JPH09318270A - Heat treatment furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To purify inert gas fed into a treatment space by a method wherein getter material is effectively acted during sintering operation. SOLUTION: A sand seal section 3 having a getter material G is arranged at an inner box 2, gas generated in a processing space S1 when fat and gas are removed is discharged directly out of a furnace 1 through an inner discharging means 5 without being contacted with the getter material G, the gas is passed from an inter-furnace space S2 through the sand seal section 3 during sintering operation so as to remove impurities, and the inert gas with the impurities being removed is fed into the processing space S1. It is possible to prevent getter material G from being contaminated when the fat and gas are removed, assure an effective function during the sintering operation and keep a surrounding area around a processed item W in a high purity clean atmosphere.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high-purity atmosphere furnace,
The present invention relates to a heat treatment furnace that can be used as a vacuum sintering furnace, a sintering furnace for magnet sintering, and the like.

[0002]

2. Description of the Related Art For example, vacuum degreasing sintering is one of heat treatments. This vacuum degreasing and sintering mainly includes a degreasing step of removing the binder from the treated object by heating the treated object at a low temperature, and a sintering step of heating the treated object after degreasing to a high temperature to sinter the treated object. In order to consistently perform these degreasing sintering in a single furnace, after the binder generated from the processed material during the degreasing process in the furnace is sufficiently discharged to the outside of the furnace through the exhaust means. By introducing an inert gas such as Ar into the furnace space, a clean atmosphere is prepared before the sintering process. But simply with this approach,
Because O ₂ or H ₂ O remaining in the furnace at the transition stages in the sintering step can adversely affect the quality of the final product in contact with the treated product, the pre-treated, O ₂ or H ₂ It is placed in a container filled with a getter material having an adsorbing effect on O so that these getter materials capture O ₂ and H ₂ O when the sintering process is started.

[0003]

However, in such a countermeasure, the periphery of the object to be treated is covered with the getter material from the initial stage of the degreasing process. For this reason, the binder generated in the degreasing step cannot pass through the getter material and cannot be exhausted by the exhaust means. At that time, the binder comes into contact with and adheres to the surface of the getter material, and the sintering step is performed. At times, there is a disadvantage that the effect of adsorption of the getter material on O ₂ and H ₂ O is reduced. Not only that, however, since the amount of binder remaining on the getter material increases at the stage of transition to the sintering step, the residual amount of the binder increases, which is a factor that rather deteriorates the quality of the final product. Further, with such a configuration, since the inside of the inner box cannot be made airtight, there is a disadvantage that the interior space of the furnace is contaminated by the binder vapor. Furthermore, in such a case, it is necessary to prepare a container of a size to accommodate the processed material and to fill the getter material in the container, which unnecessarily narrows the processing space, resulting in space utilization efficiency. As a result, there is an inconvenience leading to a decrease in processing efficiency.

The present invention intends to newly provide a heat treatment furnace in which the quality of the final product can be effectively improved by effectively utilizing such getter material.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an inner box which is disposed in a furnace to close a processing space inside and an outer processing space inside the inner box. A seal portion having a minute gap formed at a position isolated from the furnace interior space and having a degree of allowing passage of gas, and a gas introduction system for introducing gas into the furnace interior space. In addition, the getter material is arranged in the minute gap of the seal portion, and the inner exhaust means for directly exhausting the processing space to the outside of the furnace is provided.

In such a structure, when an inert gas such as Ar is introduced through the gas introduction system into the furnace space from the stage of starting sintering, the gas existing in the processing space at the time of completion of degreasing / degassing is removed. It is replaced by the inert gas introduced into the furnace space, and since the inert gas flows into the processing space through the seal portion, it comes into contact with the getter material to adsorb O ₂ and H ₂ O, and thus is purified. Will be. For this reason,
When the sintering process or the like is started, it is possible to keep the surroundings of the processed product in a high-purity atmosphere. Moreover, in the degreasing / degassing process performed prior to the above-mentioned sintering process, if the exhaust of the processing space by the internal exhaust means and the introduction of gas into the furnace internal space by the gas introduction system are performed in parallel, Since the generated binder vapor and the like can be discharged to the outside of the furnace without passing through the getter material, it is possible to prevent the getter material from being contaminated by the binder and the like. Therefore, the amount of binder and the like remaining in the furnace can be suppressed to an extremely small amount at the stage of shifting to the sintering process. Of course, it goes without saying that such a seal portion enhances the airtightness of the inner box, and thus helps prevent contamination of the furnace by a binder or the like.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. The heat treatment furnace of this embodiment is provided with an inner box 2 which is disposed in the furnace 1 and closes a processing space S1 inside, and the inner box 2
A sand seal part 3 for separating the inner processing space S1 from the outer furnace space S2 with a granular material, a gas introduction system 4 for introducing gas into the furnace space S2, and the processing space S1 directly in the furnace An internal exhaust system 50 as an internal exhaust system means 5 for exhausting to the outside and a valve 51 are provided.

