KR102243284B1 - Nitriding Apparatus and Nitriding Treatment Method - Google Patents

Abstract

According to an embodiment of the present invention, a nitriding treatment apparatus is provided. According to an embodiment of the present invention, the nitridation treatment apparatus includes a reaction chamber having a processing space formed therein so as to perform a nitriding treatment of a metal, and a treatment of supplying a processing gas including ammonia gas to the reaction chamber. A gas supply unit, a discharge unit for discharging the processed gas decomposed or undecomposed in the reaction chamber, a sensor unit for detecting a partial pressure of hydrogen inside the reaction chamber, and a partial pressure of hydrogen received from the sensor unit to an inside of the reaction chamber And a controller configured to calculate a nitridation potential value of and control the internal temperature of the reaction chamber and a flow rate of the processing gas supplied to the reaction chamber in connection with the nitridation potential value.

Description

Nitriding Apparatus and Nitriding Treatment Method {Nitriding Apparatus and Nitriding Treatment Method}

The present invention relates to a nitriding treatment device and a nitriding treatment method, and to a nitriding treatment device and a nitriding treatment method capable of forming a high-concentration nitride layer by adsorbing and diffusing nitrogen, which is a hardening element, on the surface of a metal product.

In the surface hardening method of iron, a thermochemical surface hardening method that changes the chemical composition of the iron surface by diffusing and penetrating necessary components in the reaction gas by applying heat to the iron surface, and a physical surface that is hardened only by quenching without changing the chemical composition of the iron surface. There is a hardening method. In general, thermochemical surface hardening methods include carburization, nitriding, carburizing, and chimney, and physical surface hardening methods include induction heating quenching, flame quenching, and the like.

Among them, the nitriding method, which is a kind of thermochemical surface hardening method, penetrates and diffuses nitrogen atoms into the surface of iron. Compared to other surface treatment methods such as carburization, there is little change in size or shape, and it can be produced precisely. There is this. In the nitriding method, a product made of steel is mounted inside a reaction chamber such as a furnace, the temperature is raised to a predetermined temperature, and _{a processing gas containing ammonia (NH 3} ) as a reaction gas is added to the reaction chamber. The process of putting in is carried out. The input ammonia is decomposed into nitrogen and hydrogen, and as the nitrogen penetrates and diffuses into the surface of the steel, a nitride layer is formed on the surface of the steel. The processing gas is a mixed gas containing ammonia gas, and includes carbon dioxide gas, hydrocarbon, nitrogen gas, etc. in addition to ammonia gas.

At this time, since the degree of nitriding occurring in the reaction chamber cannot be observed visually, the ammonia decomposition rate can be measured to measure the degree of nitriding on the surface of the metal product. As a method of measuring the ammonia decomposition rate, a method of measuring the degree of nitriding by measuring a hydrogen partial pressure inside a reaction chamber and calculating a nitriding potential value based on this is widely used. The nitriding potential value refers to the nitriding performance and is the most important factor in determining the nitriding degree. The nitride potential (K _N ) is defined as follows in AMS2759-10A.

는 암모니아의 분압,

는 수소의 분압을 의미한다.here,

Is the partial pressure of ammonia,

Means the partial pressure of hydrogen.

However, in such a conventional nitriding treatment apparatus and a nitriding treatment method, ammonia gas and other gases (for example, carbon dioxide and nitrogen gas or hydrocarbon and nitrogen gas, etc.) are always mixed with a processing gas in a constant ratio into the reaction chamber, In order to control the nitriding potential value that can control the nitriding degree, a separate gas cracking furnace was required. For example, by decomposing ammonia gas in a separate gas decomposition furnace to generate decomposed ammonia gas consisting of a mixture of nitrogen and hydrogen, and adjusting the amount of decomposed ammonia gas supplied to the reaction chamber, the nitriding potential value could be adjusted.

Accordingly, in the conventional nitriding treatment device and the nitriding treatment method, it is necessary to additionally install an expensive ammonia gas decomposition furnace to generate hydrogen for controlling the nitriding potential value, thereby increasing the cost of the nitriding treatment device and the installation space. There is a problem that a lot of this is required and the amount of processing gas consumed in the nitriding treatment step is also excessively increased.

