JP5637513B2 - Sliding material and mechanical seal - Google Patents

Description

  The present invention relates to a sliding material suitable for use in a mechanical seal and the like, and a mechanical seal using the same, and more specifically, a sliding material capable of further improving lubrication performance while having sealing performance, and the same. Regarding mechanical seals.

  Conventionally, when silicon carbide is slid in combination with a mechanical seal, the self-lubricating property is poor, so the sliding surface wears or the friction coefficient fluctuates and a rapid temperature rise occurs, causing thermal stress cracking. It was difficult to exhibit the excellent material characteristics. This is because, in the case of silicon carbide with high hardness, it is difficult to fit in and it is difficult to properly swell the sliding surface, so that silicon carbide comes into direct contact at a relatively early time and the sliding surface is damaged. There is.

  Therefore, when silicon carbide is used as a sliding material for a mechanical seal, it is essential to improve the lubrication performance of the sliding surface. One method for improving the lubricity of the silicon carbide sliding surface is to conventionally form pores in the sliding surface and use it as a reservoir for a sealing fluid to improve the lubrication performance. On the other hand, leakage must be suppressed on the sliding surface of the mechanical seal, and it is necessary to block the continuous fluid film of the sealing fluid.

  In order to simultaneously establish mutually contradictory effects on the sliding surface, it is necessary to form discontinuous fluid films in the rotational circumferential direction and the radial direction of the sliding surface. Thus, the sliding material for mechanical seals is required to maintain a sealing performance that is not found in other sliding materials, and even if pores are simply formed on the sliding surface, the pores can penetrate and leak. There are many cases where a route is made.

  In Patent Document 1, carbon particles having a particle size of 20 μm to 300 μm are mixed with silicon carbide powder to form a sintered body, which is provided with a sliding surface, and the carbon particles are burned and removed only on the sliding surface where the carbon particles are exposed. Thus, it is intended to form a recess on the surface of the carbon particles.

  However, the particle size of the carbon particles has a width of 20 μm to 300 μm, and it is easily imagined that it is very difficult to burn and remove so that the carbon remains uniformly in the bottom of the dent. There is a high possibility that all particles are oxidized and lost, or even if they remain, they are oxidized and lost strength.

  In addition, if a portion where several carbon particles on the surface of the sintered body are connected to each other is burned and removed, this becomes a leakage path and the sealing performance is deteriorated. Furthermore, in order to prevent breakage of the silicon carbide peripheral portion surrounding the carbon particles, carbon is left in the silicon carbide peripheral portion. However, when it burns, the temperature is higher as it is closer to the surface. However, it is brittle and easy to fall off.

  As described above, there is a problem with the hole making method described in Patent Document 1 for burning and removing carbon on the sliding surface to make a dent on the carbon surface, which is sufficient as a technique for improving the function of the mechanical seal. Absent.

  Moreover, there exists patent document 2 as a prior art regarding the mechanical seal which used the silicon carbide sintered compact containing the carbon bead which has a hollow for a sliding member. However, carbon beads have a wide variety of chemical bonding modes, crystal structures, and the like, and depending on their properties, there may be a problem that spherical carbon has insufficient strength during press molding.

  Further, simply dispersing spherical carbon in the silicon carbide structure causes a problem that the bonding between silicon carbide and carbon particles is insufficient and the spherical carbon formed on the sliding surface falls off.

  As described above, in the sliding material for mechanical seal, it is technically difficult to achieve both the formation of pores and the sealing performance, and it is a pore-dispersed sliding material having a lubricating effect and a mechanical device having sealing performance. There is a need for sliding materials.

Japanese Patent Laid-Open No. 2004-116587 JP 2001-139376 A

  For example, when the sliding surface of silicon carbide is mirror-finished, even if it is rotated with a slight undulation, no dynamic pressure is generated, and strong contact between solids occurs. However, the dynamic pressure generated on the sliding surface decreases when the undulation and roughness become too large, and the sliding surfaces come into contact with each other on the undulating convex portion.

  In order for such dynamic pressure to be generated and not to leak, submicron waviness on the sliding surface is necessary. Small waviness greatly affects sliding performance and sealing performance.

  In the conventional carbon sliding material, this minute undulation can be easily performed, so that dynamic pressure and cavitation are generated, and good lubricating performance is obtained while maintaining sealing performance. However, in the case of silicon carbide, since it is difficult to produce a stable submicron extremely small undulation, leakage occurs and sliding surfaces come into contact with each other, resulting in damage.

  Conventionally, it has been mentioned that silicon carbide sliding materials have poor self-lubricating properties, but apart from that, it is not possible to maintain good sealing performance and lubricating performance with silicon carbide sliding materials. What has happened because it is not formed on the sliding surface has been overlooked.

The present invention is a mechanical seal that slides silicon carbides that are said to have poor self-lubricating properties based on the above-mentioned knowledge that has been overlooked so far, and can further improve the lubricating performance while having sealing performance. As a new technique, a silicon carbide sliding material in which a plurality of pore groups having different peak pore diameters (the pore diameter having the highest frequency / hereinafter the same) is formed on the sliding surface is newly proposed.

