Method and apparatus for processing metal components

Abstract

The present invention is a method for treating a metallic member using a treatment furnace, the method comprising a step for introducing an activation atmosphere gas into the treatment furnace, a step for heating the activation atmosphere gas in the treatment furnace to a first temperature, a step for introducing a nitriding atmosphere gas or a soft nitriding atmosphere gas into the treatment furnace, and a step for heating the nitriding atmosphere gas or the soft nitriding atmosphere gas in the treatment furnace to a second temperature. The activation atmosphere gas can be introduced into the treatment furnace through an activation atmosphere gas introduction pipe. An organic solvent in a liquid form is introduced into the activation atmosphere gas introduction pipe, which is in a state where the introduction of the activation atmosphere gas has been continued, several times intermittently.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for treating a metal member, which activate the surface of the metal member prior to subjecting the metal member to gas nitriding treatment or gas soft nitriding treatment.

Background Art

[0002] Among the surface hardening treatments of steel materials, the need for nitriding treatment, which is a low heat treatment strain treatment, is high, and recently, in particular, the interest in gas nitriding treatment or gas soft nitriding treatment has been increasing. In automotive parts, dies, and other stainless parts, gas nitriding treatment or gas soft nitriding treatment is widely applied to improve fatigue resistance, wear resistance, and corrosion resistance.

[0003] When these treatments are applied to the surface of a member made of alloy steel, particularly high alloy steel such as stainless steel, the formation of a passive film (such as an oxide) present on the member surface hinders the penetration and diffusion of nitrogen and carbon into the metal member surface, resulting in problems such as defective treatment and uneven treatment of the member. Therefore, prior to these diffusion penetration treatments, surface activation treatment of the metal member is performed.

[0004] As a surface activation treatment, for example, a method using a chloride-based compound (activator) typified by malcolmizing treatment is known. As the chloride, vinyl chloride resin, ammonium chloride, methylene chloride, etc. are used.

[0005] The chloride is placed in a treatment furnace together with the metal member and heated. By this heating, the chloride decomposes to generate HCl. The generated HCl destroys (modifies) the passive film on the metal member surface and activates the surface. As a result, diffusion penetration treatments such as nitriding and carburizing in the next step become more reliable.

[0006] However, surface activation of metal components using chlorides as described above requires pre-installation of chlorides around the metal components in the treatment furnace. This process is difficult to automate and requires manual work by an operator. Furthermore, controlling the amount of HCl produced is difficult, so optimal results cannot always be obtained.

[0007] Furthermore, the generated HCl reacts with ammonia contained in the atmospheric gas during gas nitriding or gas soft nitriding to produce ammonium chloride. This ammonium chloride can not only accumulate in the processing furnace and exhaust system, potentially causing problems, but it can also remain on the surface of metal components (workpieces), leading to a decrease in corrosion resistance and fatigue strength.

[0008] A method for activating the surface of metal components using a fluorine compound (NF3) belonging to the same halogen group as chlorides has also been put into practical use (for example, Japanese Patent Publication No. 3-44457 (Patent Document 1)). NF3 decomposes upon heating to produce fluorine. The produced fluorine transforms the passivation film on the surface of the metal component into a fluoride film, thereby activating the surface.

[0009] However, surface activation of metal components using fluorine compounds (NF3) as described above requires advanced treatment to neutralize NF3 and HF that may be present in exhaust gases, which hinders the widespread adoption of this method.

[0010] As a pretreatment method that does not use chlorides or fluorine compounds, a method using carbon compounds has also been put into practical use (for example, Japanese Patent No. 4861703 (Patent Document 2), Japanese Patent Application No. 9-38341 (Patent Document 3), and Japanese Unexamined Patent Publication No. 10-219418 (Patent Document 4)). Specifically, acetylene is introduced into the furnace, and the HCN produced in the reaction process starting from its thermal decomposition reduces the passivation film on the surface of the metal member, thereby activating the surface (Japanese Patent Application No. 9-38341 (Patent Document 3), and Japanese Unexamined Patent Publication No. 10-219418 (Patent Document 4)).

[0011] Furthermore, a method for activating metal surfaces using carbon-nitrogen compounds is described in Japanese Patent No. 5826748 (Patent Document 5). In addition to methods using urea and acetamide, which are solids at room temperature, Patent No. 5826748 (Patent Document 5) also mentions a method using formamide, which is a liquid at room temperature.

[0012] It has been known since the 1970s that CO gas forms HCN in furnaces ("Heat Treatment", Vol. 18, No. 5, pp. 255-262 (Kiyomitsu Otomo) (Non-Patent Literature 1)). Based on this knowledge, it is thought that carbon compounds and carbon-nitrogen compounds have been selected and studied as substances that generate CO gas in the furnace during the reaction process.

[0013] However, for SUS-based materials with stronger passivation films (such as SUS310S, which have high Cr and Ni content), it is known that the method using HCN (carbon compounds, nitrogen compounds) is less effective in activating the material than the method using HCl (chloride). Therefore, it is necessary to use either the HCN method or the HCl method depending on the grade of the steel. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] Japanese Patent Application Publication No. 3-44457 [Patent Document 2] Patent No. 4861703 [Patent Document 3] Japanese Patent Application No. 9-38341 [Patent Document 4] Japanese Patent Application Publication No. 10-219418 [Patent Document 5] Patent No. 5826748 [Non-Patent Document 1] "Heat Treatment," Vol. 18, No. 5, pp. 255-262 (Kiyomitsu Otomo) [Overview of the Initiative] [Problems that the invention aims to solve]

[0015] Carbon compounds and carbon-nitrogen compounds that are solid at room temperature must be placed in advance around the metal components inside the processing furnace. This process is difficult to automate and requires manual work by operators. Furthermore, it is difficult to control the amount of HCN produced, so the optimal effect cannot always be obtained.

[0016] Carbon compounds and nitrogen compounds, which are gases at room temperature, have the advantage of being able to be introduced into the furnace in appropriate amounts using a mass flow controller. However, handling gas cylinders is not easy, they take up space, and measures must be taken to prevent gas leaks from the piping. Furthermore, depending on the type of carbon compound or nitrogen compound (especially the type of active species), some may not be compatible with mass flow controllers (making it difficult to control the amount introduced).

[0017] Carbon compounds and nitrogen compounds, which are liquid at room temperature, are generally gasified before being introduced into the furnace in order to control the amount introduced into the furnace (see paragraph 0010 of Japanese Patent No. 4861703 (Patent Document 2): "Since acetone, which is liquid at room temperature and atmospheric pressure, is used, a device for introducing acetone vapor is required").

[0018] Japanese Patent No. 5826748 (Patent Document 5) describes introducing liquid formamide directly into the hot zone of a tubular furnace (a small experimental furnace) using a probe (see paragraph 0081 of Japanese Patent No. 5826748 (Patent Document 5)). However, this method is difficult to apply to a general production furnace. This is because in a configuration where a probe is directly connected to a general production furnace, due to the high degree of heat dissipation in the production furnace, the formamide in the probe vaporizes and causes backflow, preventing the introduction of the desired amount into the furnace. Furthermore, there is also a concern that the backflowed formamide may precipitate in the undesired piping, causing pipe blockage.

[0019] The inventor of the present invention has found that by introducing an organic solvent that is liquid at room temperature (which may also include chlorides in addition to carbon compounds and carbon-nitrogen compounds) into the activation atmosphere gas introduction pipe while continuously introducing the activation atmosphere gas into the treatment furnace, it is possible to effectively suppress the occurrence of a situation where the organic solvent vaporizes and backflows even when the treatment furnace is at a high temperature.

[0020] Furthermore, the inventor of the present invention has found that by intermittently introducing the organic solvent that is liquid at room temperature in multiple portions, it is possible to achieve the introduction of an appropriate amount of the organic solvent at a timing suitable for the state inside the treatment furnace.

