JP5740638B2 - Manufacturing method of ceramic product and molding die used therefor - Google Patents

Description

  The present invention relates to a method for producing a hollow ceramic product and a mold used for the method.

  As a method for producing a cylindrical ceramic product, a centrifugal molding method in which a cylindrical molding die such as a gypsum mold or a resin is rotated has been proposed (see Patent Document 1, Patent Document 2, and Non-Patent Document 1). Further, a molding method in which rocking or vibration is applied based on a casting molding method has been proposed (see Patent Document 3).

JP 09-193130 A Japanese Patent Laid-Open No. 05-253921 JP 2005-153495 A

AIST / Ceramics forming technology (URL: http://unit.aist.go.jp/chubu/ci/vm/sub3/sub3_06_3.html)

  However, the centrifugal molding method or the molding method with rocking or vibration is not preferable from the viewpoint of saving the equipment cost because the mold is likely to be deteriorated or broken. Further, since stress always acts on the inking layer during molding, sagging or collapse due to thixotropy occurs in the inking layer that is not completely dried and solidified. As a result, cracks and the like due to green density unevenness and residual stress occur in the molded body. This becomes more prominent as the compact becomes larger.

  Further, according to the centrifugal molding method, the roundness of the sintered body tends to decrease due to the influence of gravity because the mold is rotated around the axis with the axis thereof being substantially horizontal. In addition, the product shape is limited to a cylindrical shape due to the property of utilizing a rotating action.

  Then, this invention makes it a subject to provide the manufacturing method of the said ceramic product etc. which can aim at quality improvement, aiming at the enlargement or heightening of a hollow ceramic product.

The present invention is a method for producing a hollow ceramic product, comprising a bottomed cylindrical frame having a cylindrical side part made of a porous water-absorbing material and a bottom part made of a non-water-absorbing material, and the frame A step of installing a molding die provided at least with a core made of a non-water-absorbing material at the surface layer so that the axial direction of the cylinder is aligned with the vertical direction, and the particle size distribution of the ceramic powder is The frequency of particles having a single peak and having a median diameter (M) of all particles is 10% or more, the median diameter (M) is 0.5 [μm], and the median diameter (M The ratio (B / M) of the minimum particle diameter (B) to 0.2) is 0.2 or more, and the ratio (A / M) of the maximum particle diameter (A) to the median diameter (M) is 11.0 or less. A step of adjusting the raw material so that the particle size distribution is adjusted. A step of adjusting the slurry in which the powder is dispersed, a step of injecting the slurry into the mold, and after the flow of the slurry in the mold is settled, along the outer surface of the side portion of the frame By vacuum-sucking a space that is evenly arranged in each of a plurality of directions and is airtight with respect to the outer surface of the side portion of the frame at a pressure equal to or higher than -90 [kPa], A step of causing the water-absorbing material to absorb moisture in the slurry, a step of forming the ceramic molded body by depositing the ceramic powder on the mold, and a step of firing the ceramic molded body after drying. It is characterized by including.

According to the method of the present invention, a slurry in which ceramic powder as a raw material is dispersed is injected into a mold, and after the flow of the slurry is converged, the airtightness formed outside the side portion of the bottomed cylindrical frame The space is vacuumed with a high degree of vacuum (suction pressure equal to or higher than −90 [kPa]). Since the airtight spaces are evenly arranged in each of a plurality of directions along the outer surface of the side portion of the frame, the ceramic powder layer is uniformly formed in each normal direction of the surface of the side portion.

  During the formation of the ceramic powder layer, pressure is not applied to the slurry, but due to the suction pressure acting on the side of the frame and the capillary suction force of the water-absorbing material constituting the frame, Moisture is removed. For this reason, a molded object can be formed, without the flaking layer of the raw material powder in the side part vicinity of a frame leaving | separating from the said side part. Further, since at least the surface of the core is made of a non-water-absorbing material, water absorption proceeds only from the direction from the core toward the outside, so that no weld line is generated in the molded body.

  Furthermore, the thickness direction of the ceramic powder as the raw material is the normal direction of the side surface, that is, the horizontal direction and is perpendicular to the vertical direction. For this reason, by adjusting the particle size distribution of the ceramic powder so as to reduce the influence of the sedimentation effect, there is no difference in density or unevenness in the height direction or the vertical direction of the molded body, and deformation, distortion and cracks are not caused. A high-quality molded body and sintered body without the above can be obtained.

Therefore, it is possible to improve the quality of the hollow ceramic product while increasing the size or height of the hollow ceramic product. The particle size can be adjusted by classification before mixing and a mixing treatment method.

