JP3425457B2 - Ceramic slip casting method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slip-cast molding method for ceramics, and more particularly to a slip-cast molding method for producing a ceramic molding containing a fibrous ceramic with high quality in a short time.

[0002]

2. Description of the Related Art A typical method for producing a ceramic molded body is a slip cast molding method. In this slip cast molding method, a mold made of a material having a water absorption property such as gypsum is usually used, and the slip (ceramic powder suspension) injected into the cavity of this mold absorbs moisture to solidify the slip. It is done by doing. The green obtained is fired to obtain the final ceramic member. This method is generally suitable for producing a molded product having a complicated shape.

In the slip cast molding, an organic binder such as carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, etc. is generally added to the slip in order to improve the dry strength of the green. However, when these organic binders are used, the green green strength is reduced and the shrinkage ratio is increased, so that cracks are likely to occur at the time of release and drying. In addition, since a degreasing step is required before firing, there is a drawback that it takes time.

Therefore, fibrous ceramics have been added to slips without using an organic binder. Since green (FRG) containing fibrous ceramic has an appropriate green strength, it can be easily released from the mold. Further, since the shrinkage during drying is small and it has an appropriate elastic force, the occurrence of cracks and cracks is small. Furthermore, since there is no need for a degreasing step, productivity can be improved.

However, when slips to which fibrous ceramics are added are cast at normal pressure, the dehydration speed of the slips is low, during which fibrous ceramics may precipitate downward in the slips. In this way, the fibrous ceramic is unevenly distributed, and the quality of the ceramic molded body having uneven composition is not stable. Further, in the case of manufacturing a large-sized thick-walled ceramic molded body, the slip-cast atmospheric pressure molding method has a drawback that it takes too much time.

Therefore, it is an object of the present invention to provide a method of producing a ceramic having high strength with stable quality and in a short time.

[0007]

As a result of earnest research in view of the above-mentioned object, the inventors of the present invention injected a slip of ceramic to which a fibrous ceramic is added into a cavity of a mold and pressurize the slip. By molding
The present invention has been completed by discovering that a ceramic molded body having high composition strength and high strength can be obtained in a short time.

That is, in the ceramic slip-cast molding method of the present invention, after a ceramic slip in which a part of the components is fibrous is injected into the cavity of the mold, the slip is pressed to obtain a fibrous ceramic. It is characterized by solidifying in a well dispersed state.

[0009]

The present invention will be described in detail below with reference to the accompanying drawings. First, a slip cast molding apparatus capable of carrying out the method of the present invention will be described. In this embodiment, a molding device for a rotor of an axial turbine will be described as an example, but the present invention is not limited to this.

As illustrated in FIG. 1, the slip casting molding apparatus has a molding die 1 and a closed box 2 for accommodating the molding die 1. The molding die 1 includes an annular upper die 1a, a middle die 1b which is divided according to the number of blades to form a blade portion of a rotor, and which is annularly installed on the lower surface of the upper die 1a, and a middle die 1b.
And a lower mold 1c having a hole in the center thereof, and a cavity 6 is formed by each mold. The molding die 1 composed of each die may be made of a water-permeable material such as gypsum.

The closed box 2 has a peep window 9 and a molding die 1
Upper cylindrical member 2a that closely adheres to the upper part of upper mold 1a, upper annular member 2b that closely adheres to the upper part of upper mold 1a, and side parts of upper mold 1a, middle mold 1b and lower mold 1c of mold 1 , The side cylindrical members 2c, 2d, 2e divided into a plurality of parts, the lower mold 1c and the bottom of the side cylindrical member 2e, and the concentric circles on the joint surface with the lower mold 1c. And a bottom member 2f having a groove portion 2g. The closed box 2 accommodates the mold 1 in a sealed manner so that the moisture absorbed by the mold 1 can be sucked by depressurizing the closed box 2.

