JP5070142B2 - Fluid hydrostatic guide device component, tool support component, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a hydrostatic pressure guide bearing component, a tool support component, and a manufacturing method thereof.

  Hydrostatic pressure guide bearings form a lubricating fluid film by forcibly supplying a high-pressure lubricating fluid between a shaft that is a moving part and a bearing that is a fixed part. A bearing to support. A hydrostatic pressure guide bearing in which the lubricating fluid is air is called an aerostatic bearing, a hydrostatic fluid guide bearing in which the lubricating fluid is oil is an oil hydrostatic bearing, and a hydrostatic fluid guide bearing in which the lubricating fluid is water is water. Also called a hydrostatic bearing.

  In general, hydrostatic pressure guide bearings are widely used for the spindles of precision machine tools because they have almost no friction and therefore have extremely low torque due to rotational friction and high rotational accuracy. However, since the hydrostatic bearing used for the spindle of precision machine tools has a small gap of only a few μm, the member is thermally expanded and deformed by heat generated by high-speed rotation, and the bearing gap becomes small. Contact accidents are likely to occur. For this reason, Patent Documents 1 to 3 disclose techniques for producing a rotating shaft with a silicon nitride material having a small thermal expansion coefficient and high rigidity. Thereby, the fluctuation of the bearing gap at the time of rotation can be suppressed, and a contact accident can be prevented, and further, a change in rigidity accompanying a temperature change of the bearing can also be prevented. Further, in Patent Document 1, when the slider, which is the moving part of the linear guide device using the hydrostatic bearing, is made of ceramics such as silicon nitride, the inertial force generated when the moving part reciprocates is reduced. It is also disclosed that

  Patent Document 4 discloses a support device including a hydrostatic rotating shaft that can autonomously correct the inclination of an axis with a high restoring force, and a processing machine using the support device. If the material forming the static pressure surface of this device is ceramic such as silicon nitride or sialon, the coefficient of thermal expansion can be reduced to about 1/10 of that of steel, so that the static pressure gap cannot be easily changed. Furthermore, when the material is sialon or the like, the inclination of the axis can be corrected more easily, so that the position variation of the tool or workpiece can be reduced. In addition, since these materials have a very low specific gravity, it is said that high accuracy can be achieved by reducing drive energy and increasing the response speed in servo rotation drive.

  In Patent Document 5, a base of an air static pressure linear guide device used for a high-precision processing device, a high-precision measurement device, a semiconductor manufacturing device, or a semiconductor inspection device is made of ceramics or stone, and is mounted on the base. A technique for producing a suction rail to be manufactured using a low expansion casting having a thermal expansion coefficient equivalent to that of the base is disclosed. As a result, the so-called bimetal effect that the apparatus is deformed due to the difference in thermal expansion between the base and the suction rail is reduced, and a decrease in processing accuracy can be suppressed. Examples of ceramics include alumina, mullite, and silicon nitride materials.

In Patent Documents 6 to 8, in a precision multi-axis processing machine having a degree of freedom of three or more axes for cutting or grinding an optical element or a molding die thereof, the direct acting liquid static pressure slide is made of silicon nitride or sialon. A technique for manufacturing the above is disclosed. The coefficient of linear thermal expansion of silicon nitride or sialon at room temperature is 1.5 × 10 ⁻⁶ / K, which is about 1/10 that of steel materials. Therefore, the position of the tool or workpiece mounted on the hydrostatic slide depends on the temperature. It is said that it is hard to fluctuate. Further, silicon nitride or sialon has a fracture toughness of 6.0 MPam ^1/2 , which is relatively high among ceramics, so it is difficult to break, and its Young's modulus is about 290 GPa, which is about 2.5 times that of cast iron, so it is difficult to deform. It is said that it also has the advantage. Furthermore, since silicon nitride or sialon has a light specific gravity of 3.3, the control load such as inertia force generated at the time of slide driving is small, and the mechanical response is improved. Therefore, if the direct acting liquid hydrostatic slide is made of silicon nitride or sialon, the servo band of the apparatus is improved, the controllability is improved, and high-speed and high-precision machining can be realized.

  Patent Documents 9 and 10 disclose a direct-acting static pressure slide that is easy to remove and attach and uses water as a lubricating fluid. Ceramic guideways and slideways are disclosed as components constituting the linear motion hydrostatic slide, and alumina, mullite, and silicon nitride materials are disclosed as specific examples of ceramics.

