JP2023095992A - industrial furnace - Google Patents

Abstract

To provide an industrial furnace capable of uniform degreasing treatment.SOLUTION: An industrial furnace 10 comprises: a container 12; a heat insulation body 16 arranged in an internal space 14 of the container 12; heaters 20 arranged in an internal space 18 formed by the heat insulation body 16; a tight box 24 arranged in the internal space 18 of the heat insulation body 16 and storing objects 22 to be treated; a pump 32; an exhaust pipe 34 connecting the tight box 24 with the pump 32; a capture device 38 provided in the middle of the exhaust pipe 34 and capturing an emission generated from the object 22 to be treated; a first thermometer 40 measuring temperature of a gas in the exhaust pipe 34; and a control device 64 controlling temperature of the heater 20 according to the temperature measured by the first thermometer 40.SELECTED DRAWING: Figure 1

Description

The present invention relates to industrial furnaces.

2. Description of the Related Art Conventionally, an object to be treated made of metal, magnetic material, or the like is heat-treated in a vacuum or pressurized environment. For example, Patent Document 1 below includes a vacuum chamber, an insulated container in the vacuum chamber, and a heater in the insulated container. An object to be treated is placed in an insulated container. A heating heater heats up the inner space of the heat insulating container, and the object to be treated is degreased and heat-treated.

International publication number WO2016/158029

If the object to be treated is heat treated before it is completely degreased, the heat treatment of the object to be treated will be incomplete. Whether or not it has been degreased is judged by the experience of visual confirmation by an operator of an industrial furnace. The degree of degreasing differs depending on the operator, resulting in variations in the quality of the heat-treated product. When the operator retires, there is a risk that it will no longer be possible to manufacture products of the same quality.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an industrial furnace capable of uniform degreasing treatment.

In order to solve the above problems, an industrial furnace according to the present invention has the following configuration.

The industrial furnace of the present invention comprises a container, a heat insulator arranged in the inner space of the container, a heater arranged in the inner space formed by the heat insulator, a pump, and an exhaust connecting the container and the pump. A pipe, a thermometer for measuring the temperature of the gas in the exhaust pipe, and a controller for controlling the temperature of the heater according to the temperature measured by the thermometer.

Also, a pressure gauge for measuring the pressure of the gas in the exhaust pipe may be provided. Both a thermometer and a pressure gauge may be provided.

According to the present invention, the completion of degreasing can be determined by measuring the temperature of the exhausted gas with a thermometer. Completion of degreasing can also be determined by measuring the gas pressure. Even if anyone operates the industrial furnace, it can be uniformly degreased.

It is a figure which shows the structure of the industrial furnace which measures the temperature of this invention. FIG. 4 shows a configuration for powering the heater; It is a figure which shows the structure of the industrial furnace which measures a pressure. It is a figure which shows the structure of the industrial furnace which measures temperature and pressure.

An industrial furnace of the present invention will be described with reference to the drawings. A plurality of embodiments will be described, but even in different embodiments, the same means may be denoted by the same reference numerals and the description thereof may be omitted.

[Embodiment 1]
The industrial furnace 10 of the present application shown in FIG. 1 contains a container 12, a heat insulator 16 arranged in an internal space 14 of the container 12, a heater 20 arranged in an internal space 18 of the heat insulator 16, and an object 22 to be treated. a tight box (inner case) 24, a gas source 26, a supply pipe 30 connecting the gas source 26 to the interior space 14 of the container 12 or the interior space 18 of the insulator 16 and the interior space 28 of the tight box 24, a pump 32, A first exhaust pipe 34 connecting the pump 32 and the inner space 28 of the tight box 24, a second exhaust pipe 36 connecting the pump 32 and the inner space 14 of the container 12 or the inner space 18 of the insulator 16, and the first exhaust pipe 34 A capture device 38 provided midway and a first thermometer 40 for measuring the temperature of the gas flowing through the first exhaust pipe 34 are provided.

The industrial furnace 10 is a furnace for sintering, semi-sintering, firing, degreasing, brazing, metallizing, quenching, solution treatment, tempering, annealing or aging heat treatment.