The present invention is to solve various problems, including the above problems, by using a reaction chamber as a decomposition furnace for ammonia gas when nitriding a metal product, and pyrolyzing the ammonia gas contained in the processing gas inside the reaction chamber. An object of the present invention is to provide a nitriding treatment apparatus and a nitriding treatment method capable of easily controlling the degree of nitriding of a metal product occurring in a reaction chamber by generating hydrogen and controlling a nitriding potential value using the same. However, these problems are exemplary, and the scope of the present invention is not limited thereby.

According to an embodiment of the present invention, a nitriding treatment apparatus is provided.

According to an embodiment of the present invention, the nitridation treatment apparatus includes: a reaction chamber having a treatment space formed therein so as to perform a metal nitridation treatment; A processing gas supply unit for supplying a processing gas including ammonia gas to the reaction chamber; A discharge unit for discharging the process gas decomposed or undecomposed in the reaction chamber; A sensor unit detecting a partial pressure of hydrogen in the reaction chamber; And calculating a nitriding potential value inside the reaction chamber by receiving the partial pressure of hydrogen from the sensor unit, and controlling an internal temperature of the reaction chamber and a flow rate of the processing gas supplied to the reaction chamber in connection with the nitriding potential value. It includes;

According to an embodiment of the present invention, the control unit closes the processing gas supply unit after the ammonia gas is introduced into the reaction chamber, and sets the internal temperature of the reaction chamber to a set temperature in order to decompose the input ammonia gas. The flow rate of the processing gas introduced into the reaction chamber may be adjusted by controlling the opening and closing of the processing gas supply unit so that the nitridation potential value is maintained at a preset reference value after reaching the set temperature.

According to an embodiment of the present invention, the nitridation apparatus may generate hydrogen by decomposing the ammonia gas in the reaction chamber, and may not have a separate ammonia gas decomposition furnace other than the reaction chamber.

에 의해 상기 질화 포텐셜 값을 계산할 수 있다.According to an embodiment of the present invention, the control unit, [Equation 1]

The nitriding potential value can be calculated by.

According to an embodiment of the present invention, the control unit may control to close the discharge unit when the internal pressure of the reaction chamber is less than a preset pressure and open the discharge unit when the pressure is greater than or equal to the preset pressure.

According to an embodiment of the present invention, the control unit may control the flow rate of the processing gas by controlling the processing gas supply unit by an ON/OFF control method or a PID control method.

According to an embodiment of the present invention, the sensor unit, a hydrogen sensor; A pump for pumping the process gas discharged through the gas discharge line and supplying it to the hydrogen sensor; And an exhaust line for exhausting the process gas that has passed through the hydrogen sensor to the gas discharge line.

According to another aspect of the present invention, there is provided a nitriding treatment method using a reaction chamber in which a treatment space is formed therein, and a treatment gas including ammonia gas is introduced into the treatment space for nitriding a metal.

According to an embodiment of the present invention, the nitriding treatment method includes: introducing the ammonia gas into the reaction chamber through a processing gas supply unit; After closing the processing gas supply unit, heating the temperature inside the reaction chamber to a preset temperature to decompose the ammonia gas to generate hydrogen; Deriving a nitriding potential value inside the reaction chamber through a sensor unit after the temperature inside the reaction chamber reaches the set temperature; And when the derived nitriding potential value reaches a preset reference value, the ammonia injected into the reaction chamber by controlling the processing gas supply unit so that the nitriding potential value inside the reaction chamber is maintained at a preset reference value. It may include a; nitriding potential control step of adjusting the flow rate of the gas.

에 의해 계산될 수 있다.According to an embodiment of the present invention, the nitriding potential value is [Equation 1]

Can be calculated by

)은 상기 반응 챔버로 투입된 상기 암모니아 가스가 분해되면서 생성된 상기 수소에 의한 것일 수 있다.According to an embodiment of the present invention, the partial pressure of hydrogen contained in [Equation 1] (

) May be due to the hydrogen generated while the ammonia gas introduced into the reaction chamber is decomposed.

According to an embodiment of the present invention, the set temperature may have a range of 450°C to 650°C.

According to an embodiment of the present invention, in the nitriding treatment method, when the internal pressure of the reaction chamber is less than a preset pressure, the discharging part for discharging the decomposed or undecomposed process gas in the reaction chamber is closed, and the When the pressure is higher than the set pressure, the discharge unit may be opened.

According to an embodiment of the present invention, the flow rate of the ammonia gas may be adjusted by controlling the process gas supply unit by an on/off control method or a PID control method.