In order to achieve the above object, the sliding material according to the present invention comprises:
A sliding material having pores formed on the sliding surface,
Frequency pore diameter becomes maximum is the macro domain a set of pores in the range of 0.05 to 0.1 mm, the frequency of the pore diameter the frequency is maximized is the macro domain value indicating pore diameter at the maximum When a set of pores that is 0.2 to 0.5 times a micro domain,
The macrodomain area ratio indicating the ratio of the area occupied by the macrodomain on the sliding surface is 2.0 to 10.0%,
The microdomain area ratio indicating the ratio of the area occupied by the microdomains on the sliding surface is 0.5 to 3 times the macrodomain area ratio.

  Preferably, on the sliding surface, the entire perimeter of the pores belonging to the macro domain and the micro domain is covered with a material softer than the material constituting the sliding material.

  Preferably, the material constituting the sliding material includes silicon carbide.

  Preferably, the soft material includes carbonaceous material.

  In the present invention, the pores formed on the sliding surface are composed of a macro domain and a micro domain which are a plurality of pore groups whose peak pore diameter is positively changed. The sealing liquid held in the macro domain having a relatively large pore cross-sectional area can obtain a load capacity by dynamic pressure generated on the sliding surface by rotation of the seal rotating ring fixed to the shaft, It flows out to the sliding surface outside the pores and generates an effect of improving the lubrication state.

  Therefore, the sealing liquid held in the macro domain of the sliding surface of the mechanical seal is pushed out of the pores along with the generation of dynamic pressure, and is absorbed by the micro domain having a relatively small pore diameter, so that the sealing liquid moves to the outside of the machine. It works to prevent leakage.

  As a result, when moving between the macro domain and the micro domain bi-directionally, the sealing fluid exists on the sliding surface and forms a liquid film to achieve a lubrication effect, and cavitation occurs in the empty pores. Since the liquid film is blocked, a sealing effect is obtained.

  Also, a hollow spherical carbon having one pore inside that is blocked from the outside by an outer shell made of non-graphite carbon on one sliding surface of a sliding material with poor self-lubricating property, particularly a silicon carbide sliding material. The hemisphere formed on the cut surface of the particle is preferably the above-mentioned pore.

  The present invention makes it possible to improve contradictory lubrication performance on the same sliding surface and maintain stable sealing performance for a long period of time. The feature is that the desired pores are made quantitatively by controlling the size and distribution of the pores, not the pores that are accidentally formed in the silicon carbide sintered body. As a result, good sliding performance and sealing performance It was possible to maintain.

  The mechanical seal which concerns on this invention has the sliding material in any one of said as a sealing ring for fixation and / or a sealing ring for rotation. By doing in this way, the mechanical seal excellent in sealing performance and slidability can be obtained. In the mechanical seal according to the present invention, the sliding material of the present invention may be used as both a sealing ring and a sealing ring for rotation. Or you may use as a sealing ring for fixation, and may be used as a sealing ring for rotation.

FIG. 1 is a schematic cross-sectional view in the vicinity of a sliding surface of a sliding material according to an embodiment of the present invention. 2A to 2C are schematic cross-sectional views of the sliding surface for explaining the behavior of the fluid existing on the sliding surface during sliding. FIGS. 3A and 3B are schematic cross-sectional views of the sliding surface showing the continuation of FIG. FIGS. 4A and 4B are schematic diagrams showing the pore size distribution of the macro domain and the micro domain. FIG. 5 is a schematic cross-sectional view of a sliding surface of a sliding material in which the entire periphery of pores belonging to the macro domain and the micro domain is covered with a carbonaceous material. FIG. 6 is a schematic cross-sectional view of a mechanical seal using a sliding material according to an embodiment of the present invention and a test apparatus therefor. FIG. 7 is a schematic cross-sectional view of a mechanical seal using the sliding rings of Examples 1 to 3 and Comparative Examples 1 to 3 and 7 and its performance test apparatus. FIG. 8A is a graph showing the relationship between the specific wear amount of the sliding surface and the G value in a mechanical seal performance test using the sliding rings of Examples 1 to 3 as a sealing rotary ring. FIG. 8B is a graph showing the relationship between the specific wear amount of the sliding surface and the G value in the mechanical seal performance test using the sliding rings of Comparative Examples 1 to 3 and 7 as the sealing rotary ring. is there.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

Sliding material The sliding material of the present embodiment is formed by forming pores having a specific pore diameter on a sliding surface at a specific ratio.

The material constituting the sliding material of the present embodiment is not particularly limited, for example, alumina (Al 2 O _3), silicon carbide (SiC), is preferably a hard material such as cemented carbide. In the present embodiment, the sliding material is made of silicon carbide.

  First, as shown in FIG. 1, attention is paid to pores (macropores 61 and micropores 62) formed on the sliding surface 50 per unit area in the sliding material (silicon carbide). As shown in FIGS. 2B and 2C, the sealing liquid 80 in the macropores 61 generates a positive pressure by generating a dynamic pressure by the rotation of the sliding surface 50. It is discharged out of the pores 61. If it does so, since the sealing liquid will reduce in a macropore, it will become a negative pressure and a cavitation will generate | occur | produce in a pore. However, when the inside of the macropores becomes equal to or lower than the saturated vapor pressure, the cavitation disappears due to the flow of the sealing fluid 80 from the surroundings and the inside of the macropores 61 is sealed again as shown in FIGS. 2 (A) and 3 (B). Filled with liquid 80.

