JP7766730B2 - Atmosphere furnace and method for controlling the atmosphere of the atmosphere furnace - Google Patents

Description

The present invention relates to a batch-type atmosphere furnace that subjects an object to a single cycle of heat treatment, including heating, soaking, and slow cooling, and a method for controlling the atmosphere in the atmosphere furnace.

In a heat treatment such as annealing for steel or the like, one cycle of heat treatment includes a process of heating the object, a process of soaking the object, and a process of slowly cooling the object. Such heat treatment is carried out using an atmospheric furnace filled with an atmospheric gas, and the atmosphere in the furnace containing the object, particularly the carbon potential indicating the carbon concentration (carbon equivalent) of the atmosphere, is controlled to be suitable for the heat treatment.
Patent Documents 1, 2, and 3 disclose atmosphere control methods in which an endothermic converted gas is used as the atmospheric gas, and the carbon potential (hereinafter also abbreviated as "CP") of the atmosphere in the furnace is controlled by adjusting the amount of the endothermic converted gas supplied to the furnace.
Patent Document 4 describes an atmosphere control method for a continuous steel pipe annealing furnace equipped with a front chamber, a heating chamber, a cooling chamber, and a rear chamber, in which only endothermic gas is supplied into the furnace from an endothermic gas generator connected to the heating chamber, and the CP of the endothermic gas is adjusted to a value 1.0 to 1.7 times higher than the set value of the CP of the atmosphere in the soaking zone of the heating chamber.
In Patent Documents 1 to 4, the endothermic converted gas (endothermic gas) used as the atmospheric gas is a gas produced by reaction using a hydrocarbon gas such as propane as a raw material, and is composed of a mixed gas containing CO, CO ₂ , H ₂ , N ₂ , etc. CP can be calculated based on the CO concentration and CO ₂ concentration in the atmosphere or gas.

Japanese Patent Application Laid-Open No. 2005-76109 Japanese Patent Application Laid-Open No. 2005-76986 JP 2010-76986 A JP 2015-117396 A

The atmosphere control methods disclosed in Patent Documents 1 to 3 use endothermic converted gas in which the _CO2 concentration is maintained at a constant value (fixed value), and control CP by adjusting the amount of endothermic converted gas supplied to the furnace to increase or decrease it, thereby changing the _CO2 concentration in the furnace. However, controlling CP using these methods tends to waste much of the gas contained in the endothermic converted gas, resulting in poor use of the endothermic converted gas. For example, to increase the _CO2 concentration to control CP, it is necessary to increase the amount of endothermic converted gas supplied to the furnace, but at this time, gases other than _CO2 contained in the endothermic converted gas are not substantially used and are wasted.
The atmosphere control method disclosed in Patent Document 4 controls the CP in the furnace by adjusting the CP of the endothermic converted gas supplied to the heating chamber. While this atmosphere control method has certain advantages when the atmosphere furnace is a continuous type, it is difficult to apply to a batch type. That is, in the case of a continuous atmosphere furnace, the furnace is divided into multiple chambers or zones, such as a heating chamber, a soaking zone, and a slow cooling chamber, so that each chamber or zone can have a separate atmosphere corresponding to each heat treatment. In other words, in a continuous atmosphere furnace, an optimal CP is set for each chamber or zone corresponding to each heat treatment. Therefore, the method disclosed in Patent Document 4 is a control method for maintaining the CP set in each chamber or zone, and is not a CP control method intended to change, for example, an atmosphere suitable for a heating process to an atmosphere suitable for a slow cooling process.
In the case of a batch-type atmosphere furnace, the furnace is usually not divided into multiple chambers or zones, and each heat treatment process, such as heating, soaking, and slow cooling, must be performed essentially in a single furnace chamber. That is, in a batch-type atmosphere furnace, it is necessary to control the temperature and CP so that the atmosphere in the furnace is changed according to each heat treatment. In particular, when the temperature in the furnace is increased or decreased according to each heat treatment, the CP also changes with the temperature change, so in a batch-type atmosphere furnace, it is necessary to control the atmosphere temperature and CP in a coordinated manner.

The present invention seeks to solve these problems associated with conventional technology, and aims to provide an atmosphere furnace and atmosphere control method that can coordinately control the atmosphere temperature and carbon potential, improve the efficiency of endothermic converted gas usage, and are applicable to batch-type furnaces.

In order to solve the above problems, the present invention is presented below.
[1] The atmosphere furnace of the present invention is a batch-type atmosphere furnace that performs heating, soaking, and slow cooling treatments on an object as one cycle of heat treatment,
a furnace body having a furnace chamber for accommodating the object;
a conversion device connected to the furnace body, which generates an endothermic conversion gas from air and a hydrocarbon gas and supplies the endothermic conversion gas to the furnace chamber;
a supplier connected to the converter for supplying the air and the hydrocarbon gas to the converter;
a temperature regulator for adjusting the furnace temperature of the furnace chamber of the furnace body;
an analyzer for analyzing the CO concentration and _CO2 concentration in the furnace chamber of the furnace body;
a controller connected to the transformer and the temperature regulator to control the atmosphere in the furnace chamber;
The controller
a temperature control means for controlling the temperature of the atmosphere by adjusting the furnace temperature using the temperature regulator so that the furnace temperature of the furnace chamber becomes a preset temperature corresponding to each of the heating, soaking, and slow cooling treatments;
A calculation means for calculating an actual measured value of the carbon potential of the atmosphere based on the CO concentration and _CO2 concentration obtained from the analyzer;
and a CP control means for controlling the carbon potential of the atmosphere by adjusting the CO2 concentration in the endothermic converted _gas generated by the converting device so that the actual measured value of the carbon potential becomes a preset carbon potential setting value corresponding to each of the heating, soaking, and slow cooling processes.
[2] The controller can adjust the _CO2 concentration in the endothermic converted gas by adjusting the amount of air supplied from the supplier to the converting device and the amount of hydrocarbon gas supplied in the CP control means.
[3] In the CP control means, the controller can adjust only the amount of air supplied from the supplier to the conversion device to adjust the CO ₂ concentration in the endothermic conversion gas.
[4] The atmospheric furnace of the present invention may include an inert gas supplier connected to the furnace body to supply an inert gas to the furnace chamber.
[5] The atmosphere furnace of the present invention may include a cooler connected between the furnace body and the transformer device to cool the endothermic transformed gas supplied to the furnace chamber.
[6] The atmosphere control method of the present invention for an atmosphere furnace uses a batch-type atmosphere furnace including a furnace body having a furnace chamber, a temperature regulator for adjusting the furnace temperature of the furnace chamber, an analyzer for analyzing the CO concentration and _CO2 concentration in the furnace chamber, a converter for generating an endothermic converted gas from air and a hydrocarbon gas and supplying the endothermic converted gas to the furnace chamber, a supplyer for supplying the air and the hydrocarbon gas to the converter, and a controller for controlling the atmosphere in the furnace chamber, and is an atmosphere control method for subjecting an object placed in the furnace chamber to one cycle of heat treatment, including heating, soaking, and slow cooling,
a temperature control step of controlling the temperature of the atmosphere in the furnace chamber so as to change the atmosphere to one suitable for each of the heating, soaking, and slow cooling treatments, and a CP control step of controlling the carbon potential of the atmosphere in coordination with the temperature control,
The temperature control step includes:
a step of comparing a furnace temperature of the furnace chamber with a preset temperature corresponding to each of the heating, soaking, and slow cooling treatments, and adjusting the furnace temperature by the temperature regulator so that the furnace temperature becomes the preset temperature;
The CP control step includes:
Calculating an actual measured value of the carbon potential of the atmosphere based on the CO concentration and _CO2 concentration obtained from the analyzer;
a step of calculating a variation in carbon potential by comparing a preset carbon potential value with the actual measured value in accordance with each of the heating, soaking, and slow cooling treatments;
The method also includes a step of adjusting the _CO2 concentration in the endothermic converted gas generated by the converting device based on the fluctuation amount so that the actual measured value becomes the set value.
[7] In the atmosphere control method for an atmosphere furnace of the present invention, the carbon content control step can adjust the _CO2 concentration in the endothermic converted gas by adjusting the amount of air supplied from the supply vessel to the converting device and the amount of hydrocarbon gas supplied.
[8] In the atmosphere control method for an atmosphere furnace of the present invention, the carbon content control step adjusts the CO ₂ concentration in the endothermic converted gas by adjusting only the amount of air supplied from the supply device to the converting device.
[9] The atmosphere control method of the present invention is characterized in that, as a step related to the heating treatment,
supplying an inert gas into the furnace chamber to purge the interior of the furnace before supplying the endothermic converted gas into the furnace chamber;
After the purging, the _CO2 concentration in the endothermic converted gas generated by the converting device is adjusted to a minimum value, the amount of the endothermic converted gas supplied from the converting device to the furnace chamber is adjusted to a maximum value, and the supply of the endothermic converted gas to the furnace chamber is started.
[10] In the atmosphere control method for an atmospheric furnace of the present invention, a measuring instrument for measuring the furnace pressure of the atmosphere in the furnace chamber is provided in the furnace body,
a furnace pressure control step of controlling the furnace pressure of the atmosphere after the actual measured value is set to the set value in the carbon content control step,
The furnace pressure control step includes:
The method may include a step of comparing the furnace pressure obtained from the measuring instrument with a preset pressure that is set in advance according to each of the heating, soaking, and slow cooling processes, and adjusting the amount of endothermic converted gas supplied from the converting device to the furnace chamber so that the furnace pressure becomes the set pressure.
[11] The furnace pressure control step according to [10],
When the actual measured value of the carbon potential varies from the set value due to adjustment of the supply amount of the endothermic converted gas, the _CO2 concentration in the endothermic converted gas generated by the converting device is adjusted to set the actual measured value of the carbon potential to the set value.
[12] The atmosphere control method of the present invention is characterized in that, as a step related to the soaking treatment,
a suppression control step of suppressing fluctuations in the carbon potential of the atmosphere during the treatment;
The suppression control step includes:
When the amount of change in the carbon potential exceeds a preset amount according to the soaking treatment, the method may include a step of adjusting the amount of endothermic converted gas supplied from the converting device to the furnace chamber, and/or a step of adjusting the _CO2 concentration in the endothermic converted gas generated by the converting device.
[13] In the atmosphere control method for an atmospheric furnace of the present invention, an inert gas supply device for supplying an inert gas to the furnace chamber is connected to the furnace body;
By adjusting the _CO2 concentration in the endothermic converted gas generated by the converting device and/or adjusting the amount of endothermic converted gas supplied from the converting device to the furnace chamber, when the actual measured value of the carbon potential exceeds the set value, the CO2 concentration in the endothermic converted gas generated by the converting device can be adjusted while supplying inert gas from the inert gas supplier to the furnace chamber to reduce the _CO2 concentration in the furnace chamber.
[14] In the atmosphere control method for an atmosphere furnace of the present invention, a cooler that cools the endothermic converted gas supplied from the converting device to the furnace chamber can be connected to the furnace body to vary the actual measured value of the carbon potential.

The atmosphere furnace of the present invention is a batch-type atmosphere furnace, and a controller equipped with a temperature control means and a CP control means can coordinately control the temperature and carbon potential of the atmosphere in the furnace, and the CP control means can adjust the _CO2 concentration in the endothermic converted gas, thereby improving the efficiency of use of the endothermic converted gas.
The atmosphere control method for an atmosphere furnace of the present invention is provided with a temperature control process and a CP control process in heat treatment using a batch-type atmosphere furnace, thereby enabling coordinated control of the atmosphere temperature and carbon potential, and the CP control process includes a process for adjusting the _CO2 concentration in the endothermic converted gas, thereby improving the efficiency of use of the endothermic converted gas.

