JP2006334976A - Method for producing fine ceramic using ultrasonic waves - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for attaining the densification of components with regard to a method for producing a ceramic component using cold hydrostatic pressurization molding and hot hydrostatic pressurization treatment. <P>SOLUTION: With regard to ceramic powder molding and the hot hydrostatic pressurization treatment of a ceramic sintered body, ultrasonic vibration is applied during cold hydrostatic pressurization (CIP) and hot hydrostatic pressurization (HIP). By using a CIP device or a HIP device suppressing the occurrence of a defect and the formation of pores by bridging, the fillability of powdered matter and the fineness of a sintered body are promoted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a dense ceramic using hydrostatic pressure (hereinafter abbreviated as CIP) or hot isostatic pressure (hereinafter also abbreviated as HIP).

  Up to now, measures such as CIP processing at higher pressures, controlling the plasticity of granules, HIP processing at higher pressures, controlling pressure patterns, and increasing the density before HIP as much as possible Has been taken.

For example, as disclosed in Patent Document 1, forging is performed concurrently with HIP, or pressure medium (pressure medium) is heated during CIP as disclosed in Patent Document 2 to increase the plasticity of the granules. Attempts have been made.
Japanese Patent Laid-Open No. 3-13506 JP-A-4-247904

  However, the above-described method has problems such as a heavy burden on the apparatus, a large number of control parameters during powder preparation and primary firing, and poor reproducibility. For example, when carrying out forging at the time of HIP disclosed in Patent Document 1, the apparatus becomes large, but there is a problem that it cannot cope with a complicated shape, and pressure during CIP disclosed in Patent Document 2 Even when the medium (pressure medium) is heated, it is difficult to perform the treatment for a short time, and maintaining the setting of 80 ° C. or higher, which causes heat softening, has a problem that the operational cost is considerably increased.

  Therefore, the present invention has been made in view of the conventional problems, and an object of the present invention is to provide a method for easily producing a dense ceramic.

  The method for producing a dense ceramic according to the present invention uses an ultrasonic oscillator set in each pressure vessel in a CIP molding and / or HIP processing production equipment frequently used in producing various ceramics. It is characterized by applying ultrasonic vibration.

  That is, the gist of the present invention is as follows.

  (1) When ceramic powder or powder obtained by granulating a mixture of ceramic powder and plastic resin is first molded and then filled in a shrinkable tare, and secondarily subjected to CIP molding at a higher pressure, or The powder or the granulated powder is filled in a shrinkable tare, and then formed into an ultrasonic wave by an ultrasonic oscillator set inside or outside the pressure vessel at the time of CIP molding. A method for producing a dense ceramic molded body using ultrasonic waves, characterized by applying vibration.

  (2) When the ceramic sintered body obtained by primary firing is subjected to secondary firing by higher-pressure HIP treatment, an ultrasonic wave is applied by an ultrasonic oscillator set inside or outside the pressure vessel during HIP treatment. A method for producing a dense ceramic sintered body using ultrasonic waves, characterized by applying vibration.

  (3) Ceramic powder, or powder obtained by granulating a mixture of ceramic powder and plastic resin, after primary molding, when a rubber coating is sheathed and secondarily subjected to CIP molding at a higher pressure, or the above powder, Alternatively, the granulated powder is filled in a shrinkable tare and then subjected to ultrasonic vibration by an ultrasonic oscillator set inside or outside the pressure vessel at the time of CIP molding when CIP molding is performed. After that, when performing primary firing, and then performing secondary firing by higher-pressure HIP treatment, applying ultrasonic vibration with an ultrasonic oscillation device set inside or outside the pressure vessel at the time of HIP treatment A method for producing a dense ceramic sintered body using a characteristic ultrasonic wave.

  If the method for producing a ceramic according to the present invention is applied to the production of, for example, alumina, sialon, zirconia, silicon carbide, etc., it becomes possible to stably produce a dense ceramic with few defects. Moreover, it can be easily incorporated into the apparatus, and the operation cost is extremely low. Further, the ceramic material can be easily densified without requiring high cost. This enables high quality and stable production.

  As a result of various studies in order to achieve the above object, the present inventors have applied ultrasonic vibration by an ultrasonic oscillation device set in a pressure vessel of CIP or HIP, thereby forming a bridge during molding. It has been found that it has a function of suppressing the formation of pores and pores and promoting the disappearance of closed pores in the secondary firing treatment. The inventors of the present invention diligently studied the application of ultrasonic vibration to a typical manufacturing process of ceramics and came to provide a specific method.

  Until now, before molding large structures such as alumina, sialon and zirconia, silicon nitride and silicon carbide, ceramic powder is mixed with thermoplastic resin such as polyethylene and polyvinyl alcohol, and this mixture is spray granulated or A method of CIP molding after granulating to about 30 to 80 μm by freeze drying or the like and filling a shrinkable tare has been generally used.