[container]
The container 12 comprises a container body 42 and a container lid 44 . The container body 42 has a cylindrical shape. The container lid 44 opens and closes both ends of the container body 42 . When both ends of the container body 42 are closed with container lids 44, the internal space 14 of the container 12 becomes an airtight space. The internal space 14 of the container 12 is either decompressed or pressurized. The pressure resistance of the container 12 is, for example, about 10 MPa, and can be changed by various designs. The container 12 has a double structure consisting of an inner wall 46 and an outer wall 48, between which the coolant flows. When the temperature of the inner space 14 is lowered, it can be lowered by a coolant.

[insulation]
A heat insulator 16 is arranged in the interior space 14 of the container 12 . The insulator 16 comprises an insulator body 50 and an insulator lid 52 . The heat insulator main body 50 is cylindrical. The heat insulator lid 52 opens and closes both ends of the heat insulator main body 50 . An opening/closing device (not shown) for the heat insulator lid 52 is provided so that the heat insulator lid 52 can be opened and closed while the container lid 44 is closed. Insulator 16 is composed of a heat resistant material such as graphite felt or graphite foil.

[heater]
A heater 20 is arranged in the internal space 18 of the heat insulator 16 . The heater 20 may be a rod heater made of graphite. The heater 20 is arranged parallel to the tight box 24 . A plurality of heaters 20 are arranged around the tight box 24 . The power supply circuit 54 shown in FIG. 2 supplies power to the heater 20, and the heater 20 generates heat.

[Power supply circuit]
The power supply circuit 54 is a circuit that supplies three-phase AC power to the heater 20 . The three terminals for three-phase alternating current are R, S, and T. The power supply circuit 54 includes wiring 56 connected to terminals R, S, and T, an ammeter 58 for measuring the current flowing through the wiring 56, a switch 60 for selecting the wiring 56 for power supply, a transformer 62 for power conversion, and a switch 60. A controller 64 for on/off control is provided. Switch 60 can use an element such as a thyristor.

The current value measured by the ammeter 58 and the temperature measured by the second thermometer 66 are input to the controller 64 . A second thermometer 66 measures the temperature of the interior space 18 of the insulator 16 . A controller 64 controls the on/off of the switch 60 so that the temperature of the internal space 18 of the heat insulator 16 reaches a predetermined temperature. The controller 64 is a circuit such as a programmable temperature controller or PLC (Programmable Logic Controller). When the switch 60 is turned on, power is supplied to the heater 20 through the transformer 62 .

[Tight box]
A tight box 24 is arranged in the inner space 18 of the heat insulator 16 . The tight box 24 is made of graphite or the like. The tight box 24 includes a tight box body 68 and a tight box lid 70. - 特許庁The tight box body 68 is cylindrical. The tight box lid 70 opens and closes both ends of the tight box body 68 . An opening/closing device (not shown) for the tight box lid 70 is provided so that the tight box lid 70 can be opened and closed. The internal space 28 of the tight box 24 is sealed by closing both ends of the tight box body 68 with the tight box lid 70 .

[Processed object]
An object 22 to be processed is placed in an internal space 28 of the tight box 24 . Materials of the workpiece 22 are cemented carbide, ferrous metals, non-ferrous metals, magnetic materials, ceramics, graphite, high-speed steel, die steel, low-alloy steel, etc. Metals include alloys. The object 22 to be processed is powder or a solid having a predetermined shape. Since the object 22 to be treated is housed in the tight box 24, the substance released from the object 22 to be treated when the object 22 to be degreased is prevented from being released outside the tight box 24. - 特許庁be able to. Contamination of the inner wall 46 of the container 12, the heat insulator 16, the heater 20, and the like can be prevented.

[Gas source]
Gas source 26 stores, produces, or both nitrogen, argon, hydrogen, carbon monoxide, helium, methane, and the like. The gas source 26 and the internal space 14 of the container 12 or the internal space 18 of the insulator 16 and the internal space 28 of the tight box 24 are connected by a supply pipe 30 . The supply pipe 30 branches and is provided with valves 72 and 74 respectively. The gas flow rate can be controlled by opening and closing valves 72 and 74 . Gas is introduced from the gas source 26 through the supply pipe 30 into the interior space 14 of the container 12 or the interior space 18 of the insulator 16 and the interior space 28 of the tight box 24 . A plurality of gas sources 26 may be provided to supply a plurality of types of gases to the interior space 14 of the container 12 or the interior space 18 of the insulator 16 and the interior space 28 of the tight box 24 . A plurality of supply pipes 30 are provided to supply a plurality of types of gases. Since the heat insulator 16 is not completely airtight, gas can be introduced into either the internal space 14 of the container 12 or the internal space 18 of the heat insulator 16 by introducing the gas into the other.

