JP2535649B2 - Self-lubricating sliding material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a self-lubricating sliding material having lubricity even without oil supply.

[Conventional technology]

Sliding materials in which a solid lubricant such as graphite, MoS ₂ or BN is dispersed in a sintered body of metal powder such as Cu, Fe or W is known as a self-lubricating sliding material that has lubricity even without lubrication. There is. The mechanism of this self-lubrication is explained as follows.

When the sliding surface is worn to some extent during sliding, the solid lubricant is exposed and supplied onto the sliding surface, and the solid lubricant is spread to form a film of the solid lubricant.

However, when this sliding material is obtained as a sintered body, the metallographic structure of the sintered body is generally porous and
It has about 10 to 25% pores, and these pores are a major cause of strength reduction. Further, in the molding process, there is a so-called notch phenomenon in which a difference in springback amount between the metal powder and the solid lubricant or a springback of the solid lubricant itself causes a gap between the solid lubricant and the matrix of the sintered body. It is unavoidable that the surface pressure resistance is deteriorated. Therefore, the present inventors previously developed a technique for increasing the strength by infiltrating Cu-Co-based and Cu-Mo-based infiltrants into the voids and the sintering resistance holes, and described above. The tendency was canceled.

[Problems to be Solved by the Invention]

However, since the infiltrant as described above is relatively soft, the infiltrant appears and spreads on the sliding surface when sliding under a high surface pressure, and finally seizes and adheres to the sliding surface. I understand. In such a state, the supply of this solid lubricant from the solid lubricant to the sliding surface is obstructed, the replenishment balance becomes unbalanced, and the lubrication function becomes uneven, causing abnormal noise. Was accompanied. In other words, there was a problem with the sliding characteristics under high surface pressure. Also,
Since the infiltration temperature is relatively high at about 1100 ℃, Fe in the sintered body
The reactivity with solid lubricants, especially graphite, increased, and cementite phases tended to form around graphite particles. Since this cementite phase is extremely hard, it was feared that the mating material such as the shaft would be damaged. As a countermeasure against this, MoS ₂ , WS ₂ , BN, etc. were sometimes used instead of graphite for the solid lubricant. But these MoS ₂ , WS ₂ , BN
In addition to being much more expensive than graphite, MoS ₂
There was a problem that S still easily reacts with Fe at high temperatures with respect to WS ₂ and WS _2, and it was difficult to granulate S used as a lubricant for BN.

In order to solve such a problem, the present invention has excellent self-lubricating property because the solid lubricant can be smoothly supplied to the sliding surface even during sliding under high surface pressure. It is to provide a self-lubricating sliding material.

[Means for Solving the Invention]

In the self-lubricating sliding material according to the present invention, the infiltrant is improved in view of the above-mentioned point, and a relatively hard β- or γ-phase Cu-Sn intermetallic compound having good wettability with the Fe-based sintered body is used. In addition to this, it was decided to use an infiltrant containing Pb which is soft and rich in lubricity.

In short, the self-lubricating sliding material according to the present invention has an Fe-based sintered body containing a solid lubricant dispersed in an amount of 10 to 50 vol% in an amount of 15 to 4
Characterized by infiltrating an infiltrant of a Cu-based alloy material mainly containing a β- or γ-phase Cu-Sn intermetallic compound containing 0 wt% Sn and further containing 3 to 40 wt% Pb. Is.

The Fe-based sintered body used in the present invention, Fe, a metal powder such as an Fe-based alloy, a solid lubricant, and an additive such as carbon according to the purpose are mixed, molded and sintered by a usual method. It is obtained by doing. As the solid lubricant, graphite, MoS _2, WS _2, a BN or the like are all usable, preferably is used which was granulated to about 30Myuemu～1000myuemu. Also, graphite coated with water glass can be used. The appropriate amount of this solid lubricant is 10 to 50 vol% of the sintered body. If it is less than 10 vol%, stable lubricity cannot be obtained as an oil-free sliding material. Cannot be secured.