The furnace 1 has a heating chamber 13 surrounded by a heat insulating material 12 inside a furnace barrel 11, and a heater 14 is provided inside the heating chamber 13. By opening and closing the provided lid 11a together with the lid 12a provided on a part of the heat insulating material 12, the processed material W can be taken in and out. The furnace 1 is provided with a lid 11 after accommodating the processed material W.
An external exhaust system 6 for evacuating the inside of the furnace 1 by closing a and 12a is attached. The external exhaust system 6 has a configuration in which an oil diffusion pump 61, a mechanical booster pump 62, and an oil rotary vacuum pump 63 are arranged in series, and a valve 64 is arranged on the exhaust start side.

The inner box 2 is made of molybdenum, for example,
It is composed of a box body 21 that opens to the lower end side, and a lower lid 22 that is arranged in the opening portion of the box body 21, and is arranged in the center of the heating chamber 13. A groove 22a having a U-shaped cross section is provided along the outer edge of the lower lid 22, and the lower end of the peripheral wall 21a of the box main body 21 is hung in the groove 22a so that the lower wall of the box main body 21 and the lower wall of the box main body 21 are inserted. The sand seal portion 3 is formed between the lid 22 and the lid 22. Then, in the sand seal portion 3, the processing space S1 and the furnace space S2 are separated by a minute gap. Then, the groove 22a is filled with powder or granular getter material G, as shown by hatching in the drawing. As the getter material G, the processed material W
In addition to crushing and crushing the same material as Al ₂
Various light metals such as O ₃ , AlN, and BN, as well as Fe, Mg, Al, and Ti, which have an adsorbing effect on O ₂ and H ₂ O can be used. An exhaust hole 22x is provided in the central portion of the lower lid 22.

The internal exhaust system 50 has one end penetrating the furnace body 11 and the heat insulating material 12 and connected to the exhaust hole 22x of the lower lid 22, and the other end of the mechanical booster pump 62 which is a constituent element of the external exhaust system 6. It is connected to the suction side via a valve 51. The gas introduction system 4 has one end connected to the in-furnace space S2 inside the furnace barrel 11 and the other end connected to a gas supply source (not shown) via a valve 41. It is filled with an inert gas.

Next, a method of using this embodiment will be described. First, the lids 11a and 12a are opened, and the processing object W is set in the inner box 2. The processed product W may be freely put in and taken out together with the inner box 2, or the inner box 2 may be fixed to the furnace 1 so that only the processed product W is put in and taken out. Next, the lid 11a,
When the outer exhaust system 6 and the inner exhaust system 50 are actuated by closing 12a and the furnace internal space S2 and the processing space S1 reach a predetermined vacuum degree, the valve 64 of the outer exhaust system 6 is closed and at least the mechanical booster pump 62 and Oil rotary vacuum pump 63
In the state where the gas is being operated, this time, the valve 41 of the gas introduction system 4 is opened to introduce the inert gas into the furnace internal space S2, and the heater 14 is energized to heat the workpiece W at a low temperature (for example, 500 ° C.). Start C). As a result, in the furnace 1, the inert gas introduced into the furnace inner space S2 reaches the processing space S1 through the sand seal portion 3 of the inner box 2 as shown by the arrow in the figure, and further the inner exhaust system 50 is supplied. A gas flow is formed through which the gas is discharged to the outside of the furnace 1, and the binder vapor that evaporates from the processed material W along with this gas flow is sequentially generated in the furnace 1.
Directly discharged outside. When the degreasing is completed, the heater 14 is switched to a high temperature heating state of, for example, about 1400 ° C., and the sintering process for the processed material W is performed. At this time, the valve 51 of the inner exhaust means 5 is closed, and the inert gas is introduced through the gas introduction system 4 up to near atmospheric pressure.

In this case, the gas existing in the processing space S1 before the start of sintering is replaced by the inert gas introduced into the space S2 inside the furnace at the start of sintering,
Moreover, the inert gas always contacts the getter material G when flowing into the processing space S1 via the sand seal portion 3. At this time, the getter material G is activated by high temperature heating,
O ₂ or H ₂ O showed high adsorption properties relative to adsorb O ₂ and H ₂ O at a high efficiency from the inert gas passing through, to purify the gas. Since this kind of gas usually contains O ₂ and H ₂ O from the stage of being stored in the gas supply source not only during the transfer, but it is necessary to purify the gas just before introducing it to the target site. It is extremely effective in increasing the Therefore, when the sintering process is started, the periphery of the processed material W can be kept in a high-purity atmosphere. Moreover, in the degreasing process performed prior to the sintering process, the binder vapor generated from the workpiece W can be discharged to the outside of the furnace 1 without passing through the getter material G, and the getter material G is contaminated by the binder. The situation can be effectively avoided. Therefore, the amount of binder remaining in the furnace can be suppressed to an extremely small amount at the stage of shifting to the sintering process.