As described above, sialon or silicon nitride material is useful as a static pressure rotating shaft or a linear motion static pressure slider member of an ultra-precision processing machine because of its low thermal expansion, high rigidity, and low specific gravity (light weight). It has been known.
Japanese Patent Publication No. 6-100226 JP-A-5-87143 JP-A-10-205537 JP 2006-52793 A JP 2000-136824 A JP 2005-88125 A JP 2006-29395 A JP 2006-52844 A JP 2007-78065 A JP2007-139021

  As shown in these patent documents, it has long been widely known that sialon or silicon nitride materials (hereinafter collectively referred to as “sialon or the like”) are useful as parts of ultraprecision machines. However, in reality, it is not widely used at all as a material for a rotating shaft or a slide of a tool table of an ultraprecision machine or a hydrostatic pressure guide device of an ultraprecision machine. The reason for this is that high-precision machining of sialon or the like is difficult, and the cost of parts made of sialon or the like is very high due to the difficulty of machining. Sialon and the like have been conventionally developed as members that require high strength at high temperatures, such as turbines, and high wear-resistant members such as tools. That is, sialon or the like is known as a difficult-to-work material because it has high strength and toughness among ceramic materials and has high mechanical strength even at high temperatures.

  Thus, sialon or the like, which is difficult to cut, is processed by grinding with a diamond grindstone or polishing with diamond free abrasive grains. However, grinding of sialon or the like has a problem that the cutting depth and tool moving speed cannot be increased because the grinding resistance is very high. Further, in this grinding, since the tool is easily clogged, it is necessary to dress the tool frequently. For this reason, when grinding using a grinding center or a cylindrical grinder, the processing time of tens to hundreds of times that of a metal material is required. For this reason, parts made by processing sialon or the like are expensive. Furthermore, since the grinding resistance is high and clogging of the grindstone is likely to occur, sialon and the like also have a problem that high-precision grinding is difficult. For example, a metal material can be processed into a cylindrical body with super high accuracy with a roundness of 0.1 μm or less with relative ease. However, Sialon and the like cannot be processed into a cylindrical body with such an extremely high accuracy.

Sialon and the like do not have sufficient workability in flat polishing (also referred to as “lapping”). For example, the volume removal speed when sialon or the like is subjected to surface polishing is 1/2 or less of the volume removal speed of 99.5% purity alumina. If the volume removal speed in the flat surface polishing is slow, the polishing time becomes long and flatness decreases due to surface sagging. Therefore, the time for correction, that is, the finishing time increases.
From the above, it can be said that difficult processability such as sialon prevents application to parts for ultra-precision processing machines.

  In view of these circumstances, an object of the present invention is to provide an optimal part for an ultra-precision processing machine including a sialon sintered body or a silicon nitride sintered body with greatly improved workability.

As a result of intensive studies, the inventors have found that a sialon sintered body or a silicon nitride sintered body obtained by a specific production method can solve the above problems, and completed the present invention. That is, the said subject is solved by the following this invention.
[1] A hydrostatic pressure guide device part or a tool support part including a sialon sintered body or a silicon nitride sintered body obtained by sintering a β-silicon nitride powder with a sintering aid added thereto.
[2] The bending strength of the sintered body is 400 to 600 MPa, the Young's modulus is 260 GPa or more, the thermal expansion coefficient at room temperature is 1.5 × 10 ⁻⁶ / K or less, and the specific gravity is 3.27 or less. [1].
[3] The part according to [1] or [2], wherein the sintered body has a fracture toughness value by SEPB method of 4 to 5.5 MPa · m ^1/2 .
[4] The grinding resistance of the sintered body is 80% of the grinding resistance in grinding of a sialon sintered body or a silicon nitride sintered body obtained by sintering a α-silicon nitride powder with a sintering aid added thereto. And
The volume removal speed in polishing using a lapping machine of the sintered body is the same as that in polishing of a sialon sintered body or a silicon nitride sintered body formed by adding a sintering aid to α-silicon nitride powder and sintering. The component according to any one of [1] to [3], which is 1.5 times or more the volume removal speed.
[5] The component according to any one of [1] to [4], wherein the β-silicon nitride powder has a β-type crystal ratio in a crystal portion of 80% or more.
[6] The component according to any one of [1] to [5], wherein the sintered body has an equiaxed crystal structure.
[7] The fluid hydrostatic guide device component is a guide component, a slider component, or a table component of a linear guide device using an oil hydrostatic bearing, a hydrostatic bearing or an air hydrostatic bearing, or
[1] to [6], which is a shaft component, a bearing housing component, a bearing thrust plate component, or a table component of a rotary shaft device using an oil hydrostatic bearing, a hydrostatic bearing or an air hydrostatic bearing. Parts.
[8] The component according to any one of [1] to [7], wherein the tool support component is a tool table that holds a tool or a tool table that holds a tool table.
[9] including a step of preparing a sialon sintered body or a silicon nitride sintered body obtained by adding a sintering aid to β-silicon nitride powder and sintering, and a step of grinding or polishing the sintered body , Fluid hydrostatic guide bearing component, or tool support component manufacturing method.