Even if the amount of the solid lubricant is within the above range, the strength of the sintered body in which the solid lubricant is dispersed is still inferior to that of the sintered body without the solid lubricant. Therefore, in order to obtain a mechanical member with higher strength self-lubricating slidability, the area near the sliding surface should have a two-layer structure, and the layer on the sliding surface side (in the case of bushing, the inner diameter Layer) composed of a sintered body in which a solid lubricant is dispersed, and a backing layer (outer diameter layer in the case of a bush) for covering and reinforcing the sintered body is a high-strength sintered body having no lubricant. It can also be configured with. In this case, if the shrinkage during sintering is taken into consideration, the backing layer, for example, the outer diameter layer, is also made of Fe.
It is preferably formed by sintering a system powder or the like.

Furthermore, in order to improve the wear resistance of such a Fe-based sintered body, it is effective to disperse oxide-based ceramic particles such as Al ₂ O ₃ , corundum, mullite, and SiO ₂ .
The amount of this oxide ceramic is 0.5 vol% of the Fe sintered body.
The above is effective, and 5 vol% or less is appropriate in consideration of the strength of the sintered body or the attackability against the mating material.

The infiltrant used in the present invention is a β- or γ-phase Cu-
It is a Cu-based alloy material mainly composed of an intermetallic compound of Sn. In this Cu-based alloy material, the composition of Cu and Sn forms a hard and brittle β- or γ-phase intermetallic compound in the composition in which Sn is in the range of 15 to 40 wt%. Therefore, in the present invention, the infiltrant is formed by blending Pb, which is soft and rich in lubricity, with the β- or γ-phase Cu-Sn intermetallic compound. The amount of Pb is 10 to 25 vol% in the sintered body.
Considering its presence, it is selected to be 3-40 wt% of the total infiltrant. If it is less than this range, stable lubricity cannot be obtained, and if it is more than this range, the strength of the matrix of the sintered body decreases.

The method of infiltrating such an infiltrant into the Fe-based sintered body described above can be performed as follows.

First, Cu-Sn powder and Pb powder are mixed and pressure-molded. Subsequently, an infiltrant is layered on the Fe-based sintered body produced by the method described above, and heated at a temperature equal to or higher than the melting point of the infiltrant in an inert or reducing atmosphere. At this time, when the sintered body has a double structure as described above, for example, a bush, the outer diameter layer may be infiltrated simultaneously with the inner diameter layer.

[Work]

The Cu-based alloy infiltrant used in the present invention is β
Alternatively, it is hard and brittle because it is mainly composed of a γ-phase Cu-Sn intermetallic compound. Therefore, even if a surface pressure is applied during sliding, the solid lubricant does not spread and adhere, so that the solid lubricant can be stably and smoothly supplied onto the sliding surface. Pb contained in the infiltrant together with the β- or γ-phase Cu-Sn intermetallic compound is hardly solid-dissolved in the Cu-Sn intermetallic compound. Furthermore, Pb is soft and has a high spreadability, so that it spreads on the sliding surface during sliding, but does not react with Fe, so it does not seize and stick.
Moreover, since it has lubricity by itself, it diffuses well into the infiltrant and penetrates into the matrix of the sintered material to improve the lubricity of the entire sliding material.

Since such an infiltrant contains Sn and Pb, it has a melting point lower than that of the Cu-Co-based or Cu-Mn-based infiltrant described above,
Since the wettability to the system sintered material is also great, the infiltration property is very good. In addition, since it becomes possible to infiltrate at a low temperature of about 900 ° C., the reactivity between Fe and the solid lubricant, especially graphite is suppressed. In other words, since the generation of a hard cementite phase is prevented, there is no fear of damaging the mating material when used as a sliding material. Therefore, from this point of view, it is not necessary to use MoS ₂ , WS ₂ , BN, water glass-coated graphite or the like instead of graphite. Widening the range of application of this graphite has great industrial advantages in terms of price, easiness of granulation and the like.

Further, by dispersing the oxide-based ceramics as described above in the Fe-based sintered body, the wear resistance of the matrix of the sintered body is improved. Then, by preventing excessive wear of the matrix, the replenishment efficiency of the solid lubricant can be enhanced, and stable self-lubricating property can be maintained.

〔Example〕

Next, an example in which the self-lubricating sliding material according to the present invention is applied to a bush of a bearing will be described. In the bush of this embodiment, the outer diameter layer is made of a high-strength sintered material and the inner diameter layer is made of the self-lubricating sliding material according to the present invention in which a solid lubricant is dispersed by double-layer molding. The bush of this example was obtained by the following steps.

