JP2005225716A - Ceramic material and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic material having a novel structure as a non-lubricating material exhibiting characteristics of high hardness/high strength/high melting point/high toughness/non-chemical reactivity remarkably improved compared to that of a conventional one by forming a composite material from vegetable carbon+organic polymer (phenol resin)+SiC whisker (SCW) and a novel method of manufacturing the same. <P>SOLUTION: The ceramic material is obtained by sintering a kneaded material comprising 5-28 vol% silicon carbide whisker, 60-80 vol% vegetable carbon ceramic powder and the balance being the phenol resin powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to bearings and repetitive slides, which are essential mechanical elements in the rotational operation parts of precision machine tools such as various machine tools and medical equipment, and various consumer equipment expected to play an active role in the ubiquitous computing society. Manufactures ceramic materials with high hardness, high strength, high melting point, high toughness, and no chemical reactivity, especially for ceramic materials that are attracting attention as a new material suitable for moving parts and other parts that are subject to repeated friction. The technical field of processing and selling is solid, the field of assembling and selling machine elements that employ these ceramic materials, the field of providing machine tools and devices suitable for various purposes and applications by incorporating such machine elements, etc. All related fields that are directly or indirectly related to ceramic materials are used as the technical field.

(point of view)
In the field of precision machine tools, with the aim of stabilizing accuracy and shortening work time, higher speeds are required for the spindle of machine tool bearings. From the viewpoint of workability, etc., efforts to further increase the structural strength and wear resistance of the constituent materials are continued, and the toughness is as low as possible, the friction coefficient is as low as possible, the wear resistance is high, and thermal deformation is minimized. We have been working on new iron-based, copper-based sintered alloys, new engineering plastics, etc. to find the properties that are familiar with the combination members, yet have good workability and fit economically. , 10,000 to 40, because it has not reached the point where it can sufficiently satisfy the properties of high hardness, high strength, high melting point, high toughness and chemical reactivity required for special bearings. For special bearings that require high-speed rotation of 00 rpm or higher, pressurized air is supplied to the minimum gap between the main shaft and its housing to compensate for the weakness of the material, and the main shaft is driven by the static pressure generated between them. Hydrostatic bearings that enable rotation in a non-contact supported state are often used, but the structure is sophisticated and not only expensive to manufacture, but also deteriorates the bearing characteristics during low-speed rotation and has a minimal gap. If a foreign object (water, oil, dust, etc.) enters the inside of the product, it will cause a significant deterioration of the characteristics, and maintenance must be taken in order to avoid such an event, increasing the work load. I couldn't avoid the problem.

(Conventional technology)
Under these circumstances, in order to utilize the structural characteristics of hydrostatic bearings, the high hardness, high strength, high melting point, high toughness, and no chemical reactivity required to construct the main shaft and housing are satisfied. The development and practical application of new materials is an urgent matter, and the “carbon-ceramic composite material” in Komatsugai invention published in, for example, Japanese Patent Application Laid-Open No. 62-176952 Ceramics or composites thereof used in “Gas bearing device” (Comparative invention) of Japanese Patent Application Laid-Open No. 5-248428, and after that, these conventional ceramics have poor formability and are not brittle and brittle. Japanese Patent Application Laid-Open No. 10-101453, Murayama's outside invention, developed and put into practical use as an ecological material that eliminates the drawbacks and can be provided at low cost. "Production method of hard porous carbon material product", Horikirikawa / Ohara invention "sleeve bearing device" published in Japanese Patent Laid-Open No. 2002-181049, and "Special" disclosed in Japanese Patent Publication No. 2002-250343 of the same person's invention There are non-lubricating materials of vegetable carbon ceramics such as “bearing devices”.

In this conventional vegetable carbon non-lubricated ceramic, the plant crystal and organic polymer (phenol resin) are mixed, and the strength of the ceramic crystal is reinforced by securing a viscous flow by adding some filler. Phenol resin added sintered van der Waals force (Van
der Waals Force) is a crystal structure by physical adsorption.
This crystal structure is an attractive force (usually a dispersive force) acting between molecules (interatomic) having no unpaired electrons, and the potential is V (r) = − C with respect to the interatomic distance r. It is obtained by loosely bonding neutral atoms (intermolecular force) represented by / r6 and progressing and growing in a certain direction while twisting in a state where the polymer crystal plates (lamellar structures) overlap each other. Yes, this ceramic crystal body has high hardness and strength, and when the plant carbon addition rate is 60 to 80%, material expansion and contraction deformation in a high temperature region due to non-lubricating and ceramicization are very high. At present, the plant has a vegetable carbon ceramic hardness of HV 400 to 600, a compressive strength of 160 to 246 MPa, and a bending strength of 45 to 78.4 MPa.
(1) Japanese Patent Laid-Open No. 10-101453 (2) Japanese Patent Laid-Open No. 2002-181049 (3) Japanese Patent Laid-Open No. 2002-250343

