH11193428A - Copper-base sintered bearing material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper-base sintered bearing material excellent in sliding characteristic and wear resistance and causing no seizure, etc., in an oilless state even under severe service conditions. SOLUTION: This copper-base sintered bearing material has a composition consisting of, by weight ratio, 10-30% Zn, 3-10% Sn, 1-10% ferroalloy, 3-10% graphite, and the balance Cu with inevitable impurities. Ferroalloy has excellent wettability to a matrix and adheres firmly to the matrix and strengthens it. By this method, the strength and hardness of the matrix can be improved, and sliding characteristic and wear resistance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper-based bearing material suitably used for automobiles, ships, general industrial machines, and the like, and a method for producing the same. In particular, a leaf spring bush for trucks, a tie bar bush for injection molding machines, and the like. The present invention relates to a copper-based bearing material for a bearing used under severe conditions and a method for producing the same.

[0002]

2. Description of the Related Art As a bush for the above uses,
Conventionally, a steel quenching bush, a gunmetal bush, and the like are known.

[0003]

The conventional steel quenched bushes and gunmetal bushes described above have the advantages of being inexpensive and having high strength, but have the problem of high friction coefficient, seizure resistance and wear resistance. In order to solve these drawbacks, the fact is that a forced lubrication is performed by forcibly supplying lubricating oil to a sliding portion with a partner shaft. By the way, in recent years, for the purpose of improving the environment and significantly reducing costs, it has been desired to use oilless or oil-impregnated bearings in bushes used for the above applications. The present invention has been made in view of the above circumstances, and provides a copper-based sintered bearing material having excellent sliding characteristics (low frictional resistance) and adhesion resistance, which can be used even under severe use conditions, and a method for producing the same. It is intended to provide.

[0004]

The present inventors have focused on a brass-based sintered alloy having good wear resistance and adhesion resistance, and dispersed graphite having excellent self-lubricating properties in a matrix of this alloy. Along with dispersing FeB as hard particles,
It has been found that the matrix is strengthened by the hard particles and the abrasion resistance is greatly improved. FIG. 1 shows 97 parts (7
5Cu-5Sn-10Zn-5Pb-5 graphite) -3 parts F
It is a microscope photograph (340 times) showing the structure of the copper-based sintered bearing material (B: 0.65% by weight) having the composition of eB, and the material shown in this photograph applies a pressure of 4 ton / cm ² to the mixed powder. And sintered at 780 ° C. for 30 minutes. As shown in FIG. 1, this material has a structure in which graphite (black portion) and FeB (gray portion) particles are dispersed in a brass-based β-phase matrix.

[0005] The present inventors have studied the dispersion of ceramic particles such as alumina (Al ₂ O ₃ ) for strengthening the matrix. However, since the bonding strength between the particles and the matrix is weak, a considerable effect has been obtained. Was not seen. In order to observe the metal structure of the brass-based sintered alloy in which the alumina was dispersed by the present inventors, when polishing the alloy cross section,
The fact that a large number of alumina particles dropped off from the cross section of the alloy was also observed, which clearly indicates the low bonding strength between the alumina and the matrix. On the other hand, when FeB was dispersed, such a phenomenon did not occur, and no drop-off of particles was observed in the micrograph. The reason why FiB is firmly fixed to the matrix is presumed as follows.

[0006] That is, FeB is represented by B in the Fe crystal lattice.
Has a crystal structure called a hexagonal Levis (Laves) phase. For this reason, it is considered that the characteristics of Fe constituting the main part of the crystal lattice largely appear in FeB in the crystal, and the FeB takes a behavior similar to that of Fe. Since Fe can diffuse into brass, it is presumed that a bonding state similar to diffusion bonding occurs between the FeB particles and the matrix. However, this is merely an estimation, and it goes without saying that the present invention is not limited by the presence or absence of such an action.

According to the study of the present inventors, hard particles are F
In addition to eB, FeTi, FeMo, FeSi, FeC
It was confirmed that r, FeAl, and FeZr exhibited the same abrasion resistance and adhesion resistance. These are ferroalloys which are put into a steelmaking furnace as a deoxidizing agent or a decarburizing agent during steelmaking, and high-purity ones are easily available and are stable in price. In particular, since FeAl has the same body-centered cubic lattice (bcc) as the crystal structure of αFe, it is considered that FeAl is more firmly fixed to the matrix.

The present invention has been made on the basis of the above-mentioned findings, and has a weight ratio of Zn: 10 to 30% and Sn: 3 to 1 by weight.
0%, ferroalloy 1-10%, graphite: 3-10%, the balance being Cu and unavoidable impurities. Hereinafter, the grounds for the numerical limitation will be described. However, in the following description, "%" means "wt%".