According to an embodiment of the present invention made as described above, the reaction chamber is used as a decomposition furnace for ammonia during nitriding of a metal product, and ammonia contained in the reaction gas is pyrolyzed inside the reaction chamber to generate hydrogen. Using this, the nitriding potential value can be easily controlled.

Accordingly, it is possible to easily control the degree of nitriding of metal products occurring in the reaction chamber of the nitriding apparatus without the need to install a separate ammonia gas decomposition furnace. Of course, the scope of the present invention is not limited by these effects.

1 is a cross-sectional view schematically illustrating a nitriding treatment apparatus according to an embodiment of the present invention.
2 is a cross-sectional view schematically showing a processing gas supply unit of the nitriding treatment apparatus of FIG.
3 is a schematic cross-sectional view of a nitriding treatment apparatus according to another embodiment of the present invention.
4 is a flowchart schematically illustrating a nitriding treatment method according to another embodiment of the present invention.
5 is a graph showing a process of controlling an internal temperature and a nitriding potential value of a reaction chamber according to the nitriding treatment method of FIG. 4.
6 is an image showing a result of controlling a degree of nitriding of a metal product through control of a nitriding potential value in a nitriding treatment apparatus and a nitriding treatment method according to various embodiments of the present invention.

Hereinafter, various exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, and the scope of the present invention is as follows. It is not limited to the examples. Rather, these embodiments are provided to make the present disclosure more faithful and complete, and to completely convey the spirit of the present invention to those skilled in the art. In addition, in the drawings, the thickness or size of each layer is exaggerated for convenience and clarity of description.

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the drawings, for example, depending on manufacturing techniques and/or tolerances, variations of the illustrated shape can be expected. Accordingly, embodiments of the inventive concept should not be construed as being limited to the specific shape of the region shown in the present specification, but should include, for example, a change in shape caused by manufacturing.

1 is a cross-sectional view schematically showing a nitriding treatment apparatus 100 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view schematically showing a processing gas supply unit 20 of the nitridation treatment apparatus 100 of FIG. 1, 3 is a schematic cross-sectional view of a nitriding treatment apparatus 200 according to another embodiment of the present invention.

First, as shown in FIG. 1, the nitridation treatment apparatus 100 according to an embodiment of the present invention includes a reaction chamber 10, a processing gas supply unit 20 and a discharge unit 30, and a sensor unit ( 40), a control unit 50, a gas flow fan unit 60, a cooling unit 70, a vacuum unit 80, and a burning gas supply unit 90.

As shown in FIG. 1, the reaction chamber 10 may be a type of furnace in which a processing space A is formed so as to perform a nitriding treatment of a metal product. More specifically, the reaction chamber 10 is supplied with a processing gas including ammonia gas from a processing gas supply unit 20 to be described later, and the internal temperature of the processing space A is constant at a constant temperature by a heater installed at one side. By holding it for a period of time, the surface of the metal product can be nitrided within it. In this case, in order to form a nitride layer having a desired thickness in the reaction chamber 10, the internal temperature and duration may be variously adjusted.

In addition, a gas flow fan unit 60 is installed on the upper portion of the reaction chamber 10 to generate a flow of the processing gas in the processing space A by a fan rotating inside the processing space A, It is possible to induce the processing gas to be uniformly diffused and distributed within the processing space A. In addition, in order to prevent the fan of the gas flow fan unit 60 rotating inside the processing space A from being contaminated by the processing gas, nitrogen gas is finely introduced toward the fan through the gas flow fan unit 60 to purify the fan. I can.

In addition, the reaction chamber 10 is connected to the vacuum pump, the exhaust line 80 capable of forming a vacuum atmosphere by evacuating the air inside the processing space A, and the inside of the processing space A after nitrification of metal products. A cooling unit 70 capable of discharging the heat may be connected.

1 and 2, the processing gas supply unit 20 may supply a processing gas to the reaction chamber 10. More specifically, the processing gas may be _{a mixed gas including at least one of nitrogen (N 2} ) gas, ammonia (NH 3) gas, carbon dioxide (CO ₂ ) gas, carbon monoxide (CO) gas, and hydrocarbon gas. In addition, the processing gas supply unit 20 includes a first gas supply line 21 for supplying nitrogen gas, a second gas supply line 22 for supplying ammonia gas, and any one of carbon dioxide gas, carbon monoxide gas, and hydrocarbon gas. It is connected to the third gas supply line 23 and the first gas supply line 21, the second gas supply line 22, and the third gas supply line 23 for supplying one gas, so that the processing gas is transferred to the reaction chamber. It may include a fourth gas supply line 25 for supplying to (10).

