JP2011246316A - Method for firing ceramic and ceramic firing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for firing ceramic for preventing inflow of impurities such as oxygen into a firing container.SOLUTION: An atmospheric gas is directly supplied from a gas supply source 5 arranged outside a firing furnace 1 into the firing container 10 through a gas supply port 12 formed in the firing container 10. The atmospheric gas supplied from the gas supply port 12 is circulated in the firing container 10 and then the gas is discharged outside the firing container 10 through a gas discharge outlet 13.

Description

The present invention relates to a method for firing ceramics in a firing furnace, and more particularly to a method for firing ceramics in a firing furnace supplied with atmospheric gas.
The present invention also relates to a ceramic firing apparatus for firing ceramics in this way.

Ceramics such as silicon nitride are widely used for machine parts such as automobile parts. Such a ceramic is manufactured by firing in a firing furnace, but if the ceramic raw material is fired without reacting with the atmosphere, the ceramic is densified due to shrinkage of the ceramic, and due to the variation in shrinkage, the size of the sintered body is reduced. There was also a problem that variation occurred.
In order to solve this problem, there is a method of obtaining ceramics having a small shrinkage rate by using silicon nitride, silicon carbide, boron carbide, alumina, zirconia or the like as a ceramic raw material, and holding the temperature at a temperature at which sintering is not completed and then lowering the temperature. Further, by using a ceramic raw material containing silicon and reacting in a nitrogen atmosphere and sintering, silicon nitride, sialon, etc. can be produced as a crystalline phase, and shrinkage during sintering can be further suppressed. .
As described above, the firing of the ceramic using the reactive sintering accompanied by the reaction with the atmospheric gas during the sintering is generally performed in the firing container 22 such as a crucible placed in the firing furnace 21 as shown in FIG. The objects to be processed C are stacked, and the atmosphere gas is supplied from the gas supply source 23 into the firing furnace 21 to raise the temperature in the firing furnace 21 in a reducing atmosphere by the heater 24. The atmospheric gas flows into the baking container 22 from the opening 25 of the baking container 22, but since only one opening 25 is provided, the flow of the atmospheric gas in the baking container 22 cannot be controlled. It was difficult to uniformly supply the atmospheric gas to the workpiece C in the baking container 22. Further, oxygen is generated from the heater 24 and the furnace material in the firing furnace 21, and the generated oxygen flows into the firing container 22 together with the atmospheric gas, and oxidizes the workpiece C in the firing container 22 and fires. There was a risk of reducing the effect.

  Thus, for example, Patent Document 1 proposes a ceramic firing method in which atmospheric gas is uniformly diffused in a firing container and fired. In this ceramic firing method, the firing chamber is divided into an upper chamber and a lower chamber, and the atmosphere gas is uniformly diffused into the firing container by introducing the atmosphere gas into the firing container from the lower chamber side.

Japanese Patent Laid-Open No. 4-144773

  However, also in this baking method, oxygen generated from a heater or the like installed in the lower chamber flows into the baking container together with the atmospheric gas, so that the object to be processed is oxidized.

The present invention has been made to solve such conventional problems, and an object of the present invention is to provide a ceramic firing method that suppresses the inflow of impurities such as oxygen into the firing vessel.
Another object of the present invention is to provide a ceramic firing apparatus for firing ceramics in this way.

  In order to achieve the above object, a ceramic firing method according to the present invention is a ceramic firing method in which a firing container in which a workpiece is placed is placed in a firing furnace and the workpiece is fired. An atmosphere gas from a gas supply source arranged outside the firing furnace is directly supplied into the firing container from a gas supply port formed in the firing container, and is supplied from the gas supply port in the firing container. In this method, the atmospheric gas is circulated and discharged out of the firing container through a gas discharge port.

Here, the atmospheric gas can be supplied into the baking container from the bottom surface side of the baking container and discharged out of the baking container from the upper surface side of the baking container.
Further, the atmospheric gas may be supplied into the baking container from the upper surface side of the baking container and discharged out of the baking container from the lower surface side of the baking container.

The fired ceramic is preferably silicon nitride.
Moreover, it is preferable that the said atmospheric gas consists of at least 1 among nitrogen, hydrogen, and argon.
Moreover, the said atmospheric gas can be supplied in the said baking container via the reducing agent arrange | positioned at the said gas supply port of the said baking container.