FIG. 1 is a block diagram showing an embodiment of an atmospheric furnace according to the present invention. 6 is a graph illustrating the variation of furnace temperature and CP during heat treatment in a furnace chamber in which the ambient temperature and CP are controlled. 1A is a graph illustrating the change in the supply amount of endothermic converted gas and nitrogen gas during heat treatment, and FIG. 1B is a graph illustrating the change in the CO ₂ concentration in the endothermic converted gas and the CO concentration in the furnace. 3 is a flowchart illustrating temperature control in heat treatment as an example of an atmosphere control method of the present invention. 1 is a flowchart illustrating CP control in heat treatment as an example of an atmosphere control method of the present invention.

The matters set forth herein are for illustrative purposes only and are intended to provide an illustrative description of embodiments of the present invention, with the objective of providing what is believed to be the most effective and readily understandable explanation of the principles and conceptual features of the present invention. In this regard, it is not intended to show structural details of the present invention beyond those necessary for a fundamental understanding of the present invention, and the description, taken in conjunction with the drawings, will make clear to those skilled in the art how some aspects of the present invention may be implemented in practice.

[1] Atmosphere Furnace The atmosphere furnace of the present invention is a batch-type atmosphere furnace that performs heating, soaking, and slow cooling treatments on an object as one cycle of heat treatment,
a furnace body having a furnace chamber for accommodating the object;
a conversion device connected to the furnace body, which generates an endothermic conversion gas from air and a hydrocarbon gas and supplies the endothermic conversion gas to the furnace chamber;
a supplier connected to the converter for supplying the air and the hydrocarbon gas to the converter;
a temperature regulator provided in the furnace body for adjusting the furnace temperature of the furnace chamber;
an analyzer provided in the furnace body for analyzing the CO concentration and _CO2 concentration in the furnace chamber;
a controller connected to the transformer and the temperature regulator to control the atmosphere in the furnace chamber;
The controller
a temperature control means for controlling the temperature of the atmosphere by adjusting the furnace temperature using the temperature regulator so that the furnace temperature of the furnace chamber becomes a preset temperature corresponding to each of the heating, soaking, and slow cooling treatments;
A calculation means for calculating an actual measured value of the carbon potential of the atmosphere based on the CO concentration and _CO2 concentration obtained from the analyzer;
and a CP control means for controlling the carbon potential of the atmosphere by adjusting the CO2 concentration in the endothermic converted _gas generated by the converting device so that the actual measured value of the carbon potential becomes a preset carbon potential setting value corresponding to each of the heating, soaking, and slow cooling processes.

FIG. 1 is a block diagram showing an embodiment of an atmospheric furnace according to the present invention.
The atmospheric furnace 10 of the present invention is used to perform heat treatment on an object W. The heat treatment performed by this atmospheric furnace 10 includes heating, soaking, and slow cooling in one cycle. In other words, the atmospheric furnace 10 can be said to perform three treatments, namely, heating, soaking, and slow cooling, on the object W as one cycle of heat treatment.

The heat treatment is not particularly limited with respect to the purpose or method of the treatment, as long as one cycle includes the treatments of heating, soaking, and slow cooling.
The purpose of the treatment can be to remove strain, relieve stress, make the structure uniform, change properties, etc. The treatment method can be annealing, quenching, tempering, normalizing, etc.
A common example of a heat treatment that includes heating, soaking, and slow cooling in one cycle is annealing, which is used to treat an object W made of an iron-based or aluminum-based material, with the purpose of removing distortion, softening the structure, improving ductility, etc.
In addition to the processes of heating, soaking, and slow cooling, the heat treatment can also include processes such as a purging process in which gas inside the furnace chamber is exhausted to the outside of the furnace, a preheating process in which the object is preheated, and a cooling process in which the object is cooled naturally.

Typical atmospheric furnaces include continuous processing furnaces in which objects transported through the furnace are continuously heat-treated, and batch processing furnaces in which objects kept in the furnace are intermittently heat-treated.
The atmospheric furnace 10 of the present invention is a batch-type processing furnace that intermittently heat-treats objects placed in the furnace. The batch-type atmospheric furnace 10 has the advantage of being able to handle a wide variety of objects W, since it is possible to change the temperature conditions, etc., associated with the heat treatment for each cycle. For example, objects made of iron-based materials and objects made of aluminum-based materials can be heat-treated using the same atmospheric furnace 10. Furthermore, the batch-type atmospheric furnace 10 does not require the furnace interior to be divided into multiple chambers, which also has the advantage of simplifying the configuration and saving space.

The object W to be subjected to the atmosphere furnace 10 is not particularly limited in terms of shape, use, material used, etc., as long as it is subject to heat treatment.
The shape of the object W may be linear, tubular, columnar, plate-like, rectangular, or the like.
Examples of uses of the object W include parts for automobiles, devices, and building materials.
Examples of materials used for the object W include iron-based materials such as iron and iron alloys such as steel.
The iron-based material is not particularly limited as long as it is made of iron (Fe) containing carbon (C). In addition to carbon and iron, the iron-based material can include alloys containing silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), nickel (Ni), chromium (Cr), tungsten (W), vanadium (V), molybdenum (Mo), cobalt (Co), etc. Specific examples of the iron-based material include steels such as ordinary steel, special steel, and cast and forged steel, and irons such as cast iron.

Each component of the atmosphere furnace 10 will be described below.
(1) Furnace Body The furnace body 11 is used to actually perform heat treatment on the object W in the batch-type atmospheric furnace 10, and has a furnace chamber (not shown) inside for accommodating the object W (see Figure 1).
In the furnace body 11 corresponding to the batch-type atmospheric furnace 10, the object W undergoing heat treatment is usually kept inside the furnace chamber without being transported, etc. Therefore, the furnace body 11 can have a single furnace chamber without dividing the interior of the furnace into multiple chambers or regions.
Here, the furnace chamber is defined as a chamber for subjecting the object W to heat treatment including heating, soaking, and slow cooling in one cycle, that is, a chamber for subjecting the object W to at least three treatments, namely, heating treatment, soaking treatment, and slow cooling treatment.
That is, the furnace body 11 of the batch-type atmospheric furnace 10 can have one furnace chamber within the furnace, and is configured so that the object W placed in that one furnace chamber can be subjected to heat treatment including heating, soaking, and slow cooling.

The furnace body 11 may be of any construction, material used, shape, size, furnace internal volume, heating and cooling method, etc., as long as it is compatible with the batch-type atmospheric furnace 10.
The furnace body 11 may be configured to have an opening for loading and unloading the object W into and out of the furnace chamber that can be opened and closed by a door or the like, in order to accommodate the batch-type atmospheric furnace 10. In this case, the opening can be closed during heat treatment to prevent air (outside air) from entering the furnace chamber, thereby stabilizing the atmosphere in the furnace chamber.

The furnace body 11 may be provided with a furnace chamber for carrying out heat treatments including heating, soaking, and slow cooling, as well as chambers for treatments other than heat treatments, such as a front chamber and a rear chamber.
The antechamber can be a chamber in which the object W is kept waiting before being heat-treated, or a chamber in which the object W is preheated before being heat-treated.
The rear chamber can be a chamber for storing the object W after heat treatment, or for allowing the object W after heat treatment to cool to room temperature.

The furnace body 11 may be equipped with an exhaust means (not shown) for exhausting gases inside the furnace chamber to the outside of the furnace. Examples of the exhaust means include an exhaust pipe connected to the furnace body 11, an on-off valve connected to the exhaust pipe for opening and closing the exhaust pipe, and a damper connected to the exhaust pipe for adjusting the amount of gas exhausted to the outside of the furnace. The furnace body 11 equipped with the exhaust means can exhaust gases inside the furnace chamber, such as air and unburned gases, to the outside of the furnace.
The air contained in the furnace chamber of the furnace body 11 is mainly derived from the outside air that has entered the furnace chamber, and the oxygen (O ₂ ) contained in the air can cause problems such as abnormal combustion when endothermic converted gas is supplied to the furnace chamber and oxidizing the object W during heat treatment. For this reason, at the start and end of heat treatment, it is desirable to create an oxygen-free atmosphere inside the furnace by performing a purging process using an exhaust means to exhaust the air (oxygen) inside the furnace chamber to the outside of the furnace.

(2) Transformer and Supply The transformer 12 generates endothermic transformed gas (hereinafter also referred to as "RX gas") from air and hydrocarbon gas. The transformer 12 is connected to the furnace body 11 via a first supply system 21 (see FIG. 1).
The transformer 12 can supply the generated RX gas to the furnace chamber of the furnace body 11. The RX gas supplied to the furnace chamber of the furnace body 11 can be used as an atmospheric gas that creates an atmosphere in the furnace chamber suitable for heat treatment of the object W.
A first adjusting valve 22 can be connected to the first supply system 21 (see FIG. 1 ). When the first adjusting valve 22 is connected, the amount of RX gas supplied from the transformer 12 to the furnace body 11 can be adjusted by adjusting the opening degree of the first adjusting valve 22.

The supply device 13 is for supplying air and hydrocarbon gas to the shift converter 12. The supply device 13 is connected to the shift converter 12 via an air supply system 31 and a raw material supply system 32 (see FIG. 1).
The supplier 13 can supply air to the shift converter 12 via an air supply system 31 and can supply hydrocarbon gas via a raw material supply system 32 .
An air adjustment valve 31A can be connected to the air supply system 31. When the air adjustment valve 31A is connected, the amount of air supplied from the supplier 13 to the transformer device 12 can be adjusted by adjusting the opening of the air adjustment valve 31A.
A raw material adjustment valve 32A can be connected to the raw material supply system 32. When the raw material adjustment valve 32A is connected, the supply amount of hydrocarbon gas supplied from the supply device 13 to the shift converter 12 can be adjusted by adjusting the opening degree of the raw material adjustment valve 32A.

The hydrocarbon gas used in the shift converter 12 and the supply unit 13 is not particularly limited, and examples thereof include methane gas, butane gas, and propane gas, and typically propane gas can be used.
The converter 12 uses hydrocarbon gas as a raw material, mixes it with air, and reacts the _hydrocarbon gas (propane gas; _C3H8 ) with the oxygen ( _O2 ) contained in the air as shown in the following formula (1), thereby generating carbon monoxide (CO) and hydrogen ( _H2 ).
C ₃ H ₈ + (3/2) O ₂ → 3CO + 4H ₂ ...Formula (1)

In addition to oxygen (O ₂ ), air also contains carbon dioxide (CO ₂ ), nitrogen (N ₂ ), and moisture (H ₂ O), and the mixed gas of these with the above-mentioned carbon monoxide (CO) and hydrogen (H ₂ ) is called RX gas.
That is, the RX gas generated from air and hydrocarbon gas in the conversion device 12 is a mixed gas containing multiple types of gases such as carbon monoxide (CO), hydrogen (H ₂ ), carbon dioxide (CO ₂ ), moisture (H ₂ O), and nitrogen (N ₂ ).

