EP0756922A1 - Verfahren zum Formen von Keramikwerkstoffen - Google Patents

Verfahren zum Formen von Keramikwerkstoffen Download PDF

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Publication number
EP0756922A1
EP0756922A1 EP95111854A EP95111854A EP0756922A1 EP 0756922 A1 EP0756922 A1 EP 0756922A1 EP 95111854 A EP95111854 A EP 95111854A EP 95111854 A EP95111854 A EP 95111854A EP 0756922 A1 EP0756922 A1 EP 0756922A1
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EP
European Patent Office
Prior art keywords
slurry
molding
punch
mold
filter
Prior art date
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Granted
Application number
EP95111854A
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English (en)
French (fr)
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EP0756922B1 (de
Inventor
Tomoyuki c/o Itami Works of Sumimoto Awazu
Yasushi c/o Itami Works of Sumimoto Tsuzuki
Akira c/o Itami Works of Sumimoto Yamakawa
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Sumitomo Electric Industries Ltd
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Sumitomo Electric Industries Ltd
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Priority to EP19950111854 priority Critical patent/EP0756922B1/de
Priority to DE1995626733 priority patent/DE69526733T2/de
Publication of EP0756922A1 publication Critical patent/EP0756922A1/de
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Publication of EP0756922B1 publication Critical patent/EP0756922B1/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B1/00—Producing shaped prefabricated articles from the material
    • B28B1/26—Producing shaped prefabricated articles from the material by slip-casting, i.e. by casting a suspension or dispersion of the material in a liquid-absorbent or porous mould, the liquid being allowed to soak into or pass through the walls of the mould; Moulds therefor ; specially for manufacturing articles starting from a ceramic slip; Moulds therefor
    • B28B1/265—Producing shaped prefabricated articles from the material by slip-casting, i.e. by casting a suspension or dispersion of the material in a liquid-absorbent or porous mould, the liquid being allowed to soak into or pass through the walls of the mould; Moulds therefor ; specially for manufacturing articles starting from a ceramic slip; Moulds therefor pressure being applied on the slip in the filled mould or on the moulded article in the mould, e.g. pneumatically, by compressing slip in a closed mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B1/00—Producing shaped prefabricated articles from the material
    • B28B1/26—Producing shaped prefabricated articles from the material by slip-casting, i.e. by casting a suspension or dispersion of the material in a liquid-absorbent or porous mould, the liquid being allowed to soak into or pass through the walls of the mould; Moulds therefor ; specially for manufacturing articles starting from a ceramic slip; Moulds therefor
    • B28B1/261—Moulds therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B7/00—Moulds; Cores; Mandrels
    • B28B7/40—Moulds; Cores; Mandrels characterised by means for modifying the properties of the moulding material
    • B28B7/46—Moulds; Cores; Mandrels characterised by means for modifying the properties of the moulding material for humidifying or dehumidifying

Definitions

  • This invention relates to a molding process for various ceramic products, particularly to a pressure slipcast molding of ceramic slurry, and a mold used therefor.
  • a mixture consisting of powder and liquid (hereinafter “slurry") is pressurized to discharge the liquid therefrom.
  • slurry a mixture consisting of powder and liquid
  • the resulting molded article has a high geometric stability and the liquid discharge and from the slurry can be made in reduced time.
  • porous molds made from gypsum or plastics have been used for the liquid discharge, (e.g. Japanese Patent Publication No. 2-42321, Japanese Patent Laid-Open Nos. 60-70701, 63-3906 and 61-297103).
  • the molding pressure is, at most only 10 kg/cm 2 when a gypsum mold is used and about 50 kg/cm 2 when a plastics mold is used. If the molding pressure exceeding this upper limit is applied to the porous mold, such high pressure may bring about the breakage of the molds.
  • a filter cloth 9 and a filter paper 10 are, as shown in FIG. 3, set at the frontal face of a metallic mold 3, which has holes of 1 - 3 mm inside diameter for dehydration. And only liquid (water) is discharged from the holes of the mold through the filter.
  • the liquid discharge part consists of the filter cloth 9, filter paper 10 and mold 3 having the holes 4 for dehydration
  • a high molding pressure can be applied.
  • the powder in the slurry enters the holes for dehydration pressing on the filter paper or filter cloth and then it becomes protrusions 11 are formed on the surface of the molded product, corresponding to the holes as shown in FIG. 4. Therefore, an after-treatment is necessary to remove the protrusion from the molded product, thereby resulting in a high production cost.
  • the present invention was made to overcome the above and other problems encountered in the prior art.
  • Another object of the present invention is to provide molds used for carrying out the above-mentioned molding process.
