JP2019073410A - Method of manufacturing sintered body - Google Patents

Abstract

To provide a method of manufacturing a sintered body capable of easily manufacturing a spherical sintered body with high sphericity and few impurities.SOLUTION: In an embodiment of this invention, a molded body 17 is made as follows. A slurry prepared by mixing a raw material powder, a first liquid (i.e., a dispersion liquid), and a gelling agent is charged into a second liquid (i.e., a molding liquid) in a cylinder 9 of a dropping device 5 to form an intermediate 15, and the intermediate 15 can be solidified by the gelling agent to form a solid, which is the molded body 17. For example, the slurry is dropped into the cylinder 9 containing the second liquid whose temperature is lower at the lower part than at the upper part, to form the intermediate 15, and when the intermediate 15 sinks in the second liquid, the gelling agent is used to solidify the intermediate body 15 to produce the molded body 17.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a method for producing a sintered body capable of producing a sintered body or the like composed of a spherical ceramic or a sintered alloy, for example, as a bearing.

Heretofore, ceramic balls made of, for example, a ceramic sintered body have been known as spherical objects such as bearings.
As a method of manufacturing this type of ceramic ball, for example, a method is known in which a spherical shaped body is produced by uniaxial press forming method in which ceramic powder is pressed in a uniaxial direction, and the shaped body is fired (Patent Document 1) reference).

There is also known a method of producing a spherical shaped body made of a ceramic material using a rolling granulation method and firing the shaped body (see Patent Document 2).
Furthermore, a method is also known in which granules of a ceramic material are produced using a spray granulation method by spray drying, a spherical shaped body is produced using the granules, and the shaped body is fired using HIP or the like. (See Patent Document 3).

JP, 2013-209283, A Japanese Patent Application Laid-Open No. 2002-12470 JP 2001-278670 A

By the way, in the above-mentioned prior art, there are the following problems, and their improvement has been demanded.
For example, when a spherical shaped body is produced by uniaxial press molding using a mold and the shaped body is fired to produce a sintered body, the sintered body is usually between the upper and lower molds. An annular band is formed along. Therefore, in order to increase the sphericity of the sintered body, it is necessary to remove the band by polishing or the like, so there is a problem that the manufacturing process becomes complicated and it takes time and cost.
In addition, in the case of producing a spherical shaped body using the rolling granulation method, for example, in the case of a large shaped body having a diameter of more than 3 mm, the forming time becomes long and it is not realistic. Moreover, when producing a molded object by the rolling granulation method, a large dispersion | variation exists in a dimension normally. Therefore, since it is necessary to grind a sintered compact for a long time in order to set it as the target size, manufacture takes time and there also exists a problem that manufacturing time becomes long. Furthermore, since the rolling granulation method is a method of stacking powders in layers, there is also a problem that impurities are easily mixed.

Furthermore, when the spray granulation method is used, there is also a problem that impurities are likely to be mixed when the material of the granules is produced to form a compact.
This indication is made in view of the above-mentioned subject, and the purpose provides the manufacturing method of the sintered compact which can manufacture spherical sintered compact with high sphericity and few impurities easily easily. It is to do.

(1) A first aspect of the present disclosure relates to a method for producing a sintered body in which a spherical body is produced using a raw material powder of ceramic or sintered alloy, and the body is fired to produce a spherical sintered body. It is a thing.
The method of manufacturing this sintered body is a slurry obtained by mixing the raw material powder of the ceramic or the sintered alloy, the first liquid which is the dispersion medium of the raw material powder, and the gelling agent of the first liquid. The step of preparing, and charging the slurry into a second liquid not soluble in the first liquid in the slurry to form a spherical intermediate by the surface tension of the slurry, and the gelling agent using the gelling agent. The method comprises the steps of solidifying the intermediate to produce a formed body, drying the formed body to produce a dried body, and firing the dried body.

  In the first aspect, a slurry prepared by mixing the raw material powder described above, the first liquid (i.e., the dispersion liquid), and the gelling agent is charged into the second liquid (i.e., the molding liquid) to prepare an intermediate. The intermediate can be solidified by the gelling agent to form a molded body which is a solidified body.

Therefore, it is possible to easily manufacture a spherical sintered body having high sphericity and few impurities by drying and firing this molded body.
Specifically, in the first aspect, since the slurry is dropped into the second liquid and gelation is sufficiently performed to the inside of the intermediate to produce a molded body, it was manufactured using a conventional uniaxial press molding method There is no annular band like one. Therefore, there is an advantage that sphericity is high. Moreover, since the process for removing the band is unnecessary, the manufacturing process can be simplified, and the labor and cost can be reduced.

  For example, even in the case of producing a large spherical sintered body having a diameter of more than 3 mm, rolling granulation for a long time such as rolling granulation method is not necessary, and the sintered body is easily manufactured in a short time. can do. And since rolling granulation is not performed, there is little fear of mixing of an impurity.