The first gas supply line 21, the second gas supply line 22, and the third gas supply line 23 of the process gas supply unit 20 are provided with a mass flow controller (MFC). Each is installed, the mass flow controller M is controlled to open and close by the control unit 50, it is possible to finely control the processing gas supplied to the reaction chamber 10, respectively.

For example, as shown in FIG. 2, the first gas supply line 21 for supplying nitrogen gas is a high-pressure nitrogen supply line 21b to rapidly increase the pressure in the processing space A of the reaction chamber 10 Is provided, it is possible to fill the nitrogen gas into the processing space A at high pressure through the high-pressure nitrogen supply line 21b. In addition, when the pressure in the processing space A reaches a certain pressure through the high-pressure nitrogen supply line 21b, nitrogen gas is precisely supplied through the main nitrogen supply line 21a, and the main nitrogen supply line 21a It is possible to precisely control the flow rate of nitrogen gas through the first MFC (M1) installed in. In addition, since a nitrogen bypass line 21c is provided, it can be used as a safety device for discharging the processing gas in the processing space A of the reaction chamber 10 when an abnormality occurs during the nitriding process.

Each line (21a, 21b, 21c) of the first gas supply line 21 is equipped with a solenoid valve (V) to control opening and closing, and a pressure sensor (P) and a pressure gauge (G) are provided on one side. As a result, the pressure of the first gas supply line 21 can be appropriately adjusted. In addition, a pressure regulator R is installed at an upstream portion of the main nitrogen supply line 21a to precisely control the pressure of the nitrogen gas supplied to the main nitrogen supply line 21a.

In addition, the second gas supply line 22 includes a main ammonia supply line 22a and a manual valve capable of accurately supplying ammonia gas to the processing space A of the reaction chamber 10 through the second MFC (M2). An ammonia bypass line 22b that can be used when the second MFC M2 fails as a bypass line by may be included. The main ammonia supply line 22a is provided with a solenoid valve V to control opening and closing, and a pressure sensor P and a pressure gauge G are provided on one side to provide the pressure of the second gas supply line 22 Can be adjusted appropriately.

At this time, even after the nitriding process, if ammonia gas is filled in the second gas supply line 22 and the second MFC (M2), liquefaction occurs, resulting in a failure of the second MFC (M2), a failure of the solenoid valve (V), etc. Can cause. Accordingly, the processing gas supply unit 20 supplies nitrogen gas to the second gas supply line 22 to purify the second gas supply line 22, so that the main nitrogen supply line 21a and the 2 A purge line 24 connecting one side of the gas supply line 22 may be provided. Accordingly, after the nitriding treatment process, the second gas supply line 22 may be purged with nitrogen gas supplied to the purge line 24 for cleaning.

In addition, the third gas supply line 23 is capable of accurately supplying any one of carbon dioxide gas, carbon monoxide gas, and hydrocarbon gas to the processing space A of the reaction chamber 10 through the third MFC (M3). The main supply line 23a and a bypass line by a manual valve may include a bypass line 23b that can be used when the third MFC M3 fails. The main supply line 23a is provided with a solenoid valve V to control opening and closing, and a pressure sensor P and a pressure gauge G are provided on one side so that the third gas supply line 23 controls the pressure. It can be adjusted accordingly.

As shown in FIG. 1, the discharge unit 30 may discharge the decomposed or undecomposed process gas in the reaction chamber 10 through the gas discharge line 31. In addition, a burning gas supply unit 90 is connected to the rear end of the discharge unit 30 to inject LPG gas or LNG gas into the discharge unit 30 to burn the exhausted ammonia gas.

The sensor unit 40 includes a hydrogen sensor S installed on the gas discharge line 31 connecting the reaction chamber 10 and the discharge unit 30 to detect the partial pressure of hydrogen inside the reaction chamber 10 can do. More specifically, the sensor unit 40 pumps the process gas discharged to the gas discharge line 31 and discharges the process gas that has passed through the pump 41 and the hydrogen sensor S to supply the hydrogen sensor S. It may include an exhaust line 42 that exhausts to the line 31.

