JPH11311483A - Heat-treatment furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent the inside of a furnace from being contaminated by the diffusion of a binder. SOLUTION: A middle room 21b that is closed down on fitting and is opened on departure is provided on the contacting surface of a tight box body 321 that can attach or detach a lid 21, gas is introduced to the middle room 21b via a gas introduction system 4, and at the same time the gas is evacuated via an inner exhaust system 2 for directly evacuating a treatment space S1 inside the tight box 2 and an outer exhaust system 5 for evacuating a space S2 in a furnace outside the tight box 2, thus evacuating paraffin or the like that are diffused and leaked temporarily toward the side of the space S2 in the furnace from the treatment space S1 through the gap between a lid 21 and a body 22 of the tight box 2 without returning it to the treatment space S1 again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vacuum degreasing sintering furnace,
The present invention relates to a heat treatment furnace that can be used as a purification furnace, a MIM furnace, a brazing furnace, and the like.

[0002]

2. Description of the Related Art A degreasing and sintering process mainly includes a degreasing step of removing a binder from a treated material by heating the treated material at a low temperature and a sintering step of firing the treated material by heating the treated material after degreasing at a high temperature. In recent years, since degreasing and sintering are performed consistently in a single furnace, there are many arrangements that prevent in-furnace contamination during degreasing. Specifically, a main body having an opening disposed in the furnace, and a tight box capable of closing the processing space inside by a lid which is detachably abutted on the opening, and the processing space is directly connected to the tight box. 2. Description of the Related Art There is known an internal exhaust system capable of exhausting gas to the outside of a furnace and a gas introduction system for introducing gas into the furnace. In other words, this process evacuates the processing space side through an internal exhaust system while introducing gas into the furnace, and performs degreasing, so that the processing space is relatively positioned with respect to the furnace space outside the tight box. Keeping the pressure low, the binder vapor generated from the processed material in the processing space is directly discharged from the furnace space to the outside of the furnace together with the gas flowing into the processing space through the contact gap between the body of the tight box and the lid, The furnace space is protected from contamination. Thus, in the subsequent sintering process, the processing can be performed in a clean atmosphere in which no binder remains in the furnace.

[0003]

Generally, in the degreasing step, the lower the pressure in the processing space, the more the binder evaporates, and the shorter the degreasing time. For this purpose, degreasing may be advanced by reducing the amount of gas introduced. However, in this case, the evaporated binder leaks into the furnace space through a gap between the body of the tight box and the lid by diffusion, and adheres to the furnace wall and the like. For this reason, in the subsequent sintering step, the binder evaporates again, flows into the processing space, and contaminates the processed material.

An object of the present invention is to effectively eliminate such inconveniences.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a heat treatment furnace having a general structure as a heat treatment furnace of this kind. An intermediate chamber which is closed at the time of mounting and is opened at the time of detachment, guides gas to the intermediate chamber through a gas introduction system, and exhausts the gas to the inner exhaust system and the furnace space outside the tight box. The exhaust gas is exhausted by an external exhaust system provided in the apparatus.

With such a configuration, even if the furnace space is contaminated, by heating the processed material and increasing the amount of gas introduced into the intermediate chamber via the gas introduction system thereafter, Part of the gas introduced into the intermediate chamber enters the processing space through the gap between the lid and the main body, is exhausted by the internal exhaust system, and the other enters the furnace internal space, and is exhausted by the external exhaust system. Will be done. Therefore, even if the binder adhering to the furnace wall etc. re-evaporates in the furnace space,
This can effectively prevent a problem that flows into the processing space again.

[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 used, for example, in a degreasing / sintering step, which is one of the steps in manufacturing a metal injection molded product, and is disposed in a furnace 1 and processed inside as shown in FIG. A tight box 2 for closing the space S1, an inner exhaust system 3 for directly exhausting the processing space S1 out of the furnace 1,
A gas introduction system 4 for introducing a gas from outside the furnace 1 into the furnace 1 is provided.

More specifically, the furnace 1 has a heating chamber 13 surrounded by a heat insulating material 12 inside a furnace body 11, and a heater 14 is provided in the heating chamber 13.
Of the heat insulating material 12 and the lid 2 of the tight box 2
The cover 12a is opened together with the cover 22 at the time of cooling by being opened and closed by the cylinder 10 together with the cover 2.