Furthermore, as in the case of the spray granulation method, there is little possibility that the impurities are mixed in the compact or the like.
Moreover, when producing a molded object using the granules obtained by the spray granulation method (however, in this case, drying is not necessary), gaps (triple points) between the granules remain as pores in the sintered body. As a result, the strength of the sintered body may be reduced. However, in the first aspect, there is an advantage that the strength of the sintered body is high because such a triple point does not exist.

  As described above, according to the first aspect, in the spherical sintered body, the shape of the sphere becomes close to a true sphere, so that the polishing allowance can be made small, and the time and accuracy of the polishing process are significantly reduced. it can. In addition, mixing of impurities can be suppressed. Furthermore, since internal defects in the molded body can be reduced and microdefects in the sintered body can be reduced, the crushing load of the sintered body becomes large, and the reliability is improved.

  (2) In the second aspect of the present disclosure, the slurry is dropped into a container containing the second liquid to form the intermediate, and the intermediate sinks in the second liquid, The intermediate may be solidified by the gelling agent.

In the second aspect, by dropping the slurry in a container containing the second liquid, the intermediate can be solidified by the gelling agent when the intermediate sinks.
Therefore, the molded body can be easily and continuously manufactured.

(3) In the third aspect of the present disclosure, the temperature of the second liquid in the container may be set so that the temperature is lower in the lower part than in the upper part.
In the third aspect, gelation can be further promoted in the lower part of the second liquid by setting the temperature of the second liquid in the container so that the lower part is lower than the upper part. Therefore, the intermediate can be solidified quickly.

  Incidentally, by increasing the temperature of the upper part of the second liquid, it is possible to control the time until it stabilizes into a sphere immediately after dropping the slurry, and by forming a spherical body close to a true sphere, gelation proceeds, It is possible to obtain a molded body having a shape closer to a true sphere.

In this case, as the gelling agent, a material is used in which the gelation is promoted as the temperature is lower.
(4) In the fourth aspect of the present disclosure, degassing treatment of the slurry may be performed in the step of producing the slurry.

In the fourth aspect, bubbles in the slurry can be reduced by degassing the slurry. Therefore, the air bubbles in the intermediate, the formed body, and the sintered body, which are formed later, can be reduced.
(5) In the fifth aspect of the present disclosure, the first liquid may be water, and the second liquid may be a hydrophobic liquid.

In the fifth aspect, since such first and second liquids are used, an intermediate can be easily formed.
(6) In the sixth aspect of the present disclosure, when drying the formed body, the formed body may be dried while being rotated in a gas.

According to the sixth aspect, the formed body can be easily dried.
(7) In the seventh aspect of the present disclosure, the sintered body may be a ceramic or a sintered alloy.
The seventh aspect exemplifies the material of the sintered body.

(8) In the eighth aspect of the present disclosure, the sintered body may be a bearing.
The eighth aspect exemplifies a sintered body. In addition, as sphericity of a bearing, 0.05-1.2 mm of unequal diameter is mentioned. Moreover, as a dimension of a bearing, the thing of (phi) 1-25.4 mm is mentioned.

(9) In the ninth aspect of the present disclosure, the gelling agent may be agarose, gelatin, pectin, cellulose, or a surfactant.
The ninth aspect exemplifies a preferable gelling agent.

  (10) In the tenth aspect of the present disclosure, when the slurry is introduced into the second liquid, an air pulse dispenser, a plunger dispenser, a digital pipette, or a syringe may be used.

The tenth aspect exemplifies a preferable apparatus in the case of charging the slurry into the second liquid.
Hereinafter, each structure of the present invention will be described.
Examples of the ceramic constituting the sintered body include alumina, silicon nitride, sialon, and BIDEMICS (registered trademark) made by Japan Specialty Ceramics.

  As a sintered alloy which comprises a sintered compact, a cemented carbide alloy and a cermet are mentioned. As a sintered alloy constituting the sintered body, for example, a cemented carbide obtained by sintering 10 wt% cobalt to 90 wt% tungsten carbide, 60 wt% tungsten carbonitride, 20 wt% carbonized Tungsten, 5% by weight of niobium carbide, and 7.5% by weight each of nickel and cobalt are added and sintered.

  “To solidify the intermediate with a gelling agent to produce a molded body” is not a state in which only a thin film is formed on the surface of the intermediate, but the entire intermediate is solidified with a gel-like substance to form a molded body It is to be. That is, by gelling the liquid substance (the first liquid and the gelling agent, etc.) in the intermediate, specifically, by gelling the liquid substance of the entire intermediate (internal and surface), the intermediate The whole body is to be solidified with a gel-like substance to form a molded body.

(A) is explanatory drawing which shows the state of a slurry typically, (b) is explanatory drawing which shows an intermediate typically, (c) is explanatory drawing which shows a dried body typically. It is explanatory drawing which shows the dripping apparatus etc. which are used when producing the molded object of 1st Embodiment. It is explanatory drawing which shows the drying method of the molded object of 1st Embodiment. It is a photograph which shows the molded object before drying of 1st Embodiment, and the molded object after drying. It is explanatory drawing which shows the measuring method of the diameter non-uniformity of a ceramic ball. It is explanatory drawing which shows the dripping apparatus etc. which are used when producing the molded object of 2nd Embodiment. It is explanatory drawing which shows the dripping apparatus etc. which are used when producing the molded object of 3rd Embodiment.

