Method for conveying molded body and method for producing sintered body
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-05
- Publication Date
- 2026-08-13
Smart Images
Figure JP2026004216_13082026_PF_FP_ABST
Abstract
Description
Method for transporting a formed body and method for manufacturing a sintered body
[0001] The embodiments described below generally relate to a method for transporting a formed body and a method for manufacturing a sintered body.
[0002] Ceramic sintered bodies are used in wear-resistant members, substrates for semiconductor devices, and the like. Examples of wear-resistant members include bearing balls, rollers, rollers, engine parts, and the like. Ceramic sintered bodies are composed of silicon nitride sintered bodies, aluminum nitride sintered bodies, aluminum oxide sintered bodies, zirconium oxide sintered bodies, and the like. For example, Japanese Patent No. 7402177 (Patent Document 1) discloses a wear-resistant member made of a silicon nitride sintered body. The silicon nitride sintered body of Patent Document 1 has excellent mechanical strength and wear resistance.
[0003] Ceramic sintered bodies such as materials for ceramic balls are manufactured by a raw material mixing process, a forming process, a debinding process, a sintering process, and the like. For example, Japanese Patent No. 7584543 (Patent Document 2) discloses a material for ceramic balls as a ceramic sintered body. This material for ceramic balls has a belt-shaped portion on the outer periphery of the spherical surface portion. In Patent Document 2, the polishing efficiency is improved by devising the belt-shaped portion.
[0004] Ceramic sintered bodies such as materials for ceramic balls are manufactured by degreasing and sintering a ceramic formed body having a spherical surface portion among ceramic formed bodies. A ceramic formed body having a spherical surface portion is manufactured using a forming method such as die forming, CIP forming, or rolling granulation in the forming process. In addition, a ceramic formed body having a spherical surface portion may be manufactured by combining a plurality of forming methods.
[0005] Japanese Patent No. 7402177, Japanese Patent No. 7584543, International Publication No. 2025 / 057846
[0006] Ceramic molded bodies with spherical sections are transported both after being molded using a combination of molding methods and before degreasing, and after being degreased and before sintering. The ceramic molded bodies are made by compressing raw material powder. Because the ceramic molded bodies have low strength, they sometimes break during transport involving drops. They are also sometimes transported by rolling, but they sometimes break during this rolling process.
[0007] The embodiment addresses these issues and aims to suppress damage to molded bodies having curved surfaces on part or all of their surface during transport involving dropping.
[0008] The method for transporting a molded body according to this embodiment comprises a moving step, a dropping step, and a storage step. The moving step involves moving a holding container that holds a curved molded body, which is a molded body having a curved portion on part or all of its surface, to above the base material. The dropping step involves tilting the holding container after it has been moved in the moving step and dropping the curved molded body onto the base material. The storage step involves storing the curved molded body, which has rolled on the base material after being dropped onto it, into the storage container. A cushioning material with a rebound modulus of 40% or less is provided in at least the area of the slope of the base material that includes the point where the curved molded body falls.
[0009] A diagram showing a flowchart illustrating an example of a method for transporting a molded body according to the embodiment. A diagram illustrating an example of a dropping process in the method for transporting a molded body according to the embodiment. An external view showing a ceramic spherical molded body, which is a first example of a curved molded body transported by the method for transporting a molded body according to the embodiment. An external view showing a striped ceramic spherical molded body, which is a second example of a curved molded body transported by the method for transporting a molded body according to the embodiment. A diagram showing a flowchart illustrating an example of a method for manufacturing a sintered body according to the embodiment. An external view showing a spherical sintered body, which is a first example of a ceramic curved sintered body manufactured by the method for manufacturing a sintered body according to the embodiment. An external view showing a striped spherical sintered body, which is a second example of a ceramic curved sintered body manufactured by the method for manufacturing a sintered body according to the embodiment. Embodiment
[0010] The following describes in detail embodiments of the method for transporting molded bodies and the method for manufacturing sintered bodies, with reference to the drawings.
[0011] The method for transporting a molded body according to this embodiment comprises a moving step, a dropping step, and a storage step. The moving step involves moving a holding container that holds a curved molded body, which is a molded body having a curved portion on part or all of its surface, to above the base material. The dropping step involves tilting the holding container after it has been moved in the moving step and dropping the curved molded body onto the base material. The storage step involves storing the curved molded body, which has rolled on the base material after being dropped onto it, into the storage container. A cushioning material with a rebound modulus of 40% or less is provided in at least the area of the slope of the base material that includes the point where the curved molded body falls.