  Further, the ceramic firing apparatus according to the present invention is a ceramic firing apparatus for firing a workpiece by placing a firing container in which the workpiece is placed in a firing furnace. A gas supply port for supplying a gas and a gas discharge port for discharging the atmospheric gas to the outside, and a gas supply of the atmospheric gas from the gas supply source arranged outside the baking furnace A gas supply pipe that is directly supplied into the firing container from the mouth, and circulates the atmospheric gas supplied from the gas supply port in the firing container and discharges it from the gas discharge port to the outside of the firing container. Device.

  Here, the apparatus further includes a container base for placing the baking container at a lower portion in the baking furnace, the gas supply port is provided on the lower surface of the baking container, and the gas discharge port is provided on the upper surface of the baking container. The gas supply pipe is provided so as to reach the gas discharge port through the inside of the container table, so that the atmospheric gas can be directly supplied into the baking container.

Moreover, it has further a mounting part which mounts the said to-be-processed object in the said baking container, and the said description part can also install the said to-be-processed object so that stacking is possible.
The gas supply port of the baking container may further include a reducing agent that reduces the atmospheric gas supplied into the baking container.

  According to the present invention, the inflow of impurities such as oxygen into the firing container can be suppressed.

It is sectional drawing which shows the structure of the ceramic baking apparatus which concerns on Embodiment 1 of this invention. It is a perspective view which shows the structure of the container stand used in Embodiment 1. It is sectional drawing which shows the structure of the ceramic baking apparatus which concerns on the modification of Embodiment 1. It is sectional drawing which shows the structure of the ceramic baking apparatus which concerns on the other modification of Embodiment 1. It is sectional drawing which shows the structure of the ceramic baking apparatus which concerns on Embodiment 2. FIG. It is sectional drawing which shows the structure of the ceramic baking apparatus in a prior art example.

  Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

Embodiment 1
In FIG. 1, the structure of the ceramic baking apparatus which concerns on Embodiment 1 of this invention is shown. The ceramic firing apparatus has a firing furnace 1 made of a heat-resistant material. The firing furnace 1 has a firing chamber 2 that is a hollow space inside and is kept secret from the outside. As the heat resistant material constituting the firing furnace 1, for example, alumina or the like can be used.

  A gas supply pipe 3 is installed in the lower part of the firing furnace 1, and a gas discharge pipe 4 is installed in the upper part of the firing furnace 1. The gas supply pipe 3 is connected to a gas supply source 5 disposed outside the firing furnace 1, and introduces nitrogen (atmospheric gas) supplied from the gas supply source 5 at a predetermined flow rate into the firing furnace 1. . Further, the gas discharge pipe 4 is connected to a pressure regulating valve 6 and a decompression device (not shown), and nitrogen inside the firing furnace 1 is discharged to the outside of the firing furnace 1 through the gas discharge pipe 4 by the decompression device. The firing chamber 2 is adjusted to a predetermined degree of vacuum, and the pressure adjusting valve 6 is adjusted to maintain the predetermined degree of vacuum in the firing chamber 2.

A heater 7 that raises the temperature of the firing chamber 2 is installed on the ceiling of the firing furnace 1. As the heater 7, for example, a molybdenum disilicide heater or the like can be used.
A container base 8 for placing the firing container is disposed at the bottom of the firing furnace 1. The container base 8 is formed with a conduit 9 for passing the gas supply pipe 3 from the outer surface of the container base 8 to the center.
A baking container 10 is placed on the upper surface of the container base 8. The firing container 10 has a placement portion 11 for placing the workpiece C therein. A plurality of placement units 11 are installed in the axial direction (vertical direction) of the baking container 10, and a plurality of objects to be processed C are stacked. In addition, the mounting part 11 has air permeability such as a plate-like member or a net-like member in which a large number of through-holes are formed, and allows atmospheric gas to pass in the vertical direction. Moreover, the baking container 10 has a gas supply port 12 that penetrates the lower surface and a gas discharge port 13 that penetrates the upper surface. Nitrogen is supplied from the gas supply port 12 to the inside of the baking container 10 and is discharged from the gas discharge port 13 to the outside of the baking container 10. As the baking container 10, for example, a crucible or a setter can be used.
In the present embodiment, the workpiece C is made of silicon.

  FIG. 2 shows the configuration of the container base 8. The container base 8 has a disk shape on which the firing container 10 can be placed on the upper surface, and the thickness thereof is larger than the outer diameter of the gas supply pipe 3. In the container base 8, a pipe line 9 is formed by cutting out from the outer surface toward the center for passing the gas supply pipe 3. By installing the gas supply pipe 3 connected to the gas supply source 5 in the pipe line 9, the container base is connected via the gas supply pipe 3 from the gas supply source 5 in which nitrogen is arranged outside the firing furnace 1. 8 is supplied to the central part. On the other hand, the firing container 10 is placed on the upper surface of the container table 8 by aligning the gas supply port 12 formed at the center of the lower surface of the firing container 10 with the center portion of the container table 8. Thereby, nitrogen from the gas supply source 5 disposed outside the firing furnace 1 hardly leaks out of the firing container 10 and from the gas supply port 12 formed in the firing container 10 via the gas supply pipe 3. It is supplied directly into the firing container 10.