[0021] The present invention was conceived based on the above findings. The object of the present invention is to provide a method and apparatus for treating a metal member that can practically activate the surface of the metal member using an organic solvent in a liquid state.

Means for Solving the Problems

[0022] The present invention is a method for treating a metal member using a treatment furnace, comprising a metal member input step of inputting a metal member into the treatment furnace, an activation atmosphere gas introduction step of introducing an activation atmosphere gas into the treatment furnace, a first heating step of heating the activation atmosphere gas in the treatment furnace to a first temperature, After the first heating step, a main atmosphere gas introduction step of introducing a nitriding atmosphere gas or a soft nitriding atmosphere gas into the processing furnace; A second heating step of heating the nitriding atmosphere gas or the soft nitriding atmosphere gas in the processing furnace to a second temperature in order to nitride or soft nitride the metal member; Comprising: In the activation atmosphere gas introduction step, the activation atmosphere gas is introduced into the processing furnace through an activation atmosphere gas pipe; During at least a part of the period of the first heating step, the activation atmosphere gas introduction step is carried out simultaneously; During this period, a liquid organic solvent is intermittently charged into the activation atmosphere gas introduction pipe a plurality of times A processing method characterized by the above. It is.

[0023] According to the present invention, by charging a liquid organic solvent (which may also be a chloride in addition to a carbon compound or a carbonitrogen compound) into the activation atmosphere gas introduction pipe in a state where the introduction of the activation atmosphere gas into the processing furnace is continued, even if the temperature of the processing furnace (first temperature) is high, the occurrence of the situation where the organic solvent vaporizes and flows backward can be effectively suppressed.

[0024] Further, according to the present invention, by charging the liquid organic solvent intermittently in a plurality of portions, it is possible to realize the charging of an appropriate amount of the organic solvent at a timing suitable for the state in the processing furnace.

[0025] For example, the first heating temperature is 400°C to 500°C.

[0026] According to this temperature range, while the activation treatment of the metal member proceeds favorably, the occurrence of the situation where the organic solvent vaporizes and flows backward is effectively suppressed.

[0027] Also, for example, the activation atmosphere gas contains ammonia gas, and the organic solvent is a compound containing at least one kind of hydrocarbon.

[0028] According to this, HCN, which is produced in the reaction process starting from the thermal decomposition of organic solvents, can reduce the passivation film on the surface of metal components and effectively activate the surface.

[0029] More specifically, for example, the organic solvent is one of formamide, xylene, and toluene.

[0030] In this case, for example, the inventors have confirmed in an actual production furnace that it is effective to add the organic solvent in amounts of 10 to 80 ml at a time at a substantially uniform rate over 1 to 2 minutes (preferably 10 to 2 minutes), and to add it 2 to 6 times with intervals of 10 minutes or more.

[0031] Alternatively, for example, the activated atmosphere gas may contain ammonia gas, and the organic solvent may be a compound containing at least one type of chlorine.

[0032] According to this, the HCl produced during the reaction process, which begins with the thermal decomposition of organic solvents, can reduce the passivation film on the surface of metal components and effectively activate the surface.

[0033] More specifically, for example, the organic solvent is one of trichloroethylene, tetrachloroethylene, and tetrachloroethane.

[0034] In this case, for example, the inventors have confirmed in an actual production furnace that it is effective to add the organic solvent in amounts of 10 to 80 ml at a time at a substantially uniform rate over 1 to 2 minutes (preferably 10 to 2 minutes), and to add it 2 to 6 times with intervals of 10 minutes or more.

[0035] Furthermore, at least as of the time of this application, inventions that exclude the condition of introducing a liquid organic solvent into an activated atmosphere gas introduction pipe are also covered by this patent.

[0036] In other words, the present invention is A method for processing metal components using a processing furnace, A metal component input step in which metal components are placed into the processing furnace, The process includes an activated atmosphere gas introduction step in which an activated atmosphere gas is introduced into the processing furnace, A first heating step in which the activated atmosphere gas in the processing furnace is heated to a first temperature, After the first heating step, a main atmosphere gas introduction step is performed in which a nitriding atmosphere gas or a soft nitriding atmosphere gas is introduced into the processing furnace, A second heating step is performed to heat the nitriding atmosphere gas or soft nitriding atmosphere gas in the processing furnace to a second temperature in order to nitride or soft nitride the metal member, Equipped with, During the first heating step, a liquid organic solvent is intermittently introduced into the processing furnace multiple times. Processing method characterized by That is the case.

[0037] According to this invention, by intermittently adding the organic solvent in liquid form in multiple stages, it is possible to add the appropriate amount of organic solvent at a timing that matches the conditions inside the processing furnace.

[0038] Furthermore, the present invention is Processing furnace and A metal member feeding mechanism for feeding metal members into the aforementioned processing furnace, An atmospheric gas introduction pipe is provided so as to be in communication with the processing furnace and introduces atmospheric gas into the processing furnace, An organic solvent feeding device that intermittently introduces a liquid organic solvent multiple times into the aforementioned atmospheric gas introduction piping, A heating device for heating the atmospheric gas inside the processing furnace to a predetermined temperature, Apparatus for metal members characterized by comprising That is the case.

[0039] According to the present invention, by introducing a liquid organic solvent (which may include chlorides in addition to carbon compounds and nitrogen compounds) into the atmosphere gas introduction piping while the activated atmosphere gas is continuously being introduced into the processing furnace, it is possible to effectively suppress the occurrence of the organic solvent vaporizing and flowing back, even when the temperature of the processing furnace is high.

[0040] Furthermore, according to the present invention, by intermittently adding the organic solvent in liquid form in multiple stages, it is possible to add the appropriate amount of organic solvent at a timing that matches the conditions inside the processing furnace.

[0041] The organic solvent injection device preferably has a check valve upstream of the atmospheric gas introduction piping.

[0042] This prevents backflow of the organic solvent, allowing for more precise injection of the correct amount of organic solvent. Furthermore, since unwanted vaporization of the organic solvent is suppressed, a general-purpose check valve can be used.

[0043] Furthermore, it is preferable that a dehumidifying device is provided in the middle of the atmospheric gas introduction piping.

[0044] According to this method, it is possible to effectively prevent performance degradation of metal components caused by moisture that may be present in the atmospheric gas.

[0045] Furthermore, it is preferable that the metal member input mechanism is configured to insert and remove the metal member horizontally into and out of the processing furnace.

[0046] According to this, even if precipitation of organic solvents occurs, the risk of contact between the precipitate and the metal component is relatively small, making it suitable. (In a configuration where the metal component is inserted and removed from the top of the furnace, the risk of the metal component coming into contact with the precipitate deposited around the furnace opening is relatively large.)

[0047] Furthermore, it is preferable that the atmospheric gas is an activated atmospheric gas, and that a second processing furnace for nitriding or soft nitriding is provided separately from the processing furnace.

[0048] According to this method, the activation treatment and the nitriding or soft nitriding treatment can be carried out in separate treatment furnaces, thus eliminating the risk of precipitation of organic solvents during the nitriding or soft nitriding treatment. Furthermore, since the nitriding or soft nitriding treatment and the subsequent activation treatment of the metal component can be carried out simultaneously, productivity is increased (compared to simply preparing two treatment units, there is no need to introduce organic solvents into the treatment furnace for the nitriding or soft nitriding treatment, resulting in cost reduction).

[0049] Furthermore, at least as of the time of this application, inventions that exclude the condition of introducing a liquid organic solvent into an activated atmosphere gas introduction pipe are also covered by this patent.

[0050] In other words, the present invention is Processing furnace and A metal member feeding mechanism for feeding metal members into the aforementioned processing furnace, An atmospheric gas injection pipe is provided so as to be in communication with the processing furnace and introduces atmospheric gas into the processing furnace, An organic solvent feeding device that intermittently feeds liquid organic solvent into the aforementioned processing furnace multiple times, A heating device for heating the atmospheric gas inside the processing furnace to a predetermined temperature, Apparatus for metal members characterized by comprising That is the case.