  • the basic idea of this invention is to enable the application of high pressure by using a mold made of a high-strength porous metal or ceramic material in a pressure slipcast molding process of a ceramic slurry.
  • the present invention provides a process for molding a ceramic slurry, in which a mold made wholly or partially of a porous metal or a porous ceramic is used.
  • the present invention also provides a mold made wholly or partially of a porous metal or a porous ceramic, for the purpose of molding ceramic slurry.
  • FIG. 1 is a vertical cross-sectional view showing a casting method employing a casting mold according to an embodiment of the present invention.
  • FIG. 2 is a view similar to FIG. 1, showing a casting method employing a casting mold according to a modification of the present invention.
  • FIG. 3 is a view similar to FIG. 1 employing a conventional casting mold.
  • FIG. 4 is a vertical cross-sectional view showing a cast article obtained using the conventional casting mold.
  • FIG. 5 is a view showing molded article in the form of circular trumpets.
  • FIG. 6 is a vertical cross-sectional view showing a casting method for molded article in FIG. 5.
  • FIG. 7 is a graphical representation showing the relation between pressurizing time and punch position.
  • FIG. 8 is a view illustrating pressurizing steps of the present invention.
  • the basic concept of the present invention consists in that, in pressure slipcast molding of ceramics, a casting mold made of metal or ceramic of a higher strength is employed to enable application of a higher pressure.
  • a pressure not lower than 100 kgf/cm 2 may be developed.
  • a pressure up to 1000 kgf/cm 2 is also possible depending on the mold's design.
  • Ceramics materials are not limited to Al 2 O 3 ceramics, Si 3 N 4 ceramics, BN ceramics and so on.
  • porous metals and ceramics it is possible to polish the surface of porous metals and ceramics, to decrease their surface roughness, and to make it a mirror plane in some cases.
  • molded ceramic articles can be easily taken out of the mold and also be prevented from breaking.
  • the surface appearance of the molded ceramic articles become excellent.
  • ceramics for porous materials ceramics have a high chemical resistability against acid, alkali and so on. Ceramics are neither corroded nor rusted and have sufficient durability. And they are excellent in strength and toughness, compared with other materials; therefore, they do not become fatigued and have sufficient durability mechanically, too.
  • diameters of pores in the porous materials which are components of a mold the wholly or partially, should be more than 0.1 ⁇ m so that dehydration and molding can be carried out in industrially practical time. If diameters of the pores are less than 0.1 ⁇ m, in case of using water for liquid of the slurry, the surface tension becomes higher, keeps the liquid from flowing into pores of porous materials, and makes it difficult to discharge the liquid in the slurry through pores of porous materials.
  • powders in the pressurized slurry tend to undergo cohesion to form agglomerates (hereinafter referred to as "secondary particles").
  • the maximum diameter of the pores is twenty times as high as the diameter of the secondary particles of powders in the slurry and it can prevent the powders from flowing.
  • filter paper and/or filter cloth on the surface of porous metal or ceramics facing the slurry. Even if diameters of pores on the surface of porous metal or ceramics are so large as to let the powders in the slurry enter the pores, the filter prevents powders from entering them and makes release easier. And if the surface of porous metal or ceramics is rough, the filter does not bring about an anchor effect and makes release smooth. Because the filter, made of paper or cloth has high flexibility, therefore it is possible to release the filter from molded ceramic articles slowly without producing chips. Protrusions on the surface of ceramics, in the conventional method as shown in FIG. 3, do not enter pores of porous metal or ceramics through the filter and then molded ceramic articles have an excellent surface.
  • the average diameter of pores in the filter paper or filter cloth should be more than 0.1 ⁇ m and less than twenty times as large as the diameter of the secondary particles in the slurry.
  • the average diameter of pores needs to be more than 0.1 ⁇ m. If the average diameter is larger than twenty times as large as the average diameter of the secondary powder in the slurry, it causes efflux of powder, namely a permeation of the slurry through the filter for the same reason as discussed above.
  • the paper filter may be formed of any material customarily employed for the paper filter, while the cloth filter may be formed of any material, such as synthetic fibers, e.g. polyester, nylon or acrylic fibers, or natural fibers, such as cotton, provided that such material can be woven or knitted to form a cloth.
  • synthetic fibers e.g. polyester, nylon or acrylic fibers, or natural fibers, such as cotton, provided that such material can be woven or knitted to form a cloth.
  • the slurry is pressurized by moving a punch to effect mechanical compression and discharge a liquid. Filters are attached to a portion discharging the liquid for preparing a molded article. The liquid in the slurry is passed via the molded article so as to be discharged out of the system. If the pressurization during molding is insufficient, liquid removal from the slurry in the vicinity of the punch is insufficient so that a non-solid portion is left. If the pressurization is excessive, the punch is pushed wastefully and the molded article is mechanically compressed so that the packing density of the powders in the molded article is locally increased in the vicinity of the punch with progress in the mechanical compression of the molded product.
