JP2723132B2 - Heat treatment furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat treatment furnace for performing sintering, quenching, brazing, and other heat treatments.

Conventional technology Among various heat treatment furnaces, vacuum sintering furnaces, which are indispensable for manufacturing and developing high value-added new materials and new ceramics, are used in all industries including advanced industries. It has been highly evaluated for its ability to produce sintered bodies. However, on the other hand, in the dewaxing process, vapor gas generated from a material to be processed (powder material molded with wax or the like) adheres to a heater or the like, causing furnace contamination, which has been pointed out as a maintenance problem. As a vacuum sintering furnace which has solved this problem, there is a furnace provided with a tight box which is a storage container for an object to be processed inside a furnace shell.

FIG. 3 is a simplified sectional view showing the internal configuration of a conventional vacuum sintering furnace having a tight box.

There, a tubular insulating wall 12 made of graphite is provided inside a furnace shell 10 to which a vacuum exhaust device and a gas supply device (not shown) are connected, and inside the tubular insulating wall 12. Is provided with a tight box 20 made of graphite for accommodating the processing object 60 inserted through the pressure switch 11A, 11B of the furnace shell 10. On the other hand, tight box 20 and cylindrical insulating wall
In a gap between the rod and the rod 12, a graphite rod heater 70 for heating the tight box 20 is provided in the form of a hollow support of a total of eight rod heaters in the insertion direction of the workpiece 60 (not shown in the drawing, Each of the rod heaters 70 is a tight box 20
Are symmetrically arranged at a pitch of 45 ° with respect to each other). In other words, the workpiece 60 placed under a vacuum atmosphere by the vacuum exhaust device is uniformly heated by radiating heat from the tight box 20, and at the same time, the paper gas generated at the time of dewaxing is heated together with the nitrogen gas sent through the gas supply device. The structure is such that forced exhaust is performed from the box 20. However, none of the components necessary for hollow support of the tubular heat-insulating wall 12, the rod heater 70, and the tight box 20 are shown.

However, in the case of the above-described conventional example, since the rod heater 70 is hollowly supported in the gap between the tight box 20 and the cylindrical heat insulating wall 12, the furnace shell 10 itself is not provided. There is a limit to adopting a larger capacity of the tight box 20 than before without changing the capacity, and while the cost competition is extremely severe, the increase in the processing capacity, which is one of the factors for judging the inferiority of the furnace, This is a major obstacle in achieving both the size increase and the size of the object 60, which is predicted in the future. In addition, even if it is not necessary to provide a component for hollowly supporting the rod heater 70, all the mounting work of the rod heater 70 must be performed inside the furnace shell, thereby improving the assembling efficiency of the apparatus. It is also a problem above.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heat treatment furnace capable of increasing the capacity of a tight box by making a slight design change.

Means for Solving the Problems In the present invention, a tight box which is a storage container for an object to be treated is provided inside the furnace shell, and a gas is supplied to the outer peripheral space between the furnace shell and the tight box to reduce a pressure difference between the inside and outside of the tight box. In a heat treatment furnace provided with a gas supply means for producing, a heater for heating the object to be processed is embedded in the tight box.

Action The tight box is heated by the embedded heater,
The object to be processed is heated by the radiant heat from the tight box.

Example Hereinafter, an example of a heat treatment furnace according to the present invention will be described with reference to the drawings. FIG. 1 is a simplified configuration diagram of a gas pressurized cooling type vacuum sintering furnace, and FIG. 2 is a view taken along line AA of FIG.

At both open ends of the cylindrical furnace shell 10, pressure opening / closing doors
11A and 11B are provided, respectively.
On the back of 1B, a plate-shaped heat insulating wall made of ceramic material
121A and 121B are respectively provided movably in the direction a in the figure. Moreover, in addition to the cylinder / rod mechanism (not shown) for moving the plate-shaped heat insulating walls 121A and 121B, the cooling gas circulation fan 41 and the casing are provided on the pressure opening / closing doors 11A and 11B on the back side of the plate-shaped heat insulating walls 121A and 121B. 42, a forced cooling device 40 (only the pressure opening / closing door 11A) including a water exchange pipe 43 for heat exchange and the like is provided. In addition, on the surface of the plate-shaped heat insulating walls 121A and 121B,
Lid members 21A and 21 corresponding to lids of tight box 20 described later
1B is fixed respectively.

