JP5757797B2 - Carbon jig - Google Patents

Description

  The present invention relates to a carbon jig used for hot press firing of ceramics.

  It is known as a general technique to perform hot press firing of ceramics regardless of oxides or non-oxides. In particular, for hot press firing in a non-oxidizing atmosphere, a carbon hot pressing jig is often used from the viewpoint of strength and heat conduction. Hot press firing is generally performed by filling ceramic powder in a hot press jig, firing the lid while applying a lid.

  For example, in the method for producing a yttria ceramic fired body described in Patent Document 1, the formed body is set on a carbon jig coated with boron nitride and hot-press fired in an argon atmosphere. Moreover, in the manufacturing method of the ceramic heater described in Patent Document 2, the silicon nitride composition is temporarily hot-press fired using a firing jig made of graphite and having a surface layer portion made of SiC. In the method of manufacturing a ceramic part described in Patent Document 3, a ceramic molded body or powder is housed in a carbon-type jig having a small total amount of contained metal, and is subjected to hot press firing.

JP 2008-174398 A JP 2003-40678 A JP-A-11-310461

  As described above, when a carbon jig is filled with ceramic powder or the like and pressed, the punch for transmitting the pressing force and the cylindrical die into which the punch is inserted are rubbed. Even after the punch is inserted, the punch and the die are rubbed due to the firing shrinkage of the ceramics. By rubbing each part of the jig in this way, the carbon is crushed and mixed into the ceramic powder particles to be press fired, which may cause carbon contamination.

  In addition, the carbon particles cannot be prevented from falling off due to rubbing of each part due to jig setting or rubbing between the jig and the installation base (not shown), but such carbon particles adhere to the clothes of the operator. , It can fall off during powder filling and cause carbon contamination.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a carbon jig capable of producing ceramics with less carbon contamination by hot press firing.

  (1) In order to achieve the above object, a carbon jig of the present invention is a carbon jig used for hot press firing of ceramics, and is installed on a base having a flat surface and the flat surface of the base. A plate-shaped spacer having a mold hole, a cylindrical die installed on the plane of the base by fitting the spacer into the mold hole, and fitted into the mold hole of the die, and the spacer The die and the punch are formed of carbon particles having a maximum particle diameter of 0.1 mm or less.

  Thereby, the detachment of the carbon particles can be prevented, and ceramics with less carbon contamination can be fired. In particular, carbon contamination that is noticeable in ceramics having a lightness L of 40 or more can be prevented and is effective.

  (2) Moreover, the carbon jig of the present invention is characterized in that the peripheral edge of the end face of the punch is chamfered. This makes it difficult for the periphery to come into contact when the punch is inserted into the die hole of the die, thereby preventing the carbon particles from coming off.

  (3) Moreover, the carbon jig of the present invention is characterized in that the inner peripheral edge of the die is chamfered. This makes it difficult for the periphery to come into contact when the spacer is fitted into the die hole of the die, thereby preventing the carbon particles from falling off.

  (4) Further, the carbon jig of the present invention is characterized in that the inner surface of the die and the side surface of the punch both have a surface roughness Ra of 10 μm or less. As described above, since the surface roughness of the contact surface between the die and the punch is small, degranulation due to rubbing hardly occurs.

  (5) Moreover, the carbon jig of the present invention is characterized in that both the die and the punch have a Shore hardness of 55 or more. Thus, since the dice and the punch are sufficiently hard, even if each part is rubbed during pressing and firing, it is difficult for the carbon particles to fall.

  (6) Further, the carbon jig of the present invention is characterized in that both the die and the punch have an impurity amount of 1000 ppm or less. Thereby, the die and the punch can make it difficult for the carbon particles to be crushed, and even if degranulation occurs, the influence of impurities on the contamination can be suppressed.

  According to the present invention, ceramics with less carbon contamination can be produced by hot press firing.

