TW202124731A - Surface hardening apparatus and surface hardening method - Google Patents

Abstract

The present invention is provided with: an in-furnace atmosphere gas concentration sensing device which senses the hydrogen concentration or the ammonia concentration in a treatment furnace; an in-furnace nitriding potential calculation device which calculates the nitriding potential within the treatment furnace on the basis of the hydrogen concentration or the ammonia concentration sensed by the in-furnace atmosphere gas concentration sensing device; and a gas introduction amount control device which changes the introduction amounts of a plurality of gases, excluding an ammonia decomposition gas, to be introduced into the furnace in accordance with the calculated nitriding potential within the treatment furnace and a desired nitriding potential, while maintaining the introduction amount of the ammonia decomposition gas constant, thereby bringing the nitriding potential within the treatment furnace closer to the desired nitriding potential.

Description

Surface hardening treatment device and surface hardening treatment method

The present invention relates to a surface hardening treatment device and a surface hardening treatment method for performing surface hardening treatment (for example, nitriding, nitrocarburizing, nitriding and quenching, etc.) of a metal to be treated.

In the surface hardening treatment of processed articles made of metals such as steel, nitriding treatment, which is a low-strain treatment, is often implemented. As the method of nitriding treatment, there are gas method, salt bath method, plasma method and so on.

Among these methods, the gas method is generally superior when considering the quality, environment, mass production, and the like. Carburizing or carburizing and nitriding treatment is accompanied by quenching of mechanical parts. The strain caused by such or high-frequency quenching can be improved by gas nitriding treatment (gas nitriding treatment). As the same type of treatment as the gas nitriding treatment, a gas nitrocarburizing treatment (gas nitrocarburizing treatment) accompanied by carburizing is further known.

The gas nitriding treatment is a process in which only the nitrogen is penetrated and diffused to the treated product to harden the surface. In the gas nitriding process, separate ammonia, a mixed gas of ammonia and nitrogen, ammonia and ammonia decomposition gas (consisting of 75% hydrogen and 25% nitrogen, also known as AX gas), or ammonia The mixed gas of, ammonia decomposition gas and nitrogen is introduced into the treatment furnace for surface hardening treatment.

On the other hand, gas nitrocarburizing is a process in which carbon is a minor component and nitrogen is diffused into the processed product to harden the surface. For example, in the gas nitrocarburizing process, _{the mixed gas of ammonia, nitrogen and carbon dioxide (CO 2} ), or the mixed gas of ammonia, nitrogen, carbon dioxide and carbon monoxide (CO), etc. The gas is introduced into the treatment furnace for surface hardening treatment.

Regarding the atmosphere control in gas nitriding treatment and gas soft nitriding treatment, the nitriding potential (K _N ) in the furnace is basically controlled. By controlling the nitriding potential (K _N ), various nitriding qualities can be obtained, such as controlling the volume of the _{γ'phase (Fe 4} N) and the ε phase (Fe _{2-3 N) in the compound layer formed on the steel surface} Rate, or realize processing that does not generate the compound layer, etc. For example, according to Japanese Patent Laid-Open No. 2016-211069 (Patent Document 1), the selection of the γ'phase and the thickening of the film can improve bending fatigue strength and wear resistance, and make mechanical parts more highly functional.

On the other hand, soft nitriding treatment has been used, for example, to actively and effectively utilize the hard ε phase to improve wear resistance (Non-Patent Document 1).

In the above-mentioned gas nitriding treatment and gas nitrocarburizing treatment, in order to manage the atmosphere in the treatment furnace in which the processed product is arranged, the gas concentration in the furnace atmosphere for measuring the hydrogen concentration in the furnace or the ammonia concentration in the furnace is installed Measuring sensor. Then, the nitriding potential in the furnace is calculated from the measured value of the furnace atmosphere gas concentration measurement sensor and compared with the target (set) nitriding potential to control the flow rate of each introduced gas (Non-Patent Document 2). Regarding the control method of each introduced gas, a well-known method is to control the total introduced amount while keeping the ratio of the flow rate of the introduced gas in the furnace constant (Non-Patent Document 3).

Patent Document 2 discloses a device capable of performing two kinds of controls (only one of them is selected at the same time), in which a control mode in which the flow rate ratio of the gas introduced into the furnace is kept fixed and the total introduced amount is controlled is the first control , The second control is a control mode that individually controls the amount of gas introduced in the furnace to change the flow rate of the gas introduced in the furnace (Patent Document 2). However, Patent Document 2 only discloses a specific example of the nitridation treatment in which the first control is effective (According to paragraphs 0096 and 0099 of Patent Document 2, "By maintaining NH ₃ (ammonia): N ₂ (nitrogen gas) )=80:20, control the total amount of ammonia and nitrogen introduced into the furnace", and control the nitriding potential 3, 3) with good accuracy, as to which nitriding treatment or soft nitrogen is required In the case of chemical treatment, if the second control is more effective, there is no disclosure, and there is no disclosure on the specific examples of the effective second control.

In addition, it is known that the method of controlling the total introduction amount while keeping the flow rate ratio of the introduced gas in the furnace constant has the advantage of being expected to control the total amount of gas used, but also has the disadvantage that the control range of the nitriding potential is small. As a countermeasure to solve this problem, the inventor of the present case developed a control method for achieving a wide range of nitriding potential control (for example, about 0.05 to 1.3 at 580°C) for low nitriding potential, and succeeded Applied for a related patent-Japanese Patent No. 6345320 (Patent Document 3). In the control method of Japanese Patent No. 6345320 (Patent Document 3), in order to keep the total introduction amount of the gases introduced into the furnace constant, while changing the flow rate ratio of the gases introduced into the furnace, Make the nitriding potential in the processing furnace close to the target nitriding potential, and individually control the amount of introduction of the plural kinds of gases in the furnace.

(Basic items of gas nitriding treatment) The basic items of gas nitriding treatment are explained from a chemical point of view. In gas nitriding treatment, the following formula ( 1) The nitridation reaction indicated. NH ₃ →[N]＋3/2H ₂ …(1)

At this time, the nitridation potential K _{N is} defined by the following formula (2). K _N =P _NH3 /P _H2 ^3/2 ... (2) Among them, P _NH3 is the partial pressure of ammonia in the furnace, and P _H2 is the partial pressure of hydrogen in the furnace. The nitriding potential K _N is well known as an index indicating the nitriding ability of the atmosphere in a gas nitriding furnace.

On the other hand, in the furnace in the gas nitriding process, a part of the ammonia introduced into the furnace is thermally decomposed into hydrogen and nitrogen according to the reaction shown in formula (3). NH ₃ →1/2N ₂ ＋3/2H ₂ …(3)

In the furnace, the reaction of formula (3) mainly occurs, and the nitridation reaction of formula (1) is almost negligible in quantity. Therefore, if the concentration of ammonia in the furnace consumed by the reaction of formula (3) or the concentration of hydrogen produced by the reaction of formula (3) is known, the nitriding potential can be calculated. That is, the hydrogen and nitrogen produced by 1 mole of ammonia are 1.5 mol and 0.5 mol, respectively. Therefore, as long as the ammonia concentration in the furnace is measured, the hydrogen concentration in the furnace can be known, and the nitriding potential can be calculated. Or, as long as the hydrogen concentration in the furnace is measured, the ammonia concentration in the furnace can be known, and the nitriding potential can also be calculated.

Furthermore, the ammonia gas flowing into the gas nitriding furnace is circulated in the furnace and then discharged out of the furnace. That is, in the gas nitriding process, for the existing gas in the furnace, fresh (new) ammonia gas is continuously flowed into the furnace, thereby continuously exhausting the existing gas to the outside of the furnace (by the supply pressure Its extrusion).

Here, if the flow rate of ammonia gas introduced into the furnace is small, the residence time of the gas in the furnace becomes longer. Therefore, the amount of ammonia gas that is decomposed increases, and the amount of nitrogen + hydrogen generated by the decomposition reaction Increase. On the other hand, if the flow rate of ammonia gas introduced into the furnace is large, the amount of ammonia gas discharged outside the furnace without being decomposed will increase, and the amount of nitrogen + hydrogen produced in the furnace will decrease.

(Basic items of flow control) Next, regarding the basic items of flow control, firstly, the case where the gas introduced into the furnace is only ammonia gas will be explained. When the decomposition degree of ammonia gas introduced into the furnace is set to s (0<s<1), the gas reaction in the furnace is represented by the following formula (4). NH ₃ →(1－s)/(1＋s)NH ₃ ＋0.5s/(1＋s)N ₂ ＋1.5s/(1＋s)H ₂ …(4) Among them, the left side is the gas introduced into the furnace (only ammonia gas), On the right is the gas composition in the furnace. The composition contains undecomposed ammonia and nitrogen and hydrogen produced in a ratio of 1:3 by the decomposition of ammonia. Therefore, when the hydrogen sensor is used to measure the hydrogen concentration in the furnace, the 1.5s/(1+s) on the right corresponds to the measured value measured by the hydrogen sensor, and the measured value can be calculated into the furnace. Decomposition degree of ammonia s. With this, the ammonia concentration in the furnace equivalent to (1-s)/(1+s) on the right can also be calculated. That is, the hydrogen concentration in the furnace and the ammonia concentration in the furnace can be obtained only from the measured value of the hydrogen sensor. Therefore, the nitriding potential can be calculated.

Even when a plurality of types of gases are introduced into the furnace, the nitriding potential K _N can be controlled. For example, two gases, ammonia and nitrogen, are used as the gas introduced into the furnace, and the introduction ratio is set to x: y (x and y are known conditions, and x + y = 1; for example, x = 0.5, y = 1-0.5 = The gas reaction in the furnace at 0.5 (NH ₃ :N ₂ =1:1)) is represented by the following formula (5). xNH ₃ ＋(1－x)N ₂ →x(1－s)/(1＋sx)NH ₃ ＋(0.5sx＋1－x)/(1＋sx)N ₂ ＋1.5sx/(1＋sx)H ₂ …(5)

Among them, the gas composition in the furnace on the right is undecomposed ammonia, nitrogen and hydrogen produced in a ratio of 1:3 by the decomposition of ammonia, and nitrogen introduced on the left (not decomposed in the furnace). At this time, x is a known condition (for example, x=0.5), so in the hydrogen concentration in the furnace on the right, which is 1.5sx/(1+sx), the only unknown is the decomposition degree of ammonia s. Therefore, as in the case of equation (4), the decomposition degree s of the ammonia gas introduced into the furnace can be calculated from the measured value of the hydrogen sensor, and thereby the ammonia concentration in the furnace can also be calculated. Therefore, the nitriding potential can be calculated.