[pump]
The pump 32 evacuates the interior space 14 of the container 12 or the interior space 18 of the insulator 16 and the interior space 28 of the tight box 24 . The pump 32 and the internal space 28 of the tight box 24 are connected by a first exhaust pipe 34 . The pump 32 and the internal space 14 of the container 12 or the internal space 18 of the insulator 16 are connected by a second exhaust pipe 36 . Pump 32 evacuates interior space 14 of container 12 , interior space 18 of insulator 16 and interior space 28 of tight box 24 . The first exhaust pipe 34 and the second exhaust pipe 36 are provided with valves 76 and 78, respectively, and the exhaust can be controlled by opening and closing the valves 76 and 78 as well. Since the insulator 16 is not completely airtight, exhausting gas from either the internal space 14 of the container 12 or the internal space 18 of the thermal insulator 16 exhausts the gas from the other.

[Trapping device]
When the workpiece 22 is degreased, emissions are emitted that include gaseous binder, particulate dust, or both released from the workpiece. A trapping device 38 is provided for trapping emissions in the first exhaust pipe 34 . Capture device 38 includes wax tank 80 and wax filter 82 . A wax tank 80 is a device for liquefying and storing a binder. The wax filter 82 is a device for collecting particulate dust. No effluent reaches pump 32 .

[thermometer]
A first thermometer 40 is provided on the first exhaust pipe 34 . A first thermometer 40 measures the temperature of the gas flowing through the first exhaust pipe 34 . The first thermometer 40 is a thermometer using a thermocouple. The gas with emissions is at a higher temperature than the gas without. This is because when the degreasing is completed, the heat contained in the expelled matter disappears. By measuring the temperature of the gas, it can be determined whether the gas contains emissions. A first thermometer 40 measures the temperature of the gas upstream from the capture device 38 . By measuring the temperature before the emissions are captured by the trapping device 38, it is possible to determine whether the gas contains emissions.

[Control device]
The temperature of the first thermometer 40 is input to the controller 64 . If the temperature is higher than the predetermined value, the degreasing process is continued. A controller 64 controls the on/off of the switch 60 so as to maintain the temperature of the internal space 18 of the insulator 16 . If the temperature is lower than the predetermined value, the degreasing process is terminated and the process proceeds to the next process. For example, the on/off of the switch 60 is controlled so as to raise the temperature of the internal space 18 of the heat insulator 16 for the heat treatment process.

[others]
A fan 84 may be provided in the interior space 14 of the container 12 . Fan 84 rotates when container lid 44 is closed and insulator lid 52 is opened. The gas circulates through the interior space 14 of the container 12 and the interior space 18 of the insulator 16 . In some cases, the tight box lid 70 can be opened. A motor 86 is attached to the container lid 44 for rotating the fan 84 .

A guide 88 leading from the insulator body 50 to the fan 84 may be provided. Guides 88 direct the circulating gas. The shape of the guide 88 is not limited as long as the direction of gas can be determined. Since the container 12 has a double structure and a cooling liquid flows through it, the circulating gas is cooled by the cooling liquid. A water-cooled heat exchanger 90 may be placed between the fan 84 and the heat insulator 16 to cool the gas as well.

[Heat treatment]
Next, heat treatment using the industrial furnace 10 of the present application will be described. Note that the heat treatment to be described is only an example, and may be changed as appropriate according to the type of the object 22 to be treated and the treatment method.

(1) The workpiece 22 is accommodated in the inner space 28 of the tight box 24, and the tight box lid 70, the heat insulator lid 52 and the container lid 44 are closed.

(2) The pump 32 evacuates the internal space 14 of the container 12, the internal space 18 of the insulator 16, and the internal space 28 of the tight box 24 to a predetermined pressure. At the same time as this evacuation, gas is introduced from the gas source 26 into the internal space 14 of the container 12, the internal space 18 of the heat insulator 16, and the internal space 28 of the tight box 24, and these spaces 14, 18, 28 are filled with a predetermined gas. Fulfill.