The control unit 50 is electrically connected to the reaction chamber 10, the processing gas supply unit 20, the discharge unit 30, and the sensor unit 40 to control each component, and the sensor unit 40 ) To calculate the nitridation potential value inside the reaction chamber 10 by receiving the hydrogen partial pressure sensed from the hydrogen sensor S, and the internal temperature of the reaction chamber 10 and the flow rate of the processing gas supplied to the reaction chamber 10 And it is possible to control whether the opening or closing of the discharge unit 30.

For example, the control unit 50 may inject ammonia gas into the reaction chamber 10 through the processing gas supply unit 20 to form an ammonia atmosphere inside the reaction chamber 10, and then close the processing gas supply unit 20 and the The internal temperature of the reaction chamber 10 is increased to a preset temperature. In this case, the set temperature is a temperature at which ammonia gas can be decomposed, and may have a range of 450°C to 650°C, for example. As the internal temperature of the reaction chamber 10 is increased, ammonia gas is decomposed in the reaction chamber 10 to generate hydrogen. As hydrogen is generated in the reaction chamber 10, the pressure inside the reaction chamber 10 increases, and a change in the nitridation potential starts to appear.

The controller 50 may receive the partial pressure of hydrogen transmitted from the sensor unit 40 after the internal temperature of the reaction chamber 10 reaches a set temperature, and calculate a nitriding potential value based on this. The control unit 50 compares the calculated nitriding potential value with a reference value of a preset nitriding potential so that the nitriding potential value inside the reaction chamber 10 is maintained at the reference value, so that the difference between the calculated nitriding potential value and the reference value is minimum. Control is performed in the direction of Specifically, the control unit 50 may control the opening and closing of the gas supply line constituting the processing gas supply unit 20 to control the flow rate of the processing gas, for example, ammonia gas, which is introduced into the reaction chamber 10.

In addition, the control unit 50 prevents the occurrence of a problem such as an explosion of the reaction chamber 10 due to the hydrogen generated during the decomposition of the ammonia gas, the internal pressure of the reaction chamber 10 rises above a predetermined pressure. To this end, by receiving an internal pressure from a pressure sensor (not shown) mounted in the reaction chamber 10, the opening and closing of the discharge unit 30 may be controlled so that the internal pressure does not rise above a preset pressure.

Therefore, the control unit 50 performs control to increase the internal temperature of the reaction chamber 10 in a state in which both the processing gas supply unit 20 and the discharge unit 30 are closed at the beginning of the ammonia gas decomposition step. When the pressure inside the chamber 10 reaches a predetermined reference pressure, a control is performed to open the discharge unit 30 to prevent an increase in pressure.

In this case, as the control method through the control unit 50, an on/off control method or a PID control method may be selectively used according to the required nitriding processing precision of the metal product.

According to the technical idea of the present invention, ammonia gas is decomposed in the reaction chamber 10 disconnected from the outside before the nitriding treatment is performed under the control of the above-described control unit 50 to generate hydrogen, and thus the reaction The chamber 10 functions as a decomposition furnace of ammonia gas for hydrogen generation, which is a basis for controlling the nitriding potential value, in addition to the processing space in which the nitriding treatment is performed.

The present inventors have recognized that it is difficult to effectively implement the control according to the technical idea of the present invention when the calculation of the nitridation potential value inside the reaction chamber 10 uses the equation specified in the conventional AMS2759-10A. Accordingly, the present inventors have proposed the following [Equation 1] as a calculation formula of the nitridation potential value optimized for the control method of the present invention through a number of experiments.

[Equation 1]

Kn: Nitriding potential value

X: ammonia decomposition rate

: 수소 분압

: Hydrogen partial pressure

The present inventors perform control of the nitriding potential value based on the calculation formula of the nitriding potential value according to the above [Equation 1], thereby using the reaction chamber 10 as an ammonia gas decomposition furnace without a separate ammonia gas decomposition furnace. It was possible to control the nitriding potential value with high precision.

For example, when the reference value of the nitriding potential (Kn) value is designated as C in the nitriding process of metal products, the amount of ammonia gas decreases and the amount of hydrogen increases due to the decomposition of the ammonia gas in the reaction chamber 10. The nitriding potential value can be reduced to C or less. Then, the controller 50 may control only the second gas supply line 22 of the processing gas supply unit 20 to supply only ammonia gas among the processing gases to the reaction chamber 10 for a predetermined time. Accordingly, as the amount of ammonia gas in the reaction chamber 10 increases, the nitriding potential value may rise again to exceed C. In this case, when the second gas supply line 22 is closed again, the ammonia gas is decomposed again, and the nitriding potential value is slightly changed within the effective value, and the reference value C can be continuously maintained.