  On the other hand, as shown in FIGS. 2C and 3A, the sealing liquid 80 discharged from the macropores 61 is sucked into the surrounding micropores 62 that are in a negative pressure while being dragged in the rotation direction. . At this time, since the sealing fluid 80 discharged from the macropores 61 exists and moves as a liquid film between the sliding surfaces, the friction coefficient is reduced because the lubricating effect is exerted between the sliding surfaces. Moreover, since the load capacity increases due to the pressure increase at the moment when the inside of the macropores 61 becomes a positive pressure, the contact between the solids is relaxed. Furthermore, by arranging the pores on the sliding surface, cavitation indispensable for maintaining the sealing performance of the mechanical seal described above is positively generated.

  Explaining the geometrical meaning of different mean pore diameters, for example, when the macropore radius is reduced to 1/2, the volume in the pores is reduced to 1/8. When the macropores and the neighboring micropores surrounding the macropores are limited, the flow rate pushed out from both pores is the same, but the micropores having a small volume are depleted earlier. That is, by this action, it becomes possible to give a time difference to the cycle mode between macropores and micropores.

  The following effects can be obtained by positively forming pore groups having different peak pore diameters on the same sliding surface. The sealing fluid flows into the macropores, discharges them, and creates a time difference in a series of cycle modes. The response of the micro domain having a relatively small pore volume is faster than that of the macro domain having a relatively large pore volume.

  Therefore, when dynamic pressure is generated in the macropores 61 and becomes positive pressure, the micropores 62 in the vicinity of the macropores 61 become negative pressure quickly and cavitation occurs, as shown in FIG. In addition, it acts to prevent leakage of the sealing fluid 80 released from the macropores 61 to the outside of the machine.

  As shown in FIGS. 3A and 3B, the sealing fluid absorbed by the micropores 62 flows out faster than the macropores 61 due to dynamic pressure, and the sealing fluid 80 is microporous. From 62, it flows into the macropores 61 where cavitation occurs. Thus, when the sealing fluid 80 moves on the sliding surface from the macropore 61 to the neighboring micropore 62 and from the micropore 62 to the neighboring macropore 61, a liquid film is formed on the sliding surface. A lubricating effect will be obtained.

However, as in the prior art, when a pore having the largest frequency (peak pore size) is formed on the sliding surface, the sealing fluid flows into the nearby pore and stops, so that Therefore, there is a concern that the lubricating effect cannot be expected without spreading, or the leaked sealing fluid spreads too much on the sliding surface and leaks out of the machine. For example, if all the sealing fluid filled in the pores having a pore diameter of 0.2 mm is discharged to the sliding surface and spreads, it reaches about 10 mm ² . Therefore, in the conventional sliding surface having a single peak pore diameter, if the pore area is simply increased in order to increase the load capacity due to the dynamic pressure rise generated by the rotation of the sliding surface, In addition, the sealing fluid film spreads greatly on the sliding surface, and a leakage path is formed on the sliding surface to leak out of the machine.

  On the other hand, when relatively small pores are formed on the entire sliding surface, there is no leakage to the outside of the machine, but there is a problem that the sealing fluid discharged from the pores is too small to obtain a lubricating effect on the sliding surface.

  In the present embodiment, the ratio between pore groups having different pore diameters is important for the silicon carbide sliding surface in which pores are formed by actively changing the peak pore diameter. The ratio of macropores to micropores is such that the micropore diameter is in the range of 1/2 to 1/5 of the macropore diameter and the ratio of the pore area is 0.5 to 2.0. When micropores in the range of the pore diameter are generated on the sliding surface, both the lubrication performance and the sealing performance can be maintained.

Further, as shown in FIG. 4 (A), a macro domain set of pores in the range peak pore diameter of 0.05 to 0.1 mm (macro pore group), a peak gas peak pore diameter of the macro domain A set of pores in the range of 0.2 to 0.5 times the value indicating the pore diameter is a microdomain (micropore group).

That is, when a macro domain having a peak pore diameter of 0.05 mm exists, in this embodiment, the peak of the micro domain pore diameter is in the range of 0.01 to 0.025 mm, and the peak pore diameter is 0.1 mm. In the present embodiment, the microdomain has a pore size peak in the range of 0.02 to 0.05 mm.

  When the pore size distribution of the macro domain and the pore size distribution of the micro domain overlap, as shown in FIG. 4B, the distribution is divided at the boundary between the distributions.

  Furthermore, the ratio of the area occupied by the macro domain on the sliding surface (macro domain area ratio) is 2.0 to 10.0%, preferably 3.0 to 7.0%. The ratio of the area occupied by the microdomains on the sliding surface (microdomain area ratio) is 0.5 to 3 times, preferably 0.7 to 1.5 times the macrodomain area ratio.

  Further, in the prior art, since the pores are directly formed on the silicon carbide sliding surface, the pores are sharply formed, and this portion may be lost due to shear stress. Fine pieces of silicon carbide that have been chipped off may remain on the sliding surface, and the sliding surface may be worn out and damaged. The best way to prevent this is to finely adhere the sliding surfaces between the silicon carbides. It is important not to generate silicon carbide fragments.

  Therefore, in this embodiment, as shown in FIG. 5, the pores 61 and 62 formed in the silicon carbide sliding surface 50 during the sliding are covered with the hollow spherical carbonaceous particles 70, and stress concentration occurs. Since the structure is not provided, it is possible to prevent the silicon carbide pieces from falling off. Furthermore, since the pores are in the center of the pores composed of the hollow spherical carbonaceous particles 70, the pores are separated by the carbon outer shell at the shortest, so that independent pores are formed on the sliding surface. There is a great advantage that the leakage path is not formed by connecting.