  Next, the operation of the ceramic firing apparatus shown in FIG. 1 will be described.

  First, as shown in FIG. 2, a pipe 9 in which a gas supply pipe 3 connected to a gas supply source 5 arranged outside the firing furnace 1 is formed from the outer surface of the container base 8 toward the center portion. Installed inside. Next, the firing container 10 is placed on the upper surface of the container table 8 by aligning the gas supply port 12 formed through the center of the lower surface of the firing container 10 and the center of the container table 8. A plurality of objects to be processed C are stacked on the placement portion 11 of the placed firing container 10.

Subsequently, the air in the firing chamber 2 is discharged from the gas discharge pipe 4 by the decompression device. When the firing chamber 2 is depressurized to, for example, −0.1 MPa or less, the firing chamber 2 is heated to around 600 ° C. with the heater 7 in order to burn the carbon contained in the workpiece C in the pretreatment, for example. Nitrogen is supplied at a flow rate of 2 to 4 L / min from a gas supply source 5 disposed outside of 1. Thereafter, when the pressure in the firing chamber 2 becomes, for example, −0.09 to −0.08 MPa, the flow rate of nitrogen from the gas supply source 5 is switched to a predetermined flow rate.
Nitrogen supplied at a predetermined flow rate from the gas supply source 5 is led to the gas supply port 12 of the firing container 10 through the gas supply pipe 3 connected to the gas supply source 5, and the inside of the firing container 10 is supplied from the gas supply port 12 Supplied directly to. The nitrogen supplied into the baking container 10 flows in the direction of the gas discharge port 13 through the inside of the baking container 10 on which the objects to be processed C are stacked in accordance with the flow rate of nitrogen supplied from the gas supply source 5. Here, the flow rate of nitrogen supplied from the gas supply source 5 is adjusted to such an extent that a gas such as oxygen existing outside the baking container 10 does not flow into the baking container 10 from the gas discharge port 13. It is supplied at a flow rate of 0.3 to 2 L / min.
When the inside of the firing container 10 is filled with nitrogen, the firing chamber 2 is heated to, for example, 1300 ° C. to 1500 ° C. by the heater 7, and the workpiece C stacked in the firing container 10 is fired.

  Thereby, oxygen is generated from the heater 7 or the like outside the baking container 10, but the processed object C at the time of baking is configured by suppressing the generated oxygen from flowing into the baking container 10. The oxidation of silicon can be suppressed, and the formation of silicon nitride oxide can be suppressed.

  In this way, the workpiece C is baked, and silicon constituting the workpiece C reacts with nitrogen to generate silicon nitride. Firing is terminated when a desired fired product is obtained.

  According to the present embodiment, by suppressing the oxygen generated outside the firing container 10 from flowing into the firing container 10, the oxidation of the workpiece C during firing can be suppressed. As a result, the firing effect can be improved, so that a fired product made of silicon nitride excellent in heat resistance, toughness, and high quality can be obtained, and variation in the size of the sintered product can be suppressed. , Bearings, turbine blades, cutting tools and the like can be used with high reliability.

In the present embodiment, the atmospheric gas supplied from the gas supply source 5 can also use a non-oxidizing gas other than nitrogen. For example, a gas composed of at least one of nitrogen, hydrogen, and argon can be used.
In the present embodiment, silicon nitride is fired. However, a material that fires ceramic other than silicon nitride may be used as the workpiece C. For example, a material that fires sialon may be used as the workpiece C. Good.

  In the present embodiment, as shown in FIG. 3, the gas supply port 12 may be formed below the side surface of the baking container 10. The atmospheric gas from the gas supply source 5 is directly supplied to the firing container 10 via the gas supply pipe 3 extending from the gas supply source 5 to the gas supply port 12. The atmospheric gas supplied to the baking container 10 flows in the direction of the gas discharge port 13 through the inside of the baking container 10 on which the objects to be processed C are stacked in accordance with the flow rate of the atmospheric gas supplied from the gas supply source 5.