Next, an embodiment of a method for producing a sintered body of the present disclosure will be described.
[1. First embodiment]
[1-1. Manufacturing method of ceramic ball]
The first embodiment describes a method of manufacturing a sintered body for manufacturing a spherical sintered body using a ceramic. In detail, the manufacturing method which manufactures the ceramic ball which is a ceramic sintered compact which can be used for a bearing etc. is demonstrated.

  In addition, as sphericity of the ceramic ball used for a bearing etc., 0.05-1.2 mm of diameter unequalness is mentioned. Moreover, as a dimension of a bearing, the thing of (phi) 1-25.4 mm is mentioned.

<Materials and equipment used for dripping>
First, materials and devices necessary for producing a molded body used for producing a ceramic ball will be described.

  Commercially available alumina (powder) and zirconium oxide (powder) were prepared as ceramic raw materials. Moreover, magnesium hydroxide (powder), calcium hydroxide (powder) and chromium oxide (powder) were prepared as sintering aids. Furthermore, scroll etc. were prepared as a dispersing agent.

  Then, for example, 68 g of alumina and 7 g of zirconium oxide were added to a pot containing resin beads, and 0.35 g of magnesium hydroxide, 0.2 g of calcium hydroxide and 1 g of a scroll of a dispersant were added. Furthermore, 75 g of water was poured into the pot.

Next, the pot was rotated to mix the raw materials in the pot for 10 hours to form a slurry, and 0.4 g of chromium oxide was added.
Next, the pot was placed on a hot plate, and while heating the slurry in the pot to, for example, 78 ° C. by the hot plate, a predetermined amount (eg, 2.5 g) of a gelling agent (eg, agarose) was added. The heating temperature is the temperature at which the gelling agent melts.

Furthermore, the slurry was mixed in a pot, and it was confirmed that the gelling agent was sufficiently dissolved.
Next, degassing of the slurry was performed while maintaining the temperature at 78 ° C. at which the gelling agent melted. As is well known, this degassing treatment is a treatment for degassing the slurry in the pot, for example, by applying a centrifugal force to the pot.

The state of the slurry is schematically shown in FIG. 1 (a), but the slurry is obtained by mixing the above-mentioned respective powders (inorganic powders) in a liquid consisting of water, a gelling agent and a dispersing agent, and the slurry The density of, for example, exceeds 1.0 g / cm ³ .

  Next, as shown in FIG. 2, the slurry was filled into the air pulse type dispenser 1 while maintaining the temperature at which the gelling agent was melted. That is, the dispenser 1 was heated by the heater 3 to maintain the temperature.

Separately from this, a dropping device 5 shown in FIG. 2 was prepared.
The dripping device 5 is obtained by filling a high viscosity silicone oil (KF96 manufactured by Shin-Etsu Chemical Co., Ltd.) in a cylinder 9 having a length of 1 m or more (for example, 1 m) in which the bottom 7 is closed and the top is open. The silicone oil was filled from the bottom 7 to 80 cm below the upper open end 11. The density of this silicone oil is, for example, less than 1.0 g / cm ³ .

  A band heater 13 is disposed around the upper portion of the dripping device 5, and the silicone oil is separated from the portion surrounded by the band heater 13 (i.e., the liquid upper portion H including the liquid surface) by the band heater 13. The temperature is set to a temperature (for example, 80 ° C.) at which the agent melts.

  On the other hand, the silicone oil in the lower part of the dripping device 5, that is, in the vicinity of the bottom 7 (that is, the lower part L including the portion in contact with the bottom 7) is below the temperature at which the gelling agent gels (eg 25 at room temperature) ° C) is set.

That is, the silicone oil in the cylinder 9 is set to have a temperature gradient such that the temperature of the lower part gradually decreases from the upper part.
<Method of dripping>
Next, the method of dripping the said slurry and producing an intermediate body and a molded object is demonstrated.

As shown in FIG. 2, from the tip of the dispenser 1, the slurry of the required weight (ie, the required volume) was dropped discretely and sequentially onto the silicone oil.
In addition, the volume of the slurry dripped at one time is set according to the magnitude | size of the intermediate body (therefore, subsequent molded object and ceramic ball).

For example, in the case of producing an intermediate or the like having a diameter of about 6 mm, for example, a slurry (for example, 113 mm ³ ) in an amount corresponding to the volume is dropped at one time.
The slurry dropped onto the upper surface of the silicone oil does not gel because the temperature of the silicone oil is high, and due to its own surface tension, it becomes a spherical intermediate 15 as schematically shown in FIG. The

After that, Intermediate 15 dropped gradually by its own weight.
At this time, since the temperature of the silicone oil in the cylinder 9 is lower toward the lower portion, the temperature of the slurry (specifically, the liquid portion thereof) constituting the intermediate 15 also gradually decreases. When the temperature of gelation was reached, the slurry (specifically, the liquid portion thereof) was gelated, whereby the intermediate 15 solidified and became a compact 17.