  Further, in the case of pores of a sliding material for mechanical seal, it is very important that the pores are not independent and communicated with each other in order to maintain the sealing performance. Further, the periphery of the pores formed on the sliding surface may be chipped, and the fine silicon carbide pieces may be detached and damage the silicon carbide sliding surface. This small silicon carbide piece is difficult to be discharged from the sliding surface, and when it enters the sliding surface, it causes abrasive wear. In addition, it is necessary not to create a sharp corner where stress concentration easily occurs.

Although the structure of a mechanical seal mechanical seal is not limited, the half cross section of the mechanical seal 100 with which a general industrial pump is mounted | worn is shown in FIG. In FIG. 6, a sealed rotary ring 110 is incorporated in a seal case 113 fastened and fixed to the rotary shaft 1 with a set screw 112, rotates integrally with the shaft, has a seal surface 52 on one end face thereof, and has a sealed rotary ring. Liquid leakage is sealed by incorporating a secondary seal 2 between the shaft 1 and the inner peripheral step portion 110.

  Further, the sealed rotating ring 110 is sealed so that the axial movement is restricted by the seal case 113 and the elastic force of the spring 115 that applies a pressing force in the axial direction is movable in the axial direction via the presser ring 117. The rotating ring 110 is configured to be pressed toward the non-rotating fixed sealing ring 120.

  Then, the sealing surface 53 on one end face of the fixed sealing ring 120 at the position facing the sealing rotary ring 110 rotates and slides while contacting the sealed rotary ring seal surface 52. A secondary seal 3 is mounted between the outer peripheral step of the fixed seal ring 120 and the pump casing 5 to seal liquid leakage. The fixed seal ring 120 is constrained to rotate via a fixed pin 6 for preventing rotation, provided on the inner periphery of the pump casing 5.

  The mechanical seal 100 configured in this way has an action of sealingly sealing the high-pressure side sealed fluid P1 by rotating and sliding while the sealing rotary ring 110 and the fixed sealing ring 120 rotate.

  In the present embodiment, the sealed rotating ring 110 and the fixed sealing ring 120 are made of silicon carbide, or one of the sealed rotating ring 110 and the fixed sealing ring 120 is soft such as carbon, graphite, carbon graphite mixed, etc. It is made of a sliding material, and pores are generated in either one of the sealing surface 52 of the sealed rotating ring 110 or the sealing surface 53 of the fixed sealing ring 120.

Manufacturing method of sliding material Although it does not restrict | limit especially as a method to manufacture the sliding material which concerns on this embodiment, What is necessary is just to manufacture by the method shown below, for example.

  Silicon carbide powder is prepared as a raw material.

  Spherical carbonaceous particles are prepared as a pore former for forming pores on the sliding surface. As the spherical carbonaceous particles, available existing ones may be used, and phenol resin, coal tar pitch, and the like can be obtained. In this embodiment, hollow spherical carbonaceous particles using carbon black as a raw material are used.

  In the present embodiment, the reason for using the hollow spherical carbonaceous particles as the pore former is as follows. Covering the soot around the pores on the sliding surface where the hollow spherical carbonaceous particles can easily form a sharp angle with the carbon particles can prevent the silicon carbide pieces from falling off. In addition, 2. 2. Since the pores are separated by the carbon shell on the outer periphery of the hollow spherical carbonaceous particle, independent pores are formed without the pores communicating with each other; This is because cracks that reduce the strength of the ceramic member can be avoided because the decomposition gas generated in the firing process is extremely small compared to the case of using resin beads.

  On the other hand, preferable physicochemical properties required for the hollow pore former are: 1. The melting point is higher than the sintering temperature, and the strength does not decrease even at the sintering temperature and is stable. 2. It has the effect of reducing the coefficient of friction while maintaining the hollow spherical shape; 3. Do not hinder the sintering of silicon carbide. 4. Bond firmly with silicon carbide so that it will not fall off when sliding. 5. Corrosion resistance and The coefficient of thermal expansion is the same as that of silicon carbide.

  Carbon and graphite are materials that satisfy these conditions and are available at low cost. Graphite has excellent self-lubricating properties, but there are the following disadvantages when graphite is made into hollow spherical particles. First, because the mechanical properties of graphite are anisotropic materials, the compressibility is different in the laminar direction and it does not compress evenly, and even if it receives compressive force evenly from the surroundings during silicon carbide sintering, it retains the hollow It is difficult to maintain a spherical shape.

  In addition, graphite is low in strength and easily cleaved, and graphite is a carbon hexagonal network surface with high crystallinity, so that strong bonding with silicon carbide is difficult, and hollow graphite particles may fall off during sliding. Comparing the material strength of carbon and graphite, the Young's modulus is about twice that of carbon, and the bending strength and compressive strength of carbon are about 1.5 times greater than graphite. Graphite has a smaller effect of suppressing the grain growth of silicon carbide particles during sintering than carbon. For the above reason, in this embodiment, the hollow spherical carbonaceous particles using carbon are used.

  The hollow spherical carbonaceous particles may be graphitized during the sintering process of silicon carbide. However, the main factors of graphitization are pressure and heating temperature, and it is said that high temperature heat treatment at about 2500 ° C. or higher is required under normal pressure. Further, any carbon is not graphitized by heating, but there are non-graphitizable (GC) and graphitizable carbon depending on the properties of carbon.