The slip casting molding apparatus of this embodiment includes, in addition to the molding die 1 and the closed box 2 described above, a pressurized air supply pipe 4 that penetrates the upper cylindrical member 2a and communicates with the cavity 6, and slip replenishment. Cavity supply pipe 3 penetrating the lower pipe 1c and the bottom member 2f and communicating with the cavity 6
And a suction pipe 5 connected to the side portion of the bottom member 2f and communicating with the groove 2g. The slip supply pipe 3 is connected to a slip tank (not shown) and can supply the slip 7 into the cavity 6. The slip replenishment tube 8 is
It is connected to the slip replenishment tank 82, and the slip 7 can be replenished in the cavity 6. The pressurized air supply pipe 4 is connected to a compressor (not shown), and pressurized air can be blown into the cavity 6 to pressurize the slip 7. The suction pipe 5 is also connected to the compressor in the same manner. By vacuuming, the groove 2g is depressurized, and the water absorbed by the mold 1 can be sucked through the groove 2g. The slip supply pipe 3, the slip replenishment pipe 8, the pressurized air supply pipe 4 and the suction pipe 5 have valves 31, 81, 41 and 51, respectively, and the pressures inside the pipe and the cavity 6 are atmospheric pressure. Can be returned to.

The slip casting molding apparatus of this embodiment preferably has a non-water absorbing member 10 in the upper region of the cavity 6. The non-water absorbent member 10 is preferably made of Teflon, machinable wax, various resins, or the like. By providing the non-water-absorptive member 10 in the upper region of the cavity 6 in this way, it is possible to prevent shrinkage cavities that are likely to occur inside a large-sized thick-walled molded body.

When molding a rotor of an axial turbine having an upper region having a small diameter as in the present embodiment, if the non-water absorbing member 10 is not provided, the inking of the slip 7 proceeds substantially uniformly in the entire area of the cavity 6. Therefore, as shown in FIG. 2, while the slip 7 in the cavity 6 still has a non-mealing portion, the void between the meat-forming layers in the upper region is closed.
Then, when the slip 7 left inside is inked, the supply of new slip 7 is stopped, and as a result, a shrinkage cavity is formed. However, by providing the non-water-absorptive member 10 in the upper region of the cavity 6, the solidification of the slip 7 in the upper region is delayed, and after the central part of the region forming the central part of the molded body is completely inked. Solidify. When the last solidified portion includes the surface of the molded body, shrinkage solidification does not occur when shrinking and solidifying.

In this embodiment, the non-water-absorbing member 10 has a cylindrical shape, but the non-water-absorbing member 10 of the present invention is not limited to such a shape, and is suitable in consideration of the balance between the shrinkage cavity preventing effect and the molding speed. Any shape may be used. Similarly, the non-water absorbent member 10 may be installed at an appropriate position in the upper region of the cavity in consideration of the balance between the shrinkage cavity prevention effect and the molding speed.

The slip cast molding apparatus having the closed box 2 and the non-water-absorbing member 10 has been described above as an example. However, when only the pressure molding is performed without the reduced pressure molding, the closed box 2 is used.
Also, the suction tube 5 may be omitted.

Slip cast molding is performed using the above apparatus.
The method of the present invention to be performed will be described below. (1) Slip preparation The slip 7 used in the method of the invention is a fibrous material.
Contains ceramics. Matrix ceramic
The raw material is not particularly limited, and includes nitride-based, oxide-based,
Borides, carbides and the like can be used.
The fibrous ceramic is also not particularly limited, but Si₃N_Four,
Al₂O₃It is preferable to use ceramics made of
Yes. In particular, Si₃N_FourIs the same material as the matrix after sintering
Therefore, it is preferable that Al₂O₃Is a sintering aid and
It is preferable because it is easy to form a filament.

The diameter of the fibrous ceramic is preferably 20 μm or less, more preferably 10 μm or less. The fiber length is
10 to 1000 μm is preferable, and 200 to 800 μm is particularly preferable. If the diameter exceeds 20 μm and the fiber length exceeds 1000 μm, the density of the green becomes low and the green strength and the sintered body strength decrease. Further, if the fiber length is less than 10 μm, the strength of the green becomes low.

Here, when the Al ₂ O ₃ fiber (diameter _{3 to} 10 μm, fiber length 200 to 300 μm) was added to the Si ₃ N ₄ slip, the addition amount of Al ₂ O ₃ fiber and the elongation rate of the green were measured. Is shown in the graph of FIG. 3, and the relationship between the added amount of Al ₂ O ₃ fiber and the three-point bending strength of the green is shown in the graph of FIG. The addition amount is represented by weight% when the total amount of the matrix and Al ₂ O ₃ fibers is 100% by weight. As illustrated in the graphs of FIGS. 3 and 4, in order for the green to have appropriate elongation and strength, the addition amount of the fibrous ceramic is preferably 3% by weight or more, and particularly preferably 5% by weight or more. . On the other hand, although not shown in the graph, when the addition amount of the fibrous ceramic exceeds 20% by weight, the density of the green becomes low and the strength is rather lowered. Therefore, the addition amount of the fibrous ceramic is preferably 3 to 15% by weight, particularly 5 to 10% by weight.
Weight percent is preferred.