(Awareness of problems)
The conventional vegetable carbon ceramic non-lubricated material that has already been developed has a hardness of HV 400 to 600 as described above, has a relatively high hardness, a compressive strength of 160 to 246 MPa, and a bending strength of 45 to 78. Although it has achieved about 4 MPa, it still has a slightly low value in terms of fracture toughness, and it is a little weak as the strength of the material in mechanical and mechanical parts, sliding, bearings, and all related fields surrounding it. Although there is a demand for a ceramic material as a highly reliable non-lubricated material, particularly a fiber reinforced vegetable carbon non-lubricated ceramic, which has been improved as much as possible, it does not exist at present.

In general, the following two reinforcing methods are assumed as the fiber reinforcing method of the vegetable carbon non-lubricated ceramics.
(1) Continuous fiber addition strengthening method Reinforcing method in which any one of glass, boron, B4C, Be, and carbon fiber is added alone or in combination (2) Whisker fiber addition strengthening method Al203 (alumina), SiC (silicon carbide) , A strengthening method of adding either graphite alone or in combination

    The material characteristics of (1) and (2) are brittle in terms of thermal shock, mechanical strength, thermal expansion and fracture toughness. In order to satisfy these conditions, thermal shock, mechanical strength, thermal expansion, There is a demand for selection of a fiber reinforcement excellent in fracture toughness. Among them, whisker fibers, that is, SiC (silicon carbide) and SCW (silicon carbide whisker) are particularly attracting attention. Although the silicon) fiber is high in hardness, the fracture toughness is weak, SCW (silicon carbide whisker) has the same hardness as SiC (silicon carbide), but the fracture toughness value is high, and by realizing the short fiber entanglement composition, It can be said that realization of vegetable carbon fiber reinforced unlubricated ceramics with high hardness, high strength, and high toughness can be realized as expected.

(Object of invention)
In the present invention, based on the above knowledge, ceramics as a non-lubricated material exhibit characteristics of superior hardness, high strength, high melting point, high toughness, and no chemical reactivity, superior to the conventional ones. We were convinced that we could realize the material, and we started development and research very quickly, and as a result of repeating trial and error over many years and many trial productions and experiments, this time finally plant carbon + organic polymer (Phenolic resin) + SCW (SiC
Whisker) has succeeded in realizing a novel ceramic material having a composite material and a novel manufacturing method thereof, and the configuration will be described in detail below.

(Structure of the invention)
The ceramic material of the present invention realized from the above circumstances basically has the following configuration.
That is, a ceramic material having a gist of a structure obtained by sintering a kneaded material having silicon carbide whisker 5 to 28% by volume, vegetable carbon ceramic powder 60 to 80% by volume, and the balance being phenol resin powder. It is.

    According to the present invention having this basic structure, silicon carbide whiskers having a diameter of 0.05 to 1.5 μm and a length of 20 to 80 μm, 5 to 28% by volume, and vegetable carbon ceramic powder 60 to 80 volumes are included. %, And a ceramic material having a structure obtained by sintering a kneaded product with the remainder being phenol resin powder.

    Similarly, a composition obtained by sintering a kneaded product of 5 to 28% by volume of silicon carbide whisker, 60 to 80% by volume of vegetable carbon ceramic powder having a particle size of 20 to 60 μm, and the remainder being phenol resin powder. Ceramic materials are also included.

    Further, silicon carbide whisker 5 to 28% by volume having a diameter of 0.05 to 1.5 μm and a length of 20 to 80 μm, and vegetable carbon ceramic powder 60 to 80% by volume with a particle size of 20 to 60 μm, A ceramic material obtained by sintering a kneaded product with the remainder being phenol resin powder is also included.

