JPS63170254A - Manufacture of ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to engine parts, gas turbine parts, mechanical parts,
The present invention relates to a method for manufacturing high-density fine ceramics useful for wear-resistant sliding members and the like.

(Prior art) Conventionally, in order to manufacture ceramics, as shown in the flowchart in Fig. 2, first, ceramic raw materials and sintering aids are mixed, crushed, and then crushed by pieces of cobblestone used in the crushing process. After passing through a 44μ sieve to remove foreign substances, the powder is granulated, water is added as required, and the mixture is molded using a mold press or cold isostatic press and sintered at a predetermined temperature. Obtaining a body.

(Problems to be Solved by the Invention) However, in the conventional ceramic manufacturing method described above, since the water content in the granulated powder is not actively made uniform, the water content in the granulated powder is There was a drawback that the amount of moisture varied. As a result, pores are generated in the compact due to uneven particle collapse due to variations in the amount of water in the granulated powder, which remain after sintering, making it difficult to obtain a high-strength ceramic sintered compact. There was a drawback that it could not be done.

In addition, in order to manufacture mechanical parts that conventionally require high density and high strength, hot press or hot isostatic press (I
IIP) has been used, but it has the drawback of being expensive and not suitable for mass production.

The purpose of the present invention is to eliminate the above-mentioned problems and provide a method for producing ceramics that allows high-strength, high-density ceramic sintered bodies to be fired at normal pressure without using methods such as hot pressing or HIP. It is something.

(Means for Solving the Problems) The method for producing ceramics of the present invention is a method for producing ceramics in which a ceramic raw material powder and a predetermined sintering aid are mixed, pulverized, granulated, shaped, and fired. The powder is once forcibly dried, and then water is added and/or passed through a sieve as necessary to form a uniform granulated powder having a predetermined moisture content. be.

(Function) In the above-mentioned configuration, by once forcibly drying the granulated powder and then adding moisture and/or passing it through a sieve as necessary, the granulated particles can be uniformly dried without any difference in moisture content between the granulated particles. A fine granulated powder can be obtained.

That is, by force drying the granulated powder and adding moisture, it is possible to make it into a homogeneous crushed state during molding and reduce the pores between the particles. As a result, by molding and firing the granulated powder thus obtained, for example, in a silicon nitride sintered body, even when sintered under pressure, the maximum pore diameter is 10μ or less, and the porosity is 0.5. % or less and the 4-point bending strength at room temperature is 1001
It is possible to obtain a ceramic sintered body with high strength and high density of 1.5 g/m" or more.

Here, it is preferable that the forced drying temperature is 60 to 100°C because it is difficult to achieve the desired drying state below 60°C.
This is because if the temperature exceeds 100°C, the auxiliary agent used for spray drying will harden, making it difficult to obtain a homogeneous crushed state of the granulated powder.

Furthermore, the raw material after pulverization is passed through a sieve of 32μ or less before granulation, or the granulated powder obtained by forced drying and adding moisture is
It is preferable to pass through a sieve with a size of 0μ or less because if a sieve with a mesh size larger than this is used, coarse particles after pulverization and foreign matter contained in the raw materials cannot be effectively removed, and the granulated powder will not be uniform. This is because it is difficult to maintain one's sexuality.

In addition, it is preferable that the amount of water added to the granulated powder is 0.5 to 5% by weight, because if it is less than 0.5% by weight, water will not be uniformly distributed between the granulated particles and a difference in water content will occur. It gets easier,
This is because if the amount exceeds 5% by weight, water oozes out from the surface of the molded product during molding, which tends to cause pressure distribution in the molded product.

Furthermore, the reason why granulation is preferably carried out by spray drying is to obtain a granular powder that can increase the packing density during molding.

Furthermore, PVA and PEG are used as auxiliary agents for spray drying.

MC and stearic acid are preferred because the granulated powder is less likely to harden or disintegrate due to forced drying or water addition.

In addition, raw material powders with an average particle size exceeding 2 μm require a long time to mix and grind, and during this time, impurities may be mixed in due to post-pulverization wear etc., which significantly deteriorates the properties and is not effective in increasing the density of the sintered body. 2 μm or less, preferably 1 μm
It is preferable to use the following fine raw materials.

(Example) FIG. 1 is a flowchart showing an example of the manufacturing method of the present invention. First, a ceramic raw material with an average particle diameter of preferably 2 μm or less and a sintering aid are mixed, crushed, and then passed through a sieve preferably with a diameter of 32 μm or less to remove coarse particles and foreign substances such as cobblestone fragments used during crushing. . Here, any sintering aid that can make the desired ceramic finely densified or highly strong can be used.