It is a perspective view which shows the carbon jig which concerns on 1st Embodiment. It is sectional drawing which shows the carbon jig which concerns on 1st Embodiment. It is sectional drawing which shows the usage method of the carbon jig which concerns on 1st Embodiment. It is sectional drawing which shows the carbon jig which concerns on 2nd Embodiment. It is sectional drawing which shows the carbon jig which concerns on 3rd Embodiment.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

[First Embodiment]
(Configuration of carbon jig)
FIG. 1 is a perspective view showing a carbon jig 10. FIG. 2 is a cross-sectional view showing the carbon jig 10. The carbon jig 10 is housed inside a furnace body of a hot press furnace and used for hot press firing of ceramics. In a hot press furnace, ceramic powder particles can be sintered under high temperature and press to produce a sintered body of high density and high purity. The carbon jig 10 includes a base 11, a spacer 12, a die 13, and a punch 14, and each part is made of carbon.

  The base 11 is formed in a disc shape and has a flat surface. The spacer 12 is formed in a disc shape and is installed on the plane of the base 11. The diameter of the spacer 12 substantially coincides with the inner diameter of a mold hole 13 c of a die 13 described later, and the spacer 12 is formed so as to fit into the mold hole 13 c of the die 13.

  The die 13 is formed in a cylindrical shape, and is installed on the plane of the base 11 with the spacer 12 fitted in the mold hole 13c. The mold hole 13c is formed so as to penetrate in the axial direction of the cylinder. The axial length of the die 13 is sufficiently larger than the thickness of the spacer 12, and when the spacer 12 is fitted to the die 13, a bottomed hole is formed by the spacer 12 and the die 13. The bottomed hole is filled with ceramic powder particles as a pressed body. A punch is inserted into the mold hole 13c from above, and the lower surface of the punch 14 is in contact with the ceramic powder particles.

  The punch 14 is formed in a cylindrical shape, and the diameter of the punch 14 substantially matches the inner diameter of the die hole 13 c of the die 13. In use, the punch 14 is inserted into the mold hole 13 c of the die 13, and a pressing force is applied from above to press the ceramic particles between the spacer 12.

  The die 13 and the punch 14 are formed of carbon particles having a maximum particle diameter of 0.1 mm or less. Thereby, the detachment of the carbon particles can be prevented, and ceramics with less carbon contamination can be fired. In particular, a noticeable carbon contamination can be prevented with ceramics having a lightness L of 40 or more. Thus, it is desirable that the carbon particle diameter is small. This is because large particles easily fall off. Further, it is preferably formed of isotropic graphite. The maximum particle size of the carbon particles can be specified by measuring the raw material particle size with a laser diffraction particle size distribution meter. Since the carbon particles do not grow during firing, graphitization, or the like at the time of manufacturing a carbon jig, they can be sufficiently specified by measuring the raw material particle size.

  Further, the inner surface of the die hole 13c of the die 13 and the side surface of the punch 14 both preferably have a surface roughness Ra of 10 μm or less. Thus, since the surface roughness of the mutual contact surface of the die 13 and the punch 14 is small, degranulation due to rubbing hardly occurs. From the viewpoint that each part of the carbon jig 10 is rubbed and particles fall off, it is desirable that the surface roughness of the carbon jig 10 is small.

  Moreover, it is preferable that both the die 13 and the punch 14 have a Shore hardness of 55 or more. Thus, since the dice 13 and the punch 14 are sufficiently hard, the carbon particles are unlikely to fall out during pressing and firing. Moreover, it is preferable that both the die 13 and the punch 14 have an impurity amount of 1000 ppm or less. Thereby, the dies 13 and the punch 14 are less likely to cause the degranulation of the carbon particles, and the influence of contamination is reduced even if the degranulation occurs.

  Further, the spacer 12 preferably has a side surface roughness Ra of 10 μm or less, a Shore hardness of 55 or more, and an impurity amount of 1000 ppm or less. This is because there is a step of fitting the die 13 to the spacer 12 when setting the carbon jig, and the contact surfaces are also rubbed at that time.

(Hot press firing using carbon jig)
A ceramic firing method using the carbon jig 10 will be described below. FIG. 3 is a cross-sectional view showing how to use the carbon jig 10.

