JP2001255070A - Vacuum heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high performance vacuum heat treatment capable of performing a processing for processed heavy weight item and showing a quite high air-tightness against a surrounding external part. SOLUTION: There are provided a vacuum container having a pressure reducing means for reducing an inner pressure; a rotary container having a horizontal rotary shaft installed in the vacuum container for use in storing processed items; a driving means for axially rotating the rotary container, wherein the rotary container is not fixed at its shaft part against the vacuum container, but it is installed within the vacuum container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum heating furnace used for treating, for example, a powder for hydrogen storage and a powder for nitriding.

[0002]

2. Description of the Related Art Vacuum heating furnaces are utilized in various fields in industrial production. Although the required performance and specifications differ depending on the field, generally, heating in a vacuum has an effect that a thermal reaction or a chemical reaction of an object to be processed can be performed under specific conditions.

[0003] The simplest structure of a vacuum heating furnace is one in which a heating means is provided inside a vacuum vessel capable of reducing pressure. An object to be processed is placed in the vacuum vessel, and pressure reducing means such as a pressure reducing pump is provided. Then, the inside of the vacuum vessel is depressurized to a predetermined degree of vacuum, and a high-frequency current is supplied to the induction coil as a heating means to heat the inside of the vacuum vessel and perform heat treatment without oxidizing the object to be processed. For example, this method is used for diffusion bonding between ceramic and metal. Further, a vacuum heating furnace as shown in FIG. 3 has been usually used to accelerate the processing of the object to be processed. The vacuum heating furnace shown in FIG.
The vacuum rotating container 3 is placed inside the heat holding container 33 with
0 is set. The vacuum rotating container 30 is provided with a shaft 11 at one end via a clutch 18,
Numeral 1 is fixed to the container 30 via a bearing 36a, and when the shaft 11 rotates, the vacuum rotary container 30 is rotated. A decompression tube 31 for decompressing the inside of the vacuum rotary container is fixed to the other end side.
Is fixed via a bearing 36b similarly to the shaft 11. The decompression tube 31 is provided with a filter 35 so that the object to be processed is not sucked in.
Since it is fixed to 0, it rotates at the same rotation speed as the vacuum rotary container 30. Further, the weight of the vacuum rotary container is prevented from being concentrated only on the shaft 11 and the heat reducing tube 31 by the auxiliary unit 34. However, if a decompression mechanism such as a heat reduction tube is rotated, the airtightness is deteriorated somewhere in the rotation mechanism, and the degree of vacuum is easily damaged.

Japanese Patent Application Laid-Open No. Hei 6-207229 discloses a method of separating plated iron scrap into plated metal and iron. This iron scrap processing furnace has a vacuum vessel equipped with a vacuum exhaust device, a cylindrical body arranged in the vacuum vessel with its axis oriented in the horizontal direction, and supported rotatably about the axis, and a cylindrical body rotated. It mainly has a rotation drive mechanism for causing the heating and a heating device for heating the inside of the cylindrical body. Further, iron scrap is introduced from one end side of the cylindrical body while maintaining the degree of vacuum inside the vacuum vessel, and the inside of the cylindrical body is heated to evaporate plating metal attached to the iron scrap. As an effect, it is described that since the heat treatment is performed in a vacuum, it can be evaporated at a temperature lower than the melting point at atmospheric pressure. Further, it is disclosed that by making the cylindrical body rotatable, the iron scrap is constantly stirred and the whole is uniformly heated.

[0005] In addition, after the air in the vacuum vessel is exhausted to a high vacuum instead of merely in a vacuum, the atmosphere is replaced with an atmosphere of argon, nitrogen, and hydrogen, and then heated, and the atmosphere in the vacuum furnace is treated with the atmosphere to be treated. The use of a vacuum heating furnace that performs a treatment by reacting with a substance also accounts for a large proportion. One example of the vacuum heating furnace is disclosed in JP-A-7-188713. The vacuum heating furnace disclosed therein includes a raw material holding unit that holds a rare earth raw material, a heating device that includes a heating chamber that heats the raw material holding unit, and a hydrogen gas supply that supplies hydrogen gas to the heating chamber. A vacuum heating device including an apparatus and an exhaust device for reducing the pressure in a heating chamber is disclosed. This vacuum heating device first holds the rare earth material divided into a plurality of material holding portions, puts the plurality of material holding portions into a heating chamber, heats and stores the hydrogen fed into the heating chamber into the rare earth material, and thereafter It is possible to reduce the pressure in the heating chamber by the exhaust device and to perform dehydrogenation treatment from the rare earth material. In addition, the rare earth material for the magnet is basically used as a lump having a diameter of about 30 mm. The material holding portion is divided into a plurality of parts so that the reaction can be easily performed, and a rotatable structure is provided to reduce the rare earth material hydrogen and hydrogen. It is described that the reaction can be enhanced.