  According to the present invention, it is possible to provide an optimal part for an ultra-precision processing machine including a sialon sintered body or a silicon nitride sintered body with greatly improved workability.

1. Sintered body of the present invention The hydrostatic pressure guide bearing part or tool support part of the present invention comprises a sialon sintered body or silicon nitride sintered body obtained by sintering a β-silicon nitride powder with a sintering aid added thereto. It is characterized by including.
Silicon nitride has two crystal types, α-type (hexagonal) and β-type (hexagonal). It is known that α-type is generated at a relatively low temperature and β-type is generated at a high temperature. Usually, a sialon or silicon nitride sintered body is obtained by sintering α-type silicon nitride powder (α-Si ₃ N ₄ powder) or β-type silicon nitride powder (β-Si ₃ N ₄ powder). Whichever raw material is used, it is known that the obtained sintered body is β-type. That is, a silicon nitride sintered body obtained by sintering α-Si ₃ N ₄ powder or β-Si ₃ N ₄ powder is β-Si ₃ N ₄ , and a sialon sintered body is β-sialon.
β-sialon is a solid solution in which Al (aluminum) and O (oxygen) are dissolved in β-Si ₃ N ₄ , and is generally represented by the formula Si _6-Z Al _Z ON _8-Z (Z ≦ 4.2). expressed. Most sialon or silicon nitride sintered bodies currently produced start with α-Si ₃ N ₄ powder.

The sialon or silicon nitride sintered body is obtained by sintering α-Si ₃ N ₄ powder or the like at 1700 to 1800 ° C. in a nitrogen atmosphere. In sintering, an oxide added as a sintering aid and silica on the surface of the silicon nitride powder form a liquid phase, and silicon nitride is once dissolved in the liquid phase and then precipitated. This sintering proceeds through a so-called dissolution reprecipitation process. In the present invention, the symbol “˜” includes values at both ends thereof.
When α-Si ₃ N ₄ powder is used as a starting material, Si ₃ N ₄ undergoes a crystal phase transition from α-type to β-type during this dissolution and re-precipitation process. At this time, a lot of needle-like (long plate-like) crystals of Si ₃ N ₄ are generated, and a cross-structure of needle-like (long plate-like) crystals is formed. Since this crystal structure is included, a sintered body obtained by sintering α-Si ₃ N ₄ powder is considered to have high strength and high toughness. The sialon or silicon nitride sintered body thus produced has excellent mechanical performance, but has very low workability. Hereinafter, a sialon or silicon nitride sintered body obtained by sintering an α-Si ₃ N ₄ powder in the presence of a sintering aid is also referred to as an “α raw material type sintered body”.

On the other hand, when β-Si ₃ N ₄ powder is sintered in the presence of a sintering aid, the phase transition from α-type to β-type of Si ₃ N ₄ does not occur. Generation is suppressed. For this reason, the crystal structure is equiaxed or platelet-shaped. Such a sintered body is excellent in workability because it has lower strength and toughness than a sintered body including a cross-structure of acicular crystals. Hereinafter, a sialon or silicon nitride sintered body obtained by sintering β-Si ₃ N ₄ powder in the presence of a sintering aid is also referred to as “sintered body of the present invention”. The proportion of the equiaxed crystal structure contained in the sintered body of the present invention is preferably 85% or more, and more preferably 95% or more. The proportion of the equiaxed crystal structure is determined by aspect ratio measurement by image analysis of an electron microscope.
The mechanical performance and workability of the crystal of the present invention vary depending on the proportion of β-type crystals in the crystal portion of β-Si ₃ N ₄ used as a raw material and the sintering conditions. A method for manufacturing the sintered body will be described later.