[0051] According to this invention, by intermittently adding the organic solvent in liquid form in multiple stages, it is possible to add the appropriate amount of organic solvent at a timing that matches the conditions inside the processing furnace. [Effects of the Invention]

[0052] According to the present invention, by intermittently adding the organic solvent in liquid form in multiple stages, it is possible to add the appropriate amount of organic solvent at a timing that matches the conditions inside the processing furnace.

[0053] Furthermore, according to one aspect of the present invention, by introducing a liquid organic solvent (which may include chlorides in addition to carbon compounds and nitrogen compounds) into the activated atmosphere gas introduction piping while the activated atmosphere gas is being continuously introduced into the processing furnace, it is possible to effectively suppress the occurrence of the organic solvent vaporizing and flowing back even when the temperature of the processing furnace is high. [Brief explanation of the drawing]

[0054] [Figure 1] This is a schematic diagram of a metal member processing apparatus according to a first embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of a circulating processing furnace (horizontal gas nitriding furnace). [Figure 3] This is an illustrative diagram showing an example of control regarding the input of organic solvents. [Figure 4] This is a schematic diagram of a modified example of the metal member processing apparatus according to the first embodiment. [Figure 5] This is a photograph of a circular stain. [Figure 6] This is a schematic diagram of a further modified example of the metal member processing apparatus according to the first embodiment. [Figure 7] This is a schematic diagram of a metal member processing apparatus according to a second embodiment of the present invention. [Figure 8] This is a schematic diagram of a modified example of the metal member processing apparatus according to the second embodiment. [Figure 9] This is a schematic diagram of a further modified example of the metal member processing apparatus according to the second embodiment. [Modes for carrying out the invention]

[0055] [First Embodiment] Figure 1 is a schematic diagram of a metal member processing apparatus 1 (nitriding processing apparatus) according to the first embodiment of the present invention. As shown in Figure 1, the processing apparatus 1 of this embodiment is equipped with a circulating processing furnace 2, and uses only two types of gases, ammonia and ammonia decomposition gas, as introduced into the circulating processing furnace 2. Ammonia decomposition gas is a gas also called AX gas, and is a mixed gas consisting of nitrogen and hydrogen in a ratio of 1:3.

[0056] (Overview of Processing Reactor 2) Figure 2 shows an example of the cross-sectional structure of the circulating processing furnace 2. In Figure 2, a cylinder 202 called a retort is placed inside the furnace wall (also called a bell) 201, which contains a heater (heating device) 201h, and further inside that, a cylinder 204 (φ700mm × 1000mm) called an internal retort is placed (in Figure 2, the heater 201h is conceptually illustrated, and the actual arrangement varies). The introduced gas supplied from the gas introduction pipe 205 passes around the metal component to be processed, as indicated by the arrow in the figure, and then circulates through the space between the two cylinders 202 and 204 by the action of the stirring fan 203. 206 is a gas exhaust device with a flare, 207 is a thermocouple, 208 is a lid for cooling, and 209 is a fan for cooling. This circulating processing furnace 2 is also called a horizontal gas nitriding furnace, and its structure itself is well known.

[0057] (Overview of metal component S) The metal component S is, for example, stainless steel or heat-resistant steel, and is such as a unison ring or internal crank, which are turbocharger parts for automobiles, or an engine valve for automobiles. However, in the following embodiment, SUS304 sheet metal (50mm x 50mm x 1mm) and SUS301S sheet metal (50mm x 50mm x 1mm) are used.

[0058] (Basic configuration of processing unit 1) As shown in Figure 1, the processing furnace 2 of the processing apparatus 1 of this embodiment is equipped with a furnace opening / closing lid 7 (metal member input mechanism), a stirring fan 8, a stirring fan drive motor 9, an atmospheric gas concentration detection device 3, a nitriding potential controller 4, a programmable logic controller 31, and a furnace introduction gas supply unit 20.

[0059] The stirring fan 8 is located inside the processing furnace 2 and rotates within the furnace 2 to agitate the atmosphere inside the furnace 2. The stirring fan drive motor 9 is connected to the stirring fan 8 and rotates the stirring fan 8 at a desired rotational speed.

[0060] The atmospheric gas concentration detection device 3 is composed of a sensor capable of detecting the hydrogen concentration or ammonia concentration inside the processing furnace 2 as the furnace atmospheric gas concentration. The detection body of the sensor is in communication with the inside of the processing furnace 2 via the atmospheric gas detection pipe 12. In this embodiment, the atmospheric gas detection pipe 12 is formed as a path that directly connects the sensor body of the atmospheric gas concentration detection device 3 and the processing furnace 2, and is connected to the furnace gas waste pipe 40 which leads to the exhaust gas combustion decomposition device 41. As a result, the atmospheric gas is divided into gas to be waste and gas to be supplied to the atmospheric gas concentration detection device 3.

[0061] Furthermore, the atmospheric gas concentration detection device 3, after detecting the atmospheric gas concentration inside the furnace, outputs an information signal including the detected concentration to the nitride potential controller 4.

[0062] The nitriding potential controller 4 includes a furnace nitriding potential calculation device 13 and a gas flow rate output adjustment device 30. The programmable logic controller 31 includes a gas introduction amount control device 14 and a parameter setting device 15.

[0063] The furnace nitriding potential calculation device 13 calculates the nitriding potential in the processing furnace 2 based on the hydrogen concentration or ammonia concentration detected by the atmospheric gas concentration detection device 3. Specifically, it incorporates a calculation formula for the nitriding potential programmed according to the actual gas introduced into the furnace, and calculates the nitriding potential from the value of the atmospheric gas concentration inside the furnace.

[0064] The parameter setting device 15 consists of, for example, a touch panel, and allows the user to set and input the total flow rate of the gas introduced into the furnace, the type of gas, the processing temperature, the target nitriding potential, and so on. The set parameter values ​​are transmitted to the gas flow rate output adjustment device 30.

[0065] The gas flow rate output adjustment device 30 uses the nitriding potential calculated by the in-furnace nitriding potential calculation device 13 as its output value, the target nitriding potential (set nitriding potential) as its target value, and performs control using the respective introduction amounts of ammonia gas and ammonia decomposition gas as input values. More specifically, for example, it is possible to perform control by keeping the total flow rate of ammonia gas and ammonia decomposition gas introduction constant and changing the introduction ratio between them. The output value of the gas flow rate output adjustment device 30 is transmitted to the gas introduction amount control device 14.

[0066] The gas introduction rate control device 14 sends control signals to the first supply rate control device 22 for ammonia gas (specifically a mass flow controller) and the second supply rate control device 26 for ammonia decomposition gas (specifically a mass flow controller), respectively, in order to achieve the introduction rate of each gas.

[0067] The furnace introduction gas supply unit 20 of this embodiment includes a first furnace introduction gas supply unit 21 for ammonia gas, a first supply amount control device 22, and a first supply valve 23. Furthermore, the furnace introduction gas supply unit 20 of this embodiment includes a second furnace introduction gas supply unit 25 for ammonia decomposition gas (AX gas), a second supply amount control device 26, and a second supply valve 27.

[0068] In this embodiment, ammonia gas and ammonia decomposition gas are mixed in the furnace introduction gas introduction pipe 29 before entering the processing furnace 2.

[0069] The first in-furnace gas supply unit 21 is formed by a tank filled with, for example, the first in-furnace gas (ammonia gas in this example).

[0070] The first supply amount control device 22 is formed by a mass flow controller and is interposed between the first in-furnace gas supply unit 21 and the first supply valve 23. The opening degree of the first supply amount control device 22 changes according to the control signal output from the gas supply amount control device 14. The first supply amount control device 22 also detects the amount of gas supplied from the first in-furnace gas supply unit 21 to the first supply valve 23 and outputs an information signal including this detected supply amount to the gas supply amount control device 14. This control signal can be used to correct the control by the gas supply amount control device 14, etc.