[0012] Examples of curved molded bodies transported by the transport method according to this embodiment include a ceramic curved molded body 1 made of ceramics, a metal curved molded body made of metal, and a resin curved molded body made of resin. These curved molded bodies are molded bodies that have been processed to have a curved surface. Furthermore, the curved molded body becomes a curved sintered body, which is a sintered body having a curved surface, by subjecting it to a sintering process or a thermosetting process. Hereinafter, the case in which the curved molded body is a ceramic curved molded body 1 will be described as an example. The ceramic curved molded body 1 includes at least the following four ceramic curved molded bodies. (1) A spherical ceramic curved surface molded body having only a spherical portion as the curved surface, i.e., a ceramic spherical molded body 11 (shown in Figures 2 and 3) (2) A ceramic curved surface molded body having a spherical portion and a band-shaped portion formed on the outer circumference of the spherical portion as the curved surface, i.e., a ceramic spherical molded body with a band 12 (shown in Figure 4) (3) An ellipsoidal ceramic curved surface molded body having only an ellipsoidal portion as the curved surface (4) A cylindrical ceramic curved surface molded body having a curved side surface and a circular base
[0013] In the following explanation, unless otherwise specified, the case in which the ceramic curved molded body 1 is a ceramic spherical molded body 11 will be used as an example.
[0014] The curved surface sintered body, which is a sintered body having a curved surface portion on part or all of its surface and manufactured by the manufacturing method of the sintered body according to the embodiment, will be described as a ceramic curved surface sintered body 7 made of ceramics. The ceramic curved surface sintered body 7 includes at least the following four ceramic curved surface sintered bodies: (5) A spherical ceramic curved surface sintered body having only a spherical portion as the curved surface portion, i.e., a ceramic spherical sintered body 71 (shown in Figure 6) (6) A ceramic curved surface sintered body having a spherical portion and a band-shaped portion formed on the outer circumference of the spherical portion as the curved surface portion, i.e., a ceramic spherical sintered body with a band 72 (shown in Figure 7) (7) An ellipsoidal ceramic curved surface sintered body having only an ellipsoidal portion as the curved surface portion (8) A cylindrical ceramic curved surface sintered body having a curved side surface and a circular bottom surface as the curved surface portion
[0015] The ceramic spherical sintered body 71 described in (5) above is manufactured from the ceramic spherical molded body 11 described in (1). The striped ceramic spherical sintered body 72 described in (6) above is manufactured from the striped ceramic spherical molded body 12 described in (2). The ceramic curved sintered bodies described in (7) and (8) above are each manufactured from the ceramic curved molded bodies described in (3) and (4) above.
[0016] Figure 1 shows a flowchart illustrating the method for transporting a molded body according to an embodiment. This method for transporting a molded body includes a moving step ST1, a dropping step ST2, and a receiving step ST3, and corresponds to step ST13 in the manufacturing method of a sintered body shown in Figure 5. Details of each step ST1 to ST3 will be described later.
[0017] Figure 2 shows the dropping process in the conveying method for a molded body according to the embodiment. Figure 2(A) is a side cross-sectional view, and Figure 2(B) is a top view. In the figures, reference numeral 1 denotes a ceramic curved molded body, reference numeral 2 denotes a holding container, reference numeral 3 denotes a cushioning material, reference numeral 4 denotes a base material, reference numeral 5 denotes a containment container, reference numeral 11 denotes a ceramic spherical molded body which is an example of a ceramic curved molded body 1, and reference numeral L denotes the vertical dropping distance. Figures 3 and 4 show examples of ceramic curved molded bodies 1, respectively. Reference numeral 12 denotes a stripped ceramic spherical molded body which is an example of a ceramic curved molded body 1, reference numeral 121 denotes the curved portion of the stripped ceramic spherical molded body 12, and reference numeral 122 denotes the stripped portion of the stripped ceramic spherical molded body 12.
[0018] The ceramic spherical molded bodies 11 and 12 are manufactured in a molding process ST12 (shown in Figure 5), described later, using molding methods such as die molding, CIP (Cold Isostatic Pressing) molding, and rolling granulation. Die molding is a method in which ceramic powder is filled into upper and lower molds and molded by applying pressure. With die molding, a striped ceramic spherical molded body 12 having a strip-shaped portion 122 can be produced to prevent the upper and lower molds from coming into direct contact. CIP molding (Cold Isostatic Press) is sometimes called cold isostatic pressing or CIP treatment. CIP molding is a molding method in which ceramic powder or a ceramic molded body is sealed in a recess of a rubber mold used in CIP molding (hereinafter referred to as "CIP rubber mold") and isotropic pressure is applied with a liquid. Rolling granulation is a molding method in which ceramic powder is attached to the surface of a core made of solidified ceramic powder while it is being rolled. Rolling granulation may also use metal or resin as the core.
[0019] In the molding process ST12, a CIP (Cleaning Injection Press) method is also effective for the ceramic spherical molded bodies 11 and 12 obtained by rolling granulation or die molding. Since CIP molding is isotropic, it can reduce the pores in the ceramic spherical molded bodies 11 and 12. By performing CIP molding, the strength of the ceramic spherical molded bodies 11 and 12 can be increased. Alternatively, the ceramic spherical molded bodies 11 and 12 may be obtained by demolition from long ceramic molded bodies obtained by extrusion molding, sheet molding, or injection molding.