Next, after granulating to obtain a granulated powder having a water content of about 1% by weight, it is passed through a sieve as in the conventional method. Thereafter, the obtained granulated powder is preferably force-dried at a temperature of 60 to 100°C to obtain a homogeneous granulated powder with a moisture content of 0.2 to 0.5% by weight with little variation. Make it. Then 0.5 if necessary
~5.0% by weight of moisture is added to the granulated powder to obtain a granulated powder with a uniform moisture content, and then passed through a sieve preferably of 250μI or less to remove coarse particles that have aggregated due to the addition of moisture to form the granulated powder. Get a body.

The resulting granulated powder is molded by a conventional method and then fired, for example, under normal pressure, to obtain a high-strength, high-density ceramic sintered body having the characteristics of the present invention.

Examples will be described below.

As a sintering aid, 3 parts by weight of Mg0, parts by weight of Zrozl, and 100 parts by weight of 5isNa powder with an average particle size of 0.5 μm were added to the castor charcoal.
4 parts by weight of ENT and 1 part by weight of Sr were added and mixed, 60% moisture and cobblestones with a diameter of 5 to 10 nm were added thereto, and the mixture was mixed and pulverized for 4 hours using a batch type pulverizer.

Next, the mixed and pulverized slurry was prepared using a JIS standard with an opening of 32 μm.
After passing through a standard sieve, 2% by weight of PVA and 0.2% by weight of stearic acid were added and mixed as auxiliary agents for spray drying, and the average particle size was 80 μm and the water content was 1.0 to 0 by spray drying. It was made into a granulated powder of .5% by weight.

Furthermore, after drying the granulated powder for 24 hours at the temperature shown in the forced drying temperature in Table 1 using a constant temperature dryer and adding moisture as necessary, As shown <Sieve using JIS standard sieve and sample number 1~
Granulated powder No. 8 was obtained. 3ton/cm” of this granulated powder
Cold isostatic press molding at the pressure of 5Qm x 60dragon x 6m
A molded body of m was obtained.

Thereafter, after degreasing at a temperature of 500°C for 3 hours, this compact was subjected to normal pressure sintering at a temperature of 1700°C for 1 hour in a nitrogen gas atmosphere. ) was obtained. Separately, as a comparative example of the present invention, granulated powders of sample numbers 9 to 11 were prepared under the manufacturing conditions shown in Table 1 without performing forced drying, and were molded and fired under the same conditions. I got a body.

The bending strength, maximum pore diameter, and porosity of these sintered bodies were measured and shown in Table 1. In addition, the bending strength was measured by the four-point bending strength method of JIS R-1601r Fine Ceramics Bending Strength Test Method. The maximum pore diameter and porosity were measured by mirror-polishing the surface of the sintered body and using an optical microscope at a magnification of 400 times. The pore diameter was determined by measuring the maximum length of the pores, and the maximum pore diameter was determined by measuring the number of 1000 pores, and the maximum diameter among them was determined as the maximum pore diameter. Moreover, the porosity is a value obtained by actually measuring the area of 1000 measured pores, calculating the total pore area number, and dividing the total pore area by the total visual field area required for measurement.

As is clear from Table 1, the sintered body using the prepared raw material of the present invention, in which water was added as necessary after forced drying and passed through a sieve, had extremely high strength and fewer pores compared to the comparative example. It is clear that it is a sintered body.

Implementation ■1 100 parts by weight of ZrO□ powder with an average particle size of 1.8μ, 5 parts by weight of stabilizer YgOs, and sintering aid Al! 032 parts by weight of each raw material and 100 parts by weight of water were mixed and ground in a zirconia pot mill. Grinding was carried out for 1 hour as shown in Table 2.
The process was carried out for 10 hours and 30 hours, and then 1% by weight of PIE0, an auxiliary agent used in spray drying, was added to the mixed and pulverized slurry.
Granulated powders were each prepared by spray drying.

