JPH05106973A - Vacuum furnace - Google Patents

Abstract

PURPOSE:To obtain a vacuum furnace which is capable of heating a large number of work pieces in a short time without temperature variability. CONSTITUTION:There is provided a chamber 24 which houses a tray 40 in an insulation chamber 23 enveloped with an insulation wall 22 in a furnace shell 21. A large number of ventilation holes 28 are bored on a side wall of this chamber 24 on one side while a suction air port 30 is installed to a side wall 29 on the other side. The ambient gas in the furnace is arranged to flow from the ventilation ports 28 into the chamber 24 by way of circulation passages 31a and 31b by driving a fan 35. The ambient gas heated with a heater 34 flows laterally under a flow straightened state in the chamber 24 and circulates to the suction air port 30 and heats work pieces 41 stacked on many stages on the tray 40.

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 or sintering of an object to be treated.

[0002]

2. Description of the Related Art Conventionally, a heat treatment of a material which is easily oxidized, such as a stainless steel or an aluminum material, is carried out in a vacuum using a vacuum furnace. Also, as the degree of vacuum increases, some components of the material are likely to evaporate, so several atmospheres can be obtained by introducing atmospheric gas into the once evacuated furnace shell.
A heat treatment is also performed in an atmosphere gas of rr or atmospheric pressure.

[0003]

However, since the heating of the object to be processed in the vacuum furnace depends on the radiant heat transfer from a heater such as an electric heater, a large number of objects to be processed are processed at one time. In some cases, the temperature rise inside the assembly is delayed, which requires a long processing time, resulting in poor productivity.

The present invention solves 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 temperature unevenness.

[0005]

In 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 atmospheric gas supply source, and one side wall is formed of a perforated plate. A chamber having an intake port on the other side wall opposite to this is provided in the heat insulating chamber, and the atmosphere gas is circulated in the circulation path from the intake port to the outside of the one side wall through the outside of the chamber. And a heater for heating the atmospheric gas, and a tray for holding the objects to be processed in a stacked state and loading them in the chamber.

[0006]

In the vacuum furnace of the present invention, the tray is loaded into the chamber and the atmosphere gas is introduced into the furnace shell,
When the fan is operated, the atmospheric gas sucked from the intake port is heated by the heater, passes through the circulation path, and is blown into the chamber from the perforated plate portion, and after heating the object to be processed, a circulation flow reaching the intake port is formed. It The high-temperature atmospheric 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, it is possible to raise the temperature of many objects to be processed on the tray in a short time with a substantially uniform temperature distribution.

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

Further, in the present invention, the vacuum furnace is a continuous furnace having a hearth roller for transporting trays, and the chamber is a tunnel-shaped chamber having a tray loading port at one end and a tray delivery port at the other end. This is preferable because the loading and extraction of the tray for the chamber can be performed quickly and easily.

Further, in the present invention, the other side wall of the chamber is also made of a perforated plate, and if the holes of this perforated plate are used as the intake ports, the gas flow distribution in the chamber will be improved by the rectifying action of the multiple intake ports. It is preferable because it is further homogenized.

Further, in the present invention, if the chamber is constructed such that the other side wall is cut off and the opening formed by this cut-off is used as an intake port, the intake 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 is 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 is an inlet for charging the object to be treated, 6 is an outlet for the same extraction, and an inlet door 7 and an outlet door 8 are air cylinder type opening / closing devices 9 and 1.
It is designed to be opened and closed by 0. Reference numeral 11 is a charging table, 12 is an extraction table, and 13 is a hearth roll for transporting in the furnace, which is provided over the entire length of 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.
A heat insulating chamber 23 surrounded by 2 is provided, and a chamber 24 through which the tray 40 passes is provided in the heat insulating chamber 23. The chamber 24 is in the form of a tunnel with a square cross section extending in the furnace length direction, with a tray loading port 25 at one end and a tray outlet 26 at the other end. One side wall 27 of the chamber 24 has a large number of passages. It is composed of a perforated plate having pores 28 formed therein, and an intake port 30 is provided on the other side wall 29. Three
Circulation paths 1a and 31b extend 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. A fan 32 for circulating the atmospheric gas is provided so as to face the intake port 30 and is driven by the electric motor 33. Reference numeral 34 is an electrothermal heater provided in the circulation path 31 (generically referring to the upper circulation path 31a and the lower circulation path 31b). Reference numeral 35 is an exhaust port provided in the furnace shell 21, which is connected to a vacuum pump (not shown), and 36 is an atmospheric gas supply port which is also provided in the furnace shell 21, and is connected to an atmospheric gas supply source (not shown).