The configuration of the converter 12 is not particularly limited as long as it can generate RX gas from air and hydrocarbon gas, but it can be equipped with a catalyst for reacting air with hydrocarbon gas. A nickel catalyst can usually be used as the catalyst, and the catalyst can be heated to a high temperature (about 1000 to 1100°C) and the air and hydrocarbon gas can be brought into contact with each other to cause them to react.
The supply device 13 is not particularly limited in configuration, etc., as long as it can supply air and hydrocarbon gas to the shift conversion device 12. As a specific example, the supply device 13 may include an air blower such as a blower, compressor, fan, etc. for supplying air to the shift conversion device 12. Furthermore, as a specific example, the supply device 13 may include a tank, cylinder, etc. for storing hydrocarbon gas in order to supply the hydrocarbon gas to the shift conversion device 12.
The first adjusting valve 22, the air adjusting valve 31A, and the raw material adjusting valve 32A are not particularly limited in type as long as they can be operated by the controller 16 and can open and close the systems to which they are connected, and for example, solenoid valves, motor-operated valves, etc. can be used. Among these, motor-operated valves are preferable for use as the first adjusting valve 22, the air adjusting valve 31A, and the raw material adjusting valve 32A, because the amount of opening and closing can be adjusted by operation by the controller 16.

The converter 12 can be used in conjunction with the supplier 13 to adjust the _CO2 concentration in the RX gas.
That is, the converter 12 and the supply device 13 have a CP control means provided in the controller 16 to control the carbon potential (hereinafter also abbreviated as "CP") of the atmosphere in the furnace chamber, and have the function of adjusting the _CO2 concentration in the RX gas so that the furnace chamber of the furnace body 11 has a CP atmosphere suitable for each process of heating, soaking, and slow cooling in the heat treatment.
The CP suitable for each of the heating, soaking, and slow cooling processes can be determined in advance depending on the material (e.g., iron-based material, etc.) used for the object W, the purpose of the heat treatment (e.g., annealing, etc.), etc. Therefore, the CP suitable for each of the heating, soaking, and slow cooling processes can be stored in the controller 16 as a preset temperature setting. The controller 16 can then control the CP of the atmosphere by operating the air adjustment valve 31A and raw material adjustment valve 32A of the supply device 13 to adjust the _CO2 concentration in the RX gas supplied to the furnace chamber so that the CP of the atmosphere in the furnace chamber becomes the set value corresponding to each process.

One method for adjusting the CO ₂ concentration is to adjust the amount of air and the amount of hydrocarbon gas supplied from the supply device 13 to the shift converter 12 .
Another method for adjusting the CO ₂ concentration is to adjust only the amount of air supplied from the supplier 13 to the shift converter 12 .

Specifically, when the _CO2 concentration is increased by adjusting the amount of air supplied and the amount of hydrocarbon gas supplied, the amount of air supplied to the shift converter 12 is increased and/or the amount of hydrocarbon gas supplied is decreased.
When the amount of air supplied is increased, the amount of carbon dioxide ( _CO2 ) in the RX gas increases accordingly, resulting in a higher _CO2 concentration. On the other hand, when the amount of hydrocarbon gas supplied is decreased, the amounts of carbon monoxide (CO) and hydrogen ( _H2 ) in the RX gas decrease accordingly, resulting in a higher _CO2 concentration in the RX gas.

When the CO ₂ concentration is reduced by adjusting the amounts of air and hydrocarbon gas supplied, the amount of air supplied to the shift converter 12 is reduced and/or the amount of hydrocarbon gas supplied is increased.
When the amount of air supplied is reduced, the amount of carbon dioxide ( _CO2 ) in the RX gas is correspondingly reduced, resulting in a lower _CO2 concentration. On the other hand, when the amount of hydrocarbon gas supplied is increased, the amounts of carbon monoxide (CO) and hydrogen ( _H2 ) in the RX gas are increased, resulting in a lower _CO2 concentration in the RX gas.

In practice, the CO ₂ concentration in the RX gas can be easily adjusted by simply adjusting the amount of air supplied from the supplier 13 to the converter 12 .
Alternatively, when adjusting the _CO2 concentration in the RX gas, or when fine and precise adjustment of the _CO2 concentration is required, it is desirable to adjust both the amount of air supplied and the amount of hydrocarbon gas supplied.

Specifically, when increasing the _CO2 concentration by adjusting only the amount of air supplied, the amount of air supplied to the converter 12 is increased, and accordingly the amount of carbon dioxide ( _CO2 ) in the RX gas increases, increasing the _CO2 concentration.
Alternatively, when the _CO2 concentration is reduced by adjusting only the amount of air supplied, the amount of air supplied to the converter 12 is reduced, and the amount of carbon dioxide ( _CO2 ) in the RX gas is reduced accordingly, thereby reducing the _CO2 concentration.

When adjusting the _CO2 concentration in the RX gas by adjusting only the amount of air supplied, it is desirable to always supply a constant amount (fixed amount) of hydrocarbon gas to the converter 12. In this case, oxygen ( _O2 ) contained in the air reacts with the hydrocarbon gas and is eliminated, so that oxygen ( _O2 ) can be prevented from being supplied to the furnace body 11.
When a constant amount (fixed amount) of hydrocarbon gas is always supplied to the shift converter 12, it is not necessary to react all of the oxygen (O ₂ ) in the air supplied to the shift converter 12 with the hydrocarbon gas. If some oxygen (O ₂ ) remains unreacted with the hydrocarbon gas, this unreacted oxygen can be eliminated by reacting it with hydrogen (H ₂ ) or carbon monoxide (CO).

At first glance, adjusting the CO ₂ concentration in the RX gas using the supplier 13 and the converter 12 may appear to adjust the CP of the RX gas, but in this application, the CP of the RX gas is not actually taken into consideration.
In other words, controlling the CP of the atmosphere by adjusting the CP of the RX gas has considerable advantages in terms of maintaining the CP of the atmosphere of the chamber or area when the CP of the RX gas is approximately equal to the CP of the atmosphere of the chamber or area to which the RX gas is supplied.
However, in the present application, the atmosphere in one furnace chamber is changed to an atmosphere suitable for each of the heating, soaking, and slow cooling processes included in the heat treatment, and the CP of the furnace chamber atmosphere also varies depending on each process.
In other words, the CP control of the atmosphere in the furnace chamber in this application is control for varying the CP of the atmosphere in the furnace chamber in accordance with each of the heating, soaking, and slow cooling processes included in the heat treatment, and is different from control for maintaining the CP of the atmosphere.
In addition, in the present application, CP control of the atmosphere in the furnace chamber is performed by adjusting the CO ₂ concentration in the RX gas, but it can also be said that CP control is essentially performed by adjusting the amount of CO ₂ supplied to the furnace chamber.

(3) Temperature Regulator The temperature regulator 14 is used to regulate the furnace temperature in the furnace chamber of the furnace body 11, that is, the temperature of the atmosphere in the furnace chamber.
The temperature regulator 14 is electrically connected to a controller 16 (see FIG. 1), and the controller 16 can control, for example, the ON/OFF operation of the temperature increase or decrease.
The temperature regulator 14 is not particularly limited in terms of configuration, etc., as long as it is capable of adjusting the furnace temperature.
For example, the temperature regulator 14 may include a heat exchanger (not shown) provided in the furnace chamber of the furnace body 11. Specifically, examples of the heat exchanger include a radiant tube burner or a cooling tube, which passes a heat medium such as combustion gas or a refrigerant such as air through a tubular heat exchange tube to raise or lower the furnace temperature in the furnace chamber by heat exchange.
Alternatively, the temperature regulator 14 may include a measuring device such as a thermocouple that can measure the furnace temperature.

The temperature regulator 14 is controlled by the controller 16 and adjusts the furnace temperature of the furnace chamber of the furnace body 11, thereby changing the furnace temperature to a temperature suitable for each process of heating, soaking, and slow cooling in the heat treatment.
That is, the temperature regulator 14 is a temperature control means provided in the controller 16 for controlling the temperature of the atmosphere in the furnace chamber, and has the function of adjusting the temperature of the atmosphere in the furnace chamber so that the furnace chamber of the furnace body 11 has a furnace temperature suitable for each process of heating, soaking, and slow cooling in the heat treatment.
The optimum temperature for each of the heating, soaking, and slow cooling processes can be determined in advance depending on the material (e.g., iron-based material, etc.) used for the object W, the purpose of the heat treatment (e.g., annealing, etc.), etc. Therefore, the optimum temperature for each of the heating, soaking, and slow cooling processes can be stored in the controller 16 as a preset temperature setting, and the temperature regulator 14, whose operation is controlled by the controller 16, adjusts the furnace temperature to the set temperature (optimum temperature) corresponding to each process, thereby controlling the temperature of the atmosphere.

Specifically, in the heating process, the temperature regulator 14 is controlled so that the temperature increase operation is turned on, and the temperature of the furnace is adjusted to increase. The increase in the furnace temperature in the heating process continues until the furnace temperature reaches the set temperature according to the soaking process, and the temperature can usually be adjusted to increase at a constant rate.
In the soaking process, the temperature regulator 14 controls the ON/OFF of the temperature increase operation and can adjust the furnace temperature to maintain it at a set temperature according to the soaking process. The furnace temperature is maintained for a predetermined processing time, and usually, upper and lower limit values of the furnace temperature are set and the furnace temperature can be adjusted to maintain it within the range between the upper and lower limit values.
In the slow cooling process, the temperature regulator 14 is controlled so that the temperature lowering operation is turned on, and the temperature can be adjusted to lower the furnace temperature. The lowering of the furnace temperature in this slow cooling process continues until the furnace temperature reaches a predetermined set temperature, and the temperature can usually be adjusted to lower at a constant rate.

(4) Analyzer The analyzer 15 is used to analyze the CO concentration and _CO2 concentration in the furnace chamber of the furnace body 11.
The analyzer 15 is electrically connected to the controller 16 (see FIG. 1 ), and can input information relating to the analyzed CO concentration and CO ₂ concentration to the controller 16 .
The analyzer 15 is not particularly limited in configuration, etc., as long as it is capable of analyzing the CO concentration and CO ₂ concentration in the furnace chamber.
For example, the analyzer 15 may include a measuring instrument (not shown) that is provided in the furnace chamber of the furnace body 11 and measures the CO concentration and _CO2 concentration. Specifically, the measuring instrument may include sensors such as a CO sensor and a _CO2 sensor.

In this application, the CP and temperature of the furnace chamber atmosphere are controlled in coordination because CP varies with temperature (furnace temperature). In other words, to control CP, it is necessary to obtain an actual measured value of CP as CP that varies with temperature (furnace temperature).
The analyzer 15 is a calculation means provided in the controller 16 for determining the actual measured value of CP, and has a function of analyzing the CO concentration and _CO2 concentration during each of the heating, soaking, and slow cooling processes of the heat treatment.
Specifically, the analyzer 15 can analyze the CO concentration and _CO2 concentration in the furnace chamber of the furnace body 11 constantly or at regular intervals. Information on the CO concentration and _CO2 concentration analyzed by the analyzer 15 is input to the controller 16 and used to calculate the actual measured value of CP.

(5) Controller The controller 16 controls the atmosphere in the furnace chamber of the furnace body 11 according to the heating, soaking, and slow cooling processes of the heat treatment, and more specifically, controls the temperature and CP of the atmosphere in the furnace chamber in a coordinated manner.
The controller 16 is electrically connected to the temperature regulator 14 and can operate the temperature regulator 14. The controller 16 includes a temperature control means for operating the temperature regulator 14 to adjust the furnace temperature and control the ambient temperature so that the furnace temperature in the furnace chamber becomes a preset temperature corresponding to each of the heating, soaking, and slow cooling processes.
The controller 16 is electrically connected to the analyzer 15 and can obtain information on the CO concentration and _CO2 concentration in the furnace chamber analyzed by the analyzer 15. The controller 16 is provided with a calculation means for calculating the actual measured value of the CP of the atmosphere based on the CO concentration and _CO2 concentration obtained from the analyzer 15.