The molding die of the present invention comprises a cylindrical or bottomed cylindrical outer frame, an inner frame having a cylindrical side portion made of a porous water-absorbing material and a bottom portion made of a non-water-absorbing material, An inner core provided with at least a surface layer made of a non-water-absorbing material, and arranged uniformly in each of a plurality of directions along the outer surface of the side portion of the inner frame, with respect to the vacuum suction device A suction path that forms a space that is airtightly formed with respect to the outer surface of the side portion of the inner frame by being hermetically connected is formed at a location where the outer frame contacts the side portion of the inner frame. It is characterized by.

  By using the mold of the present invention in the production of a cylindrical ceramic product, as described above, a hollow ceramic product of any desired shape having a high quality can be produced while being large or tall.

Fig.1 (a) is a top view of the shaping | molding die used for the method of this invention. FIG.1 (b) is sectional drawing of the said shaping | molding die along the Ib-Ib line | wire of Fig.1 (a). Explanatory drawing regarding the manufacturing method of the ceramic product as one Embodiment of this invention.

  As an embodiment of the present invention, a method for producing an alumina sintered body as a ceramic product will be described.

(Slurry adjustment)
The particle size distribution of the ceramic powder has a single peak, the median size (M) is 0.5 [μm], the frequency is 10 [%] or more, and the maximum particle size / median size ratio (A / M) was 11.0 or less, and the slurry was adjusted so that the minimum particle diameter / median diameter ratio (B / M) was 0.2 or more.

  In addition to the alumina powder, the ceramic powder may be various ceramic powders made of silicon carbide, silicon nitride, zirconia, spinel, yttria, or the like. As the dispersant, a known one such as a polycarboxylic acid type is used. The solvent is preferably water, particularly ion-exchanged water with few impurities, but a known solvent such as alcohol can be used. As the binder, known materials such as polyvinyl alcohol and acrylic emulsion are used. Moreover, additives, such as a pH adjuster or an antifoamer, may be added as needed.

(Configuration of mold)
The mold shown in FIGS. 1A and 1B includes an outer frame 10, an inner frame 20, and a core 30.

  The outer frame 10 is made of substantially bottomed cylindrical stainless steel, and its height is, for example, 950 [mm]. As shown in FIG. 1A, the outer frame 10 is disposed so as to have a rotational symmetry (for example, eight rotational symmetry) in the circumferential direction, and as shown in FIG. As shown, a plurality of suction ports 12 arranged at equal intervals in the vertical direction (axial direction) (so as to have translational symmetry in the vertical direction) are provided.

  The inner frame 20 is in contact with the inner side of the outer frame 10 over the entire circumference, and is provided with a side part 21 made of a cylindrical porous water-absorbing material (for example, gypsum) and a disk provided to close the bottom of the side part 21. And a bottom 22 made of a non-water-absorbing material (for example, chloroprene rubber). The inner diameter of the inner frame 20 is, for example, 800 [mm], and the depth thereof is, for example, 950 [mm]. In order to obtain a molded body having a desired height, a part of the side portion 21 made of gypsum is covered with a resin or the like, thereby suppressing the water absorption action.

  The suction port 12 is airtightly connected to a vacuum suction device (such as a vacuum pump), thereby forming an airtight space with respect to the outer surface of the side portion 21 of the inner frame 20. By arranging the plurality of suction ports 12 as described above, the airtight spaces are equally arranged in each of the circumferential direction and the axial direction along the outer surface of the side portion 21 of the inner frame 20.

  In addition, about each of the some direction along the outer surface of the side part 21 of the inner frame 20, a suction path | route can be formed with various forms so that airtight space may be arrange | positioned equally. For example, a lattice-like suction groove in which elongated members extend in each of the plurality of directions and a suction port communicating with the suction groove may be formed inside the side wall of the outer frame 10 as a suction path.

  The core 30 is made of a non-water-absorbing material (for example, neoprene rubber having a shore hardness of 40 °) such as rubber, silicon or plastic having a shore hardness A (JIS) of 20 to 60 °. The core 30 is disposed inside the inner frame 20 and has a substantially cylindrical shape having the same height as the depth of the inner frame 20 and has a diameter of, for example, 600 [mm].

  The shape of each of the outer frame 10, the inner frame 20, and the core 30 can be arbitrarily changed to create a ceramic product having an arbitrary shape. The side wall 21 of the outer frame 10 and the side portion 21 of the inner frame 20 are not only cylindrical, but also are arbitrarily surrounded by a triangular cylinder, a rectangular cylinder, a trapezoidal cylinder, a polygonal cylinder, or an elliptic cylinder. It may be a shape.