[0006]

In the above-mentioned production method, the rotating means of a container (hereinafter referred to as a rotary container) for carrying out heat treatment while stirring the raw materials is different from each other. However, when the rotating container is fixed to the vacuum container with the rotating shaft portion, it is difficult to adopt a high-vacuum vacuum heating furnace. Normally, the rotating container has a substantially cylindrical shape, but a slight deformation occurs during the heat treatment in the vacuum container. The center of gravity goes wrong due to the deformation, but if the rotating container is fixed with the rotating shaft,
Vibration occurs during rotation. In particular, in the case of processing a large amount of objects to be processed at once, even if the rotating shaft is fixed at both ends of the rotating container, the rotating shaft is slightly shifted due to its own weight, and the problem of vibration and noise occurs. Further, the vibration lowers the airtightness of the vacuum container, which is not preferable. Further, when the driving means for the rotary container is provided on the extension of the rotary shaft from the outside of the vacuum container, this vibration directly affects the sealing mechanism for transmitting the driving force provided in the vacuum container, which is a problem.

[0007]

As described above, there is room for further study on improving the vibration and noise caused by the deformation of the rotating container during the heat treatment while maintaining a high vacuum degree. The present invention, as a result of examining the solution of these problems, has come to find a vacuum heating furnace which can easily maintain high airtightness even with a rotating container therein and has low noise. In other words, the present invention provides a vacuum container, a rotating container for putting an object to be processed whose rotation axis is horizontal in the vacuum container, a driving unit for rotating the rotating container, an air in the vacuum container and the object to be processed. And a replacement means for replacing the reaction gas with a reaction gas for reacting with the reaction vessel, wherein the rotary vessel is installed in the vacuum vessel in a structure not fixed to the vacuum vessel by a shaft portion.

Further, the rotating container is provided so that the rotating shaft is in a horizontal direction, and the driving unit is provided so as to transmit a rotating force to a cylindrical curved surface portion of the rotating container. It is characterized in that it is provided only for With such a structure, even if the rotating container is slightly deformed due to heating, the rotating container only rotates above the driving unit, and it is easy to maintain high airtightness as compared with the one fixed by the rotating shaft. Becomes Further, since the driving mechanism can be simplified, it is suitable for processing a heavy object to be processed.

It is preferable that the rotary container is detachable from the vacuum container. When powder or the like is treated in a vacuum heating furnace as a treatment agent, it is necessary to perform internal cleaning after the treatment. It is very important to clean the rotating container when the object to be processed is not limited to the same object to be processed, or when the object to be processed deteriorates in air atmosphere. If it is not detachable, the powder is easily scattered during cleaning, and the powder easily adheres to the inner wall of the vacuum container. Since the vacuum container requires a fine structure for sealing the air with the outside, it is not preferable to adhere even a fine powder. In addition, contamination is more likely to remain than when the rotary container itself is cleaned, which is not preferable because it is mixed as impurities when other objects to be processed are processed. In the present invention, the term "removable" means a device that does not require any special operation, and has a broad meaning that the device can be easily removed without partially disassembling the vacuum container or the driving unit.

Further, as a form of a driving unit for rotating the rotary container, as shown in FIG. 1, the driving unit is disposed above the rotary container at two places in the cross section of the rotary shaft of the rotary container, and the rotational force of the driving unit is substantially reduced. It is preferred that the shape be transmitted to the rotating container by rolling contact. With the above structure, it is possible to rotate even if the rotating container is slightly deformed by the heat treatment. In addition, since the rotating container is placed on the driving unit, there is no need to fix the rotating container and the vacuum container via the driving unit. If a damper is provided between the drive unit and the vacuum vessel to absorb vibrations, it is possible to obtain better airtightness, and furthermore, the drive mechanism is not complicated, and the generation of noise can be reduced.

With the above configuration, 100 kg
It is possible to process a large number of objects to be processed at one time. In addition, the structure, which is a rotating body, has good heat uniformity. In addition, since a high vacuum state is easily maintained, a high-performance product can be obtained by treating an object to be oxidized, for example, a magnetic powder for a rare earth magnet.