If necessary, a sintering aid, a dispersant, etc. are added to the ceramic raw material to which the fibrous ceramic is added as described above, and then water is mixed as a medium to prepare a uniform slip 7. To do. It is not necessary to add an organic binder to the slip to which the fibrous ceramic is added.

(2) Slip Injection After the obtained slip 7 is filled in the slip tank, the valve 41 and the valve 31 of the pressurized air supply pipe 4 are opened, and the slip 7 is inserted from the slip supply pipe 3 into the cavity 6. Inject. At this time, it is preferable that the slip 7 is slowly injected by gravity or the like. If the injection speed of the slip 7 is too high, air may be trapped when entering the cavity 6 and pinholes or the like may be generated in the obtained green. After supplying the slip 7 by a predetermined amount, the valve 31 and the valve 41 are closed.

(3) Pressurization (and Decompression) Molding Pressurized air is introduced into the cavity 6 through the pressurized air supply pipe 4, and the slip 7 is pressurized. The speed of dehydration of the pressurized slip 7 is faster than that in the case of normal pressure molding, and the molded body is solidified before the fibrous ceramic is precipitated. Further, the pressurization increases the flow velocity of the slip 7, and the slip 7 becomes dense. Therefore, the obtained green has high density without uneven distribution of fibrous ceramics. The pressure due to the pressurized air, which varies depending on the shape of the viscosity and the cavity 6 of the slip 7, it is preferable to be 2 to 10 kg / cm ² or so, especially 2~5kg / cm ² is preferred. Pressure is 2kg / cm ²
If it is less than 10 kg / cm ² , the above effect cannot be obtained, and if it exceeds 10 kg / cm ² , the split mold member may be broken.

When performing the above-mentioned pressurization, the inside of the cavity 6 is observed through the observation window 9. At this time, when the slip 7 in the cavity 6 decreases below a predetermined amount, the valve 41 is opened to return the pressure in the cavity 6 to the atmospheric pressure once, and the valve 81 is opened to slip from the slip replenishment tank 82. The slip 7 is replenished through the replenishment tube 8. After replenishing, the valves 81 and 41 are closed and the pressure is applied again.

When the pressure molding is performed as described above, the moisture absorbed in the molding die 1 can be sucked by vacuuming the suction tube 5 at the same time. The degree of reduced pressure at this time is preferably about -75 to -76 cmHg.

(4) Release When the slip 7 in the cavity 6 solidifies and solidifies,
The pressurization (and decompression) is stopped, the valve 41 (and the valve 51) is opened, and the closed box 2 and the molding die 1 are separated. The obtained green contains fibrous ceramics and has an appropriate green strength, so that the mold release can be easily performed.

When the non-water-absorbing member 10 is provided in the upper region of the cavity 6, the slip in the portion surrounded by the non-water-absorbing member 10 may not be solidified. Therefore, even if the non-water-absorbing member 10 is attached and the green is removed. Good. In this case, the green may be left in the atmosphere until the dehydration is completed. After the moisture surrounded by the non-water absorbent member 10 has diffused to some extent, the non-water absorbent member 10 is removed.

The green thus obtained does not contain an organic binder and therefore does not require degreasing treatment. Further, since the shrinkage during drying is small and it has an appropriate elastic force, the occurrence of cracks and cracks is small.

The present invention will be described in more detail with reference to the following specific examples. Example 1 As the slip cast molding apparatus, the molding apparatus for the rotor of the axial turbine shown in FIG. 1 was used. The mold 1 was made of gypsum, and the non-water absorbent member 10 was made of machinable wax. The height of the cavity formed by the mold 1 was 100 mm, and the maximum diameter was 140 mm.