(3) The control device 64 controls the switch 60 to apply current to the heater 20 and raise the temperature of the internal space 18 of the heat insulator 16 . The tight box 24 arranged in the internal space 18 of the heat insulator 16 is heated, and the object 22 to be processed is also heated.

The temperature of the workpiece 22 in the inner space 28 of the tight box 24 rises, and the workpiece 22 is degreased. During degreasing, the pump 32 is driven, and the waste generated from the object 22 to be treated is accumulated in the wax tank 80 and the wax filter 82 in the middle of the first exhaust pipe 34 . Gas is supplied to the inner space 28 of the tight box 24 from the gas source 26 as needed. The internal space 28 of the tight box 24 is brought to a predetermined pressure by intake and exhaust. In addition to the inner space 28 of the tight box 24 , the gas may also be supplied from the gas source 26 to the inner space 14 of the container 12 and the inner space 18 of the insulator 16 .

A first thermometer 40 in the middle of the first exhaust pipe 34 measures the temperature of the gas flowing through the first exhaust pipe 34 . The temperature measured by the first thermometer 40 is input to the controller 64 .

If the input temperature is higher than a predetermined value, the controller 64 turns on/off the switch 60 so that the temperature of the internal space 18 of the insulator 16 is maintained. If the temperature of the gas is higher than the predetermined value, the gas contains emissions and the degreasing is not complete. Degreasing is continued while maintaining the temperature of the internal space 18 of the heat insulator 16 . If the temperature input to the controller 64 is less than the predetermined value, the switch 60 is controlled to turn on and off so as to change the temperature of the internal space 18 of the heat insulator 16 . If the temperature of the gas is below a predetermined value, the gas is free of emissions and degreasing is complete. You can proceed to the next step. For example, the current flowing through the heater 20 is increased to raise the temperature of the object 22 to be processed. For example, the workpiece 22 is sintered at approximately 1500° C. or higher.

The temperature is input to the control device 64 after the degreasing is started. After starting degreasing, the temperature may be input to the control device 64 periodically, or the temperature may be input to the control device 64 all the time. Alternatively, the temperature may be input to the control device 64 after a certain period of time has elapsed since the start of degreasing.

(4) Cooling the object 22 after the object 22 is heat-treated. The insulator lid 52 and the tight box lid 70 are opened. The fan 84 is rotated to circulate the gas and cool the object 22 to be processed. During cooling, gas may be introduced from a gas source 26 into the interior space 14 of the container 12 , the interior space 18 of the insulator 16 and the interior space 28 of the tight box 24 .

After the object 22 is cooled, the container lid 44, the insulator lid 52 and the tight box lid 70 are opened and the object 22 is removed.

As described above, by measuring the temperature of the gas exhausted during degreasing, it is possible to determine whether or not degreasing is completed. It is possible to prevent proceeding to the next step before the degreasing is completed.

[Embodiment 2]
The industrial furnace 100 of FIG. 3 has a pressure gauge 102 on the first exhaust pipe 34 instead of the first thermometer 40 of the first embodiment. A pressure gauge 102 measures the pressure of the gas in the first exhaust pipe 34 . The pressure gauge 102 is a diaphragm type pressure gauge. A pressure gauge 102 measures the pressure of the gas downstream of trap 38 . The pressure of the gas in the first exhaust pipe 34 is constant wherever it is measured, and being measured downstream of the capture device 38 prevents contamination of the pressure gauge with emissions.

The pressure measured by pressure gauge 102 is input to control device 64 . If the gas contains emissions, the pressure is high; if it does not, the pressure is low. By measuring the pressure of the gas, it can be determined whether the gas contains emissions. This is because the binder of the object 22 to be processed evaporates and expands.

As in the first embodiment, the controller 64 turns on/off the switch 60 according to the input pressure. If the pressure is higher than the predetermined value, the degreasing process is continued. The gas contains emissions and the degreasing is not complete. A controller 64 turns on/off the switch 60 so as to maintain the temperature of the internal space 18 of the heat insulator 16 . Degreasing is continued. If the pressure is lower than the predetermined value, the degreasing process is terminated and the process proceeds to the next process. The gas is free of emissions and the degreasing is complete. For example, the switch 60 is turned on/off so as to raise the temperature of the internal space 18 of the heat insulator 16 for the heat treatment process.