[0071] The first supply valve 23 is formed by a solenoid valve that switches between open and closed states in accordance with a control signal output by the gas introduction amount control device 14, and is located downstream of the first supply amount control device 22.

[0072] The second in-furnace gas supply unit 25 is formed, for example, by a tank filled with the second in-furnace gas (ammonia decomposition gas in this example). Alternatively, the second in-furnace gas supply unit 25 may be piping installed from a pyrolysis furnace that generates ammonia decomposition gas by pyrolyzing ammonia gas.

[0073] The second supply amount control device 26 is formed by a mass flow controller and is interposed between the second in-furnace gas supply unit 25 and the second supply valve 27. The opening degree of the second supply amount control device 26 changes according to the control signal output from the gas supply amount control device 14. The second supply amount control device 26 also detects the amount of gas supplied from the second in-furnace gas supply unit 25 to the second supply valve 27 and outputs an information signal including this detected supply amount to the gas supply amount control device 14. This control signal can be used to correct the control by the gas supply amount control device 14, etc.

[0074] The second supply valve 27 is formed by a solenoid valve that switches between open and closed states in accordance with a control signal output by the gas introduction amount control device 14, and is located downstream of the second supply amount control device 26.

[0075] In this embodiment, the processing apparatus 1 is configured to introduce a first furnace introduction gas (ammonia gas) and a second furnace introduction gas (ammonia decomposition gas) into the processing furnace 2 as an activation atmosphere gas in order to activate the surface of the metal member S as a pretreatment for nitriding. Furthermore, during this pretreatment, the activation atmosphere gas in the processing furnace 2 can be heated to a first temperature (a specific example will be described later, but for example, 350°C to 550°C) by a heater 201h.

[0076] Furthermore, the processing apparatus 1 of this embodiment is configured to introduce a first furnace introduction gas (ammonia gas) and a second furnace introduction gas (AX gas) into the processing furnace 2 while providing feedback control to nitride the surface of the metal member S after the pretreatment. In addition, during the pretreatment, the nitriding atmosphere gas in the processing furnace 2 can be heated to a second temperature (a specific example will be described later, but for example, 520°C to 650°C) by heater 201h.

[0077] (New features of processing unit 1) A novel feature of the processing apparatus 1 of this embodiment is that it is equipped with an organic solvent injection device 300 that intermittently introduces a liquid organic solvent multiple times into the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe).

[0078] The organic solvent injection device 300 includes a tank 301 filled with an organic solvent (specific examples will be described later), an organic solvent injection pipe 302 extending from the container 301 into the furnace introduction gas introduction pipe 29, a pump 303 provided in the middle of the organic solvent injection pipe 302 to send the organic solvent in the container 301 toward the furnace introduction gas introduction pipe 29, and a check valve 304 provided downstream of the pump 303.

[0079] Pump 303 is designed to deliver a predetermined amount of organic solvent (e.g., 0 to 100 ml) at a predetermined discharge rate (e.g., 0 to 5000 ml / min) intermittently multiple times at predetermined intervals (e.g., 0 to 120 minutes) toward the furnace introduction gas introduction pipe 29.

[0080] The operating conditions of such a pump 303 are controlled by the organic solvent input control device 305. Specifically, in this embodiment, the organic solvent is added at a rate of approximately uniform speed in amounts of 10 to 80 ml per batch over 1 second to 2 minutes (preferably 10 to 2 minutes), and is added 2 to 6 times with intervals of 10 minutes or more between batches.

[0081] The tip of the organic solvent inlet pipe 302 (for example, a cylindrical pipe with a diameter of 3 mm) penetrates the wall of the furnace introduction gas introduction pipe 29 (for example, a cylindrical pipe with a diameter of 27 mm) at approximately a right angle and extends into the furnace introduction gas introduction pipe 29 (for example, protruding approximately 300 mm toward the central axis (the dimensions shown as an example may vary depending on the size of the processing furnace 2)). The furnace introduction gas introduction pipe 29 extends into the processing furnace 2 and its tip is an inclined surface (an inclined surface of approximately 45°) (the shorter end is downward and the tip is upward), while the tip of the organic solvent inlet pipe 302 is cut by a plane perpendicular to the axis of the organic solvent inlet pipe 302.

[0082] The check valve 304 is a general-purpose check valve for liquid media. In this embodiment, since the risk of the liquid organic solvent undesirably vaporizing is extremely small, no special specifications are required.

[0083] (Operation of processing device 1: Pre-treatment) Next, the operation of the processing apparatus 1 of this embodiment will be described. First, the metal member S to be processed is introduced horizontally into the circulating processing furnace 2 via the furnace opening / closing lid 7 (metal member input mechanism). Then, the circulating processing furnace 2 is heated by the heater 201h.

[0084] Subsequently, ammonia gas and ammonia decomposition gas are introduced into the processing furnace 2 at a set flow rate as activated atmosphere gases via the furnace introduction gas supply unit 20 and the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe). This set flow rate can be set and input using the parameter setting device 15 and is controlled by the first supply amount control device 22 (mass flow controller) and the second supply amount control device 26 (mass flow controller). In addition, the stirring fan drive motor 9 is driven to rotate the stirring fan 8, stirring the atmosphere inside the processing furnace 2.

[0085] Meanwhile, the organic solvent injection device 300 intermittently injects liquid organic solvent multiple times into the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe) while the activated atmosphere gas (ammonia gas and ammonia decomposition gas) is being continuously introduced into the processing furnace 2. Here, the conditions for introducing the organic solvent by the organic solvent injection device 300 can be set and input in the parameter setting device 15 and are controlled by the pump 303.

[0086] The liquid organic solvent introduced into the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe) reaches the processing furnace 2 while remaining in liquid state, being pushed out by the activated atmosphere gas (ammonia gas and ammonia decomposition gas). There, it vaporizes and is thermally decomposed in the processing furnace 2.

[0087] The surface of the metal component S can be activated by the above pretreatment. Specifically, if the organic solvent is a compound containing at least one hydrocarbon, the HCN produced in the reaction process starting from the thermal decomposition of the organic solvent reduces the passivation film on the surface of the metal component S, effectively activating the surface. Alternatively, if the organic solvent is a compound containing at least one chlorine, the HCl produced in the reaction process starting from the thermal decomposition of the organic solvent reduces the passivation film on the surface of the metal component S, effectively activating the surface.

[0088] In particular, because the organic solvent is added intermittently multiple times, additional organic solvent is added during the pretreatment process, significantly enhancing the effect of the organic solvent and thus significantly increasing the surface activation effect of the metal component S.

[0089] (Operation of treatment device 1: Nitriding treatment) Subsequently, the circulating processing furnace 2 is heated to the desired nitriding temperature by the heater 201h. Meanwhile, in this embodiment, the introduction of the activated atmosphere gas (ammonia gas and ammonia decomposition gas) into the processing furnace 2 is continued as the introduction of the nitriding atmosphere gas (the type of gas is continued, but the amount introduced may be changed). Specifically, a mixed gas of ammonia gas and ammonia decomposition gas is introduced into the processing furnace 2 from the furnace introduction gas supply unit 20 at the initial flow rate set for the nitriding treatment. This initial flow rate can also be set and input in the parameter setting device 15 and is controlled by the first supply amount control device 22 and the second supply amount control device 26 (both mass flow controllers). In addition, the stirring fan drive motor 9 is driven to rotate the stirring fan 8 and stir the atmosphere inside the processing furnace 2.

[0090] The furnace nitriding potential calculation device 13 of the nitriding potential controller 4 calculates the nitriding potential inside the furnace (initially it is an extremely high value (because there is no hydrogen inside the furnace), but it decreases as the decomposition of ammonia gas (hydrogen generation) progresses), and determines whether it has fallen below the sum of the target nitriding potential and the reference deviation value. This reference deviation value can also be set and input using the parameter setting device 15.