  As graphitizable carbon, mesophase carbon, coke, pyrolytic carbon and the like are known. On the other hand, non-graphitizable carbon can produce non-graphitizable carbon by heat treatment of carbon black or phenol resin or furan resin at around 1000 ° C.

  As a result of examining these non-graphitizable carbons, it was found that carbon black having strong non-graphitability is preferable because the development of the carbon layer surface is restricted even when heat-treated as a hollow spherical carbonaceous particle material. Then, it is set as the hollow spherical carbonaceous particle which uses carbon black as a raw material.

In addition to silicon carbide powder as a raw material for the sliding material, boron fine powder as a sintering aid, or carbon powder and carbon black fine powder for suppressing the grain growth of silicon carbide and generating a fine and dense structure. It may be added. In this case, the fine carbon powder or fine carbon black powder acts as a sintering aid, and has the effect of reducing and removing the SiO ₂ coating in the silicon carbide powder and increasing atomic diffusion between the silicon carbide powder particles.

On the other hand, boron diffuses to the surface of the silicon carbide powder in the early stage of the sintering process, lowers the surface energy of the silicon carbide powder, suppresses the evaporation of the silicon carbide, and the surface diffusion, and promotes the densification of the silicon carbide. There is. In the present embodiment, it is preferable to add B ₄ C 0.10 wt% to 1.0 wt% as a sintering aid.

  Moreover, the hollow spherical carbonaceous particles made from the carbon black powder put in as a pore forming material have a function of suppressing the coarsening of silicon carbide crystal grains. This is because if the hollow spherical carbonaceous particles are dispersed in the grain boundaries of silicon carbide, the sintering progresses and the silicon carbide particles grow and collide with the hollow spherical carbonaceous particles. Suppress growth. Due to this effect, dense silicon carbide particles are formed around the hollow spherical carbonaceous particles and are firmly bonded by receiving a uniform compressive force as the sintering proceeds.

  Since there is a correlation between the pore diameter contained in the hollow spherical carbonaceous particles and the outer diameter of the hollow spherical carbonaceous particles, the target range can be obtained by screening before introducing the hollow spherical carbonaceous particles. The particle size distribution is obtained.

Furthermore, in the present embodiment, a fine silicon carbide powder having an average particle diameter of 1.0 × 10 ⁻² μm to 3.0 × 10 ⁻¹ μm may be added to 1.0 wt% to 8.0 wt% with respect to 100 wt% of silicon carbide powder. preferable. The specific surface area (surface area / volume) of particles close to a sphere is inversely proportional to the particle diameter, and the smaller the particle diameter, the larger the specific surface area. There is an effect to advance the sintering of silicon carbide.

  When this fine silicon carbide powder is added and dispersed, the surface energy of the silicon carbide particles adjacent to the highly reactive fine silicon carbide powder is reduced, so that the sintering can proceed easily and a high-density silicon carbide sintered body can be easily obtained. Become. In this embodiment, since hollow spherical carbonaceous particles are dispersed in the structure of the silicon carbide sintered body, it is necessary to increase the density in order to maintain the strength. Furthermore, it is necessary to bond the hollow spherical carbonaceous particles physically and firmly so that they do not fall out of the silicon carbide structure.

  When fine silicon carbide powder is added and dispersed, a high-density silicon carbide sintered body is obtained, and the hollow spherical carbonaceous particles are solid at the boundary with the silicon carbide particles because the surrounding silicon carbide particles are subjected to shrinkage due to the sintering. It is firmly bonded by mechanical contraction force.

Here, it is preferable that the average particle diameter of the fine silicon carbide powder is 1.0 × 10 ⁻² μm or more because the smaller the particle diameter is, the more the particles are aggregated and it is difficult to add fine particles. If the diameter is made smaller than this, even if a concentrated colloidal system is used as the dispersing material, it tends to be difficult to disperse to primary particles or a particle size close thereto.

Further, the upper limit of the average particle diameter of the fine silicon carbide powder is preferably 3.0 × 10 ⁻¹ μm. When a fine silicon carbide powder larger than this is added, the dispersibility is remarkably improved. This is because the crystal density was not so much improved by observing the vicinity of the silicon carbide particles surrounding the particles and the periphery.

Of the above-mentioned silicon carbide powder, fine silicon carbide powder and sintering aid (B ₄ C, etc.), organic binders such as acrylic resin, phenol resin, coal tar pitch, polyimide, epoxy resin as a binder One type is preferably added in an amount of 2.0 to 5.0% by weight. These organic substances are soluble in an organic solvent, but a water-soluble phenol resin is preferable in consideration of the environment, and it is desirable to cure by heating at 150 ° C. or lower.

  Furthermore, water-soluble polyvinyl alcohol, preferably 1.5% to 3.0% by weight, hollow spherical carbonaceous particles and ion-exchanged water are added thereto, and a surfactant is added therein to form a slurry. After sufficiently stirring the slurry with a ball mill, the slurry is dried with a spray dryer and granulated.

  The granules are compression-molded with a metal mold press or rubber press almost similar to a mechanical seal shape, and further, the molded body is heated at 120 ° C. for 1 to 2 hours to complete the curing in order to cure the binder. This is machined to the mechanical seal part dimensions. Firing may be performed at 2050 ° C. to 2150 ° C. in an argon or vacuum atmosphere without pressure.

  Hereinafter, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.

