JPH0442164B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a firing molding method for refractory materials such as various ceramics and carbon materials using a mold by vibration molding method or impact load molding method. The present invention relates to a method for obtaining a long molded article having a length of more than 50 cm and having no surface peeling defects. [Conventional technology] Length 20 to 30 mm used as protection tube, crucible, etc.
Methods for molding fired products such as relatively short ceramic cylinders, cylinders, polygonal tubes, and polygonal pillars into shapes close to the final shape include slurry casting,
Examples include extrusion molding, vibration molding, and tamping molding. In addition, in Japanese Utility Model Publication No. 55-42901, when fresh concrete is poured into a mold and hardened to obtain a concrete molded body, a sheet made of paper that has deaerating properties and does not allow concrete components to pass through is poured. A technique is disclosed in which concrete is placed between the upper surface of fresh concrete and formwork. In addition, Japanese Patent Application Laid-Open No. 57-133012 discloses that when obtaining a cement mortar molded body by pouring cement mortar into a formwork and hardening it, a filter is used to dehydrate excess water in the mortar, and the mortar facing the filter is used to remove excess water from the mortar. A technique has been disclosed in which a mold release material having filtration performance and excellent flexibility and bendability is interposed between the filter and the filter, and the filter is mortared while applying vibration pressure. [Problem to be solved by the invention] By the way, since the slurry casting method uses a large amount of water, the raw material powder tends to be distributed in the vertical direction based on the viscosity or specific gravity of the raw material powder, and it is difficult to obtain a molded product having a uniform density in the vertical direction. The disadvantage is that the longer the length is, the more uneven the surface becomes. Moreover, even if a load is applied from above and the molding is performed, the raw material powder becomes fluidized and high density cannot be expected. In order to improve this, if pressure molding is performed while slowing water using a filter, a certain degree of high density can be expected, but it takes a considerable amount of time to achieve high density, which impairs productivity and makes practical molding difficult. It's not about sex. In any case, with the slurry casting method, it is difficult to obtain a uniform and high-density elongated molded body due to the filling density. Extrusion molding can only be applied to continuous products with the same cross-sectional shape;
It cannot be applied to tapered or thick-walled structures. Furthermore, since the content of water, binder, additives, etc. is high, pores tend to remain inside the molded product, making it difficult to obtain a high-density molded product. The vibration molding method and the tamping molding method usually use split wooden molds or metal molds, but they have the following problems. (1) As the raw materials are tightly packed, water and binder move near the boundary between the molded product and the mold and stick or solidify, resulting in poor mold releasability. Even if this is done, some of the raw material will peel off, stick to the formwork, and be carried away.
Peeling defects are likely to occur on the surface of the molded product. (2) Conventionally commonly used molding frames are made of metal or hard wood and do not have air permeability, so gases such as air and water vapor in the voids of raw material particles As it progresses, it collects and remains inside the molded body or at the boundary between the molded body and the mold, and tends to cause defects such as voids and delamination. Therefore, there was a certain limit to the degree of compactness that a molded body could reach. In other words, if the packing density of a part of the molded body reaches this limit point, even if there are other low-packing-density parts remaining, if the molding operation is not finished at that point, overfilling will occur and the above-mentioned defects will occur. In particular, in the case of large molded products such as long products, there was a problem that the packing density became non-uniform. (3) Excessive compaction filling using conventional wooden frames or molds may cause the molded product to stick to the mold, making demolding difficult or causing energy to remain inside the molded product. This accumulates as stress, causing problems such as local expansion failure of the molded body during demolding or destruction during drying or firing. Also, Publication No. 55-42901 and Japanese Unexamined Patent Publication No.
The above-mentioned method disclosed in Publication No. 57-133012 attempts to cause cement to contain a large amount of water and cause a hydration reaction to harden. If a ceramic or carbon material molded body is molded using this method, it is impossible to obtain a uniform, high-density elongated molded body as in the slurry casting method described above. [Means for Solving the Problems] The present inventors have developed a mold that has good mold releasability and no surface peeling defects by using a vibration molding method or an impact load molding method.