When the flow rate ratio of the introduced gas in the furnace is not fixed, the hydrogen concentration in the furnace and the ammonia concentration in the furnace include two variables, the decomposition degree s of the ammonia introduced into the furnace, and the introduction ratio x of the ammonia gas. Generally, a mass flow controller (MFC) is used as a machine to control the gas flow. Therefore, based on its flow value, the ammonia introduction ratio x can be continuously read in the form of a digital signal. Therefore, based on the formula (5), by combining the introduction ratio x with the measured value of the hydrogen sensor, the nitriding potential can be calculated.

On the other hand, the basic matter of gas nitrocarburizing will be explained from a chemical point of view. In gas nitrocarburizing, the processing furnace (gas nitrocarburizing furnace) where the processed product is arranged will be generated by the following formula (6 ), the carbon supply reaction represented by the formula (7) (supplying carbon to the steel surface). 2CO→[C]＋CO ₂ …(6) CO＋H ₂ →[C]＋H ₂ O…(7)

It can be seen from equations (6) and (7) that the carbon supply source is carbon monoxide gas. Carbon monoxide gas can be directly introduced into the treatment furnace, or it can be generated from carbon dioxide in the treatment furnace. On the other hand, in the treatment furnace, the equilibrium reaction represented by the following formula (8) is established.

Furthermore, in the treatment furnace, the equilibrium reaction represented by the following formula (9) is established _{for H 2 O.}

According to the above, the amount of hydrogen consumed by the reactions of formulas (8) and (9) (set to molar ratio w) is related to the amount of oxygen in the treatment furnace. Therefore, it is better not to directly nest the measured value of the hydrogen sensor into the 1.5sx/(1+sx) in formula (5), but regard the measured value of the hydrogen sensor as equivalent to (1.5sx-w) /(1+sx), on this basis, calculate w based on the measured value of the oxygen sensor, and then calculate the decomposition degree of ammonia s.

The equilibrium constant of formula (9) is K=pH ₂ O/(pH ₂ · pO ₂ ^1.5 ), and pH ₂ O, pH ₂ , and pO ₂ are the partial pressures _{of H 2} O, H ₂ , and O _{2 in} the furnace, respectively. Therefore, the pH ₂ O value can be calculated from the known equilibrium constant K and the values of both the oxygen sensor and the hydrogen sensor (=pH ₂ , pO _{2) corresponding to the temperature conditions in the furnace.} Moreover, from equations (8) and (9), it can be seen that the amount of hydrogen consumed by these reactions, w, is equal to the value _{of pH 2 O.} Therefore, w can be obtained, so the decomposition degree of ammonia s can be obtained. [Prior Technical Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Laid-Open No. 2016-211069 [Patent Document 2] Japanese Patent No. 5629436 [Patent Document 3] Japanese Patent No. 6345320 [Non-Patent Literature]

[Non-Patent Document 1] "Nitriding and nitrocarburizing of iron", 2nd edition (2013), pages 81-86 (Dieter Liedtke et al., AGNE Gijutsu Center) [Non-Patent Document 2] "Heat Treatment", Vol. 55, No. 1, pages 7-11 (Hiraoka Tai, Watanabe Yoichi) [Non-Patent Document 3] "Nitriding and nitrocarburizing of iron", 2nd edition (2013), pages 158-163 (Dieter Liedtke et al., AGNE Gijutsu Center) [Non-Patent Document 4] "Effect of Compound Layer Thickness Composed of γ'-Fe4N on Rotated-Bending Fatigue Strength in Gas-Nitrided JIS-SCM435 Steel"、Materials Transactions、Vol.58、No.7(2017)、993～ 999 pages (Y. Hiraoka and A. Ishida) [Non-Patent Document 5] "Special Steel", Volume 61, No. 3, Pages 17-19 (Junzawa Kyun)

[The problem to be solved by the invention]

The inventor of the present case has repeatedly studied the situation of gas nitrocarburizing treatment in which a plurality of types of furnace introduction gases including ammonia and ammonia decomposition gas are introduced into the treatment furnace. As a result, they have found that the When the nitriding potential is close to the target nitriding potential, by keeping the amount of introduction of ammonia decomposition gas constant, while keeping the amount of introduction of the introduced gases in each furnace other than the above-mentioned ammonia decomposition gas among the above-mentioned plural kinds of introduced gases in the furnace The change can achieve practical nitridation potential control.

The present invention is the inventor based on the above knowledge. The object of the present invention is to provide a surface hardening treatment device and surface hardening treatment method, which is equivalent to introducing a plurality of types of gases including ammonia gas and ammonia decomposition gas into the gas nitrocarburizing treatment in the treatment furnace, which can realize Practical enough to control the nitriding potential. [Technical means to solve the problem]

The present invention is a surface hardening treatment device, which is characterized in that: Introduce a plurality of types of gas introduced into the furnace, including ammonia gas and ammonia decomposition gas, into the processing furnace, and perform gas nitrocarburizing treatment, which is used as the surface hardening treatment of the processed product arranged in the above-mentioned processing furnace, and is equipped with : Furnace atmosphere gas concentration detection device, which detects the hydrogen concentration or ammonia concentration in the above-mentioned processing furnace; furnace nitriding potential calculation device, which is calculated based on the hydrogen concentration or ammonia concentration detected by the furnace atmosphere gas concentration detection device The nitriding potential in the processing furnace; and a gas introduction amount control device that decomposes the ammonia gas based on the nitriding potential in the processing furnace and the target nitriding potential calculated by the furnace nitriding potential calculation device The amount of introduction is kept constant, while the introduction amount of the introduced gases in each furnace other than the ammonia decomposition gas among the plurality of kinds of introduced gases in the furnace is changed, thereby making the nitriding potential in the processing furnace close to the target nitriding Potential.

According to the present invention, it has been confirmed that by keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of each furnace introduction gas except ammonia decomposition gas among the plurality of furnace introduction gases, relatively comparison can be achieved. Wide range of nitriding potential control (especially relatively low nitriding potential control).

For the amount of ammonia decomposition gas introduced to maintain a fixed amount, it is hoped that a preliminary experiment can be performed before operation to determine in advance. The reason is that the degree of thermal decomposition of ammonia is actually affected by the furnace environment of the furnace used.

The surface hardening treatment device of the present invention is preferably further provided with an in-furnace oxygen concentration detection device that detects the oxygen concentration in the processing furnace, and the in-furnace nitriding potential calculation device is based on the detection by the furnace atmosphere gas concentration detection device The hydrogen concentration or ammonia concentration and the oxygen concentration detected by the oxygen concentration detection device in the furnace are used to calculate the nitriding potential in the processing furnace.

As mentioned above, in the soft nitriding treatment, hydrogen is consumed in the carbon supply reaction to become water (H ₂ O). The amount of water (H ₂ O) is in equilibrium with the amount of oxygen in the furnace. The oxygen concentration detection device in the furnace is used to detect the oxygen concentration in the furnace, and the oxygen concentration is used for the calculation of the nitriding potential, thereby achieving a more precise nitriding potential.

Furthermore, it is preferable that the above-mentioned gas introduction amount control device sets the introduction amount of ammonia gas into the furnace as A, the introduction amount of ammonia decomposition gas into the furnace as B, and when x is set to a specific constant, use is allocated to each The proportional coefficients c1,..., cN of the gas introduced into the furnace, the introduction amount of the gas introduced into the furnace except ammonia and ammonia decomposition gas among the above-mentioned multiple kinds of gases introduced into the furnace, C1,..., CN (N is more than 1 Integer) is controlled to satisfy the following formula: C1=c1×(A+x×B),..., CN=cN×(A+x×B).

According to actual experiments conducted by the inventor of the present case, it is known that when such control conditions are used, a relatively large range of nitriding potential control (especially a relatively low nitriding potential control) can be achieved.

The value of x is 0.5, for example. It can be understood as: the amount of hydrogen produced by thermal decomposition of 1 mol of ammonia gas in the furnace is 1.5 mol, and the amount of hydrogen supplied to the furnace by 1 mol of ammonia decomposition gas is 0.75 mol (3/4 mol) ), so the value of x is the ratio of 1.5:0.75=1:0.5. For the amount of hydrogen, the amount B of ammonia decomposition gas introduced into the furnace is converted into the coefficient of the amount A of ammonia introduced into the furnace.

However, the value of x does not have to be strictly 0.5, as long as it is in the range of approximately 0.4 to 0.6, a practical nitriding potential control can be achieved.

The above-mentioned plural kinds of gas introduced into the furnace include carbon dioxide as a carburizing gas. Or the above-mentioned plural kinds of gas introduced into the furnace include carbon monoxide gas as a carburizing gas.

Alternatively, the above-mentioned plural kinds of gas introduced into the furnace include carbon dioxide and nitrogen, or carbon monoxide gas and nitrogen.

In addition, the present invention can also be understood as a surface hardening treatment method. That is, the present invention is a surface hardening treatment method characterized by introducing a plurality of types of gas introduced into the furnace including ammonia gas and ammonia decomposition gas into the treatment furnace, and performing gas nitrocarburizing treatment as a configuration The surface hardening treatment of the processed article in the above-mentioned treatment furnace includes: a gas concentration detection step in the furnace atmosphere, which detects the hydrogen concentration or ammonia concentration in the above-mentioned treatment furnace; The hydrogen concentration or ammonia concentration detected in the furnace atmosphere gas concentration detection step calculates the nitriding potential in the processing furnace; and the gas introduction amount control step is based on the processing furnace calculated by the furnace nitriding potential calculation step The internal nitriding potential and target nitriding potential, while keeping the introduction amount of the ammonia decomposition gas constant, change the introduction amount of the introduced gases in each furnace except the ammonia decomposition gas among the above-mentioned plural kinds of furnace introduction gases. , Thereby making the nitriding potential in the processing furnace close to the target nitriding potential.