Powder Mixing Fe powder (atomized powder) and carbon (average particle diameter: 10 μm) were used as the powder components of the outer diameter layer in the composition shown in Table 1.

As the powder component of the inner diameter layer, Fe-Ni-Mo alloy (atomized alloy powder), carbon (same as above), graphite and SiO ₂ were used in the composition shown in Table 1.

The powders for the outer diameter layer and the inner diameter layer were mixed with a V-type mixer for 30 minutes so that there was no mixing deviation.

Forming First, two-layer powder feeding was performed using a two-layer powder feeding jig. In this two-layer powder feeding, the molding die was divided into an outer diameter portion and an inner diameter portion by a partition plate, and the outer diameter portion was filled with the outer diameter layer powder and the inner diameter portion was filled with the inner diameter layer powder. After this filling, the partition plate was pulled up and pressure molding was performed by CIP. This molding pressure is 4t /
It was cm ² .

Sintering was carried out by holding the molded body obtained by firing at a sintering temperature of 1100 ° C. for 1 hour in a vacuum atmosphere.

Infiltration The Cu—Sn intermetallic compound and Pb were used in the composition shown in Table 2 as components of the infiltration agent. (In addition, Cu-Sn intermetallic compound,
Water atomized powder was used as Pb. ) These infiltrant powders were mixed in the same manner as in the above, then filled in the same mold as in, and molded in the same manner as in except that the two-layer powder feeding jig (partition plate) was not used. Infiltration was carried out by placing a compact of this infiltrant on top of the sintered body and holding it at a infiltration temperature of 1050 ° C. for 1 hour in a reducing atmosphere consisting of ammonia decomposition gas.

Roughing, heat treatment and finishing After the roughing was done by the usual method, it was held at 850 ° C for 1 hour, water-cooled, tempered at 180 ° C for 3 hours, and finally finished to complete the bush. .

Abrasion test The bushes obtained in the examples were attached to a bearing tester to perform an abrasion test. This test condition is shown in FIG.
In this test, the friction heat generated in the bush due to the swing of the shaft (swing angle: 180 °) was detected with a thermocouple.
The wear coefficient was calculated by measuring the torque. The results are shown in FIG. 2 together with the case of the comparative bush. The bush of the comparative example is manufactured in the same manner as in the example except that the compositions of the sintered body and the infiltrant are shown in Table 1 and Table 2, respectively.

From the wear test results shown in FIG. 2, it was confirmed that the bush of the example has a life approximately twice that of the bush of the comparative example.

[Advantages of the Invention] According to the self-lubricating sliding material of the present invention, the Fe-based sintered body contains the β- or γ-phase Cu-Sn intermetallic compound and Pb.
Since the infiltrating agent of the Cu-based alloy material is infiltrated, (a) the strength of the sintered body is increased, and (b) the solid lubricant is smoothly supplied to the sliding surface for a long time. Self-lubricating property is stably maintained, (c) The infiltrant and the matrix of the sintered body each have lubricity, and the self-lubricating property is improved. (D) Cementite phase causing damage to the mating material Can be prevented from being generated in the matrix. Therefore, compared to the conventional dry bearing member, stable performance can be achieved without lubrication even under a very high surface pressure, and maintenance-free mechanical components can be realized.

[Brief description of drawings]

FIG. 1 is a graph for explaining wear test conditions of an example and a comparative example when a self-lubricating sliding material according to the present invention is applied to a bush of a bearing, and FIG. 2 is a graph showing the test result. .

Claims (2)

(57) [Claims] 1. A F containing 10 to 50 vol% of a solid lubricant dispersed therein.
e-sintered body containing 15-40 wt% Sn, β or γ phase C
u-Sn intermetallic compound as the main component, and Pb content of 3-40wt%
% Self-lubricating sliding material, characterized in that the infiltrant of a Cu-based alloy material to be blended is infiltrated. 2. A Fe-based sintered body in which a solid lubricant is dispersedly contained in an amount of 10 to 50 vol% and 0.5 to 5 vol% of oxide ceramic particles are dispersed, and β containing 15 to 40 wt% of Sn or A self-lubricating sliding material comprising a Cu-Sn intermetallic compound in the γ phase as a main component and further infiltrated with an infiltrant of a Cu-based alloy material containing 3 to 40 wt% of Pb.