Y ₂ O ₃ fine powder 2.5 having an average particle size of 5 to 10 μm
% By weight, average diameter 3 to 5 μm, average fiber length 300 to 600
1.0% by weight of Al ₂ O ₃ fibers with a mean particle size of 0.4-
42 parts by weight of water was added to 100 parts by weight of a ceramic mixture composed of 0.5 μm α-Si ₃ N ₄ fine powder and mixed by a ball mill for 40 hours to obtain a slip having a viscosity of 0.5 p.

After pouring the obtained slip into the cavity 6 of the above slip cast molding apparatus, 4.0 kg / cm ²
The pressure inside the void 52 is -76 cm.
Pressure and pressure reduction molding was performed for 240 minutes while reducing the pressure to Hg. At that time, the inking time and the square of the inking thickness had a linear relationship. The relationship is shown in the graph of FIG. In addition, Table 1 shows the inking rate constant calculated from the relationship between the inking time and the inking thickness. The inking rate constant is calculated by the formula: (inking thickness) ² / inking time, and the unit is cm ² / sec.

After that, the parts other than the non-water-absorbing member 10 are released from the mold, and left for 60 minutes to allow the water remaining in the portion surrounded by the non-water-absorbing member 10 to diffuse and fully solidify.
Remove 10 to get a green. It took about 5 hours from the start of molding until the green completely solidified.

When the green thus obtained was cut and the inside was observed, no shrinkage cavities or the like were found. Further, the composition of each section shown in FIG. 6 was analyzed using fluorescent X-rays, and the mode diameter, bulk density, true density and porosity of each section shown in FIG. 7 were examined. The results are shown in Tables 2 and 3.

A rotor obtained by sintering the above green at 1800 ° C. for 2 hours was cut, and the true density and three-point bending strength of each section shown in FIG. 7 were examined, and an average value was calculated. The Weibull coefficient of the obtained rotor was examined. The results are shown in Table 4 together with the target values.

Example 2 2.5% by weight of Y ₂ O ₃ fine powder having an average particle size of 5 to 10 μm, and Al ₂ O having an average diameter of 3 to 5 μm and an average fiber length of 300 to 600 μm.
₃ 1.0% by weight of fiber and the rest of the average particle size 0.4-0.5 μm α
42 parts by weight of water was added to 100 parts by weight of a ceramic mixture consisting of -Si ₃ N ₄ fine powder, and mixed by a ball mill for 40 hours to obtain a slip having a viscosity of 0.4 p.

The obtained slip was injected into the cavity of the same slip cast molding apparatus as in Example 1, and 2 kg / c
Pressure molding was performed at a pressure of m ² for 240 minutes. The relationship between the inking time and the inking thickness at that time is shown in the graph of FIG. Also,
Table 1 shows the thickness constants of the thickness calculated from the relationship between the thickness of the thickness and the thickness of the thickness.

Thereafter, the parts other than the non-water-absorbing member are released, and
After left for 60 minutes, the water remaining in the portion surrounded by the non-water-absorbing member was diffused and sufficiently solidified, and then the non-water-absorbing member was removed to obtain a green. It took about 4 hours from the start of molding until the green completely solidified.

When the green thus obtained was cut and the inside was observed, no shrinkage cavities and the like were found. Further, the composition of each section shown in FIG. 6 was analyzed using fluorescent X-rays, and the mode diameter, bulk density, true density and porosity of each section shown in FIG. 7 were examined. The results are shown in Tables 2 and 3.

A rotor obtained by sintering the above green at 1800 ° C. for 2 hours was cut, and the true density and three-point bending strength of each section shown in FIG. 7 were examined, and an average value was calculated. The Weibull coefficient of the obtained rotor was examined. The results are shown in Table 4 together with the target values.

Example 3 2.5% by weight of Y ₂ O ₃ fine powder having an average particle diameter of 5 to 10 μm and Al ₂ O having an average diameter of 3 to 5 μm and an average fiber length of 300 to 600 μm
₃ 1.0% by weight of fiber and the rest of the average particle size 0.4-0.5 μm α
42 parts by weight of water was added to 100 parts by weight of a ceramic mixture containing —Si ₃ N ₄ fine powder, and mixed by a ball mill for 40 hours to obtain a slip having a viscosity of 0.5 p.

The obtained slip was poured into the cavity of the same slip cast molding apparatus as in Example 1 and 4 kg / c
Pressure molding was performed at a pressure of m ² for 240 minutes. The relationship between the inking time and the inking thickness at that time is shown in the graph of FIG. Also,
Table 1 shows the thickness constants of the thickness calculated from the relationship between the thickness of the thickness and the thickness of the thickness.