In addition, the present invention is a surface hardening treatment device characterized in that a plurality of furnace introduction gases including ammonia gas, ammonia decomposition gas, and carburizing gas (such as carbon dioxide or carbon monoxide gas) are introduced into the treatment furnace, Carry out gas nitrocarburizing treatment as the surface hardening treatment of the processed product arranged in the above-mentioned processing furnace, and equipped with: furnace atmosphere gas concentration detection device, which detects the hydrogen concentration or ammonia concentration in the above-mentioned processing furnace; An internal nitriding potential calculation device that calculates the nitriding potential in the processing furnace based on the hydrogen concentration or ammonia concentration detected by the furnace atmosphere gas concentration detection device; and a gas introduction amount control device, which is based on the nitrogen in the furnace The nitriding potential and target nitriding potential in the processing furnace calculated by the chemical potential calculation device keep the introduction amount of the ammonia decomposition gas constant while changing the introduction amount of the ammonia gas and the carburizing gas. Thereby, the nitriding potential in the processing furnace is close to the target nitriding potential.

It is characterized only in that the introduction amount of ammonia decomposition gas is kept fixed, while the introduction amount of ammonia gas and carburizing gas is changed; as for the introduction of other gases, the control of the introduction amount is ignored. Accordingly, it is possible to clearly include the introduction of a fixed amount of trace gas (approximately 1% or less according to the flow rate ratio) that does not substantially participate in the reaction within the scope of the right. For example, when the present invention is applied when two or more carburizing gases are introduced, even if only the introduction amount of the main carburizing gas is changed, and a fixed amount of another carburizing gas to be introduced in a small amount is introduced In the same way, a relatively large range of nitridation potential control (especially a relatively low nitridation potential control) can also be achieved.

In this case, it is preferable that the above-mentioned gas introduction amount control device sets the introduction amount of ammonia gas into the furnace as A, sets the introduction amount of ammonia decomposition gas in the furnace as B, and sets x as a specific constant. Given the proportional coefficient c1 of the carburizing gas, the introduction amount C1 of the carburizing gas is controlled to satisfy the following formula: C1=c1×(A+x×B).

In addition, the present invention is a surface hardening treatment device characterized by introducing a plurality of furnace introduction gases including ammonia gas, ammonia decomposition gas, carburizing gas, and nitrogen gas into the treatment furnace to perform gas nitrocarburizing Treatment, which is used as the surface hardening treatment of the processed article placed in the above-mentioned processing furnace, and equipped with: furnace atmosphere gas concentration detection device, which detects the hydrogen concentration or ammonia concentration in the above-mentioned processing furnace; furnace nitriding potential calculation A device for calculating the nitriding potential in the processing furnace based on the hydrogen concentration or ammonia concentration detected by the furnace atmosphere gas concentration detection device; and a gas introduction amount control device based on the calculation by the furnace nitriding potential calculation device The nitriding potential and target nitriding potential in the above-mentioned treatment furnace keep the introduction amount of the ammonia decomposition gas constant while changing the introduction amount of the ammonia gas, the carburizing gas, and the nitrogen gas. Make the nitriding potential in the processing furnace close to the target nitriding potential.

It is characterized only in that the introduction amount of ammonia decomposition gas is kept fixed, while the introduction amount of ammonia gas, carburizing gas, and nitrogen is changed; as for the control of the introduction amount of other gases, it does not matter. Accordingly, it is possible to clearly include the introduction of a fixed amount of trace gas (approximately 1% or less according to the flow rate ratio) that does not substantially participate in the reaction within the scope of the right. For example, when the present invention is applied when two or more carburizing gases are introduced, even if only the introduction amount of the main carburizing gas is changed, and a fixed amount of another carburizing gas to be introduced in a small amount is introduced In the same way, a relatively large range of nitridation potential control (especially a relatively low nitridation potential control) can also be achieved.

In this case, it is preferable that the above-mentioned gas introduction amount control device sets the introduction amount of ammonia gas into the furnace as A, sets the introduction amount of ammonia decomposition gas in the furnace as B, and sets x as a specific constant. The proportional coefficient c1 of the carburizing gas and the proportional coefficient c2 assigned to the nitrogen are controlled to satisfy the following formula: C1=c1×(A+x×B), C2=c2×(A+x×B). [Effects of Invention]

According to the present invention, it has been confirmed that by keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of each furnace introduction gas except ammonia decomposition gas among the plurality of furnace introduction gases, relatively comparison can be achieved. Wide range of nitriding potential control (especially relatively low nitriding potential control).

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

(constitute) Fig. 1 is a schematic diagram showing a surface hardening treatment apparatus according to an embodiment of the present invention. As shown in Fig. 1, the surface hardening treatment device 1 of this embodiment introduces ammonia, ammonia decomposition gas, and carbon dioxide into the treatment furnace 2 to perform gas nitrocarburizing treatment, which is used as the treatment being disposed in the treatment furnace 2. Surface hardening treatment device for surface hardening treatment of product S.

The ammonia decomposition gas system is also called AX gas, and contains a mixed gas of nitrogen and hydrogen in a ratio of 1:3. The to-be-processed article S is a metal product, for example, it is assumed that it is a steel part or a mold.

As shown in Fig. 1, the treatment furnace 2 of the surface hardening treatment device 1 of this embodiment is provided with a stirring fan 8, a stirring fan drive motor 9, a furnace temperature measuring device 10, a furnace heating device 11, and an atmosphere gas concentration detection device 3. The nitriding potential regulator 4, the temperature regulator 5, the programmable logic controller 31, the recorder 6, and the gas supply part 20 introduced into the furnace.

The stirring fan 8 is arranged in the processing furnace 2 and rotates in the processing furnace 2 to stir the gas in the processing furnace 2. The stirring fan drive motor 9 is connected with the stirring fan 8 to rotate the stirring fan 8 at an arbitrary rotation speed.

The furnace temperature measuring device 10 is provided with a thermocouple, and is configured to measure the temperature of the furnace gas existing in the processing furnace 2. Furthermore, after measuring the temperature of the gas in the furnace, the furnace temperature measuring device 10 outputs an information signal (furnace temperature signal) containing the measured temperature to the temperature regulator 5 and the recorder 6.

The atmosphere gas concentration detection device 3 includes a sensor that can detect the hydrogen concentration or ammonia concentration in the treatment furnace 2 as the atmosphere gas concentration in the furnace, and an oxygen sensor that can detect the oxygen concentration in the furnace as the oxygen concentration in the treatment furnace 2 Device. The detection body of each of the above two sensors communicates with the inside of the processing furnace 2 via the atmosphere gas pipe 12. In the present embodiment, the atmosphere gas piping 12 is formed by a single-line path that directly connects the sensor main body of the atmosphere gas concentration detection device 3 and the processing furnace 2. An on-off valve 17 is provided in the middle of the atmospheric gas pipe 12, and the on-off valve is controlled by the on-off valve control device 16.

In addition, after detecting the atmospheric gas concentration and oxygen concentration in the furnace, the atmospheric gas concentration detection device 3 outputs an information signal including the detected concentration to the nitriding potential regulator 4 and the recorder 6.

The recorder 6 includes a CPU (Central Processing Unit, central processing unit) or memory and other memory media, based on the output signal from the furnace temperature measuring device 10 or the atmosphere gas concentration detection device 3, the temperature in the processing furnace 2 or the furnace The atmospheric gas concentration and the oxygen concentration are memorized in correspondence with the date and time when the surface hardening process is performed, for example.

The nitriding potential regulator 4 has an in-furnace nitriding potential calculation device 13 and a gas flow rate output adjustment device 30. In addition, the programmable logic controller 31 has a gas introduction control device 14 and a parameter setting device 15.

The furnace nitriding potential calculation device 13 calculates the nitriding potential in the processing furnace 2 based on the hydrogen concentration or the ammonia concentration and the oxygen concentration detected by the furnace atmosphere gas concentration detection device 3. Specifically, according to the actual gas introduced into the furnace, the nitridation potential calculation formula based on the same idea as the formula (5) ~ formula (9) is introduced, and the value of the atmosphere gas concentration in the furnace and the oxygen concentration Value to calculate the nitriding potential.

In this embodiment, the introduction amount of ammonia gas into the furnace is set to A, the introduction amount of ammonia decomposition gas into the furnace is set to B, and x is set to a specific constant, the proportional coefficient assigned to the furnace introduction gas is used c1, control the introduction amount C1 of the gas introduced into the furnace, i.e. carbon dioxide, excluding ammonia and ammonia decomposition gas to satisfy the following formula: C1=c1×(A+x×B).

Furthermore, the parameter setting device 15 includes, for example, a touch panel, and can set input target nitriding potential, processing temperature, processing time, introduction amount of ammonia decomposition gas, specific constant x, proportional coefficient c1, etc., for the same processed article. In addition, it is also possible to set input PID (Proportion Integration Differentiation, proportional-integral-derivative) control setting parameter values for each different value of the target nitriding potential. Specifically, the "proportional gain", "integral gain or integral time" and "derivative gain or derivative time" of the input PID control can be set for each different value of the target nitriding potential. Each setting parameter value that has been set and input is transmitted to the gas flow output adjustment mechanism 30.

Furthermore, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the in-furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (the set nitriding potential) as the target The input values are the respective introduction amounts of ammonia and carbon dioxide in the three types of furnace introduction gases. More specifically, in the PID control, the introduction amount of ammonia decomposition gas is kept constant while the introduction amount of ammonia and carbon dioxide is changed, thereby bringing the nitriding potential in the treatment furnace 2 close to the target nitriding potential . In addition, in this PID control, each setting parameter value transmitted from the parameter setting device 15 is used.

Regarding the candidates of the setting parameter values used to implement the PID control of the setting input operation to the parameter setting device 15, it is preferable to perform pilot processing and obtain them in advance. In this embodiment, even if (1) the state of the processing furnace (the state of the furnace wall or fixture), (2) the temperature conditions of the processing furnace, and (3) the state (type and number) of the processed product are the same, it is still the same. (4) For each different value of the target nitriding potential, the candidate of the set parameter value can be obtained in advance through the automatic adjustment function of the nitriding potential regulator 4 itself. To construct a nitridation potential regulator 4 with automatic adjustment function, UT75A (high-function digital indicator regulator, manufactured by Yokogawa Electric Co., Ltd., http://www.yokogawa.co.jp/ns/cis) /utup/utadvanced/ns-ut75a-01-ja.htm) etc.