The tight box 2 is made of graphite disposed in the heating chamber 13 and is detachably brought into contact with a cylindrical or rectangular cylindrical main body 21 at a position where both ends of the main body 21 are closed. The lid 22 is supported by the lid 12a, and is pushed in a direction to close the lid by a spring force so as to close the processing space S1.

The internal exhaust system 3 has one end 3a penetrating through the furnace body 11, the heat insulating material 12 and the tight box body 21 and connected to the processing space S1, and the other end having a valve 31, a trap 32, a mechanical booster pump 33 and a rotary. It is open to the atmosphere via a pump 34. The gas introduction system 4 has one end 4
a through the furnace body 11 and the heat insulating material 12
The other end 4 b is connected to a gas supply source 42 via a valve 41. This gas supply source 42 has N
A gas such as ₂ or Ar is prepared and can be selectively connected to the gas introduction system 4.

In this embodiment, the present embodiment further includes grooves 2 on the abutting surfaces of both open ends of the tight box body 21 to which the right and left lids 22 of the tight box 2 are attached and detached.
1a, an intermediate chamber 21b which is closed when the lid 22 is mounted and opened when the lid 22 is detached is formed inside the groove 21a. Then, the above-described gas introduction system 4
One end 4a is connected to the center of the tight box main body 21 and a passage 21c is formed inside the tight box main body 21 so as to extend in the axial direction and communicate the one end 4a to the intermediate chamber 21b. The gas introduced via the introduction system 4 can be guided to the intermediate chamber 21b.

In this heat treatment furnace, one end 5a is connected to the furnace body 1
1 and connected to the furnace space S2 outside the tight box 2 and the other end 5b is connected to the upstream of the mechanical booster pump 33 via a valve 51 and a trap 52 to provide an external exhaust system 5. I have. In addition, what is shown by the code | symbol 20 in a figure is a strong cooling fan. Next, a method of using this embodiment will be described. First, the lids 11a, 12a, and 22 are opened, and the processing object W is set in the tight box 2. Next, the lid 11
a, 12a, and 22 are closed to operate the outer exhaust system 5 and the inner exhaust system 3 to evacuate the furnace space S2 and the processing space S1 to a predetermined degree of vacuum, and then close the valve 51 to exhaust the inner exhaust system 3; Gas from the gas introduction system 4 and the heater 14
To start the degreasing treatment on the processing object W. At this time, the furnace pressure becomes at least a pressure exceeding 5 × 10 ⁻⁴ Torr, and paraffin and the like among the components of the binder evaporate from the processed material W first. When degreasing progresses to some extent and the shape retaining force of the processed material increases, the valve 51 of the outer exhaust system 5 is opened together with the inner exhaust system 3 to increase the amount of gas in the gas introduction system 4. This gas passes through the passage 21 of the tight box body 21.
After flowing in the intermediate chamber 21b and being introduced into the intermediate chamber 21b, a part flows into the processing space S1 through the contact gap between the tight box main body 21 and the lid 22, as indicated by an arrow in the figure, and the other part flows into the tie box. It flows out into the heating space 13 through the contact gap between the main body 21 and the lid 22. The gas flowing into the processing space S1 is discharged out of the furnace 1 via the internal exhaust system 3 together with the remaining binder components, for example, resin, which evaporate from the processing object W. The gas flowing into the heating space 13 is ventilated. After passing through the heat insulating material 12 having a property and exiting into the furnace interior space S2, it is discharged out of the furnace 1 through the external exhaust system 5. At this time, if any of the paraffin or the like that has evaporated previously leaks to the furnace space S2 through the gap between the main body 21 and the lid 22 of the tight box 2 due to diffusion and adheres to the periphery, it is re-used. Evaporates and is discharged together. In this case, the intermediate chamber 2 into which gas is introduced
Since the pressure of 1b is the highest, paraffin or the like is prevented from flowing back from the furnace space S2 to the processing space S1 through the gap between the main body 21 and the lid 22 of the tight box 2, and the resin and the like are transferred to the furnace space. Leakage is also prevented. The resin and the like sucked out of the internal exhaust system 3 are trapped by the trap 3
The carrier gas is captured at 2, 52 and pump 3
It is released to the atmosphere through 3,34. The furnace pressure during the degreasing step is kept below the atmospheric pressure.