When the strength and toughness of the sintered body are low, the workability is excellent. On the other hand, when the strength and toughness are low, the reliability of the parts is reduced. When the sintered body of the present invention has a bending strength of less than 400 MPa and a toughness of less than 4 MPa · m ^1/2, it is easy to grind and polish, but chipping and chipping easily occur during processing, and Reliability is also likely to decline. Moreover, when the bending strength exceeds 600 MPa or the toughness exceeds 5.5 MPa · m ^1/2 , the sintered body of the present invention is difficult to grind and polish. The bending strength of the sintered body of the present invention is preferably 400 to 600 MPa, and the fracture toughness is preferably 4 to 5.5 MPa · m ^1/2 in view of workability and reliability when used as a part. The bending strength is determined according to JIS R1601. Fracture toughness is determined by the SEPB method (Single Edge Precracked Beam method) of JIS R1607.

The Young's modulus of the sintered body of the present invention is preferably 260 GPa or more, and more preferably 275 GPa or more and 320 GPa or less. A sintered body having a Young's modulus in this range gives a component that is less likely to undergo dimensional changes due to external force because of its high rigidity. The Young's modulus is determined according to JIS R1602.
Further, the thermal expansion coefficient of the sintered body of the present invention at room temperature is preferably 1.5 × 10 ⁻⁶ / K or less, more preferably 1.0 × 10 ⁻⁶ / K or more and 1.5 × 10 ⁻⁶ / K or less. preferable. The sintered body of the present invention having a thermal expansion coefficient at room temperature in this range gives a component in which dimensional change, position change, deformation, and change with time are suppressed. A thermal expansion coefficient is calculated | required based on JISR3251.
Furthermore, the specific gravity of the sintered body of the present invention is preferably 3.27 or less, more preferably 3.0 or more and 3.27 or less. Since the sintered body of the present invention having a specific gravity within this range can reduce the inertial force generated during driving, it provides a device with a small control load and an improved mechanical response. Furthermore, such a component provides a device with excellent controllability to improve the servo bandwidth of the motor. When a sintered body having a specific gravity within the above range is used as a part, an apparatus that achieves both high speed and high precision workability can be obtained. Specific gravity is calculated | required based on JISR1634.

2. The hydrostatic pressure guide bearing component or tool support component of the present invention The hydrostatic pressure guide device component or tool support component of the present invention (hereinafter also referred to as "the component of the present invention") is the sintered component of the present invention described above. Including the body. That the part of the present invention includes the sintered body of the present invention means that all or part of the part is composed of the sintered body of the present invention.

(1) Fluid static pressure guide device component The fluid static pressure guide device component is a component of the fluid static pressure guide device. As described above, the hydrostatic pressure guide device forms a lubricating fluid film by forcibly supplying a high-pressure lubricating fluid between a moving body (rotating shaft or slide) and a stationary body (bearing or guide). It is a bearing that supports a shaft by generating a load with a film. Preferred examples of the hydrostatic pressure guide device component include a linear guide device component using an oil hydrostatic bearing, a hydrostatic bearing, or an air hydrostatic bearing. A linear guide device using an oil hydrostatic bearing, a hydrostatic bearing or an air hydrostatic bearing is a device comprising a guide (fixed body) and a slider (moving body) that can move in the linear guide direction along the guide. In this apparatus, oil / water or air is supplied as a bearing fluid between the guide and the slider. The slider may have a table for holding a tool or the like. The sintered body of the present invention is suitable for these guide, slider, and table parts.
FIG. 1 is a schematic cross-sectional view of a linear guide. (A) in FIG. 1A, (C), (D), and (E) in FIG. 1b are types in which the guide is held by a slider, and (B) in FIG. Indicates the type in which the slider is held by a guide. In FIGS. 1a and 1b, 1 is a slider, 3 is a guide, 5 is a bearing (sometimes referred to as “bearing”), 7 is a base, 10 is a table, 12 is a tool, 14 is a tool base, and 16 is a linear motor. It is.