  Specifically, as intermediate 15 descends (and hence temperature decreases), solidification (ie curing) starts from the surface of intermediate 15, and when it reaches bottom 7, even the inside of intermediate 15 is completely The mixture solidified into a spherical shaped body 17.

In addition, since the formed body 17 is solidified to the inside, it does not collapse or break even when overlapped, and the shape of the formed body 17 is maintained even if the formed body 17 is overlapped.
Next, silicone oil is removed from the surface of the molded body 17 with absorbent fibers or a solvent, and then dried by natural drying, warm air or the like to obtain a dried dry body 19 (see FIG. 1 (c)). The

  Specifically, the formed body 17 was dried using, for example, a drying device 21 shown in FIG. The drying device 21 has a plurality of inclined rollers 23 arranged in parallel with a gap smaller than the diameter of the molded body 17.

  When drying the formed body 17 using the drying device 21, the formed body 17 is supplied to the upper portion of the rotating roller 23 (specifically, between the pair of rollers 23), and the formed body 17 is rotated by the rotation of the roller 23. At the same time, the molded body 17 is blown with warm air and dried. In addition, as a method of drying, a method of rolling on a rotating table can also be adopted.

  Here, FIG. 4 shows an example of the molded body 17 before drying (but in a state of being covered with silicone oil) and the dried body 19 after drying for 20 hours at room temperature. In the case of φ5.83 mm, the dried body 19 shrank 16.3% to φ4.88 mm.

Next, the dried dry body 19 was subjected to a degreasing treatment at a temperature of 600 ° C. in an air environment.
Next, the dried body 19 after degreasing was fired at 1500 ° C. for 2 hours in an air firing furnace to obtain a ceramic ball 25 (see FIG. 5) which is a spherical sintered body.

In addition, it is preferable to perform HIP processing in argon atmosphere of 1000 atm after that. Thereby, the generation of pores can be effectively suppressed.
Further, the sphericity of the ceramic ball 25 can be enhanced by polishing the surface of the ceramic ball 25 by, for example, a known diamond grindstone in the same manner as in the conventional method.

[1-2. effect]
(1) In the first embodiment, a slurry prepared by mixing the above-described raw material powder, the first liquid (i.e., the dispersion liquid), and the gelling agent is charged into the second liquid (i.e., the molding liquid). As a result, an intermediate 15 is formed, and the intermediate 15 is solidified by a gelling agent to produce a molded body 17.

Therefore, by drying and baking the molded body 17, it is possible to easily manufacture the ceramic ball 25 which is a spherical sintered body having high sphericity and few impurities.
Specifically, in the first embodiment, since the slurry is dropped into the second liquid and gelation is sufficiently performed to the inside of the intermediate 15 to produce the compact 17, the conventional uniaxial press molding method is used. There is no annular band like the one made. Therefore, sphericity is high. Moreover, since the process for removing the band is unnecessary, the manufacturing process can be simplified, and the labor and cost can be reduced.

  Further, even when producing a large ceramic ball 25 having a diameter of more than 3 mm, for example, rolling granulation for a long time such as rolling granulation method is not necessary, and the ceramic ball 25 can be easily manufactured in a short time. Can. And since rolling granulation is not performed, there is little fear of mixing of an impurity.

Furthermore, as in the case of the spray granulation method, there is little risk of contamination.
Moreover, when producing a molded object using the granules by the spray granulation method, the interstices (triple points) between the granules may remain as pores in the sintered body, and the strength of the sintered body may decrease. . However, in the first embodiment, since such a triple point does not exist, there is an advantage that the strength of the ceramic ball 25 is high, and the secondary firing step (HIP step etc.) which is a step of removing internal pores is omitted. It also has the merit of being able to

  As described above, in the first embodiment, the spherical shape of the ceramic ball 25 is close to a true sphere, so that the polishing allowance can be reduced, and the time and accuracy of the polishing process can be significantly reduced. In addition, mixing of impurities can be suppressed. Furthermore, since internal defects in the molded body 17 can be reduced and micro defects in the ceramic balls 25 can be reduced, the crushing load is increased, and the reliability is improved.

  (2) In the first embodiment, the slurry is dropped to the cylinder 9 containing the second liquid to form the intermediate 15, and the gelling agent is used when the intermediate 15 settles in the second liquid. Thus, the intermediate 15 can be solidified to produce a molded body 17. Therefore, the molded body 17 can be easily and continuously manufactured.

  (3) In the first embodiment, the gelation of the lower part is further promoted by setting the temperature of the second liquid in the cylinder 9 so that the temperature is lower in the lower part than in the upper part. it can. Therefore, intermediate 15 can be solidified quickly. Moreover, the deformation of the intermediate 15 can be suppressed, and the sphericity of the intermediate 15 or the like can be enhanced.

