JPH0212668B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum furnace apparatus used, for example, in brazing aluminum products.

In general, vacuum furnace equipment for brazing aluminum products such as heat exchangers requires a high degree of vacuum to prevent oxidation of the metal used for brazing. In addition to evacuating the vacuum using a vacuum pump, oxygen remaining in the vacuum furnace is removed by burning an oxygen-removing substance, such as magnesium. Such residual oxygen removal is performed as follows. In other words, when an aluminum product coated with an aluminum alloy containing magnesium is brought into a vacuum furnace and heated, when the temperature of the magnesium reaches approximately 550°C or higher, the magnesium vaporizes and flies around the vacuum furnace as gas molecules. . When this is combined with residual oxygen, it is converted into magnesium oxide, and the residual oxygen is removed.

By the way, in the method of burning magnesium, a high degree of vacuum can be obtained by removing residual oxygen, but since vaporized magnesium or magnesium oxide begins to solidify at a temperature of about 400°C or below, When it hits an object, it becomes deposited on its surface. For this reason, after the brazing process (the temperature of the brazing process is approximately 580℃) is completed, cooling may be started while maintaining the vacuum state, or inert gas may be introduced into the vacuum furnace using a circulation fan, etc. When forced cooling is started, magnesium or magnesium oxide (hereinafter collectively referred to simply as ``magnesium'')
That's what it means. ) begins to adhere and accumulate in the low-temperature parts of the vacuum furnace (parts with a temperature of about 400°C or less), causing the following problems. In other words, if magnesium adheres to the surface of the electrical insulating material inside the vacuum furnace, it will cause electrical leakage.Also, a heating chamber is formed separately in the vacuum furnace, and the object to be heated is carried into the heating chamber by a trolley. In this case, problems such as magnesium sticking to the gap between the cart and the wall of the heating chamber arise, such as making it difficult to carry the cart out of the heating chamber. Magnesium will also adhere to the inner walls of the vacuum furnace body or heating chamber as they cool down, but if the adhering magnesium is not removed, magnesium will be released into the atmosphere when the door of the vacuum furnace body is opened. It begins to absorb water. For this reason, the next time the door is closed and the vacuum pump is used to evacuate, it takes a long time to reach a high vacuum state, which reduces operability. On the other hand, removing magnesium adhering to the inner wall after each operation is
Particularly when the vacuum furnace body or heating chamber is large, much labor and time are required, resulting in increased running costs and decreased operability. Furthermore, it is dangerous for workers to enter the vacuum furnace to perform cleaning work because magnesium is an ignitable substance, and furthermore, magnesium dust may pose a health hazard.

The present invention was made under these circumstances, and can prevent electrical leakage accidents, etc., and does not require cleaning work to remove oxygen removing substances in the heating chamber, improving operability. It is an object of the present invention to provide a vacuum furnace device that can be improved.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional front view of a vacuum furnace apparatus according to an embodiment, and FIG. 2 is a side view showing a vacuum furnace body and a mechanism for carrying in a material to be heated. Reference numeral 1 denotes a cylindrical vacuum furnace body, and air therein is sucked through an exhaust pipe 11 by a vacuum pump 12.
2 is a door, which is opened and closed by an opening/closing mechanism 21;
3 is a wall with insulation material attached to the frame;
It constitutes an upper wall part and a side wall part of the heating chamber 30.
31 is an electric heater. In this example, a trolley 4 is used to carry the object to be heated into and take it out from the vacuum furnace body 1, and this trolley 4 has rails 41, 4
You will be guided along 2. The bottom plate 43 of the truck 4 is attached to the heating chamber 4 when the truck 4 is housed in the vacuum furnace body 1.
0, and has the role of forming the bottom wall of the wall 3.
Similar to the above, a frame with heat insulating material attached is used. Therefore, the object to be heated M placed on the trolley 4 is heated in the heating chamber 30 surrounded by the wall 3 and the bottom plate 43.