The sintered body of the present invention is particularly useful as a part of a device that is driven by a linear motor by an oil static pressure guide, a water static pressure guide, or an air static pressure guide (see FIG. 1A (A)). This is because in the linear motor drive device, if the moving body (slider 1, table 10, etc.) is reduced in weight, the power of the linear motor 16 can be reduced, so that the heat generated by the linear motor 16 can be greatly reduced. When the heat generation of the linear motor 16 is reduced, the dimensional change due to the temperature of each component constituting the apparatus is also reduced, so that the drift over time of the processing machine can be greatly reduced.
In general, since the static pressure guide device has a very small coefficient of friction, lost motion when the slider 1 is reversed and a change in the posture of the slider 1 are serious problems. However, when the weight of the slider 1 or the like is reduced, these lost motions and changes in posture can be greatly reduced, and the pattern generated on the processed product surface can be greatly reduced. That is, since the specific gravity of the sintered body of the present invention is as small as 40% of cast iron, even if only the material of the mobile component is replaced with the sintered body of the present invention from the cast iron as it is, the weight of the mobile component is 40% of the current weight. %, And the advantages as described above can be obtained. Furthermore, since the sintered body of the present invention has a rigidity as high as twice or more that of cast iron, the thickness of the parts can be reduced. Therefore, the weight of the part can be further reduced, and the weight of the part can be reduced to 1/10 of the cast iron part.

  Furthermore, in a linear guide device using a hydrostatic bearing or the like, the slider 1 moves along the shape of the guide 3, so that the motion accuracy of the slider 1 is determined by the shape of the guide 3. Therefore, when the shape of the guide 3 changes, the movement accuracy of the tool is likely to decrease. For this reason, it is necessary to reduce the change in the shape of the guide 3. However, generally, a linear motor 16 is installed in the vicinity of the guide 3. Therefore, when the temperature of the guide 3 changes due to the heat generated by the linear motor 16, the shape of the guide 3 changes due to thermal expansion. In that respect, when the sintered body of the present invention having a thermal expansion coefficient of 1/10 that of cast iron is applied to the guide 3, the above-described problems are unlikely to occur and high-precision processing is possible.

  Another preferred example of the hydrostatic pressure guide device component includes a rotary shaft device component using an oil hydrostatic bearing, a hydrostatic bearing or an air hydrostatic bearing. A rotary shaft device using an oil hydrostatic bearing, a water hydrostatic bearing or an air hydrostatic bearing is a device comprising a rotary shaft and a bearing that rotatably positions and holds the shaft. It is a device that supplies oil, water or air between them. This rotary shaft device may have a bearing housing that receives the radial direction of the rotating body, a bearing thrust plate that receives the force acting in the axial direction of the rotating body, or a tool table that holds a tool or the like. . FIG. 2 is a schematic cross-sectional view of an example of a rotary shaft device using an oil hydrostatic bearing, a water hydrostatic bearing, or an air hydrostatic bearing. In FIG. 2, 20 is a rotating shaft, 22 is a bearing housing, 23 is a bearing thrust plate, and other symbols are defined as in FIG. The sintered body of the present invention is suitable for these parts. The rotating shaft device including these components has the same merit as the linear guide device. The linear guide device slider (1 in FIGS. 1a and 1b) is connected to the shaft of the rotary shaft device (20 in FIG. 2) and the bearing thrust plate (23 in FIG. 2). 3) corresponds to the bearing housing (22 in FIG. 2) of the rotary shaft device.

(2) Tool support component The tool support component of this invention contains the sintered compact of the above-mentioned this invention. The tool support component refers to a tool table that holds a tool or a tool table that holds a tool table. The tool is a tool for processing an object. In the present invention, the tool is a cutting tool or a grindstone for cutting or grinding an object. The tool table may include a device that can finely adjust the position. Such a tool table is also called a fine adjustment table.
Since the tool table and the tool table may be directly exposed to grinding fluid or grinding mist during processing, the shape is likely to change due to temperature changes. For this reason, if the sintered body of the present invention having a thermal expansion coefficient of 1/10 of cast iron and 1/18 of aluminum is applied to these parts, the shape change due to temperature change can be reduced, so that high-precision processing is possible. It becomes possible. The tool table and the tool table may be provided on a slider (1 in FIGS. 1a and 1b) of the hydrostatic pressure guide device component.

(3) Ultra-precision machine The parts of the present invention are suitable as parts of an ultra-precision machine. The ultra-precision processing machine refers to a machine for processing optical materials, molds for molding them, and semiconductor materials on the nanometer order. Examples of the ultra-precision machine include a precision multi-axis machine having a machining degree of 3 axes or more.

3. Manufacturing method of component of the present invention The component of the present invention includes (1) a step of preparing a sialon sintered body or silicon nitride sintered by adding a sintering aid to β-silicon nitride powder and sintering, and (2) It is preferable to manufacture through a step of grinding or polishing the sintered body.