  (4) In the first embodiment, bubbles in the slurry can be reduced by degassing the slurry. Therefore, the air bubbles in the intermediate body 15, the formed body 17, and the ceramic ball 25 formed later can be reduced.

(5) In the first embodiment, since water is used as the first liquid and silicone oil which is a hydrophobic liquid is used as the second liquid, the intermediate 15 can be easily formed.
(6) In the first embodiment, when the formed body 17 is dried, the formed body 17 is dried while being rotated in a gas, so that the formed body 17 can be easily dried.

  As described above in detail, although the ceramic balls 25 are conventionally expensive due to the difficulty of the polishing process, in the first embodiment, the ceramic balls 25 having a shape close to a true sphere without bands are manufactured. As it can be done, the manufacturing cost can be significantly reduced.

  In addition, when manufacturing ceramic balls 25 of various sizes, it is possible to cope with the adjustment of the flow rate of the slurry and the control of the nozzle which is the tip of the dispenser 1. Furthermore, as compared with the conventional uniaxial press forming method, it is not necessary to prepare various molds, and since it is not necessary to set up replacement, the manufacturing process can be greatly simplified and the manufacturing cost can be significantly reduced. Is possible.

Thereby, the ceramic ball 25 can be developed on the market at low cost.
Also, the quality of the bearing application is important, and in the case of the ceramic ball 25, there is a high possibility of fatal defect, but according to the first embodiment, the pores in the ceramic ball 25 can be reduced, which is high. It is possible to obtain a ceramic ball 25 with load resistance and high reliability.

[1-3. Correspondence of wording]
Here, the correspondence relationship of words is demonstrated.
The dispenser 1, the cylinder 9, the intermediate 15, the formed body 17, the dried body 19, and the ceramic ball 25 of the first embodiment are respectively the dispenser, the container, the intermediate, the formed body, the dried body, and the sintering of the present disclosure. It corresponds to an example of the body.

[2. Second embodiment]
Next, a second embodiment will be described, but the description of the same content as that of the first embodiment will be omitted or simplified. The same components as those in the first embodiment are denoted by the same reference numerals.

In the second embodiment, since the manufacturing apparatus and the like are different from the first embodiment, the description will be made based on FIG.
As shown in FIG. 6, in the second embodiment, the slurry is filled from the first container 31 into the dispenser 1.

Next, the slurry is dropped from the dispenser 1 into the silicone oil in the cylinder 9 of the dropping device 5. The slurry is gelled from the intermediate 15 in the cylinder 9 to form a compact 17.
The bottom of this cylinder 9 is connected with the inclined pipe 33 so that the tip end is lowered, so the silicone oil moves in the pipe 33 and the formed body 17 moves in the tip while rolling in the pipe 33 .

  Further, a minute opening (not shown) through which only silicone oil passes is provided below the central portion of the pipe 33, and a branch pipe 35 is connected to the minute opening. The lower end of the branch pipe 35 is opened to the second container 37, so the silicone oil flowing through the pipe 33 is supplied to the second container 37 through the branch pipe 35.

  The micro opening is provided on the entire surface of the pipe 33 downstream of the connecting portion of the branch pipe 35, and the remaining silicone oil falling from the micro opening is configured to fall into the second container 37. ing.

  On the other hand, in the inside of the pipe 33, the molded body 17 which has moved to the tip end side from the connection portion of the branch pipe 35 is dried by air blowing to become a dried body 19 and discharged from the tip end side of the pipe 33 into the third container 39. Ru.

  In addition, the silicone oil collected in the second container 37 is heated to a temperature (for example, 80 to 90 ° C.) less than 100 ° C., and is sent to the fourth container 43 through the filter 41. Then, the silicone oil is automatically supplied from the fourth container 43 into the cylinder 9 by a pump or the like and reused.

  In the second embodiment, the same effects as in the first embodiment can be obtained. Moreover, in the second embodiment, since the dried body 19 can be continuously produced, there is an advantage that the working efficiency is high. Furthermore, there is an advantage that reuse of silicone oil can be easily performed.

[3. Third embodiment]
Next, a third embodiment will be described, but the description of the same content as that of the first embodiment will be omitted or simplified. The same components as those in the first embodiment are denoted by the same reference numerals.

In the third embodiment, since the manufacturing apparatus and the like are different from the first embodiment, the description will be made based on FIG. 7 focusing on the different points.
As shown in FIG. 7, in the third embodiment, the molded body 17 taken out of the cylinder 9 of the dropping device 5 as in the first embodiment, more specifically, the molded body 17 in a state where silicone oil is adhered to the surface, It is moved over a slightly inclined punching metal 53 in which a large number of minute openings (i.e., openings smaller in diameter than the compact 17) are opened.