The controller 16 is electrically connected to the air adjustment valve 31A and the raw material adjustment valve 32A of the supplier 13, and can adjust the amounts of air and hydrocarbon gas supplied from the supplier 13 to the shift converter 12 by operating the air adjustment valve 31A and the raw material adjustment valve 32A. The controller 16 is equipped with CP control means that adjusts the amounts of air and hydrocarbon gas supplied from the supplier 13 to the shift converter 12, or only the amount of air supplied, and adjusts the _CO2 concentration in the RX gas generated by the shift converter 12.
The controller 16 is also electrically connected to the first adjusting valve 22 of the transformer 12, and can adjust the amount of RX gas supplied from the transformer 12 to the furnace chamber of the furnace body 11 by operating the first adjusting valve 22. The CP control means included in the controller 16 adjusts the _CO2 concentration in the RX gas and, if necessary, adjusts the amount of RX gas supplied to the furnace chamber, thereby controlling the CP of the atmosphere so that the actual measured value of the CP of the atmosphere obtained by the calculation means becomes the set value of CP that is preset in accordance with each of the heating, soaking, and slow cooling processes.

Specifically, the controller 16 has a built-in electronic calculator (computer) that includes a processing unit such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and a storage area unit such as an HDD, an SSD, and a ROM.
The temperature control means, the calculation means, and the CP control means are stored as programs in the storage area of the controller 16 .
In addition, the temperatures suitable for each of the heating, soaking, and slow cooling processes included in the heat treatment are stored as preset set temperatures, and the CP suitable for each process is stored as a preset CP set value in the memory area section of the controller 16.
The controller 16 can coordinately control the temperature and CP of the furnace chamber atmosphere by having an electronic calculator (computer) execute a temperature control means, a calculation means, and a CP control means as a program stored in the memory area based on the set temperature and CP set values stored in the memory area.

In addition, when the controller 16 is electrically connected to the first adjusting valve 22 of the transformer 12, it can control the furnace pressure in the furnace chamber by adjusting the amount of RX gas supplied from the transformer 12 to the furnace chamber of the furnace body 11.
That is, in a heat treatment including heating, soaking, and slow cooling, the furnace pressure may change with a change in furnace temperature. Such a change in furnace pressure may cause problems such as condensation and clogging in the first supply system 21. Therefore, it is desirable to perform furnace pressure control to suppress the change in furnace pressure.

Regarding furnace pressure control, the furnace body 11 may be provided with a measuring instrument 19 for measuring the furnace pressure of the atmosphere in the furnace chamber, and this measuring instrument 19 may be electrically connected to the controller 16 (see FIG. 1).
The measuring instrument 19 is not particularly limited in type as long as it can measure the pressure in the furnace chamber (furnace pressure), and a pressure sensor or the like can be used.
The controller 16 can store pressures suitable for the heating, soaking, and slow cooling processes in the storage area as preset pressures.

Furnace pressure control can be performed by comparing the furnace chamber pressure obtained from the measuring instrument 19 with a preset set pressure and adjusting the amount of RX gas supplied from the transformer 12 to the furnace chamber so that the furnace pressure becomes the set pressure.
In addition, the CP control means provided in the controller 16 performs CP control by adjusting the _CO2 concentration in the RX gas and the amount of RX gas supplied to the furnace chamber. However, since the furnace pressure also changes during this CP control, it is desirable to perform furnace pressure control after the actual measured value of CP (FP) is set to the set value in CP control.
Alternatively, if the actual measured value of CP (FP) deviates from the set value as a result of adjusting the amount of RX gas supplied to the furnace chamber for furnace pressure control, it is desirable that the controller 16 executes CP control again to change the actual measured value of CP (FP) to the set value.

(6) Temperature Control Means The temperature control means is a program for controlling the temperature of the atmosphere in the furnace chamber.
The temperature control means controls the furnace temperature, which is the temperature of the atmosphere in the furnace chamber, to a temperature suitable for each of the heating, soaking, and slow cooling processes of the heat treatment, by varying the furnace temperature according to each process.
In the temperature control means, the furnace temperature can be an actual value measured by a thermocouple or the like provided in the temperature regulator 14. Furthermore, the temperature suitable for each of the heating, soaking, and slow cooling processes in the heat treatment can be a preset temperature set according to each process.
That is, the temperature control means compares the measured furnace temperature with the set temperature, and if the two values differ, executes temperature control to change the furnace temperature of the atmosphere in the furnace chamber to match the set temperature.

FIG. 2 is a graph illustrating the changes in furnace temperature and CP during heat treatment in a furnace chamber in which the temperature and CP of the atmosphere are controlled by the temperature control means and the CP control means.
In the heating process of the heat treatment, the temperature control means controls the temperature so that the furnace temperature is increased over time. Specifically, the furnace temperature during the heat treatment is increased over time from the starting temperature (T ₀ ) to a soaking temperature (T ₁ ) that is a temperature suitable for the soaking process (see FIG. 2 ).

In the soaking process of the heat treatment, the temperature control means controls the temperature so as to maintain the furnace temperature until the treatment time has elapsed. Specifically, the furnace temperature during the soaking process is maintained at the soaking temperature (T ₁ ) until the treatment time for the soaking has elapsed (see FIG. 2 ).
In the slow cooling process of the heat treatment, the temperature control means controls the temperature so that the furnace temperature is slowly lowered over time. Specifically, the furnace temperature during the slow cooling process is lowered over time from the soaking temperature ( _T1 ) to an end temperature ( _T2 ), which is a temperature suitable for the end of the slow cooling process, until the processing time for the slow cooling has elapsed (see FIG. 2).

The starting temperature (T ₀ ) can be set arbitrarily and is not particularly limited. The soaking temperature (T ₁ ) and the ending temperature (T ₂ ) are preset temperatures that can be set in advance to be appropriate depending on the material used for the object, the heat treatment method, etc., and are not particularly limited.
As a specific example, when the material used for the object is an iron-based material and the heat treatment method is annealing, the starting temperature (T ₀ ) can be preferably 300 to 700°C, more preferably 400 to 650°C, and even more preferably 500 to 600°C.

When the material used for the object is an iron-based material and the heat treatment method is annealing, the soaking temperature (T ₁ ) can be preferably 600 to 1000° C., more preferably 650 to 950° C., and even more preferably 680 to 900° C. The treatment time for soaking can be preferably 150 to 450 minutes, more preferably 200 to 400 minutes, and even more preferably 250 to 350 minutes.
When the material used for the object is an iron-based material and the heat treatment method is annealing (particularly, spheroidizing annealing), the end temperature (T ₂ ) can be set to 450 to 700° C., more preferably 500 to 680° C., and even more preferably 550 to 650° C. The slow cooling gradient (temperature drop rate, specifically, temperature drop per hour) for slow cooling can be set to preferably 5 to 50° C./h, more preferably 10 to 40° C./h, and even more preferably 15 to 30° C./h.

(7) Calculation Means The calculation means is a program for calculating the actual measured value of CP of the atmosphere in the furnace chamber.
The calculation means performs calculations to calculate the actual measured value of CP of the atmosphere in the furnace chamber based on the CO concentration and _CO2 concentration obtained from the analyzer.

Specifically, CP can be calculated by the following formula (2).
CP = [(CO concentration) ² × Cs] ÷ [(CO ₂ concentration) × K] ... Formula (2)
In formula (2), Cs represents the saturated carbon concentration in the material used for the object.
In addition, in formula (2), K is an equilibrium constant, which can be calculated from the formula K = (CO concentration) ² ÷ [C × (CO ₂ concentration)] (where C = CP/ _Cs ) based on the Boudouard reaction shown as "C + CO 2 = 2CO".

In the above formula (2), Cs and K are constants. Therefore, the potential factor (hereinafter also abbreviated as "PF") calculated by the following formula (3) can be treated as a value synonymous with CP.
PF = (CO concentration) ² ÷ (CO ₂ concentration) ... Formula (3)

Regarding CP control, from equation (2) or equation (3), CP(PF) can be increased by lowering the CO ₂ concentration, and can be decreased by increasing the CO ₂ concentration.
Therefore, in CP control, the CP (PF) of the atmosphere in the furnace chamber can be controlled by adjusting the _CO2 concentration in the RX gas, in other words, by adjusting the amount of _CO2 supplied to the furnace chamber.
Specifically, in CP control, when CP (PF) is to be increased in each of the heating, soaking, and slow cooling processes included in the heat treatment, the _CO2 concentration in the RX gas is adjusted to be lower, and when CP (PF) is to be decreased, the _CO2 concentration in the RX gas is adjusted to be higher, thereby controlling the CP (PF) of the atmosphere in the furnace chamber.

(8) CP Control Means The CP control means is a program for controlling the CP (PF) of the atmosphere in the furnace chamber.
The CP control means performs CP control to vary the CP (PF) of the atmosphere in the furnace chamber according to each process, in order to obtain a CP (PF) suitable for each process of heating, soaking, and slow cooling in the heat treatment.
In the CP control means, the CP(PF) of the atmosphere in the furnace chamber can be the actual measured value of CP(PF) calculated by the above-mentioned calculation means based on the CO concentration and _CO2 concentration obtained from the analyzer. Also, the CP(PF) suitable for each of the soaking and slow cooling processes can be a preset CP(PF) value corresponding to each process.
That is, the CP control means compares the actual measured value of CP (PF) with the set value of CP (PF), and if the two values differ, performs CP control to vary the CP (PF) of the atmosphere in the furnace chamber to match the set value of CP (PF).

As shown in Fig. 2, in the heating process of the heat treatment, the CP control means executes CP control so as to increase the CP (PF) of the atmosphere in the furnace chamber over time. Specifically, the CP (PF) during the heat treatment can be increased over time from an initial value ( _C0 ) to a treatment value ( _C1 ) that is a value suitable for the soaking process.
In the soaking process of the heat treatment, the CP control means executes CP control so as to maintain CP (PF) until the processing time has elapsed. Specifically, the CP (PF) during the soaking process can be maintained at the processing value (C ₁ ) until the processing time for soaking has elapsed (see FIG. 2).
In the slow cooling process of the heat treatment, the CP control means executes CP control so as to decrease the CP (PF) over time. Specifically, the CP (PF) during the slow cooling process can be decreased over time from a processing value (C ₁ ) to an end value (C ₂ ), which is a CP (PF) suitable for the end of the slow cooling process, until the processing time for the slow cooling has elapsed (see FIG. 2 ).

The initial value (C ₀ ) is a temperature that can be set arbitrarily and is not particularly limited. The process value (C ₁ ) and the end value (C ₂ ) are set values that can be set in advance to set an appropriate CP depending on the material used for the object, the heat treatment method, etc., and are not particularly limited.
As a specific example, if the material used for the object is an iron-based material such as S10C or S40C carbon steel for mechanical structures, and CO and _CO2 are in equilibrium in the Boudouard reaction (C + _CO2 = 2CO), the PF values (calculated values) at each temperature in the range of 700 to 850°C are as follows:
S10C; 15 (700°C), 35 (750°C), 73 (800°C), 147 (850°C).
S40C; 62 (700°C), 141 (750°C), 292 (800°C), 589 (850°C).
The initial value (C ₀ ), processing value (C ₁ ), and end value (C ₂ ) are set to an appropriate PF value (CP value) depending on the change in furnace temperature during heat treatment (heat pattern, see, for example, "furnace temperature" in FIG. 2 ). For example, in the case of S10C, if the soaking treatment is performed at 700°C, the processing value (C ₁ ) can be set to a PF value of 15, and if the soaking treatment is performed at 800°C, the processing value (C ₁ ) can be set to a PF value of 73.