All of the granulated powder thus obtained was sampled, and the granulated powder was dried for 30 hours at the forced drying temperature shown in Table 2 using a dry air dryer, and water was added as necessary. After that, 1.5ton/arm” with a cold isostatic press machine.
A molded body of 60×60×6 cranes was obtained. Thereafter, the sintered bodies were dried, degreased, and fired at 1400° C. in the atmosphere to obtain sintered bodies of sample numbers 9 to 15, which are products of the present invention. Comparative example sample numbers 16 to 18 were prepared by producing sintered bodies in the same manner except that forced drying was not performed, and sintered bodies were pulverized for 48 hours without performing forced drying using ZrO with an average particle size of 3 μm. A sintered body was produced by the method described above to obtain Comparative Example Sample No. 19.

The bending strength and relative density of the obtained sintered body were measured and shown in Table 2. Incidentally, the bending strength was measured in the same manner as in Example 1 and was also measured further.

As a result, as shown in Table 2, in the products of the present invention, the relative density of the compact was increased and the strength was significantly improved, and a high-strength zirconia sintered body could be obtained by the method of the present invention.

Furthermore, it was found that in Comparative Example 19, in which the average particle size was 2 μm or more, the properties were deteriorated in terms of bending strength.

100 parts by weight of 5iC with an average particle size of 0.8 μm and sintering aid B
, 1.7 parts by weight of C, 0.8 parts by weight of carbon black and 150 parts by weight of water were added, and the mixture was mixed and pulverized for 8 hours in a batch type mixer/pulverizer. This slurry was divided into three equal parts, passed through a sieve with the mesh openings shown in Table 3, and 0.5% by weight of MC was added as a spray drying aid to each slurry. A granulated powder was obtained.

The obtained powder was divided into two parts, one part was dried at 90°C for 24 hours, the other part was left as is (no forced drying), and was press molded into a size of 60 x 60 x 10 m. Further, hydrostatic pressing was performed at a pressure of 5 ton/01 m''.Then, sintered bodies were produced by firing at a temperature of 2050°C in an argon atmosphere, and the sintered bodies of sample numbers 20 to 22, which are products of the present invention, were In addition, sintered bodies were prepared in the same manner except that forced drying was not performed to obtain sintered bodies of comparative sample numbers 23 to 25.

The bending strength and relative density of the obtained sintered body were determined in the same manner as in Example 2. The results are shown in Table 3.

Table 3 As is clear from the results, forced drying has excellent bending strength and relative density of the sintered compact, and the effect of making the sieve mesh finer after mixing and pulverization appears to improve the bending strength. In the present invention, it has been found that it is preferable to pass the pulverized raw material through a sieve of 32 μm or less before granulation.

(Effects of the Invention) As is clear from the above detailed explanation, according to the present invention, pressureless sintering is achieved by the synergistic effect of forced drying of granulated powder, addition of water as necessary, and/or sieving. Even in sintering, a high-strength, high-density fine ceramic sintered body with small maximum pore diameter and small porosity and excellent mechanical strength can be obtained industrially and at low cost. Therefore, it can be used for applications such as high-temperature bearings, engine parts, gas turbine parts, etc., and has extremely high industrial value.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an embodiment of the manufacturing method of the present invention, and FIG. 2 is a flowchart showing an example of manufacturing a conventional silicon nitride sintered body. Figure 1

Claims (1)

[Claims] 1. A method for manufacturing ceramics in which a ceramic raw material powder and a predetermined sintering aid are mixed, crushed, granulated, formed, and fired, wherein the granulated powder is once forcibly dried. A method for manufacturing ceramics, which comprises: adding water and/or passing through a sieve as necessary to obtain a uniform granulated powder having a predetermined water content. 2. The manufacturing method according to claim 1, wherein the forced drying temperature is 60 to 100°C. 3. The manufacturing method according to claim 1, wherein the pulverized raw material is passed through a sieve of 32 μm or less before granulation. 4. The manufacturing method according to claim 1, wherein the amount of water added is 0.5 to 5% by weight. 5. The manufacturing method according to claim 1, wherein the sieving after the forced drying is performed using a sieve of 250 μm or less. 6. The manufacturing method according to claim 1, wherein the raw material after mixing and pulverizing the ceramic has an average particle size of 1 μm or less. 7. The ceramics are Si_3N_4, ZrO_2,
The manufacturing method according to claim 1, which is SiC. 8. The manufacturing method according to claim 1, wherein the granulation is performed by spray drying. 9. Polyvinyl alcohol (PVA), polyethylene glycol (PEG) as auxiliary agents used in the spray drying.
9. The manufacturing method according to claim 8, which uses at least one of , methyl cellulose (MC), and stearic acid. 10. The manufacturing method according to claim 1, wherein the ceramic raw material powder has an average particle size of 2 μm or less.