  • FIG. 7 and 8 illustrates a pressurizing step of the present invention.
  • FIG. 7 schematically shows the relation between pressurizing time and punch displacement.
  • FIG. 8 schematically shows the molding state of a slurry at each stage of the pressurizing time.
  • a point at which the packing density of ceramic particles in the slurry becomes uniform in the pressurizing direction, in other words, a point at which the concentration gradient in the pressurizing direction of ceramic particles in the slurry becomes null, is defined as the state in which all the slurry charged into the cavity has solidified.
  • the pressurizing time which elapses until solidification is defined at T. The above will be understood on comparing the unsolidified stage shown at the third from left to the stage of the solidified slurry shown at the forth from left.
  • pressurization is caused to proceed further continuously for a pre-set time from this stage and is then stopped in order to take out a molded product from the mold.
  • the time control can be achieved by terminating the pressurization within 50% of the pressing time determined from the time at which the slurry in the mold is dehydrated and all slurry turned into a molded article. In other words, pressing of the slurry is completed at a time between T and 1.50T, wherein T is the pressing time necessary to remove sufficient excess liquid from the slurry in the mold to produce a molded mass. If the timing of the end of pressurization exceeds 50%, density fluctuations can occur and the sintered product is deteriorated in dimensional stability. In the worst case, cracks are produced.
  • the molded product is abnormally compressed, as that it becomes intimately affixed to the punch or a solvent removing portion resulting in lowered mold release properties and crack exfoliation.
  • the molded article tends to be expanded (springback) when being taken out of the mold, a strong friction operates between the mold and the molded article thus resulting in the mold injuring the molded article or producing cracks.
  • the pressurization and timing is related with the shape of the molded article. That is, the condition is changed depending upon the ratio of the size of the article portion thrust by the punch to the size of the proceeding direction of the punch.
  • This ratio is termed the aspect ratio.
  • the force of friction acting between the molded article and the lateral surface of the mold is as large that uniform pressure can hardly be applied to the entire molded article. If excess pressure is applied to an article under such state, significant non-uniform pressure is produced in the longitudinal direction, such that only a small amount of an excess pressure induces density fluctuations or fracture of molded articles. Thus it becomes necessary to strictly control the pressurization end timing.
  • the total pressurizing time is up to 1.50 times T, that is in a range of from T to 1.5T for the aspect ratio of the molded article of 1 or less, and is up to 1.12 times T, that is in a range of from T to 1.12T for the aspect ratio exceeding 1. If the aspect ratio is within this range, the lowering of molded release properties or damages to the molded article due to friction with the mold may be suppressed by the above-mentioned reason. In addition, the sintered article may be improved in dimensional accuracy or strength.
  • the pressing condition may be implemented by the amount of the punch displacement. That is, the pressurization is terminated within a length the punch is moved distance equal to 17% of the molding length L as measured from a punch position at which excess liquid is removed from the slurry in the mold and the entire slurry has solidified. In other words, punch stroke may go beyond a point at which sufficient excess liquid is removed from the slurry in the mold and the entire slurry has solidified. In other words, punch displacement from a point at which sufficient excess liquid is removed from the slurry in the mold to produce a molded mass is less than 17% of the total molding length L. If the punch is moved for pressurization in excess of 17% of the molding length L the molded article can undergo density fluctuations and, in extreme cases, cracks occur.
  • the molded article is injured due to the lowering of the mold release properties and to friction with the mold.
  • the sintered product may also be severely affected in dimensional accuracy and mechanical strength, such that, if the aspect ratio exceeds 1, poor dimensional accuracy or lowering in mechanical properties, such as three-point bending strength, is produced.
  • the allowable control range of the punch displacement is changed depending upon the range of the aspect ratio. That is, with the aspect ratio of the molded product exceeding 1, any excess solvent is removed from all the slurry in the mold, such that pressurization ceases during the time the punch is moved a distance equal to 4% of the molding length as from the position the molding mass is turned into the molded article. If the punch is moved for pressurization beyond a point corresponding to 4% of the molding length, the molded article undergoes density fluctuations and, in an extreme case, cracking is incurred.
  • the pressure molding of the present system is the pressing technique equivalent to pressure mechanical compression at an extremely high pressure. Since a correspondingly high mechanical compression acts on the liquid removing portion, it is desirable to use a material of high mechanical strength, namely a porous member of metal or ceramics. If a filter such as a filter paper and/or a filter cloth is provided on the front surface of a slurry contacting portion of a porous member, mold release properties are improved and satisfactory molded products are produced without being constrained by the state of the porous member, such as pore size or surface roughness.
