JP2561876B2 - Graphite composite sliding member - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphite-based composite sliding member which is useful as a mechanical component for a sliding bearing, a rolling bearing retainer, a sliding valve, a contact type seal, and the like where friction occurs due to sliding. More specifically, especially in the high temperature range (300 ° C
The present invention relates to a graphite-based composite sliding member which has excellent friction and wear characteristics and is suitable for use under conditions where it is difficult to use a fluid lubricant such as lubricating oil or grease, that is, under so-called dry friction conditions.

[0002]

2. Description of the Related Art In recent years, with the development of mechatronics, there has been an increasing demand for sliding members having excellent friction and wear characteristics, especially in a high temperature range.

As a sliding member used in a high temperature range of 300 to 500 ° C., a fluid lubricant such as lubricating oil or grease cannot be used between the contact surfaces, so that it is usually made of graphite or molybdenum disulfide. Such solid lubricants are used. Since these solid lubricants generally do not have fluidity and wettability like fluid lubricants, when they are used,
Means such as coating, impregnation and pouring cannot be used.

Therefore, in the case of a solid lubricant, the lubricant is coated on the friction surface, the sliding member itself is made of the solid lubricant, or the solid lubricant is mixed with other materials for use. Must be applied by such means. In all of these means, a part of the solid lubricant adheres to the surface of the other member between the sliding contact surfaces to form a solid lubricant film having a desired film thickness, so that the lubricating effect is exhibited for the first time. Therefore, the quality of the film forming property of the solid lubricant film on the surface of the mating member influences the friction and wear characteristics.

Conventionally, graphite is most often used as a solid lubricant because of its self-lubricity, good thermal conductivity, non-melting property, small thermal expansion coefficient and excellent heat resistance. Has been done. The graphite used for this sliding member is generally classified into natural graphite and artificial graphite. However, when the solid lubricant itself is used as the sliding member, it is slightly different in terms of friction and wear characteristics. Artificial graphite, which is inferior but capable of obtaining a high-strength molded body, is generally used.

As a method for producing this high-strength graphite molded body, for example, an aggregate such as caustic powder is used by using a binder such as coal tar pitch, which is carbonized and graphitized by itself by heating and firing. Molded, this is 700 ~
After firing at a temperature of 1100 ° C, it is re-fired by infiltrating an impregnating agent such as pitch, and then heat-treated at a temperature of 2500 to 3000 ° C to obtain graphitization. In order to obtain a graphite molded body, a method of impregnating the graphite molded body with a synthetic resin or a metal is also performed.

The graphite molded body obtained by the above-mentioned method can be used as it is as a sliding member, but in terms of friction and wear characteristics, especially the film forming property of the graphite coating on the surface of the mating member in the high temperature region. However, as a result, the friction coefficient is high and the wear amount is large, which causes a drawback in the friction and wear characteristics, and in the above-described method, the time required for production such as graphitization of coke powder is extremely long ( There is also a manufacturing defect that it generally takes 2 to 3 months).

[0008] Therefore, the present applicant has previously filed Japanese Patent Application No. 59-1497.
No. 06 (Japanese Examined Patent Publication No. 63-13953), a high temperature wear-resistant graphite-boron carbide sliding member comprising a sintered body of a mixture of 65 to 95% by weight of carbon powder and 5 to 35% by weight of boron carbide powder. (Hereinafter referred to as No. 706 sliding member) was proposed.

The No. 706 sliding member is obtained in a short time, and is a drawback of the graphite molded body obtained by using the conventional pitch binder, which is a drawback of the graphite material on the surface of the mating material in the high temperature region. It was intended to improve defects such as wear characteristics.

However, the sliding member of No. 706 deteriorates in film forming property of the graphite coating on the surface of the mating member due to an increase in its use condition, especially in speed condition (sliding speed), and as a result, deterioration in friction and wear characteristics. Tend to cause.

[0011]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the present invention, the characteristics of the sliding member No. 706 are effectively utilized as they are, and the physical properties of the sliding member are improved. An object of the present invention is to provide a graphite-based composite sliding member having excellent film forming properties and improved friction and wear characteristics.

[0012]

[Means for Solving the Problem] The inventors of the present invention have conducted extensive studies to obtain a sliding member which does not cause deterioration in friction and wear characteristics even when the sliding speed is increased, and as a result, carbon
(C) Powder and boro powder (B) or boron carbide (B ₄ C) powder are mixed with a predetermined amount of calcium fluoride (CaF ₂ ) powder, and the resulting sintered body is No. 706 sliding. Not only under the use conditions of the member, but also in the state where the sliding speed is increased, it was found that the graphite film on the surface of the other member is excellent in film forming property, and that it exhibits excellent friction and wear characteristics, and the present invention is based on this finding. It came to completion.

[0013]

The graphite-based composite sliding member of the present invention comprises a sintered body of a mixture of carbon powder and boron or boron carbide powder powder and calcium fluoride powder.