An example which does not correspond to the present invention in which the rotating container is fixed to the vacuum container by a shaft portion will be described below. In FIG. 2, components other than the vacuum container 1 and the rotary container 2 are the same as those in FIG. For example, as shown in FIG. 2 (a), a shaft 11 communicates with the outside via a seal portion 12a provided on the vacuum container 1 on the axis of the rotary container, and the behavior of the rotary container directly affects the seal portion. As shown in FIG. 2 (b), a fixing member 14 having an extending portion 13 that rotates with the rotating container 2 and communicating with the outside of the vacuum container via a seal 12 b. Some have no fixed part. Further, as shown in FIG. 2C, even when the driving force is transmitted from the curved surface of the rotating container,
If three or more places, such as 4e, in addition to the driving parts 4a, 4c, come into contact with the curved surface part, the rotating container is fixed to the vacuum container, which is not preferable.

In particular, the present application is desirably used for preparing a powdery object to be processed, for example, a rare earth magnet raw material, which needs to suppress the reaction with the outside air. It is a well-known fact that oxygen corresponds to impurities in rare earth magnets. By using the vacuum heating furnace of the present invention, it is possible to process a large number of workpieces at once, and to maintain a high degree of vacuum, so that it is possible to produce a high-performance magnet raw material with reduced oxidation and further a magnet. is there.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of an essential part showing a vacuum heating furnace for integral use of the present invention. The vacuum container 1 for isolating from the atmosphere includes a main body 1b and a lid 1a, and by opening and closing the lid 1a, it is possible to work inside the vacuum container, and to perform vacuum and heating. This vacuum vessel has a pressure reducing means for reducing the pressure inside the vacuum vessel by a vacuum pump 7 through a seal part 21 and a replacement means having a valve 9 for sending a reaction gas for reacting the object to be processed from a cylinder 8 via a seal part 22. , And is automatically controlled so that the reaction gas can be sent while maintaining a predetermined degree of vacuum. Further, a plurality of heating means 17 for heating the inside of the vacuum vessel 1 are provided, and control of temperature rise, temperature holding, and temperature drop is possible.

Next, the structure of the driving means will be described. Inside the vacuum vessel 1, there are provided rotating shafts 15a and 15b whose both ends are fixed in parallel by bearings. An electric motor 6 for driving shaft rotations 15a, 15b from one end of the vacuum vessel 1 to one end of the rotation shaft 15a.
Are connected. The bearing at the other end is fixed to the vacuum vessel via a damper 3. A drive shaft 16 extending from the electric motor 6 includes rotating shafts 15a, 1
The drive shaft 16 is connected to the drive shaft 5b via a transmission mechanism 10, and the drive shaft 16 is kept airtight between the inside of the vacuum vessel 1 and the outside air by a seal portion 23. Drive units 4 a, 4 b, 4 for transmitting a driving force to the rotary container 2 are further provided on the drive shaft 16.
c and 4d (4d is omitted in the drawing) are provided, and they form a driving means in conjunction with each other. FIG. 1B is a cross-sectional view taken along the line AA of FIG. As shown in the figure, two rotating shafts 15a and 15b are provided in parallel in the vacuum vessel 1 and each rotate in the same direction.

The rotating container 2 is placed on the driving section 4 of the driving means. The rotating container 2 has a substantially cylindrical shape as described above, and the rotating force of the driving unit 4 is transmitted by frictional force and rotates. In order to prevent the curved surface portion of the rotating container 2 from being shifted in the axial direction with respect to the driving portion, a measure for preventing a deviation such as a rail is used.
A hole is provided on the side surface of the rotary container 2 so that the atmosphere and pressure in the vacuum container 1 and the rotary container 2 are the same. Since the rotating container 2 is placed on two driving units (the driving units 4a and 4c in the figure) in a predetermined cross section of the rotating container 2, even if the rotating container is slightly deformed, the sealing property of the vacuum container itself is impaired. There is no. In this embodiment, in order to make it detachable, the structure is such that the rails are provided only slightly wider than the drive unit. Further, a projection 5 for promoting the reaction of the object to be processed is provided inside the rotary container 2. FIG.
In (b), the shape is formed into a curved shape, but the shape, the length, and the like are not particularly limited, and may be appropriately selected.

Example 1 An object to be processed was subjected to vacuum heating using a vacuum heating furnace having the above structure. 130 kg of the powdery object to be processed was sealed in a rotary container. The rotating container was installed above a driving unit arranged in a vacuum container. The lid of the vacuum container was closed, and the outside air was completely separated from the inside of the vacuum container. Next, the pressure inside the vacuum vessel was reduced to 0.01 Pa in 30 minutes by a vacuum pump, and then the vacuum pump was stopped to maintain the degree of vacuum. Next, the valve was opened, a predetermined amount of nitrogen in the cylinder was filled in the vacuum vessel, and the valve was closed. Next, the power of the electric motor was turned on, and the drive unit was rotated via the drive shaft, the transmission mechanism, and the rotation shaft. The rotation speed of the drive unit was maintained so that the rotation speed became 10 rpm with respect to the rotating container. Next, the inside of the vacuum vessel was heated for 5 minutes by heating means for 5 minutes.
Heated to 00 ° C. Vacuum heat treatment was performed for 10 hours while maintaining the temperature inside the vacuum container and the rotation speed of the rotary container. Then, within 2 hours, the temperature inside the vacuum vessel was cooled to nearly room temperature. Thereafter, the nitrogen atmosphere inside the vacuum vessel was eliminated, and the rotating vessel was taken out. The object to be processed was taken out of the rotating container, and then the rotating container was cleaned. During this time, the leak amount between the vacuum vessel and the outside air is 3 × 10 ^−4.
Pa · M / sec or less.