Example 1
First, 100 weight% of silicon carbide powder pulverized to an average particle diameter of 1 μm was mixed with the following components to form a slurry. 4.0% by weight of fine silicon carbide powder of 0.3 μm or less is added, 3% by weight of carbon black is added to suppress silicon carbide crystal growth that occurs during sintering, and 0.15% by weight of B ₄ C is used as a sintering aid. % Was added. Further, 4.0% by weight of water-soluble phenol resin and 2.5% by weight of polyvinyl alcohol were added as binders.

  The hollow spherical carbonaceous particles are 1.1% by weight when the average pore diameter of the hollow part is 0.1 mm and 0.2% by weight when the average pore diameter of the hollow part is 0.02 mm, and ion-exchanged water is added to this. The slurry was made into a slurry having a concentration of 40%, and then, in order to uniformly disperse the hollow spherical carbonaceous particles in the slurry, they were mixed and stirred for 20 hours by a ball mill, and spray dried by a spray dryer to form granules.

  After filling this granule into a metal mold, press molding at 100 MPa, and further curing the binder, the molded body is heated at around 120 ° C for 1 to 2 hours to complete the curing, and then a test sliding ring And sintered at 2150 ° C. in an argon atmosphere.

  To confirm the sintered sliding ring structure, the sliding surface after polishing and lapping is taken with an optical microscope or digital microscope, and the sliding surface photograph taken in the range of 50 to 100 times is imported into software dedicated to image analysis. Designation of measurement area, correction by image quality improvement filter, pixel length was set to 1.000 μm / dot, and pore diameter and pore area were measured.

The measurement results are as follows: in an arbitrary sliding area of 10 mm ² , a pore group having a peak pore diameter of 0.086 mm and a standard deviation of 0.026 mm, and a pore group having a peak pore diameter of 0.018 mm and a standard deviation of 0.008 mm The total area porosity was 11.7%. The sliding surface finish roughness Ra after lapping was 0.03 to 0.05 μm. The silicon carbide sealed sliding ring is M01, and the bending test piece for bending strength test according to JIS R 1601 is T01.

Example 2
As hollow spherical carbonaceous particles, Example 1 except that 1.1% by weight of the hollow part having an average pore diameter of 0.1 mm and 1.0% by weight of the hollow part having an average pore diameter of 0.05 mm were added. Similarly, a sintered sliding ring was produced. The structure of the sintered sliding ring was confirmed in the same manner as in Example 1.

The measurement results are as follows: pore group with a peak pore diameter of 0.092 mm and standard deviation of 0.023 mm, and pore group with a peak pore diameter of 0.053 mm and standard deviation of 0.02 mm in an arbitrary sliding area of 10 mm ² The total area porosity was 22.8%. The sliding surface finish roughness Ra after lapping was 0.03 to 0.05 μm. The silicon carbide sealed sliding ring is M02, and the bending test piece for bending strength test according to JIS R 1601 is T02.

Example 3
As hollow spherical carbonaceous particles, Example 1 with the exception that 3.3% by weight of the hollow part having an average pore diameter of 0.05 mm and 3.3% by weight of the hollow part having an average pore diameter of 0.01 mm were added. Similarly, a sintered sliding ring was produced. The structure of the sintered sliding ring was confirmed in the same manner as in Example 1.

The measurement results were as follows: in a sliding area of 10 mm ² , a pore group having a peak pore diameter of 0.050 mm and a standard deviation of 0.015 mm, and a pore group having a peak pore diameter of 0.009 mm and a standard deviation of 0.003 mm The total area porosity was 7.7%. The sliding surface finish roughness Ra after lapping was 0.03 to 0.05 μm. The silicon carbide sealed sliding ring is M03, and the bending test piece for bending strength test according to JIS R 1601 is T03.

Comparative Example 1
A sintered sliding ring was produced in the same manner as in Example 1, except that 7.2% by weight of hollow spherical carbonaceous particles having an average pore diameter of 0.1 mm in the hollow portion was added. The structure of the sintered sliding ring was confirmed in the same manner as in Example 1.

As a result of measurement, the peak pore diameter was 0.098 mm, the standard deviation was 0.019 mm, and the area porosity was 8.8% in an arbitrary sliding area of 10 mm ² . The sliding surface finish roughness Ra after polishing and lapping was 0.03 to 0.05 μm. The silicon carbide sealed sliding ring is designated as S01.

Comparative Example 2
A sintered sliding ring was produced in the same manner as in Example 1 except that 13.0% by weight of hollow spherical carbonaceous particles having an average pore diameter of 0.05 mm was added. The structure of the sintered sliding ring was confirmed in the same manner as in Example 1.

As a result of measurement, in an arbitrary sliding area of 10 mm ² , the peak pore diameter was 0.052 mm, the standard deviation was 0.018 mm, and the area porosity was 19.0%. Sliding surface finish roughness Ra after polishing and lapping was 0.03 to 0.05 μm. The silicon carbide sealed sliding ring is designated as S02.

Comparative Example 3
A sintered sliding ring was produced in the same manner as in Example 1 except that 7.3 wt% of hollow spherical carbonaceous particles having an average pore diameter of 0.05 mm in the hollow portion were added. The structure of the sintered sliding ring was confirmed in the same manner as in Example 1.

As a result of measurement, in an arbitrary sliding area of 10 mm ² , the peak pore diameter was 0.046 mm, its standard deviation was 0.017 mm, and the area porosity was 8.4%. The sliding surface finish roughness Ra after polishing and lapping was 0.03 to 0.05 μm. The silicon carbide sealed sliding ring is designated as S03.