Next, the main parts of this embodiment will be explained. A cooling medium introduction pipe (hereinafter referred to as "introduction pipe") 5A for introducing a cooling medium such as cooling gas (for example, nitrogen gas) or cooling water into the heating chamber 30. A cooling medium discharge pipe (hereinafter referred to as "discharge pipe") 5B for discharging the cooling medium from the heating chamber 30 is provided so as to protrude into the vacuum furnace body 1 from the outside. A flexible introduction hose 51A is connected to one end of the introduction pipe 5A in the vacuum furnace body 1, and a flexible discharge hose 51B is connected to one end of the discharge pipe 5B. On the other hand, the bottom plate 43 of the cart 4 is fixedly provided with an introduction intermediate pipe 52A and a discharge intermediate pipe 52B extending upward from below through the bottom plate 43. When housed inside, the lower ends of the intermediate pipes 52A, 52B are connected to the flexible hoses 51A, 51B via quick joints 53A, 53B, respectively. At the ends of the intermediate pipes 52A and 52B located above the bottom plate 43, as shown in FIG. They are detachably connected via quick joints 61A and 61B. Here, the flow path member 6 is provided with an oxygen removing substance such as magnesium by flowing a cooling medium into the flow path member 6 when the heating chamber 30 is forcedly cooled or left to cool after the heat treatment is completed. It plays the role of adhering to the surface.
A tube, a box, or the like can be used as the flow path member 6, and in this embodiment, a U-shaped tube is used. A flow control valve 7 and a first on-off valve 8A are provided in this order from the upstream side in the middle of the introduction pipe 5A, and a second valve 8A is provided in the middle of the discharge pipe 5B.
An on-off valve 8B is provided. T is heating chamber 30
This is a temperature sensor for detecting the temperature of the cooling medium flowing through the temperature sensor T. When a temperature signal from the temperature sensor T is input to the controller 100, an operation signal corresponding to this input signal is sent from the controller 100 to the flow control valve. 7 will be sent. As a result, the opening degree of the flow control valve 7 is adjusted to control the flow rate of the cooling medium, and the temperature of the cooling medium flowing inside the heating chamber 30 is maintained constant. From the first on-off valve 8A to the second valve via the flow path member 6
A flow path leading to the on-off valve 8B, for example, the introduction pipe 5
Immediately downstream of the first on-off valve 8A at A,
A branch pipe 9 is provided that branches from the introduction pipe 5A and opens into the vacuum furnace body 1 via a third on-off valve 91. This branch pipe 9 is connected from the first on-off valve 8A to the second on-off valve 8B during the heat treatment.
This is to create a vacuum state in the flow path up to the same level as the inside of the vacuum furnace body 1. Incidentally, such a branch pipe may be provided in both the introduction pipe 5A and the discharge pipe 5B.

In an apparatus having such a configuration, for example, the object to be heated M to be brazed is placed on the trolley 4, the trolley 4 is carried into the vacuum furnace body 1, the door 2 is closed, and the vacuum pump 12 is used to generate a vacuum. The air inside the furnace body 1 is exhausted. On the other hand, by previously closing the first on-off valve 8A and the second on-off valve 8B and opening the third on-off valve 91, the second on-off valve is connected from the first on-off valve 8A via the flow path member 6. The air in the flow path up to 8B is exhausted from the exhaust pipe 11 via the branch pipe 9 and the vacuum furnace body 1. After the inside of the vacuum furnace body 1 is sufficiently vacuumed, the object M to be heated is heated by the electric heater 31, and the surface temperature of the object M to be heated is about 500℃.
When the temperature exceeds .degree. C., the adhering magnesium is vaporized and begins to fly around inside the heating chamber 30 while reflecting at a speed of about 1 km per second, and combines with residual oxygen. When the brazing process is completed in the high vacuum atmosphere thus created, the inside of the heating chamber 30 is cooled by, for example, introducing an inert gas. The temperature of the inner walls of the heating chamber 30 is 400℃.
Before the following happens, for example, immediately after the brazing process is finished, close the third on-off valve 91, open the first on-off valve 8A and the second on-off valve 8B, and open the flow path member 6.
The controller 100 adjusts the opening degree of the flow rate control valve 7 to control the flow rate so that the surface temperature of the flow rate control valve 7 is 400° C. or lower. and the inside of the discharge pipe 5B. Therefore, the vaporized magnesium comes to adhere to the surface of the flow path member 6. Thereafter, the cooling medium in the flow path member 6 is expelled by, for example, introducing air from the introduction pipe 8A, and then the quick joints 53A and 53B are removed and the carriage 4 is pulled out of the vacuum furnace body 1. At this time, the intermediate pipes 51A and 51B are pulled out together with the truck 4. Then, by removing the quick joints 61A, 61B, the channel member 6 is removed from the intermediate pipes 51A, 51B, and replaced with a new channel member 6, in preparation for the next brazing operation. Moreover, the removal of magnesium attached to the channel member 6 can be performed by using a mechanical method using a hammer or the like, a method of igniting and burning, a chemical method, etc. 6 can be used again.