Step (1) In this step, a sialon sintered body or a silicon nitride sintered body obtained by adding a sintering aid to β-silicon nitride powder and sintering it is prepared. Preparing includes adding a sintering aid to β-silicon nitride powder and sintering to produce a sintered body. Hereinafter, the manufacturing method of the sintered compact of this invention is demonstrated.
The raw material β-type silicon nitride powder (β-Si ₃ N ₄ powder) may be prepared by purchasing a commercial product. In the β-Si ₃ N ₄ powder, the proportion of β-type crystals in the crystal portion is preferably 80% or more, and more preferably 90% or more. When such a powder is used as a raw material, a sintered body having excellent workability and excellent balance of mechanical properties when used as a part can be obtained. The proportion of β-type crystals in the crystal portion of β-Si ₃ N ₄ powder can be determined by a powder X-ray diffraction method. The average particle size of the _β-Si 3 _{N 4} powder is not particularly limited, but preferably 0.1 to 3 m. The average particle diameter is determined by a laser diffraction scattering method.

  The production method of the present invention uses a sintering aid. The sintering aid is a substance added for the purpose of promoting and stabilizing the sintering. Known sintering aids may be used, examples of which include yttrium oxide, alumina, aluminum nitride and aluminum nitride polytypes. The amount of the sintering aid added is usually about 5 to 15% by weight in the total of the raw material powder and the sintering aid, but in the present invention, 7% in the total of the raw material powder and the sintering aid. ˜12% by weight is preferred. This is because when the amount of the sintering aid is within the above range, the sintered body of the present invention is easily obtained.

It is preferable that the β-Si ₃ N ₄ powder and the sintering aid are mixed in advance and sintered. Sintering is preferably carried out at 1700-1800 ° C. in nitrogen.

Step (2) In this step, the sintered body of the present invention obtained in the above step is ground or polished. The sintered body of the present invention is preferably polished after surface grinding. Thus, the parts having a high-precision surface finish are suitable for slider parts and table parts. The surface grinding process may be performed by a known method using a surface grinding machine.
As described above, the sintered body of the present invention has extremely excellent workability compared to the α raw material type sintered body. The workability in grinding can be evaluated by measuring the grinding resistance in the normal direction of the ground surface during grinding with a known dynamometer. The grinding resistance of the sintered body of the present invention is preferably 80% or less of the grinding resistance when the α raw material type sintered body is ground under the same conditions. The grinding resistance may be measured in surface grinding, cylindrical grinding or free-form surface grinding. The α raw material type sintered body used for comparison of workability at this time and the sintered body of the present invention are those sintered under the same conditions except that the crystal structure of the sintered raw material is different. For example, the particle size of the raw material powder, the type and amount of the sintering aid, the sintering temperature, and the sintering atmosphere are the same.

  Moreover, it is preferable that the sintered body of the present invention that has undergone planar processing is finished with flatness, parallelism, or squareness by subsequent polishing using a lapping machine. In general, for polishing ceramics, a lapping machine made of cast iron or copper and free abrasive grains of diamond are used. The diamond abrasive used at this time has a particle size of 10 μm or less, and is extremely fine. For this reason, when the α raw material type sintered body is polished using a lapping machine, the volume reduction per hour in polishing (also referred to as “volume removal speed”) is not fast. Increasing the grain size of the abrasive grains improves the volume removal speed of the sintered body, but increases the surface roughness. A component having a rough surface is not suitable for a guide or a bearing surface of a hydrostatic pressure guide device or the like. However, since the sintered body of the present invention has excellent workability, the volume removal speed is faster than that of the α raw material type sintered body even when the above-mentioned fine abrasive grains are used for polishing. The volume removal speed in the polishing using the lapping machine of the sintered body of the present invention is preferably 1.5 times or more the volume removal speed when the α raw material type sintered body is polished under the same conditions. More specifically, the volume removal speed is obtained by polishing a plane that has been adjusted to a certain degree of flatness (about 1 μm) and surface roughness (Ra = 0.4 μm) in advance. The flatness is measured with a laser interferometer, and the surface roughness is measured with a surface roughness meter based on JIS B 0651. As described above, the α raw material type sintered body used for comparison of the workability and the sintered body of the present invention are those sintered under the same conditions except that the crystal structure of the sintered raw material is different.