[0091] If the calculated value of the furnace nitriding potential is determined to be below the sum of the target nitriding potential and the reference deviation value, the nitriding potential controller 4 starts controlling the amount of gas introduced into the furnace via the gas introduction amount control device 14.

[0092] The furnace nitriding potential calculation device 13 of the nitriding potential controller 4 calculates the furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal. The gas flow rate output adjustment device 30 then uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, the target nitriding potential (set nitriding potential) as the target value, and the amount of introduced gas into the furnace as the input value to perform PID control. Specifically, in this PID control, for example, control is performed to change the introduction ratio of the amount of introduced ammonia gas and the amount of introduced ammonia decomposition gas while keeping the total flow rate of both constant. In this PID control, each setting parameter value set and input in the parameter setting device 15 is used. These setting parameter values ​​are, for example, different values ​​depending on the value of the target nitriding potential.

[0093] Then, the gas flow rate output adjustment device 30 controls the amount of each gas introduced into the furnace as a result of PID control. Specifically, the gas flow rate output adjustment device 30 determines the flow rate of each gas, and this output value is transmitted to the gas introduction amount control device 14.

[0094] The gas introduction rate control device 14 sends control signals to the first supply rate control device 22 for ammonia gas and the second supply rate control device 26 for ammonia decomposition gas, respectively, in order to achieve the introduction rate of each gas.

[0095] Through the control described above, the furnace nitriding potential can be stably controlled to be near the target nitriding potential. This makes it possible to perform nitriding treatment on the surface of the metal component S with extremely high quality.

[0096] (Specific examples) The practical effects of adding the following six types of organic solvents were verified using the apparatus 1 of this embodiment. Formamide, xylene, and toluene are examples of compounds in liquid state that contain hydrocarbons. Trichloroethylene, tetrachloroethylene, and tetrachloroethane are examples of compounds in liquid state that contain chlorine.

[0097] [Table 1] TIFF0007875601000002.tif40168

[0098] As metal component S, five sheets each of SUS316 (50mm x 50mm x 1mm) and SUS310S (50mm x 50mm x 1mm) were inserted, each in a vertical orientation.

[0099] The pretreatment temperature was set to 420°C, and the set flow rates of ammonia gas and ammonia decomposition gas introduced as the activation atmosphere gas were set to 35 L / min (constant) and 5 L / min (constant), respectively. The pretreatment duration was set to 1 hour, and the organic solvent was added in four batches of 20 ml each, at a nearly uniform rate over 1 minute, with 14-minute intervals between additions. The first addition of the organic solvent was initiated when the temperature inside the treatment furnace 2 reached 420°C, and the pretreatment was terminated 14 minutes after the completion of the fourth addition of the organic solvent (see Figure 3).

[0100] The nitriding temperature was set to 580°C, the initial flow rate of the ammonia gas introduced as the nitriding atmosphere gas was set to 17 L / min, and the initial flow rate of the ammonia decomposition gas introduced as the nitriding atmosphere gas was set to 23 L / min. The duration of the nitriding treatment was set to 5 hours, the target nitriding potential was set to 1.5, and the flow rate of the nitriding atmosphere gas introduced was feedback controlled.

[0101] Subsequently, the processing furnace 2 (and metal component S) was cooled using a cooling lid 208 and a cooling fan 209 (see Figure 2).

[0102] The thickness of the nitrided layer formed on the surface of the metal component S was measured by observing the vicinity of the surface of the cut metal component S with an optical microscope. The average values ​​of these measurements are shown in the table below.

[0103] [Table 2] TIFF0007875601000004.tif73166

[0104] Next, as a comparative example, the method of adding the organic solvent was changed to adding 80 ml at a nearly uniform rate over 1 minute in a single step, and the timing of the start of the addition was set to when the temperature inside the processing furnace 2 reached 420°C. All other conditions were the same as in the above example. The thickness of the nitrided layer formed on the surface of the metal member S was measured by observing the vicinity of the surface of the cut metal member S with an optical microscope. The average value of these measurements is shown in the table below.

[0105] [Table 3] TIFF0007875601000006.tif73166

[0106] As shown in Tables 2 and 3, excellent results were observed for SUS316 when all six types of organic solvents were added intermittently multiple times.

[0107] Furthermore, as shown in Tables 2 and 3, excellent effects were observed with SUS310S when three types of organic solvents containing chloride were added intermittently multiple times.

[0108] Furthermore, in the processing apparatus 1 of this embodiment, it is effective to use either a method utilizing HCN (carbon compounds, nitrogen compounds) or a method utilizing HCl (chloride) depending on the grade of the steel (see paragraph 0013).

[0109] (Verification of suitable pretreatment temperature) The ease of nitriding (ease of nitrogen atom penetration) in the subsequent nitriding treatment can differ depending on the pretreatment temperature. For pretreatment temperatures of 300°C to 550°C (first temperature), a SUS316 plate (50mm x 50mm x 1mm) was used as the metal member S, and all other conditions were the same as in the above example. The thickness of the nitrided layer formed on the surface of the metal member S was measured by observing the vicinity of the surface of a cut metal member S with an optical microscope. The average values ​​of these measurements are shown in the table below. As can be seen from the table, a pretreatment temperature in the range of 400°C to 500°C was preferred.

[0110] [Table 4] TIFF0007875601000008.tif47166

[0111] (Effects of processing device 1) According to the processing apparatus 1 of this embodiment as described above, by introducing a liquid organic solvent (in addition to carbon compounds and nitrogen compounds, chlorides are also acceptable) into the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe) while the introduction of activated atmosphere gas (ammonia gas and ammonia decomposition gas) into the processing furnace 2 is being continued, the organic solvent introduction device 300 can effectively suppress the occurrence of the organic solvent vaporizing and flowing back even when the temperature of the processing furnace 2 is high.

[0112] Furthermore, according to the processing apparatus 1 of this embodiment, the organic solvent input device 300 intermittently inputs the organic solvent in liquid form in multiple batches, thereby enabling the input of an appropriate amount of organic solvent at a timing appropriate to the conditions inside the processing furnace 2. As a result, the organic solvent can be additionally added during the pretreatment process, significantly enhancing the effect of adding the organic solvent and thus significantly increasing the surface activation effect of the metal member S. Specifically, by controlling the pump 303, the organic solvent can be added in amounts of 10 to 80 ml at a time, at a substantially uniform rate over 1 to 2 minutes, in 2 to 6 batches with intervals of 10 minutes or more.

[0113] Furthermore, according to the processing apparatus 1 of this embodiment, the organic solvent injection device 300 has a check valve 304 on the upstream side of the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe). This prevents backflow of the organic solvent and enables more precise injection of the appropriate amount of organic solvent.

[0114] Furthermore, according to the processing apparatus 1 of this embodiment, the metal member S is moved in and out of the processing furnace 2 horizontally through the furnace opening / closing lid 7. As a result, even if precipitation of organic solvent occurs, the risk of contact between the precipitate and the metal member S is relatively small.

[0115] In the processing apparatus 1 of this embodiment, the pretreatment temperature (first heating temperature) is preferably set within the range of 400°C to 500°C. According to this temperature range, the activation treatment of the metal member S proceeds smoothly, while the occurrence of the organic solvent vaporizing and flowing back is effectively suppressed.

[0116] In the apparatus 1 of this embodiment, for example, the activating atmosphere gas may include ammonia gas, and the organic solvent may be a compound containing at least one hydrocarbon. In this case, the HCN produced in the reaction process, which begins with the thermal decomposition of the organic solvent, can reduce the passivation film on the surface of the metal member S and effectively activate the surface. More specifically, for example, the organic solvent may be one of formamide, xylene, and toluene. In these cases, the inventors have confirmed in an actual production furnace that it is effective to add the organic solvent in amounts of 10 to 80 ml at a time over a period of 1 to 2 minutes at a substantially uniform rate, 2 to 6 times with an interval of 10 minutes or more between additions.

