JPH0331664B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an inorganic sintered ultra-precision measuring stand. One of the basics of machining is to maintain accurate standards, and the measuring table called a reference surface plate is used as the reference surface. In machine work, the position and dimensions of the workpiece are measured and determined on this surface plate, and the necessary markings are made and machined, but the equipment used for this marking work and measurement is moved on the surface plate. In order to accurately determine the position, it is important that it be light and able to move smoothly, and at the same time, the reference surface must not expand, contract, or deform due to temperature. Moreover, since it is used constantly, it is also necessary to have wear resistance. However, with conventionally used iron surface plates, the shape and dimensions change significantly due to temperature expansion.
To obtain high accuracy, a room with constant temperature and humidity is required. Natural stone surface plates made of gabbro are also used, but they have the drawback of not having sufficient hardness and wear resistance. The present invention aims to provide a measuring table that eliminates the drawbacks of conventional surface plates, and uses an inorganic sintered body made of oxide or non-oxide material and sintered at high temperature, that is, a certain type of ceramic. The measuring table is formed by the method, and is characterized by eliminating thermal deformation and having excellent hardness, corrosion resistance, heat resistance, and abrasion resistance. In addition, the measuring table of the present invention is composed of coarse grains with high hardness and appropriate surface area and volume, and medium grains and fine grains for adjusting pores, and the polished surface of the coarse grains provides a high precision standard. By forming a stable pressure-receiving surface that functions as a surface and dispersing it in a base material with adjusted pores, the surface is made porous with the same function as a kissing surface. It has characteristics. Ceramics made of fired ceramics mainly composed of fine alumina particles with a particle size of about 1 μm have a dense surface with no pores, and when polished to a mirror finish, other mirror-finished objects such as block gauges placed on the polished surface will It cannot be moved easily due to adsorption (ringing), and the fact that it is dense is a disadvantage in terms of workability. In order to eliminate these drawbacks, it is possible to use a material with a large particle size, but in that case, the ceramic loses the fineness required for an ultra-precision measuring table, and along with this, various other problems arise. will occur. On the other hand, in general, when filling a container with a large number of balls with multiple diameters such as large, medium, and small, in order to obtain the minimum void ratio, it is necessary to It is known that the optimal mixing ratio of spheres of different sizes is determined by Applying this concept to the particle size of ceramic materials makes it possible to control the density of ceramics and at the same time obtain an appropriate porosity. From this point of view, the present invention creates a stable pressure-receiving surface on the surface by selecting the optimum values for the particle size and mixing ratio of the materials that make up the ceramic, and at the same time adjusts the pores. It smoothes the sliding of specular objects on the surface, hardness,
It is characterized in that workability is also maintained appropriately. Hereinafter, the present invention will be explained in more detail with reference to the drawings. FIGS. 1 and 2 show a surface plate and a V-block as specific examples of the construction of the workbench of the present invention. The ceramic materials that make up these
corundum, alundum, mullite, silicon carbide,
or a mixture of multiple of these as the main component, with silicon nitride added as necessary, or additives for coloring as described below.
Aggregate formed by coarse particles of about 0.2 to 5 mm,
A base material made of fine particles of the same material with a particle size of 5 μm or less is used, and these are mixed in an appropriate ratio. In particular, the above-mentioned aggregate has a grain size of, for example, 5 mm and 2 mm.
Five types of aggregates, approximately mm, 1 mm, 0.5 mm, and 0.2 mm, are mixed and used as appropriate, and aggregates with smaller particle sizes are sequentially filled between aggregates with larger particles. Furthermore, a base material formed of fine particles is filled and bonded between them, and the particle size of these fine particles is 1 μm.
It is desirable to keep it below m, and if necessary, clay, feldspar, china clay, etc. can be mixed. Therefore, the porosity is adjusted by the particle size distribution of the aggregate, and if the porosity is increased by filling the base material between the relatively large aggregates, the porosity of the object to be measured, etc. It can improve slippage. In this case, the above aggregate is used on the polished working surface 1 of the surface plate or V-block.
An intermittent contact surface similar to the scraped surface of a casting surface plate is formed at a and 1b, and the object to be measured can easily slide against the work surface at this point. Further, by polishing the surface, the working surface exhibits a state in which a base material formed by fine particles is filled between a large number of relatively large aggregates, and the polished surface of the relatively large aggregates. However, in the base material with high porosity, it forms a stable pressure-receiving surface that functions as a precise reference surface, and the particle size of the aggregate must be selected appropriately. Furthermore, by appropriately selecting the particle size of the aggregate, the hardness and workability of the ceramic can be adjusted. It is appropriate to adjust the particle size and mixing ratio of the above-mentioned aggregate and base material so that the porosity will be 0.1 to 20% after sintering the ceramics, considering the intended use of the workbench. That is, when the porosity exceeds its upper limit,
The density of the ceramic will be impaired, and if the lower limit is exceeded, excessive adsorption (linking) will occur between the ceramic and other mirror-finished objects, impeding workability. In addition, the mixture of aggregate and base material mentioned above is molded into the shape shown in the drawing and sintered. A high hardness of HR _A 93-94 or higher can be obtained. The measuring table thus sintered is made into a product by lap-polishing its working surfaces 1a and 1b to make it flat.
In the above, the case where the measuring table of the present invention is constructed as a surface plate or a V-block has been described, but in addition to these, it can also be constructed as, for example, a tombstone or a bevel table. Note that if the ceramic is made relatively porous by adjusting the porosity as described above, the working surfaces 1a, 1
When the outer walls 2a, 2b, etc., except for b, are coated with plastic, the adhesion of the plastic is good, and external shocks can be absorbed and damage can be prevented. In the figure, 3a is a reinforcing rib. Furthermore, the measuring table can be colored appropriately to prevent eye fatigue or to indicate accuracy. For example, by pre-mixing 0.5-10% chromium, the measuring platform after sintering can be made blue, 1-8% iron can make it brown, and 0.5-10% iron can make it brown.
It can be colored black with ~5% iron and cobalt. As detailed above, according to the present invention, it is possible to provide an ultra-precision measuring stand that is not only free from thermal deformation but also has extremely high hardness and excellent corrosion resistance, heat resistance, and abrasion resistance at a low cost. be able to. Furthermore, according to the present invention, the particle size of corundum etc.
By mixing coarse particles with a particle size of 0.5 to 5 mm and fine particles with a particle size of 5 μm or less, it is easy to adjust the porosity of the mixture.
The sintering process was adjusted to 20%, and the work surface was polished to a flat surface, which prevents other mirror-finished objects from sliding on the surface, making it a stable pressure-receiving surface to serve as a precise reference surface, and for work. Surface hardness and workability are maintained extremely well. Next, examples of the present invention will be shown. In the experimental implementation, the ceramic material used was a mixture of aggregate consisting of coarse and medium particles of alumina (corundum) and a base material consisting of fine alumina powder, and a mixture of fine powder of porcelain material. there was. The above coarse particles have a particle size of 700~
Particle size of 50μm is 50-10μm as medium grain.
A fine powder with a particle size of 5 μm or less was used. The blending ratio of the above alumina coarse particles, medium particles, and fine particles is 20 to 30 wt% and 30 to 40 wt%.
%, mixed to be within the range of 35-50wt%,
Furthermore, 25 wt% of the porcelain material was mixed with 75 wt% of these aluminas. The above-mentioned mixture was sufficiently stirred and mixed, then compressed and calcined at 1350°C. The porosity of the sintered body fired with the above-mentioned composition could be adjusted to about 15%. The obtained sintered body exhibits various physical properties suitable for ultra-precision measuring tables. For example, the thermal expansion is relatively small, and the thermal expansion coefficient (25
~800℃1/℃×10 ^-6 ) is 7.4 to 8.0, whereas the above sintered body has a thermal expansion coefficient of 5.9 (25
~800°C1/°C×10 ^-6 ) could be obtained. In this way, the influence of thermal expansion is extremely small.
It is extremely advantageous as a material for ultra-precision measuring jigs and related components. Furthermore, the above-mentioned sintered body also exhibits a superior value in terms of coefficient of friction (vs. FC25) compared to general alumina products, as shown in Table 1.

