JP2871111B2 - Cooling method in vacuum furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-chamber for heating an article to be processed in a vacuum state and a main heating for heating the article to be processed in a higher vacuum than the front chamber and a higher temperature than the front chamber. Room,
The front chamber has an inlet for receiving the article to be processed, the main heating chamber has an outlet for sending out the article to be processed, and the front chamber and the main heating chamber move the article in the front chamber to the main heating chamber. In a vacuum furnace connected via a door that can be opened and closed, the workpiece heated in the main heating chamber is sent out from the main heating chamber, and then the main heating is performed to put the workpiece in the front chamber into the main heating chamber. The present invention relates to a cooling method in a vacuum furnace for cooling a chamber.

[0002]

2. Description of the Related Art In a vacuum furnace as described above, there is an effect that heating of a workpiece in a front chamber and heating of a workpiece in a main heating chamber can be performed with good continuity. In the course of such heating, when the article to be treated in the front chamber is transferred to the main heating chamber after the article to be treated is sent out from the main heating chamber, the article to be treated is suddenly exposed to the high temperature in the main heating chamber. In order to prevent this, the main heating chamber is cooled to the same temperature as the front chamber. In the case of the cooling, conventionally, a method of cooling by leaving the main heating chamber in a vacuum state has been performed.

[0003]

In the conventional cooling method in a vacuum furnace, there is a problem that it takes a long time to lower the temperature of the main heating chamber to a predetermined temperature, thereby lowering the operating rate of the vacuum furnace. In addition, when introducing gas into the main heating chamber and trying to cool it, the gas leaks into the front chamber and deteriorates the vacuum state there. When an article is placed in the main heating chamber, the article to be treated comes into contact with the gas in the main heating chamber, causing a problem that the quality is deteriorated.

The present invention has been made to solve the above-mentioned problems (technical problems) of the prior art, and prevents leakage of hydrogen, helium or a gas containing them from the main heating chamber to the front chamber. By introducing the main heating chamber to the main heating chamber at a pressure within the range and cooling the main heating chamber, the main heating chamber can be cooled to a predetermined temperature in a short time, and even if such gas is introduced,
An object of the present invention is to provide a cooling method in a vacuum furnace, which can prevent deterioration of a vacuum state in a front chamber and prevent deterioration of quality of a processing target when a processing target in the front chamber is put into a main heating chamber. And

[0005]

Means for Solving the Problems To achieve the above object, a cooling method in a vacuum furnace according to the present invention comprises a front chamber for heating a workpiece in a vacuum state, and A main heating chamber for heating to a higher temperature than the front chamber in a high vacuum state, and the front chamber has an inlet for receiving the article to be processed, while the main heating chamber has an outlet for sending out the article to be processed. The front chamber and the main heating chamber are mainly heated in the main heating chamber in a vacuum furnace connected via an openable / closable door in order to transfer the workpiece in the front chamber to the main heating chamber. After cooling out the main heating chamber after sending it out of the chamber, the hydrogen, helium or gas containing them leaks from the main heating chamber to the front heating chamber when cooling the main heating chamber to put the workpiece in the front chamber into the main heating chamber. Is introduced into the main heating chamber at a pressure within the range where .

[0006]

The object to be treated is placed in the front chamber, where it is heated in a vacuum. Subsequently, the workpiece is transferred to a main heating chamber where it is heated to a higher temperature in a higher vacuum. Thereafter, the article heated in the main heating chamber is sent out from the main heating chamber.