At this time, air is blown to perform initial drying of the formed body 17. The container 55 is disposed below the minute opening 51, and the silicone oil dropped from the minute opening 51 is collected.
Next, the compact 17 after the initial drying is supplied to a cylindrical member 57 extending in the vertical direction to perform further drying. Specifically, in the cylindrical member 57, a pipe 59 extending spirally in the vertical direction is disposed, and in the pipe 59, a minute opening 61 similar to the above is formed. Then, air is blown from the lower side of the cylindrical member 57 upward.

Therefore, the dried compact 19 obtained in the upper part of the pipe 59 is sufficiently dried when it rolls down in the pipe 59 and moves downward.
In the third embodiment, the same effects as in the first embodiment can be obtained. In addition, there is an advantage that drying of the formed body 17 can be performed easily and sufficiently.

[4. Experimental example]
Next, an experimental example performed to confirm the effect will be described.
Experimental Example 1
In this experimental example 1, ceramic balls are produced by the production methods of Examples 1 and 2 in the range of the present disclosure, and ceramic balls are produced by the production method of Comparative Examples 1 to 5 outside the scope of the present disclosure. I examined the difference in the effect. In each of the following experimental examples, the ceramic balls after firing were polished using a diamond grindstone as described above.

  In this experimental example 1, the target dimension of the molded body to be produced was φ8.4 mm, and the target dimension of the ceramic ball after polishing was φ6.35 mm. In addition, the drip amount (necessary volume) of the slurry was adjusted according to the target dimension of the molded object to produce.

a) Example 1
In Example 1, ceramic balls were produced by the same production method as in the first embodiment (that is, a method of forming a compact by gelling the slurry in the second liquid: in-liquid method). In Example 1, the sintered body was polished to a target size, the polishing time was determined as follows, and the presence or absence of polishing scratches was examined. Further, the relative density was as follows: The diameter, diameter and crushing load were examined. The results are shown in Table 1 below.

Polishing time: Relative value to the polishing time (100) of the sintered body in the case of a uniaxial press compact Polishing flaw: Visually determine presence or absence Relative density: Determined by measuring weight in water by Archimedes method.

Unequal diameter: The difference between the vertical (a) and horizontal (b) dimensions of the ceramic ball indicating the degree of true sphere
(Ie, as shown in FIG. 5, in the projection of the ceramic ball
"(Maximum) major diameter-(perpendicular to major diameter)"
Crushing load: Relative value to crushing load (100) of sintered body in uniaxial press forming method
(Crushing load is the load at which a sintered body is broken when a load is applied to the sintered body)
b) Example 2
Example 2 uses silicon nitride as the ceramic material of Example 1. Specifically, an inorganic powder containing silicon nitride as the main component (97% by weight) was used as the inorganic material of the slurry. The components of the slurry such as other inorganic components are the same as in Example 1.

  In the case of the silicon nitride-based material of this Example 2, the process up to the forming process of the dry body is the same as that of the first embodiment, but at the time of baking, at 1750 ° C. under a nitrogen atmosphere using a controlled atmosphere furnace. Baking was performed for 2 hours. In addition, this baking condition is the same also about the nitrogen silicon system of each following experimental example.

Then, with respect to this example 2 as well, in the same manner as the example 1, the polishing time, the polishing flaw, the relative density, the diameter unevenness, and the crushing load were examined. The results are shown in Table 1 below.
c) Comparative Example 1
In Comparative Example 1, a molded body is produced using a silicon nitride-based inorganic powder using a known uniaxial press molding method, and the molded body is fired to produce a ceramic ball.

Then, also in this Comparative Example 1, in the same manner as in Example 1, the polishing time, the polishing flaw, the relative density, the diameter unevenness, and the crushing load were examined. The results are shown in Table 1 below.
d) Comparative example 2
The comparative example 2 produces a molded object using the well-known uniaxial press molding method using the inorganic powder of an alumina type, bakes the molded object, and manufactures a ceramic ball.

Then, also in this Comparative Example 2, in the same manner as in Example 1, the polishing time, the polishing flaw, the relative density, the difference in diameter, and the crushing load were examined. The results are shown in Table 1 below.
e) Comparative example 3
The comparative example 3 produces a molded object using the well-known rolling granulation method using the silicon nitride type inorganic powder, and bakes the molded object, and manufactures a ceramic ball.

Then, also in this Comparative Example 3, in the same manner as in Example 1, the polishing time, the polishing flaw, the relative density, the difference in diameter, and the crushing load were examined. The results are shown in Table 1 below.
f) Comparative example 4
The comparative example 4 produces a molded object using the following alginic acid method using the inorganic powder of a silicon nitride type, dries after baking, and bakes the molded object, and manufactures a ceramic ball.

  Here, in the alginic acid method, a slurry containing inorganic powder, agarose and sodium alginate is dropped into a two-layer solution in which the upper layer is liquid paraffin and the lower layer is calcium chloride aqueous solution, and the upper layer is a slurry that has become spherical. This is a method of forming a film around the periphery and coagulating a spherical slurry in the lower layer to produce a compact.