  • the pore size of the porous member in contact with the slurry needs to be not more than 20 times the mean particle size of the secondary particles of the powders present in the slurry and not less than 0.1 ⁇ m by reason of the time of liquid removal and mold release properties.
  • the surface roughness of the porous member in contact with the slurry needs to be not more than 0.4 Rz by reason of the mold release properties.
  • the surface roughness of the porous member in contact with the slurry needs to be not more than 0.4 Rz by reason of the mold release properties of the molded article.
  • the pore diameter of the filter paper or filter cloth in contact with the slurry needs to be not less than 0.1 ⁇ m and not more than 20 times the mean particle size of the secondary particles of the powders present in the slurry by reason of mold release properties and the time for solvent removal.
  • the punch is moved within a die or mandrel and the slurry is mechanically compressed as the punch is slid against the inner wall of the die.
  • slurry effluence occurs by reason of the clearance of the sliding portions, such that the slurry falls into shortage and solidification is not completed.
  • a sealant is provided at the sliding portion. O-rings formed of rubber, resin or metal, for example, may be employed as the sealant.
  • the die and the punch are formed of the material which is superior in abrasion resistance and is not susceptible to fatigue due to repeated sliding of the punch relative to the die. That is, with the present molding system, it is advantageous to use a die and a punch exhibiting high mechanical strength capable of withstanding high pressure and high abrasion resistance.
  • a metal material such as cemented carbide or high-speed steel is preferred.
  • the state of the slurry is defined in the system of the present application, it becomes possible to produce a molded product of an intricate shape which cannot be produced with the conventional uniaxial pressurization employing a die and a punch.
  • a product having a shape with the aspect ratio exceeding 3, a trumpet shape with a changing cross-section or a cylindrical shape can be molded.
  • the slurry needs to be flown uniformly into the mold, so that the slurry is preferably of a viscosity not higher than 5000 cps.
  • the volume fraction of powders should in general be 60 vol% or less, depending upon the state and types of the starting powders and the solvent.
  • the powder type, particle size, particle size distribution or solvent type There is no particular limitation to the powder type, particle size, particle size distribution or solvent type.
  • a mixture of powders was made by adding Y 2 O 3 , Al 2 O 3 as assistant agents to Si 3 N 4 powders, having an average diameter of 0.7 ⁇ m, then mixing it in ethylalcohol. Water and binder were added to the mixture. Making use of a nylon ball mill, they were made into a slurry. The powder content of the slurry was set to be 40 vol.%.
  • FIG. 1, 2 show a process for molding.
  • a mold 3 having holes 5 for dehydration and attached to porous material 7, was set in mold 2 and the slurry was injected into it.
  • the slurry was pressurized with a metallic pestle 1 fitted with a porous punch 6 at its terminal end. Water in the slurry 8 was discharged by applying pressure through porous materials 6, 7 and a dehydration exit 4. Molded ceramic articles could be taken out as a result.
  • SUS 316 is a stainless steel according to Japanese Industrial Standard G 4303. Table 1 No. Porous materials Molding pressure (kgf/cm 2 ) Density of molded articles (%) Molding time (sec.) 1 SUS 316 5 49.8 1000 2 SUS 316 20 50.7 250 3 SUS 316 100 61.6 45 4 SUS 316 1000 63.4 12 *5 gypsum 5 48.9 850 *6 gypsum 20 gypsum fractured - *7 resin 5 49.7 800 *8 resin 20 50.8 200 *9 resin 100 resin fractured - * indicates comparisons
  • Si 3 N 4 (90 - 95 wt%) with mean primary particle size of 0.2 ⁇ m and mean secondary particle size of 0.5 ⁇ m, as main component, Y 2 O 3 (mean primary particle size, 0.5 ⁇ m) and Al 2 O 3 (mean primary particle size, 0.3 ⁇ m), as additives, are employed.
  • the starting powders were mixed in a ball mill with distilled water and admixed with a binder and thus a slurry having a volume concentration of 42 vol% of the powders was prepared (the slurry same as the slurry of Example 1).
  • the mean secondary particle size was 0.53 ⁇ m (due to the effect of the additive added to 0.5 ⁇ m of the main component). Using this slurry, a disc 50 mm in diameter and about 6 mm in thickness was molded. In this case, the aspect ratio was 0.12.
  • the punch and the die were formed of cemented carbide and the mold was formed of high-speed steel. Molding was carried out under a high pressure of 300 kgf/cm 2 .