  In addition to a columnar shape, a core 30 having various shapes such as a prismatic shape may be used. The thickness of the molded body and the sintered body can be adjusted by adjusting the dimensions of the core 30. Also. The volume ratio of the hollow portion to the entire ceramic product can be adjusted in a range of 5 to 95 [%].

(Manufacturing method of ceramic products)
After the mold shown in FIG. 1 is installed so that the surface of the bottom portion 22 which is the surface of the ceramic powder is horizontal, the slurry whose particle size is adjusted as described above is shown in FIG. ) Is injected into the mold as shown. The slurry may be charged into the mold from the beginning in an amount necessary for the desired shape in accordance with a batch method, or may be supplied from the stirring tank or the like to the mold as occasion demands.

  From the stage where the flow of the slurry injected into the molding die was settled, the inside of the molding die was vacuum-sucked through the suction port 12, thereby producing a molded body by inking. During vacuum suction, the degree of vacuum was adjusted to -90 [kPa] or higher. As a result, as shown in FIGS. 2B and 2C, the inking proceeds from the radially outer side, and the thickness of the molded body P gradually increases.

  When the height of the molded body P reached the desired height (600 [mm]), the surplus slurry on the inking layer was discharged (mud). In addition, the air-tight space formed by the suction port 12 was vacuum-sucked at a pressure equal to or higher than −90 [kPa] over a predetermined time, whereby water absorption by the side portion 21 was performed.

  Further, the molded product P was removed. By continuing the suction even after the molded body P is molded, the molded body P is efficiently dried, and the release from the mold becomes rapid. The core 30 is pulled out when molding is completed. As a result, as shown in FIG. 2D, a molded body P having a cylindrical shape (height 600 [mm], outer diameter 800 [mm], inner diameter 600 [mm]) was obtained.

  And after the molded object P was dried and further raw-processed as needed, it was baked, and the cylindrical ceramic product (sintered body) was manufactured. In addition, the sintered compact which has a hollow part may be created by baking the molded object P in the state which hold | maintained the core 30, and burning the core 30. FIG.

  Commercially available alumina powder (AL-160SG-4, Showa Denko Co., Ltd., purity 99.7 [%]), binder (WA-320, Mitsui Toatsu Chemical Co., Ltd.), dispersant (KE-552, Kyoyo Chemical Co., Ltd.) ) And ion-exchanged water were added, and the slurry was adjusted by grinding and mixing.

  The frequency of median diameter (0.5 [μm]) is 10 [%], the minimum particle diameter / median diameter ratio (B / M) is 0.2, and the maximum particle diameter / median diameter ratio (A / M) is used, and a slurry whose particle size distribution is adjusted to 11.0 is used, and the vacuum suction pressure is adjusted to be the same as or stronger than −90 [kPa], whereby the molded article of Example 1 And a sintered body was obtained.

  The frequency of the median diameter is 16 [%], the minimum particle diameter / median diameter ratio (B / M) is 0.2, and the maximum particle diameter / median diameter ratio (A / M) is 9.5. A molded body and a sintered body of Example 2 were obtained under the same conditions as in Example 1 except that a slurry having a controlled particle size distribution was used.

  The frequency of the median diameter is 21 [%], the minimum particle diameter / median diameter ratio (B / M) is 0.5, and the maximum particle diameter / median diameter ratio (A / M) is 11.0. A molded body and a sintered body of Example 3 were obtained under the same conditions as in Example 1 except that a slurry having a controlled particle size distribution was used.

  The frequency of the median diameter is 15 [%], the minimum particle diameter / median diameter ratio (B / M) is 0.3, and the maximum particle diameter / median diameter ratio (A / M) is 9.0. Example 4 and a sintered body were obtained under the same conditions as in Example 1 except that a slurry with a controlled particle size distribution was used.

  The frequency of the median diameter is 14 [%], the minimum particle diameter / median diameter ratio (B / M) is 0.3, and the maximum particle diameter / median diameter ratio (A / M) is 11.0. A molded body and a sintered body of Example 5 were obtained under the same conditions as in Example 1 except that a slurry having a controlled particle size distribution was used.

  The frequency of the median diameter is 18 [%], the minimum particle diameter / median diameter ratio (B / M) is 0.5, and the maximum particle diameter / median diameter ratio (A / M) is 5.0. A molded body and a sintered body of Example 6 were obtained under the same conditions as in Example 1 except that a slurry having a controlled particle size distribution was used.