As carbon powder, calcinated coke containing no volatile matter, carbon black, amorphous carbon powder such as resin charcoal, raw coke containing volatile matter, bulk mesophase,
Examples thereof include carbonaceous powders such as mesocarbon microbeads, and graphitic carbon powders such as artificial graphite, quiche graphite, and natural graphite. These may be used alone or in combination of two or more. Good.

The boron or boron carbide powder plays a role as a sintering accelerator for the carbon powder, and is contained in the obtained sintered body to contribute to the improvement of the friction and wear characteristics especially in a high temperature region. The mixing ratio of the boron or boron carbide powder is 5 to 35% by weight based on the total weight of the graphite-based composite sliding member as boron. If the amount of this boron or boron carbide powder is less than 5% by weight, the effect as a sintering accelerator is reduced and, during the heating and sintering process, all of boron is dissolved in carbon to form a solid solution, and Since it does not exist in the bound body, improvement in mechanical strength and friction and wear characteristics becomes insufficient. This boron or boron carbide itself is not a substance exhibiting lubricity such as graphite or molybdenum disulfide, but when it is contained in a sintered body and used as a sliding member, it forms a graphite film on the surface of the mating material. It promotes film-forming properties, increases the durability of the coating in dry friction, and improves friction and wear properties. This tendency is particularly remarkable in the high temperature region. The amount of this boron or boron carbide powder
If it exceeds 35% by weight, the coefficient of friction increases, the wear resistance decreases significantly, and the surface of the mating material is damaged.

Calcium fluoride powder is a substance that has a surface that is completely cleaved in its crystal structure, has a low shear strength, and exhibits lubricity itself especially in a high temperature region. This calcium fluoride powder is mixed with the carbon powder and boron or boron carbide powder, and expands the plane spacing (lattice constant) in the C-axis direction of the crystal lattice structure of the graphite particles in the heating and sintering process to expand the graphite particles. The calcium fluoride powder has a function of enhancing cleavage in the shearing direction, and also has a function of forming a liquid phase in the heating and sintering process to densify the sintered body and improve physical properties of the sintered body. This action of enhancing the cleavage property further enhances the film forming property of the graphite coating on the surface of the mating member during sliding with the mating member. The blending ratio of this calcium fluoride powder is 3 to 20% by weight based on the total weight of the graphite-based composite sliding member. If the blending ratio is less than 3% by weight, not only the lubricity of the calcium fluoride powder itself is not exhibited, but also the effect of expanding the interplanar spacing of the graphite particles in the C-axis direction and the effect of improving the physical property values do not appear. Further, even if the blending ratio exceeds 20% by weight, no further effect appears on the lubricity of the calcium fluoride powder itself,
Moreover, no further effect is exerted on the expansion of the C-axis plane spacing of the graphite particles.

In the sliding member of the present invention, carbon powder is blended with a predetermined amount of boron or boron carbide powder and calcium fluoride powder to obtain 100 kg / cm ² or more, preferably 150 to 300 kg / cm ^2.
Under pressure of at least 2000 ℃, preferably 2100 ~ 2200 ℃
It is obtained by sintering at the temperature of. At this time, when raw coke powder is used as the carbon powder,
It can also be obtained by blending a predetermined amount of boron or boron carbide powder and calcium fluoride powder and sintering the mixture under normal pressure.

The graphite-based composite sliding member of the present invention has a Shore hardness of 40 or more, preferably 45 to 80 and a bulk density of 1.7 g / cm.
³ or more, preferably 1.80-2.40 g / cm ³ , bending strength 3
00 kg / cm ² or more, preferably 400 to 1700 kg / cm ² , and the surface spacing in the C-axis direction is 3.4 angstroms or more, preferably
3.425 to 3.495 angstrom, load 5kg / cm ² and friction coefficient less than 0.3 at sliding speed 30m / min, preferably
0.05 to 0.28 and wear amount 0.03 mm or less, preferably 0.005
~ 0.025mm and load 20kg / cm ² Slip speed 5m / min
Friction coefficient is 0.2 or less, preferably 0.03 to 0.12, and the wear amount is 0.01 mm or less, preferably 0.002 to 0.009 mm.

The graphite-based composite sliding member of the present invention is obtained by blending carbon powder with a predetermined amount of boron or boron carbide and calcium fluoride powder, and subjecting this to pressure sintering or atmospheric pressure sintering. In the sintering process, the action of the calcium fluoride powder in the components expands the C-axis plane spacing of the graphite particle crystal lattice structure to enhance the cleavage of the graphite particles in the shear direction and to increase the calcium fluoride content. The generation of the liquid phase in the sintering process of the powder densifies the sintered body, and the physical properties of the sintered body are increased. As a result, during sliding between the sliding member and the mating member, the graphite particles are easily sheared even when the speed condition is increased, and a graphite film is formed on the surface of the mating member. Since this graphite coating also contains a calcium fluoride coating as a component, the friction and wear characteristics in the high temperature region are also improved.