(Related invention)
In addition to the ceramic material described above, the present invention also includes a method for producing the same, which is obtained by subjecting silicon carbide whisker powder to surface silane coupling treatment and forming a film of aminosilane-based silane coupling agent on the surface. After that, the plant carbon ceramics powder in a predetermined ratio with respect to the appropriate amount, and an appropriate amount of the phenol resin powder as the remainder thereof are mixed, kneaded and appropriately shaped, and then sintered in an inert gas atmosphere or vacuum, It is a manufacturing method of the ceramic material which consists of a structure made to manufacture.

The ceramic material of the present invention having the above-described configuration has achieved the highest strength toughness of the conventional ceramic materials, and has the highest compressive strength (about 246 MPa) of conventional injection-molded vegetable carbon ceramics. ) Exceeding 33% or more can be realized, and a value of 12% or more can be obtained for the same maximum bending strength (about 78.4 MPa). Bending stress can be greatly improved, and it is possible to make the material superior to ever as a material for repeated sliding members such as special bearings and brakes, and a ceramic material having such excellent characteristics. The conventional method of producing ceramic crystal binder phenol resin is a large amount of gas generated during the sintering process. Would then generate strain internal stress becomes Rukoto, whereas in some cases destroy, while adopting the vacuum baking, the nitrogen gas injected calcined 180 to 250 ° C. Vacuum 1/100
Absorbs and burns a large amount of gas, and then injects nitrogen gas and sinters using a sintering method of 700 to 1,100 ° C. and vacuum 1/10000 of the main firing. Thus, the yield is good, and a ceramic material with high reliability in product accuracy can be reliably manufactured.

In implementing the present invention having the above-described configuration, the best or desirable mode will be described.
First, the ceramic material matrix of the present invention is composed of vegetable carbon ceramic powder and phenol resin powder, and has a composition structure in which hard and tough whisker SCW powder is uniformly dispersed and intertwined. The whisker as a fiber reinforcement is represented by Al203 (alumina), SiC (silicon carbide), graphite, etc., but silicon carbide is required because of high strength. Whisker (SCW) is the best choice, and in Japan, it is currently only supplied by a specific manufacturer, but it is not limited to those of the manufacturer. Silicon carbide whisker (SCW) any whisker can be used It goes without saying.

    The characteristics of this whisker are as follows: (a) Melting point is as high as 2,690 ° C, and no change in physical properties is observed at ceramic firing temperature of 700 to 1,100 ° C. (B) High hardness and (c) Excellent strength. (D) High heat resistance, (e) Low specific gravity, (g) Low thermal expansion, (h) Chemical stability, (i) High conductivity, (n) High thermal conductivity The fiber reinforced carbon ceramics, as an engineering ceramics (WRC) material for machine parts, including non-lubricated sliding and bearing-related fields, have a low frictional resistance value if SCW is 28 volume% or less, Unprecedented material can be realized.

    SCW has a Mohs hardness of 9 and a hardness substantially equal to that of Al203 (alumina), an elastic modulus (Young's modulus) of 481 GPa, a tensile strength of 20.6 GPa, a specific gravity of 3.18, and a high hardness The fiber is a fiber-like fiber having both high toughness and high strength, and its size is not limited, but it is 0.05 to 1.5 μm in diameter and long in terms of ease of production and function development. It should be in the range of 20 to 80 μm, and the matrix (carbon ceramics) particles 20 to 60 μm powder are under the optimum conditions as a fiber matrix entangled fiber reinforced composite material. In addition, since it has high chemical reaction stability and excellent high thermal conductivity, it greatly contributes to strengthened crystals in the ceramic crystallization process and can be easily mixed uniformly with carbon ceramic powder as a matrix.

    By adding 5 to 28% by volume of this SCW, the fiber carbon reinforced vegetable carbon ceramics is uniformly bonded to the vegetable carbon ceramic powder. The fiber matrix relationship by the silane coupling treatment is strengthened by the coating treatment. It has a composition structure that promotes bonding and is further strongly bonded due to the entanglement of short fibers, and as a fiber reinforced ceramic, due to the high toughness that is the physical property of SCW, the compressive strength is 328 MPa, the bending strength is 90 This results in a very high toughness of .8 MPa.

    Since fiber-like fibers cannot be uniformly dispersed and mixed by ordinary mixing methods, the average particle length by ball milling is classified to MAX 80 μm or less to perform meshler classification, and the length of the fiber to be shortened is reduced. By making a powder of a desired size of 80 μm or less, a uniform distribution due to short fiber entanglement must be obtained.

    It is necessary to perform ball mill pulverization and meshler classification with a vegetable carbon ceramic powder of 20 to 100 μm particle size to 20 to 60 μmMAX. is there.