[0117] Furthermore, in the apparatus 1 of this embodiment, for example, the activation atmosphere gas may include ammonia gas, and the organic solvent may be a compound containing at least one type of chlorine. In this case, the HCl produced in the reaction process, which begins with the thermal decomposition of the organic solvent, can reduce the passivation film on the surface of the metal member S and effectively activate the surface. More specifically, for example, the organic solvent may be one of trichloroethylene, tetrachloroethylene, and tetrachloroethane. In these cases, the inventors have confirmed in an actual production furnace that it is effective to add the organic solvent in amounts of 10 to 80 ml at a time, at a substantially uniform rate over 1 second to 2 minutes, 2 to 6 times with intervals of 10 minutes or more.

[0118] (Modified version of processing device 1) Figure 4 is a schematic diagram of a modified version of the processing apparatus 1. As shown in Figure 4, in this modified version, a dehumidifier 331 is provided upstream of the first supply amount control device 22 for ammonia gas (one example in the middle of the atmosphere gas introduction piping), and a dehumidifier 335 is provided upstream of the second supply amount control device 26 for ammonia decomposition gas (one example in the middle of the atmosphere gas introduction piping). If the second in-furnace gas supply section 25 is piping provided from a pyrolysis furnace that pyrolyzes ammonia gas to produce ammonia decomposition gas, a dehumidifier may be provided upstream of the pyrolysis furnace (the ammonia gas, which is the raw material for ammonia decomposition gas, is dehumidified). Furthermore, if the ammonia gas that has been dehumidified by the dehumidifier upstream of the first supply amount control device 22 is distributed and supplied to the pyrolysis furnace, then one dehumidifier is sufficient.

[0119] According to this method, performance degradation of the metal component S due to moisture contained in the activated atmosphere gas (ammonia gas and ammonia decomposition gas) can be effectively prevented. (According to the inventor's knowledge, if the moisture content is high, circular stains may appear on the metal component S after nitriding treatment (impairing its appearance). See Figure 5.)

[0120] Furthermore, Figure 6 is a schematic diagram of a further modified version of the processing unit 1. In the modified version shown in Figure 6, two processing units 1' and 1'' are configured to work in conjunction.

[0121] The first processing apparatus 1' is used for activation processing, and compared to the aforementioned processing apparatus 1, the atmospheric gas detection piping 12, the atmospheric gas concentration detection device 3, and the furnace nitriding potential calculation device 13 may be omitted.

[0122] The second treatment apparatus 1" is used for nitriding treatment, and the organic solvent input apparatus 300 may be omitted compared to the aforementioned treatment apparatus 1.

[0123] Furthermore, in this modified example, a mobile furnace 400 (vacuum furnace or atmosphere furnace) for transporting the metal member S that has been pre-treated by the first processing device 1' to the second processing device 1'' is provided so as to be movable from the area near the furnace opening / closing lid 7 of the first processing device 1' to the area near the furnace opening / closing lid 7 of the second processing device 1''.

[0124] In addition, as shown in Figure 6, the first in-furnace gas supply unit 21 (tank) for ammonia gas and the second in-furnace gas supply unit 25 (tank or piping) for ammonia gas decomposition gas are common to the two processing units 1' and 1''.

[0125] According to this modified version, since the activation treatment is carried out in the processing furnace 2 of the first processing apparatus 1', and the nitriding treatment is carried out in a separate processing furnace 2 of the second processing apparatus 1'', there is absolutely no risk of organic solvent precipitation during the nitriding treatment in the processing furnace 2 of the second processing apparatus 1''.

[0126] Furthermore, according to this modified configuration, the nitriding treatment in the processing furnace 2 of the second processing apparatus 1" and the activation treatment of the next metal member S in the processing furnace 2 of the first processing apparatus 1' can be performed simultaneously, thus increasing productivity.

[0127] [Second Embodiment] Figure 7 is a schematic diagram of a metal member processing apparatus 501 (soft nitriding processing apparatus) according to a second embodiment of the present invention. As shown in Figure 7, the processing apparatus 501 of this embodiment also has a circulating processing furnace 2 similar to the processing apparatus 1 of the first embodiment, but uses three types of gases introduced into the circulating processing furnace 2: ammonia, ammonia decomposition gas, and carbon dioxide.

[0128] Specifically, in the processing apparatus 501 of this embodiment, the furnace introduction gas supply unit 520 is further equipped with a third furnace introduction gas supply unit 561 for carbon dioxide, a third supply amount control device 562, and a third supply valve 563.

[0129] The third in-furnace gas supply unit 561 is formed by, for example, a tank filled with the third in-furnace gas (carbon dioxide in this example).

[0130] The third supply amount control device 562 is also formed by a mass flow controller and is interposed between the third in-furnace gas supply unit 561 and the third supply valve 563. The opening degree of the third supply amount control device 562 changes according to the control signal output from the gas supply amount control device 14. The third supply amount control device 562 also detects the amount of gas supplied from the third in-furnace gas supply unit 561 to the third supply valve 563 and outputs an information signal including this detected supply amount to the gas supply amount control device 14. This control signal can be used to correct the control by the gas supply amount control device 14, etc.

[0131] The third supply valve 563 is formed by a solenoid valve that switches between open and closed states in accordance with a control signal output by the gas introduction amount control device 14, and is located downstream of the third supply amount control device 562.

[0132] In this embodiment, the ammonia gas, ammonia decomposition gas, and carbon dioxide are mixed in the furnace introduction gas introduction pipe 29 before entering the processing furnace 2.

[0133] The gas flow rate output adjustment device 30 uses the nitriding potential calculated by the in-furnace nitriding potential calculation device 13 of the nitriding potential controller 4 as its output value, the target nitriding potential (set nitriding potential) as its target value, and performs control using the respective introduction amounts of ammonia gas and ammonia decomposition gas as input values ​​(the introduction amount of carbon dioxide gas is kept constant). More specifically, for example, it is possible to perform control by keeping the total flow rate of the introduction amount of ammonia gas and the introduction amount of ammonia decomposition gas constant and changing the introduction ratio of each. The output value of the gas flow rate output adjustment device 30 is transmitted to the gas introduction amount control device 14.

[0134] The gas introduction rate control device 14 sends control signals to the first supply rate control device 22 for ammonia gas (specifically a mass flow controller), the second supply rate control device 26 for ammonia decomposition gas (specifically a mass flow controller), and the third supply rate control device 562 for carbon dioxide gas (specifically a mass flow controller), respectively, in order to achieve the introduction rate of each gas.

[0135] Furthermore, in the processing apparatus 501 of this embodiment, as a pretreatment for soft nitriding, a first furnace introduction gas (ammonia gas) and a second furnace introduction gas (ammonia decomposition gas) can be introduced into the processing furnace 2 as an activation atmosphere gas to activate the surface of the metal member S. During this pretreatment, the heater 201h can heat the activation atmosphere gas in the processing furnace 2 to a first temperature (a specific example will be described later, but for example, 350°C to 550°C).

[0136] Furthermore, in this embodiment, the processing apparatus 1, after the pretreatment, is capable of introducing the first furnace-introduced gas (ammonia gas) and the second furnace-introduced gas (AX gas) into the processing furnace 2 as a soft nitriding atmosphere gas, while controlling the amount of the third furnace-introduced gas (carbon dioxide gas) to a constant level, and using feedback control (variation control). In addition, during this pretreatment, the nitriding atmosphere gas in the processing furnace 2 can be heated to a second temperature (a specific example will be described later, but for example, 520°C to 650°C) by heater 201h.