When the above degreasing step is completed, the temperature in the furnace 1 is further raised, and the process proceeds to the next sintering step. In the degreasing step, the gas is used to prevent the processed material W from evaporating. Also in this case, the gas reaches the intermediate chamber 21b via the gas introduction system 4, flows through the processing space S1 and the furnace space S2, and is discharged from the inner exhaust system 3 and the outer exhaust system 5.
The gas flowing into the furnace space S2 discharges the residue outside the furnace,
The gas flowing into the processing space S1 prevents the processed material from evaporating.

With the above configuration, the paraffin and the like once evaporated leaks into the furnace space S2 through the gap between the main body 21 and the lid 22 of the tight box 2 and temporarily leaks to the furnace wall and the like. Is effectively removed by increasing the amount of gas introduced into the furnace 1 via the gas introduction system 4 when the processing object W is subsequently heated. That is, by such parallel exhaust, a part of the gas introduced into the intermediate chamber 21b enters the processing space S1 through the gap between the lid 22 and the main body 21, and is exhausted by the internal exhaust system 3, and Enters the furnace space S2 and is exhausted by the external exhaust system 5, so that even if paraffin or the like adhering to the furnace wall or the like re-evaporates in the furnace space S2, the external exhaust system 5 It is surely discharged out of the furnace 1 and the inside of the processing space S1 is kept clean even during sintering. Therefore, in the present embodiment, the processed material W is not re-contaminated, and the quality of the injection-molded product can be effectively improved as compared with the related art.

The specific configuration of each section is not limited to the above-described embodiment. For example, in the above-described embodiment, the lid of the tight box is made openable and closable by the cylinder. However, this lid may be left in the tight box main body, screwed, and configured independently of the furnace door and the like. Also, the entire tight box can be made removable from the furnace. In this case, the relation between the tight box main body and the lid is not necessarily limited to the structure that is detachable in the core direction, and may be detached in any positional relation as long as the processing object can be taken in and out of the tight box. Good. Further, if necessary, a gas introduction system 6 in the box and an auxiliary gas introduction system 7 shown in the figure can be used. In addition, specific embodiments of each part can be variously modified without departing from the spirit of the present invention, such as connecting an exhaust passage to the intermediate chamber and providing an intermediate chamber on the lid side.

[0016]

The present invention is embodied in the form described above and has the following effects. That is, the heat treatment furnace of the present invention is provided with an intermediate chamber which is closed at the time of mounting and is opened at the time of detachment, on the one contact surface of the lid or the body of the removable tight box, and the intermediate chamber is provided with a gas through a gas introduction system. , And the gas can be exhausted by the internal exhaust system and an external exhaust system provided at a position for exhausting the furnace space outside the tight box.

For this reason, during degreasing, paraffin and the like once diffused and leaked from the processing space to the furnace space side through the gap between the lid of the tight box and the main body are exhausted from the external exhaust system without returning to the processing space again. The furnace space and the processing space can be cleaned. Then, recontamination of the processed material in the next sintering step can be prevented, and the quality of the final product can be reliably improved.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Furnace 2 ... Tight box 3 ... Internal exhaust system 4 ... Gas introduction system 5 ... External exhaust system 21 ... Main body 21b ... Intermediate room 22 ... Lid S1 ... Processing space S2 ... Furnace space W ... Processing object

Claims (1)

[Claims] 1. A tight box capable of closing a processing space inside by a main body having an opening disposed in a furnace and a lid removably abutting on the opening, and a tight box which is directly connected to the processing space. An inner exhaust system capable of exhausting outside the furnace, and a gas introducing system for introducing gas into the furnace, comprising: An intermediate chamber which is closed and opened at the time of separation is provided, a gas is guided to the intermediate chamber via a gas introduction system, and the gas is provided at a position for exhausting the furnace internal space outside the inner exhaust system and the tight box. A heat treatment furnace characterized by being configured to be evacuated by an external exhaust system.