As a result of much research in order to obtain a long molded body for fired ceramics or carbon materials with a high and uniform packing density, we found that after the raw material powder was molded, excessive accumulation occurred inside the molded body. As a result of further research based on the idea that if the residual stress is appropriately released, the phenomenon of cracking or destruction occurring in that part due to the part restoring and expanding after forming can be solved. The object of the present invention is to provide a method for forming a fired body of elongated ceramic or carbon material having a high and uniform packing density. That is, the present invention is a method of filling a mold with ceramic or carbon material raw material powder to form a long molded body using a vibration molding method or an impact load molding method, and then curing, drying, and firing the raw material powder. The moisture content of the flour is 3 to 100 parts by weight of the raw material flour.
20 parts by weight, and the molding frame is a combination of a mold body made of a soft material having water absorption, air permeability, and plastic deformability, and a support having high strength, and The thickness of the form body made of the material is 2 mm to 30 mm, and the plastic deformability of the form body made of the soft material is at point A in Figure 1 of the attached surface.
(P100Kg/cm ² , δ0.01%), Point B (P100Kg/cm ² , δ0.
1
%), point C (1000Kg/cm ² , δ1.0%), point D (P1000
Kg/cm ² , δ0.1%) is a method for forming a fired body of ceramics or carbon material. Here, P is the instantaneous impact pressure during molding,
δ represents the amount of deformation of the frame body deformed by the molded body formed by the impact pressure upon drying or water absorption. [Function] A form body made of a soft material is used in combination with a high-strength wooden or metal frame body that supports the form body in the portion that comes into contact with the raw material excavated soil. In this case, the high-strength support also includes a core for forming a cylinder. The form body made of a soft material must have appropriate water absorption (including oil absorption), air permeability, and plastic deformability as described below. Water absorption rate As molding progresses, the mold body itself absorbs the water containing the binder that moves to the interface between the molded body and the mold in contact with it, keeping the surface of the molded body in a low-moisture state. dripping Water absorption rate or oil absorption rate is 1%
It is necessary that the amount is at least 5%, and preferably at least 5%. If it is less than 1%, the mold releasability is poor;
It becomes difficult to obtain a healthy molded product without surface defects. Air permeability In order to increase the packing density of the molded body, gaseous components such as air, water vapor, and gas generated by vaporization of the binder existing in the spaces between the particles of the raw clay are molded through a soft material formwork. Excreting it from the body is effective. The air permeability must be 0.1 millidarcy or more, preferably 1
It is more than millidarcy. If it is less than 0.1 millidarcy, coarse pores may remain inside or near the surface of the molded product, or layers may easily peel off.
Furthermore, 1 darcy means 1 darcy per second per 1 cubic centimeter of volume at a pressure difference of 1 kg/ ^cm2 .
This means that milliliters of air can pass through it. Plastic deformability Energy (internal stress) is accumulated inside the molded body as the packing density of the molded body increases, and expansion occurs when the restraining force is released by demolding the mold. In other words, if the molded body is completely constrained only by a high-strength, high-steel mold without using a mold body made of a soft material as in the present invention and is packed excessively tightly, large expansion (elasticity) occurs upon demolding. (referred to as a restoring effect) occurs, and the molded object is destroyed. However, in the present invention, as the molded body becomes more closely packed and the energy accumulated inside the molded body becomes excessive, the mold itself that restrains the molded body deforms minutely and absorbs this excess energy. Since it is opened appropriately, it is possible to perform high-density molding without leaving a low-filling-density portion as in the conventional method, and it is possible to perform a more densely-packed operation. Generally, the stress-plastic deformability of a material is given by a stress-strain curve, but since it is difficult to define the appropriate range of the present invention for such two-dimensional properties, we have used the elastic modulus as a guideline instead. When expressed as tensile strength, it is preferable that the following values are satisfied.

