JP3196305B2 - 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 vacuum furnace for performing heat treatment such as heat treatment and sintering of an object to be processed.

[0002]

2. Description of the Related Art Conventionally, heat treatment of easily oxidizable materials such as stainless steel and aluminum is performed in a vacuum using a vacuum furnace. Also, when the degree of vacuum is high, some components of the material are likely to evaporate.
Heat treatment is also performed in an atmosphere gas at rr or atmospheric pressure.

[0003]

However, since the heating of the object to be processed in the vacuum furnace is performed by radiant heat transfer from a heater such as an electric heater, an assembly of many objects to be processed is processed at a time. In some cases, there has been a problem that the temperature inside the assembly is delayed, a long processing time is required, and productivity is poor.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a vacuum furnace capable of raising the temperature of an object to be processed in a short time with less uneven temperature.

[0005]

According to the vacuum furnace of the present invention, a heat insulating chamber surrounded by a heat insulating wall is provided in a furnace shell connected to a vacuum pump and an atmosphere gas supply source, and one side wall is constituted by a perforated plate. A chamber having an air inlet on the other side wall facing the air chamber is disposed in the heat-insulating chamber, and an atmosphere gas circulating path extends from the air inlet to the outside of the one side wall through the outside of the chamber. A fan for heating the atmosphere gas and a tray for holding the objects to be processed in a stacked manner and loaded into the chamber.

[0006]

In the vacuum furnace according to the present invention, the tray is charged into the chamber and the atmosphere gas is charged into the furnace shell.
When the fan is operated, the atmospheric gas sucked from the intake port is heated by the heater, is blown into the chamber from the perforated plate portion through the circulation path, and after heating the workpiece, a circulating flow reaching the intake port is formed. You. The high-temperature atmosphere gas flowing into the chamber is rectified by the ventilation holes of the perforated plate, and flows laterally between the stacked objects to obtain a desired gas flow distribution by the arrangement of the ventilation holes. Therefore, a large number of workpieces on the tray can be heated in a short time with a substantially uniform temperature distribution.

In the present invention, if the circulation path is formed between the wall surface of the insulated room and the outer wall surface of the chamber, the atmosphere gas heated by the heater flows through the insulated room, so that the heat loss is small and the structure is simple. preferable.

In the present invention, the vacuum furnace is a continuous furnace having a hearth roller for tray transfer, and the chamber is a tunnel-shaped chamber having a tray loading inlet at one end and a tray outlet at the other end. This is preferable because the loading and extraction of the tray with respect to the chamber can be performed quickly and easily.

Further, in the present invention, the other side wall of the chamber is also constituted by a perforated plate, and if the holes of the perforated plate are used as intake ports, the gas flow distribution in the chamber is controlled by the rectifying action of the plurality of intake ports. It is preferable because it is further uniformized.

In the present invention, when the chamber is configured such that the other side wall is cut off, and the opening formed by this cut is used as an air inlet, the suction resistance is small and the structure of the chamber is simple and preferable.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a continuous vacuum sintering furnace will be described below with reference to FIGS. In the figure, reference numeral 1 denotes a continuous vacuum sintering furnace, which comprises a dewaxing chamber 2, a sintering chamber 3, and a cooling chamber 4 arranged in series. Reference numeral 5 denotes an inlet for charging the object to be treated, 6 denotes an outlet for extraction, and an inlet door 7 and an outlet door 8 are air cylinder type opening / closing devices 9 and 1.
0 is driven to open and close. Reference numeral 11 denotes a charging table, reference numeral 12 denotes an extraction table, and reference numeral 13 denotes a hearth roll provided in the furnace for the entire length of the furnace for transporting in the furnace.

On the other hand, as shown in detail in FIG. 2, the sintering chamber 3 has a substantially cylindrical heat insulating wall 2 made of graphite in a cylindrical furnace shell 21.
2 is provided, and a chamber 24 through which the tray 40 passes is provided in the heat insulating chamber 23. The chamber 24 has a tray-shaped inlet 25 at one end and a tray outlet 26 at the other end, and has a tunnel shape extending in the furnace length direction and having a rectangular cross section. One side wall 27 of the chamber 24 has a large number of passages. It is made of a perforated plate having pores 28, and an intake port 30 is provided in the other side wall 29. 3
Reference numerals 1a and 31b denote circulation paths extending from the intake port 30 to the outside of the side wall 27, and are formed between the inner surface of the heat insulating wall 22 and the outer wall surface of the chamber 24. Reference numeral 32 denotes a fan for circulating atmospheric gas, which is provided to face the intake port 30 and is driven by an electric motor 33. Reference numeral 34 denotes an electric heater provided in the circulation path 31 (a generic name of the upper circulation path 31a and the lower circulation path 31b). An exhaust port 35 provided in the furnace shell 21 is connected to a vacuum pump (not shown), and an atmospheric gas supply port 36 also provided in the furnace shell 21 is connected to an atmospheric gas supply source (not shown).