The set parameter values (combination of "proportional gain", "integral gain or integral time" and "derivative gain or derivative time") obtained as candidates will be recorded in some forms, and can be manually input to the target processing content Parameter setting device 15. However, the set parameter value obtained as a candidate can also be stored in some memory devices in a state associated with the target nitriding potential, and automatically read by the parameter setting device 15 based on the set input value of the target nitriding potential out.

Before PID control, the gas flow output adjustment mechanism 30 determines the initial value of the introduction amount of ammonia decomposition gas to be maintained fixed and the introduction amount of ammonia and carbon dioxide to be changed based on the value of the target nitriding potential. The candidates for these values are preferably obtained in advance by implementing pilot processing, and are automatically read by the parameter setting device 15 from a memory device or the like, or manually input from the parameter setting device 15. Thereafter, according to PID control, the nitriding potential in the treatment furnace 2 is approached to the target nitriding potential, and the amount of introduction of ammonia and carbon dioxide is determined by maintaining the above-mentioned relationship of C1=c1×(A+x×B) (Subject to change) (The amount of introduction of ammonia decomposition gas remains fixed). The output value of the gas flow output adjustment mechanism 30 is transmitted to the gas introduction amount control mechanism 14.

The gas introduction amount control mechanism 14 sends a control signal to the first supply amount control device 22 for ammonia gas.

The furnace-introduced gas supply unit 20 of the present embodiment includes a first furnace-introduced gas supply unit 21 for ammonia, a first supply amount control device 22, a first supply valve 23, and a first flow meter 24. In addition, the furnace-introduced gas supply unit 20 of this embodiment has a second furnace-introduced gas supply unit 25 for ammonia decomposition gas (AX gas), a second supply amount control device 26, a second supply valve 27, and a second Flowmeter 28. Furthermore, the furnace-introduced gas supply unit 20 of the present embodiment includes a third furnace-introduced gas supply unit 61 for carbon dioxide, a third supply amount control device 62, a third supply valve 63, and a third flow meter 64.

In this embodiment, ammonia gas, ammonia decomposition gas, and carbon dioxide are mixed in the furnace introduction gas introduction pipe 29 before being put into the processing furnace 2.

The first furnace introduction gas supply unit 21 is formed of, for example, a tank filled with the first furnace introduction gas (ammonia gas in this example).

The first supply amount control device 22 is formed of a mass flow controller (which can change the flow rate little by little in a short period of time), and is interposed between the first furnace introduction gas supply part 21 and the first supply valve 23. The opening degree of the first supply amount control device 22 is changed in accordance with the control signal output from the gas introduction amount control mechanism 14. In addition, the first supply amount control device 22 detects the supply amount from the gas supply unit 21 introduced into the first furnace to the first supply valve 23, and outputs an information signal including the detected supply amount to the gas introduction control mechanism 14 and Adjuster 6. The control signal can be used to modify the control of the gas introduction amount control mechanism 14 and so on.

The first supply valve 23 is formed of a solenoid valve that switches its open and closed states in accordance with a control signal output by the gas introduction amount control mechanism 14, and is interposed between the first supply amount control device 22 and the first flow meter 24.

The first flow meter 24 is formed of, for example, a mechanical flow meter such as a flow meter, and is interposed between the first supply valve 23 and the gas introduction pipe 29 in the furnace. In addition, the first flow meter 24 detects the supply amount of the gas introduction pipe 29 introduced into the furnace from the first supply valve 23. The supply amount detected by the first flow meter 24 can be used for the operator to visually confirm the operation.

The second furnace introduction gas supply part 25 is formed of, for example, a tank filled with a second furnace introduction gas (ammonia decomposition gas in this example).

The second supply amount control device 26 is formed of a mass flow controller (which can change the flow rate little by little in a short period of time), and is interposed between the second furnace introduction gas supply unit 25 and the second supply valve 27. The opening degree of the second supply amount control device 26 is changed in accordance with the control signal output from the gas introduction amount control mechanism 14. In addition, the second supply amount control device 26 detects the supply amount from the gas supply unit 25 introduced into the second furnace to the second supply valve 27, and outputs an information signal including the detected supply amount to the gas introduction control mechanism 14 and Adjuster 6. The control signal can be used to modify the control of the gas introduction amount control mechanism 14 and so on.

The second supply valve 27 is formed of a solenoid valve that switches its open and closed states in accordance with a control signal output by the gas introduction amount control mechanism 14, and is interposed between the second supply amount control device 26 and the second flow meter 28.

The second flow meter 28 is formed of, for example, a mechanical flow meter such as a flow meter, and is interposed between the second supply valve 27 and the furnace-introduced gas introduction pipe 29. In addition, the second flow meter 28 detects the supply amount of the gas introduction pipe 29 introduced into the furnace from the second supply valve 27. The supply amount detected by the second flow meter 28 can be used for the operator to visually confirm the operation.

However, in the present invention, the introduction amount of the ammonia decomposition gas is not changed little by little, so the second supply amount control device 26 may be omitted, and the flow rate (opening) of the second flow meter 28 may be manually adjusted. It is made to comply with the control signal output from the gas introduction amount control mechanism 14.

The third furnace introduction gas supply unit 61 is formed of, for example, a tank filled with a third furnace introduction gas (carbon dioxide in this example).

The third supply amount control device 62 is formed of a mass flow controller (which can change the flow rate little by little in a short period of time), and is interposed between the third furnace introduction gas supply unit 61 and the third supply valve 63. The opening degree of the third supply amount control device 62 is changed in accordance with the control signal output from the gas introduction amount control mechanism 14. In addition, the third supply amount control device 62 detects the supply amount from the gas supply unit 61 introduced into the third furnace to the third supply valve 63, and outputs an information signal including the detected supply amount to the gas introduction control mechanism 14 and Adjuster 6. The control signal can be used to modify the control of the gas introduction amount control mechanism 14 and so on.

The third supply valve 63 is formed of a solenoid valve that switches its open and closed states in accordance with a control signal output by the gas introduction amount control mechanism 14, and is interposed between the third supply amount control device 62 and the third flow meter 64.

The third flow meter 64 is formed of, for example, a mechanical flow meter such as a flow meter, and is interposed between the third supply valve 63 and the gas introduction pipe 29 in the furnace. In addition, the third flow meter 64 detects the supply amount of the gas introduction pipe 29 from the third supply valve 63 into the furnace. The supply amount detected by the third flow meter 64 can be used for the operator to visually confirm the operation.

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。(Function: Example 1) Next, referring to FIGS. 2 and 3, the function of the surface hardening treatment apparatus 1 of this embodiment will be described. First, the article S to be processed is put into the processing furnace 2 and the heating of the processing furnace 2 is started. In the example shown in Figure 2 and Figure 3, the size used is

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

In the heating of the processing furnace 2, the gas supply part 20 is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, and carbon dioxide into the processing furnace 2 at a set initial flow rate. Here, as shown in Figure 2, the set initial flow rate of ammonia is set to 13[l/min], the set initial flow rate of ammonia decomposition gas is set to 19[l/min], and the set initial flow rate of carbon dioxide is set to 1.03[l /min], and x = 0.5, c1 = 0.053. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state. The pretreatment of gas nitriding is usually performed, that is, the surface of the steel is activated to allow nitrogen to enter. In this case, hydrogen chloride gas or hydrogen cyanide gas will be generated in the furnace. These gases may degrade the atmosphere gas concentration detection device (sensor) 3 in the furnace, and closing the on-off valve 17 can effectively prevent this from happening.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the target nitriding potential (0.6 in this example: refer to Figure 3) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is judged that the temperature rise is completed, and it is judged that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (0.7 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia and carbon dioxide in the three types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: the nitriding potential in the treatment furnace 2 is approached by keeping the amount of introduction of ammonia decomposition gas constant while changing the amount of introduction of ammonia and carbon dioxide. Target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas and the introduction amount of carbon dioxide as a result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), and a third supply amount control device 62 for carbon dioxide.

Through the above control, as shown in Fig. 3, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. As a specific example, according to the example shown in Fig. 3, by feedback control with a sampling time of hundreds of milliseconds, the amount of ammonia introduced can be increased or decreased within a fluctuation range of about 3 ml (±1.5 ml), which can be started from the start of the treatment. At about 30 minutes later, the nitriding potential was controlled with extremely high accuracy to the target nitriding potential (0.6) (in the example shown in Figure 2, at about 190 minutes after the start of the treatment, the gas flow rate and nitriding were stopped. Record of momentum).

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。(Function: Example 1-2) Next, the case where the surface hardening treatment apparatus 1 of this embodiment is used and the target nitriding potential is set to 0.4 will be described as Example 1-2. In this embodiment 1-2, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

In the heating of the processing furnace 2, the gas supply part 20 is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, and carbon dioxide into the processing furnace 2 at a set initial flow rate. Here, the set initial flow rate of ammonia is set to 5.5[l/min], the set initial flow rate of ammonia decomposition gas is set to 25[l/min], the set initial flow rate of carbon dioxide is set to 0.95[l/min], and x = 0.5, c1 = 0.053. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (0.4 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed and the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (0.5 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia and carbon dioxide in the three types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: the nitriding potential in the treatment furnace 2 is approached by keeping the amount of introduction of ammonia decomposition gas constant while changing the amount of introduction of ammonia and carbon dioxide. Target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas and the introduction amount of carbon dioxide as a result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), and a third supply amount control device 62 for carbon dioxide.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a fluctuation range of about 3 ml (±1.5 ml), and the nitriding can be achieved about 30 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.4) with extremely high precision.