  • the pressurizing conditions were controlled by the molding time or the amount of punch displacement (aspect ratio, not more than 1). With the use of the slurry quantity which will give a molding thickness of 6 mm for molding, the optimum pressurization end timing was set by time control (50% or less of the pressurization time which elapsed since a time point when all the slurry in the mold is dehydrated to produce a molded article) and punch displacement control (17% or less of the molding length as from the position at which all the slurry in the mold is dehydrated to give a molded article). Other molding conditions were also varied in many ways.
  • the relation of mold release properties and the molding state and various conditions are as shown in Table 2.
  • the produced molded article was divided in the cross-section in five equal parts and the density of the molded product was measured to calculate density fluctuations in the molded article from the maximum and minimum values.
  • Al 2 O 3 (mean primary particle size, 0.2 ⁇ m; mean secondary particle size, 0.4 ⁇ m) was used.
  • the starting powders were mixed in a ball mill with distilled water and admixed with a binder to produce a slurry having a volume concentration of the powders of 50 vol%.
  • a plate of SUS with a through-hole having a filter paper and/or a filter cloth ahead of it, was used.
  • the punch and the die were formed of cemented carbide and the mold was formed of high-speed steel. Molding was carried out under a high pressure of 500 kgf/cm.
  • the pressurization during molding was controlled by controlling the molding time or amount of punch displacement (aspect ratio, 1 or high).
  • the quantity of slurry which will give the molding length of 60 mm was used for molding.
  • the optimum pressurization end timing was by time control (within 12% of the pressurizing time which elapsed since the time point when all the slurry in the mold is dehydrated and turned into a molded product) and by punch displacement control (within 4% of the molding length as from the position when all the slurry in the molded is dehydrated and turned into slurry).
  • the slurry was made by mixing together Al 2 O 3 powders having average diameter of 1 ⁇ m, distilled water using a ball mill and admixing with a binder.
  • the powder content of the slurry was set to be 53 vol.%.
  • Stainless steel having different diameters of pores and surface roughness, was used as porous materials, and the molding pressure applied in this case was 200 and 800 kgf/cm 2 .
  • the diameter of pores on the surface was determined by taking the average through observations under a microscope.
  • Table 2 shows results of the density of molded articles, molding time and mold release properties with respect to the porous materials, under various conditions.
  • Table 4 No. Molding pressure (kgf/cm 2 ) Average diameter of pores of porous materials ( ⁇ m) Surface roughness of porous materials (Rz) Density of molded articles (%) Molding time (sec.) Status of mold release 1 200 0.07 0.2 - not stiffened in 300 - 2 200 0.53 0.2 67.7 79 satisfactory 3 200 0.53 0.5 67.4 77 peeled off 4 200 4.8 0.3 68.8 53 satisfactory 5 200 4.8 0.6 68.7 54 peeled off 6 200 21.3 0.3 67.6 42 peeled off 7 800 0.07 0.2 - not stiffened in 300 - 8 800 0.53 0.2 69.4 69 satisfactory 9 800 0.53 0.5 69.2 68 peeled off 10 800 4.8 0.3 70.7 47 satisfactory 11
  • Y 2 O 3 , Al 2 O 3 as assistant agents were added to Si 3 N 4 powders having an average diameter of 0.5 ⁇ m. Then they were mixed in distilled water by making use of a ball mill. Some binder was added to the mixture and they were mixed further to make a slurry. The powder content of the slurry was 42 vol.%. Measurements of the particle size distribution indicated the mean particle diameter to be 0.53 ⁇ m.
  • Disks having a diameter of 40 mm and a thickness of 5 mm, were molded out of the slurry.
  • FIG. 2 shows a process for molding. Conditions were changed variously; diameters of pores in the porous stainless steel, surface roughness and diameters of pores in the filter. Casting without filter and casting as illustrated in FIG. 3 were practiced for comparison. And molding pressure applied in this case was 300 kgf/cm 2 .
  • Table 5 and 6 show how some conditions affect the molded ceramic articles and statuses of mold releasing. It may be seen from these Tables that satisfactory cast articles could be produced in accordance with the present invention.
  • Table 5 No. Process Filter present or none Average diameter of pores of filter ( ⁇ m) Materials of filter Average diameter of pores of metallic materials ( ⁇ m) 1 FIG. 2 none - - 20.1 2 FIG. 2 none - - 72.2 3 FIG. 2 none - - 8.2 4 FIG. 2 filter 0.05 resin film 20.1 5 FIG. 2 filter 0.05 resin film 72.2 6 FIG. 2 filter 0.4 filter paper 20.1 7 FIG. 2 filter 0.4 filter paper 72.2 8 FIG. 2 filter 0.4 filter paper 8.2 9 FIG. 2 filter 5.0 filter paper 20.1 10 FIG.