The CP control means performs CP control by adjusting the _CO2 concentration in the RX gas, and also adjusts the amount of RX gas supplied to the furnace chamber as necessary.
FIG. 3(a) is a graph illustrating an example of changes in the supply amounts of RX gas and nitrogen gas during heat treatment, and FIG. 3(b) is a graph illustrating an example of changes in the _CO2 concentration in the RX gas and the CO concentration in the furnace chamber.
In the heating process of the heat treatment, the CP control means can adjust the supply amount of RX gas to the maximum value (100%) (see FIG. 3(a)) in order to fill the furnace chamber with RX gas in the shortest possible time.
During the heat treatment, the CO concentration in the furnace chamber increases over time due to the supply of RX gas (see FIG. 3(b)). As the CO concentration increases, CP also increases over time (see FIG. 2).
In addition, in the heat treatment, the CP control means can adjust the _CO2 concentration in the RX gas to the minimum value ( _d0 ) (see Figure 3(b)). This is to maximize the supply amount of RX gas and increase the CP (PF) of the atmosphere in the furnace chamber to the set value CP (PF) related to the CP control as quickly as possible, thereby shortening the time it takes for the CP (PF) of the atmosphere in the furnace chamber to reach the treatment value ( _C1 ) from the initial value ( _C0 ).

In the soaking process of the heat treatment, the CP control means can adjust the supply amount of RX gas to be reduced from the maximum value (100%) to a steady value ( _V1 ) at the start of the process. Furthermore, during the soaking process, the CP control means can adjust the supply amount of RX gas to be approximately maintained at the steady value ( _V1 ) or to be gradually reduced within a range from the steady value ( _V1 ) to a value slightly lower than the steady value ( _V1 ) (see FIG. 3(a)).
The reason for reducing the supply amount of RX gas to a steady-state value (V ₁ ) at the start of processing is to reduce the waste of RX gas by limiting the supply amount of RX gas to approximately the amount required to maintain the furnace pressure in the furnace chamber (furnace pressure control).

During the soaking treatment, the CP control means executes CP control so as to maintain the CP (PF) at a constant value (treatment value: C ₁ ) until the treatment time has elapsed.
Therefore, in the soaking treatment, it is desirable to perform suppression control so as to suppress fluctuations in the CP (PF) of the atmosphere during the treatment.
In the suppression control, the amount of fluctuation in CP (PF) that is allowable in the soaking treatment can be used as a preset amount. The preset amount can be stored in the storage area of the controller 16, for example.
The suppression control can be performed when the fluctuation amount of CP (PF) exceeds a set amount. Specifically, the suppression control can be performed by adjusting the amount of RX gas supplied from the converter 12 to the furnace chamber and/or adjusting the _CO2 concentration in the RX gas generated by the converter 12.

Regarding the suppression control, for example, in soaking treatment, the amount of _CO2 generated in the furnace chamber due to the reduction of the target material may gradually decrease during the treatment. In such a case, the suppression control can suppress an increase in CP (PF) during soaking treatment due to the gradual decrease in the amount of _CO2 in the furnace chamber by gradually reducing the supply amount of RX gas within a range slightly lower than the steady value ( _V1 ).

In the soaking treatment, the supply amount of RX gas and the CO ₂ concentration in the RX gas are adjusted in conjunction with each other, so that the CO 2 concentration in the furnace chamber can be maintained at a steady value (m ₁ ) (see FIG. 3( b )).
At the start of the soaking treatment, the CP control means increases the CO ₂ concentration in the RX gas in response to the reduction in the supply amount of the RX gas.
Furthermore, during the soaking treatment, if the supply amount of RX gas is maintained at a steady value (V ₁ ), the CO ₂ concentration in the RX gas can be maintained within the range from the first steady value (d ₁₁ ) to the second steady value (d ₁₂ ) by suppression control (see Figure 3 (b)).

In essence, the amount of _CO2 in the furnace chamber during the soaking treatment gradually decreases, and in response to this, the CP control means can use suppression control to slowly increase the _CO2 concentration in the RX gas within the range from the first steady-state value ( _d11 ) to the second steady-state value ( _d12 ) in order to maintain the CP (PF) during the soaking treatment at the treatment value ( _C1 ).
Furthermore, when the _CO2 concentration in the RX gas is increased, the CP (PF) also fluctuates, so the CP control means uses suppression control to gradually reduce the supply amount of RX gas within a range slightly lower than the steady-state value ( _V1 ), thereby suppressing fluctuations in CP (PF) and maintaining the CP (PF) at the processing value ( _C1 ) during the soaking treatment.

In the slow cooling process of the heat treatment, the CP control means can adjust the supply amount of RX gas so as to increase from the steady value (V ₁ ) to the end value (V ₂ ) until the processing time has elapsed (see Figure 3(a)).
During the slow cooling process, the CP control means can increase the _CO2 concentration in the RX gas from the second steady-state value ( _d12 ) to the end value ( _d2 ) (see FIG. 3(b)).

In the slow cooling process, the CP control means decreases the CP(PF) over time, and this decrease in CP(PF) can be achieved mainly by increasing the _CO2 concentration in the RX gas.
Furthermore, in the slow cooling process, the furnace pressure is likely to change as the furnace temperature decreases, and such changes in furnace pressure can cause problems such as condensation in the piping. Therefore, in the slow cooling process, the supply amount of RX gas can be adjusted to increase in order to maintain the furnace pressure in the furnace chamber (furnace pressure control).

In addition, when the operation of lowering CP (PF) in the slow cooling process requires _CO2 exceeding the upper limit of the concentration in the RX gas, that is, when the increase in the _CO2 concentration in the RX gas alone is not sufficient, the operation of lowering CP (PF) can be performed by lowering the CO concentration in the furnace chamber ("CO concentration in furnace" in Figure 2).
The CO concentration in the furnace chamber can be reduced by supplying inert gas to the furnace chamber using the inert gas supply 17 .
That is, by supplying an inert gas to the furnace chamber using the inert gas supplier 17, the CO in the furnace chamber can be diluted, and the CO concentration can be reduced.
Manipulating the _CO2 concentration in the RX gas changes the dew point accordingly, and therefore, if the dew point becomes excessively high, problems such as condensation and clogging in the piping may easily occur. Manipulating the CO2 concentration in the furnace using an inert gas has the advantage of suppressing problems caused by manipulating the _CO2 concentration in the RX gas and substantially lowering the _CO2 concentration in the RX gas.

(9) Inert Gas Supply Device The atmospheric furnace 10 of the present invention may be provided with an inert gas supply device 17 for supplying an inert gas to the furnace chamber of the furnace body 11 (see FIG. 1).
The inert gas supply device 17 can be connected to the furnace body 11 via a second supply system 71 .
A second adjustment valve 72 can be connected to the second supply system 71 (see FIG. 1). An electric valve, a solenoid valve, or the like can be used as the second adjustment valve 72. When the second adjustment valve 72 is connected, the amount of inert gas supplied from the inert gas supply device 17 to the furnace body 11 can be adjusted by adjusting the opening of the second adjustment valve 72.

The inert gas is not particularly limited as long as it does not affect the material used in the object W during the heat treatment, that is, it is a gas that is inert to the material used in the object W.
Examples of inert gases include nitrogen (N ₂ ) gas and rare gases such as helium gas, neon gas, argon gas, krypton gas, xenon gas, and radon gas, and typically nitrogen (N ₂ ) gas can be used.

The inert gas supply unit 17 may include a tank, a cylinder, or the like for storing the inert gas in order to supply the inert gas to the furnace chamber, or may include, for example, a filter for collecting nitrogen (N ₂ ) from the air.
The second adjustment valve 72 can be electrically connected to the controller 16, and the controller 16 can operate the second adjustment valve 72 to adjust the amount of inert gas supplied from the inert gas supplier 17 to the furnace body 11.

The main purpose of supplying an inert gas to the furnace chamber is to purge the furnace chamber.
Purging the furnace chamber is a process of supplying and filling the furnace chamber with an inert gas to exhaust gases inside the furnace chamber, such as oxygen (O ₂ ), to the outside of the furnace.
That is, the inert gas supplier 17 supplies an inert gas to the furnace chamber to purge the furnace chamber, thereby making the atmosphere in the furnace chamber suitable for heat treatment.

Additionally, when the second adjusting valve 72 is electrically connected to the controller 16 , the controller 16 can control the purging of the furnace chamber using the inert gas supply 17 .
For example, the controller 16 can purge the furnace chamber at the start of the heat treatment included in the heat treatment, and create an atmosphere in the furnace chamber suitable for the heat treatment (see Figures 2, 3(a) and (b)).
Alternatively, the controller 16 can perform a purge of the furnace chamber at the end of the slow cooling process included in the heat treatment, and prepare for the next heat treatment by exhausting the gas inside the furnace chamber to the outside of the furnace (see Figures 2, 3(a) and (b)).

Other purposes for supplying an inert gas to the furnace chamber include the above-mentioned control of the CO concentration in the furnace and the furnace pressure control in the furnace chamber.
In the present invention, furnace pressure control can be performed by adjusting the supply amount of RX gas supplied from the converter 12 to the furnace chamber using the controller 16. However, adjusting the supply amount of RX gas may cause fluctuations in the CP (PF) of the atmosphere. Even in such a case, the furnace pressure can be adjusted and furnace pressure control can be performed by using the inert gas supplier 17 to supply an inert gas instead of RX gas to the furnace chamber while adjusting the supply amount.

(10) Cooler The atmosphere furnace 10 of the present invention may be equipped with a cooler 18.
The cooler 18 can be connected to the first supply system 21 between the furnace body 11 and the converter 12, and can cool the RX gas supplied to the furnace chamber.
In other words, if the dew point of the RX gas supplied to the furnace chamber becomes higher than the temperature outside the atmosphere furnace 10 (outside air temperature), a large amount of condensation will occur inside the piping, and the condensation will cause problems such as clogging the piping, damaging various devices, and entering the furnace chamber and causing abnormal reactions due to moisture.
The cooler 18 cools the RX gas supplied to the furnace chamber and lowers its dew point, thereby preventing the above-mentioned problems from occurring.
The cooler 18 is not particularly limited in configuration as long as it can cool the RX gas supplied to the furnace chamber, and for example, a refrigerator, a cold water cooler, etc. can be used.

[2] Atmosphere Control Method The atmosphere control method of the present invention is an atmosphere control method using a batch-type atmosphere furnace, in which an object placed in the furnace chamber is subjected to one cycle of heat treatment, including heating, soaking, and slow cooling, and the method comprises the steps of:
a temperature control step of controlling the temperature of the atmosphere in the furnace chamber so as to change the atmosphere to one suitable for each of the heating, soaking, and slow cooling treatments, and a CP control step of controlling the carbon potential of the atmosphere in coordination with the temperature control,
The temperature control step includes:
a step of comparing a furnace temperature of the furnace chamber with a preset temperature corresponding to each of the heating, soaking, and slow cooling treatments, and adjusting the furnace temperature by the temperature regulator so that the furnace temperature becomes the preset temperature;
The CP control step includes:
Calculating an actual measured value of the carbon potential of the atmosphere based on the CO concentration and _CO2 concentration obtained from the analyzer;
a step of calculating a variation in carbon potential by comparing a preset carbon potential value with the actual measured value in accordance with each of the heating, soaking, and slow cooling treatments;
and a step of adjusting the _CO2 concentration in the endothermic converted gas generated by the converting device based on the fluctuation amount so that the actual measured value becomes the set value.

