JP3466673B2 - Vacuum furnace with movable heat reflector - 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 with a movable heat reflection plate for burning metal or ceramics which is heat-treated at high temperature.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
The vacuum furnace composed of the heat insulating material 3 and the heat insulating material 3 causes almost no temperature difference in the vertical direction in the furnace due to convection. However, in the case of a vacuum furnace, the processed product in the furnace is heated mainly by radiant heat transfer, so that the temperature difference in the furnace is mainly determined by the structure of the heat insulating material. Therefore, the temperature difference of the heat treatment unit 4 in the furnace for heating the processed product is the arrangement of the heaters that are metal heating elements, that is, the heater 1 installed vertically in the entire circumferential direction of the heat treatment unit and the heat treatment unit. It is adjusted by the heater 2 installed over the entire bottom surface of the. Further, the heat generation amounts of the arranged heaters 1 and 2 are adjusted by controlling the power distribution by the thyristors 5 and 6, respectively.
In this method, since the arrangement of the heaters and the distribution of the electric power are determined based on the past experience and experience, the temperature difference is fixed within that range, and it is difficult to obtain a desired temperature difference determined by the processed product. That is, in the conventional technique, since the temperature difference is mainly determined by the furnace structure, there is a problem that the furnace lacks flexibility.

[0003]

On the other hand, firing conditions for treated products, especially temperature difference conditions, have become severe in recent years.
It has become necessary to improve the accuracy of the temperature difference inside the furnace. Furthermore, due to the increase in the number of products to be processed, the number of opportunities to perform different heat treatments in one furnace has increased, and various desired temperature differences have been required for one furnace. An object of the present invention is to provide a vacuum furnace capable of obtaining a desired temperature difference in a heat treatment section for heat treatment of a treated product in order to solve such a problem.

[0004]

In order to achieve such an object, the present invention provides a heating chamber surrounded by a heat insulating material, which has a heat treatment section for heat treating an object to be heated; In a vacuum furnace having a first heating body installed in the vertical direction over the entire circumferential direction of the inside of the heating chamber, and a first control means for controlling the heating amount of the first heating body, in a heating chamber A vacuum characterized in that a movable heat reflection plate that is vertically movable above the heat treatment unit and a movement amount control means for controlling the vertical movement amount of the movable heat reflection plate are provided. Provide a furnace. Further, in the configuration of the present invention, the vacuum furnace further includes a second heating body installed on a bottom surface of the heating chamber, and a second control means for controlling a heating amount of the second heating body. The heating amount of the first heating body and the heating amount of the second heating body may be separately controlled. According to a preferred embodiment of the present invention, the first control means may have a plurality of temperature detection means in the vertical direction of the heat treatment section.

[0005]

The heating amount of the first heating element is controlled by the first control means to bring the temperature of the heating chamber surrounded by the heat insulating material to a steady state, and the amount of vertical movement of the movable heat reflection plate installed in the heating chamber. Is controlled above the heat treatment section by the movement amount control means, the radiant heat from the movable heat reflection plate can be increased or decreased to obtain a desired temperature difference in the vertical direction of the heat treatment section. Furthermore, the heating of the first heating body is performed by using a vacuum furnace further including a second heating body installed on the bottom surface of the heating chamber and a second control means for controlling the heating amount of the second heating body. By separately controlling the amount and the heating amount of the second heating element, a desired temperature difference in the vertical direction of the heat treatment section can be obtained more reliably.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 10 is a vacuum furnace, and the vacuum furnace 10 has a cylindrical body 11, an upper lid 12 and a lower lid 13, and an upper lid 12 and a lower lid 1
Each of the flanges 3 is fastened to the cylindrical body 11 by a fastening means (not shown) such as a bolt at the flange portion, so that the airtightness inside is secured. Inside the vacuum furnace 10, there is a heating chamber 15 surrounded by a heat insulating material 14, and inside the heating chamber 15, there is a heat treatment section 16 for heat-treating a treated product. A side surface heater 17 is installed in the up-down direction over the entire circumferential direction inside the heating chamber 15, and the side surface heater 17 is connected to a temperature controller 19 via a side surface heater thyristor 18. . A bottom surface heater 20 is installed on the entire bottom surface of the heating chamber 15, and this bottom surface heater 20 is connected to a temperature controller 19 via a bottom surface heater thyristor 21 like the side surface heater 17. . A thermocouple 22 for control is installed at a substantially central level in the vertical direction of the heat treatment section 16 so as to detect the temperature of the heat treatment section 16. This control thermocouple 22
Is connected to a temperature controller 19, and the heat generation amounts of the side surface heater 17 and the bottom surface heater 20 are controlled by the thyristors 18 and 21 so that the heat treatment section 16 reaches a steady state of a desired temperature. There is.

Further, at three points of the top, bottom and center of the heat treatment section 16, a thermocouple for temperature measurement (upper) 23a, a thermocouple for temperature measurement (middle) 23b, a thermocouple for temperature measurement (lower) ) 23c is installed so that it is possible to detect the temperature difference in the vertical direction that occurs in the temperature of the heat treatment unit 16 that has reached a steady state. These temperature-measuring thermocouples are respectively connected to the calculator 24, and the temperature difference between the temperature-measuring thermocouple (upper) 23a and the temperature-measuring thermocouple (middle) 23b, the temperature-measuring thermocouple (middle) 23b.
And the temperature difference due to the temperature measuring thermocouple (lower) 23c is calculated. The calculator 24 is connected to the temperature controller 19 and a movement amount controller 26 of the movable heat reflection plate 25, which will be described below, and the side surface heater 17 is controlled by the calculated temperature difference.
And heat generation amount of bottom heater 20 and movable heat reflection plate 25
It is configured to control the movement amount of. A movable heat reflection plate 25 made of molybdenum, which is parallel to the bottom of the heating chamber 15, is installed above the heating chamber 15. The lower surface of the movable heat reflection plate 25, that is, the surface facing the bottom surface of the heating chamber 15 has an emissivity capable of reflecting heat, preferably 0.25 or less. The movable heat reflection plate 25 is connected to the movement amount controller 26, and can move in the heating chamber 15 in the vertical direction within the range from the top of the heating chamber 15 to the upper portion of the heat treatment unit 16.