Then, the relative density and the like of the comparative example 4 were examined in the same manner as the example 1. The results are shown in Table 1 below.
g) Comparative example 5
The comparative example 5 produces a molded object using the said alginic acid method using the inorganic powder of an alumina type, is baking after drying the molded object, and manufactures a ceramic ball.

  Then, the relative density and the like of the comparative example 5 were examined in the same manner as the example 1. The results are shown in Table 1 below.

In addition, ◎ ○ × in the column of cost in Table 1 indicates the order of 、, 、, and × from the lower cost side.

  As apparent from Table 1, Examples 1 and 2 are preferable because they do not require a banding step, have a short polishing time, and have no polishing scratches. That is, it is suitable because the process for processing the ceramic ball is not time-consuming.

Moreover, since the diameter inequalities are small in the first and second embodiments, the sphericity is preferably high. Furthermore, the relative density is high and the crushing load is high, so that the strength is excellent.
On the other hand, Comparative Examples 1 and 2 are not preferable because they require a banding step, have a long polishing time, and have polishing scratches. Moreover, compared with Example 1, 2, since crushing load is low, it is inferior in intensity | strength.

Moreover, since the difference in diameter is large and the crushing load is small, Comparative Example 3 is not preferable.
Furthermore, in Comparative Examples 4 and 5, the deformation of the molded body (therefore, the ceramic ball) was large, and the diameter inequality could not be measured.

As is clear from this experimental example 1, it is understood that in Examples 1 and 2 of the present disclosure, ceramic balls having high sphericity and high strength can be easily manufactured.
<Experimental Example 2>
In Experimental Example 2, as shown in Table 2 below, ceramic balls were manufactured by the manufacturing method of Examples 3 to 15 within the scope of the present disclosure, and the effects thereby were examined.

  The present experimental example 2 is the same as the first embodiment except for the conditions described in Table 2 below. Here, the composition and production method of the alumina-based inorganic powder are the same as in the first embodiment, and the composition and production method of the silicon nitride-based inorganic powder are the same as those of the second embodiment.

  The upper temperature in Table 2 is an average temperature in the range of 1 cm from the surface of the second liquid, and the lower temperature is an average temperature in the range of 1 cm from the lower surface of the second liquid. The normal temperature is 25 ° C.

  In addition, the quantity of the slurry dripped was suitably adjusted according to the volume of the target molded object.

As is clear from this Table 2, in Examples 3 to 15 of the present disclosure, even if the size of the molded body is a large one exceeding φ 20 mm, it is preferable that there is no difference in diameter (that is, the sphericity is high). . In the case where the upper temperature is 25 ° C., the difference in diameter is substantially zero, but the sphericity is slightly lower than in the other examples.

<Experimental Example 3>
In this experimental example 3, the ceramic balls of Examples 16 to 20 of the range of the present disclosure were manufactured by the drying method of Table 3 below, and the difference in the effects due to the production was examined.

  In Example 16, the alumina-based inorganic powder similar to that of the first embodiment was used, and the formed body was dried by a roller drying method to manufacture a ceramic ball. Then, the polishing time, the presence or absence of polishing scratches, the relative density, and the diameter unevenness of the molded product were examined. The results are shown in Table 3 below.

  In Example 17, while using the alumina type inorganic powder similar to the said 1st Embodiment, the molded object was dried by the in-liquid rolling system, and the ceramic ball was manufactured. Then, the polishing time, the presence or absence of polishing scratches, the relative density, and the diameter unevenness of the molded product were examined. The results are shown in Table 3 below.

  Here, the drying by the in-liquid rolling method refers to forming the slurry spheres while rotating (that is, rotating) the slurry spheres by applying rotational force to the slurry in the liquid, and then drying the formed spheres. .

  In Example 18, the same silicon nitride-based inorganic powder as in Example 2 was used, and the formed body was dried by a roller drying method to produce a ceramic ball. Then, the polishing time, the presence or absence of polishing scratches, the relative density, and the diameter unevenness of the molded product were examined. The results are shown in Table 3 below.

  In Example 19, the alumina-based inorganic powder similar to that of the first embodiment was used, and the formed body was placed on an oil sheet for absorbing oil and naturally dried to manufacture a ceramic ball. Then, the polishing time, the presence or absence of polishing scratches, the relative density, and the diameter unevenness of the molded product were examined. The results are shown in Table 3 below.

  In Example 20, a silicon nitride-based inorganic powder similar to that of Example 2 was used, and the formed body was placed on an oil sheet for absorbing oil and naturally dried to manufacture a ceramic ball. Then, the polishing time, the presence or absence of polishing scratches, the relative density, and the diameter unevenness of the molded product were examined. The results are shown in Table 3 below.

In addition, ◎ of the polishing time in Table 3 indicates that the polishing time is shorter than に.

As apparent from this Table 3, the polishing time of the sintered body is shorter as compared with the one dried by the drying method of Examples 19 and 20, and the one dried by the drying method of Examples 16 to 18 is preferable. The
Moreover, the diameter non-uniformity of the molded object of Examples 16-18 was smaller than the diameter non-uniformity of the molded object of Example 19, 20, and the point of sphericity was suitable.