[0020] The method for transporting the ceramic spherical molded bodies 11 and 12 includes a dropping step ST2 (shown in Figure 1) in which the ceramic spherical molded body 11 is dropped. The dropping step ST2 is a step in which the ceramic spherical molded body 11 is dropped from above to below. In Figure 2, the ceramic spherical molded body 11 is shown to be in free fall in the vertical direction, but it may also be horizontal projection (for example, launched horizontally) in which it falls in a parabolic trajectory. Furthermore, it is preferable that the dropping is carried out in accordance with gravity.
[0021] The ceramic spherical molded body 11 is placed in the holding container 2 before being dropped. The shape of the holding container 2 is not particularly limited, as long as it is capable of holding the ceramic spherical molded body 11 and has an opening in part for insertion and removal. Alternatively, the holding container 2 may be a belt conveyor, and the ceramic spherical molded body 11 may be moved by the belt conveyor and dropped from the downstream end of the belt conveyor.
[0022] The holding container 2 may be a CIP rubber mold. In that case, the moving step ST1 includes a rubber mold dismantling step in which the ceramic spherical molded body 11 is detached from the recess of the CIP rubber mold. After the rubber mold dismantling step, the CIP rubber mold that holds the ceramic spherical molded body 11 detached from the recess is moved as the holding container 2. The CIP rubber mold is preferably disc-shaped and has a plurality of recesses for housing the ceramic spherical molded body 11. Having a plurality of recesses in the CIP rubber mold allows multiple ceramic spherical molded bodies 11 to be CIP-treated in a single CIP molding process. The shape of the CIP rubber mold is not particularly limited, but examples include those described in International Publication No. 2025 / 057846 (Patent Document 3).
[0023] The base material 4 is provided above the containment container 5 and below the holding container 2. The inclined surface formed on the upper surface of the base material 4 is positioned and shaped to receive the ceramic spherical molded body 11 dropped from the holding container 2, and to allow the ceramic spherical molded body 11 to roll from the drop point LL of the inclined surface using its slope and fall through the drop hole B into the containment container 5. For example, the base material 4 has a hollow shape for the drop hole B, and its upper surface is inclined to slope downward toward the inner drop hole B. Note that the shapes of the drop hole B, cushioning material 3, and base material 4 when viewed from above are not limited to circles, but may be ellipses or rectangles (including squares).
[0024] The cushioning material 3 is provided in an area of the inclined surface of the base material 4 that includes at least the landing point LL of the ceramic spherical molded body 11. Figure 2 shows an example in which the cushioning material 3 is provided over the entire inclined surface of the base material 4. Preferably, the cushioning material 3 is also provided in the area where the ceramic spherical molded body 11 rolls down the inclined surface of the base material 4, that is, over the entire inclined surface downstream of the landing point LL of the ceramic spherical molded body 11, or, as shown in Figure 2, it may be provided over the entire inclined surface of the base material 4. By providing the cushioning material 3 over the entire inclined surface of the base material 4, it is not necessary to control the landing position of the ceramic spherical molded body 11, thus increasing the degree of freedom in transport. In other words, if the landing position is controlled in advance, the area over which the cushioning material 3 is provided can be reduced. The cushioning material 3 is fixed to the inclined surface of the base material 4 using adhesive, double-sided tape, etc., as necessary.
[0025] The cushioning material 3 has a rebound modulus of 40% or less. Rebound modulus is the ratio of how much a material bounces back when a force is applied to it. For example, when an object is dropped from a certain height, an object with a rebound modulus of 100% will bounce back to its original height. Therefore, the lower the rebound modulus, the lower the ratio of bounce.
[0026] By using a cushioning material 3 with a rebound modulus of 40% or less, damage to the ceramic spherical molded body 11 due to impact from dropping can be suppressed. For this reason, the rebound modulus of the cushioning material 3 is preferably 40% or less, and more preferably 15% or less. The lower limit of the rebound modulus is not particularly limited, but a rebound modulus of 1% or more is preferred. If the rebound modulus is too low, the cost of the material may increase. For this reason, the rebound modulus of the cushioning material 3 is preferably 40% or less, and more preferably within the range of 1% to 15%. The method for measuring the rebound modulus shall be in accordance with JIS K 6400-3. Note that JIS K 6400-3 corresponds to ISO 8307.
[0027] It is preferable that the hardness of the cushioning material 3 is 45 degrees or less. Hardness is a specification that indicates the hardness of the material. If the hardness of the cushioning material 3 exceeds 45 degrees, the cushioning material 3 becomes hard, and the possibility of the ceramic spherical molded body 11 being damaged when it collides with the cushioning material 3 during a fall increases. In particular, there is a possibility that the ceramic spherical molded body 11 may crack due to the impact when it collides with the cushioning material 3.