The method of measuring the hydrogen partial pressure in the reaction chamber 10 may be configured as a circulation type as described above, but in addition, as in the nitridation treatment apparatus 200 according to another embodiment of the present invention of FIG. 3, the sensor unit 40 ) May be installed directly in the reaction chamber 10 to measure the hydrogen partial pressure.

For example, as shown in FIG. 3, by directly installing the hydrogen sensor S on one side of the reaction chamber 10, the partial pressure of hydrogen in the processing space A of the reaction chamber 10 can be directly measured. Accordingly, during the nitriding process, the partial pressure of hydrogen in the reaction chamber 10 can be continuously monitored in real time. In this way, the nitridation potential value can also be checked in real time by the hydrogen partial pressure sensed in real time.

Hereinafter, a nitriding treatment method using the above-described nitriding treatment apparatus will be described in detail.

4 is a flow chart schematically showing a nitridation treatment method according to another embodiment of the present invention, and FIG. 5 is a temperature inside the reaction chamber 10 over time as the nitridation treatment method shown in the flow chart of FIG. 4. A graph showing the change and change of the nitridation potential (Kn) is shown.

4 and 5, the nitridation treatment method may proceed in the order of an ammonia input step (S10), ammonia decomposition step (S20), a nitridation potential derivation step (S30), and a nitridation potential control step (S40). have.

In the ammonia input step S10, the processing gas supply unit 20 may be opened to introduce ammonia gas into the reaction chamber 10. In this case, the internal temperature T1 of the reaction chamber 10 may have a temperature at which decomposition of ammonia gas does not substantially occur, for example, in the range of room temperature to 400°C.

Subsequently, in the ammonia decomposition step (S20), after the processing gas supply unit 20 and the discharge unit 30 are closed, the temperature inside the reaction chamber 10 may be heated to a preset temperature T2. The set temperature is a temperature at which ammonia gas can be decomposed, and may have a range of 450°C to 650°C, for example.

Accordingly, a step of decomposing ammonia gas present in the reaction chamber 10 into hydrogen and nitrogen is performed during the process of increasing the temperature in the reaction chamber 10 to reach the set temperature T2. In this step, as hydrogen is generated, the nitriding potential value starts to decrease as shown in FIG. 5.

Subsequently, in the nitridation potential derivation step (S30), after the temperature inside the reaction chamber 10 reaches the set temperature T2, the nitridation potential value inside the reaction chamber 10 is determined by the hydrogen sensor (S) of the sensor unit 40. Based on the hydrogen partial pressure sensed through ), it is derived according to [Equation 1].

More specifically, in the nitriding potential derivation step (S30), by continuously closing the process gas supply unit 20 and the discharge unit 30 after the ammonia decomposition step (S20), the ammonia gas is decomposed inside the reaction chamber 10. The generated hydrogen can be accumulated in the reaction chamber 10 without being discharged to the outside. Accordingly, the nitriding potential value gradually decreases as the hydrogen partial pressure inside the reaction chamber 10 increases, and at this time, by detecting the hydrogen partial pressure inside the reaction chamber 10 in real time through the hydrogen sensor S, the nitriding potential Changes in values can be sensed in real time. In some cases, when the amount of hydrogen generated in this step is too large and the internal pressure of the reaction chamber 10 increases above the reference pressure, the discharge unit 30 may be opened to control the pressure to be maintained below the reference pressure. .

Subsequently, when the sensed nitridation potential value inside the reaction chamber 10 decreases to a preset reference value, the nitridation potential value inside the reaction chamber 10 will continue to be maintained at the reference value through the nitridation potential control step S40. Thus, by controlling the opening and closing of the processing gas supply unit 20, the flow rate of the ammonia gas injected into the reaction chamber 10 can be appropriately controlled.

In the nitriding potential control step (S40), an on/off control method or a PID control method may be selectively used as the control method of the ammonia gas flow rate according to the required precision of the nitriding treatment of the metal.

For example, as shown in FIG. 5, in the case of the on/off control method, the nitriding potential value continuously changes slightly based on the reference value, but the configuration of the device is relatively simple, and accordingly, the process can be performed at low cost. Therefore, it can be preferably used when high precision is not required.