<Experimental Example 4>
In Experimental Example 4, the generation state of color unevenness due to the mixing of impurities was examined.
When a plurality of (for example, 500) ceramic balls made of silicon nitride were manufactured by the manufacturing method using the in-liquid method of Example 2, the occurrence rate of color unevenness due to impurities in the ceramic balls was 0.50%. It was very small.

  On the other hand, when a plurality of (for example, 10000) ceramic balls of silicon nitride type are manufactured by the manufacturing method using the uniaxial press molding method of the comparative example 1, the generation rate of color unevenness due to impurities in the ceramic balls is 3%. There were many.

  Furthermore, when a plurality of (for example, 10000) ceramic balls of silicon nitride type are manufactured by a manufacturing method using a high speed pressing method in which a large number of molded bodies are simultaneously manufactured with multiple pins, occurrence of color unevenness due to impurities in the ceramic balls The rate was even higher at 10%.

As apparent from this experimental example 4, it can be seen that the production of the ceramic ball according to the production method of the present disclosure can suppress the mixing of impurities into the ceramic ball.
[5. Other Embodiments]
As mentioned above, although embodiment of this indication was described, this indication is not limited to the above-mentioned embodiment, It is possible in the range which does not deviate from the gist of this indication to carry out in various modes.

(1) For example, as the first liquid, alcohol or the like can be adopted other than water.
(2) The second liquid may be any one that does not mix with the first liquid of the slurry, and silicone oil, vegetable oil, decalin, etc. can be adopted.

  (3) As the gelling agent, gelatin, pectin, cellulose, surfactant or the like can be adopted in addition to agarose. For example, starch, PVA (polyvinyl alcohol), curdlan, k-carrageenan, l-carrageenan, gellan gum and the like can be employed.

  (4) As a device for introducing the slurry into the second liquid, a plunger type dispenser, a digital pipette, a syringe or the like can be adopted other than the air pulse type dispenser. (5) As a sintered alloy which comprises a sintered compact, the cemented carbide of the composition mentioned above, cermet, for example are mentioned. For example, a raw material powder of this cemented carbide or cermet sintered alloy can be used to make a slurry, and this slurry can be used to form a spherical intermediate and to form a dry body through a formed body. And a sintered compact is obtained by baking this dried body, for example similarly to the former.

  (6) Note that the function possessed by one component in each of the above embodiments may be shared by a plurality of components, or the function possessed by a plurality of components may be exhibited by one component. In addition, part of the configuration of each of the above embodiments may be omitted. In addition, at least a part of the configuration of each of the above-described embodiments may be added to or replaced with the configuration of the other embodiments. In addition, all the aspects contained in the technical thought specified from the wording as described in a claim are an embodiment of this indication.

DESCRIPTION OF SYMBOLS 1 ... Dispenser 9 ... Tube 15 ... Intermediate body 17 ... Molded body 19 ... Dry body 25 ... Ceramic ball

Claims (10)

A method for producing a sintered body, wherein a spherical body is produced using a raw material powder of ceramic or sintered alloy, and the body is fired to produce a spherical sintered body,
Preparing a slurry by mixing a raw material powder of the ceramic or the sintered alloy, a first liquid which is a dispersion medium of the raw material powder, and a gelling agent of the first liquid;
The slurry is charged into a second liquid which is not soluble in the first liquid in the slurry, and a spherical intermediate is formed by the surface tension of the slurry, and the intermediate is solidified by the gelling agent. Producing a molded body,
Drying the formed body to produce a dried body;
Firing the dried body;
The manufacturing method of the sintered compact which has. The slurry is dropped into a container containing the second liquid to form the intermediate, and the intermediate is solidified by the gelling agent when the intermediate sinks in the second liquid. ,
The manufacturing method of the sintered compact of Claim 1. The temperature of the second liquid in the container is set such that the temperature is lower in the lower part than in the upper part,
The manufacturing method of the sintered compact of Claim 2. In the step of preparing the slurry, the slurry is subjected to degassing treatment,
The manufacturing method of the sintered compact of any one of Claims 1-3. The first liquid is water, and the second liquid is a hydrophobic liquid,
The manufacturing method of the sintered compact of any one of Claims 1-4. When drying the formed body, the formed body is dried while being rotated in a gas.
The manufacturing method of the sintered compact of any one of Claims 1-5. The sintered body is a ceramic or a sintered alloy
The manufacturing method of the sintered compact of any one of Claims 1-6. The sintered body is a bearing,
The manufacturing method of the sintered compact of any one of Claims 1-7. The gelling agent is agarose, gelatin, pectin, cellulose or a surfactant.
The manufacturing method of the sintered compact of any one of Claims 1-8. When the slurry is introduced into the second liquid, an air pulse dispenser, a plunger dispenser, a digital pipette, or a syringe is used.
The manufacturing method of the sintered compact of any one of Claims 1-9.