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。(Function: Example 1-3) Next, the case where the surface hardening treatment apparatus 1 of this embodiment is used and the target nitriding potential is set to 0.2 will be described as Example 1-3. In this embodiment 1-3, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

In the heating of the processing furnace 2, the gas supply part 20 is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, and carbon dioxide into the processing furnace 2 at a set initial flow rate. Here, as shown in Figure 4, the set initial flow rate of ammonia is set to 2[l/min], the set initial flow rate of ammonia decomposition gas is set to 29[l/min], and the set initial flow rate of carbon dioxide is set to 0.87[l /min], and x = 0.5, c1 = 0.053. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the target nitriding potential (0.2 in this example: refer to Figure 5) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed, and it is determined that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (in this example, 0.3), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia and carbon dioxide in the three types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: the nitriding potential in the treatment furnace 2 is approached by keeping the amount of introduction of ammonia decomposition gas constant while changing the amount of introduction of ammonia and carbon dioxide. Target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas and the introduction amount of carbon dioxide as a result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), and a third supply amount control device 62 for carbon dioxide.

Through the above control, as shown in FIG. 5, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. As a specific example, according to the example shown in Fig. 5, by feedback control with a sampling time of hundreds of milliseconds, the amount of ammonia introduced can be increased or decreased within a fluctuation range of about 3 ml (±1.5 ml), which can be started from the start of treatment. After about 30 minutes, the nitriding potential was controlled with extremely high accuracy to the target nitriding potential (0.2) (in the example shown in Figure 4, at about 160 minutes after the start of the treatment, the gas flow rate and nitriding were stopped. Record of momentum).

(Explanation of Comparative Example) For comparison, the nitriding potential control is performed in the following manner, that is, without introducing ammonia decomposition gas, the flow ratio of ammonia gas to carbon dioxide is always maintained at 95:5, so that the total flow rate of the same is changed.

Specifically, the in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , Regard the introduction of ammonia and carbon dioxide as input values. More specifically, in the PID control, the following control is implemented: while keeping the flow ratio of ammonia gas to carbon dioxide constant, the total introduction amount of ammonia gas and carbon dioxide is changed, so that the nitrogen in the treatment furnace 2 is changed. The chemical potential is close to the target nitriding potential.

However, in the control of the above comparative example, the nitriding potential cannot be controlled stably.

(Comparison between Example 1-1 to Example 1-3 and Comparative Example) A table summarizing the above results is shown as FIG. 6.

(Configuration of the second embodiment) As shown in FIG. 7, in the second embodiment, the third furnace-introduced gas supply part 61' is formed of a tank filled with carbon monoxide gas instead of carbon dioxide.

Furthermore, in the second embodiment, the introduction amount of ammonia gas into the furnace is set to A, the introduction amount of ammonia decomposition gas into the furnace is set to B, and x is set to a specific constant, use the introduced gas allocated to the furnace The proportional coefficient c1 controls the introduction amount C1 of carbon monoxide gas, which is the gas introduced into the furnace other than ammonia gas and ammonia decomposition gas, to satisfy the following formula: C1=c1×(A+x×B).

The other structure of this embodiment is substantially the same as that of the 1st embodiment demonstrated using FIG. In FIG. 7, the same reference numerals are given to the same parts as in the first embodiment. In addition, detailed descriptions of the parts of this embodiment that are the same as those of the first embodiment will be omitted.

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。(Function: Example 2-1) Next, the case where the surface hardening treatment apparatus of the second embodiment is used and the target nitriding potential is set to 0.6 will be described as Example 2-1. In this embodiment 2-1, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20 is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, and carbon monoxide gas into the processing furnace 2 at an initial flow rate. Here, the set initial flow rate of ammonia gas is set to 5.5 [l/min], the set initial flow rate of ammonia decomposition gas is set to 19 [l/min], and the set initial flow rate of carbon monoxide gas is set to 0.2 [l/min], and x=0.5, c1=0.01. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (0.6 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is judged that the temperature rise is completed, and it is judged that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (0.7 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia and carbon monoxide in the three types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: the nitriding potential in the treatment furnace 2 is changed by keeping the introduction amount of ammonia decomposition gas constant while changing the introduction amount of ammonia gas and carbon monoxide gas. Close to the target nitridation potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas and the introduction amount of carbon monoxide gas as a result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), and a third supply amount control device 62 for carbon monoxide gas.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced is increased or decreased within a fluctuation range of about 3 ml (±1.5 ml), and the nitrogen can be nitrogenized at about 20 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.6) with extremely high precision. (Function: Example 2-2)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the second embodiment is used and the target nitriding potential is set to 0.4 will be described as Example 2-2. In this embodiment 2-2, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20 is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, and carbon monoxide gas into the processing furnace 2 at an initial flow rate. Here, as shown in Figure 8, the set initial flow rate of ammonia gas is set to 3[l/min], the set initial flow rate of ammonia decomposition gas is set to 25[l/min], and the set initial flow rate of carbon monoxide gas is set to 0.15[ l/min], and x=0.5, c1=0.01. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (0.4 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed and the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (0.5 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia and carbon monoxide in the three types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: the nitriding potential in the treatment furnace 2 is changed by keeping the introduction amount of ammonia decomposition gas constant while changing the introduction amount of ammonia gas and carbon monoxide gas. Close to the target nitridation potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas and the introduction amount of carbon monoxide gas as a result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), and a third supply amount control device 62 for carbon monoxide gas.

By the above control, as shown in FIG. 9, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced is increased or decreased within a fluctuation range of about 3 ml (±1.5 ml), and the nitrogen can be nitrogenized at about 20 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.4) with extremely high precision. (Function: Example 2-3)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the second embodiment is used and the target nitriding potential is set to 0.2 will be described as Example 2-3. In this embodiment 2-3, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20 is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, and carbon monoxide gas into the processing furnace 2 at an initial flow rate. Here, the set initial flow rate of ammonia gas is set to 1 [l/min], the set initial flow rate of ammonia decomposition gas is set to 29 [l/min], and the set initial flow rate of carbon monoxide gas is set to 0.15 [l/min], and x=0.5, c1=0.01. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (0.3 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is judged that the temperature rise is completed, and it is judged that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (0.4 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia and carbon monoxide in the three types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: the nitriding potential in the treatment furnace 2 is changed by keeping the introduction amount of ammonia decomposition gas constant while changing the introduction amount of ammonia gas and carbon monoxide gas. Close to the target nitridation potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas and the introduction amount of carbon monoxide gas as a result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), and a third supply amount control device 62 for carbon monoxide gas.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a fluctuation range of about 3 ml (±1.5 ml), and the nitriding can be achieved about 30 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.2) with extremely high precision.

(Explanation of Comparative Example) For comparison, the nitridation potential control is performed in the following manner, that is, without introducing ammonia decomposition gas, the flow ratio of ammonia gas to carbon monoxide gas is always maintained at 99:1, so that the total flow rate of the gas is changed.

Specifically, the in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amount of ammonia gas and carbon monoxide gas is used as the input value. More specifically, in the PID control, the following control is implemented: the flow rate ratio of ammonia gas and carbon dioxide gas is kept constant, and the total introduction amount of ammonia gas and carbon monoxide gas is changed to make the processing furnace 2 The nitriding potential is close to the target nitriding potential.

However, in the control of the above comparative example, the nitriding potential cannot be controlled stably.

(Comparison between Example 2-1 to Example 2-3 and Comparative Example) A table summarizing the above results is shown as FIG. 10.

(Configuration of the third embodiment) As shown in FIG. 11, the furnace introduction gas supply part 20' of the third embodiment further has a fourth furnace introduction gas supply part 71 for nitrogen, a fourth supply amount control device 72, a fourth supply valve 73, and a second 4 Flowmeter 74.

The fourth furnace introduction gas supply unit 71 is formed of, for example, a tank filled with the fourth furnace introduction gas (nitrogen).

The fourth supply amount control device 72 is formed of a mass flow controller (which can change the flow rate little by little in a short period of time), and is interposed between the fourth furnace introduction gas supply unit 71 and the fourth supply valve 73. The opening degree of the fourth supply amount control device 72 is changed in accordance with the control signal output from the gas introduction amount control mechanism 14. In addition, the fourth supply amount control device 72 detects the supply amount from the gas supply unit 71 introduced into the fourth furnace to the fourth supply valve 73, and outputs an information signal including the detected supply amount to the gas introduction control mechanism 14 and Adjuster 6. The control signal can be used to modify the control of the gas introduction amount control mechanism 14 and so on.

The fourth supply valve 73 is formed of a solenoid valve that switches its open and closed states in accordance with a control signal output by the gas introduction amount control mechanism 14, and is interposed between the fourth supply amount control device 72 and the fourth flow meter 74.

The fourth flow meter 74 is formed of, for example, a mechanical flow meter such as a flow meter, and is interposed between the fourth supply valve 73 and the furnace-introduced gas introduction pipe 29. In addition, the fourth flow meter 74 detects the supply amount of the gas introduction pipe 29 from the fourth supply valve 73 into the furnace. The supply amount detected by the fourth flow meter 74 can be used for the operator to visually confirm the operation.

Furthermore, in the third embodiment, the introduction amount of ammonia gas into the furnace is set to A, the introduction amount of ammonia decomposition gas into the furnace is set to B, and x is set to a specific constant, the proportional coefficient assigned to each is used c1 and c2, control the introduction amount C1 of carbon dioxide and the introduction amount C2 of nitrogen gas into the furnace other than ammonia and ammonia decomposition gas to satisfy the following formula: C1=c1×(A＋x×B), C2=c2×(A+x×B).