[0028] The lower limit of the hardness of the cushioning material 3 is not particularly limited, but 5 degrees or higher is preferred. If the hardness of the cushioning material 3 is less than 5 degrees, it may be too soft and difficult to maintain its shape. For this reason, the hardness of the cushioning material 3 is preferably 45 degrees or lower, and more preferably between 5 degrees and 30 degrees. Furthermore, a hardness of 5 degrees or higher and 20 degrees is even more preferred. The hardness should be measured in accordance with JIS K 6253-3.
[0029] Furthermore, hardness measurement shall be carried out in accordance with JIS K 6253-3, using one of the following types of testers: Type A durometer, Type D durometer, Type E durometer, or Type AM durometer. Note that JIS K 6253-3 corresponds to ISO 48-4.
[0030] The thickness of the cushioning material 3 is preferably 0.5 mm or more. If the cushioning material 3 is too thin, less than 0.5 mm, it may not be able to take advantage of its good rebound modulus. There is no particular upper limit to the thickness of the cushioning material 3, but it is preferably 10 mm or less. Even if the thickness exceeds 10 mm, it may not be possible to obtain any further effect.
[0031] Examples of materials for the cushioning material 3 include resin sheets such as rubber sheets, urethane sheets, and gel sheets. Furthermore, when using commercially available cushioning material 3, the rebound modulus and hardness may be based on catalog values.
[0032] The ceramic spherical molded body 11, upon impact with the cushioning material 3 due to the fall, rolls along the base material 4, i.e., the cushioning material 3, and falls into the storage container 5 for storage. By giving the upper surface of the base material 4 an inclination angle of 10 degrees or more and 40 degrees or less from the horizontal plane, the storage efficiency into the storage container 5 is increased. In particular, since the ceramic curved molded body 1 has a curved surface and the ceramic spherical molded bodies 11 and 12 have a spherical surface, it is easy for them to roll down the inclined surface of the base material 4 and be stored in the storage container 5. If the inclination angle of the inclined surface of the base material 4 exceeds 40 degrees, the momentum due to the inclination will be too great, causing the ceramic curved molded body 1 to fall too fast into the storage container 5, which may cause damage. If the inclination angle is less than 10 degrees, the ceramic curved molded body 1 will not roll much on the inclined surface of the base material 4, which may reduce storage efficiency.
[0033] In the dropping process of the ceramic spherical molded body 11, it is preferable that the vertical component distance (vertical drop distance) L when it falls from the holding container 2 onto the cushioning material 3 is 300 mm or less. The upper end LH of the vertical drop distance L is the lowest point (point or line) E of the opening edge of the holding container 2 when the holding container 2 is tilted in the dropping process ST2. The upper end LH of the vertical drop distance L is a position shifted horizontally from the lowest point E by half the maximum dimension of the ceramic curved molded body 1 (radius if the ceramic curved molded body 1 has a spherical portion) R (for example, the horizontal component in the direction from the lowest point E to the center of the drop hole B). The lower end LL of the vertical drop distance L is the intersection of the vertical line passing through the upper end LH and the cushioning material 3. By providing at least the cushioning material 3 in the area including the drop point LL, damage to the ceramic spherical molded body 11 during the dropping process can be suppressed. On the other hand, if the vertical drop distance L is greater than 300 mm, the damage to the ceramic spherical molded body 11 when it collides with the cushioning material 3 may increase. In particular, the larger the size of the ceramic spherical molded body 11, the greater the impact of the collision. Similarly, the impact of the collision is also greater in the case of the striped ceramic spherical molded body 12. For this reason, the vertical drop distance L is preferably 300 mm or less, and more preferably between 25 mm and 200 mm. It can be used even if the vertical drop distance L is less than 25 mm (including 0 mm), but it may not be possible to obtain any further effect.
[0034] The dropped ceramic spherical molded body 11 rolls over the cushioning material 3, falls from the cushioning material 3, and is contained within the containment container 5. If the vertical drop distance L is too small, the ceramic spherical molded body 11 will have difficulty rolling over the cushioning material 3, which may reduce its ability to be contained within the containment container 5. Also, if the vertical drop distance L is close to 0 mm, handling will be poor, reducing work efficiency, or the design difficulty for automation may become extremely high.
[0035] As described above, the rubber mold dismantling process using the CIP rubber mold is a process of separating the ceramic spherical molded body 11 from the recess of the CIP rubber mold. By tilting the CIP rubber mold as a holding container 2, the ceramic spherical molded body 11 after CIP treatment can be dropped from the CIP rubber mold onto the cushioning material 3. The dropping process may include a process of dropping the ceramic spherical molded body 11 in addition to the rubber mold dismantling process using the CIP rubber mold.
[0036] As previously described, the ceramic curved surface molded body 1 may be a striped ceramic spherical molded body 12 having a strip-shaped portion 122 on the outer circumference of a spherical portion 121, a cylindrical ceramic curved surface molded body, or an ellipsoidal ceramic curved surface molded body. As mentioned above, the striped ceramic spherical molded body 12 is mainly obtained by mold molding. The method for transporting the molded body according to this embodiment can similarly suppress damage whether the ceramic curved surface molded body 1 is a striped ceramic spherical molded body 12, a cylindrical ceramic curved surface molded body, or an ellipsoidal ceramic curved surface molded body.