[Table] Regarding the strength during water absorption, it is necessary that the amount of deformation that deforms in response to the maximum pressure applied from the molded object to the form body during molding does not exceed an appropriate amount, and the relationship between stress and amount of deformation must be determined. There is an appropriate range for two-dimensional correlation. In other words, in the vibration molding method or the impact load molding method according to the present invention, the raw material and the formwork are generally 100Kg/cm ² to 1000Kg/cm ^{2 .}
An instantaneous impact pressure is applied in the range of The amount of deformation in the thickness direction is preferably in the range of 0.01% to 1%, and the appropriate range of the instantaneous impact pressure and the amount of deformation of the form body is shown in FIG. That is, point A
(P100Kg/cm ² , δ0.01%), Point B (P100Kg/cm ² , δ0.
1
%), point C (P100Kg/cm ² , δ1.0%), point D (P1000
Kg/cm ² , δ0.1%). Here, P represents the instantaneous impact pressure during molding, and δ represents the amount of deformation during drying or water absorption of the frame body deformed by the molded body formed by the impact pressure. This amount of deformation can be obtained by measuring the thickness of the mold body before molding and the thickness of the mold body after molding and curing. In other words, the dimensional accuracy and dimensions of the molded body should be reduced by 1% or more in thickness, that is, become thinner, because its strength during water absorption is low and the amount of deformation of the mold body that deforms due to the pressure applied to the raw material powder during molding is reduced by 1% or more in thickness. The reproducibility deteriorates, and the shear force generated between the molded body and the mold body during molding causes partial damage to the mold body, which also deteriorates the surface finish of the molded body itself. In addition, the strength when dry is high and the amount of deformation is 0.01%.
A mold body of less than 100 mm has a low water absorption ability, and it is difficult to appropriately release the stress accumulated inside the molded body due to the filling of the raw material slough, and the above-mentioned defects are likely to occur. In the present invention, as a formwork made of a soft material that is in contact with the molded body during molding, if shear failure does not occur even if the strength at the time of water absorption is low, excessive deformation such as buckling will be prevented by contacting the formwork body. This can be avoided by using high strength supports. Further, when a relatively thick soft material is used and the frame body has high strength, a support body that supports only a portion of the frame body, for example, the lower part, may be used. A molded object formed using a form body with such characteristics will expand and deform locally while being restrained by the form body, but if the characteristics of the form body are within the above-mentioned appropriate range, the amount of deformation will be small. Furthermore, this is not a disadvantage since it does not become a defect that affects the performance of the fired product. Examples of soft materials that have the above-mentioned characteristics and can be put to practical use include kraft paper, rigid polyurethane sheets, rigid polyethylene sheets, and hard wood. When using these as a formwork, they may be laminated in advance into the desired shape using an appropriate adhesive and molded, or the inner surface of a formwork made of high-strength material such as metal, wood, or synthetic resin may be used. Alternatively, it may be used by pasting it on the outer surface. In this case, the thickness of the hard material and the magnitude of the instantaneous impact pressure applied to the powder may be appropriately selected depending on the shape of the ceramic or refractory material to be molded.
For example, when the outer diameter of the cylindrical molded body is 50 to 600 mm, 2
mm to 30 mm, and if the thickness is less than 2 mm, not only will the amount of deformation described above not be obtained, but it will not be able to withstand the instantaneous impact pressure and will deform or collapse, impairing the smoothness of the surface of the molded product. saturate.
Also, depending on the shape of the required molded object, cylinder, cube, etc.