Pressure is input to the control device 64 after degreasing is started. After starting degreasing, the pressure may be input to the control device 64 periodically, or the pressure may be input to the control device 64 all the time. Alternatively, the pressure may be input to the control device 64 after a certain period of time has elapsed since the degreasing was started.

Completion of degreasing can be determined by measuring the pressure. It is possible to prevent proceeding to the next step before the degreasing is completed.

[Embodiment 3]
The industrial furnace 110 of FIG. 4 has a first thermometer 40 and a pressure gauge 102 on the first exhaust pipe 34 . A first thermometer 40 measures the temperature of the gas upstream from the trap 38 and a pressure gauge 102 measures the pressure of the gas downstream from the trap 38 . That is, the first and second embodiments are combined.

The temperature measured by first thermometer 40 and the pressure measured by pressure gauge 102 are input to controller 64 . The controller 64 turns on/off the switch 60 so that the temperature of the internal space 18 of the insulator 16 is maintained when the temperature is above a predetermined value and the pressure is above a predetermined value or both. Continue the degreasing process as the gas contains emissions. The switch 60 is turned on/off so that the temperature of the internal space 18 of the heat insulator 16 changes when the temperature is less than a predetermined value and the pressure is less than a predetermined value. For example, the switch 60 is turned on/off so that the temperature of the heater 20 is raised for heat treatment.

After starting degreasing, the temperature and pressure are input to the controller 64 . After starting degreasing, the temperature and pressure may be input to the control device 64 periodically, or the temperature and pressure may be input to the control device 64 all the time. Alternatively, the temperature and pressure may be input to the control device 64 after a certain period of time has elapsed since the start of degreasing.

Completion of degreasing can be determined by measuring temperature and pressure. It is possible to prevent proceeding to the next step before the degreasing is completed.

(Section 1) An industrial furnace according to one aspect includes a container, a heat insulator arranged in an internal space of the container, a heater arranged in an internal space formed by the heat insulator, a pump, and the container and a pump, a thermometer for measuring the temperature of the gas in the exhaust pipe, and a controller for controlling the temperature of the heater according to the temperature measured by the thermometer.

According to the industrial furnace described in item 1, the progress of degreasing can be determined by measuring the temperature of the exhausted gas with the thermometer. Completion of degreasing can be determined at the same timing regardless of who operates the industrial furnace.

(Section 2) The thermometer measures the temperature of the gas inside the exhaust pipe.

According to the industrial furnace according to the second aspect, it is possible to determine whether or not the gas contains the emitted matter by measuring the temperature of the gas before the emitted matter is captured by the trapping device.

(Section 3) If the temperature measured by the thermometer is higher than a predetermined value, the controller controls the heater so as to maintain the temperature of the internal space of the heat insulator.

According to the industrial furnace described in item 3, if the temperature of the gas is higher than the predetermined value, the gas contains emissions, degreasing is continued, and the transition to the next step is made to wait.

(Section 4) An industrial furnace according to one aspect includes a container, a heat insulator arranged in an internal space of the container, a heater arranged in an internal space formed by the heat insulator, a pump, and the container and a pump, a pressure gauge for measuring the gas pressure in the exhaust pipe, and a controller for controlling the temperature of the heater according to the pressure measured by the pressure gauge.

According to the industrial furnace described in item 4, the progress of degreasing can be determined by measuring the pressure of the exhausted gas with the pressure gauge. Completion of degreasing can be determined at the same timing regardless of who operates the industrial furnace.

(Section 5) The pressure gauge measures the pressure of the gas inside the exhaust pipe.

According to the industrial furnace according to paragraph 5, the pressure of the gas in the exhaust pipe is the same wherever it is measured, and measuring the pressure of the gas downstream of the capture device ensures that the pressure gauge is contaminated with emissions. can prevent it from being done.

(Section 6) If the pressure measured by the pressure gauge is higher than a predetermined value, the control device controls the heater so as to maintain the temperature of the inner space of the heat insulator.

According to the industrial furnace described in item 6, if the gas pressure is higher than the predetermined value, the gas contains emissions, degreasing is continued, and the transition to the next process is made to wait.

(Section 7) An industrial furnace according to one aspect includes a container, a heat insulator arranged in an internal space of the container, a heater arranged in an internal space formed by the heat insulator, a pump, and the container and a pump, a capture device provided in the middle of the exhaust pipe for capturing emissions generated from the object to be processed, a thermometer for measuring the temperature of the gas in the exhaust pipe, and the exhaust pipe and a controller for controlling the temperature of the heater based on the temperature measured by the thermometer and the pressure measured by the pressure gauge.