[0037] The ceramic curved molded body 1 may have a maximum dimension of 7 mm or more. If the ceramic curved molded body 1 is a ceramic spherical molded body 11, the maximum dimension is the diameter. If the ceramic curved molded body 1 is a striped ceramic spherical molded body 12, the maximum dimension is the diameter of the spherical portion 121. If the ceramic curved molded body 1 has an elliptical shape, the maximum dimension is the diameter of the major axis. If the ceramic curved molded body 1 has a cylindrical shape, the maximum dimension is the diameter of the base circle (major axis in the case of an ellipse) or the height, whichever is larger.
[0038] As shown in Figure 5, the ceramic curved molded body 1 becomes a ceramic curved sintered body 7 by performing a degreasing process (if necessary) and a sintering process after the containment process ST3 shown in Figure 1. Figure 6 shows a ceramic spherical sintered body 71, which is a first example of a ceramic curved sintered body 7 manufactured by the manufacturing method of the sintered body according to the embodiment. Figure 7 shows a banded ceramic spherical sintered body 72, which is a second example of a ceramic curved sintered body 7, having a spherical portion 721 and a band-shaped portion 722 formed on the outer circumference of the spherical portion 721.
[0039] By polishing the ceramic curved surface sintered body 7 (for example, the striped ceramic spherical sintered body 72), it becomes a bearing ball. The bearing balls come in various sizes, with diameters ranging from 1 mm to 70 mm. As the diameter and maximum dimensions increase, the impact when the original ceramic curved surface molded body 1 is dropped increases. The transport process ST13 in the method for transporting the ceramic curved surface molded body 1 can suppress damage even if the maximum dimensions of the ceramic curved surface molded body 1 (diameter in the case of ceramic spherical molded bodies 11 and 12) are as large as 7 mm or more. In other words, it is effective for transporting ceramic curved surface molded bodies 1 with a maximum of 7 mm or more, and even more so for dimensions ranging from 9 mm to 70 mm.
[0040] The main component of the ceramic curved molded body 1 is one selected from silicon nitride, aluminum nitride, boron nitride, aluminum oxide, zirconium oxide, and silicon carbide. The main component is the component that is present in the largest mass ratio in the ceramic sintered body. For example, if silicon nitride is the largest component, it becomes a silicon nitride sintered body. If aluminum oxide is the largest component, it becomes an aluminum oxide sintered body. Furthermore, it is preferable to use a ceramic curved molded body 1 with silicon nitride as the main component. A silicon nitride sintered body as a ceramic curved sintered body 7 is more expensive than an aluminum oxide sintered body, etc. If a silicon nitride molded body is damaged, the cost loss is significant.
[0041] The method for transporting the molded body according to the embodiment can be used in the method for manufacturing a ceramic sintered body. As shown in FIG. 5, the ceramic curved surface molded body 1 accommodated in the storage container 5 in the transport step ST13 is sent to the degreasing step ST14 or the sintering step ST15 together with the storage container 5. The method for manufacturing a ceramic sintered body will be described with reference to FIG. 5.
[0042] First, the raw material mixing and molding step ST11 shown in FIG. 5 is performed. The raw material mixing step ST11 is a step of mixing ceramic powder as the main component and a sintering aid. Further, if necessary, a binder, a solvent, etc. may be further mixed. Also, the raw material mixing step ST11 may be performed using a pulverizer such as a ball mill or a bead mill.
[0043] Next, the molding step ST12 is performed. It is preferable to use molding methods such as die molding, CIP molding, and rolling granulation for the ceramic curved surface molded body 1. Also, by using die molding, a ceramic spherical molded body 12 with a band as an example of the ceramic curved surface molded body 1 can be produced.
[0044] In the molding step ST12, CIP molding may be performed on the ceramic spherical molded bodies 11 and 12 obtained by die molding or rolling granulation. When producing the ceramic spherical sintered bodies 71 and 72 used for bearing balls, it is preferable to perform CIP molding on the ceramic spherical molded bodies 11 and 12 obtained by die molding or rolling granulation. CIP molding is a method of enclosing the ceramic spherical molded bodies 11 and 12 in the concave portion of a CIP rubber mold and applying isostatic pressure using a liquid. After performing CIP molding, the ceramic curved surface molded body 1 is detached from the concave portion of the CIP rubber mold. Detaching the ceramic spherical molded bodies 11 and 12 from the concave portion of the CIP rubber mold is called rubber mold separation or CIP rubber mold separation.