According to the embodiment described above, since the surface of the channel member 6 is made into a low-temperature part by flowing the cooling medium through the channel member 6, the magnesium flying around in the heating chamber 30 is concentrated on the surface of the channel member 6. Therefore, there is no risk of magnesium adhering to other parts. Therefore, it is possible to prevent an electric leakage accident caused by magnesium adhering to the surface of the electrical insulating material, and it is also possible to prevent magnesium from sticking to the gap between the cart 4 and the wall 3 of the heating chamber 30, making it difficult to pull out the cart 4. If you do this, you can solve any problems you may have. There is no risk of magnesium adhering to the inner wall of the heating chamber 30, and the channel member 6 with magnesium adhering to its surface is pulled out of the vacuum furnace body 1 together with the trolley 4 and replaced with a new one. Cleaning work inside the room 30 is no longer required,
As a result, it is no longer necessary to carry out cleaning work every time one brazing process is completed, unlike in the conventional case. Therefore, since the next brazing process can be started immediately, operability can be improved. In addition, since the work of removing magnesium from the channel member 6 removed from the trolley 4 can be performed regardless of the operating time,
It does not affect the operating cycle. Furthermore, since the worker does not have to enter the heating chamber 30 to perform cleaning work, accidents caused by magnesium ignition can be avoided, and magnesium dust will not harm health. As in this embodiment, a branch pipe 9 is provided in the flow path from the first on-off valve 8A to the second on-off valve 8B via the flow path member 6, and the branch pipe 9 is provided during the brazing process. By creating a vacuum state in the flow path, the cooling medium flows into the heating chamber 3.
Since there is no leakage within 0, there is no risk of brazing failure. Therefore, the quick joint is not required to have very high airtightness, so a quick joint made of a metal sheet with high heat resistance, for example, can be used. Furthermore, since the brazing process has already been completed when the cooling medium is allowed to flow, even if the cooling medium leaks from the quick joint, the brazing process will not be affected. Also, if flexible hoses 51A, 51B and quick joints 53A, 53B are used, the intermediate pipe 52
A, 52B can be easily connected and separated from the inlet pipe 5A and the discharge pipe 5B.

Here, the present invention may be applied to a vacuum furnace apparatus in which the object to be heated is suspended from the ceiling of a heating chamber without using a trolley, or in which a heating chamber is not separately provided within the vacuum furnace. The present invention may be applied to a vacuum furnace device in which the vacuum furnace body itself constitutes the wall of the heating chamber.

Further, in the present invention, a thermocouple may be provided in the flow path member, and the opening degree of the flow control valve may be adjusted by a controller or manually based on the temperature detected by the thermocouple.

As described above, according to the present invention, by flowing the cooling medium through the channel member, the oxygen removing substance is concentratedly attached to the surface of the channel member, so that the oxygen removing substance is applied to the electrical insulating material. It is possible to prevent electrical leakage accidents caused by adhesion of Moreover, since the channel member is removably installed in the heating chamber, the channel member to which the oxygen removing substance has adhered can be replaced with a new one to prepare for the next heat treatment operation. Cleaning work for removing the oxygen-removing substance is no longer necessary, and operability can be improved, and accidents caused by ignition of the oxygen-removing substance in the heating chamber can be avoided.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view showing a vacuum furnace apparatus according to an embodiment of the present invention, FIG. 2 is a side view showing a vacuum furnace body and a mechanism for carrying in the object to be heated, and FIG. 3 is a flow path member. FIG. 1... Vacuum furnace body, 12... Vacuum pump, 2...
Door, 3... Wall, 30... Heating chamber, 4... Cart,
5A...Cooling medium introduction pipe, 5B...Cooling medium discharge pipe, 51A, 51B...Flexible hose, 6...Cooling medium flow path member, 7...Flow rate control valve, 8A, 8B,
91... Opening/closing valve, 9... Branch pipe, 100... Controller, M... Item to be heated.

Claims (1)

[Claims] 1 In a vacuum furnace device that removes residual oxygen by heating and vaporizing the oxygen removing substance in a heating chamber inside the vacuum furnace and combining it with residual oxygen, cooling is performed to make the vaporized oxygen removing substance adhere to the surface. A medium flow path member is removably provided in the heating chamber,
A vacuum furnace apparatus characterized in that a cooling medium inlet pipe and a cooling medium discharge pipe, each extending to the outside of the vacuum furnace body, are connected and provided at both ends of the cooling medium flow path member.