  The frequency of the median diameter is 14 [%], the minimum particle diameter / median diameter ratio (B / M) is 0.3, and the maximum particle diameter / median diameter ratio (A / M) is 4.0. A molded body and a sintered body of Example 7 were obtained under the same conditions as in Example 1 except that a slurry having a controlled particle size distribution was used.

  Table 1 shows the conditions for forming the molded bodies of Examples 1 to 7, the measurement results of the relative densities of the molded bodies and the sintered bodies, and the observation results of the appearance. In each example and comparative example described later, two molded bodies are produced, a part of one molded body is cut out, the green density is evaluated from the cut-out portion, and the other molded body is baked. A sintered body was produced.

  As is clear from Table 1, variations in the relative density in the vertical direction and radial direction of each molded body of Examples 1 to 7 were small, and cracks due to drying shrinkage of the molded body were not observed in appearance after drying. . In addition, the relative densities of the sintered bodies of Examples 1 to 7 were all 99% or more and very dense, warped in appearance, and deformation and cracking were not observed.

  In the same manner as in each of Examples 1 to 7, when a molded body was created while a slurry whose particle size distribution was adjusted was poured into a molding die, similarly, molding with little variation in raw density and no cracking When a body was obtained, raw-processed and fired, a sintered body with no warpage, deformation and cracking, and a relative density of 99 [%] or higher was obtained.

Comparative example

[Comparative Example 1]

Compared to Examples 1 to 7, the minimum particle diameter / median diameter ratio (B / M) is 0.2 or more, and the maximum particle diameter / median diameter ratio (A / M) is 11.0 or less. On the other hand, the same conditions as in Examples 1 to 7 except that a slurry having a different particle size distribution was used in that the frequency of the median diameter was less than 10% (9%). Thus, a molded body and a sintered body of Comparative Example 1 were obtained.
[Comparative Example 2]

Compared with Examples 1 to 7, the frequency of the median diameter is 10%, and the maximum particle diameter / median diameter ratio (A / M) is 11.0 or less, which is the same, whereas the smallest particle Comparative Example under the same conditions as in Examples 1-7, except that a slurry having a different particle size distribution was used in that the diameter / median diameter ratio (B / M) was less than 0.2 (0.1) 2 shaped bodies were obtained.
[Comparative Example 3]

Compared with Examples 1-7, the frequency of the median diameter is 10 [%] or more, and the minimum particle diameter / median diameter ratio (B / M) is 0.2 or more. Under the same conditions as in Examples 1-7, except that a slurry having a different particle size distribution was used in that the particle size / median size ratio (A / M) exceeded 11.0 (12.0). The molded body of Comparative Example 3 was obtained.
[Comparative Example 4]

Besides the vacuum suction pressure is weaker than -90 [kPa] (-70 [kPa]), the frequency of the median diameter is 10 [%], and the minimum particle diameter / median diameter ratio (B / M) is 0.2 or more. And a comparative example under the same conditions as in Examples 1 to 7 including that a slurry having a particle size distribution with a maximum particle size / median size ratio (A / M) of 11.0 or less was used. 4 shaped bodies were obtained.
[Comparative Example 5]

Compared with Examples 1-7, while the frequency of the median diameter is equal to or more than 10%, the minimum particle diameter / median diameter ratio (B / M) is less than 0.2 (0.1). Example 1 except that a slurry having a different particle size distribution was used in that the maximum particle size / median size ratio (A / M) exceeded 11.0 (21.0). The molded object and the sintered compact of the comparative example 5 were obtained on the same conditions as -7.
[Comparative Example 6]

Compared with Examples 1-7, while the minimum particle diameter / median diameter ratio (B / M) agrees with 0.2 or more (0.3), the frequency of the median diameter is less than 10% ( 7 [%]), and slurry having different particle size distribution was used in that the maximum particle size / median size ratio (A / M) exceeded 11.0 (16.0). In addition, the molded article of Comparative Example 6 was obtained under the same conditions as in Examples 1 to 7, except that the vacuum suction pressure was weaker than −90 [kPa] (−89 [kPa]).
[Comparative Example 7]

  Compared with Examples 1 to 7, the maximum particle diameter / median diameter ratio (A / M) coincides with that of 11.0 or less, while the frequency of the median diameter is less than 10% (8 [%]). And the slurry having different particle size distribution was used in that the minimum particle size / median size ratio (B / M) was less than 0.2 (0.1). A molded body and a sintered body of Comparative Example 7 were obtained under the same conditions.

  Table 2 shows the conditions for forming the molded bodies of Comparative Examples 1 to 7, the measurement results of the relative densities of the molded bodies and the sintered bodies, and the observation results of the appearance.