  • a mixture of powders was made by adding Y 2 O 3 , Al 2 O 3 as assistant agents to Si 3 N 4 powder having an average diameter of 0.8 ⁇ m, mixing it, in ethylalcohol and by drying it. Deionized water and a binder were added to the mixture. Making use of a nylon ball mill, they were made into slurry. The powder content of the slurry was set to be 40 vol.%.
  • Molding pressure (kgf/cm 2 ) Density of molded articles (%) Molding time (sec.) 1 Al 2 O 3 2 50.5 840 2 Al 2 O 3 20 51.3 220 3 Al 2 O 3 200 63.5 32 4 Al 2 O 3 950 64.7 9 *5 gypsum 2 49.2 720 *6 gypsum 20 gypsum fractured - *7 resin 2 49.9 720 *8 resin 20 51.2 200 *9 resin 200 resin fractured - *indicates comparisons
  • the slurry was made by mixing together Al 2 O 3 , powder having an average diameter of 1 ⁇ m, distilled water and some binder.
  • the powder content of the slurry was to be 53 vol.%.
  • the process for molding was the same as Example 1, as shown in FIG. 1.
  • Al 2 O 3 with different diameters of pores and surface roughness, was used.
  • the cavity rate of the Al 2 O 3 was 38 vol.%, and the molding pressure applied in this case was 200 and 800 kgf/cm 2 .
  • Table 8 shows results of density of molded articles, molding time and mold release properties with respect to the porous materials under various conditions.
  • Table 8 No. Molding pressure (kgf/cm 2 ) Average diameter of pores of porous materials ( ⁇ m) Surface roughness of porous materials (Rz) Density of molded articles (%) Molding time (sec.) Status of molded articles and mold releasing 1 200 0.07 0.2 - not stiffened in 300 - 2 200 0.71 0.2 68.2 72 satisfactory 3 200 0.71 0.7 67.9 69 peeled off 4 200 8.7 0.3 69.3 50 satisfactory 5 200 8.7 0.7 69.2 51 peeled off 6 200 24.4 0.3 68.1 35 peeled off 7 800 0.07 0.2 - not stiffened in 300 - 8 800 0.71 0.2 69.5 65 satisfactory 9 800 0.71 0.5 69.9 62 peeled off 10 800 0.71 0.7 69
  • Si 3 N 4 (90 to 95 wt%) with mean primary particle size of 0.5 ⁇ m and mean secondary particle size of 1.0 ⁇ m), as a main component, Y 2 O 3 (mean primary particle size of 0.5 ⁇ m) and Al 2 O 3 (mean primary particle size of 0.3 ⁇ m), as additives, were used.
  • the starting powders were mixed in a ball mill with distilled water and admixed with a binder in order to prepare slurries with volume concentrations of 42, 52 and 62 vol%.
  • the mean secondary particle sizes of the slurries were 1.3, 1.8 and 2.4 ⁇ m.
  • the optimum pressurization and timing of the three slurries was controlled so as to be within 4% of the molding length (100 mm) as from the position at which all the slurry in the mold is dehydrated and turned into molded article.
  • viscosity mean pore size of porus ceramic article ( ⁇ m) punch position (molding length) (mm) punch displacement (distance from 100 mm) (mm) density of molded article (g/cm 3 ) defects in molded articles 1 14, 15 42 1320 4.2 99 1 56.1 good 2 14, 15 42 1320 13.5 98 2 56.6 good 3 14, 15 42 1320 19.7 100 0 56.8 good 4 14, 15 52 2780 4.2 100 0 58.4 good 5 14, 15 52 2780 13.5 98 2 58.2 good 6 14, 15 52 2780 19.7 98 2 58.4 good *7 14, 15 62 6500 4.2 99 1 64.1 fracture at 10 mm diameter portion *8 14, 15 62 6500 13.5 98 2 63.1 fracture at 10 mm diameter portion *9 14, 15 62 6500 19.7 98 2 63.3 fracture at 10 mm diameter portion *indicates comparisons
  • Y 2 O 3 and Al 2 O 3 as assistant agents were added to Si 3 N 4 powder having an average diameter of 0.5 ⁇ m. Then they were mixed in distilled water by making use of a ball mill. Some binder was added to the mixture and they were mixed further to make the slurry. The powder content of the slurry was 42 vol.%. The average diameter was indicated to be 0.53 ⁇ m by measurement of the size distribution.
  • Disks having a diameter of 40 mm and a thickness of 5 mm, were molded out of the slurry through the process for molding as shown in FIG. 2.
  • the porous material was Al 2 O 3 . And other conditions were changed variously; diameters and surface roughness of the porous materials and diameters of pores in the filter. Molding without the filter and molding as illustrated in FIG. 3 were also performed for comparison. And molding pressure applied in this case was 300 kgf/cm 2 . Table 10 and 11 show how some conditions affect the molded ceramic articles and its status of molded articles and mold releasing. They also show that a satisfactory molded ceramic articles could be produced in accordance with the present invention. Table 10 No.