[0045] After performing CIP rubber mold breaking, it is effective to set the conveyance process of the ceramic curved surface formed body 1 detached from the concave portion to steps ST1 to ST3 (shown in FIG. 1) in the formed body conveyance method according to the embodiment. In that case, the CIP rubber mold becomes the holding container 2, and the ceramic curved surface formed body 1 is dropped from the CIP rubber mold. Also, the forming method may use sheet forming, extrusion molding, or injection molding. A long ceramic formed body obtained by these forming methods may be processed to produce a cylindrical ceramic formed body. By performing forming in the forming step ST12, the ceramic curved surface formed body 1 can be obtained.
[0046] Next, after the forming step ST12, in the conveyance step ST13, for example, after steps ST1 to ST3 shown in FIG. 1, a debinding step ST14 is performed as necessary. The debinding step ST14 is a step of debinding the ceramic curved surface formed body 1 (CIP formed or not CIP formed). By performing the debinding step ST14, a binder or the like in the ceramic curved surface formed body 1 can be burned out. The debinding step ST14 is a step of heating the ceramic curved surface formed body 1 within a range of 400°C or higher and 800°C or lower.
[0047] The debinding step ST14 heats the ceramic curved surface formed body 1 by putting the entire storage container 5 called a sheath, which is stored in the storage step ST3 of step ST3, into a heating furnace. It is effective to set the conveyance process of the ceramic curved surface formed body 1 to the sheath to steps ST1 to ST3 in the formed body conveyance method according to the embodiment. By performing debinding of the ceramic curved surface formed body 1 in the debinding step ST14, a debound body having a curved surface portion can be obtained.
[0048] Next, a sintering step ST15 is performed. The sintering step ST15 is a step of sintering the ceramic curved surface formed body 1, for example, the debound body. The sintering step ST15 is a step of heating the ceramic curved surface formed body 1 within a range of 1500°C or higher and 2000°C or lower. As the sintering step ST15, atmospheric pressure sintering, pressure sintering, hot isostatic pressing (HIP), or the like can be used. Also, respective sintering steps may be combined.
[0049] The sintering process ST15 is carried out in air, a non-oxidizing atmosphere, a reducing atmosphere, or a vacuum. Atmospheric pressure sintering is sintering under controlled conditions of 1 atmosphere (0.9 atm to 1.1 atm, i.e., 0.09 MPa to 0.11 MPa). Pressure sintering is sintering performed by applying a pressure higher than atmospheric pressure. Uniaxial pressure sintering is sometimes called hot pressing. High-pressure pressing (HIP) is a sintering method that uses isotropic pressure with a gas.
[0050] If the sheath can withstand the sintering temperature, the sheath used in the degreasing process ST14 to house the ceramic curved molded body 1 can be used as is in the sintering process ST15. When the sheath is replaced between the degreasing process ST14 and the sintering process ST15, it is effective to use the transport process ST1 to ST3 in the transport method for the molded body according to the embodiment for the transport process of the ceramic curved molded body 1 to be transported into the sheath.
[0051] By performing the sintering process ST15, a curved ceramic sintered body 7 can be obtained. The curved ceramic sintered body 7 can be used for bearing balls, check balls, media, rollers, etc. Therefore, the ceramic sintered body having a spherical portion may be polished or otherwise processed as needed.
[0052] The method for transporting molded bodies according to the embodiment can suppress damage to the ceramic curved molded body 1 during transport. Damage to the ceramic curved molded body 1 can be visually confirmed or not. Visually confirmed damage is when the ceramic curved molded body 1 is cracked or partially chipped. Damage that is not visually confirmed is a small crack in the ceramic curved molded body 1. If a small crack exists in the ceramic curved molded body 1, it will remain as a small crack when it becomes a ceramic curved sintered body 7. Such small cracks are called microcracks. If microcracks exist in the ceramic curved sintered body 7, they may cause cracking or chipping when polishing is performed after the sintering process ST15. With the method for transporting molded bodies and the method for manufacturing sintered bodies according to the embodiment, not only is visually confirmed damage prevented, but the occurrence of microcracks can also be prevented. Microcracks appear white when the surface of the ceramic curved sintered body 7 is observed.
[0053] Furthermore, a metallurgical microscope may be used to observe the surface of the curved ceramic sintered body 7. Microcracks with a length of 500 μm or more may affect wear resistance. By suppressing the occurrence of microcracks in the curved ceramic molded body 1, the yield of the curved ceramic sintered body 7 can also be improved. In other words, this method is suitable for manufacturing the curved ceramic sintered body 7, which requires polishing. However, very small microcracks are likely to be removed during the polishing process of the curved ceramic sintered body 7, so they are unlikely to affect wear resistance.
[0054] (Examples) (Examples 1-7, Comparative Examples 1-2) Among the ceramic curved molded bodies 1, a ceramic spherical molded body 11 of type C and a ceramic spherical molded body 12 with strips of types A, B, and D were prepared as shown in Table 1. Silicon nitride was used as the main component for the ceramic spherical molded bodies 11 and 12. The ceramic spherical molded bodies 11 and 12 are for obtaining primary balls for bearing balls. The diameters of the ceramic spherical molded bodies 11 and 12 are matched to the size of the bearing balls to be used. The presence or absence of the strip portion 122 and the size of the bearing balls to be used, i.e., the diameter of the bearing balls, are as shown in Table 1.