On the other hand, inside the furnace shell 10, a tubular heat insulating wall 12 made of the same material as the plate heat insulating walls 121A and 121B is provided in a hollow supported form, and inside the cylindrical heat insulating wall 12, A tight box 20 made of, for example, ceramic and having an outer shape capable of being in close contact with the tight box is provided. However, cylindrical insulation wall 12
Are not shown.

That is, if the pressure opening / closing doors 11A and 11B are closed, the open both end surfaces of the cylindrical heat insulating wall 12 are formed by the plate heat insulating walls 121A and 121B.
At the same time, open both end surfaces of the tight box 20 are covered with lid members 21A and 21B.
, Respectively.

Inside the tight box 20, there is provided a hearth 22 on which the object 60 is placed, and further, at the bottom thereof, a vapor gas exhaust pipe 15 is connected. The vapor gas generated inside is sent to a wax strap 16 arranged outside the furnace shell 10 (details will be described later). On the other hand, in the wall of the tight box 20, a heater 30 for heating the processing object 60 is helically embedded over the entire peripheral surface thereof (see FIGS. 1 and 2).

The heater 30 will be described below in detail. In the present embodiment, a bare nichrome wire is employed in connection with the tight box 20 being an electrical insulator, and the tight box 20 is used.
During the manufacturing process of the heater, leave the power supply lead wire (not shown)
The tight box 20 with the embedded heater 30 and the heater 30 attached thereto is inserted into the inside of the cylindrical heat-insulating wall 12, and the power supply lead wire is connected to a power lead-in electrode ( (Not shown). However, if the tight box 20 is made of graphite, for example, the heater
Some insulation is needed around 30.

Next, a device provided around the furnace shell 10 will be described. On the wall of the furnace shell 10, a suction pipe of the vacuum exhaust device 50 is provided.
14 is connected, and by appropriately switching the rotary pump 52 and the oil diffusion pump 51, air and the like inside the furnace shell 10 are sucked, and a vacuum state necessary for sintering is created. The vapor gas exhaust pipe 15
The other end is connected to a rotary pump 52, and the suction force sucks the paper gas or the like filled in the tight box 20, and the wax component contained in the vapor gas is supplied to the wax trap 16 provided in the middle of the vapor gas exhaust pipe 15.
Is to be collected.

Similarly, a gas supply pipe 13 of a gas supply device (not shown) is connected to the wall surface of the furnace shell 10, and in the case of dewax or the like, a predetermined gas such as nitrogen gas is used as a carrier gas inside the furnace shell 10. The pressure difference is sent between the inside and the outside of the tight box 20 which is sucked through the vapor gas exhaust pipe 15. Therefore, the vapor gas generated from the processing object 60 is surely guided to the wax strap 16 without leaking to the outside of the tight box 20. Further, when removing the workpiece 60 after the main sintering step, for example, nitrogen gas is sent from the gas supply device as a cooling gas into the inside of the furnace shell 10, and this is cooled and forced by the forced cooling device 40.
In this process, the workpiece 60 is cooled to a high temperature in a short time in this process. Reference numeral 16 denotes a water cooling tube for cooling the outside of the furnace shell 10 (see FIG. 2).

Hereinafter, the specific operation of the heat treatment furnace configured as described above will be described in detail.

First, the pressure opening / closing doors 11A and 11B are opened, the workpiece 60 is inserted into the tight box 20, and after placing it on the hearth, the pressure opening / closing doors 11A and 11B are closed, and the evacuation device 50 is operated. . When the inside of the furnace shell 10 reaches a predetermined pressure state, the heater 30 is energized, and then a nitrogen gas is fed into the furnace shell 10 from a gas supply device. Eventually 60
When the temperature is close to the dewaxing temperature, vapor gas will gradually be generated from now on. It is.