Thereafter, the parts other than the non-water-absorbing member were released, and
After left for 60 minutes, the water remaining in the portion surrounded by the non-water-absorbing member was diffused and sufficiently solidified, and then the non-water-absorbing member was removed to obtain a green. It took about 4 hours from the start of molding until the green completely solidified.

When the green thus obtained was cut and the inside was observed, no shrinkage cavities and the like were found. Further, the composition of each section shown in FIG. 6 was analyzed using fluorescent X-rays, and the mode diameter, bulk density, true density and porosity of each section shown in FIG. 7 were examined. The results are shown in Tables 2 and 3.

The rotor obtained by sintering the above green at 1800 ° C. for 2 hours was cut, and the true density and three-point bending strength of each section shown in FIG. 7 were examined, and the average value was calculated. The Weibull coefficient of the obtained rotor was examined. The results are shown in Table 4 together with the target values.

Comparative Example 1 2.5% by weight of Y ₂ O ₃ fine powder having an average particle size of 5 to 10 μm, and Al ₂ O having an average diameter of 3 to 5 μm and an average fiber length of 300 to 600 μm.
₃ 1.0% by weight of fiber and the rest of the average particle size 0.4-0.5 μm α
42 parts by weight of water was added to 100 parts by weight of a ceramic mixture containing —Si ₃ N ₄ powder and mixed by a ball mill for 40 hours to obtain a slip having a viscosity of 0.4 p.

The obtained slip was poured into the cavity of a slip cast molding apparatus similar to that in Example 1, and the pressure was maintained at normal pressure.
Molded for 180 minutes. The relationship between the inking time and the inking thickness at that time is shown in the graph of FIG. In addition, Table 1 shows the inking rate constant calculated from the relationship between the inking time and the inking thickness.

Thereafter, the parts other than the non-water-absorbing member were released, and
After leaving for 17 hours, moisture remaining in the portion surrounded by the non-water-absorbing member was diffused and sufficiently solidified, and then the non-water-absorbing member was removed to obtain a green. It took about 20 hours from the start of molding until the green completely solidified.

When the green thus obtained was cut and the inside was observed, no shrinkage cavities and the like were found. Further, the composition of each section shown in FIG. 6 was analyzed using fluorescent X-rays, and the mode diameter, bulk density, true density and porosity of each section shown in FIG. 7 were examined. The results are shown in Tables 2 and 3.

The rotor obtained by sintering the above green at 1800 ° C. for 2 hours was cut, the true density and three-point bending strength of each section shown in FIG. 7 were examined, and the average value was calculated. The Weibull coefficient of the obtained rotor was examined. The results are shown in Table 4 together with the target values.

Comparative Example 2 2.5% by weight of Y ₂ O ₃ fine powder having an average particle size of 5 to 10 μm, and Al ₂ O having an average diameter of 3 to 5 μm and an average fiber length of 300 to 600 μm.
₃ 1.0% by weight of fiber and the rest of the average particle size 0.4-0.5 μm α
42 parts by weight of water was added to 100 parts by weight of a ceramic mixture composed of —Si ₃ N ₄ powder and mixed by a ball mill for 40 hours to obtain a slip having a viscosity of 0.5 p.

The obtained slip was poured into the cavity of a slip cast molding apparatus similar to that of Example 1, and at normal pressure.
Molded for 180 minutes. The relationship between the inking time and the inking thickness at that time is shown in the graph of FIG. In addition, Table 1 shows the inking rate constant calculated from the relationship between the inking time and the inking thickness.

Thereafter, the parts other than the non-water-absorbing member were released, and
After leaving for 17 hours, moisture remaining in the portion surrounded by the non-water-absorbing member was diffused and sufficiently solidified, and then the non-water-absorbing member was removed to obtain a green. It took about 20 hours from the start of molding until the green completely solidified.

When the green thus obtained was cut and the inside was observed, no shrinkage cavities and the like were found. Further, the composition of each section shown in FIG. 6 was analyzed using fluorescent X-rays, and the mode diameter, bulk density, true density and porosity of each section shown in FIG. 7 were examined. The results are shown in Tables 2 and 3.