  In the present invention, when CIP molding is performed, as shown in FIG. 1, ultrasonic vibration is applied by an ultrasonic oscillator (for example, an ultrasonic oscillator 4) set inside or outside the pressure vessel 1. As a result, the fluidity of the powder is more activated during CIP molding, and it is possible to suppress the generation of defects during molding. FIG. 1 schematically shows a CIP device in which a vibrator for ultrasonic vibration (specifically, an ultrasonic oscillator) is incorporated in a general CIP device for use in the embodiments described later. FIG. Reference numeral 2 in FIG. 1 represents an elevating piston, and reference numeral 3 represents a setter table for the sample.

  Examples of the ceramic powder of the present invention include alumina, zirconia, silicon nitride, silicon carbide, cordierite and the like, and the size is often about 0.1 to 10 μm as the center particle size.

  Further, as a mixing method of the ceramic powder of the present invention, a rotary pot mill, a planetary ball mill, an attrition mill, a vibrating ball mill, or the like can be used, and alumina, zirconia, mullite, silicon nitride, sialon, carbonization can be used. It can be used for manufacturing a ceramic sintered body having a fine ceramic such as silicon as a parent phase.

  As the pot or ball to be used, it is preferable to use a sintered body having the same composition as the powder to be mixed, but it is also possible to use another material with less wear or a resin-coated ball.

  As a method for forming the obtained mixed powder into a desired shape, when ultrasonic vibration of the present invention is used, CIP forming after uniaxial press forming or shrinkage of a direct rubber mold, vinyl, paper mold, etc. It is preferable to fill in a tare having properties and then perform CIP molding.

  Bridging during molding by making the mixed powder flow and consolidate easily by applying ultrasonic vibration appropriately with an ultrasonic oscillator set inside or outside the pressure vessel during CIP molding. And the formation of pores can be suppressed, and a dense ceramic molded body can be produced.

  Ultrasonic vibration can be applied to other typical ceramic forming methods such as casting, extrusion, doctor blade forming, and injection forming.

  The present invention can also be applied to the case where CIP molding is performed by filling ceramic powder into a shrinkable tare as it is. Furthermore, ceramic powder or powder obtained by granulating a mixture of ceramic powder and plastic resin is first molded and then filled into a shrinkable tare, and secondarily subjected to CIP molding at a higher pressure than primary molding. It can also be applied to cases.

  Further, the application of ultrasonic vibration according to the present invention can be applied to the case where the ceramic sintered body obtained by the primary firing is subjected to secondary firing by HIP treatment at a higher pressure than that during the primary firing.

  Usually, ceramic sintered bodies obtained after various primary firings such as silicon nitride and silicon carbide in addition to alumina, sialon and zirconia have a relative density of 95%, which is the ratio of the bulk density of the sintered body to the theoretical density. It has been densified as described above. That is, it can be said to be a ceramic sintered body that is fired and densified to a relative density of 95% or more by closed pores substantially by primary firing.

  Furthermore, even during HIP treatment, which is the most common method for secondary firing to increase the density and strength from the time of primary firing, the mixed powder is obtained by applying ultrasonic vibration according to the present invention. Provided a new technique of using ultrasonic vibration in the HIP processing chamber in order to make it possible to eliminate the internal defects during the various primary firings more efficiently by facilitating flow and consolidation. Is.

  At the time of HIP processing, as shown in FIG. 2, by applying ultrasonic vibration appropriately by an ultrasonic oscillation device (for example, ultrasonic oscillator 4) set inside or outside the pressure vessel 1, The disappearance of closed pores in the secondary firing treatment can be promoted, and a dense ceramic sintered body can be produced. FIG. 2 schematically shows a HIP apparatus in which a vibrator for ultrasonic vibration (specifically, an ultrasonic oscillator) is incorporated in a general HIP apparatus for use in an embodiment described later. FIG. Reference numeral 3 in FIG. 2 represents a setter table for the sample, and reference numeral 5 represents a heater for HIP.

  As the sintering method, in addition to the normal pressure sintering method, the gas pressure sintering method, and the hot press method, induction heating sintering and the like can be mentioned, but the same as the HIP method which is the secondary densification sintering of the present invention. In addition, ultrasonic vibration can be developed.

As the sintering atmosphere of the present invention, depending on the ceramic compound composition, the oxide system is basically in the atmosphere, and the non-oxide system is in an inert atmosphere gas such as Ar gas or N ₂ gas or in vacuum. preferable. This is because the ceramic raw material powder suppresses the reaction with the atmospheric gas.

  In addition, after applying ultrasonic vibration during the CIP molding, primary firing is performed, and then when performing secondary firing by HIP treatment at a higher pressure than the primary firing, The effect is greater.

  The ultrasonic vibration of the present invention may be a standing wave applied from the outer periphery of the pressure vessel or a structure in which a vibrator is loaded inside. It is more efficient to appropriately adjust the output and frequency according to the size of the molded body and the thickness of the sintered body.

  For both CIP and HIP, a square plate or cylinder having a size of several centimeters is sufficiently effective in an output range of about 3 to 10 W from the outside or from the inside, but more preferably 5 W or more. Similarly, a square plate or cylinder having a size of several tens of cm is sufficiently effective in the output range of about 10 to 30 W from the outside or the inside, but more preferably 20 W or more.