In the atmosphere control method of the present invention, a batch-type atmosphere furnace is used.
The batch-type atmospheric furnace includes a furnace body having a furnace chamber, a temperature regulator that adjusts the furnace temperature in the furnace chamber, an analyzer that analyzes the CO concentration and _CO2 concentration in the furnace chamber, a converter that generates RX gas from air and hydrocarbon gas and supplies the RX gas to the furnace chamber, a supplier that supplies air and hydrocarbon gas to the converter, and a controller that controls the atmosphere in the furnace chamber.
Specifically, the batch-type atmosphere furnace can use the above-mentioned atmosphere furnace 10, which is equipped with a furnace body 11, a temperature regulator 14, an analyzer 15, a transformer 12, a supply device 13, and a controller 16 (see Figure 1).

The atmosphere control method is a method of performing three processes, namely, heating, soaking, and slow cooling, as one cycle of heat treatment on the object W housed in the furnace chamber of the furnace body 11. The atmosphere control method includes a temperature control step of controlling the temperature of the atmosphere and a CP control step of controlling the CP of the atmosphere so that the atmosphere in the furnace chamber is suitable for each process included in the heat treatment to perform the heat treatment on the object W.
In the atmosphere control method, the CP of the atmosphere to be controlled fluctuates in response to a change in the temperature of the atmosphere. Therefore, the atmosphere control method uses the actual measured value of CP that fluctuates in response to the temperature to control the CP of the atmosphere, and controls the temperature of the atmosphere and CP in coordination with each other.
Each step of the atmosphere control method will be described below.

(1) Temperature Control Step The temperature control step is a step of controlling the furnace temperature, which is the temperature of the atmosphere in the furnace chamber, in order to change the atmosphere in the furnace chamber to one suitable for each of the heating, soaking, and pre-cooling treatments.
The temperature control process includes a process of comparing the furnace temperature of the furnace chamber with a preset temperature according to each of the heating, soaking, and slow cooling processes, and adjusting the furnace temperature using a temperature regulator 14 so that the furnace temperature becomes the set temperature.
The temperature control step can be performed by using a temperature control means (program) provided in the controller 16 of the atmospheric furnace 10, and by the controller 16 operating the temperature regulator 14.

FIG. 4 is a flowchart showing a specific example of the temperature control process.
The temperature control process includes a heating process (denoted as "heating" in FIG. 4), a soaking process (denoted as "soaking" in FIG. 4), and a slow cooling process (denoted as "slow cooling" in FIG. 4).
The heat treatment process is a process in which the furnace temperature in the furnace chamber is increased to heat the object to a temperature suitable for soaking treatment. In this heat treatment process, the furnace temperature in the furnace chamber is increased from a starting temperature (T ₀ ) to a soaking temperature (T ₁ ) (see FIG. 2 ).

The heat treatment process includes the following steps:
Step S11: Start heating.
Step S12: Raising the temperature of the furnace chamber.
A step of analyzing the furnace temperature (S13).
A step of determining whether the furnace temperature has reached the set temperature (S14).
Step S15: Stopping the temperature increase.
Step S16: Ending the heating.

In step (S11), the controller 16 turns on the temperature regulator 14, and the heat treatment process is started.
In step (S12), the temperature regulator 14 raises the temperature of the furnace chamber.
In step (S13), the furnace temperature is analyzed by comparing the soaking temperature (T ₁ ), which is a preset temperature, with the actual measured value of the furnace temperature in the furnace chamber.

In step (S14), it is determined whether the furnace temperature has reached the set temperature based on the analysis result in step (S13). Specifically, in step (S14), the actually measured value of the furnace temperature can be used as the furnace temperature, and the soaking temperature (T ₁ ) can be used as the set temperature.
In step (S14), if it is determined that the furnace temperature (actual measured value) has not reached the set temperature (soaking temperature; _T1 ) (S14; no), steps (S12) and (S13) are repeated to continue raising the furnace temperature.
In step (S14), if it is determined that the furnace temperature (actual measured value) has reached the set temperature (soaking temperature; T ₁ ) (S14; yes), step (S15) is executed.
In step (S15), the temperature regulator 14 stops raising the temperature of the furnace chamber.
In step (S16), the heat treatment process is completed, and then the soaking process is started.

The soaking process is a process in which the furnace temperature of the furnace chamber is maintained at a constant value and the object is kept in a soaking atmosphere. In this soaking process, the furnace temperature of the furnace chamber is maintained at the soaking temperature (T ₁ ) until the treatment time has elapsed (see FIG. 2 ).
The processing time for the soaking treatment is determined in advance depending on the material of the object, etc.

The soaking process includes the following steps:
Step S21: Starting soaking.
A step of adjusting the temperature (S22).
A step of analyzing the furnace temperature (S23).
A step of determining whether the furnace temperature is maintained at the set temperature (S24).
A step of determining whether the processing time has elapsed (S25).
Step S16: Ending the soaking.

In step (S21), the soaking process is started.
In step (S22), the temperature of the atmosphere (furnace temperature) is adjusted by the temperature adjuster 14. Specifically, in step (S22), the temperature adjustment is performed by the controller 16 operating the temperature adjuster 14 to increase or decrease the furnace temperature (actual measured value).
In step (S23), the furnace temperature is analyzed by comparing a preset temperature (soaking temperature; T ₁ ) with the actual measured value of the furnace temperature in the furnace chamber.

In step (S24), it is determined based on the analysis results in step (S23) whether the furnace temperature is maintained at the set temperature (soaking temperature; T ₁ ).
In step (S24), if it is determined that the furnace temperature (actual measured value) is not maintained at the set temperature (soaking temperature; _T1 ) (S24; no), steps (S22) and (S23) are repeatedly executed, and the temperature adjustment of the furnace temperature is continuously performed.
In step (S24), if it is determined that the furnace temperature (actual measured value) is maintained at the set temperature (soaking temperature; T ₁ ) (S24; yes), step (S25) is executed.

In step (S25), it is determined whether a predetermined soaking treatment time has elapsed since the soaking treatment process was started (step (S21)). If it is determined in step (S25) that the treatment time has not elapsed (S25; no), steps (S22) to (S24) are repeatedly executed. If it is determined in step (S25) that the treatment time has elapsed (S25; yes), step (S26) is executed.
In step (S26), the soaking process is completed, and then the slow cooling process is started.

The slow cooling process is a process in which the furnace temperature of the furnace chamber is lowered at a constant rate to slowly cool the object. In this slow cooling process, the furnace temperature of the furnace chamber is lowered from the soaking temperature (T ₁ ) to the end temperature (T ₂ ) during the treatment time (see FIG. 2 ).
The processing time for the slow cooling process is determined in advance according to the temperature drop rate that is set depending on the material of the object, etc.

The slow cooling process includes the following steps.
A step of starting slow cooling (S31).
Step S32: Lowering the temperature of the furnace chamber.
A step of analyzing the furnace temperature (S33).
A step of determining whether the furnace temperature has reached the set temperature (S34).
Step S35: Stopping the temperature drop.
Step S36: Ending the slow cooling.

In step (S31), the slow cooling process is started.
In step (S32), the temperature of the furnace chamber is lowered by the temperature regulator 14. At this time, the rate at which the temperature of the furnace chamber is lowered by the temperature regulator 14 is determined in advance depending on the material of the object, etc.
In step (S33), the furnace temperature is analyzed by comparing the end temperature (T ₂ ), which is a preset temperature, with the actual measured value of the furnace temperature in the furnace chamber.

In step (S34), it is determined whether the furnace temperature has reached the set temperature based on the analysis result in step (S33).
In step (S34), if it is determined that the furnace temperature (actual measured value) has not reached the set temperature (end temperature; _T2 ) (S34; no), steps (S32) and (S33) are repeated, and the furnace temperature continues to be lowered.
In step (S34), if it is determined that the furnace temperature (actual measured value) has reached the set temperature (end temperature; T ₂ ) (S34; yes), step (S35) is executed.
In step (S35), the temperature regulator 14 stops lowering the temperature of the furnace chamber.
In step (S36), the controller 16 turns off the temperature regulator 14, and the slow cooling process is terminated, and with this termination, the temperature control process is terminated.

(2) CP Control Step The CP control step is a step of controlling the CP of the atmosphere in the furnace chamber in order to change the atmosphere in the furnace chamber to one suitable for each of the processes of heating, soaking, and pre-cooling.
The CP control process includes first to third steps.
The first step is a step of calculating the actual measured value of CP of the atmosphere based on the CO concentration and _CO2 concentration obtained from the analyzer 15. That is, in the first step, the actual measured value of CP is calculated based on the CO concentration and _CO2 concentration analyzed by the analyzer 15 as the CP that has changed in the temperature control step. The calculation of this actual measured value of CP can be performed by using a calculation means (program) provided in the controller 16 of the atmosphere furnace 10.

The second step is a step of calculating the amount of change in CP by comparing the actual measured value of CP with a preset value of CP according to each of the heating, soaking, and slow cooling processes. The calculation of the amount of change in CP can be performed, for example, by using a calculation function or the like provided in the controller 16 of the atmosphere furnace 10.
The third step is a step of adjusting the _CO2 concentration in the RX gas generated by the converter 12 based on the fluctuation amount obtained in the second step so that the measured value of CP becomes the set value of CP. The adjustment of the _CO2 concentration in the RX gas can be performed by the controller 16 of the atmosphere furnace 10 operating the converter 12, the supply device 13, etc. using a CP control means (program) provided in the controller 16.

FIG. 5 is a flowchart showing a specific example of the CP control process.
The CP control process includes a heating process (denoted as "heating" in FIG. 5), a soaking process (denoted as "soaking" in FIG. 4), and a slow cooling process (denoted as "slow cooling" in FIG. 4).
Furthermore, the CP control process can include a purging process at the start of the heating process and at the end of the slow cooling process. This purging process can be performed by supplying an inert gas to the furnace chamber of the furnace body 11 using the inert gas supply device 17 provided in the atmospheric furnace 10.

The heat treatment step is a step of increasing the CP in the furnace chamber atmosphere to a value suitable for soaking, in which the CP is increased from an initial value (C ₀ ) to a treatment value (C ₁ ) (see FIG. 2).
In the heat treatment step, the amount of RX gas supplied from the converter 12 is set to 100% (see FIG. 3(a)).
In the heat treatment step, the CO ₂ concentration in the RX gas is set to the minimum value (d ₀ ), and the CO concentration in the furnace is increased from the initial value (0%) to the treatment value (m ₁ ) (see FIG. 3( b )).

The heat treatment process includes the following steps:
A step of purging (S41).
Step S42: Start supplying RX gas.
Step S43: Set the supply amount of RX gas to 100%.
A step of adjusting the supply amount of hydrocarbon gas (S44).
A step of adjusting the amount of air supplied (S45).
A step of calculating and analyzing CP (S46).
A step of determining whether the CO ₂ concentration is at the minimum value (d ₀ ) (S47).
Step S48: Determine whether CP has increased from the initial value (C ₀ ).
A step (S49) of determining whether CP has reached the processing value (C ₁ ).

In step (S41), the controller 16 operates the inert gas supply device 17 to perform a purge process. This purge process is performed by supplying _N2 gas, an inert gas, to the furnace chamber at a maximum supply rate (100%) for a predetermined processing time (see FIG. 3(a)). After the predetermined processing time has elapsed, the purge process is terminated by reducing the supply rate of _{N2 gas} to 0% and stopping the supply of _N2 gas to the furnace chamber (see FIG. 3(a)).
In step (S42), after the purge process in step (S41), the supply of RX gas is started.
In step (S43), the amount of RX gas supplied to the furnace chamber at the start of supply is adjusted to the maximum value (100%) in order to fill the furnace chamber with RX gas in the shortest possible time.
In steps (S44) and (S45), the amounts of hydrocarbon gas and air supplied from the supply device 13 to the shift converter 12 are adjusted. By adjusting the amounts of hydrocarbon gas and air supplied, the _CO2 concentration in the RX gas at the start of supply is adjusted to the minimum value ( _d0 ). Here, the _CO2 concentration in the RX gas is set to the minimum value ( _d0 ) because, when the amount of RX gas supplied to the furnace chamber is the maximum value (100%), increasing the _CO2 concentration in the RX gas will decrease the CO2 concentration in the furnace chamber, and when the furnace chamber is completely filled with RX gas, the CP will not reach the treatment value ( _C1 ).