  As is apparent from Table 2, cracks were not observed in the molded bodies of Comparative Examples 1, 5, and 7, but the sintered bodies of Comparative Examples 1, 5, and 7 were partially insufficiently densified, And cracks were observed. In the molded bodies of Comparative Examples 2 to 4 and 6, a difference in green density occurred in the upper and lower directions, and cracks were observed.

  According to the method of the present invention, a slurry in which ceramic powder as a raw material is dispersed is injected into a mold, and after the convection and flow of the slurry converge, the slurry is formed outside the side portion of the bottomed cylindrical frame. The airtight space is vacuum-sucked at a high degree of vacuum (the same or strong suction pressure as −90 [kPa]). The airtight space formed by the suction port 12 is evenly arranged in each of a plurality of directions (circumferential direction and axial direction) along the outer surface of the side portion 21 of the inner frame (frame) 20. The inking layer is uniformly formed in each normal direction of the surface of the side portion 21.

  When the ceramic powder layer is formed, pressure is not applied to the slurry, but the suction pressure acting on the side portion 21 of the inner frame 20 and the capillaries of the water-absorbing material such as gypsum constituting the inner frame 21. Water in the slurry is removed by the action of the suction force. For this reason, the molded object P can be formed, without the flaking layer of the raw material powder in the side part 21 vicinity of the inner frame 20 leaving | separating from the said side part 21 (refer FIG.2 (b)). Further, since at least the surface of the core 30 is made of a non-water-absorbing material, water absorption proceeds only from the direction toward the outside from the core 30, so that no weld line is generated in the molded body P. Further, since the core 30 having flexibility is used even when the molded body P is dried and contracted, the molded body P is not cracked even when the molded body P holds the core 30.

  Furthermore, the thickness direction of the ceramic powder as the raw material is the normal direction of the side surface, that is, the horizontal direction and is perpendicular to the vertical direction. For this reason, by adjusting the particle size distribution of the ceramic powder so as to reduce the influence of the sedimentation effect, there is no difference in density or unevenness in the height direction or the vertical direction of the molded body, and deformation, distortion and cracks are not caused. A high-quality molded body and sintered body without the above can be obtained.

  Compared to conventional solid casting and the like, there is less size restriction and it can be applied from small to large. For example, one side is 400 [mm] or more or a diameter is 300 [mm] or more, and the wall thickness is 40 [mm] or more. Large-walled shaped compacts and ceramic products can be created.

DESCRIPTION OF SYMBOLS 10 ... Outer frame, 12 ... Suction port, 20 ... Inner frame, 21 ... Side part, 22 ... Bottom part, 30 ... Core, P ... Molded object.

Claims (2)

A method for producing a hollow ceramic product, comprising:
A bottomed cylindrical frame having a cylindrical side portion made of a porous water-absorbing material and a bottom portion made of a non-water-absorbing material, and at least a surface layer provided inside the frame is made of a non-water-absorbing material A step of installing a molding die provided with a child so that the axial direction of the cylinder is aligned with the vertical direction;
The particle size distribution of the ceramic powder has a single peak, the frequency of particles having a median diameter (M) of all the particles is 10% or more, and the median diameter (M) is 0.5 [μm]. , and the and the ratio of the minimum particle diameter to the median diameter (M) (B) (B / M) of 0.2 or more, and the ratio of the maximum particle diameter (a) with respect to a median diameter (M) (a / M ) Adjusting the raw material so that it becomes 11.0 or less,
Adjusting the slurry in which the ceramic powder having a controlled particle size distribution is dispersed;
Injecting the slurry into the mold;
After the flow of the slurry in the mold is settled, the slurry is evenly arranged in each of a plurality of directions along the outer surface of the side portion of the frame, and is hermetically formed with respect to the outer surface of the side portion of the frame. By vacuuming the space being at a pressure equal to or higher than −90 [kPa] to cause the water-absorbing material to absorb moisture in the slurry and to allow the ceramic powder to fill the mold. Forming a ceramic molded body;
And drying the ceramic molded body, followed by firing. A cylindrical or bottomed cylindrical outer frame, an inner frame having a cylindrical side part made of a porous water-absorbing material and a bottom part made of a non-water-absorbing material, and at least a surface provided inside the inner frame The layer comprises a core made of a non-water-absorbing material,
Evenly arranged in each of a plurality of directions along the outer surface of the side portion of the inner frame, and hermetically connected to the outer surface of the side portion of the inner frame by being hermetically connected to the vacuum suction device. A molding die characterized in that a suction path that forms a formed space is formed at a location in the outer frame that abuts against a side of the inner frame.