It is formed into a polygonal, medium or irregular column shape, and when it is made into a cylindrical shape, it is used by forming an outer frame body and an inner frame body. The molding method used in the present invention is generally a vibration molding method or an impact pressure molding method using a pneumatic impactor (rammer). The vibration conditions in the vibration molding method depend on the shape of the molded object,
The size and total weight including the molding frame are selected appropriately, but for example, when molding a cylindrical body with an outer diameter of 80 mm, an inner diameter of 55 mm, and a flow rate of 1200 mm, the upper part of the mold filled with raw material slough is After loading the formwork with a 5-10 kg load cone and placing it on a vibration table adjusted to minimize lateral vibration, vibration molding is usually carried out for 5-30 minutes at an amplitude of 2-6 mm. It is. In tamping molding using a pneumatic impactor, a load drill is not used, and the end of the pneumatic impactor is inserted into the hollow part of the formwork while sequentially filling the hollow parts of the outer and inner formwork with raw material. Apply impact pressure. At this time, the pneumatic impactor may be operated manually,
It may also be operated automatically by mechanical operation. In the present invention, during the curing and drying stage of the molded body after the completion of molding, moisture and gaseous molecules in the molded body and gaseous molecules are slowly transferred into the mold body made of a soft material having water absorption and air permeability. The residual stress that has accumulated excessively is released. After molding, the molded product is usually cured at room temperature for 24 hours or more with the soft material mold body in place, and after it has developed sufficient shape retention strength, the mold body is removed, and then placed in a dryer. Temperature 30~
It is dried at 150° C., preferably 40 to 120° C., for 24 hours or more to completely remove moisture and complete hardening of the binder, and then fired at a high temperature. Note that the soft formwork body does not necessarily have to be completely removed; it may be removed after curing and drying while fixed to the molded body, and even if the baking process is carried out, there will be no problem even if it is destroyed by fire. do not have. As an embodiment of the method of the present invention, FIG. 2 shows a case in which a ceramic cylinder is molded. That is, for metal, a paper outer frame (form) 2 having appropriate water absorption, air permeability, and plastic deformation strength is installed inside a wooden outer frame (support) 1; On the outer periphery of the core body (support body) 3 is a paper inner frame body (form body) 4 which also has water absorbency, air permeability, and plastic deformation strength.
These are covered with a metal or wooden pedestal 5.
It is assembled and installed on the vibration table 6, and the space between the paper outer frame body (form body) 2 and the paper inner frame body (form frame body) 4 is
A ceramic raw material scoop is filled in the chamber, a metal load cone 7 is inserted from the top and vibration is applied, and after a predetermined period of time, the molded body 8 is placed into a paper outer frame (form body) 2 and a paper inner frame body. Core body (support body) 3 with (formwork body) 4 attached
After removing the core body (support body) 3 from the mold outer frame (support body) 1, the core body (support body) 3 is pulled out. Next, the molded body 8 is sufficiently cured and dried together with the paper outer frame (mold) 2 and the paper inner frame (mold) 4 to develop shape-retaining strength, and then the paper outer frame ( Except for the mold body (form body) 2 and paper inner frame body (form body) 4, the molded product is sufficiently dried to obtain a sound molded product. The raw material powder that can be used as raw material powder in the method of the present invention includes commonly used ceramic powders such as alumina, magnesia, zirconia, silica powder, china clay, kibushi clay, silicon carbide, silicon nitride, etc. There are carbonaceous powders such as graphite powder, coke powder, carbon powder, pitch powder, etc., and metal powders such as silicon powder. 3 to 20 parts by weight, preferably 5 to 15 parts by weight of water, an organic binder such as methyl cellulose, polyvinyl alcohol, polyacrylic acid ester, phenolic resin, per 100 parts by weight of a single substance or a mixture of two or more of these. , 0.05 to 5 parts by weight, preferably 0.5 to 3 parts by weight, of heat-treated tar, etc., and further 0.05 to 5 parts by weight of glycerin, fux emulsion, alginate, etc. as additives, and a mixture thereof is used. . If the water content is less than 3 parts by weight, the packing density of the powder will be low, if it is more than 20 parts by weight, the powder will easily get caught in the middle of the mold powder during molding, and if the water content is even higher, it will fluidize and fill. Density does not increase. In addition, water is dehydrated in the drying process, and pores are formed in the dehydrated portions, making it impossible to obtain a uniform molded product with a high packing density. Example 1 30 parts by weight of metal silicon powder with a purity of 98.5% or more and a particle size of 74 μm or less was added to 70 parts by weight of silicon carbide with a particle size of 4 mm or less, and further 7.5 parts by weight of a 10% polyvinyl alcohol aqueous solution was added, and the mixture was kneaded in a kneader. The materials were thoroughly mixed to prepare ceramic raw material sludge (water content: 6.8 parts by weight). On the other hand, with the configuration shown in FIG. 2, the metal pedestal 5 is loaded on the vibration table 6, and the inner diameter