  Moreover, in this embodiment, as FIG. 4 shows, the gas supply port 12 may be formed in the upper surface of the baking container 10, and the gas exhaust port 13 may be formed in the lower side of the side surface of the baking container 10. FIG. The atmospheric gas from the gas supply source 5 is directly supplied to the firing container 10 via the gas supply pipe 3 extending from the gas supply source 5 to the gas supply port 12. The atmosphere gas supplied from above the firing container 10 is a gas discharge port formed below the inside of the firing container 10 in which the objects to be processed C are stacked according to the flow rate of the atmosphere gas supplied from the gas supply source 5. It circulates in 13 directions.

Embodiment 2
FIG. 5 shows the configuration of the ceramic firing apparatus according to the second embodiment. In the second embodiment, oxygen contained in the atmospheric gas supplied from the gas supply source 5 is removed, and a reducing agent 14 is disposed at the gas supply port 12.
The atmospheric gas from the gas supply source 5 arranged outside the firing furnace 1 is directly supplied into the firing container 10 through the gas supply pipe 3 and the reducing agent 14. At this time, oxygen contained in the atmospheric gas from the gas supply source 5 is removed by the reducing agent 14, and the atmospheric gas having a reduced oxygen concentration is supplied into the firing container 10. Thereby, the oxidation of the workpiece C can be further suppressed.
As the reducing agent 14, for example, carbon or titanium can be used.

In Embodiments 1 and 2 above, the heater 7 is installed on the ceiling portion of the firing furnace 1, but it is sufficient that the temperature of the firing chamber 2 can be raised. For example, it is installed on the side of the firing furnace 1. You can also.
Moreover, in Embodiment 1 and 2, since the mounting part 11 in the baking container 10 is comprised so that the to-be-processed object C may be stacked, many to-be-processed objects C can be baked simultaneously. However, when it is not necessary to fire a large number of workpieces C, the placement unit 11 may not be configured to be stacked.

  DESCRIPTION OF SYMBOLS 1 Firing furnace, 2 Firing chamber, 3 Gas supply pipe, 4 Gas discharge pipe, 5 Gas supply source, 6 Pressure adjustment valve, 7 Heater, 8 Container stand, 9 Pipe line, 10 Firing container, 11 Mounting part, 12 Gas Supply port, 13 Gas discharge port, 14 Reducing agent, C

Claims (10)

A ceramic firing method for firing a workpiece by placing a firing container in which the workpiece is placed in a firing furnace,
An atmosphere gas from a gas supply source arranged outside the firing furnace is directly supplied into the firing container from a gas supply port formed in the firing container,
A ceramic firing method, wherein the atmosphere gas supplied from the gas supply port is circulated in the firing vessel and discharged out of the firing vessel through a gas discharge port.   2. The ceramic firing method according to claim 1, wherein the atmospheric gas is supplied into the firing container from a bottom surface side of the firing container and is discharged out of the firing container from an upper surface side of the firing container.   2. The ceramic firing method according to claim 1, wherein the atmospheric gas is supplied into the firing container from an upper surface side of the firing container and is discharged out of the firing container from a lower surface side of the firing container.   The ceramic firing method according to claim 1, wherein the ceramic to be fired is silicon nitride.   5. The ceramic firing method according to claim 1, wherein the atmospheric gas is made of at least one of nitrogen, hydrogen, and argon.   The ceramic firing method according to claim 1, wherein the atmospheric gas is supplied into the firing container through a reducing agent disposed at the gas supply port of the firing container. A ceramic firing apparatus for firing a workpiece by placing a firing container in which the workpiece is placed in a firing furnace,
A firing container in which a gas supply port for supplying atmospheric gas to the inside and a gas discharge port for discharging the atmospheric gas to the outside;
A gas supply pipe for directly supplying the atmospheric gas from the gas supply source arranged outside the baking furnace into the baking container from the gas supply port;
A ceramic firing apparatus, wherein the atmosphere gas supplied from the gas supply port is circulated in the firing vessel and discharged from the gas discharge port to the outside of the firing vessel. A container base for placing the firing container at a lower portion in the firing furnace;
The gas supply port is provided on the lower surface of the baking container, the gas discharge port is provided on the upper surface of the baking container, and the gas supply pipe is provided so as to reach the gas discharge port through the inside of the container base. The ceramic firing apparatus according to claim 7, wherein the atmospheric gas is supplied directly into the firing container. It further has a placement part for placing the object to be processed in the baking container,
The ceramic firing apparatus according to claim 7 or 8, wherein the placement unit is installed so that the workpieces can be stacked.   The ceramic firing apparatus according to any one of claims 7 to 9, further comprising a reducing agent that reduces the atmospheric gas supplied into the firing container at the gas supply port of the firing container.

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