(Embodiment 2) After performing the work of Embodiment 1,
A vacuum heat treatment was performed in the same manner as in Example 1 except that the object to be processed had a different composition and the replacement gas in the vacuum vessel in the cylinder was NH ₃ . As in Example 1, the leak amount between the vacuum vessel and the outside air was 3 × 10 ⁻⁴ Pa · M / sec or less. Further, no mixture of the composition of the object to be processed in Example 1 was observed.

(Comparative Example 1) A comparison was made using a vacuum heating furnace having a conventional structure. A vacuum heating furnace having the structure shown in FIG. 2A was used. In this vacuum heating furnace, the shaft 1
1 and the rotating container 2 are detachable by a clutch 18, but the shaft portion is fixed during rotation. The shaft 11 is rotated by an electric motor, and the rotating container rotates accordingly. Seal part 1 between shaft 11 and vacuum vessel
Sealed by 2a, the airtightness between the outside air and the inside of the vacuum vessel is maintained. Although not shown, the multi-end side of the vacuum heating furnace also has substantially the same structure, but the shaft and the rotating container are fixed on that side and are not removable. The vacuum vessel and the rotating vessel were of substantially the same size as in Example 1. Vacuum heat treatment was performed using this vacuum heating furnace. The object to be processed and the vacuum heating conditions were the same as those in Example 1.
The same as above. When the leak amount between the vacuum vessel and the outside air was measured, the leak amount was more than 3 × 10 ⁻⁴ Pa · M / sec, and strict airtightness could not be maintained. The shaft is fixed to the axis of the rotating container,
It is considered that the vibration due to the subtle deformation of the rotating container is transmitted to the shaft as it is and affects the seal portion.

[0020]

As described above, according to the present invention, it is possible to process a large weight object at a time, and to provide a high-performance vacuum heat treatment with extremely high airtightness to the outside. We were able to. Thus, heating, nitriding, and hydrogenation can be performed in a desired atmosphere that does not contain impurities such as oxygen, and high vacuum and high uniformity can be maintained, so that a raw material having high characteristics can be manufactured. Further, even in a vacuum heating furnace which tends to have a complicated structure, cleaning is easy because the structure is simplified, and contamination of impurities can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an example of the present invention.

FIG. 2 is a cross-sectional view of a main part showing a conventional configuration that does not correspond to the present invention.

FIG. 3 is a sectional view of an essential part showing an example of a conventional vacuum heating furnace.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vacuum container, 2 rotating containers, 3 dampers, 4 driving parts, 5 protrusions, 6 electric motors, 7 vacuum pumps, 8 cylinders, 9 valves, 15 rotating shafts, 16 drive shafts, 17 heating means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F27D 7/06 F27D 7/06 B F-term (Reference) 4K061 AA07 BA00 CA16 CA21 DA05 EA07 FA12 FA14 GA02 GA03 GA04 4K063 AA05 AA16 BA01 BA15 CA03 DA13 DA19 DA22 DA32 DA33 DA34

Claims (4)

[Claims] 1. A vacuum vessel provided with a decompression means for decompressing the inside, a rotary vessel installed in the vacuum vessel for containing an object whose rotation axis is horizontal, and a rotary vessel rotating And a driving means for causing the rotating vessel to be fixed to the vacuum vessel by a shaft portion, and the rotating vessel is installed in the vacuum vessel. 2. The rotating container has a substantially cylindrical shape, the rotation axis is in a horizontal direction, and a driving unit transmits a rotating force to a cylindrical curved surface of the rotating container, and is lower than the rotation axis of the rotating container. The vacuum heating furnace according to claim 1, which is provided only in the section. 3. The vacuum heating furnace according to claim 1, wherein the rotary container is detachable from the vacuum container. 4. The driving unit is disposed above the rotating container at two positions in a part of the axial cross section of the rotating container, the driving unit has at least a cylindrical shape, and the rotational force of the driving unit is substantially caused by rolling contact. The vacuum heating furnace according to claim 2 or 3, which is transmitted to a rotating container.