    SCW powder is subjected to surface silane coupling treatment, and a coating such as aminosilane silane coupling agent (N-phenyl-r-aminopropyltrimethoxysilane) is applied. After the coating treatment, plant carbon ceramic powder and phenol resin powder Kneaded with a kneading machine, and kneaded until the composition is uniform, and then added with SCW and similarly kneaded to achieve uniform composition by dispersing balance kneading. .

    The mixing ratio in the mixture is desirably set to a ratio of SCW powder 5 to 28% by volume with respect to vegetable carbon ceramic powder 60 to 80% by volume, and the balance being phenol resin powder, and is outside this range. If the plant carbon ceramic powder is less than 60% by volume, the lubricity and hardness are reduced. If the ratio exceeds 80% by volume, the ceramic crystal becomes brittle. If the SCW is less than 5% by volume, the effect of reinforcing the fiber is obtained. When the amount exceeds 28% by volume, the wear resistance during lubrication increases, so it can be said that the use of a ratio outside these ranges is not preferable.

The mixture is then filled into a mold and molded by a powder compression hot press (180 ° C.), a rubber-type hydrostatic press, or the like to obtain a molded body. Subsequently, the molded body was pre-sintered (1/100 vacuum furnace, 180 to 250 ° C.) to remove impurities, and then the degree of vacuum was 1/10000.
The main firing is performed by high-temperature sintering at a heating temperature of 700 to 1,100 ° C. In addition, blank processing shaping | molding by cutting is performed to a desired shape in the uncured state before this high temperature sintering, and grinding processing is required after high temperature sintering.

    Sintering is performed in an inert gas atmosphere or in a vacuum, preferably pre-baking at a vacuum degree of about 1/100, and main sintering at a vacuum degree of 1/10000. This is desirable. This is because, when carried out in the atmosphere, the oxidation phenomenon causes impurity deposition, abnormal volume consumption, and internal stress distortion of the internally generated gas, and there is a high possibility of destruction during firing. Therefore, it is desirable to prevent oxidation in the furnace by injecting nitrogen gas, absorb impurities generated during firing by vacuum vacuum, and control the cooling rate from a high temperature after completion of firing. For firing, either hot pressing with compaction is followed by temporary firing, or normal temperature isostatic pressing (CIP) is followed by preliminary sintering, and then vacuum main sintering is performed. In some cases, hot powder extrusion may be employed.

Vegetable carbon ceramic powder having an average particle size of 20 to 100 μm is pulverized with a carbide ball (φ3 to φ10) rotary pulverizer, molded and granulated with a granulator, and classified with a mesh mesher to obtain an average. Particle size 20-60
Fine particles of μm were used.
In addition, as a vegetable carbon ceramic powder, a powder manufactured by Sanwa Yushi Co., Ltd. (a plant carbon ceramic powder according to the invention taken up in Patent Document 1 (1)) RBC 100 μm was prepared.

As a fiber reinforcement, SCW powder (diameter 0.05 to 1.5 μm, length 20 to 200 μm) is ceramic ball (Al203) φ10, ceramic spot (Al203) φ150 × 150L.
Was prepared, and pulverized with a rotary pulverizer, and classified with a mesh mesher to obtain a fiber having a diameter of 0.05 to 1.5 μm and a length of 80 μm.

The coating was applied by the surface silane coupling treatment of the SCW powder, and the surface silane coupling was performed as follows.
That is, the diluted silane coupling liquid is dropped onto the SCW powder and uniformly kneaded, and a uniform coating in a wet state is performed. This is put into a drier and dried for about 12 to 15 hours. By this treatment, a film of an aminosilane coating agent having a thickness of about 0.03 to 0.05 μm can be formed on the surface of the SCW powder.

The SCW of 5 to 28% by volume subjected to the surface silane coupling coating treatment was added to and mixed with a homogeneous mixture of phenol resin powder and vegetable carbon ceramic powder of 20 to 60 μm. Knead uniformly over 20 hours. And these uniformly kneaded fine particle powder mixture has a diameter of 80 mm,
The mold is filled in a 50 mm deep mold, pressed with a hydraulic hot compression press at a pressure of 500 to 2,000 kg / square cm, heated to 180 ° C. or hydrostatic pressure (CIP) with a rubber mold to 900 to 2, Pressed at 000 kg / square cm to form a green compact having a diameter of 80 mm and a thickness of 13 to 15 mm.
This molded body was placed in a batch type vacuum furnace, pre-sintered at a temperature of 180 to 250 ° C. for about 20 hours, formed into a blank having an outer diameter thickness of 1 to 3 mm, and a heating temperature of 700 The main calcination was performed at 1,100 ° C. for 30 to 35 hours. The calcined product had a specific gravity of 1.3 to 1.4.