The tray 40 is a tray for holding a large number of workpieces 41, which are aluminum sintered parts, in a stacked manner, and the workpieces 41 are placed on a plurality of shelves 42. The front wall 43 and the rear wall 44 of the tray 40 are fitted to the inner peripheral surface of the chamber 24 with a small amount of clearance, and the atmospheric gas flowing in the circulation path 31 flows from the tray inlet 25 and the tray outlet 26 to the outside. It is configured to prevent the fluid from flowing directly into the chamber 24.

The dewaxing chamber 2 on the pre-process side of the sintering chamber 3
The sintering chamber 3 has the same configuration as that of the sintering chamber 3 except that the above-described chamber 24 and the fan 32 are not provided. A heat insulating chamber 52 is provided in a furnace shell 51 and a heater 53 is provided. The cooling chamber 4 on the post-process side of the sintering chamber 3 has a fan 55 for circulating the atmosphere and a cooler 56 for cooling the atmosphere inside the furnace shell 54. Door 57 between dewaxing chamber 2, sintering chamber 3, and cooling chamber 4
And 58 are opening and closing devices 59 and 60 of the air cylinder type.
It can be opened and closed by.

Next, the object 4 to be processed in the vacuum furnace having the above-described configuration is described.
The first processing method will be described with reference to FIG. First, when the trays 40 on which the workpieces 41 are stacked are loaded into the dewaxing chamber 2, the doors 7 and 57 are closed to evacuate the interior of the dewaxing chamber 2, and the heater 53 makes the workpieces 4.
1 is heated to about 450 ° C. to perform dewaxing. At this time, after once evacuating to a high degree of vacuum of about 10 ⁻³ Torr, a small amount of nitrogen gas is supplied into the chamber to discharge wax as carrier gas to the outside of the furnace.

At the end of the dewaxing operation, the interior of the dewaxing chamber 2 and the sintering chamber 3 are evacuated, the door 57 is opened, and the tray 40 is transferred into the chamber 24 of the sintering chamber 3.
After evacuation of the residual wax adhering to the object 41 while the temperature is raised by the step 4, the nitrogen gas is introduced into the sintering chamber 3 from the atmosphere gas supply port 36 to make the inside of the sintering chamber 3 a nitrogen gas atmosphere at substantially atmospheric pressure. Drive 32. As a result, the insulation room 23
The nitrogen gas inside flows through the circulation path 31 and is heated by the heater 34, passes through the ventilation holes 28 in the side wall 27 made of a perforated plate, flows laterally through the chamber 24 in a rectified state, and After substantially uniformly heating the object 41 to be treated,
And is circulated to the circulation path 31.

The object 41 is heated to about 600 by the above-mentioned heating.
After sintering at a predetermined temperature for a predetermined time, the inside of the sintering chamber 3 is evacuated again, the door 58 is opened, and the tray 40 is transferred into the cooling chamber 4.
The high-temperature gas is prevented from flowing into the cooling chamber 4, and the temperature of the nitrogen gas in the cooling chamber 4 is reduced.
1 can be quenched. And a plurality of trays 40
Are sequentially and intermittently charged into the furnace, and the above-described steps are repeated, whereby a large number of articles can be continuously processed. The tray 40 may not have the front wall 43 and the rear wall 44 (see FIG. 1).

Next, a second embodiment in which the present invention is applied to a continuous vacuum sintering furnace will be described with reference to FIGS.
These figures show only the part of the sintering chamber 3 in FIG.
1 and 2 are denoted by the same reference numerals, and detailed description is omitted.

In this embodiment, the heat insulating wall 22 has a substantially rectangular cylindrical shape, and the chamber 61 has a U-shaped tunnel shape extending in the furnace length direction. That is, the chamber 6
1 comprises side walls 27, 62 and a top wall 63, and has no bottom wall. The other side wall 62 opposite to the one side wall 27 made of a perforated plate is also made of a perforated plate.

The side wall 62 and the top wall 6 of the chamber 61
3 and the circulation path 6 outside the side wall 27.
5b is partitioned by a partition plate 66, and a fan 68 housed in a casing 67 for the blower is arranged at the top of the heat insulating chamber 23, and a discharge port 69 of the casing 67 is opened to the partition plate 66. is there. Reference numeral 70 denotes a suction port of the casing 67. Reference numeral 71 denotes a bottom wall of the circulation path 65a, reference numeral 72 denotes a bottom wall of the circulation path 65b, and reference numerals 73 and 74 denote side walls for closing the sintering chamber entrance side and exit side of both the circulation paths 65a and 65b. The arrangement of the heater 34 is also different from that of the first embodiment.