[0137] The other configurations of the processing apparatus 501 in this embodiment are substantially the same as those of the processing apparatus 1 in the first embodiment. In Figure 7, the same reference numerals are used for parts that are the same as in the first embodiment. Furthermore, detailed descriptions of parts that are the same as in the first embodiment of this embodiment are omitted.

[0138] (Overview of metal component S) The metal member S subjected to soft nitriding treatment in this embodiment is, for example, stainless steel or heat-resistant steel, such as a unison ring or internal crank, which are turbocharger parts for automobiles, or an engine valve for automobiles. In the following embodiment, SUS304 sheet material (50mm x 50mm x 1mm) and SUS301S sheet material (50mm x 50mm x 1mm) are used.

[0139] (Operation of processing device 501: Pretreatment) Next, the operation of the processing apparatus 501 of this embodiment will be described. First, the metal member S to be processed is introduced horizontally into the circulating processing furnace 2 via the furnace opening / closing lid 7 (metal member input mechanism). Then, the circulating processing furnace 2 is heated by the heater 201h.

[0140] Subsequently, ammonia gas and ammonia decomposition gas are introduced into the processing furnace 2 at a set flow rate as activated atmosphere gases from the furnace introduction gas supply unit 520 via the furnace introduction gas introduction piping 29 (atmosphere gas introduction piping). This set flow rate can be set and input using the parameter setting device 15 and is controlled by the first supply amount control device 22 (mass flow controller) and the second supply amount control device 26 (mass flow controller). In addition, the stirring fan drive motor 9 is driven to rotate the stirring fan 8, stirring the atmosphere inside the processing furnace 2.

[0141] Meanwhile, the organic solvent injection device 300 intermittently injects liquid organic solvent multiple times into the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe) while the activated atmosphere gas (ammonia gas and ammonia decomposition gas) is being continuously introduced into the processing furnace 2. Here, the conditions for introducing the organic solvent by the organic solvent injection device 300 can be set and input in the parameter setting device 15 and are controlled by the pump 303.

[0142] The liquid organic solvent introduced into the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe) reaches the processing furnace 2 while remaining in liquid state, being pushed out by the activated atmosphere gas (ammonia gas and ammonia decomposition gas). There, it vaporizes and is thermally decomposed in the processing furnace 2.

[0143] The surface of the metal component S can be activated by the above pretreatment. Specifically, if the organic solvent is a compound containing at least one hydrocarbon, the HCN produced in the reaction process starting from the thermal decomposition of the organic solvent reduces the passivation film on the surface of the metal component S, effectively activating the surface. Alternatively, if the organic solvent is a compound containing at least one chlorine, the HCl produced in the reaction process starting from the thermal decomposition of the organic solvent reduces the passivation film on the surface of the metal component S, effectively activating the surface.

[0144] In particular, because the organic solvent is added intermittently multiple times, additional organic solvent is added during the pretreatment process, significantly enhancing the effect of the organic solvent and thus significantly increasing the surface activation effect of the metal component S.

[0145] (Operation of processing device 501: Soft nitriding treatment) Subsequently, the circulating processing furnace 2 is heated to the desired soft nitriding temperature by the heater 201h. Meanwhile, in this embodiment, the introduction of an activated atmosphere gas into the processing furnace 2 is started. That is, the introduction of ammonia gas and ammonia decomposition gas continues as the introduction of the nitriding atmosphere gas, while the introduction of carbon dioxide gas is started. Specifically, a mixed gas of ammonia gas, ammonia decomposition gas, and carbon dioxide gas is introduced into the processing furnace 2 from the furnace introduction gas supply unit 20 at the initial flow rate set for the soft nitriding treatment. This initial flow rate can also be set and input in the parameter setting device 15 and is controlled by the first supply amount control device 22, the second supply amount control device 26, and the third supply amount control device 562 (all of which are mass flow controllers). In addition, the stirring fan drive motor 9 is driven to rotate the stirring fan 8, stirring the atmosphere inside the processing furnace 2.

[0146] The furnace nitriding potential calculation device 13 of the nitriding potential controller 4 calculates the nitriding potential inside the furnace (initially it is an extremely high value (because there is no hydrogen inside the furnace), but it decreases as the decomposition of ammonia gas (hydrogen generation) progresses), and determines whether it has fallen below the sum of the target nitriding potential and the reference deviation value. This reference deviation value can also be set and input using the parameter setting device 15.

[0147] If the calculated value of the furnace nitriding potential is determined to be below the sum of the target nitriding potential and the reference deviation value, the nitriding potential controller 4 starts controlling the amount of gas introduced into the furnace via the gas introduction amount control device 14.

[0148] The furnace nitriding potential calculation device 13 of the nitriding potential controller 4 calculates the furnace nitriding potential based on the input hydrogen concentration signal or ammonia concentration signal. The gas flow rate output adjustment device 30 then uses the nitriding potential calculated by the furnace nitriding potential calculation device 13 as the output value, the target nitriding potential (set nitriding potential) as the target value, and the amount of introduced gas into the furnace as the input value to perform PID control. Specifically, in this PID control, for example, control is performed to change the introduction ratio of ammonia gas and ammonia decomposition gas while keeping the total amount of introduced ammonia gas and ammonia decomposition gas constant. In this PID control, each setting parameter value set and input in the parameter setting device 15 is used. These setting parameter values ​​are, for example, different values ​​depending on the value of the target nitriding potential.

[0149] Then, the gas flow rate output adjustment device 30 controls the amount of each gas introduced into the furnace as a result of PID control. Specifically, the gas flow rate output adjustment device 30 determines the flow rate of each gas, and this output value is transmitted to the gas introduction amount control device 14.

[0150] The gas introduction rate control device 14 sends control signals to the first supply rate control device 22 for ammonia gas, the second supply rate control device 26 for ammonia decomposition gas, and the third supply rate control device 562 for carbon dioxide gas, respectively, in order to achieve the introduction rate of each gas.

[0151] Through the control described above, the furnace nitriding potential can be stably controlled to be near the target nitriding potential. This makes it possible to perform nitriding treatment on the surface of the metal component S with extremely high quality.

[0152] (Specific examples) The practical effects of adding the six types of organic solvents listed in Table 1 above were verified using the processing apparatus 501 of this embodiment.

[0153] As metal component S, five sheets each of SUS316 (50mm x 50mm x 1mm) and SUS310S (50mm x 50mm x 1mm) were inserted, each in a vertical orientation.

[0154] The pretreatment temperature was set to 420°C, and the set flow rates of ammonia gas and ammonia decomposition gas introduced as the activation atmosphere gas were set to 35 L / min (constant) and 5 L / min (constant), respectively. The pretreatment duration was set to 1 hour, and the organic solvent was added in four batches of 20 ml each, at a nearly uniform rate over 1 minute, with 14-minute intervals between additions. The first addition of the organic solvent was initiated when the temperature inside the treatment furnace 2 reached 420°C, and the pretreatment was terminated 14 minutes after the completion of the fourth addition of the organic solvent (see Figure 3).

[0155] The soft nitriding temperature was set to 580°C, the initial flow rate of the ammonia gas introduced as the soft nitriding atmosphere gas was set to 17 L / min, the initial flow rate of the ammonia decomposition gas introduced as the soft nitriding atmosphere gas was set to 23 L / min, and the constant flow rate of the carbon dioxide gas introduced as the soft nitriding atmosphere gas was set to 2 L / min. The soft nitriding treatment was performed for 5 hours, the target nitriding potential was set to 1.5, and the flow rate of the soft nitriding atmosphere gases was feedback controlled.

[0156] Subsequently, the processing furnace 2 (and metal component S) was cooled using a cooling lid 208 and a cooling fan 209 (see Figure 2).

[0157] The thickness of the soft nitride layer formed on the surface of the metal component S was measured by observing the vicinity of the surface of the cut metal component S with an optical microscope. The average values ​​of these measurements are shown in the table below.