  • FIG.2 Materials of filter Average diameter of pores of ceramics materials ( ⁇ m) 1 FIG.2 none - - 24.4 2 FIG.2 none - - 72.2 3 FIG.2 none - - 8.7 4 FIG.2 filter 0.08 resin film 24.4 5 FIG.2 filter 0.08 resin film 72.2 6 FIG.2 filter 0.6 filter paper 24.4 7 FIG.2 filter 0.6 filter paper 72.2 8 FIG.2 filter 0.6 filter paper 8.7 9 FIG.2 filter 0.6 filter paper 72.2 10 FIG.2 filter 4.0 filter paper 24.4 11 FIG.2 filter 4.0 filter paper 72.2 12 FIG.2 filter 4.0 filter paper 8.7 13 FIG.2 filter 4.0 filter paper 72.2 14 FIG.2 filter 23.2 filter cloth 24.4 15 FIG.2 filter 23.2 filter cloth 72.2 16 FIG.2 filter 23.2 filter cloth 8.7 17 FIG.3 filter 4.0 filter paper plus filter cloth diameter of holes for the hydration 1400 18 FIG.3 filter 4.0 filter paper plus filter cloth 2000 19 FIG.3 filter 4.0 filter paper plus filter cloth 2
  • molded ceramic articles having a high density and a smoothed surface could be surely produced in a relatively short time.
  • Si 3 N 4 (90-95 wt%) with the mean primary particle size of 0.2 ⁇ m and the mean secondary particle size of 0.5 ⁇ m, as a main component, and Y 2 O 3 , with the mean primary particle size of 0.5 ⁇ m and Al 2 O 3 with the mean primary particle size of 0.3 ⁇ m, as additives, were used.
  • the starting powders were mixed in a ball mill with distilled water and added to a binder to give a slurry with a volumetric concentration of the powders of 42 vol%.
  • the mean secondary particle size of the slurry was 0.53 ⁇ m (with the particle size of the main component of 0.5 ⁇ m which is raised to 0.53 ⁇ m under the effect of the additive). Using this slurry, a cylinder having a diameter of 10 mm and a length of 50 mm was produced. In this case aspect ratio is 5 (50 mm/10 mm).
  • the concept of the molding method is shown in FIG. 2.
  • the molding equipment basically included punch 1, die 2, mold 3 and a dehydrator. Molding was performed by pressurizing the slurry within the die with a punch, as in the case of press molding. The moisture in the slurry was removed from the system via the dehydrator. The dehydrated slurry was solidified to give a molded article. Pressurization was performed evenly with a punch having the same cross-section as the product cross-section. Since the slurry intruded into the space between the punch and the slurry (clearance), a sealant such as an O-ring was provided therein.
  • the dehydrator included (i) a porous member formed of SUS, (ii) a filter such as filter paper or filter cloth on the front surface, or (iii) an SUS plate having through-hole and a filter such as a filter paper or a filter cloth on its front side.
  • the slurry is not in direct contact with the porous member.
  • the punch, die and the mold are formed of metal, such as cemented carbide, as in the case of customary press molding, it is possible to use a higher molding pressure than in the conventional case wherein the device in its entirety is formed by a porous member.
  • the punch and the cavity were formed of cemented carbide, while the mold was formed of high speed steel. The molding was carried out at an elevated pressure of 300 kgf/cm 2 .
  • molding was also carried out in accordance with a method (iii)-1 in which no sealant was used in the clearance between the punch and the die, and a method (iii)-2 in which the die was formed of a resin used in a conventional casting mold.
  • the pressurizing conditions during molding were controlled by the molding time or punch displacement.
  • the molding conditions were determined as later described. If the pressurization is insufficient, slurry dehydration in the vicinity of the punch becomes insufficient and a non-solid portion is left. Conversely, if excess pressurization is made, the punch is moved excessively to mechanically compact the molded product, thus locally increasing the powder packing density in the molded product in the vicinity of the punch. The result is poor dimensional accuracy and deformation of the sintered product. If the molded article exhibits significant density fluctuations in the molded article, the article undergoes cracks or destruction. From this it follows that the pressurization end timing must be within a certain range as from the time point when a present amount of the moisture in the slurry in the mold is dehydrated and the slurry in its entirety has been molded.
  • the slurry was used in a quantity which gave a molding length of 50 mm.
  • the optimum pressurization end timing was set in accordance with one of the following two methods:
  • molding was carried out in accordance with a variety of molding time durations and punch displacements.