Comparative Example 4
To 100% by weight of silicon carbide powder ground to an average particle size of 1 μm, 3.0% by weight of fine silicon carbide powder of 0.3 μm or less was added, and 3% by weight of carbon black was added. Further, 0.15% by weight of B ₄ C was added as a sintering aid. Furthermore, 4.0% by weight of a water-soluble phenol resin was added as a binder.

  Next, 1.8% by weight of commercially available polystyrene beads having an average pore diameter of 0.01 mm and ion-exchanged water are added to form a slurry with a concentration of 40%. Next, a ball mill is used to uniformly disperse the polystyrene beads in the slurry. The mixture was stirred for a period of time and spray dried with a spray dryer to form granules. The granules were filled into a metal mold, pressure-molded, machined to the dimensions of a test sliding ring, and then sintered at 2150 ° C. in an argon atmosphere.

The structure of the sintered sliding ring was confirmed in the same manner as in Example 1. Measurements, during any sliding area 10 mm ^2, the peak pore diameter of 0.01 mm, standard deviation at 0.006 mm, an area porosity of 5.6%. The silicon carbide sealed sliding ring is designated as S04.

Comparative Example 5
A sintered sliding ring was prepared in the same manner as in Comparative Example 4 except that 4.0% by weight of fine silicon carbide powder of 0.3 μm or less was added and 23% by weight of commercially available polystyrene beads having an average pore diameter of 0.01 mm were added. did. The structure of the sintered sliding ring was confirmed in the same manner as in Example 1.

As a result of measurement, the peak pore diameter was 0.009 mm, the standard deviation was 0.004 mm, and the area porosity was 20.5% in an arbitrary sliding area of 10 mm ² . The silicon carbide sealed sliding ring is designated as S05.

Comparative Example 6
A sintered sliding ring was prepared in the same manner as in Comparative Example 4 except that 4.0% by weight of fine silicon carbide powder of 0.3 μm or less was added and 0.7% by weight of commercially available polystyrene beads having an average pore diameter of 0.20 mm were added. did. The structure of the sintered sliding ring was confirmed in the same manner as in Example 1.

As a result of measurement, the peak pore diameter was 0.196 mm, the standard deviation was 0.028 mm, and the area porosity was 4.6% in an arbitrary sliding area of 10 mm ² . The silicon carbide sealed rotating ring is designated as S06.

Comparative Example 7
A sintered sliding ring was produced in the same manner as in Comparative Example 4 except that 4.0% by weight of fine silicon carbide powder of 0.3 μm or less was added and no pore former was added. The sliding surface of the obtained sliding ring was polished and lapped to finish the surface roughness (Ra) to 0.02 μm to 0.05 μm. The silicon carbide sealed rotating ring is referred to as S07.

Comparative Example 8
First, 3% by weight of carbon black is added to 100% by weight of silicon carbide fine powder pulverized to an average particle size of 1 μm, 0.15% by weight of B ₄ C is added as a sintering aid, and a water-soluble phenol resin is added. 4.0 wt% and polyvinyl alcohol 2.5 wt%. Further, hollow spherical carbonaceous particles having an average pore diameter of 0.01 mm in hollow portions are 17.0% by weight, and ion-exchange water is added to form a slurry having a concentration of 40%, and then the hollow spherical carbonaceous particles are uniformly dispersed in the slurry. Therefore, the mixture was mixed and stirred for 20 hours with a ball mill, and spray dried with a spray dryer to form granules. The granules were filled into a metal mold, pressure-formed at 100 MPa, machined to the dimensions of a test sliding ring, and then sintered at 2150 ° C. in an argon atmosphere.

The structure of the sintered sliding ring was confirmed in the same manner as in Example 1. As a result of measurement, the peak pore diameter was 0.009 mm, the standard deviation was 0.003 mm, and the area porosity was 18.0% in an arbitrary sliding area of 10 mm ² . The specimen for bending strength test based on JIS R 1601 is designated as T08.

  From Table 1, it was confirmed that sliding materials having different peak pore diameters can be obtained by using hollow spherical carbonaceous particles having different average particle diameters.

  Further, from Table 2, it was confirmed that the use of the fine silicon carbide powder can suppress the decrease in the strength of the sintered body due to the formation of pores. On the other hand, it was confirmed that the bending strength of the sintered body of Comparative Example 8 that did not use the fine silicon carbide powder was greatly reduced.

Mechanical seal static test As shown in FIG. 7, the above-mentioned silicon carbide fixed ring is mounted on the sealing fixed ring 210 of the mechanical seal in which the testing machine is incorporated, and M01 to M06 and S01 to S03 are mounted on the opposing rotating ring. A leak test was performed when stationary (non-rotating). The test method is that the mechanical seal tester shown in FIG. 7 is kept stationary without rotating, and water pressurized to 7 MPa by a hand pump is supplied to the machine inner side 50 and left as it is for 30 minutes. Was confirmed visually. As a result of the test, no leakage was confirmed in the test rotating rings of M01 to M06 and S01 to S03 having pores on the sliding surface, and it was confirmed that good sealing performance was maintained in a static static pressure state. .

  For all samples (Examples 1 to 3 and Comparative Examples 1 to 3 and 7), leakage to the atmosphere side could not be confirmed, and good sealing performance was confirmed.