The rotor obtained by sintering the above green at 1800 ° C. for 2 hours was cut, the true density and three-point bending strength of each section shown in FIG. 7 were examined, and the average value was calculated. The Weibull coefficient of the obtained rotor was examined. The results are shown in Table 4 together with the target values.

Comparative Example 3 2.5% by weight of Y ₂ O ₃ fine powder having an average particle size of 5 to 10 μm and Al ₂ O having an average diameter of 3 to 5 μm and an average fiber length of 300 to 600 μm.
₃ 1.0% by weight of fiber and the rest of the average particle size 0.4-0.5 μm α
42 parts by weight of water was added to 100 parts by weight of a ceramic mixture composed of —Si ₃ N ₄ powder and mixed by a ball mill for 40 hours to obtain a slip having a viscosity of 0.5 p.

The obtained slip was poured into the cavity of the same slip cast molding apparatus as in Example 1 to give a void.
Pressure reduction molding was performed for 180 minutes while reducing the pressure inside 71 to -76 cmHg. The relationship between the inking time and the inking thickness at that time is shown in the graph of FIG. In addition, Table 1 shows the inking rate constant calculated from the relationship between the inking time and the inking thickness.

Thereafter, the parts other than the non-water-absorbing member were released, and
After leaving for 17 hours, moisture remaining in the portion surrounded by the non-water-absorbing member was diffused and sufficiently solidified, and then the non-water-absorbing member was removed to obtain a green. It took about 20 hours from the start of molding until the green completely solidified.

When the green thus obtained was cut and the inside was observed, no shrinkage cavities and the like were observed. Further, the composition of each section shown in FIG. 6 was analyzed using fluorescent X-rays, and the mode diameter, bulk density, true density and porosity of each section shown in FIG. 7 were examined. The results are shown in Tables 2 and 3.

The rotor obtained by sintering the above green at 1800 ° C. for 2 hours was cut, the true density and three-point bending strength of each section shown in FIG. 7 were examined, and the average value was calculated. The Weibull coefficient of the obtained rotor was examined. The results are shown in Table 4 together with the target values.

[0059]

Table 2 Example 1 Example 2 Example 3 Y ₂ O ₃ Al ₂ O ₃ Y ₂ O ₃ Al ₂ O ₃ Y ₂ O ₃ Al ₂ O ₃ site ( % by weight ) ( % by weight ) ( % by weight ) ) ( Wt% ) ( wt% ) ( wt% ) a 2.50 0.94 2.40 0.93 2.45 0.93 b 2.45 0.95 2.35 0.94 2.45 0.94 c 2.50 0.95 2.40 0.95 2.50 0.95 d 2.40 0.95 2.40 0.93 2.50 0.95 e 2.40 0.93 2.35 0.94 2.40 0.93 f 2.40 0.93 2.40 0.92 2.45 0.93

Table 2 (continued) Comparative Example 1 Comparative Example 2 Comparative Example 3 Y ₂ O ₃ Al ₂ O ₃ Y ₂ O ₃ Al ₂ O ₃ Y ₂ O ₃ Al ₂ O ₃ site ( % by weight ) ( % by weight ) ( Wt% ) ( wt% ) ( wt% ) ( wt% ) a 2.50 1.06 2.45 1.07 2.50 1.03 b 2.50 1.08 2.45 1.05 2.45 1.02 c 2.40 0.98 2.45 1.00 2.50 1.02 d 2.40 0.92 2.50 0.98 2.50 0.94 e 2.35 0.86 2.40 0.85 2.40 0.84 f 2.40 0.88 2.40 0.87 2.40 0.90

Table 3 Example 1 Example 2 Example 3 Comparative Example 1 Mode diameter (μm) Upper 0.066 0.077 0.072 0.097 Middle 0.069 0.074 0.074 0.097 Lower 0.072 0.076 0.080 0.105 Wing 0.080 0.082 0.083 0.106 Bulk density (g / cc) Upper 2.02 1.91 2.02 1.77 Middle 1.98 1.91 1.96 1.76 Lower 1.95 1.89 1.96 1.74 Wing 1.88 1.87 1.87 1.73 True density (g / cc) Upper 3.15 3.12 3.18 3.10 Middle 3.20 3.18 3.18 3.15 Lower 3.13 3.14 3.12 3.11 Wing 3.10 3.11 3.11 3.11 Pore Rate (%) Upper part 37.2 38.7 38.0 42.9 Central part 37.9 40.1 38.8 44.1 Lower part 37.3 39.6 38.6 43.9 Feather part 38.5 40.1 39.5 43.5