The tray 40 is a tray for holding a large number of processed objects 41, which are aluminum sintered parts, in a stacked state, and the processed objects 41 are placed on a plurality of shelf plates 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 clearance, and the atmospheric gas flowing in the circulation path 31 is discharged from the tray loading port 25 and the tray delivery port 26. The flow is prevented from directly flowing into the chamber 24.

The dewax chamber 2 on the front side of the sintering chamber 3 is
Except that the chamber 24 and the fan 32 are not provided, the sintering chamber 3 has the same configuration, the heat insulation chamber 52 is provided in the furnace shell 51, and the heater 53 is provided. Further, the cooling chamber 4 on the post-process side of the sintering chamber 3 is provided with a fan 55 for atmosphere circulation and a cooler 56 for atmosphere cooling in the furnace shell 54. Door 57 between dewaxing chamber 2, sintering chamber 3 and cooling chamber 4
And 58 are air cylinder type opening / closing devices 59 and 60.
It is designed to be opened and closed by.

Next, the object 4 to be processed in the vacuum furnace having the above-mentioned structure
The processing method 1 will be described with reference to FIG. First, the trays 40 on which the objects to be processed 41 are stacked are loaded into the dewaxing chamber 2, and then the doors 7 and 57 are closed to make the inside of the dewaxing chamber 2 a vacuum and the object 53 to be processed by the heater 53.
1 is heated to about 450 ° C. for dewaxing. At this time, the gas is once evacuated to a high vacuum degree of about 10 ⁻³ Torr, and then a small amount of nitrogen gas is supplied into the chamber to discharge the wax as a carrier gas to the outside of the furnace.

At the end of the dewaxing, the dewaxing chamber 2 and the sintering chamber 3 are evacuated, the door 57 is opened to transfer the tray 40 into the chamber 24 of the sintering chamber 3, and the heater 3 is placed in vacuum.
After evacuation of the residual wax adhered to 41 parts of the object to be processed while raising the temperature by 4, the nitrogen gas was introduced from the atmosphere gas supply port 36 to make the inside of the sintering chamber 3 a nitrogen gas atmosphere of substantially atmospheric pressure. Drive 32. As a result, the heat insulation chamber 23
The nitrogen gas inside flows through the circulation path 31 and is heated by the heater 34, passes through the vent holes 28 of the side wall 27 made of a perforated plate, flows laterally inside the chamber 24 in a rectified state, and on each shelf plate 42. After the object 41 to be treated is heated almost evenly, the intake port 30
Is sucked from and circulates to the circulation path 31.

The object 41 to be treated is heated to about 600 by the above heating.
After sintering for a predetermined time at 0 ° C., 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 object to be treated 4 is cooled by the nitrogen gas atmosphere whose temperature is lowered in the cooling chamber 4.
1 can be rapidly cooled. And a plurality of trays 40
It is possible to continuously process a large number of products to be processed by sequentially and intermittently charging the same into the furnace and repeating the above steps. 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. 4 and 5.
These figures show only the part of the sintering chamber 3 in FIG.
The same or corresponding parts as those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the heat insulating wall 22 has a substantially rectangular tube shape, and the chamber 61 has a tunnel shape with a U-shaped cross section extending in the furnace length direction. That is, Chillamba 6
1 is composed of side walls 27 and 62 and a top wall 63 and has no bottom wall. The other side wall 62 facing the one side wall 27 made of a perforated plate is also made of a perforated plate, and a large number of the holes form an intake port 64.