Conversely, when high precision of the nitriding process is required, it can be controlled by the PID control method. In this case, the flow of ammonia introduced into the reaction chamber 10 can be controlled very finely with high precision according to a change in the partial pressure of hydrogen transmitted from the hydrogen sensor S, and accordingly, the nitriding potential value Kn is shown in FIG. 5. It can be controlled very precisely as shown in.

According to the nitridation treatment apparatus and nitridation treatment method according to various embodiments of the present invention, the reaction chamber 10 is used as a decomposition furnace for ammonia gas during the nitridation treatment of metal, The included ammonia gas is pyrolyzed to generate hydrogen, and the nitriding potential value can be easily controlled using this.

Accordingly, an expensive ammonia decomposition furnace is not required to generate hydrogen for controlling the nitriding potential value, and the nitriding potential value can be controlled by adjusting only the supply amount of ammonia gas among the processing gases, so the amount of processing gas consumed is also You can save. In addition, it is possible to have the effect of being able to easily adjust the degree of nitriding of the metal product occurring in the reaction chamber 10 by controlling the nitriding potential value without configuring an additional device.

As described above, the nitriding treatment apparatus and the nitriding treatment method of the present invention are applied to gears, hubs, shafts, etc. that require wear resistance and impact toughness due to vibration among automobile parts by adjusting the nitriding concentration of the nitride layer in the metal nitriding treatment. Can be used.

Hereinafter, an experimental example for aiding understanding of the present invention will be described. It goes without saying that the following experimental examples are presented as illustrative examples to aid understanding of the present invention, and the present invention is not limited to the following experimental examples.

Nitriding treatment of low-carbon steel was performed using the nitridation treatment apparatus 100 shown in FIG. 1. The composition of the low carbon steel used in this experimental example is shown in Table 1.

element C Mn P S Fe Composition (wt%) 0.1 to 0.15 <0.6 <0.05 <0.05 bal.

The temperature of the reaction chamber 10 for the nitriding treatment was maintained at 520°C, and the nitrogen (N ₂ ), ammonia (NH ₃ ), and carbon dioxide (CO ₂ ) ratio were appropriately adjusted to control the nitriding potential in the atmosphere of the nitriding treatment. Nitriding potential values (Kn) were controlled at 0.3, 1, 2, and 7. At this time, the flow rate of ammonia introduced into the reaction chamber 10 was controlled by the PID control method.

6 shows the results of observing the surface of the low-carbon steel when the nitriding potential values are 0.3, 1, 2, and 7.

Referring to FIG. 6, it can be seen that a nitride layer having various phases is formed on the surface of a low-carbon steel having an α phase as the nitriding potential value is changed during the nitriding treatment.

Specifically, when the nitriding potential value is maintained at 0.3, it can be confirmed that a γ'phase is formed. When the nitriding potential value is increased to 1 and maintained, compared to the case where the nitriding potential value is 0.3, it can be seen that the γ'phase is generated thicker on the surface. If the nitriding potential value is increased and maintained to 2, it can be seen that an ε phase is generated on top of the γ'phase. If the nitriding potential value is further increased to 3 and maintained, the ε phase becomes γ 'It can be seen that it is generated thicker to the lower region of the phase (upper). Accordingly, as shown in FIG. 6, it can be seen that the phase of the nitride layer formed on the surface of the low-carbon steel can be controlled by precisely controlling the nitriding potential value.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary, and those of ordinary skill in the art will appreciate that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

10: reaction chamber
20: processing gas supply unit
30: discharge unit
40: sensor unit
50: control unit
60: gas flow fan unit
70: cooling unit
80: vacuum part
90: burning gas supply
100, 200: nitriding treatment device

Claims (12)