As described above, the heat treatment furnace of this embodiment is
Place the getter material G in a position that is not affected during the degreasing process
By doing so, the processed product W can be made to function effectively during sintering.
To O _TwoAnd H_TwoEffectively prevent impregnation with impurities such as O
can do. As a result, the quality of the final product remains
Excellent effect that can be significantly improved compared to
Is played. Of course, due to the sand seal part 3,
Since the airtightness of the box 2 is improved, the inside of the furnace is
It also helps prevent contamination during S2.

In addition to the functions and effects described above, in this embodiment, the size of the space occupied by the getter material G is basically independent of the size of the object W to be processed.
There is no inconvenience of unduly narrowing the space, and it is possible to effectively improve the space utilization efficiency and thus the processing efficiency. The specific configuration of each unit is not limited to that of the illustrated embodiment. For example, in the above embodiment, the sand seal part 3 filled with the getter material G is provided only between the furnace internal space S2 and the processing space S1, but as shown in FIG. 2, the start end of the internal exhaust system 50 is connected. It is also effective to provide the getter material G by providing the sand seal portion 6 according to the above embodiment between the exhaust hole 22x of the container 2 and the processing space S1. In this sand seal part 6, another groove 22b is provided inside the groove 22a of the lower lid 22, and a peripheral wall 23a hung from the table 23 on which the workpiece W is placed is inserted into this groove 22b. It is composed. By doing so, normally, as shown by the arrow in the figure, the flow of the gas in the processing space S1 is allowed so that the exhaust is not obstructed, and the internal exhaust system 50 is directed in the direction opposite to the arrow. Even if there is a backflow of gas from the side, the purity of the processing space S1 can be maintained by purifying the gas. Further, as shown in FIG. 3, the inner box 2 is doubled, and the gap between the box body 21 and the lower lid 22 is opened / closed by an operation from outside the furnace, and the inner exhaust means 5 is opened.
It can also be. In this case, at the time of degreasing and degassing, the inner box 2 is opened as shown in the drawing to remove the binder without passing the getter material G, and the getter material G is sealed at the time of sintering. further,
In each of the above embodiments, the material of the inner box 2 is not limited to molybdenum, and various metals, ceramics, graphite, and other materials capable of withstanding high temperatures can be selected. In the case of graphite, it is desirable to perform impermeable treatment in order to ensure the effective function of the sand seal part. Further, the starting end side of the inner exhaust system may be divided into a plurality of pieces by a manifold, a plurality of inner boxes may be arranged in the processing space, and the exhaust holes of the inner boxes may be connected to the corresponding manifolds. . According to this structure, cooling can be performed directly as compared with the case where a single large inner box is used, so that the cooling rate for the processed material can be effectively increased.

Other configurations can be variously modified without departing from the spirit of the present invention. For example, at the time of sintering, even if a so-called atmospheric pressure flow that introduces an inert gas having a pressure higher than the atmospheric pressure into the furnace space is provided with a valve that opens the internal exhaust system to the atmosphere, the same as in the above embodiment. It is possible to obtain the action and effect. Alternatively, the valve 64 of the external exhaust system 6 may be opened to perform vacuum sintering.

[0016]

The present invention is embodied in the form described above and has the following effects. That is, in the heat treatment furnace of the present invention, a seal portion having a getter material is provided in the inner box, and the gas generated in the processing space during degreasing and degassing is directly discharged to the outside of the furnace through the inner exhaust means without contacting the getter material. During the sintering, the inert gas after removing the impurities can be introduced into the processing space by passing through the seal portion from the furnace space. Therefore, it is possible to prevent the getter material from being contaminated during degreasing and degassing, to ensure an effective function during sintering, and to keep the periphery of the processed material in a high-purity, clean atmosphere. Therefore, according to the heat treatment furnace of the present invention, it is possible to significantly improve the quality of the final product as compared with the conventional one. Of course, since the airtightness of the inner box is effectively enhanced by such a seal portion, it also has an advantageous effect on prevention of contamination of the furnace internal space.

Further, according to the present invention, the getter material can be compactly arranged regardless of the size of the object to be processed, so that the processing efficiency can be effectively improved as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of an essential part corresponding to FIG. 1, showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view of an essential part corresponding to FIG. 1, showing still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Furnace 2 ... Inner box 3, 6, 7 ... Sand seal part 4 ... Gas introduction system 5 ... Inner exhaust means G ... Getter material S1 ... Processing space S2 ... Furnace inner space

Claims (1)

[Claims] 1. An inner box which is arranged in a furnace to close a processing space inside, and a gas which is formed at a position separating the processing space in the inner box from an outer furnace space to permit passage of gas. A seal portion having a minute gap to the extent possible, and a gas introduction system for introducing a gas into the furnace space, wherein a getter material is arranged in the minute gap of the seal portion, A heat treatment furnace provided with an internal exhaust means for exhausting the processing space directly to the outside of the furnace.