JPH11193427A - 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, 2-20% Al, 3-10% graphite, and the balance Cu with inevitable impurities. Al has a function of precipitating an extremely hard Sn-Al alloy phase in an alpha solid solution of Cu Zn-Al with high strength and strengthening a matrix. 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 Conventionally, as a bush used for the above applications, a quenched steel bush, a bush made of gunmetal, and the like are known.

[0003]

The above-mentioned conventional hardened bushes made of steel and bushings made of gunmetal have the advantages of being inexpensive and having high strength, but have a high friction coefficient, and have problems of seizure resistance and abrasion 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 Cu-10Zn-7.5Sn based sintered alloy having good wear resistance and adhesion resistance, and have been working to strengthen the matrix of this alloy. When Al is added in an amount of about 5% by weight, high strength Cu
It has been found that a very hard Sn-Al alloy phase precipitates in a network form in the α-solid solution of -Zn-Al and exhibits a pearlite-like structure. Originally, Sn is an element constituting an α solid solution together with Cu and Zn, but it is considered that a part of the element was extracted from the α solid solution due to the presence of Al and was bonded to and precipitated with Al. 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. Further, the amount of Al added and the structure of the structure of the Sn-Al alloy phase are merely examples. The present inventors have further found that by dispersing graphite having excellent self-lubricating properties in the matrix, the sliding characteristics and abrasion resistance are significantly improved in combination with the strengthening of the matrix.

[0005] The present invention has been made based on the above findings, and the weight ratio of Zn: 10 to 30%, Sn: 3 to 1
0%, Al: 2 to 20%, graphite: 3 to 10%, balance 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.

Al: 2 to 20% Al exerts the same addition effect as Zn, and the effect is produced with a smaller amount than Zn (that is, the zinc equivalent is large).
On the other hand, when the content of Zn is increased, the material becomes brittle due to the precipitation of the β phase, but by adding Al, the content of Zn can be reduced and the embrittlement can be suppressed. In addition, a part of Al forms a solid solution in the Cu-Zn matrix to form Cu-Zn-A
1 forms a solid solution, and partly combines with Sn and precipitates as a very hard Sn-Al alloy phase as described above. When the content of Al is small, the Sn-Al alloy phase is network-like, but as the Al content increases, the Sn-Al alloy phase increases.
The proportion occupied by the alloy phase increases and the alloy phase becomes lumpy. That is, A
As the content of l increases, the hardness of the matrix increases and the abrasion resistance improves. The content of Al is
If it is less than 2%, the above-mentioned effects are not sufficient, and 20%
%, The alloy becomes brittle. Further, as described later, in the case where a backing metal is provided with a sintered alloy to perform bending or the like, the content of Al is preferably 10% or less and 5% or less in order to improve workability. Is more preferable.

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, compacted into a predetermined shape, and the obtained compact is sintered to obtain the above-mentioned material. 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. Hereinafter, more preferred embodiments of the present invention will be described.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The copper-based sintered bearing material of the present invention includes:
When the following lubricating components are contained, adhesion resistance and sliding characteristics (low friction resistance) can be further improved. Pb: 2 to 5% Pb hardly forms a solid solution in Cu, and is 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).

[0012]

[Embodiment 1] Hereinafter, the present invention will be described in more detail with reference to specific embodiments. Mix brass-based raw material powder,
The mixed powder was filled in a mold to form a rectangular plate-shaped green compact having a side of 30 mm and a thickness of 5 mm at a pressure of 4 ton / cm ² . Next, the green compact is heated at 780 to 800 ° C. in a reducing atmosphere.
Sintered for 30 to 40 minutes, and subjected to oil impregnation treatment to obtain a plurality of sample Nos. Of the present invention. 4-No. No. 23 was produced. Moreover, the sample No. of the comparative example was similarly prepared from a brass-based raw material powder or a bronze-based powder without adding Al. 1
-No. 3 was produced. The sample No. 3, No.
7, No. Reference numeral 14 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. To distinguish them. Table 1 shows the components of these samples. In addition, the density, hardness, bending strength (sintered bimetal No. 3, No. 7, No. 14) of each sample after sintering.
And the oil content (excluding sintered bimetal No. 3) are shown in Table 2.

[0013]

[Table 1]

[0014]

[Table 2]

As can be seen from Table 2, there is no remarkable difference in the transverse rupture strength between the inventive example and the comparative example. 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 present invention example than in the comparative example, and it can be seen that the matrix is strengthened by the Sn-Al alloy phase.
And, by the increase in hardness, in the example of the present invention, the abrasion resistance is remarkably improved as described below.

No. 1 of the above sintered solids. 1, No.
5, No. 8 and sintered bimetal no. 3, No.
7, No. 10, No. No. 22 was used to conduct a thrust friction test. FIG. 1 shows an outline of a thrust friction test, in which a cylindrical solid test piece is pressed against a sintered solid or sintered bimetal, and the wear rate (depth) of the sample is measured by rotating the test piece. It has become. 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 start of the test to apply a pressure of 50 kgf / cm ² and a friction speed of 4 m / m.
This was performed for 20 hours under the conditions of "in".

FIG. 2 shows the amount of wear of each sample. The sintered solid No. of the comparative example. 1 and sintered bimetal No. 3, the wear amounts were 0.058 mm and 0.033 mm, respectively. 5, No. 8,
No. 10, No. At 22, each is 0.019m
m, 0.012 mm, 0.011 mm, 0.019 m
m, the sintered bimetal No. of the present invention. 0.013m for 7
m, indicating that wear 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 An Al powder and a brass-based raw material powder were mixed, and the mixed powder was uniformly spread 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. 7 was produced. 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. 3 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 an upward load is applied 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 example, the test was performed for 100 hours under the conditions of a pressing force of 100 kgf / cm ² and a friction speed of 5 m / min. Also in this journal friction test, the amount of wear was extremely small, and the friction coefficient was stable at about 0.05.

[0020]

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 diagram showing an outline of a thrust friction test.

FIG. 2 is a diagram showing the amount of friction in a thrust friction test.

FIG. 3 is a diagram showing an outline of a journal friction test.

Claims (7)

[Claims] 1. Zn: 10 to 30% by weight, Sn: 3 by weight ratio
A copper-based sintered bearing material comprising: -10%, Al: 2-20%, graphite: 3-10%, the balance being Cu and unavoidable impurities. 2. The copper-based sintered bearing material according to claim 1, comprising 2 to 5% by weight of Pb. 3. One or two of MoS ₂ , WS ₂ , BN
The copper-based sintered bearing material according to claim 1, wherein the copper-based sintered bearing material contains 3 to 7% by weight of a seed or more. 4. 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. 5. 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. 6. 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 back metal. And sintering the whole, and then subjecting the sintered alloy to rolling processing. 7. A method for producing a copper-based sintered bearing material having 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.