A method of using the vacuum furnace having the above structure will be described. First, the side surface heater 17 heats the inside of the heating chamber 15 until the heat treatment unit 16 reaches the set temperature. At this time, the side surface heater thyristor 18 detects the temperature of the heat treatment unit 16 by the control thermocouple 22 so that the temperature of the heat treatment unit 16 reaches a steady state at the set temperature.
The amount of heat generated by the side surface heater 17 is controlled by. Next, a thermocouple for temperature measurement (upper) 23a, a thermocouple for temperature measurement (middle) 23b,
The temperature measuring thermocouple (lower) 23c detects the temperature of the heat treatment unit 16 that has reached a steady state, and the calculator 24
Then, the thermocouple for temperature measurement (top) 23a and the thermocouple for temperature measurement (middle) 2
The first temperature difference due to 3b and the second temperature difference due to the temperature measuring thermocouple (middle) 23b and the temperature measuring thermocouple (lower) 23c are calculated.
At this time, the movable heat reflection plate 25 is installed at the top of the heating chamber 15. Then, based on the calculated first and second temperature differences, the movement amount controller 26 lowers the movable heat reflection plate 25 from the top of the heating chamber 15. Radiant heat increases due to the lowering of the movable heat reflection plate 25, and the temperature difference of the heat treatment unit 16 changes. Next, with the movable reflector lowered,
The process waits until the temperature in the heating chamber 15 reaches a steady state, and then the same cycle is repeated, and the movable heat reflection plate 25 is moved in the vertical direction until the desired temperature difference is obtained in the heating chamber 15.

If a desired temperature difference cannot be obtained only by controlling the amount of movement of the movable heat reflection plate 25 in the vertical direction,
Using the bottom heater 20, the thyristors 18 and 21
By adjusting the electric power distribution between the side surface heater 17 and the bottom surface heater 20 and changing the heat generation amount of each, a desired temperature difference can be obtained. With respect to the above vacuum furnace, a temperature difference measurement experiment in the vertical direction of the heat treatment section 16 was conducted for two kinds of set temperatures, 1000 ° C and 1500 ° C. The measurement conditions are shown in Table 1, and the measurement results are shown in Tables 2 and 3.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

As can be seen from Tables 2 and 3, when the movable heat reflection plate 25 is not used but only by the side surface heater 17, the temperature of the heat treatment section 16 in the vertical direction is as follows.
The top, center, and bottom of the heat treatment section 16 are arranged in this order, and the maximum temperature difference is 10 ° C (referenced to the temperature of the center) for both set temperatures of 1000 ° C and 1500 ° C. The effect of the movable heat reflection plate 25 is shown in the middle row of Table 2. The temperature of the central part hardly changed from the case without the movable heat reflection plate, the temperature of the top part and the bottom part both increased to the same temperature, and the maximum temperature difference was improved from 10 ° C to 3 ° C. . Next, the results when the movable reflector and the bottom heater 20 are used are shown in the lowermost row of Tables 2 and 3. Set temperature 1000 ° C
In case of, the temperature at the top, center, and bottom becomes equal,
Even when the set temperature was 1500 ° C, a substantially uniform temperature difference was obtained. As described above, according to the movable heat reflection plate, it is possible to reduce the temperature difference in the vertical direction of the heat treatment unit, and the bottom surface heater is used together with the movable heat reflection plate to distribute the electric power to the side surface heater. It was confirmed that the temperature difference can be further reduced by carrying out.

[0014]

[Effect] According to the present invention, a desired temperature difference can be obtained in the vertical direction of the heat treatment section in the vacuum furnace, and thus a severe temperature difference condition for the processed product can be dealt with. Further, without remodeling the furnace, it is possible to cope with the diversification of the temperature difference due to the diversification of processed products, and to improve the production efficiency.

[Brief description of drawings]

FIG. 1 is a schematic view of a vacuum furnace according to an embodiment of the present invention.

FIG. 2 is a schematic view of a conventional vacuum furnace.

[Explanation of symbols]

10 vacuum furnace 14 Insulation 16 Heat treatment section 15 heating chamber 18 First control means 21 Second control means 23 Temperature detecting means 25 Movable heat reflector 26 Moving amount control means

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F27D 11/02 F27B 17/00 F27D 19/00 G05D 23/19

Claims (3)

(57) [Claims] 1. A heating chamber surrounded by a heat insulating material, which has a heat treatment unit for heat-treating an object to be heated, and a first heating unit installed in a vertical direction over the entire circumference of the inside of the heating chamber. In a vacuum furnace having a body and a first control means for controlling a heating amount of the first heating body, a movable heat reflector movable up and down above the heat treatment unit installed in the heating chamber. A vacuum furnace comprising a plate and a movement amount control means for controlling the vertical movement amount of the movable heat reflection plate. 2. The heating of the first heating body, further comprising a second heating body installed on a bottom surface of the heating chamber, and second control means for controlling a heating amount of the second heating body. The vacuum furnace according to claim 1, wherein the amount and the heating amount of the second heating body are separately controlled. 3. The vacuum furnace according to claim 1, wherein the first control means has a plurality of temperature detection means in the vertical direction of the heat treatment section.