The other structure of this embodiment is substantially the same as that of the 1st embodiment demonstrated using FIG. In FIG. 11, the same reference numerals are given to the same parts as in the first embodiment. In addition, detailed descriptions of the parts of this embodiment that are the same as those of the first embodiment will be omitted. (Function: Example 3-1)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the third embodiment is used and the target nitriding potential is set to 1.0 will be described as Example 3-1. In this embodiment 3-1, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the treatment furnace 2, a gas supply part 20' is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, carbon dioxide, and nitrogen into the treatment furnace 2 at a set initial flow rate. Here, the set initial flow rate of ammonia is set to 13[l/min], the set initial flow rate of ammonia decomposition gas is set to 19[l/min], the set initial flow rate of carbon dioxide is set to 2.2[l/min], and that of nitrogen Set the initial flow rate to 20 [l/min], and x=0.5, c1=0.1, and c2=0.9. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (1.0 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed, and it is determined that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (1.1 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon dioxide and nitrogen in the four kinds of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon dioxide, and nitrogen, the nitriding in the treatment furnace 2 The potential is close to the target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B) and C2=c2×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia, the introduction amount of carbon dioxide, and the introduction amount of nitrogen as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), the third supply amount control device 62 for carbon dioxide, and the fourth supply amount control device 72 for nitrogen.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced is increased or decreased within a fluctuation range of about 3 ml (±1.5 ml), and the nitrogen can be nitrogenized at about 20 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (1.0) with extremely high precision. (Function: Example 3-2)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the third embodiment is used and the target nitriding potential is set to 0.6 will be described as Example 3-2. In this embodiment 3-2, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the treatment furnace 2, a gas supply part 20' is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, carbon dioxide, and nitrogen into the treatment furnace 2 at a set initial flow rate. Here, as shown in Figure 12, the set initial flow rate of ammonia is set to 8[l/min], the set initial flow rate of ammonia decomposition gas is set to 25[l/min], and the set initial flow rate of carbon dioxide is set to 2[l /min], the set initial flow rate of nitrogen is 18.5 [l/min], and x=0.5, c1=0.1, c2=0.9. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (0.6 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is judged that the temperature rise is completed, and it is judged that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (0.7 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon dioxide and nitrogen in the four kinds of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon dioxide, and nitrogen, the nitriding in the treatment furnace 2 The potential is close to the target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B) and C2=c2×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia, the introduction amount of carbon dioxide, and the introduction amount of nitrogen as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), the third supply amount control device 62 for carbon dioxide, and the fourth supply amount control device 72 for nitrogen.

By the above control, as shown in FIG. 13, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a fluctuation range of about 3 ml (±1.5 ml), and the nitriding can be achieved about 30 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.6) with extremely high precision. (Function: Example 3-3)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the third embodiment is used and the target nitriding potential is set to 0.2 will be described as Example 3-3. In this embodiment 3-3, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the treatment furnace 2, a gas supply part 20' is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, carbon dioxide, and nitrogen into the treatment furnace 2 at a set initial flow rate. Here, the set initial flow rate of ammonia gas is set to 3[l/min], the set initial flow rate of ammonia decomposition gas is set to 29[l/min], the set initial flow rate of carbon dioxide is set to 1.8[l/min], and that of nitrogen Set the initial flow rate to 15.8 [l/min], and x=0.5, c1=0.1, and c2=0.9. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (0.2 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed, and it is determined that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (in this example, 0.3), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon dioxide and nitrogen in the four kinds of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon dioxide, and nitrogen, the nitriding in the treatment furnace 2 The potential is close to the target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B) and C2=c2×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia, the introduction amount of carbon dioxide, and the introduction amount of nitrogen as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), the third supply amount control device 62 for carbon dioxide, and the fourth supply amount control device 72 for nitrogen.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a range of about 3 ml (±1.5 ml), and the nitrogen can be nitridated at about 40 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.2) with extremely high precision.

(Explanation of Comparative Example) For comparison, the nitriding potential control is performed in the following manner, that is, without introducing ammonia decomposition gas, the flow ratio of ammonia, nitrogen, and carbon dioxide is always maintained at 50:45:5 to change the total flow rate.

Specifically, the in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, nitrogen, and carbon dioxide are used as input values. More specifically, in the PID control, the following control is implemented: while keeping the flow ratio of ammonia, nitrogen, and carbon dioxide constant, the total introduction amount of ammonia, nitrogen, and carbon dioxide is changed to make the treatment furnace The nitriding potential in 2 is close to the target nitriding potential.

However, in the control of the above comparative example, the nitriding potential cannot be controlled stably.

(Comparison between Example 3-1 to Example 3-3 and Comparative Example) A table summarizing the above results is shown as FIG. 14.

(Configuration of the fourth embodiment) As shown in FIG. 15, in the fourth embodiment, the third furnace-introduced gas supply part 61' is formed of a tank filled with carbon monoxide gas instead of carbon dioxide.

Furthermore, in the fourth embodiment, the introduction amount of ammonia gas into the furnace is set to A, the introduction amount of ammonia decomposition gas into the furnace is set to B, and x is set to a specific constant, the proportional coefficient assigned to each is used c1, c2, control the introduction amount C1 of carbon monoxide gas and the introduction amount C2 of nitrogen gas into the furnace other than ammonia and ammonia decomposition gas to satisfy the following equations: C1=c1×(A＋x×B), C2=c2×(A+x×B).

The other structure of this embodiment is substantially the same as that of the 1st embodiment demonstrated using FIG. In FIG. 15, the same reference numerals are given to the same parts as in the third embodiment. In addition, detailed descriptions of the parts of this embodiment that are the same as those of the third embodiment will be omitted. (Function: Example 4-1)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the fourth embodiment is used and the target nitriding potential is set to 1.0 will be described as Example 4-1. In this embodiment 4-1, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20' is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, carbon monoxide gas, and nitrogen into the processing furnace 2 at an initial flow rate. Here, the set initial flow rate of ammonia gas is set to 13[l/min], the set initial flow rate of ammonia decomposition gas is set to 19[l/min], the set initial flow rate of carbon monoxide gas is set to 0.9[l/min], nitrogen The initial flow rate is set to 20 [l/min], and x = 0.5, 1 = 0.04, and c2 = 0.96. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (1.0 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed, and it is determined that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (1.1 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon monoxide and nitrogen in the four types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon monoxide gas, and nitrogen, the nitrogen in the treatment furnace 2 The chemical potential is close to the target nitriding potential, and the relationship between C1=c1×(A+x×B) and C2=c2×(A+x×B) is maintained. In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas, the introduction amount of carbon monoxide gas, and the introduction amount of nitrogen as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), a third supply amount control device 62 for carbon monoxide gas, and a fourth supply amount control device 72 for nitrogen.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a fluctuation range of about 3 ml (±1.5 ml), and the nitriding can be achieved about 30 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (1.0) with extremely high precision. (Function: Example 4-2)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the fourth embodiment is used and the target nitriding potential is set to 0.6 will be described as Example 4-2. In this embodiment 4-2, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20' is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, carbon monoxide gas, and nitrogen into the processing furnace 2 at an initial flow rate. Here, as shown in Figure 12, the set initial flow rate of ammonia gas is set to 8[l/min], the set initial flow rate of ammonia decomposition gas is set to 25[l/min], and the set initial flow rate of carbon monoxide gas is set to 0.8[ l/min], the set initial flow rate of nitrogen is 19.7[l/min], and x=0.5, c1=0.04, c2=0.96. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (0.6 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is judged that the temperature rise is completed, and it is judged that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (0.7 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon monoxide and nitrogen in the four types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon monoxide gas, and nitrogen, the nitrogen in the treatment furnace 2 The chemical potential is close to the target nitriding potential, and the relationship between C1=c1×(A+x×B) and C2=c2×(A+x×B) is maintained. In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas, the introduction amount of carbon monoxide gas, and the introduction amount of nitrogen as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), a third supply amount control device 62 for carbon monoxide gas, and a fourth supply amount control device 72 for nitrogen.

By the above control, as shown in FIG. 13, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a range of about 3 ml (±1.5 ml), and the nitrogen can be nitridated at about 40 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.6) with extremely high precision. (Function: Example 4-3)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the fourth embodiment is used and the target nitriding potential is set to 0.2 will be described as Example 4-3. In this embodiment 4-3, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20' is introduced from the furnace to introduce ammonia gas, ammonia decomposition gas, carbon monoxide gas, and nitrogen into the processing furnace 2 at an initial flow rate. Here, the set initial flow rate of ammonia gas is set to 3[l/min], the set initial flow rate of ammonia decomposition gas is set to 29[l/min], the set initial flow rate of carbon monoxide gas is set to 0.7[l/min], and nitrogen The initial flow rate is set to 16 [l/min], and x = 0.5, c1 = 0.04, c2 = 0.96. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (0.2 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed, and it is determined that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (in this example, 0.3), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon monoxide and nitrogen in the four types of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon monoxide gas, and nitrogen, the nitrogen in the treatment furnace 2 The chemical potential is close to the target nitriding potential, and the relationship between C1=c1×(A+x×B) and C2=c2×(A+x×B) is maintained. In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas, the introduction amount of carbon monoxide gas, and the introduction amount of nitrogen as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), a third supply amount control device 62 for carbon monoxide gas, and a fourth supply amount control device 72 for nitrogen.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a range of about 3 ml (±1.5 ml), and the nitrogen can be nitridated at about 40 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.2) with extremely high precision.

(Explanation of Comparative Example) For comparison, the nitriding potential control is performed in the following manner, that is, without introducing ammonia decomposition gas, the flow ratio of ammonia, nitrogen, and carbon monoxide is always maintained at 50:48:2 to change the total flow rate.

Specifically, the in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, nitrogen, and carbon monoxide gas are used as input values. More specifically, in the PID control, the following control is implemented: the flow rate ratio of ammonia, nitrogen, and carbon monoxide gas is kept constant, and the total introduction amount of ammonia, nitrogen, and carbon monoxide gas is changed to make The nitriding potential in the treatment furnace 2 is close to the target nitriding potential.

However, in the control of the above comparative example, the nitriding potential cannot be controlled stably.

(Comparison between Example 4-1 to Example 4-3 and Comparative Example) A table summarizing the above results is shown as FIG. 16.

(Configuration of the fifth embodiment) As shown in Fig. 17, the furnace-introduction gas supply part 20" of the fifth embodiment has the furnace-introduction gas supply part 20' of the fourth embodiment and the fifth furnace-introduction gas supply part 81 for carbon dioxide. , The fifth supply amount control device 82, the fifth supply valve 83, and the fifth flow meter 84.

The 5th furnace introduction gas supply part 81 is formed by the tank filled with the 5th furnace introduction gas (carbon dioxide), for example.

The fifth supply amount control device 82 is formed of a mass flow controller (which can change the flow rate little by little in a short period of time), and is interposed between the fifth furnace introduction gas supply unit 81 and the fifth supply valve 83. The opening degree of the fifth supply amount control device 82 is changed in accordance with the control signal output from the gas introduction amount control mechanism 14. In addition, the fifth supply amount control device 82 detects the supply amount from the gas supply unit 81 introduced into the fifth furnace to the fifth supply valve 83, and outputs an information signal including the detected supply amount to the gas introduction control mechanism 14 and Adjuster 6. The control signal can be used to modify the control of the gas introduction amount control mechanism 14 and so on.