[0055]
[0056] The Type A, B, and D striped ceramic spherical molded bodies 12 were obtained by mold molding and, as shown in Figure 4, have a strip-shaped portion 122 on the outer circumference of the spherical portion 121. The Type C ceramic spherical molded body 11 is obtained after processing to remove the strip-shaped portion 122 shown in Figure 4, as shown in Figure 3. Next, CIP molding was performed on the Type A, B, and D striped ceramic spherical molded bodies 12 using a CIP rubber mold. When performing the rubber mold removal process after CIP molding, a transport process ST13 was carried out using the CIP rubber mold as a holding container 2 under the conditions shown in Table 2.
[0057] In the method of Example 1 in Table 2, 100 banded ceramic spherical molded bodies 12 were prepared. Using a CIP rubber mold (a CIP rubber mold having three or more recesses), the CIP rubber molds of all 100 banded ceramic spherical molded bodies 12 were removed, and then the CIP rubber molds were moved, causing the 100 banded ceramic spherical molded bodies 12 to fall onto the cushioning material 3. The 100 banded ceramic spherical molded bodies 12 that rolled down the slope of the storage container 5 and fell into the container 5 were picked up one by one from the container 5. The percentage of the 100 banded ceramic spherical molded bodies 12 picked up from the storage container 5 that were damaged was then measured. The presence or absence of damage to the 100 banded ceramic spherical molded bodies 12 was confirmed visually.
[0058] Furthermore, in the methods of Examples 2 to 7 and Comparative Examples 1 to 2, 100 ceramic spherical molded bodies 11 or striped ceramic spherical molded bodies 12 were prepared in the same manner, and the presence or absence of damage to the 100 ceramic spherical molded bodies 11 and 12 picked up from the storage container 5 was checked. Among the 100 ceramic spherical molded bodies 11 and 12 that fall from the holding container 2, some detach from the CIP rubber mold and directly collide with the cushioning material 3, while others collide with the upper side of other ceramic spherical molded bodies 11 and 12 that are in contact with the cushioning material 3 before colliding with the cushioning material 3. Considering the latter, it is preferable that the cushioning material 3 be provided over the entire inclined surface of the base material 4.
[0059] Comparative Example 1 was conducted without using the cushioning material 3 in the dropping process, while Comparative Example 2 was conducted using the cushioning material 3 with a rebound modulus of 50% in the dropping process. Furthermore, the cushioning material 3 used in Examples 1-7 and Comparative Examples 1 and 2 had a thickness of 2 mm. The hardness of the cushioning material 3 was measured according to JIS K 6253-3. Additionally, the base material 4 used in Examples 1-7 and Comparative Examples 1 and 2 was given an incline. This created a mechanism where the ceramic spherical molded bodies 11 and 12, upon dropping onto the incline of the cushioning material 3, rolled along the incline. The incline angle of the base material 4 was within the range of 10 degrees to 40 degrees. The conditions and the resulting damage rates are shown in Table 2.
[0060]
[0061] As can be seen from Table 2, the fracture rates of the ceramic spherical molded bodies 11 and 12 were good, between 0 and 10% in Examples 1 to 7. In Example 6, the fracture rate was higher than in Examples 1 to 5 because the vertical drop distance exceeded 300 mm. Therefore, it can be seen that a vertical drop distance L of 300 mm or less, and more preferably 200 mm or less, is preferable. In addition, in Example 7, although the rebound modulus of the cushioning material 3 was 40% or less, the fracture rate was higher than in Examples 1 to 5 because the hardness exceeded 40. Therefore, it can be seen that a cushioning material 3 with a rebound modulus of 40% or less and a hardness of 45 or less is preferable.
[0062] Furthermore, in Example 5, the vertical drop distance L was set to 25 mm. As can be seen from the 0% failure rate, it can be seen that even if it is less than 25 mm, the effect on the failure rate is small. On the other hand, in Comparative Examples 1 and 2, where the favorable conditions were not met, the failure rate increased significantly. In particular, it can be seen that the effect of suppressing the failure rate is small when the rebound elastic modulus of the cushioning material 3 is high, as in Comparative Example 2. In addition, in the examples and comparative examples, the inclination angle of the slope of the base material 4 was set to 10 degrees or more and 40 degrees or less, so there was no congestion of the ceramic spherical molded bodies 11 and 12 on the base material 4 and the receiving process ST3 was smooth.