In step (S46), CP is calculated and analyzed. The calculation of CP corresponds to the first step described above and is executed using a calculation means (program) provided in the controller 16, and an actual measured value of CP is calculated. The analysis of CP corresponds to the second step described above and analyzes the amount of CP fluctuation by comparing the set value of CP with the actual measured value of CP.
In step (S47), it is determined whether the _CO2 concentration in the RX gas is at the minimum value ( _d0 ) based on the analysis result in step (S46). If it is determined in step (S47) that the _CO2 concentration is at the minimum value ( _d0 ) (S47; yes), step (S48) is executed.
In step (S48), it is determined whether the actual CP value has increased from the initial value (C ₀ ) based on the analysis result in step (S46). If it is determined in step (S48) that the actual CP value has increased from the initial value (C ₀ ) (S48; yes), step (S49) is executed.

In step (S49), it is determined whether the actual measured value of CP has reached the processing value (C ₁ ) based on the analysis result in step (S46).
In steps (S47) to (S49), if it is determined that the _CO2 concentration is not at the minimum value (d ₀ ) (S47; no), if it is determined that the actual measured value of CP has not increased from the initial value (C ₀ ) (S48; no), or if it is determined that the actual measured value of CP has not reached the processing value (C ₁ ) (S49; no), only the adjustment of the air supply amount in step (S45) or the adjustment of the hydrocarbon gas supply amount in steps (S45) and (S44) is repeatedly performed.
That is, steps (S47) to (S49) correspond to the third step described above, and the _CO2 concentration in the RX gas is adjusted so that the measured value of CP becomes the set value of CP.
Then, in step (S49), if it is determined that the measured value of CP has reached the treatment value (C ₁ ) (S49; yes), the heat treatment process is ended, and then the soaking process is started.

The soaking step is a step in which CP is maintained at a constant value until the treatment time has elapsed. During this soaking step, CP is maintained at a treatment value (C ₁ ) (see FIG. 2).
In the soaking process, the supply amount of RX gas from the converter 12 is reduced from the maximum value (100%) to a steady value (V ₁ ) (see FIG. 3( a )).
In addition, during the soaking process, the CO concentration in the furnace is maintained at the processing value (m ₁ ), and the CO ₂ concentration in the RX gas is first increased from the minimum value (d ₀ ) to the first steady-state value (d ₁₁ ), and then slowly increased within the range from the first steady-state value (d ₁₁ ) to the second steady-state value (d ₁₂ ) during the soaking process time (see FIG. 3( b )).

The soaking process includes the following steps:
Step of reducing the amount of RX gas supplied (S51).
A step of adjusting the supply amount of hydrocarbon gas (S52).
A step of adjusting the amount of air supplied (S53).
A step of calculating and analyzing CP (S54).
A step of determining whether the CO ₂ concentration has reached a first steady-state value (d ₁₁ ) (S55).
A step of determining whether CP is the processing value (C ₁ ) (S56).
Step (S57) of fine-tuning the _CO2 concentration.
A step of finely adjusting the RX gas supply amount (S58).
A step of determining whether the CO ₂ concentration is within a range from a first steady-state value (d ₁₁ ) to a second steady-state value (d ₁₂ ) (S59A).
A step of determining whether the processing time has elapsed (S59B).

In step (S51), the soaking process is started and the RX gas supply amount is reduced from the maximum value (100%) to a steady value (V ₁ ).
In steps (S52) and (S53), the amounts of hydrocarbon gas and air supplied from the supply device 13 to the shift converter 12 are adjusted. By adjusting the amounts of hydrocarbon gas and air supplied, the _CO2 concentration in the RX gas is adjusted to increase from the minimum value ( _d0 ) to the first steady-state value ( _d11 ).
In step (S54), CP is calculated and analyzed. The calculation of CP corresponds to the first step described above and is executed using a calculation means (program) provided in the controller 16, and an actual measured value of CP is calculated. The analysis of CP corresponds to the second step described above and analyzes the amount of CP fluctuation by comparing the set value of CP with the actual measured value of CP.

In step (S55), it is determined whether the _CO2 concentration in the RX gas has reached the first steady-state value ( _d11 ) based on the analysis result in step (S54). If it is determined in step (S55) that the _CO2 concentration has reached the first steady-state value ( _d11 ) (S55; yes), step (S56) is executed.
In step (S56), it is determined whether the actual CP value is maintained at the processing value (C ₁ ) based on the analysis result in step (S54). If it is determined in step (S56) that the actual CP value is maintained at the processing value (C ₁ ) (S56; yes), step (S57) is executed.

If it is determined in step (S55) that the _CO2 concentration has not reached the first steady-state value ( _d11 ) (S55; no), or if it is determined in step (S56) that the actual measured value of CP is not maintained at the processing value ( _C1 ) (S56; no), only the adjustment of the air supply amount in step (S53) is performed, or the adjustment of the hydrocarbon gas supply amount in steps (S53) and (S52) is repeated.
That is, steps (S55) and (S56) correspond to the third step described above, and the _CO2 concentration in the RX gas is adjusted so that the measured value of CP becomes the set value of CP.

In step (S57), the _CO2 concentration in the RX gas is finely adjusted within the range from the first steady-state value ( _d11 ) to the second steady-state value ( _d12 ). This fine adjustment is usually performed by only adjusting the amount of air supplied from the supplier 13 to the transformer 12.
In step (S58), the amount of RX gas supplied to the furnace chamber is finely adjusted.
Steps (S57) and (S58) are executed in response to a decrease in the amount of _CO2 in the furnace chamber during the soaking treatment. That is, during the soaking treatment, the amount of _CO2 in the furnace chamber decreases over time, and steps (S57) and (S58) are executed to compensate for this decrease and maintain CP at the treatment value ( _C1 ).

In step (S59A), it is determined whether the _CO2 concentration is within the range from the first steady-state value ( _d11 ) to the second steady-state value ( _d12 ). If it is determined in step (S59A) that the _CO2 concentration is within the range from the first steady-state value ( _d11 ) to the second steady-state value ( _d12 ) (S59A; yes), step (S59B) is executed.
In step (S59B), it is determined whether the processing time has elapsed.
If it is determined in step (S59A) that the _CO2 concentration is not within the range from the first steady-state value ( _d11 ) to the second steady-state value ( _d12 ) (S59A; no), or if it is determined in step (S59B) that the processing time has not elapsed (S59B; no), steps (S57) and (S58) are repeatedly executed.
Then, in step (S59B), if it is determined that the treatment time has elapsed (S59B; yes), the soaking treatment step is ended, and subsequently the slow cooling treatment step is started.

The slow cooling process is a process in which the CP is slowly lowered during the treatment time.
In this annealing step, CP is decreased from a processing value (C ₁ ) to a finishing value (C ₂ ) (see FIG. 2).
In the slow cooling process, the supply amount of RX gas from the converter 12 is increased from a steady value (V ₁ ) to a final value (V ₂ ) (see FIG. 3( a )).
In the slow cooling process, the _CO2 concentration in the RX gas is increased from the second steady value ( _d12 ) to the end value ( _d2 ), and the CO concentration in the furnace decreases from the process value ( _m1 ) (see FIG. 3(b)).

The slow cooling process includes the following steps.
Step of increasing the amount of RX gas supplied (S61).
A step of adjusting the supply amount of hydrocarbon gas (S62).
A step of adjusting the amount of air supplied (S63).
A step of calculating and analyzing CP (S64).
A step of determining whether the CO ₂ concentration has increased from the second steady-state value (d ₁₂ ) (S65).
A step of determining whether the CO ₂ concentration is at an end value (d ₂ ) (S66).
A step (S67A) of determining whether CP has decreased from the processing value (C ₁ ).
A step of determining whether CP is the end value (C ₂ ) (S67B).
Step S68: Stopping the supply of RX gas.
A step of purging (S69).

In step (S61), the RX gas supply amount is adjusted to increase from a steady value (V ₁ ) to an end value (V ₂ ) at the start of the slow cooling process. This increase in the RX gas supply amount is made in order to suppress changes in the furnace pressure in response to changes in the furnace temperature.
In steps (S62) and (S63), the amounts of hydrocarbon gas and air supplied from the supply device 13 to the shift converter 12 are adjusted. By adjusting the amounts of hydrocarbon gas and air supplied, the _CO2 concentration in the RX gas is adjusted to increase from the second steady-state value ( _d12 ) to the end value ( _d2 ).
In step (S64), CP is calculated and analyzed. The calculation of CP corresponds to the first step described above and is executed using a calculation means (program) provided in the controller 16, and an actual measured value of CP is calculated. The analysis of CP corresponds to the second step described above and analyzes the amount of CP fluctuation by comparing the set value of CP with the actual measured value of CP.

In step (S65), it is determined whether the _CO2 concentration in the RX gas has increased from the second steady-state value ( _d12 ) based on the analysis result in step (S64). If it is determined in step (S65) that the _CO2 concentration has increased from the second steady-state value ( _d12 ) (S65; yes), step (S66) is executed.
In step (S66), it is determined whether the _CO2 concentration in the RX gas is at the end value ( _d2 ) based on the analysis result in step (S64). In step (S66), if it is determined that the _CO2 concentration is at the end value ( _d2 ) (S66; yes), step (S67A) is executed.
If it is determined in step (S65) that the _CO2 concentration has not risen from the second steady-state value ( _d12 ) (S65; no), and if it is determined in step (S66) that the _CO2 concentration is not at the end value ( _d2 ) (S66; no), only the adjustment of the air supply amount in step (S63) or the adjustment of the hydrocarbon gas supply amount in steps (S63) and (S62) is repeatedly performed.

In step (S67A), it is determined whether the actual CP value has decreased from the processed value (C ₁ ) based on the analysis result in step (S64). If it is determined in step (S67A) that the actual CP value has decreased from the processed value (C ₁ ) (S67A; yes), step (S67B) is executed.
In step (S67B), it is determined whether the actual measurement value of CP is the end value (C ₂ ) based on the analysis result in step (S64). If it is determined in step (S67B) that the actual measurement value of CP is the end value (C ₂ ) (S67B; yes), step (S68) is executed.
If it is determined in step (S67A) that the actual measured value of CP has not decreased from the processing value (C ₁ ) (S67A; no), and if it is determined in step (S67B) that the actual measured value of CP is not the end value (C ₂ ) (S67B; no), only the adjustment of the air supply amount in step (S63) is performed, or the adjustment of the hydrocarbon gas supply amount in steps (S63) and (S62) is repeatedly performed.

In step (S68), the supply of RX gas to the furnace chamber is stopped.
In step (S69), the controller 16 operates the inert gas supplier 17 to perform the purge process.
The slow cooling process essentially ends at step (S68).
However, after the slow cooling process is completed, a purge process is carried out in step (S69) to prepare the atmosphere in the furnace chamber in preparation for the heat treatment of the next object, and the slow cooling process is completed. With this completion, the CP control process is also completed.
The purging process is performed by supplying _N2 gas, an inert gas, to the furnace chamber at a maximum supply rate (100%) for a predetermined processing time (see FIG. ₃ (a)). After the predetermined processing time has elapsed, the purging process is terminated by reducing the supply rate of _N2 gas to 0% and stopping the supply of _N2 gas to the furnace chamber (see FIG. 3(a)).