  • the pore size and surface roughness of the porous member and the filter pore size, as other molding conditions, were also varied.
  • a homogeneous ceramic sintered article with high dimension accuracy and high strength may be produced.
  • Contents of d) By further limiting the slurry conditions, articles of more intricate shape can be produced, in addition to the above effects. By selecting slurry conditions and using the above material, and by combining the above various mold types and molds of the specific shape, the effects shown on the left are produced.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Dispersion Chemistry (AREA)
  • Filtering Materials (AREA)
  • Press-Shaping Or Shaping Using Conveyers (AREA)
EP19950111854 1995-07-27 1995-07-27 Verfahren zum Formen von Keramikwerkstoffen Expired - Lifetime EP0756922B1 (de)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2036694A1 (de) * 2007-09-17 2009-03-18 SCG Building Materials Co., Ltd. Vorrichtung und Verfahren zur Formung eines Musters auf einer Keramikfliese oder einer Platte mit vorgeschriebener Dicke
CN101186080B (zh) * 2006-09-22 2011-08-17 Scg建筑材料有限公司 在规定厚度的瓷砖或板坯中成形图案的装置和方法
CN109624025A (zh) * 2018-12-28 2019-04-16 广西晶联光电材料有限责任公司 一种氧化物靶材的注浆成型模具和方法
CN109881666A (zh) * 2019-04-15 2019-06-14 河北省水利水电勘测设计研究院 一种岩心钻探多功能旋喷注浆器

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005011019B4 (de) * 2005-03-10 2007-01-04 Daimlerchrysler Ag Herstellung und Verwendung eines zerstörbaren Formkerns für den metallischen Guss

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GB1072997A (en) * 1964-07-29 1967-06-21 Jasba Keramikfabrik Method for use in the manufacture of cast articles
JPS6070701A (ja) 1983-09-26 1985-04-22 日東電工株式会社 チツプ抵抗体
JPS61297103A (ja) 1985-06-26 1986-12-27 キヤタラ−工業株式会社 泥漿鋳込み成形方法
JPS633906A (ja) 1986-06-24 1988-01-08 株式会社神戸製鋼所 泥しよう粉末材料の脱水成形方法
JPH0242321B2 (de) 1986-09-04 1990-09-21
US5156856A (en) * 1986-12-04 1992-10-20 Ngk Insulators, Ltd. Mold for forming molded body
EP0587160A1 (de) * 1992-09-10 1994-03-16 Sumitomo Electric Industries, Ltd. Verfahren und Form zur Herstellung von keramischen Gegenständen
JPH06262612A (ja) * 1993-03-12 1994-09-20 Sumitomo Electric Ind Ltd セラミックスの成形法および成形型

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GB790027A (en) * 1954-12-27 1958-01-29 Shenango China Inc Process for the manufacture of ceramic objects
GB1072997A (en) * 1964-07-29 1967-06-21 Jasba Keramikfabrik Method for use in the manufacture of cast articles
JPS6070701A (ja) 1983-09-26 1985-04-22 日東電工株式会社 チツプ抵抗体
JPS61297103A (ja) 1985-06-26 1986-12-27 キヤタラ−工業株式会社 泥漿鋳込み成形方法
JPS633906A (ja) 1986-06-24 1988-01-08 株式会社神戸製鋼所 泥しよう粉末材料の脱水成形方法
JPH0242321B2 (de) 1986-09-04 1990-09-21
US5156856A (en) * 1986-12-04 1992-10-20 Ngk Insulators, Ltd. Mold for forming molded body
EP0587160A1 (de) * 1992-09-10 1994-03-16 Sumitomo Electric Industries, Ltd. Verfahren und Form zur Herstellung von keramischen Gegenständen
JPH06262612A (ja) * 1993-03-12 1994-09-20 Sumitomo Electric Ind Ltd セラミックスの成形法および成形型

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101186080B (zh) * 2006-09-22 2011-08-17 Scg建筑材料有限公司 在规定厚度的瓷砖或板坯中成形图案的装置和方法
EP2036694A1 (de) * 2007-09-17 2009-03-18 SCG Building Materials Co., Ltd. Vorrichtung und Verfahren zur Formung eines Musters auf einer Keramikfliese oder einer Platte mit vorgeschriebener Dicke
CN109624025A (zh) * 2018-12-28 2019-04-16 广西晶联光电材料有限责任公司 一种氧化物靶材的注浆成型模具和方法
CN109881666A (zh) * 2019-04-15 2019-06-14 河北省水利水电勘测设计研究院 一种岩心钻探多功能旋喷注浆器
CN109881666B (zh) * 2019-04-15 2023-11-24 河北省水利水电勘测设计研究院 一种岩心钻探多功能旋喷注浆器

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