JPH0312596B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a carbon sliding material for mechanical seals. Prior Art The carbon sliding material for mechanical seals that has been commonly used in the past is made by kneading graphite with a pitch binder and then hot-pressing it. This sliding material has the advantage of forming a glossy, smooth mirror surface under water, oil conditions, etc. and exhibiting excellent sealing properties. Problems to be Solved by the Invention However, with the conventional carbon sliding materials as described above, the sliding surface becomes mirror-like after the start of use, and there are too few irregularities from a microscopic perspective, so it cannot be used for mechanical seals. In the case where the sealing liquid is used, it is difficult to form a uniform film of the sealing liquid on the sealing portion, and the heat generated by rotational torque and sliding is rather large, so problems such as cracking and blistering are likely to occur. An object of the present invention is to overcome the above-mentioned drawbacks of conventional carbon sliding materials. Means for Solving the Problems The means adopted in the present invention to solve the above problems is to use non-graphitizable carbon powder as a part of the carbonaceous material constituting the carbon sliding material for mechanical seals. . The non-graphitizable carbon powder is a hard carbon powder that does not graphitize and become soft even when heated, such as activated carbon such as coconut husk activated carbon, or pulverized synthetic resin carbide. Coconut shell activated carbon has particularly high hardness and excellent usability, making it the most suitable carbon powder to be included in the sliding material of the present invention. The amount of non-graphitizable carbon powder is preferably 5 to 30% by weight of the total carbonaceous material constituting the sliding material. If the amount of non-graphitizable carbon powder is too large, the thermal conductivity becomes low and the temperature is likely to rise, and the coefficient of friction becomes high, which is not preferable. Further, the particle size of the non-graphitizable carbon powder is preferably about 5 to 50 μm. If the particle size is too small, the effect of use will not be achieved, and on the other hand, if the particle size is too large, it will be difficult to produce a product with a uniform composition. Except for using non-graphitizable carbon powder as a part of the carbonaceous material, the sliding material of the present invention is not particularly different from conventional carbonaceous sliding materials, including its manufacturing method. That is, as carbonaceous materials other than non-graphitizable carbon powder, natural or synthetic graphite, carbon black, mesophase microspheres made from pitch, coke powder, etc. are used, and as binders, coal tar pitch, synthetic resin-based ones, etc.
All that are used in the production of sliding materials of this type can be used. In addition, when mesophase microspheres are used as the carbonaceous material, since this material has a trace amount of resinous components and tubular functional groups on the surface, it is possible to mold and bake without a binder. The molding can be performed by any molding method such as a pressure molding method or an extrusion molding method, and the heating and baking after molding can also be performed arbitrarily within the range of about 1000 to 2800°C. Effect The non-graphitizable carbon powder contained in the sliding material of the present invention is harder and more wear-resistant than other carbonaceous materials and binders such as graphite and coke powder, so it is suitable for use in mechanical seals. In this case, a sliding surface is formed that has fine irregularities in which the portions where the non-graphitizable carbon powder appears on the surface are convex portions and the other portions are concave portions.
Due to the presence of these irregularities, a uniform micro gap is formed over the entire sliding part between the sliding material surface and the other sliding material, and a thin film of sealing liquid is formed uniformly and reliably. to help others. Examples Examples 1 and 2 After kneading and pulverizing the raw materials with the following composition in a kneader, they were made into blocks of 90mmφ x 50mmφ x 35mmL.
A sliding material was obtained by hot-pressing molding at 1000 kg/cm ² and further heat-treating to 1200°C.

[Table] * Particle size of 5 to 10 μm The physical properties of the obtained sliding material were as shown in Table 1.

[Table] Next, the above-mentioned sliding material was impregnated with a synthetic resin to maintain airtightness, and a performance evaluation test was conducted under the following conditions using a mechanical seal tester. A Evaluation based on hot water conditions Seal fluid: Fresh water Temperature: 80℃ Seal pressure: 20Kg/cm ² rotation speed: 3000rpm Time: 100 hours PV value: 85.4Kg/cm ²・m/sec Test piece dimensions: 56mmφ×81mmφ×27mmL Mating sliding material: Cemented carbide B Evaluation based on oil conditions Seal fluid: Turbine oil #32 Temperature: 60℃ Seal pressure: 30Kg/cm ² Rotation speed: 3000rpm Time: 100 hours PV value: 114.7Kg/cm ²・m/ sec Dimensions of test piece: 57mmφ x 72.5mmφ x 23.2mmL Mating sliding material: Cemented carbide The test results are shown in Tables 2 and 3. however,
"Carbon surface condition" is a value measured by a surface roughness meter for unevenness of a carbon sliding surface.

【table】

【table】

[Table] * Occurred in 2 to 5 locations Examples 3 and 4 Raw materials of the following formulation were wet mixed using acetone as a solvent, dried, and granulated to obtain a powder for molding.

[Table] Next, this powder was heated to 1500 ml using a rubber press.
The molded body was molded into a disk shape of 50mmφ x 30mmL under a pressure of Kg/ ^cm2 , and the resulting molded body was fired at 2000℃ and then machined to form a sliding surface having an annular sliding surface with an inner diameter of 23mm and an outer diameter of 29mm. It was used as a dynamic material. Next, a performance evaluation test was conducted on each sliding material under the following conditions. The results are shown in Table 4. Seal fluid: Turbine oil #68 Rotation speed: 1000 rpm Time: 24 hours Temperature: Natural temperature rise PV value: 5 Kg/cm ² m/sec Mating sliding material: Tungsten carbide Testing machine: Vertical friction and wear testing machine

[Table] * Measured at a position 1 mm directly below the sliding surface In addition, a micrograph (200x magnification) of the sliding surface of the sliding material of Example 3 after the test is shown in FIG.
The coconut shell activated carbon is slightly protruding on the sliding surface and hits hard, so it appears white in the photo. Effects of the Invention Due to the action of the non-graphitizable carbon powder as described above, the sliding material of the present invention has excellent liquid film forming properties with a sealing liquid when used as a sliding material for a mechanical seal. Therefore, by using the sliding material of the present invention, it is possible to reduce the torque compared to the case of using conventional carbon sliding materials, and the occurrence of cracks and blistering can be significantly reduced. can.

[Brief explanation of the drawing]

FIG. 1 is a micrograph (200x magnification) of the sliding surface of the sliding material of Example 3.

Claims (1)

[Claims] 1. (1) A carbon sliding material for mechanical seals, characterized in that a part of the carbonaceous material constituting the sliding material is non-graphitizable carbon powder. (2) The sliding material according to claim 1, wherein the non-graphitizable carbon powder accounts for 5 to 40% by weight of the total carbonaceous material. (3) The sliding material according to claim 1 or 2, wherein the non-graphitizable carbon powder is coconut shell activated carbon.