  When hot press firing is performed on a desired ceramic, first, the carbon jig 10 is set. In the setting, the base 11 is disposed at a predetermined position, and the spacer 12 is disposed on the base 11.

  A spacer 12 installed on the base 11 is installed by fitting a die 13. In this way, a bottomed hole is formed by the spacer 12 and the die 13. This bottomed hole is filled with ceramic powder particles S. In that case, it may replace with the ceramic granular material S and may fill with a molded object. The molded body includes not only a mold or CIP molded body but also a green sheet laminate.

  In particular, when carbon is mixed in ceramics having a lightness L of 40 or more, it is effective to use the above-mentioned carbon jig when hot pressing firing ceramics of L40 or more. Such ceramics include alumina, yttria, zinc oxide, silicon nitride, aluminum nitride, oxides mainly composed of boron nitride, and non-oxide ceramics. The lightness L refers to L in the color difference-Lab color space. In this way, the ceramic is filled into the bottomed hole, and the punch is inserted into the bottomed hole to complete the setting.

  The carbon jig 10 thus set is placed at a position surrounded by a heat insulating material in the furnace body of the hot press furnace. The furnace body has a gas replacement device, and after the air in the internal space in which the carbon jig of the furnace body is accommodated is sucked out, the inside gas can be replaced by filling with a predetermined inert gas. Further, the furnace body is provided with a heater, and the temperature inside the furnace body can be raised to a predetermined temperature and maintained.

  After installing the carbon jig 10, the furnace is closed, the inside is exhausted by an exhaust system, and the heater is energized to heat the inside of the furnace. Then, the punch is pressed downward by a pusher inserted through the furnace body, and the punch is lowered by this pusher to compress the powder. Thus, by applying a load downward to the upper end of the punch, the ceramic granular material can be pressurized. The pusher is lowered in a heated state, and the ceramic is fired in a state of being pressed with a predetermined pressing force.

[Second Embodiment]
In the above embodiment, the periphery of each part of the carbon jig 10 is not particularly processed, but may be processed into a chamfered shape. FIG. 4 is a cross-sectional view showing the carbon jig 20 that has been chamfered.

  In the carbon jig 20 shown in FIG. 4, the peripheral edge 23 a of the inner surface of the die 23 and the peripheral edge 24 a of the end face of the punch 24 are chamfered. Specifically, the chamfered shape is a C plane or an R plane. By forming the C surface and the R surface, the member is less likely to be caught when the carbon jig 20 is set.

  The R plane is more preferable than the C plane. As for the dimension of the C surface or R surface, C or R is preferably at least 0.1 mm or more, and more preferably about 0.5 mm. Larger than this is not a problem, but inevitably the burrs of the ceramic sintered body become large, so that processing takes time.

[Third Embodiment]
In the above embodiment, the one peripheral edge 23a of the inner surface of the die 23 and the peripheral edge 24a of the end surface of the punch 24 are chamfered, but the peripheral edge of the end surface of the spacer and the other peripheral edge of the inner surface of the die are also chamfered. May be. FIG. 5 is a cross-sectional view showing the carbon jig 30 further chamfered.

  As shown in FIG. 5, in the carbon jig 30, the peripheral edge 32 a of the end face of the spacer 32, both peripheral edges 33 a and 33 b of the inner surface of the die 33, and the peripheral edge 24 a of the end face of the punch 24 are chamfered. By chamfering the peripheral edges of the members that easily come into contact with each other when they are fitted in this way, the members are less likely to be caught when the carbon jig 30 is set, and as a result, contamination is less likely to occur. In any case, the chamfered shape is preferably the R surface rather than the C surface.

[Other Embodiments]
Even when BN, which is a release material, is applied to the contact portion of the ceramic particle 10 of the carbon jig 10, or when a carbon sheet is disposed between the carbon jig 10 and the ceramic particle. The present invention is effective.

[Examples and Comparative Examples]
Experiments were conducted using carbon jigs constructed under different conditions. The inner diameter of each carbon jig was unified to φ100 mm. Specific specifications of each carbon jig are shown in the following table. The maximum particle size of the carbon particles constituting each carbon jig was specified by measuring the raw material particle size with a laser diffraction particle size distribution meter. As an object of hot press firing, an aluminum nitride powder to which 5% by weight of yttrium oxide was added was used.