In this embodiment, the same operation as in the first embodiment is performed, but the sintering chamber 3 is heated when the object 41 is heated.
When the fan 68 is operated with a nitrogen gas atmosphere of approximately atmospheric pressure inside, the nitrogen gas flowing into the chamber 61 in a rectified state through the ventilation holes 28 of the side wall 27 made of a perforated plate is
The flow is rectified by the large number of intake ports 64 on the other side wall 62 made of a perforated plate, and flows out from the intake ports 64 into the circulation path 65a as a substantially uniform flow, so that the nitrogen gas flow in the chamber 61 is further uniformed. Has advantages.

FIGS. 6 and 7 show a third embodiment in which the present invention is applied to a continuous vacuum sintering furnace. In the second embodiment, the side wall 62 is removed, and one side is removed by this removal. A large opening formed on the side of the passage of the tray 40 facing the side wall 27 is used as the intake port 75. Further, in this embodiment, a guide plate 76 for smoothly changing the gas flow direction is provided at the intake port 75. Other configurations are the same as those of the second embodiment.

That is, the intake port 75 in this embodiment
Is an enlarged view of the intake port 30 in the first embodiment,
Is equivalent to the one that is opened over the entire surface of. The chamber 77 has a tunnel shape having an L-shaped cross section composed of only the side wall 27 and the top wall 63. Since the side walls 29 and 62 in other embodiments are omitted, the intake resistance of the fan 68 can be small. The structure of 77 is also simplified. The guide plate 76 may be omitted.

The present invention is not limited to the above embodiments. For example, in the second and third embodiments, the bottom walls may be provided in the chambers 61 and 77. In the above, the example of the continuous vacuum sintering furnace has been described. However, the present invention is also applicable to a batch type vacuum furnace and a vacuum furnace for heat treatment. Further, in the above embodiment, the circulation paths 31, 65 are formed in the heat insulating chamber 23, and thus have an advantage that the heat loss is small.
It may be constituted by a pipeline extending from 4,75 parts through the outside of the furnace shell 21 to the side wall 27 part.

[0025]

As explained above, according to the present invention,
Atmospheric gas heated by a heater is flowed into the chamber containing the tray in a rectified state, and is circulated laterally in the chamber. The temperature can be raised.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a continuous vacuum sintering furnace showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a diagram showing a method of operating the furnace of FIG. 1;

FIG. 4 is a vertical sectional view of a sintering chamber of a continuous vacuum sintering furnace showing a second embodiment of the present invention.

FIG. 5 is a sectional view taken along line BB in FIG. 4;

FIG. 6 is a longitudinal sectional view of a sintering chamber of a continuous vacuum sintering furnace showing a third embodiment of the present invention.

FIG. 7 is a sectional view taken along line CC in FIG. 6;

[Description of References] 1 ... continuous vacuum sintering furnace, 3 ... sintering chamber, 21 ... furnace shell, 22
... heat insulation wall, 23 ... heat insulation chamber, 24 ... chamber, 25 ... tray loading inlet, 26 ... tray outlet, 27 ... side wall, 28 ... vent hole, 29 ... side wall, 30 ... intake port, 31a ... circulation path, 3
1b: circulation path, 32: fan, 34: heater, 35: exhaust port, 36: atmosphere gas supply port, 40: tray, 41 ...
Object to be processed, 42: shelf board, 61: chamber, 62: side wall,
63 ... top wall, 64 ... intake port, 65a ... circulation path, 65b ...
Circulation path, 66: partition plate, 67: casing, 68: fan, 75: intake port, 77: chamber.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI F27D 7/06 F27D 7/06 A (56) References JP-A-60-262914 (JP, A) JP-A-62-93310 ( JP, A) JP-A-4-39593 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F27D 7/04 C21D 1/767 C21D 1/773 F27B 9/04 F27B 9 / 10 F27D 7/06

Claims (5)

(57) [Claims] 1. A heat insulating chamber surrounded by a heat insulating wall is provided in a furnace shell connected to a vacuum pump and an atmosphere gas supply source, and one side wall is constituted by a perforated plate, and the other side wall opposed thereto is provided with an air inlet. Is provided in the insulated room,
In a circulation path extending from the intake port to the outside of the one side wall via the outside of the chamber, a fan for ambient gas circulation and a heater for ambient gas heating are provided, and the processing object is held in a stacked state. A vacuum furnace comprising a tray to be inserted into a chamber. 2. The vacuum furnace according to claim 1, wherein the circulation path is formed between a wall surface of the heat insulating chamber and an outer wall surface of the chamber. 3. A hearth roller for conveying a tray is provided.
2. The chamber of claim 1, wherein the chamber comprises a tunnel-shaped chamber having a tray loading inlet at one end and a tray outlet at the other end.
Or the vacuum furnace according to 2. 4. The vacuum furnace according to claim 1, wherein the other side wall of the chamber is also formed of a perforated plate, and a hole of the perforated plate is used as an intake port. 5. The vacuum furnace according to claim 1, wherein the chamber has a configuration in which the other side wall is cut off, and an opening formed by the cut off of the side wall is used as an intake port.