[Table] In addition to these physical properties, the sintered body has countless fine pores formed on its surface due to the appropriate particle size distribution of the aggregate and base material, which makes it possible for other specular objects to be adsorbed. At the same time, it can reduce the coefficient of friction and improve slipperiness. Figures A and B in Figures 3 and 4 are micrographs of the ground and fractured surfaces of the sintered body, Figures A and B in Figures 5 and 6 are micrographs of alumina material with fine grain size as a comparative example. These are micrographs of the ground surface and fractured surface of a ceramic surface plate, with A in each figure being 350x magnification and B being 3500x magnification. It can be seen from all the enlarged photographs that a large number of pores are formed in the sintered body according to the present invention, whereas almost no pores are formed in the comparative example.

[Brief explanation of drawings]

1 and 2 are a partially cutaway perspective view of a surface plate and a perspective view of a V block showing an example of an embodiment of the present invention, and FIGS. 3 and 4 respectively A and B show an embodiment of the present invention. Micrographs substituted for drawings showing the particle bonding structure of the ground surface and fractured surface, Figures 5 and 6 A and B, respectively.
is a photomicrograph substituted for a drawing showing the particle bonding structure of a ground surface and a fractured surface in a comparative example.

Claims (1)

[Claims] 1 A mixture of coarse particles with a particle size of 0.2 to 5 mm and fine particles of the same material with a particle size of 5 μm or less, the main component of which is corundum, alundum, mullite, silicon carbide, or a mixture of multiple thereof, is mixed with a porosity of 0.1 to 5 μm. An inorganic sintered ultra-precision measuring table that is sintered at 1,300 to 1,500 degrees Celsius at a temperature of 20% and polished to a flat work surface.