The fifth supply valve 83 is formed of a solenoid valve that switches its open and closed states in accordance with a control signal output by the gas introduction amount control mechanism 14, and is interposed between the fifth supply amount control device 82 and the fifth flow meter 84.

The fifth flow meter 84 is formed of, for example, a mechanical flow meter such as a flow meter, and is interposed between the fifth supply valve 83 and the furnace-introduced gas introduction pipe 29. In addition, the fifth flow meter 84 detects the supply amount of the gas introduction pipe 29 introduced into the furnace from the fifth supply valve 83. The supply amount detected by the fifth flow meter 84 can be used for the operator to visually confirm the operation.

Furthermore, in the fifth embodiment, the introduction amount of ammonia gas into the furnace is set to A, the introduction amount of ammonia decomposition gas into the furnace is set to B, and x is set to a specific constant, the proportional coefficient assigned to each is used c1, c2, c3, the introduction amount of carbon monoxide gas C1, the introduction amount of nitrogen C2, and the introduction amount of carbon dioxide C3, which are introduced into the furnace other than ammonia and ammonia decomposition gas, are controlled to satisfy the following equations: C1=c1×(A＋x×B), C2=c2×(A＋x×B), C3=c3×(A+x×B).

The other structure of this embodiment is substantially the same as that of the 4th embodiment demonstrated using FIG. 15. In FIG. 17, the same reference numerals are given to the same parts as in the fourth embodiment. In addition, detailed descriptions of the parts of this embodiment that are the same as those of the fourth embodiment will be omitted. (Function: Example 5-1)

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。Next, the case where the surface hardening treatment apparatus of the fifth embodiment is used and the target nitriding potential is set to 1.0 will be described as Example 5-1. In this embodiment 5-1, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20" is introduced from the furnace to set the initial flow rate to introduce ammonia, ammonia decomposition gas, carbon monoxide gas, nitrogen and carbon dioxide into the processing furnace 2. Here, the initial flow rate of ammonia is set Set to 13[l/min], the set initial flow rate of ammonia decomposition gas is 19[l/min], the set initial flow rate of carbon monoxide gas is set to 0.45[l/min], and the set initial flow rate of nitrogen is set to 21[l /min], the set initial flow rate of carbon dioxide is set to 0.9 [l/min], and x=0.5, c1=0.02, c2=0.94, c3=0.04. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (1.0 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed, and it is determined that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (1.1 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon monoxide, nitrogen, and carbon dioxide in the 5 kinds of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon monoxide gas, nitrogen, and carbon dioxide, the inside of the processing furnace 2 The nitriding potential is close to the target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B), C2=c2×(A+x×B) and C3=c3×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas, the introduction amount of carbon monoxide gas, the introduction amount of nitrogen, and the introduction amount of carbon dioxide as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), a third supply amount control device 62 for carbon monoxide gas, a fourth supply amount control device 72 for nitrogen, and a fifth supply amount control device 82 for carbon dioxide.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a fluctuation range of about 3 ml (±1.5 ml), and the nitriding can be achieved about 30 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (1.0) with extremely high precision.

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。(Function: Example 5-2) Next, the case where the surface hardening treatment apparatus of the fifth embodiment is used and the target nitriding potential is set to 0.6 will be described as Example 5-2. In this embodiment 5-2, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20" is introduced from the furnace to set the initial flow rate to introduce ammonia, ammonia decomposition gas, carbon monoxide gas, nitrogen and carbon dioxide into the processing furnace 2. Here, the initial flow rate of ammonia is set Set to 12[l/min], the set initial flow rate of ammonia decomposition gas is set to 25[l/min], the set initial flow rate of carbon monoxide gas is set to 0.5[l/min], and the set initial flow rate of nitrogen is set to 23[l /min], the set initial flow rate of carbon dioxide is set to 1.0 [l/min], and x=0.5, c1=0.02, c2=0.94, c3=0.04. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (1.0 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is judged that the temperature rise is completed, and it is judged that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (0.7 in this example), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon monoxide, nitrogen, and carbon dioxide in the 5 kinds of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon monoxide gas, nitrogen, and carbon dioxide, the inside of the processing furnace 2 The nitriding potential is close to the target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B), C2=c2×(A+x×B) and C3=c3×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas, the introduction amount of carbon monoxide gas, the introduction amount of nitrogen, and the introduction amount of carbon dioxide as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), a third supply amount control device 62 for carbon monoxide gas, a fourth supply amount control device 72 for nitrogen, and a fifth supply amount control device 82 for carbon dioxide.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced is increased or decreased within a range of about 3 ml (±1.5 ml), and the nitrogen can be nitrogenized at about 40 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.6) with extremely high precision.

700×1000之地坑爐作為處理爐2，將加熱溫度設為570℃，並使用具有4 m² 之表面積之鋼材作為被處理品S。(Function: Example 5-3) Next, the case where the surface hardening treatment apparatus of the fifth embodiment is used and the target nitriding potential is set to 0.2 will be described as Example 5-3. In this embodiment 5-3, the size is also used

The 700×1000 pit furnace was used as the treatment furnace 2, the heating temperature was set to 570°C, and a steel material with a surface area of ^{4 m 2 was used as the processed product S.}

During the heating of the processing furnace 2, the gas supply part 20" is introduced from the furnace to set the initial flow rate to introduce ammonia, ammonia decomposition gas, carbon monoxide gas, nitrogen and carbon dioxide into the processing furnace 2. Here, the initial flow rate of ammonia is set Set to 3[l/min], the set initial flow rate of ammonia decomposition gas is set to 29[l/min], the set initial flow rate of carbon monoxide gas is set to 0.3[l/min], and the set initial flow rate of nitrogen is set to 16[l /min], the set initial flow rate of carbon dioxide is set to 0.6 [l/min], and x=0.5, c1=0.02, c2=0.94, c3=0.04. These set initial flow rates can be set and input in the parameter setting device 15. In addition, the stirring fan driving motor 9 is driven to rotate the stirring fan 8 and the gas in the processing furnace 2 is stirred.

In the initial state, the on-off valve control device 16 turns the on-off valve 17 into a closed state.

In addition, the furnace temperature measuring device 10 measures the temperature of the gas in the furnace, and outputs an information signal including the measured temperature to the nitriding potential regulator 4 and the recorder 6. The nitriding potential regulator 4 judges whether the state in the processing furnace 2 is a state in which the temperature rise is in progress or the temperature rise has been completed (steady state).

In addition, the nitriding potential calculation device 13 in the furnace of the nitriding potential regulator 4 calculates the nitriding potential in the furnace (at first it is a very high value (because there is no hydrogen in the furnace), but as the ammonia gas is decomposed (hydrogen is generated) ) And decrease), and determine whether it is lower than the sum of the target nitriding potential (1.0 in this example) and the reference deviation value. The reference deviation value can also be set and input in the parameter setting device 15, for example, 0.1.

When it is determined that the temperature rise is completed, and it is determined that the calculated value of the nitriding potential in the furnace is lower than the sum of the target nitriding potential and the reference deviation value (in this example, 0.3), the nitriding potential regulator 4 passes through the gas introduction amount The control mechanism 14 starts to control the amount of gas introduced into the furnace. In response to this, the on-off control device 16 switches the on-off valve 17 to the open state.

When the on-off valve 17 is switched to the open state, the processing furnace 2 communicates with the atmosphere gas concentration detection device 3, and the furnace atmosphere gas concentration detection device 3 detects the hydrogen concentration in the furnace or the ammonia concentration in the furnace, and detects the oxygen concentration. The detected hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal are output to the nitriding potential regulator 4 and the recorder 6.

The in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, carbon monoxide, nitrogen, and carbon dioxide in the 5 kinds of furnace introduced gases are used as input values. Specifically, in the PID control, the following control is implemented: while keeping the introduction amount of ammonia decomposition gas constant, while changing the introduction amount of ammonia, carbon monoxide gas, nitrogen, and carbon dioxide, the inside of the processing furnace 2 The nitriding potential is close to the target nitriding potential, and maintain the above-mentioned relationship of C1=c1×(A+x×B), C2=c2×(A+x×B) and C3=c3×(A+x×B). In this PID control, each setting parameter value set and input by the parameter setting device 15 is used. The setting parameter value can be different according to the value of the target nitriding potential.

Then, the gas introduction amount control mechanism 14 controls the introduction amount of ammonia gas, the introduction amount of carbon monoxide gas, the introduction amount of nitrogen, and the introduction amount of carbon dioxide as the result of PID control. The gas introduction amount control mechanism 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas (fixed supply Amount), a third supply amount control device 62 for carbon monoxide gas, a fourth supply amount control device 72 for nitrogen, and a fifth supply amount control device 82 for carbon dioxide.

Through the above control, the nitriding potential in the furnace can be stably controlled near the target nitriding potential. Thereby, the surface hardening treatment of the processed article S can be performed with extremely high quality. Specifically, through feedback control with a sampling time of about hundreds of milliseconds, the amount of ammonia introduced will increase or decrease within a range of about 3 ml (±1.5 ml), and the nitrogen can be nitridated at about 40 minutes after the start of the treatment. The potential is controlled at the target nitriding potential (0.2) with extremely high precision.

(Explanation of Comparative Example) For comparison, the nitriding potential control is performed in the following manner, that is, without introducing ammonia decomposition gas, the flow ratio of ammonia, nitrogen, carbon monoxide gas and carbon dioxide is always maintained at 50:47:1:2, so that the total amount of the gas is maintained. The flow rate changes.

Specifically, the in-furnace nitriding potential calculation device 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential based on the input hydrogen concentration signal, ammonia concentration signal, and oxygen concentration signal. Then, the gas flow output adjustment mechanism 30 implements PID control. The PID control system uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, and the target nitriding potential (set nitriding potential) as the target value , The input amounts of ammonia, nitrogen, carbon monoxide and carbon dioxide are used as input values. More specifically, in the PID control, the following control is implemented: while maintaining a constant flow ratio of ammonia, nitrogen, carbon monoxide gas, and carbon dioxide, the total introduction amount of ammonia, nitrogen, carbon monoxide, and carbon dioxide is generated. Change to make the nitriding potential in the processing furnace 2 approach the target nitriding potential.