  The sintered body of the present invention may be processed into a cylindrical body. When the sintered body of the present invention is processed into a cylindrical body, it is preferable to perform grinding using a cylindrical grinder. Since the cylindrical surface cannot be finished and polished with loose abrasive grains unlike a flat surface, it needs to be finished with high precision only by grinding. In particular, when the sintered body of the present invention is processed into a rotating shaft or a bearing housing of an ultra-precision processing machine, ultra-high precision grinding with a roundness of 0.1 μm or less is required. In general, in such processing that requires ultra-high precision, the influence of elastic deformation of the grindstone shaft for machining the sintered body of the present invention and the grindstone bond layer has a significant effect on accuracy degradation. At this time, when the grinding resistance of the workpiece is large, the elastic deformation of the grindstone shaft dented or the grindstone bond layer becomes larger, and the processing accuracy may be further lowered. Since the α raw material type sintered body has a very high grinding resistance compared to a metal material and considerably higher than other ceramic materials, it is extremely difficult to process it into a cylindrical body with high accuracy. In this respect, the sintered body of the present invention can reduce the grinding resistance as compared with the α raw material type sintered body, and can be processed into a cylindrical body with high accuracy. In the sintered body of the present invention, the grinding resistance in such grinding is preferably 80% or less compared to the grinding resistance when the α raw material type sintered body is ground under the same conditions.

[Example A]
Using β-Si ₃ N ₄ powder as a starting material, using yttrium oxide, aluminum oxide, and aluminum nitride polytype as a sintering aid, β = β = Z = 0.5 under normal pressure sintering conditions of 1700 to 1800 ° C. A sialon sintered body was produced.
[Comparative Example B]
A β-sialon sintered body with Z = 0.5 was produced in the same manner as in Example A except that α-Si ₃ N ₄ powder was used instead of β-Si ₃ N ₄ powder.
[Comparative Example C]
Using β-Si ₃ N ₄ powder as a starting material, 5 wt% of yttrium oxide and 5 wt% of alumina as sintering aids, a β-Si ₃ N ₄ sintered body is produced under conditions of normal pressure sintering at 1700 to 1800 ° C. did.

The mechanical properties and the like of these sintered bodies were evaluated according to the standards already described and are shown in Table 1.
The sintered body obtained in Example A had a bending strength of 490 MPa and a fracture toughness value of 4.5 MPa · m ^1/2 . On the other hand, the bending strength of the sintered body obtained in Comparative Example B is 700 MPa, the fracture toughness value is 6.2 MPa · m ^1/2 , the bending strength of the sintered body obtained in Comparative Example C is 880 MPa, and the fracture toughness value is 6. A high bending strength and fracture toughness value of 8 MPa · m ^1/2 were exhibited.

The sintered body thus obtained was processed under the following conditions to evaluate workability.
<Polishing test>
The sintered body obtained in each example was surface ground to flatness = 1 μm and surface roughness Ra = 0.4 μm to obtain a test piece. Thereafter, this test piece was polished. Polishing was performed using a lapping machine made of cast iron and diamond slurry having an average particle diameter of 6 μm as abrasive grains. The surface pressure at the time of polishing was adjusted using a heavy stone so as to be 6 N / cm ² .
The results are shown in FIG. FIG. 3 shows the correlation between the polishing time and the removal volume, and the slope represents the volume removal speed, that is, the workability (also referred to as “working efficiency”). The volume removal speed calculated from FIG. 3 is 1.28 for the sintered body of Comparative Example C having the worst processing efficiency, and 1.2 for the sintered body of Comparative Example B, and 2. 42. In other words, the volume removal speed of the sialon sintered body of the present invention obtained by sintering β-Si ₃ N ₄ powder in the presence of a sintering aid is the same as that of Comparative Example C, which is α-source silicon nitride. It was found to be 2.4 times that of the sintered body and 1.9 times that of the sintered body of Comparative Example B, which is an α material type sialon.

<Grinding test>
The sintered body obtained in each example was surface ground to obtain a rectangular parallelepiped test piece having a width of 100 mm, a length of 100 mm, and a thickness of 18 mm. The side surface of this test piece had a flatness = 2 μm and a surface roughness Ra = 0.8 μm. Next, this side surface (18 × 100 mm) was ground using a φ10 diamond grindstone # 140, and its workability was evaluated. The grinding conditions at this time were a grinding wheel rotation speed of 8000 rpm, a rotation direction down cut, a cutting depth of 0.04 mm / time, and a grinding feed speed of 500 mm / min. Grinding resistance was measured with a Kistler dynamometer. The results are shown in FIG. FIG. 4 shows the relationship between the grinding resistance in the normal direction and the removal volume during processing. As can be seen, the grinding resistance of the sintered body of Example A is about 75% of the sintered body of Comparative Example C in the initial stage and 70% or less of the sintered body of Comparative Example C in the final stage. there were.