After the article to be processed in the main heating chamber is sent out as described above, the next article to be processed in the front chamber is transferred to the main heating chamber in the following manner. After the article to be processed is sent out from the main heating chamber, hydrogen, helium, or a gas containing them is introduced into the main heating chamber. The main heating chamber is rapidly cooled by the convection of these gases. When the temperature of the main heating chamber reaches the same level as that of the front chamber, the door is opened, and the article to be processed in the front chamber is moved to the main heating chamber.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. In FIG. 1, reference numeral 1 denotes a vacuum furnace, which is a front chamber 2 (also called a preheating chamber) and a main heating chamber 3 (also simply called a heating chamber).
And a cooling chamber 4. The front chamber 2 has an entrance 5 for receiving the article to be treated, and is provided with a door 7 operated by an opening / closing device 6. Further, a heater 8 for heating the article to be processed A, for example, an electric heater is provided therein, and the front chamber 2 is connected to a vacuum exhaust device (not shown). The space between the front chamber 2 and the main heating chamber 3 and the space between the main heating chamber 3 and the cooling chamber 4 are partitioned by partition walls 10 and 11, respectively. The partition 10 has an inlet 12 through which the article A to be treated in the front chamber 2 is introduced into the main heating chamber 3.
Is provided on the partition 11, and the processing target A in the main heating chamber 3 is provided.
An outlet 13 is provided for taking the air into the cooling chamber 4. The entrances 12 and the exits 13 are provided with doors 15, 17 operated by opening and closing devices 14, 16, respectively. Those doors 1
Since the main heating chamber 3 is operated in a higher vacuum state than the front chamber 2 or the cooling chamber 4, the inlets 12 and the outlets 13 are closed from the front chamber 2 or the cooling chamber 4 side. . Inside the main heating chamber 3, a heat insulating wall 18 is provided to heat the article to be processed A to a higher temperature than the front chamber 2. Inlet part 19 and outlet part 20 of the heat insulating wall 18
Are attached to the doors 15 and 17, respectively, and open and close integrally with the doors 15 and 17. Reference numeral 21 denotes a heater for heating the article to be processed, for example, an electric heater. The main heating chamber 3 is connected to a well-known vacuum exhaust device (not shown). Next, the cooling chamber 4 is the outlet 2
3 provided with a door 25 operated by an opening / closing device 24. Reference numeral 26 denotes a fan for stirring the cooling gas in the cooling chamber 4. The cooling chamber 4 is connected to a gas supply means (not shown) for supplying a cooling gas. Next, reference numeral 27 denotes a conveying means provided through the front chamber 2, the main heating chamber 3, and the cooling chamber 4, and uses, for example, a roller hearth.

The above-described vacuum furnace 1 is used, for example, for sintering a powder metal molded product. An article A to be treated, for example, a powdered metal molded article, is first put into the front chamber 2 and is placed therein, for example, for 10 minutes.
^The substrate is heated to, for example, about 600 ° C. in a vacuum of about ⁻³ Torr to perform dewaxing. Next, the article to be processed A is put into the main heating chamber 3 and heated to a higher temperature than the front chamber, for example, 1200 ° C. in a vacuum state higher than that of the front chamber 2, for example, about 10 ⁻⁵ Torr. Then, sintering of the powder metal is performed. When sintering is completed, the product A
Is placed in a cooling chamber 4 where it is cooled to a normal low temperature and then discharged from outlet 23.

In the above-described operation, the article A heated in the main heating chamber 3 is sent out from the main heating chamber 3 and then the next article A in the front chamber 2 is transferred to the main heating chamber 3. In transferring, the inside of the main heating chamber 3 is cooled as follows.
That is, when the doors 15 and 17 are closed, the main heating chamber 3 is closed.
An atmosphere gas for cooling is introduced therein. As the atmosphere gas, a gas having a high cooling effect even under a relatively low pressure,
For example, hydrogen, helium, or a gas containing them is used. The pressure to be introduced is within a range where the leakage of the atmospheric gas from the main heating chamber 3 to the front chamber 2 or the cooling chamber 4 is prevented, that is, within a range where the doors 15 and 17 are kept in a sealed state. The pressure is set to, for example, 200 Torr or less. The main heating chamber 3 is left in a state where such a gas is introduced, and the main heating chamber 3 is cooled. In this case, the main heating chamber 3 is rapidly cooled by the convection of the introduced atmospheric gas. By such cooling, the temperature in the main heating chamber 3 becomes
When the temperature becomes about the same as the inside temperature, the door 15 is opened and the front room 2 is opened.
The article to be processed A is moved into the main heating chamber 3.