Zn: 10 to 30% Zn forms a solid solution with Cu to strengthen the matrix,
It improves the wear resistance of the alloy and the corrosion resistance to degraded oil. If the Zn content is less than 10%, such an effect becomes insufficient, and if the Zn content exceeds 30%, the alloy becomes brittle. Sn: 3 to 10% Sn forms a solid solution with Cu together with Zn to strengthen the matrix and improve the wear resistance of the alloy. If the Sn content is less than 3%, such effects are insufficient, and if the Sn content exceeds 10%, the alloy becomes brittle.

Ferroalloys: Ferroalloys such as 1-10% FeB disperse without dissolving in the matrix and significantly improve the wear resistance of the matrix. However, as described above, simply by mechanically interposing in the matrix like alumina does not strengthen the matrix, so that adhesion (wetting) at the particle interface is important. In this regard, since the ferroalloy is firmly fixed to the matrix, the properties as hard particles are exhibited, and the wear resistance can be significantly improved. If the content of ferroalloy is less than 1%, its effect is not sufficient, and if it exceeds 10%, the alloy becomes brittle.

Graphite: 3-10% Graphite is mechanically dispersed in the matrix and acts as a solid lubricant. In addition, graphite has a high affinity for oil,
The effect is exhibited under the boundary lubrication region. If the content of graphite is less than 3%, the lubricating effect is not sufficient, and
If the content exceeds 0%, the strength of the matrix decreases.

Next, in order to produce the copper-based sintered bearing material of the present invention, the powder is mixed and compacted into a predetermined shape, and the obtained compact is sintered. A sintered body having such a composition is obtained. Further, by integrally providing the sintered alloy as described above on the surface of the steel back metal or the steel back metal having a copper plating on the surface, a copper-based sintered bearing material with supplemented strength can be obtained. . Specifically, on the surface of a steel back metal or a steel back metal having copper plating on the surface,
The mixed powder may be sprayed or a green compact formed from the mixed powder may be placed, and the whole may be sintered and the sintered alloy may be subjected to rolling.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Ferroalloys are FeB, FeT
i, FeMo, FeSi, FeCr, FeAl, FeZ
n, one or more of FeZr, FeW, FeNb, FeV, and FeNi, especially FeTi, FeMo, F
one or two of eSi, FeCr, FeAl, FeZr
While it is preferred to use more than one species, other ferroalloys can also be used.

If the copper-based sintered bearing material of the present invention contains the following lubricating components, adhesion resistance and sliding characteristics can be further improved. Pb: 2 to 5% Pb hardly forms a solid solution in Cu, and is mechanically dispersed as a soft metal in the matrix, contributing to an improvement in adhesion resistance. If the content of Pb is less than 2%, such effects are insufficient, and if the content exceeds 5%, the hardness of the material is reduced.

Any one of MoS ₂ , WS ₂ , and BN
The sliding properties can be further improved by containing 3 to 7% of the species or two or more species in total. Especially,
MoS ₂ is suitable because it is dispersed in the matrix and works synergistically with the lubricating oil to improve the sliding properties. However,
When the content of the lubricating component exceeds 7%, the strength of the material decreases. The copper-based sintered bearing material of the present invention may be a sintered body alone (sintered solid), or may be formed on a steel back metal or a steel back metal having copper plating on its surface as described above. It may be one in which a sintered alloy is integrally provided (sintered bimetal).

[0016]

The present invention will be described below in more detail with reference to specific examples. [Example 1] Various ferroalloy powders and brass-based raw material powders were mixed, and the mixed powders were filled in a mold to obtain 4 ton / cm ^2.
A 30 mm-square, 5 mm-thick, rectangular plate-shaped green compact was formed at the pressure described above. Next, the green compact is 780-700 in a reducing atmosphere.
Sintered at 800 ° C. for 30 to 40 minutes, and subjected to oil impregnation treatment to obtain a plurality of sample Nos. Of the present invention. 4-No. 20 were produced. Further, the sample No. of the comparative example was prepared from a brass-based raw material powder or a bronze-based powder in the same manner as described above without adding the ferroalloy powder. 1 to No. 3 was produced. The sample No. Reference numeral 3 denotes a clad material obtained by spraying and sintering a raw material powder on a backing metal as described later, and performing a rolling process on the clad material. To distinguish them. Table 1 shows the components of these samples. Also, the density, hardness, bending strength (excluding sintered bimetal No. 3, No. 19 and No. 20) and oil content (excluding sintered bimetal No. 3) of each sample after sintering are shown. 2
Shown in

[0017]

[Table 1]

[0018]

[Table 2]

As can be seen from Table 2, there is no remarkable difference between the present invention and the comparative example regarding the bending strength. Further, the oil content of the example of the present invention is equal to or higher than that of the comparative example, and thus it is understood that the example has a function as an oil-impregnated bearing. On the other hand, the hardness is generally higher in the examples of the present invention than in the comparative examples, indicating that the matrix is reinforced by the ferroalloy particles.
Then, due to the increase in the hardness, in the example of the present invention, the sliding characteristics and wear resistance are remarkably improved as described below.