95mm, length 1500mm metal outer frame (support) 1, water absorption rate 35%, air permeability 8mm Darcy, tensile strength at 9% water absorption 240Kg/cm ² Paper tube base paper, outer diameter 90mm, inner diameter 80
mm (pressure: 5 mm), paper outer frame (form body) 2 laminated and molded to a length of 1500 mm (deformation amount when absorbing water: 0.6%), an outer diameter of 55 mm, an inner diameter of 50 mm, using the same paper tube base paper, length
Paper inner frame body (form body) laminated to 1500 mm 4,
A metal core (support) 3 having a diameter of 48 mm and a length of 1500 mm was assembled. Next, the empty space between the paper outer frame body (form body) 2 and the paper inner frame body (form body) 4 of the mold is filled with the ceramic raw material shavings, and the outer diameter is 79 mm from the top. Inner diameter 59
A metal load cone 7 with a length of 300 mm and a length of 300 mm was inserted, and vibration forming was performed at an amplitude of 2 to 5 mm for 30 minutes. The instantaneous impact pressure at this time was 600Kg/cm ² . Next, the molded body 8 is placed on a metal base 5, a metal outer frame (support) 1, and a metal core (support) together with a paper outer frame (form) 2 and a paper inner frame (form) 4. After removing the paper body (form body) 3 and air-drying it at room temperature for 24 hours, the paper outer frame body (form body) 2 and the paper inner frame body (form body) 4 were removed and dried at a maximum temperature of 105° C. for 24 hours. The cylindrical molded body obtained after drying has an outer diameter of 80 mm, an inner diameter of 55 mm, and a length.
It was formed to 120mm. The results obtained are shown in Table 1. Example 2 70 parts by weight of fused alumina with a particle size of 120 mesh or less and 30 parts by weight of alumina with an average particle size of 80 μm were added with 10 parts by weight of silica sol (water content 7 parts by weight) with a solid content concentration of 30% and heated in a kneader. The ceramic raw material was prepared by mixing thoroughly. On the other hand, there is an inner surface of a hard wooden outer frame (support body) with an outer surface of 200 mm x 200 mm, an inner diameter of 125 mm, and a height of 1000 mm, which has a two-part structure, and a hard wooden core body (support body) with a diameter of 75 mm and a height of 1000 mm. ) is a rigid polyurethane foam sheet with a water absorption rate of 22%, air permeability of 1 mm Darcy, tensile strength of 5 Kg/ ^cm2 , and thickness of 2.5 mm (deformation when water is absorbed: 0.3%).
are assembled as a frame for forming a cylindrical body, and the tip of an impact pressurizer (rammer) using air pressure is filled with the above-mentioned ceramic raw material sludge into the hollow space between the vertical frame and the core body. was inserted into the cavity to perform pressure filling. The instantaneous impact pressure at this time is 500
It was Kg/ ^cm2 . Next, after curing and drying at room temperature for 24 hours, the molded body was removed from the outer frame and core, and dried at a maximum temperature of 105°C for 24 hours. The results obtained are shown in Table 1. Example 3 70 parts by weight of artificial graphite powder with a particle size of 8 mm or less,
Add 5 parts by weight of water to 30 parts by weight of pitch coke powder with a particle size of 74 μm or less and 9 parts by weight of high softening point pitch powder with a particle size of 74 μm or less, mix thoroughly in a pressure kneader, and prepare carbonaceous raw material. It was adjusted. On the other hand, the inner surface of a metal outer cylinder (support body) with an outer diameter of 545 mm, an inner diameter of 505 mm, and a length of 1500 mm, and an outer diameter of 395 mm and an inner diameter of 355 mm.
Manufactured by laminating 2.5 mm thick kraft paper with a water absorption rate of 90%, air permeability of 40 mm Darcy, and tensile strength of 550 Kg/cm ² at 9% water absorption on the outer surface of a metal inner tube (supporting body) with a length of 1500 mm. sheet (deformation amount during water absorption: 0.2%)
were assembled as a cylindrical mold by gluing them together, and the carbonaceous raw material was inserted into the cavity at the tip of the pneumatic impact pressurizer while stirring the carbonaceous raw material into the cavity between the outer cylinder and the inner cylinder. Filling molding was performed. The instantaneous impact pressure at this time was 300Kg/cm ² . The results obtained are shown in Table 1. Comparative Example 1 A metal core with a diameter of 55 mm and a length of 1500 mm and an inner diameter of 80 mm were assembled on a metal pedestal placed on a vibrating table using the same ceramic raw materials used in Example 1.