A reaction chamber having a processing space formed therein to perform a metal nitriding treatment;
A processing gas supply unit for supplying ammonia gas as processing gas to the reaction chamber;
A discharge unit for discharging the process gas decomposed or undecomposed in the reaction chamber;
A sensor unit detecting a partial pressure of hydrogen in the reaction chamber; And
Receives the partial pressure of hydrogen from the sensor unit, calculates a nitridation potential value inside the reaction chamber, and controls the internal temperature of the reaction chamber and a flow rate of the processing gas supplied to the reaction chamber in connection with the nitridation potential value. Includes;
The control unit,
After the ammonia gas is introduced into the reaction chamber, both the processing gas supply unit and the discharge unit are closed so that the ammonia gas is decomposed to generate hydrogen in the reaction chamber disconnected from the outside, and then the ammonia gas injected Raise the internal temperature of the reaction chamber to a set temperature in order to decompose,
The processing gas supply unit and the discharge unit are continuously closed so that the hydrogen generated by decomposing the ammonia gas in the reaction chamber is not discharged to the outside and can be accumulated in the reaction chamber, and the inside of the closed reaction chamber The change in the nitriding potential value gradually decreasing with the increase of the hydrogen partial pressure of is calculated in real time,
After the derived nitriding potential value reaches a preset reference value, the ammonia gas injected into the reaction chamber is controlled by controlling the opening and closing of the processing gas supply so that the nitriding potential value is maintained at the preset reference value. Nitriding treatment device that regulates only the flow rate. The method of claim 1,
The nitriding treatment device,
Hydrogen is generated by the decomposition of the ammonia gas in the reaction chamber, and a nitriding treatment apparatus having no separate ammonia gas decomposition furnace other than the reaction chamber. The method of claim 1,
The control unit,
A nitriding treatment device that calculates the nitriding potential value by the following [Equation 1].
[Equation 1]

Kn: Nitriding potential value
X: ammonia decomposition rate

: Hydrogen partial pressure The method of claim 1,
The control unit,
When the internal pressure of the reaction chamber is less than a preset pressure, the discharge unit is closed, and when the pressure is greater than or equal to the preset pressure, the discharge unit is controlled to open. The method of claim 1,
The control unit,
A nitridation processing apparatus for controlling the flow rate of the processing gas by controlling the processing gas supply unit by an ON/OFF control method or a PID control method. The method of claim 1,
The sensor unit,
Hydrogen sensor;
A pump for pumping the process gas discharged through a gas discharge line and supplying it to the hydrogen sensor; And
An exhaust line for exhausting the process gas passing through the hydrogen sensor to the gas discharge line;
Containing a nitriding treatment device. In the nitriding treatment method using a reaction chamber in which a treatment space is formed inside and ammonia gas is introduced as a treatment gas for nitriding a metal into the treatment space,
Introducing the ammonia gas into the reaction chamber through a processing gas supply unit;
After closing the processing gas supply unit, heating the temperature inside the reaction chamber to a preset temperature to decompose the ammonia gas to generate hydrogen;
Deriving a nitriding potential value inside the reaction chamber through a sensor unit after the temperature inside the reaction chamber reaches the set temperature; And
When the derived nitriding potential value reaches a preset reference value, the ammonia injected into the reaction chamber by controlling the processing gas supply unit so that the nitriding potential value inside the reaction chamber is maintained at the preset reference value. Nitriding potential control step of adjusting only the flow rate of the gas;
In the step of generating hydrogen,
Closing both the processing gas supply unit and the discharge unit for discharging the processing gas decomposed or undecomposed in the reaction chamber so that the reaction chamber can be disconnected from the outside,
In the nitridation potential derivation step,
The processing gas supply unit and the discharge unit are continuously closed so that the hydrogen generated by decomposing the ammonia gas in the reaction chamber is not discharged to the outside and can be accumulated in the reaction chamber, and the inside of the closed reaction chamber A nitriding treatment method for sensing, in real time, a change in the nitriding potential value that gradually decreases with an increase in the hydrogen partial pressure of. The method of claim 7,
The nitriding potential value is calculated by the following [Equation 1].
[Equation 1]

Kn: Nitriding potential value
X: ammonia decomposition rate

: Hydrogen partial pressure The method of claim 8,
The partial pressure of hydrogen contained in [Equation 1] above (

) Is by the hydrogen generated while the ammonia gas introduced into the reaction chamber is decomposed. The method of claim 7,
The set temperature has a range of 450°C to 650°C, a nitriding treatment method. The method of claim 7,
In the nitriding treatment method,
When the internal pressure of the reaction chamber is less than a preset pressure, the discharge unit for discharging the decomposed or undissolved process gas in the reaction chamber is closed, and if the pressure is higher than the preset pressure, the discharge unit is opened. The method of claim 7,
In the nitriding potential control step,
A nitriding treatment method for controlling the processing gas supply unit by an on/off control method or a PID control method to adjust the flow rate of the ammonia gas.

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