Next, FIG. 2 shows an example of a change in the temperature in the main heating chamber 3. When the article A in the front chamber 2 is introduced into the main heating chamber 3, the temperature is, for example, about 600 ° C. It is. After the article A is transferred, the heating of the main heating chamber 3 is started, and reaches a temperature of 1200 ° C. in about 60 minutes, for example. In that state, for example, it is held for 90 minutes. After the article to be processed A is sent out as described above, the atmospheric gas is introduced as described above, and the main heating chamber 3 is cooled, for example, for about 60 minutes. This time is, as in the prior art, the main heating chamber 3
This is a time significantly shorter than the time required for cooling to 600 ° C. (temperature change indicated by a dashed line) by leaving the device in a vacuum state.

In the above-described processing, for example, as shown in FIG. 3, depending on the article to be treated, the article is held at a temperature of 1200 ° C. for a predetermined time in the main heating chamber, gradually cooled to a predetermined temperature, and then treated.
Is sent out from the main heating chamber, and then the ambient gas is introduced into the main heating chamber 3 to cool the main heating chamber 3.
Further, depending on another article to be treated, after the article to be treated is cooled in the main heating chamber 3 as shown in FIG. The chamber 3 can be cooled, and when the atmospheric gas in the main heating chamber 3 is insufficient, the processing object A is sent out from the main heating chamber 3 and then the atmospheric gas is further introduced into the main heating chamber 3 to supply the main gas. The heating chamber 3 can be cooled. In addition to the above, various heating conditions are widely applied as the heating conditions of the article to be processed in the main heating chamber 3 of the present invention.
Further, it is desirable that the gas pressure introduced into the main heating chamber is lower than the pressure in the front chamber (high vacuum state), but exceeds the force from the opening / closing device that operates the door between the front chamber and the main heating chamber 3. If there is no pressure, the effect of the present invention can be obtained.

Next, an example of the type, the pressure, and the time required for the cooling as described above of the atmosphere gas will be described. For example, hydrogen gas is used for 10 minutes at 10 Torr, and helium gas is used for 7 minutes.
It is 60 minutes in Torr. By the way, in case of nitrogen gas 8
It is 60 minutes at 0 Torr.

[0014]

As described above, according to the present invention, after the article A heated in the main heating chamber 3 is sent out from the main heating chamber 3, the article A in the front chamber 2 is mainly removed. When the main heating chamber 3 is cooled down to the same temperature as the temperature in the front chamber 2 to enter the heating chamber 3, gas is introduced into the main heating chamber 3, so that convection occurs in the main heating chamber 3. This has the effect of cooling to a predetermined temperature in a short time.

In addition, even when the gas is introduced as described above, since hydrogen, helium or a gas containing them is used as the gas, even if the gas pressure is low, a large cooling effect by the convection can be brought about. Thus, there is an effect that the cooling can be shortened in a state in which gas leakage from the main heating chamber 3 to the front chamber 2 is prevented.

Furthermore, since the above-mentioned gas is used, when the article A in the front chamber 2 is put in the main heating chamber 3, even if the above-mentioned gas is present therein, the article A There is no effect of the above-mentioned gas on the object A, and there is also an effect that the quality of the article A to be treated can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a vacuum furnace.

FIG. 2 is a graph showing an example of a temperature change in a main heating chamber.

FIG. 3 is a graph showing a different example of a change in the temperature of the main heating chamber.

FIG. 4 is a graph showing still another example of a temperature change in the main heating chamber.

[Explanation of symbols]

 A Products to be processed 1 Front room 3 Main heating room 15 Door

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C21D 1/773 F27D 7/06 B22F 3/10 F27B 5 / 04,9 / 04,14 / 04

Claims (1)

(57) [Claims] A first chamber for heating the article to be processed in a vacuum state; and a main heating chamber for heating the article to be processed in a higher vacuum than the front chamber and at a higher temperature than the front chamber, The front chamber has an inlet for receiving the article to be processed, the main heating chamber has an outlet for sending out the article to be processed, and the front chamber and the main heating chamber move the article in the front chamber to the main heating chamber. In a vacuum furnace connected via a door that can be opened and closed, the workpiece heated in the main heating chamber is sent out from the main heating chamber, and then the main heating is performed to put the workpiece in the front chamber into the main heating chamber. In cooling the chamber, hydrogen, helium or a gas containing them is introduced into the main heating chamber at a pressure within a range that prevents leakage from the main heating chamber to the front chamber, thereby cooling the main heating chamber. A cooling method in a vacuum furnace.