Mechanical seal performance test The above-mentioned silicon carbide fixed ring is mounted on the mechanical sealing fixed ring 210 shown in FIG. 7, and the test slide rings M01 to M03 of Examples 1 to 3 are mounted on the opposed rotating ring 100, A rotation test was performed under the following conditions to confirm sliding performance and sealing performance.

  The sealing liquid uses tap water, turbine oil VG32 and VG46, and the supply side inlet temperature is adjusted to 20 to 80 ° C, the process pressure to 0.2MPa to 3MPa, and the rotation speed to 500r / min to 3600r / min. The temperature of the rotating and stationary sliding surfaces under test was measured by inserting a thermocouple at a position of 1 mm or less directly below the sliding surface, and the viscosity of the sealing liquid was determined from this temperature.

  The test results are shown in FIGS. 8 (A) and (B). The test time for each point shown in FIG. 8 was 72 to 100 hours. After the test was completed, the wear depth was measured, and then re-polishing, lapping and reused. Trace the two sliding surfaces after the test with a surface roughness meter at a magnification of 5000 times in the radial direction to obtain the wear depth, calculate the wear volume based on that, and calculate the specific wear amount from the load and sliding distance did.

Evaluation of the leakage performance test of the mechanical seal is performed using an fG graph that represents the relationship between the dimensionless characteristic number G value and the friction coefficient f. In this graph, it was found that there was a clear boundary line (sealing limit line) between the points that did not leak and the points that did not leak in the test. There will be no leakage above the line and leakage will be observed below the boundary. The above G is given by Equation 1 below.
G = (ZVb) / W Equation 1
Here, G is the dimensionless characteristic number, Z is the viscosity coefficient of the fluid in the vicinity of the sliding portion, V is the speed, b is the sliding surface width, and w is the load.

On the other hand, the relationship of fG is shown in the following equation 2. In the fG graph, there is a value Ψc on the boundary between sealing and leakage, and the limit of sealing is determined by this Ψc. In the mechanical seal, when Ψ in the f-G graph rises to the right, it indicates that a fluid film that is a fluid lubrication region is formed.
Ψ = f / √G Equation 2

  Although the result of the sliding performance test of Examples 1-3 is shown to FIG. 8 (A), there was no leak in all the points. In the graphs shown in FIGS. 8A and 8B, the vertical axis represents the specific wear amount (proportional to f), and the horizontal axis represents the dimensionless characteristic number G value defined by Equation 1. Table 3 shows the qualitative view of the G value. The G value decreases as the load (W) increases, decreases as the viscosity (Z) decreases due to temperature rise, and decreases as the speed (V) decreases. It is a dimensionless number. Therefore, G becomes smaller as the sliding condition becomes more severe.

  As the mechanical seal material, a sliding material that has a very small amount of leakage and has a wide range of G value, and has a small amount of wear even in a region where the G value is small is the best. Evaluation of the superiority or inferiority of the test sliding ring is performed at the limit G value at which the G value decreases and the wear amount starts to increase.

  When the limit G value of FIG. 8A (Examples 1 to 3) is compared with the limit G value of FIG. 8B (Comparative Examples 1 to 3), Example 1 clearly shown in FIG. The limit G value of ˜3 is smaller than Comparative Examples 1 to 3 shown in FIG. That is, Examples 1 to 3 shown in FIG. 8 (A) have less wear amount even under severer sliding conditions than Comparative Examples 1 to 3 in FIG. 8 (B), and excellent sliding performance as a mechanical seal sliding material. It can be said that it has.

  The sliding surface formed with macrodomain and microdomain pores may have better sliding performance and sealing performance even under more severe sliding conditions than a sliding surface having a single peak pore diameter. Proven.

  Further, Comparative Example 7 (no pores) shown in FIG. 8B shows good sliding performance with a small specific wear amount in a region where the G value is large, that is, a region where the sliding conditions are not strict. As the value was lowered (sliding conditions became severe), the amount of wear began to increase rapidly. As described above, the silicon carbide sliding surface without pores has no problem in sliding performance as long as the G value is large. However, when the sliding condition becomes severe, the sliding performance deteriorates as soon as the sliding condition becomes severe, causing leakage and leakage. Will occur.

DESCRIPTION OF SYMBOLS 1 ... Mechanical seal 2 ... Sealing ring for rotation 3 ... Sealing ring for fixation 50 ... Sliding surface 61 ... Macropore 62 ... Micropore 80 ... Fluid

Claims (5)

A sliding material having pores formed on the sliding surface,
Frequency pore diameter becomes maximum is the macro domain a set of pores in the range of 0.05 to 0.1 mm, the frequency of the pore diameter the frequency is maximized is the macro domain value indicating pore diameter at the maximum When a set of pores that is 0.2 to 0.5 times a micro domain,
The macrodomain area ratio indicating the ratio of the area occupied by the macrodomain on the sliding surface is 2.0 to 10.0%,
The sliding material whose micro domain area ratio which shows the ratio of the area which the said micro domain occupies on the said sliding surface is 0.5 to 3 times the said macro domain area ratio.   2. The sliding material according to claim 1, wherein, on the sliding surface, the entire perimeter of pores belonging to the macro domain and the micro domain is covered with a material softer than a material constituting the sliding material.   The sliding material according to claim 1 or 2, wherein a material constituting the sliding material contains silicon carbide.   The sliding material according to claim 2 or 3, wherein the soft material includes carbonaceous material.   The mechanical seal which has the sliding material in any one of Claims 1-4 as a sealing ring for fixation and / or a sealing ring for rotation.

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