As a result, the compressive strength and bending strength of the obtained sintered body are as shown in the values in FIG.
Moreover, the test result is shown below as a comparison with the conventional vegetable carbon non-lubricated ceramics.

(Effect of Example)
From this comparison data, the ceramic material of the present invention shows a 49% increase in compressive strength and +108 MPa, and a +30.8 MPa and 51.3% increase in bending strength, as well as the coefficient of friction. The fiber reinforcement due to the addition of SCW significantly improves the brittleness of the ceramic itself as high hardness, high strength, high toughness and low friction of the ceramic itself, and also improves the lubricity. Therefore, from these data, it was confirmed that the ceramic material of the present invention has characteristics as a non-lubricated ceramic having high lubricity against brittle fracture.

(Conclusion)
As described above, the ceramic material of the present invention, that is, the vegetable carbon fiber reinforced unlubricated ceramic, has significantly required characteristics as compared with the vegetable carbon ceramics that were still fragile as a conventional special bearing and repeated sliding material. Because it is possible to improve, as a material for non-lubricated plain bearings and hydrostatic bearings, or as a material for repeated sliding, high hardness, high strength, high toughness, low friction, excellent wear resistance, In addition to the fields of bearings and sliding that generally have non-chemically reactive properties and require these conditions, they have been highly evaluated and expanded in fields directly and indirectly related to this field. It is expected that it will be adopted and spread throughout the range.

The drawing shows the test results of the ceramic material obtained by the typical embodiment of the present invention.
This is a data sheet from a test conducted by the Yamagata Industrial Technology Center.

Claims (10)

  A ceramic material obtained by sintering a kneaded material having silicon carbide whiskers of 5 to 28% by volume, vegetable carbon ceramics powder of 60 to 80% by volume, and the balance being phenol resin powder.   A kneaded product having a diameter of 0.05 to 1.5 μm, a length of 20 to 80 μm of silicon carbide whiskers of 5 to 28% by volume, a vegetable carbon ceramic powder of 60 to 80% by volume, and the balance of phenol resin powder. A ceramic material characterized by being sintered.   It was obtained by sintering a kneaded material containing 5 to 28% by volume of silicon carbide whisker, 60 to 80% by volume of vegetable carbon ceramic powder having a particle size of 20 to 60 μm, and the remainder being phenol resin powder. Characteristic ceramic material.   5 to 28% by volume of silicon carbide whisker having a diameter of 0.05 to 1.5 μm and a length of 20 to 80 μm, and 60 to 80% by volume of vegetable carbon ceramic powder having a particle size of 20 to 60 μm. A ceramic material obtained by sintering a kneaded material to be a phenol resin powder.   Silicon carbide whisker powder is subjected to surface silane coupling treatment to form a film of aminosilane-based silane coupling agent on the surface, and then a certain proportion of plant carbon ceramic powder with respect to the appropriate amount, and phenol resin as the balance thereof The method for producing a ceramic material according to any one of claims 1 to 4, wherein an appropriate amount of the powder is mixed, kneaded and appropriately shaped, and then sintered and produced in an inert gas atmosphere or vacuum.   6. The method for producing a ceramic material according to claim 5, wherein the silicon carbide whisker powder to be subjected to the coupling treatment has a diameter of 0.05 to 1.5 μm and a length of 20 to 80 μm.   The method for producing a ceramic material according to claim 5, wherein the vegetable carbon ceramic powder has a particle size of 20 to 60 µm.   6. The silicon carbide whisker powder to be subjected to coupling treatment has a diameter of 0.05 to 1.5 μm and a length of 20 to 80 μm, and the vegetable carbon ceramic powder has a particle size of 20 to 60 μm. The manufacturing method of the ceramic material of description.   The method for producing a ceramic material according to any one of claims 5 to 8, wherein the sintering temperature is 700 to 1,100 ° C.   The method for producing a ceramic material according to claim 9, wherein a blanking process is performed after vacuum pre-sintering in a range of 180 to 250 ° C prior to the sintering and production of claim 9.

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