[0020]

EXAMPLES The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

Example 1 10, 20 and 35% by weight of boron carbide powder having an average particle size of 1.5 μm based on calcined pitch coke powder having a particle size of 150 μm or less
And 5, 10, 15 and 20% by weight of calcium fluoride powder having an average particle size of 50 μm were mixed and mixed to obtain a uniform mixture of the coke powder, the boron carbide powder and the calcium fluoride powder. This mixture was filled in a graphite mold, 200kg / cm
^Under pressure of ² , the temperature was raised to a temperature of 2100 ° C., and the temperature was maintained for 1 hour for sintering. Then, after cooling to room temperature, it was taken out from the graphite mold to obtain a sliding member. The physical properties and friction and wear characteristics of these sliding members are shown in the table as Sample No. 1 to N.
o. As shown in FIG.

Example 2 Bulk mesophase powder having an average particle size of 10 μm was used, to which 10 and 20% by weight of boron carbide powder having an average particle size of 1.5 μm was added.
5% and 10% by weight of calcium fluoride powder having an average particle size of 50 μm were mixed and mixed to obtain a uniform mixture of the bulk mesophase powder, the boron carbide powder and the calcium fluoride powder. This mixture is filled in a graphite mold and 1000 kg
It was compressed at a pressure of / cm ² to obtain a green compact. This green compact was heated in a sintering furnace at 2150 ° C. for 1 hour for sintering. Then, after cooling to room temperature, it was taken out from the graphite mold to obtain a sliding member. The physical properties and friction and wear characteristics of these sliding members are
In the table, it is as shown in samples No. 7 to No. 8.

Comparative Example Sample in Example of Japanese Patent Application No. 59-149706 (Japanese Patent Publication No. 63-13953)
Graphite sliding member composed of 80% by weight of calcined pitch coke powder of No. 4 and 20% by weight of boron carbide powder (Sample No. 9); graphite sliding member manufactured using a conventional pitch-based binder (Sample No. 9) .10); Graphite sliding member (Sample No. 11) manufactured by impregnating aluminum into a graphite compact manufactured using a pitch-based binder, and 80% by weight of raw caustic powder as carbon powder and boron carbide powder 20. Graphite compacts (Sample No. 12) obtained by pressure-sintering with 1 wt% were manufactured. The physical property values and friction and wear characteristics of these sliding members are shown in the table.

The coefficient of friction and the amount of wear in the table were measured by using a Suzuki type thrust tester with a length of 20 mm, a width of 20 mm and a thickness of 7 mm.
mm block-shaped sliding member, outer diameter 18 mm, inner diameter 14 mm, length
For a 20 mm stainless steel tubular body (counterpart member),
Load 5 kg / cm ² , sliding speed 30 m / min, load 20 kg / cm
^2. Sliding speed was 5 m / min, and sliding was performed at an ambient temperature of 350 ° C. The wear amount is a value obtained by measuring the wear amount of the sliding member after the test time of 2 hours.

As can be seen from this experiment, 3 to 35% by weight of boron carbide powder and 3 to 20% by weight of calcium fluoride powder were mixed with carbon powder, and this was pressure-sintered or pressure-sintered. The graphite-based composite sliding member obtained by
Excellent friction and wear characteristics were exhibited under any of the above conditions.

In the examples, examples of using calcined pitch coke and bulk mesophase as the carbon powder are shown, but other amorphous carbon powders, carbonaceous powders, artificial graphite powders, natural graphite powders, and these The same effect can be obtained by using the mixed powder of.

[0027]

[Table 1]

[0028]

[Effect] The graphite-based composite sliding member of the present invention is expanded with the cleavage in the shear direction of the graphite particles by expanding the C-axis plane spacing of the crystal lattice structure of the graphite particles. A graphite coating is easily formed on the surface of the member. Since the film-forming property of the graphite coating on the surface of the mating member is not affected by the change in the speed condition (sliding speed) with the mating member, it is possible to increase the sliding speed, which is a drawback of the sliding member of the prior art. The problem of deterioration of the film-forming property of the graphite coating on the surface of the mating member and the deterioration of friction and wear characteristics caused by the problem can be solved all at once.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kura Yoshida 807 Nonoshita, Yadomachi, Tosu City, Saga Prefecture 1 Kyushu Industrial Technology Laboratory (72) Inventor Kaji Kashima 8 Kiriharacho, Fujisawa City, Kanagawa Prefecture OILES CORPORATION (72) Inventor Katsumi Mino 8 Kirihara-cho, Fujisawa-shi, Kanagawa Examiner Kazutaka Itabashi, Oiles Industry Co., Ltd. (56) References JP 63-13953 (JP, B2) JP 57-25483 (JP) , B2)

Claims (2)

(57) [Claims] 1. A graphite-based composite sliding member comprising a sintered body of a mixture of 5-35 wt% boron or boron carbide powder, 3-20 wt% calcium fluoride powder, and the balance carbon powder. 2. The carbon powder includes amorphous carbon powder such as calcined coke, carbon black, resin charcoal, carbonaceous powder such as raw coke, bulk mesophase and mesocarbon microbeads, artificial graphite, quiche graphite and natural graphite. The graphite-based composite sliding member according to claim 1, which is one kind or a mixture of two or more kinds of graphitic carbon powder.