The side wall 62 and the top wall 6 of the chamber 61
Circulation path 65a on the outside of 3 and circulation path 6 on the outside of the side wall 27
The space 5b is partitioned by a partition plate 66, and a fan 68 housed in a casing 67 for a blower is arranged at the top of the heat insulating chamber 23, and a discharge port 69 of the casing 67 is opened in the partition plate 66. is there. Reference numeral 70 is a suction port of the casing 67. Further, 71 is a bottom wall of the circulation passage 65a, 72 is a bottom wall of the circulation passage 65b, and 73 and 74 are side walls which close the inlet side and the outlet side of the sintering chamber of both the circulation passages 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 to be processed is heated.
When the fan 68 is operated under a nitrogen gas atmosphere of approximately atmospheric pressure, the nitrogen gas that has passed through the ventilation holes 28 of the side wall 27 made of a perforated plate and has flowed into the chamber 61 in a rectified state is
The nitrogen gas flow in the chamber 61 is further homogenized because it is rectified by the multiple intake ports 64 of 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. It has advantages.

Next, 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 this removal results in one of 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. The other structure is the same as that of the second embodiment.

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

The present invention is not limited to the above-mentioned embodiments. For example, in the second and third embodiments, the chambers 61 and 77 may be provided with bottom walls. Although the example of the continuous vacuum sintering furnace has been described above, the present invention can also be applied to batch type vacuum furnaces and vacuum furnaces for heat treatment. Further, in the above-described embodiment, since the circulation passages 31 and 65 are formed in the heat insulating chamber 23, there is an advantage that heat loss is small.
It may be configured by a pipe line from 4,75 parts to the side wall 27 part through the outside of the furnace shell 21.

[0025]

As described above, according to the present invention,
Atmosphere gas heated by a heater is flowed in a straightened state into the chamber containing the tray, and is circulated horizontally in the chamber, so the temperature unevenness of many objects on the tray can be reduced in a short time. The temperature can be raised.

[Brief description of drawings]

FIG. 1 is a vertical 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.

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

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

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

7 is a cross-sectional view taken along the line CC in FIG.

[Explanation of symbols]

1 ... Continuous vacuum sintering furnace, 3 ... Sintering chamber, 21 ... Furnace shell, 22
... Insulation wall, 23 ... Insulation chamber, 24 ... Chamber, 25 ... Tray loading port, 26 ... Tray delivery port, 27 ... Side wall, 28 ... Vent hole, 29 ... Side wall, 30 ... Intake port, 31a ... Circulation path, 3
1b ... Circulation path, 32 ... Juan, 34 ... Heater, 35 ... Exhaust port, 36 ... Atmosphere gas supply port, 40 ... Tray, 41 ...
Processing object, 42 ... Shelf plate, 61 ... Chamber, 62 ... Side wall,
63 ... Top wall, 64 ... Intake port, 65a ... Circulation path, 65b ...
Circulation path, 66 ... Partition plate, 67 ... Casing, 68 ... Juan, 75 ... Intake port, 77 ... Chamber.

Claims (5)

[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, one side wall is made of a perforated plate, and an intake port is provided on the other side wall opposite to the side wall. A chamber with the above is placed in the heat insulation chamber,
A fan for circulating the atmospheric gas and a heater for heating the atmospheric gas are provided in the circulation path extending from the intake port to the outside of the one side wall through the outside of the chamber, and the objects to be processed are held in a stacked state. A vacuum furnace comprising a tray to be loaded into a chamber. 2. The vacuum furnace according to claim 1, wherein the circulation path is formed between the heat insulating chamber inner wall surface and the chamber outer wall surface. 3. A hearth roller for transporting the tray,
The chamber comprises a tunnel-shaped chamber having a tray loading port at one end and a tray loading port at the other end.
Or the vacuum furnace according to 2. 4. The vacuum furnace according to claim 1, 2 or 3, wherein the other side wall of the chamber is also made of a perforated plate, and the holes of the perforated plate serve as intake ports. 5. The vacuum furnace according to claim 1, 2 or 3, wherein the chamber has a configuration in which the other side wall is cut off, and the opening formed by the cutout of the side wall is an intake port.