<Precision cylindrical grinding test>
The sintered body of Example A and the sintered body of Comparative Example C were subjected to a cylindrical grinder to produce a φ100 × 60 mm column. At this time, the final finishing was performed by using a resin bond # 1500 diamond grindstone as a grindstone, precisely truing and dressing, and then the grindstone peripheral speed was 2000 m / min. The roundness measurement results after finishing are shown in FIGS. The roundness was measured according to JIS B 7451. The circularity of the cylinder obtained by grinding the sintered body of Example A was 0.08 μm, indicating that extremely precise roundness processing is possible. On the other hand, the roundness of the cylinder obtained by grinding the sintered body of Comparative Example C was 0.34 μm, indicating that precise roundness processing was difficult.

These results are summarized in Table 1.

  According to the present invention, it is possible to provide an optimal part for an ultra-precision processing machine including a sialon sintered body or a silicon nitride sintered body with greatly improved workability.

Cross-sectional schematic diagram of an example of a linear guide device using an oil hydrostatic bearing, water hydrostatic bearing or air hydrostatic bearing Cross-sectional schematic diagram of an example of a linear guide device using an oil hydrostatic bearing, water hydrostatic bearing or air hydrostatic bearing Cross-sectional schematic diagram of an example of a rotating shaft device using an oil hydrostatic bearing, a hydrostatic bearing or an air hydrostatic bearing Diagram showing the relationship between polishing time and removal volume Diagram showing the relationship between normal grinding resistance and removal volume The figure showing the measurement result of the roundness of the cylinder obtained by grinding the sintered compact of Example A The figure showing the measurement result of the roundness of the cylinder obtained by grinding the sintered compact of the comparative example C

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slider 3 Guide 5 Bearing 7 Base 10 Table 12 Tool 14 Tool base 16 Linear motor 20 Rotating shaft 22 Bearing housing 23 Bearing thrust plate

Claims (8)

β- silicon nitride powder by adding a sintering aid composed of sintered Sialon sintered body or a silicon nitride sintered body only contains,
The sintered body has a bending strength of 400 to 600 MPa, a Young's modulus of 260 GPa or more, a thermal expansion coefficient at room temperature of 1.5 × 10 ⁻⁶ / K or less, and a specific gravity of 3.27 or less. Pressure guide device parts or tool support parts. The component according to claim 1, wherein a fracture toughness value of the sintered body by a SEPB method is 4 to 5.5 MPa · m ^1/2 . The grinding resistance of the sintered body is 80% or less of the grinding resistance in the grinding of a sialon sintered body or a silicon nitride sintered body obtained by adding a sintering aid to α-silicon nitride powder and sintering. ,And,
The volume removal speed in polishing using a lapping machine of the sintered body is the same as that in polishing of a sialon sintered body or a silicon nitride sintered body formed by adding a sintering aid to α-silicon nitride powder and sintering. The component according to claim 1 or 2, wherein the component is 1.5 times or more the volume removal speed. The component according to any one of claims 1 to 3, wherein the β-silicon nitride powder has a β-type crystal ratio in a crystal portion of 80% or more. The component according to any one of claims 1 to 4, wherein the sintered body has an equiaxed crystal structure. The hydrostatic pressure guide device component is a guide component, a slider component, or a table component of a linear guide device using an oil hydrostatic bearing, a hydrostatic bearing or an air hydrostatic bearing, or
The shaft component, bearing housing component, bearing thrust plate component, or table component of a rotary shaft device using an oil hydrostatic bearing, a hydrostatic bearing, or an air hydrostatic bearing, according to any one of claims 1 to 5. The listed parts. The said tool support component is a component as described in any one of Claims 1-6 which is a tool stand holding a tool, or a tool table holding a tool stand. A hydrostatic pressure guide device component according to any one of claims 1 to 7, or a method of manufacturing a tool support component,
including a step of preparing a sialon sintered body or a silicon nitride sintered body obtained by adding a sintering aid to a β-silicon nitride powder and sintering, and a step of grinding or polishing the sintered body. A method of manufacturing a pressure guide device part or a tool support part.

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