(3) Furnace Pressure Control Step In the above CP control step, the slow cooling step (S61) can be a furnace pressure control step of controlling the furnace pressure of the atmosphere in the furnace chamber.
The furnace pressure control process can be carried out by comparing the furnace pressure (actual value) obtained from the measuring instrument 19 with a set pressure that is preset according to the heat treatment, and adjusting the amount of RX gas supplied from the transformer 12 to the furnace chamber so that the furnace pressure (actual value) becomes the set pressure.
That is, in the slow cooling process, the furnace pressure is likely to change due to temperature changes, and the furnace pressure control step can suppress changes in the furnace pressure by adjusting the amount of RX gas supplied to the furnace chamber.
Furthermore, the furnace pressure control step can be performed not only in the slow cooling treatment but also in the heating treatment and soaking treatment in order to suppress changes in furnace pressure.

Furthermore, in the furnace pressure control process, the CO concentration in the furnace may change due to adjustment of the supply amount of RX gas, and the CP (actual measured value) may deviate from the set value.
In such a case, a step can be provided in which the _CO2 concentration in the RX gas generated by the converter 12 is adjusted by repeating step (S63) of the slow cooling treatment process described above, or by repeating steps (S62) and (S63), and the actual measured value of CP is set to the set value.

(4) Suppression Control Step In the CP control step, steps (S57) to (S59A) of the soaking treatment step can be a suppression control step for suppressing fluctuations in the CP (actual measured value) of the atmosphere during treatment.
That is, in the soaking treatment, the amount of CO ₂ in the furnace chamber decreases little by little as the treatment progresses, which may cause the CP (actual measured value) to fluctuate.
The suppression control process can suppress fluctuations in CP (actual measured value) by finely adjusting the _CO2 concentration in the RX gas in step (S57) and finely adjusting the amount of RX gas supplied to the furnace chamber in step (S58).

(5) Furnace CO concentration adjustment process The supply of inert gas ( _N2 gas) to the furnace chamber by the inert gas supply device can be used not only for the above-mentioned purging process, but also for the furnace CO concentration adjustment process to adjust the CO concentration in the furnace chamber.
That is, in the above-mentioned CP control step, when the CP (actual value) exceeds the set value due to adjustment of the _CO2 concentration in the RX gas and/or adjustment of the supply amount of RX gas, it is possible to respond by, for example, increasing the _CO2 concentration or decreasing the supply amount of RX gas, but such processing is cumbersome because it requires repeated operations such as readjustment of the _CO2 concentration and readjustment of the supply amount of RX gas, etc. Furthermore, the _CO2 concentration in the RX gas cannot be increased beyond the upper limit of the concentration in the RX gas, and the supply amount of RX gas cannot be decreased further than the amount necessary to maintain the furnace pressure.
Therefore, in such a case, as a process for adjusting the CO concentration inside the furnace, an inert gas ( _N2 gas) is supplied from the inert gas supply device 17 to the furnace chamber, and the CO concentration inside the furnace is reduced by diluting the CO in the furnace chamber, and then the _CO2 concentration in the RX gas is adjusted, thereby reducing the need for repetitive work and simplifying the process.

(6) Gas Cooling Process In the CP control process, in the slow cooling process step (S61), a gas cooling process can be performed to cool the RX gas supplied to the furnace chamber.
The gas cooling process can be performed using the cooler 18 provided in the atmospheric furnace 10 .
Since the RX gas has a high dew point, when it is supplied to the furnace chamber during the slow cooling process, it causes condensation and other problems. In such cases, as a gas cooling process, the RX gas supplied to the furnace chamber is cooled using the cooler 18 to lower the dew point, thereby preventing problems caused by condensation and other problems.

The present invention is particularly useful for application to batch furnaces, as it can coordinately control the temperature and carbon potential of the atmosphere and improve the efficiency of use of endothermic converted gas.

10: Atmosphere furnace,
11: Furnace body,
12; transformer; 21; first supply system; 22; first regulating valve;
13; supplier, 31; air supply system, 31A; air adjustment valve, 32; raw material supply system, 32A; raw material adjustment valve,
14; temperature regulator,
15; analyzer,
16: Controller,
17; inert gas supply device, 71; second supply system, 72; second adjusting valve,
18; Cooler;
19; Measuring instruments,
W: Object.

Claims (14)

A batch-type atmospheric furnace that performs heating, soaking, and slow cooling processes on an object as one cycle of heat treatment,
a furnace body having a furnace chamber for accommodating the object;
a conversion device connected to the furnace body, which generates an endothermic conversion gas from air and a hydrocarbon gas and supplies the endothermic conversion gas to the furnace chamber;
a supplier connected to the converter for supplying the air and the hydrocarbon gas to the converter;
a temperature regulator for adjusting the furnace temperature of the furnace chamber of the furnace body;
an analyzer for analyzing the CO concentration and _CO2 concentration in the furnace chamber of the furnace body;
a controller connected to the transformer and the temperature regulator to control the atmosphere in the furnace chamber;
The controller
a temperature control means for controlling the temperature of the atmosphere by adjusting the furnace temperature using the temperature regulator so that the furnace temperature of the furnace chamber becomes a preset temperature corresponding to each of the heating, soaking, and slow cooling treatments;
A calculation means for calculating an actual measured value of the carbon potential of the atmosphere based on the CO concentration and _CO2 concentration obtained from the analyzer;
The CP control means controls the carbon potential of the atmosphere by adjusting the CO 2 concentration in the endothermic converted _gas generated in the converting device so that the actual measured value of the carbon potential becomes a preset carbon potential setting value according to each of the heating, soaking, and slow cooling processes .
The CP control means adjusts the amount of air supplied from the supplier to the transformer in each of the heating, soaking, and slow cooling processes, thereby adjusting the CO _{2 concentration in the endothermic transformed gas generated in the transformer for each of the heating, soaking, and slow cooling processes. An atmosphere furnace characterized by adjusting the CO 2} concentration in the endothermic transformed gas generated in the transformer for each of the heating, soaking, and slow cooling processes . The controller adjusts the CO ₂ concentration in the endothermic converted gas by adjusting the amount of air supplied from the supplier to the converting device and the amount of hydrocarbon gas supplied in the CP control means. The atmosphere furnace according to claim 1. The controller adjusts only the amount of air supplied from the supplier to the transformer in the CP control means to adjust the CO ₂ concentration in the endothermic transformed gas. The atmosphere furnace according to claim 1. The atmospheric furnace of claim 1, further comprising an inert gas supply device connected to the furnace body to supply inert gas to the furnace chamber. The atmosphere furnace of claim 1, further comprising a cooler connected between the furnace body and the transformer device to cool the endothermic transformed gas supplied to the furnace chamber. 2. An atmosphere control method for performing a single cycle of heat treatment on an object placed in the furnace chamber, the method comprising: a batch-type atmosphere furnace according to claim 1, the batch-type atmosphere furnace comprising: a furnace body having a furnace chamber; a temperature regulator for adjusting the furnace temperature of the furnace chamber; an analyzer for analyzing _CO2 concentrations and CO2 concentrations in the furnace chamber; a converter for generating an endothermic converted gas from air and a hydrocarbon gas and supplying the endothermic converted gas to the furnace chamber; a supplyer for supplying the air and the hydrocarbon gas to the converter ; and a controller for controlling the atmosphere in the furnace chamber,
a temperature control step of controlling the temperature of the atmosphere in the furnace chamber so as to change the atmosphere into one suitable for each of the heating, soaking, and slow cooling treatments, and a CP control step of controlling the carbon potential of the atmosphere in coordination with the temperature control,
The temperature control step includes:
a step of comparing a furnace temperature of the furnace chamber with a preset temperature corresponding to each of the heating, soaking, and slow cooling treatments, and adjusting the furnace temperature by the temperature regulator so that the furnace temperature becomes the preset temperature;
The CP control step includes:
Calculating an actual measured value of the carbon potential of the atmosphere based on the CO concentration and _CO2 concentration obtained from the analyzer;
a step of calculating a variation in carbon potential by comparing a preset carbon potential value with the actual measured value in accordance with each of the heating, soaking, and slow cooling treatments;
and adjusting the CO ₂ concentration in the endothermic converted gas generated by the converting device for each of the heating, soaking, and slow cooling processes based on the fluctuation amount so that the actual measured value becomes the set value. An atmosphere control method for an atmosphere furnace, comprising: The CP control step adjusts the CO ₂ concentration in the endothermic converted gas by adjusting the amount of air supplied from the supply device to the converting device and the amount of hydrocarbon gas supplied. The atmosphere control method for an atmospheric furnace according to claim 6. The atmosphere control method for an atmosphere furnace according to claim 6, wherein the CP control step adjusts the CO ₂ concentration in the endothermic converted gas by adjusting only the amount of air supplied from the supply device to the converting device. As a step related to the heating treatment,
supplying an inert gas into the furnace chamber to purge the interior of the furnace before supplying the endothermic converted gas into the furnace chamber;
7. The atmosphere control method for an atmospheric furnace according to claim 6, further comprising the steps of: after the purging, adjusting the CO ₂ concentration in the endothermic converted gas generated by the converting device to a minimum value; adjusting the supply amount of the endothermic converted gas from the converting device to the furnace chamber to a maximum value; and starting the supply of the endothermic converted gas to the furnace chamber. The furnace body is provided with a measuring instrument for measuring the furnace pressure of the atmosphere in the furnace chamber,
a furnace pressure control step of controlling the furnace pressure of the atmosphere after the actual measurement value is set to the set value in the CP control step,
The furnace pressure control step includes:
7. The atmosphere control method for an atmosphere furnace according to claim 6, further comprising a step of comparing the furnace pressure obtained from the measuring instrument with a set pressure preset according to each of the heating, soaking and slow cooling processes, and adjusting the amount of endothermic converted gas supplied from the converting device to the furnace chamber so that the furnace pressure becomes the set pressure. The furnace pressure control step includes:
When the actual measured value of the carbon potential fluctuates from the set value due to the adjustment of the supply amount of the endothermic converted gas, the CO ₂ concentration in the endothermic converted gas generated by the converting device is adjusted to set the actual measured value of the carbon potential to the set value. The atmosphere control method for an atmospheric furnace according to claim 10, further comprising the step of: As a step related to the soaking treatment,
a suppression control step of suppressing fluctuations in the carbon potential of the atmosphere during the treatment;
The suppression control step includes:
7. The atmosphere control method for an atmosphere furnace according to claim 6, further comprising a step of adjusting the amount of endothermic converted gas supplied from the converting device to the furnace chamber when the amount of change in the carbon potential exceeds a preset amount according to the soaking process, and/or a step of adjusting the CO ₂ concentration in the endothermic converted gas generated by the converting device. an inert gas supply device for supplying an inert gas to the furnace chamber is connected to the furnace body;
The CO ₂ concentration in the endothermic converted gas generated by the converting device is adjusted, and/or the amount of endothermic converted gas supplied from the converting device to the furnace chamber is adjusted. When the actual measured value of the carbon potential exceeds the set value, an inert gas is supplied from the inert gas supplier to the furnace chamber to reduce the CO 2 concentration in the furnace chamber. The atmosphere control method for an atmospheric furnace according to claim 6, wherein the CO ₂ concentration in the endothermic converted gas generated by the converting device is adjusted. The atmosphere control method for an atmospheric furnace described in claim 6, wherein a cooler that cools the endothermic converted gas supplied from the converting device to the furnace chamber is connected to the furnace body, and the actual measured value of the carbon potential is varied.