  Using each carbon jig, in a nitrogen atmosphere, the hot press was fired at 1800 ° C. for 6 hours while being pressurized at 10 MPa. As a result, a ceramic sintered body having a size of φ100 × 10 mm was obtained. The upper and lower surfaces of the obtained ceramic sintered body were ground by 1 mm, and the presence or absence of carbon contamination was evaluated by the number of black spots generated on both surfaces of the ground φ100. The black spots were counted so that they could be observed with the naked eye. A black point refers to an area having a lightness of less than L40. The presence or absence of a black spot is performed by placing a color sample next to the sintered body and comparing it. For example, a black spot having a diameter of 0.5 mm cannot be measured with a color difference meter, but is counted because it can be grasped with the naked eye. Carbon contamination does not necessarily appear as black-spot carbon particles but may diffuse to some extent as black spots. In such a case as well, the above criteria were used.

  In the rightmost column of Table 1, the evaluation results are shown by ◎, ○, Δ, and ×, classified by the number of black spots. As shown in Table 1, when a carbon jig having a maximum particle diameter of 0.1 mm or less, a Ra on the jig surface of 10 μm or less, and a Shore hardness of 55 or more is used (Example) 1-6, 8), good results of ◯ or ◎ were obtained. Further, when chamfering was performed on the peripheral edge of the end face of the punch of the carbon jig of Example 2 and the peripheral edge of the inner surface of the die and hot pressing was performed, good results of ◎ were obtained (Example 7). On the other hand, when a carbon jig having no chamfering and a Ra on the jig surface of greater than 10 μm was used (Examples 9 and 10), the number of black spots was small, although inferior to Examples 1 to 8. In addition, when a carbon jig having no chamfering and a jig having a Shore hardness of less than 55 was used (Example 11), the number of black spots was small although it was inferior to Examples 1-8. On the other hand, when the maximum particle diameter of the carbon particles was larger than 0.1 mm (Comparative Examples 1 and 2), the number of black spots increased. From the above, it was demonstrated that ceramics with less carbon contamination can be produced by hot press firing using the carbon jig of the example.

DESCRIPTION OF SYMBOLS 10 Carbon jig 11 Base 12 Spacer 13 Dies 13c Die hole 14 Punch 20 Carbon jig 23 Die 23a Edge of the inner surface of the die 24a Edge of the end face of the punch 30 Carbon jig 32 Spacer 32a Edge of the end face of the spacer 33 Dies 33a, 33b Periphery S of the inner surface of the die S Ceramic powder

Claims (6)

A method for producing a ceramic having a lightness L of 40 or more by hot press firing using a carbon jig,
A base having a plane, a plate-like spacer installed on the plane of the base, a mold hole, and a cylindrical shape installed on the plane of the base by fitting the spacer into the mold hole A die and a punch that fits into the die hole of the die and presses the ceramic powder particles between the spacer, and the die and the punch are made of carbon particles having a maximum particle diameter of 0.1 mm or less. Arranging the formed carbon jig at a predetermined position;
Filling the carbon jig with a ceramic powder or molded body as a raw material;
And a step of performing hot press firing by compressing the raw material while maintaining the temperature at a high temperature using the carbon jig . The ceramic manufacturing method according to claim 1 , wherein the carbon jig has a chamfered peripheral edge of the end face of the punch. The ceramic manufacturing method according to claim 1 , wherein the carbon jig has a chamfered peripheral edge on the inner side surface of the die. The ceramic jig according to any one of claims 1 to 3, wherein in the carbon jig, the inner surface of the die and the side surface of the punch both have a surface roughness Ra of 10 µm or less . Manufacturing method . The method for producing ceramics according to any one of claims 1 to 4, wherein the carbon jig has a die hardness and a punch hardness of 55 or more. 6. The method for producing ceramics according to claim 1 , wherein the carbon jig has an impurity amount of 1000 ppm or less in both the die and the punch.

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