Fill the empty space between a metal cylindrical outer frame with a thickness of 3 mm and a length of 1500 mm, insert a metal load cone with an inner diameter of 57 mm, an outer diameter of 78 mm, and a length of 300 mm from the top, and apply an amplitude of 2 to 5 mm.
Then, vibration molding was performed for 30 minutes. A two-part mold was used as the metal outer frame in order to facilitate demolding of the molded body, the outer surface of the core bar, and the outer frame. The results obtained are shown in Table 1. Comparative Example 2 The same raw material as the ceramic raw material used in Example 2 was used, and a hard wooden core and a hard wooden outer frame with the same hollow dimensions as in Example 2 were used. Rammer molding using a pneumatic impactor was performed during direct filling. When close-packing molding was performed until the bulk density reached 2.70 or more, cracks occurred during demolding, and a sound molded product could not be obtained. Reduced pneumatic impact conditions to prevent cracks and adhesion to the frame during demolding (instantaneous impact pressure of 500
Kg/cm ² ) and the results are shown in Table 1. Comparative Example 3 Using the same carbonaceous raw material sludge as in Example 3, and using the same metal inner cylinder and metal outer cylinder as in Example 3, filling the empty spaces of both with the raw material slough, Rammer molding was performed using a pneumatic impactor. When close-packing molding was performed so that the bulk density of the molded product was 1.60 or more, cracks occurred during demolding, making it impossible to obtain a sound molded product. Relaxed tight packing conditions to prevent cracking during demolding (instantaneous impact pressure 300
Kg/cm ² ) and the results are shown in Table 1. Comparative Example 1-1 In Example 1, a 0.5 mm thick formwork was used,
Other molding was carried out under the same conditions as in Example 1. The results obtained are shown in Table 1. Comparative Example 1-2 In Example 1, the amount of deformation upon water absorption was 3%, and the thickness was 5
Molding was carried out under the same conditions as in Example 1 using a mold frame of mm. The results obtained are shown in Table 1. Comparative Example 1-3 In Example 1, the moisture content of the raw material powder was set to 30 parts by weight, and molding was performed under the same conditions as in Example 1.
The results obtained are shown in Table 1.

〔Effect of the invention〕

By using a formwork body with a special characteristic range, the present invention appropriately releases residual stress that has accumulated excessively in some parts, so that the part expands and breaks during demolding, or breaks during drying and firing. This is a molding method that has the effect of making it possible to perform high-density molding without leaving any low-density filling portions, resulting in a molded body for fired bodies having a high and uniform packing density. .

[Brief explanation of drawings]

FIG. 1 is a graph showing the appropriate range of stress deformation of the formwork body. FIG. 2 is a sectional view of an apparatus showing one embodiment of the method of the present invention.

Claims (1)

[Claims] 1 A long molded body is formed by filling a mold with ceramic or carbon material raw material powder by vibration molding method or impact load molding method, and is then cured, dried, and fired, and the water content of the raw material powder is The amount of the raw material powder
For molding, the amount is 3 to 20 parts by weight per 100 parts by weight, and the formwork is made of a soft material having water absorption, air permeability, and plastic deformability in combination with a support having high strength. The thickness of the frame body made of the soft material is 2 mm to 30 mm, and the plastic deformability of the form body made of the soft material is at point A (P100 kg/cm ² , δ0.01
%), point B (P100Kg/cm ² , δ0.1%), point C (P1000Kg/
cm ² , δ1.0%) and point D (P1000Kg/cm ² , δ0.1%). Here, P represents the instantaneous impact pressure during molding, and δ represents the amount of deformation during drying or water absorption of the frame body deformed by the molded body formed by the impact pressure.