[0063]

Table 4 Characteristic target values Example 1 Example 2 Example 3 True density (g / cc) 3.20 3.20 3.21 3.21 Three-point bending strength (MPa) 588.0 638.4 642.9 660.2 Weibull coefficient 15.0 17.6 18.2 17.2

Table 4 (continued) Characteristics Comparative example 1 Comparative example 2 Comparative example 3 True density (g / cc) 3.21 3.21 3.21 Three-point bending strength (MPa) 627.7 622.7 617.8 Weibull coefficient 13.7 14.6 14.5

As is clear from FIG. 5 and Table 1, the slip inking rate by pressure reduction molding and pressure forming is higher than the slip infiltration rate by normal pressure forming and pressure reduction forming. Further, as is clear from Tables 2 and 3, the pressure-reduced pressure-molded and pressure-molded molded bodies have better dispersibility of fibrous ceramics than the normal-pressure molded and pressure-molded molded bodies. Moreover, the porosity is small and the density is high. Further, as is clear from Table 4, the pressure-reduced pressure-molded product and the pressure-molded product have a higher strength and a smaller variation in strength than the normal-pressure molded product and the pressure-reduced molding product.

[0067]

As described in detail above, according to the slip cast molding method of the present invention, a slip added with a fibrous ceramic is injected into a cavity and the slip is molded while being pressurized, so that there is no compositional unevenness. A ceramic molded body having high strength can be obtained in a short time.

The slip cast molding method of the present invention is particularly suitable for producing a large-sized thick-walled or complex-shaped ceramic molded body.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a slip cast molding apparatus capable of performing a slip cast molding method of the present invention.

FIG. 2 is a cross-sectional view showing an example of a state in which slip is supplied to a cavity of the slip cast molding apparatus in FIG.

[3] and the addition amount of Al ₂ O ₃ fibers is a graph showing the relationship between the Al ₂ O ₃ elongation of the molded body with added fiber.

[Figure 4] and the addition amount of Al ₂ O ₃ fibers is a graph showing the relationship between the three-point bending strength of the molded body obtained by adding the Al ₂ O ₃ fibers.

FIG. 5 is a graph showing the relationship between the inking time and the square of the inking thickness in Examples and Comparative Examples.

FIG. 6 is a diagram showing one pattern of a section in a green cross section obtained in Examples and Comparative Examples.

FIG. 7 is a diagram showing another pattern of sections in a cross section of the molded body obtained in Examples and Comparative Examples.

[Explanation of symbols]

1 ... Mold 1a ・ ・ ・ Upper mold 1b ... Medium 1c ... Lower mold 10 ... Non-water absorbent material 2 ... closed box 2a ... Upper cylindrical member 2b ... Upper annular member 2c, 2d, 2e ... Side cylindrical member 2f: bottom member 2g ... groove 3… Slip supply pipe 31, 41, 51, 81 ... Valve 4 ... Pressurized air supply tube 5 ... Suction tube 6 ... Cavity 7 ... slip 8 ... Slip replenishment tube 82 ... Slip replenishment tank 9 ... Peep window

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Koizumi 1-4-1 Chuo, Wako-shi, Saitama, Ltd. Honda R & D Co., Ltd. (72) Inventor Taizo Kitamura 4-1-1 Chuo, Wako, Saitama (56) Reference JP 62-196129 (JP, A) JP 62-216969 (JP, A) JP 2-9777 (JP, A) JP 63-59527 ( (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 41/16 B29C 41/36 C04B 35/622

Claims (2)

(57) [Claims] 1. A ceramic in which some of the components are fibrous
After injecting the slip into the mold cavity,
Pressurizes the cup, so that the fibrous ceramic is well dispersed.
Slip cast molding method that solidifies in the left state
And a ceramic mold having no shrinkage cavities is obtained by using a mold having a non-water-absorbing member that delays the inking of slips in the upper region of the cavity. 2. The ceramic slip cast molding method according to claim 1, wherein the mold is housed in a closed box, and the water in the slip is sucked by depressurizing the closed box. how to.