[0063] Next, in Example 1, after the molding process ST12, 100 banded ceramic spherical molded bodies 12 were picked up from the container 5 after rolling down the slope via the moving process ST1 (including the rubber mold removal process) and the dropping process ST2. These 100 banded ceramic spherical molded bodies 12 were then subjected to a degreasing process and a sintering process to produce 100 banded ceramic spherical sintered bodies 72. Each of the 100 banded ceramic spherical sintered bodies 72 was polished to a surface roughness Ra of 0.01 μm or less to produce bearing balls. 100 bearing balls were produced from each, and the percentage of those with microcracks was measured. Similarly, in the methods of Examples 2-7 and Comparative Examples 1-2, 100 bearing balls were produced from 100 ceramic spherical molded bodies 11 or 100 banded ceramic spherical molded bodies 12, and the percentage of those with microcracks was measured. The results of the microcrack occurrence rates in these cases are shown in Table 3.
[0064]
[0065] As can be seen from Table 3, in Examples 1 to 7, the occurrence of microcracks in the bearing balls was suppressed to 5% or less. Microcracks can only be observed in sintered bodies. Suppressing microcracks is effective in improving the yield of ceramic curved sintered bodies 7, such as ceramic spherical sintered bodies 71 and 72 which have spherical portions that require polishing.
[0066] According to at least one embodiment described above, the aim is to suppress damage to curved molded bodies, such as ceramic spherical molded bodies 11 and 12, during transport involving dropping.
[0067] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Modifications of these embodiments are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Furthermore, the embodiments described above can be implemented in combination with each other.
Claims
1. A method for transporting a molded body, comprising: a moving step of moving a holding container that holds a curved molded body, which is a molded body having a curved portion on part or all of its surface, to above a base material; a dropping step of tilting the holding container after the moving step and dropping the curved molded body onto the base material; and a storage step of rolling the curved molded body on the base material after it has been dropped and then storing the dropped curved molded body in a storage container, wherein a cushioning material with a rebound modulus of 40% or less is provided in at least the area of the slope of the base material that includes the point where the curved molded body falls.
2. The method for transporting a molded body according to claim 1, wherein the curved molded body is a ceramic curved molded body made of ceramics.
3. The method for conveying a molded article according to claim 1 or 2, characterized in that the rebound modulus of the cushioning material is 15% or less.
4. The method for transporting a molded body according to claim 1 or 2, characterized in that the hardness of the cushioning material is 45 or less.
5. The method for transporting a molded body according to claim 3, characterized in that the hardness of the cushioning material is 45 or less.
6. The method for conveying a molded body according to claim 1 or 2, characterized in that the vertical distance of the fall from the holding container to the point of impact on the cushioning material is 300 mm or less.
7. The method for conveying a molded body according to claim 5, characterized in that the vertical distance of the fall from the holding container to the point of impact on the cushioning material is 300 mm or less.
8. The method for transporting a molded body according to claim 1 or 2, wherein the transfer step includes a rubber mold dismantling step of detaching the curved molded body from the recess of the rubber mold used in the CIP (Cold Isostatics Press) process, and after the rubber mold dismantling step, the rubber mold that holds the curved molded body detached from the recess is moved as the holding container.
9. The method for transporting a molded body according to claim 7, wherein the transfer step includes a rubber mold dismantling step of detaching the curved molded body from the recess of the rubber mold used in the CIP process, and after the rubber mold dismantling step, the rubber mold that holds the curved molded body detached from the recess is moved as the holding container.
10. The method for conveying a molded body according to claim 1 or 2, wherein the curved molded body is a spherical molded body having a spherical portion, and the spherical molded body has a strip-shaped portion on the outer circumference of the spherical portion.
11. The method for conveying a molded body according to claim 9, wherein the curved molded body is a spherical molded body having a spherical portion, and the spherical molded body has a strip-shaped portion on the outer circumference of the spherical portion.
12. The method for conveying a molded body according to claim 1 or 2, characterized in that the curved molded body is a spherical molded body having a spherical portion, and the spherical molded body has a diameter of 7 mm or more.
13. The method for conveying a molded body according to claim 11, characterized in that the curved molded body is a spherical molded body having a spherical portion, and the spherical molded body has a diameter of 7 mm or more.
14. The method for transporting a molded body according to claim 1 or 2, characterized in that the curved molded body mainly consists of silicon nitride.
15. The method for conveying a molded body according to claim 13, characterized in that the curved molded body is mainly composed of silicon nitride.
16. A method for manufacturing a sintered body, comprising: a moving step, a dropping step, and a storage step according to any one of claim 1 or claim 2; and a sintering step, after the storage step, of transporting the storage container containing the curved molded body into a sintering furnace to sinter the curved molded body, thereby producing a curved sintered body having a curved portion on part or all of its surface.
17. A method for manufacturing a sintered body, comprising: a moving step, a dropping step, and a storage step according to claim 13; and a sintering step, after the storage step, of transporting the storage container containing the curved molded body into a sintering furnace to sinter the curved molded body and producing a curved sintered body which is a sintered body having a curved portion on part or all of its surface.
18. A method for manufacturing a sintered body, comprising: a moving step, a dropping step, and a storage step according to claim 15; and a sintering step, after the storage step, of transporting the storage container containing the curved molded body into a sintering furnace to sinter the curved molded body and producing a curved sintered body which is a sintered body having a curved portion on part or all of its surface.