  Next, examples of the present invention will be described together with comparative examples.

(Examples 1-3)
Silicon nitride (Si ₃ N ₄ ) powder (β conversion 90% or more, purity 97%, average particle size 0.8 μm),
Yttrium oxide (Y ₂ O ₃ ) powder (average particle size 1.5 μm),
Aluminum oxide (Al ₂ O ₃ ) powder (average particle size 0.6 μm),
Magnesium oxide (MgO) powder (average particle size 0.4 μm),
Zirconium oxide (Zr ₂ O) powder (average particle size 1.2 μm),
Was added in a predetermined amount (mass%) shown in Table 1, and purified water or acetone was used as a dispersion medium and kneaded for 24 hours in a ball mill with silicon nitride ceramics attached thereto. The amount of purified water or acetone added was 140 g with respect to 100 g of all ceramic powder raw materials.

  Next, the obtained mixed powder was put into a 120 mm × 120 mm mold, uniaxially molded at 120 mm × 120 mm × t20 mm at a pressure of 20 MPa, and then high-pressure molded by a CIP apparatus with ultrasonic vibration (output 10 W). The CIP pressure was 120 MPa, and a plate-like molded body having a size of 110 mm × 110 mm × thickness 18 mm was obtained.

As the sintering conditions, Example 1 was maintained for 8 hours at each temperature shown in Table 1 while nitrogen gas was flowing, and Examples 2 and 3 were subjected to pressureless sintering in the atmosphere. Followed by secondary firing process at a HIP apparatus _{N 2} gas with ultrasonic vibration (output 15W). The HIP pressure was 180 MPa, and a plate-like dense sintered body of 86 mm × 86 mm × thickness 14 mm was obtained.

(Examples 4 to 9)
Examples 4 to 9 were prepared using the same raw materials as in Examples 1 to 3 and the same composition and the same purified water or acetone, but with CIP molding without ultrasonic vibration and ultrasonic vibration (output 15 W) This is the case where the HIP process is performed (Examples 4 to 6), and the CIP molding with ultrasonic vibration (output 10 W) and the HIP process without ultrasonic vibration are performed (Examples 7 to 9).

The sintered body density was measured by the Archimedes method. A test piece for evaluating mechanical properties was cut out from the obtained sintered body, and its characteristics were evaluated. The bending strength was measured with a test piece conforming to JIS R1601 at a crosshead speed of 0.5 mm / sec, and the hardness was measured as Vickers hardness at an indentation load of 9.8 N. For toughness, the fracture toughness value (K _IC ) was measured at room temperature by the SEPB method according to JIS R1607.

(Comparative Examples 10-12)
This is a case (Comparative Examples 10 to 12) in which CIP molding and HIP processing without ultrasonic vibration are performed.

  From the above, it was found that the sintered body of the present invention had excellent values for density, strength, hardness, and toughness compared to those without ultrasonic vibration. It can be judged that the present invention is applicable to various ceramic material types for general purposes.

It is the schematic showing the CIP apparatus incorporating the vibrator | oscillator for ultrasonic excitation. It is the schematic showing the HIP apparatus incorporating the vibrator | oscillator for ultrasonic excitation.

Explanation of symbols

1 pressure vessel,
2 lifting piston,
3 Sample setter table,
4 Ultrasonic oscillator,
5 Heater for HIP.

Claims (3)

Ceramic powder or powder obtained by granulating a mixture of ceramic powder and plastic resin is filled into a shrinkable tare after primary molding, and then subjected to secondary hydrostatic pressure molding at a higher pressure, or ,
When filling the powder or the granulated powder into a shrinkable tare, and then hydrostatic pressure molding,
A method for producing a dense ceramic molded body using ultrasonic waves, wherein ultrasonic vibration is applied by an ultrasonic oscillator set inside or outside a pressure vessel at the time of hydrostatic pressure molding. When the ceramic sintered body obtained by the primary firing is subjected to the secondary firing by the hot isostatic pressing process at a higher pressure than during the primary firing,
A method for producing a dense ceramic sintered body using ultrasonic waves, wherein ultrasonic vibration is applied by an ultrasonic oscillator set inside or outside a pressure vessel at the time of hot isostatic pressing. Ceramic powder, or powder obtained by granulating a mixture of ceramic powder and a plastic resin, after primary molding, when a rubber coating is externally applied and then subjected to secondary hydrostatic pressure molding at a higher pressure, or
When filling the powder or the granulated powder into a shrinkable tare, and then hydrostatic pressure molding,
After applying ultrasonic vibration by an ultrasonic oscillator set inside or outside the pressure vessel during hydrostatic pressure molding,
When performing the primary firing, and then performing the secondary firing by a higher pressure hot isostatic pressing process,
A method for producing a dense ceramic sintered body using ultrasonic waves, wherein ultrasonic vibration is applied by an ultrasonic oscillator set inside or outside a pressure vessel at the time of hot isostatic pressing.

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