According to the industrial furnace described in Item 7, the progress of degreasing can be determined by measuring the temperature of the exhausted gas with the thermometer and the pressure of the exhausted gas with the pressure gauge. Completion of degreasing can be determined at the same timing regardless of who operates the industrial furnace.

(Section 8) The thermometer measures the temperature of the gas inside the exhaust pipe, and the pressure gauge measures the pressure of the gas inside the exhaust pipe.

According to the industrial furnace according to item 8, it is possible to determine whether or not the gas contains emissions by measuring the temperature of the gas before the emissions are captured by the trapping device. Also, the pressure of the gas in the exhaust pipe is the same no matter where it is measured, and measuring the pressure of the gas downstream from the capture device prevents the manometer from becoming contaminated with emissions.

(Section 9) If the temperature measured by the thermometer of the control device is higher than a predetermined value, the pressure measured by the pressure gauge is higher than a predetermined value, or both, the temperature of the internal space of the insulator Control the heater to maintain

According to the industrial furnace according to item 9, if the temperature of the gas is higher than the predetermined value, the pressure of the gas is higher than the predetermined value, or both, the gas contains emissions, and degreasing is not performed. Continue the process and wait for the transition to the next process.

In addition, the present invention can be implemented with various improvements, modifications, and changes based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Each of the described embodiments is not independent, and can be implemented in appropriate combinations based on the knowledge of those skilled in the art.

10, 100, 110: Industrial furnace 12: Container 14: Internal space of container 16: Thermal insulator 18: Internal space of thermal insulator 20: Heater 22: Workpiece 24: Tight box 26: Gas source 28: Inside of tight box Space 30: Supply pipe 32: Pumps 34, 36: Exhaust pipe 38: Capture device 40: Thermometer 64: Control device 102: Pressure gauge

Claims (9)

a container;
a heat insulator disposed in the interior space of the container;
a heater disposed in the internal space formed by the heat insulator;
a pump;
an exhaust pipe connecting the container and the pump;
a thermometer for measuring the temperature of the gas in the exhaust pipe;
a control device for controlling the temperature of the heater according to the temperature measured by the thermometer;
industrial furnace with 2. The industrial furnace of claim 1, wherein said thermometer measures the temperature of the gas inside the exhaust pipe. 3. The industrial furnace according to claim 1, wherein the controller controls the heater so that the temperature of the inner space of the heat insulator is maintained when the temperature measured by the thermometer is higher than a predetermined value. a container;
a heat insulator disposed in the interior space of the container;
a heater disposed in the internal space formed by the heat insulator;
a pump;
an exhaust pipe connecting the container and the pump;
a pressure gauge for measuring the pressure of the gas in the exhaust pipe;
a control device that controls the temperature of the heater according to the pressure measured by the pressure gauge;
industrial furnace with 5. The industrial furnace of claim 4, wherein said pressure gauge measures the pressure of gas inside the exhaust pipe. 6. The industrial furnace according to claim 4 or 5, wherein said controller controls the heater so that the temperature of the inner space of the heat insulator is maintained when the pressure measured by the pressure gauge is higher than a predetermined value. a container;
a heat insulator disposed in the interior space of the container;
a heater disposed in the internal space formed by the heat insulator;
a pump;
an exhaust pipe connecting the container and the pump;
a trapping device provided in the middle of the exhaust pipe for trapping emissions generated from the object to be processed;
a thermometer for measuring the temperature of the gas in the exhaust pipe;
a pressure gauge for measuring the pressure of the gas in the exhaust pipe;
a controller for controlling the temperature of the heater according to the temperature measured by the thermometer and the pressure measured by the pressure gauge;
industrial furnace with 8. The industrial furnace of claim 7, wherein said thermometer measures the temperature of the gas inside the exhaust pipe and said pressure gauge measures the pressure of the gas inside the exhaust pipe. If the temperature measured by the thermometer is higher than a predetermined value, the pressure measured by the pressure gauge is higher than a predetermined value, or both, the controller maintains the temperature of the inner space of the insulator. 9. The industrial furnace according to claim 7 or 8, wherein the heater is controlled.

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