However, in the control of the above comparative example, the nitriding potential cannot be controlled stably.

(Comparison between Example 5-1 to Example 5-3 and Comparative Example) A table summarizing the above results is shown as FIG. 18.

1: Surface hardening treatment device 2: Treatment furnace 3: Atmosphere gas concentration detection device 4: Nitriding potential regulator 5: Temperature regulator 6: Logger 8: Stirring fan 9: Stirring fan drive motor 10: Furnace temperature measuring device 11: Furnace heating device 12: Atmosphere gas piping 13: Nitriding potential calculation device 14: Gas inlet control device 15: Parameter setting device (touch panel) 16: On-off valve control device 17: On-off valve 20: Furnace gas supply part 20': Furnace gas supply part 20": Introduce the gas supply part into the furnace 21: Introducing the gas supply part into the first furnace 22: The first furnace gas supply control device 23: 1st supply valve 24: The first flow meter 25: Introducing the gas supply part into the second furnace 26: The second supply control device 27: 2nd supply valve 28: The second flow meter 29: Gas introduction piping into the furnace 30: Gas flow output adjustment device 31: Programmable logic controller 40: Gas waste piping in the furnace 41: Exhaust combustion decomposition device 61: Introducing the gas supply part in the third furnace 61': Gas supply part introduced into the third furnace 62: 3rd furnace gas supply control device 63: 3rd supply valve 64: 3rd flow meter 71: Introducing the gas supply part in the fourth furnace 72: The fourth furnace gas supply control device 73: 4th supply valve 74: 4th flow meter 81: Gas supply part introduced into the fifth furnace 82: 5th furnace gas supply control device 83: 5th supply valve 84: 5th flow meter S: Product to be processed

Fig. 1 is a schematic diagram showing a surface hardening treatment apparatus according to the first embodiment of the present invention. Fig. 2 is a graph showing the control of gas introduction in the furnace of Example 1-1. Fig. 3 is a graph showing the nitriding potential control of Example 1-1. Fig. 4 is a graph showing the control of gas introduction in the furnace of Examples 1-3. Fig. 5 is a graph showing the nitriding potential control of Examples 1-3. Fig. 6 is a table comparing Example 1-1 to Example 1-3 with each comparative example. Fig. 7 is a schematic diagram showing a surface hardening treatment apparatus according to a second embodiment of the present invention. Fig. 8 is a graph showing the control of introducing gas into the furnace of Example 2-2. Fig. 9 is a graph showing the nitriding potential control of Example 2-2. Fig. 10 is a table comparing Examples 2-1 to 2-3 and each comparative example. Fig. 11 is a schematic diagram showing a surface hardening treatment apparatus according to a third embodiment of the present invention. Fig. 12 is a graph showing the control of introducing gas into the furnace of Example 3-2. Fig. 13 is a graph showing the nitriding potential control of Example 3-2. Fig. 14 is a table comparing Examples 3-1 to 3-3 with each comparative example. Fig. 15 is a schematic diagram showing a surface hardening treatment apparatus according to a fourth embodiment of the present invention. Fig. 16 is a table comparing Examples 4-1 to 4-3 with each comparative example. Fig. 17 is a schematic diagram showing a surface hardening treatment apparatus according to a fifth embodiment of the present invention. Fig. 18 is a table comparing Examples 5-1 to 5-3 with each comparative example.

Claims (14)

A surface hardening treatment device, characterized in that: Introduce a plurality of types of gas introduced into the furnace, including ammonia gas and ammonia decomposition gas, into the processing furnace, and perform gas nitrocarburizing treatment, which is used as the surface hardening treatment of the processed product arranged in the above-mentioned processing furnace, and is equipped with : Furnace atmosphere gas concentration detection device, which detects the hydrogen concentration or ammonia concentration in the above-mentioned treatment furnace; A furnace nitriding potential calculation device, which calculates the nitriding potential in the processing furnace based on the hydrogen concentration or ammonia concentration detected by the furnace atmosphere gas concentration detection device; and A gas introduction amount control device which keeps the introduction amount of the ammonia decomposition gas constant based on the nitridation potential in the processing furnace calculated by the nitridation potential calculation device in the furnace and the target nitridation potential, while maintaining the plural number The introduction amount of the introduced gas in each furnace other than the ammonia decomposition gas among the introduced gas in the seed furnace is changed, thereby bringing the nitriding potential in the processing furnace close to the target nitriding potential. Such as the surface hardening treatment device of claim 1, which Further equipped with a furnace oxygen concentration detection device for detecting the oxygen concentration in the above-mentioned processing furnace, and The nitriding potential calculation device in the furnace calculates the nitriding potential in the processing furnace based on the hydrogen concentration or ammonia concentration detected by the furnace atmosphere gas concentration detection device and the oxygen concentration detected by the oxygen concentration detection device in the furnace . Such as the surface hardening treatment device of claim 1 or 2, where When the above-mentioned gas introduction amount control device sets the introduction amount of ammonia gas into the furnace as A, sets the introduction amount of ammonia decomposition gas into the furnace as B, and sets x as a specific constant, use the gas that is allocated to each furnace introduction gas Proportional coefficients c1,..., cN, control the amount of introduction C1,..., CN (N is an integer greater than 1) of the above-mentioned plural kinds of gases introduced into the furnace except for ammonia and ammonia decomposition gas into the introduced gases in the furnace to satisfy The following formula: C1=c1×(A+x×B),..., CN=cN×(A+x×B). Such as the surface hardening device of claim 3, where The above-mentioned specific constant x is 0.4 to 0.6. Such as the surface hardening device of claim 4, where The above-mentioned specific constant x is 0.5. Such as the surface hardening device of any one of claims 1 to 5, wherein The above-mentioned plural kinds of gas introduced into the furnace include carbon dioxide. Such as the surface hardening device of any one of claims 1 to 5, wherein The above-mentioned plural kinds of gases introduced into the furnace include carbon monoxide gas. Such as the surface hardening device of any one of claims 1 to 5, wherein The plurality of types of gases introduced into the furnace include carbon dioxide and nitrogen. Such as the surface hardening device of any one of claims 1 to 5, wherein The above-mentioned plural kinds of gas introduced into the furnace include carbon monoxide gas and nitrogen gas. A surface hardening treatment method, which is characterized in: Introduce a plurality of types of gas introduced into the furnace, including ammonia gas and ammonia decomposition gas, into the processing furnace, and perform gas nitrocarburizing treatment, which is used as the surface hardening treatment of the processed product arranged in the above-mentioned processing furnace, and includes : A step of detecting the concentration of atmosphere gas in the furnace, which detects the concentration of hydrogen or ammonia in the above-mentioned treatment furnace; A step of calculating the nitriding potential in the furnace, which calculates the nitriding potential in the processing furnace based on the hydrogen concentration or the ammonia concentration detected by the furnace atmosphere gas concentration detection device; and The gas introduction amount control step is to keep the introduction amount of the ammonia decomposition gas constant based on the nitriding potential in the processing furnace and the target nitriding potential calculated by the nitriding potential calculation device in the furnace, and to make the plural numbers The introduction amount of the introduced gas in each furnace other than the ammonia decomposition gas in the introduced gas in the seed furnace is changed, thereby making the nitriding potential in the processing furnace close to the target nitriding potential. A surface hardening treatment device, characterized in that: Introduce a plurality of types of gas introduced into the furnace including ammonia gas, ammonia decomposition gas and carburizing gas into the treatment furnace, and perform gas nitrocarburizing treatment as the surface hardening treatment of the treated product arranged in the above treatment furnace , And have: Furnace atmosphere gas concentration detection device, which detects the hydrogen concentration or ammonia concentration in the above-mentioned treatment furnace; A furnace nitriding potential calculation device, which calculates the nitriding potential in the processing furnace based on the hydrogen concentration or ammonia concentration detected by the furnace atmosphere gas concentration detection device; and A gas introduction amount control device which, based on the nitriding potential and target nitriding potential in the processing furnace calculated by the nitriding potential calculation device in the furnace, keeps the introduction amount of the ammonia decomposition gas constant, while keeping the ammonia The introduction amount of gas and the carburizing gas is changed, thereby making the nitriding potential in the processing furnace close to the target nitriding potential. Such as the surface hardening treatment device of claim 11, where The above-mentioned gas introduction amount control device uses the ratio assigned to the carburizing gas when the introduction amount of ammonia gas in the furnace is set to A, the introduction amount of ammonia decomposition gas into the furnace is set to B, and x is set to a specific constant. The coefficient c1 controls the introduction amount C1 of the above-mentioned carburizing gas to satisfy the following formula: C1=c1×(A+x×B). A surface hardening treatment device, characterized in that: Introduce multiple types of furnace gases including ammonia, ammonia decomposition gas, carburizing gas, and nitrogen into the processing furnace, and perform gas nitrocarburizing treatment, which is used as surface hardening of the processed product placed in the above-mentioned processing furnace Deal with, and have: Furnace atmosphere gas concentration detection device, which detects the hydrogen concentration or ammonia concentration in the above-mentioned treatment furnace; A furnace nitriding potential calculation device, which calculates the nitriding potential in the processing furnace based on the hydrogen concentration or ammonia concentration detected by the furnace atmosphere gas concentration detection device; and A gas introduction amount control device which, based on the nitriding potential and target nitriding potential in the processing furnace calculated by the nitriding potential calculation device in the furnace, keeps the introduction amount of the ammonia decomposition gas constant, while keeping the ammonia The introduction amount of gas, the carburizing gas, and the nitrogen gas is changed, thereby making the nitriding potential in the processing furnace close to the target nitriding potential. Such as the surface hardening treatment device of claim 13, where The above-mentioned gas introduction amount control device uses the ratio assigned to the carburizing gas when the introduction amount of ammonia gas in the furnace is set to A, the introduction amount of ammonia decomposition gas into the furnace is set to B, and x is set to a specific constant. The coefficient c1 and the proportional coefficient c2 assigned to the nitrogen gas control the introduction amount C1 of the carburizing gas and the introduction amount C2 of the nitrogen gas to satisfy the following formula: C1=c1×(A+x×B), C2=c2×(A+x×B).

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