Among the above sintered solids, No. 1, No.
5, No. 7 and sintered bimetal No. 7 3 was used to conduct a thrust friction test. FIG. 2 shows an outline of a thrust friction test. A cylindrical test piece is pressed against a sintered solid or a sintered bimetal, and the test piece is rotated to change the friction coefficient with time and the wear amount of the sample ( Depth). In this example, SUS304 material was used as a mating test piece, and a lithium-based grease was slightly applied to the mating test piece surface before the test was started.
0 kgf / cm ² and a friction speed of 4 m / min.
Time went.

FIG. 3 shows the change with time of the friction coefficient of each sample. The sintered solid No. of the present invention example containing FeB or FeTi. In Nos. 4 and 5, the friction coefficient stably changed and was at most about 0.15, indicating that the sliding characteristics were extremely good. On the other hand, the sintered solid No. 1 and sintered bimetal No. 3, the coefficient of friction is as high as 0.2 or more.
o. In No. 3, the friction coefficient rose sharply immediately after the start of the test and immediately before the end of the test, indicating an unstable transition.
In addition, as is clear from the wear amount shown in FIG. 4, it is understood that the wear of the example of the present invention is extremely small. As described above, in the present invention, it was confirmed that the sliding characteristics and abrasion resistance were remarkably improved, and there was no fear of occurrence of seizure or the like.

[Example 2] FeB powder and brass-based raw material powder were mixed, and the mixed powder was uniformly dispersed on a Cu-plated steel sheet so as to have a predetermined layer thickness. And sintered at 780-800 ° C. for 10-30 minutes. Next, the sintered layer of the sintered plate thus obtained was densified by a rolling roll, and further subjected to secondary sintering to obtain a sintered layer having a thickness of 2.0 mm and an overall thickness of 3 mm. No. of Table 1 of 0.0 mm. A sintered bimetal having the composition shown in FIG. This sintered bimetal is bent to an inner diameter of 40 mm,
A bearing bush having an outer diameter of 46 mm and a length of 30 mm was produced. Then, a journal friction test was performed using this bearing bush.

FIG. 5 schematically shows a journal friction test, in which a shaft is passed through a bearing bush and the shaft is rotated for a predetermined time while applying an upward load to the bearing bush.
The change with time of the friction coefficient and the wear amount (depth) of the bearing bush are measured. In this embodiment, the pressing force 1
Under the conditions of 00 kgf / cm ² and a friction speed of 5 m / min.
Run for 00 hours. In this journal friction test,
The amount of wear was extremely small, and the friction coefficient was stable at about 0.05.

[0024]

As described above, according to the present invention, excellent sliding characteristics and abrasion resistance as well as excellent anti-adhesion properties are obtained, and even under severe operating conditions, seizure can occur without lubrication. In addition, the bearing performance can be sufficiently exhibited for applications such as a leaf spring bush for trucks.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a structure of a copper-based sintered bearing material of the present invention.

FIG. 2 is a diagram showing an outline of a thrust friction test.

FIG. 3 is a diagram showing a transition of a coefficient of friction in a thrust friction test.

FIG. 4 is a diagram showing the amount of friction in a thrust friction test.

FIG. 5 is a diagram showing an outline of a journal friction test.

Claims (8)

[Claims] 1. Zn: 10 to 30% by weight, Sn: 3 by weight ratio
-10%, ferroalloy 1-10%, graphite: 3-10
%, The balance being Cu and unavoidable impurities. 2. The ferroalloy is made of FeB, FeT.
i, FeMo, FeSi, FeCr, FeAl, FeZ
The copper-based sintered bearing material according to claim 1, comprising one or more of n, FeZr, FeW, FeNb, FeV, and FeNi. 3. The copper-based sintered bearing material according to claim 1, comprising 2 to 5% by weight of Pb. 4. One or two of MoS ₂ , WS ₂ and BN
The copper-based sintered bearing material according to any one of claims 1 to 3, wherein the material contains 3 to 7% by weight of a seed or more. 5. A copper-based sintered bearing material, wherein the sintered alloy according to claim 1 is integrally provided on a surface of a steel back metal. 6. A method for producing a copper-based sintered bearing material having the sintered alloy according to claim 1 as a sliding member, wherein the powder is mixed and compacted into a predetermined shape. And sintering the obtained green compact to produce a copper-based bearing material. 7. A method for producing a copper-based sintered bearing material having the sintered alloy according to claim 1 as a sliding member, wherein a mixed powder is sprayed on a surface of a steel backing metal. And sintering the whole, and then subjecting the sintered alloy to rolling processing. 8. A method for producing a copper-based sintered bearing material comprising the sintered alloy according to claim 1 as a sliding member, comprising forming a mixed powder on a surface of a steel back metal. A method for producing a copper-based bearing material, comprising placing a compact that has been compacted and sintering the entire compact.