Then, when a sufficient time has passed for the wax component to sufficiently escape from the workpiece 60, the dewaxing step is completed, and thereafter, the temperature, pressure, and the like of the workpiece 60 are set according to a predetermined heat treatment pattern. And the main sintering process is sequentially performed.

When the main sintering step is completed, nitrogen gas is sent again from the gas supply device, and the plate-shaped heat insulating walls 121A and 121B are respectively moved in the direction a in the drawing to allow nitrogen gas to flow inside the tight box 20. To At the same time, forced cooling device 40
Is operated to cool the nitrogen gas circulating throughout the inside of the furnace shell 10. Then, the sintering is completed
If the temperature of 60 drops below a predetermined level, the pressure opening / closing door 11A
Or open 11B and take it out. This completes a series of heat treatment steps.

Accordingly, in the case of the present embodiment, since the tight box 20 is inserted and fixed along the inner wall of the cylindrical heat insulating wall 12, the capacity of the tight box 20 is compared with that of the conventional example. Of course, the components required to fix and support the tight box 20 are no longer required, and most of the work of mounting the heater 30 can be performed outside the furnace shell 10. There is a great advantage in reducing costs.

Moreover, since the heaters 30 are arranged uniformly over the entire peripheral surface of the tight box 20, it is effective in uniformly heating the workpiece 60, and the heaters are also provided on the lid members 21A and 21B.
By embedding 30, there is a very great advantage in further promoting good sintering of the object 60.

Furthermore, in the present embodiment, the dewaxing is performed in a nitrogen gas atmosphere, but the heater 30 is
Embeded in a tight box 20 and a tubular insulating wall 12
And the like are ceramic materials, so that dewaxing is possible even in an air atmosphere. This is of great significance in that it can sufficiently cope with recently published research reports that dewaxing efficiency is increased if dewaxing is performed in an air atmosphere.

Incidentally, the heat treatment furnace according to the present invention is, of course, not limited to the application of only the gas pressure cooling type vacuum sintering furnace,
Regarding the method of embedding the heater, a concave portion may be formed on the peripheral surface of the tight box, and this may be attached to the heater. Also, it goes without saying that the method of fixing and supporting the tight box is not limited.

Effects of the Invention As described above, in the case of the heat treatment furnace of the present invention, the capacity of the tight box can be increased as much as the space required for mounting the heater can be omitted, and the furnace can be used without a large design change. Therefore, it is possible to increase the processing capacity, which is one of the factors for determining the priority, and to increase the size of the object to be processed which is predicted in the future. Moreover, since the heater can be embedded in the tight box outside the furnace shell due to its structure, the heater mounting operation can be simplified, and the need for a heater support member is eliminated. There is a great advantage in reducing the cost of the entire apparatus.

Further, since the heater is embedded in the tight box, dewaxing can be performed even in an air atmosphere.

[Brief description of the drawings]

FIGS. 1 and 2 are explanatory views of an embodiment of a heat treatment furnace according to the present invention. FIG. 1 is a simplified configuration diagram of a gas pressurized and cooled vacuum sintering furnace, and FIG. 2 is FIG. FIG. 4 is a view as viewed from the direction of arrows AA. FIG. 3 is a simplified sectional view showing the internal configuration of a conventional vacuum sintering furnace. 10 Furnace shell 20 Tight box 30 Heater 60 Workpiece

Claims (1)

(57) [Claims] A tight box which is a storage container for an object to be treated is provided inside a furnace shell, and gas supply means for supplying a gas to an outer peripheral space between the furnace shell and the tight box to create a pressure difference between the inside and outside of the tight box is provided. Heat treatment furnace,
A heat treatment furnace, wherein a heater for heating the object is embedded in the tight box.