[0158] [Table 5] TIFF0007875601000010.tif98166

[0159] Next, as a comparative example, the method of adding the organic solvent was changed to adding 80 ml at a nearly uniform rate over 1 minute in a single step, and the timing of the start of the addition was set to when the temperature inside the processing furnace 2 reached 420°C. All other conditions were the same as in the above example. The thickness of the soft nitride layer formed on the surface of the metal member S was measured by observing the vicinity of the surface of the cut metal member S with an optical microscope. The average value of these measurements is shown in the table below.

[0160] [Table 6] TIFF0007875601000012.tif95168

[0161] As shown in Tables 5 and 6, excellent results were observed for SUS316 when all six types of organic solvents were added intermittently multiple times.

[0162] Furthermore, as shown in Tables 5 and 6, excellent effects were observed with SUS310S when three types of organic solvents containing chloride were added intermittently multiple times.

[0163] Furthermore, in the processing apparatus 501 of this embodiment, it is effective to use either a method utilizing HCN (carbon compounds, nitrogen compounds) or a method utilizing HCl (chloride) depending on the grade of the steel (see paragraph 0013).

[0164] (Effects of the processing device 501) With the processing apparatus 501 of this embodiment as described above, even if the temperature of the processing furnace 2 is high, the organic solvent injection device 300 can effectively suppress the occurrence of the organic solvent vaporizing and flowing back into the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe) while the introduction of activated atmosphere gas (ammonia gas and ammonia decomposition gas) into the processing furnace 2 is being continued, by introducing a liquid organic solvent (in addition to carbon compounds and nitrogen compounds, chlorides are also acceptable) into the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe).

[0165] Furthermore, with the processing apparatus 501 of this embodiment, the organic solvent input device 300 intermittently inputs the organic solvent in liquid form in multiple batches, thereby enabling the input of the appropriate amount of organic solvent at a timing appropriate to the conditions inside the processing furnace 2. As a result, the organic solvent can be additionally added during the pretreatment process, significantly enhancing the effect of adding the organic solvent and thus significantly increasing the surface activation effect of the metal member S. Specifically, by controlling the pump 303, the organic solvent can be added in amounts of 10 to 80 ml at a time, at a substantially uniform rate over 1 to 2 minutes, in 2 to 6 batches with intervals of 10 minutes or more.

[0166] Furthermore, in the processing apparatus 501 of this embodiment, the organic solvent injection device 300 also has a check valve 304 on the upstream side of the furnace introduction gas introduction pipe 29 (atmosphere gas introduction pipe). This prevents backflow of the organic solvent and enables more precise injection of the appropriate amount of organic solvent.

[0167] Furthermore, in the processing apparatus 501 of this embodiment, the metal member S is moved in and out of the processing furnace 2 horizontally via the furnace opening / closing lid 7. As a result, even if precipitation of organic solvent occurs, the risk of contact between the precipitate and the metal member S is relatively small.

[0168] In the processing apparatus 501 of this embodiment, the pretreatment temperature (first heating temperature) is preferably set within the range of 400°C to 500°C. This temperature range allows the activation treatment of the metal member S to proceed smoothly while effectively suppressing the occurrence of the organic solvent vaporizing and flowing back.

[0169] In the apparatus 501 of this embodiment, for example, the activating atmosphere gas may include ammonia gas, and the organic solvent may be a compound containing at least one hydrocarbon. In this case, the HCN produced in the reaction process starting from the thermal decomposition of the organic solvent can reduce the passivation film on the surface of the metal member S and effectively activate the surface. More specifically, for example, the organic solvent may be one of formamide, xylene, and toluene. In these cases, the inventors have confirmed in an actual production furnace that it is effective to add the organic solvent in amounts of 10 to 80 ml at a time over a period of 1 to 2 seconds at a substantially uniform rate, 2 to 6 times with an interval of 10 minutes or more.

[0170] Furthermore, in the apparatus 501 of this embodiment, for example, the activating atmosphere gas may include ammonia gas, and the organic solvent may be a compound containing at least one type of chlorine. In this case, the HCl produced in the reaction process starting from the thermal decomposition of the organic solvent can reduce the passivation film on the surface of the metal member S, thereby effectively activating the surface. More specifically, for example, the organic solvent may be one of trichloroethylene, tetrachloroethylene, or tetrachloroethane. In these cases, the inventors have confirmed in an actual production furnace that it is effective to add the organic solvent in amounts of 10 to 80 ml at a time over a period of 1 to 2 minutes at a substantially uniform rate, 2 to 6 times with intervals of 10 minutes or more.

[0171] (Modified version of the processing device 501) Figure 8 is a schematic diagram of a modified version of the processing apparatus 501. As shown in Figure 8, in this modified version, a dehumidifier 331 is provided upstream of the first supply amount control device 22 for ammonia gas (one example in the middle of the atmosphere gas introduction piping), and a dehumidifier 335 is provided upstream of the second supply amount control device 26 for ammonia decomposition gas (one example in the middle of the atmosphere gas introduction piping). If the second in-furnace gas supply section 25 is piping provided from a pyrolysis furnace that pyrolyzes ammonia gas to produce ammonia decomposition gas, a dehumidifier may be provided upstream of the pyrolysis furnace (the ammonia gas, which is the raw material for ammonia decomposition gas, is dehumidified). Furthermore, if the ammonia gas that has been dehumidified by the dehumidifier upstream of the first supply amount control device 22 is distributed and supplied to the pyrolysis furnace, then one dehumidifier is sufficient.

[0172] According to this method, performance degradation of the metal component S due to moisture contained in the activated atmosphere gas (ammonia gas and ammonia decomposition gas) can be effectively prevented. (According to the inventor's knowledge, if the moisture content is high, circular stains may appear on the metal component S after soft nitriding treatment (impairing its appearance). See Figure 5.)

[0173] Figure 9 is a schematic diagram of a further modified version of the processing unit 501. In the modified version shown in Figure 9, two processing units 501' and 501'' work in conjunction with each other.

[0174] The first processing apparatus 501' is used for activation processing, and compared to the aforementioned processing apparatus 501, the atmosphere gas detection piping 12, the atmosphere gas concentration detection device 3, the furnace nitriding potential calculation device 13, the third supply amount control device 562, and the third supply valve 563 may be omitted.

[0175] The second treatment apparatus 501" is used for soft nitriding treatment, and the organic solvent feeding apparatus 300 can be omitted compared to the aforementioned treatment apparatus 501.

[0176] Furthermore, in this modified example, a mobile furnace 400 (vacuum furnace or atmosphere furnace) for transporting the metal member S that has been pre-treated by the first processing device 501' to the second processing device 501'' is provided so as to be movable from the area near the furnace opening / closing lid 7 of the first processing device 501' to the area near the furnace opening / closing lid 7 of the second processing device 501''.

[0177] In addition, as shown in Figure 9, the first in-furnace gas supply unit 21 (tank) for ammonia gas and the second in-furnace gas supply unit 25 (tank or piping) for ammonia gas decomposition gas are common to the two treatment devices 501' and 501''.

[0178] According to this modified version, since the activation treatment is carried out by the processing furnace 2 of the first processing apparatus 501', and the soft nitriding treatment is carried out by another processing furnace 2 of the second processing apparatus 501”, there is absolutely no risk of organic solvent precipitation during the soft nitriding treatment in the processing furnace 2 of the second processing apparatus 501”.

[0179] Furthermore, according to this modified configuration, the soft nitriding treatment in the processing furnace 2 of the second processing apparatus 501" and the activation treatment of the next metal member S in the processing furnace 2 of the first processing apparatus 501' can be carried out simultaneously, thus increasing productivity. The claims at the time of filing are as follows: [Claim 1] A method for processing metal components using a processing furnace, A metal component input step in which metal components are placed into the processing furnace, The process includes an activated atmosphere gas introduction step in which an activated atmosphere gas is introduced into the processing furnace, A first heating step in which the activated atmosphere gas in the processing furnace is heated to a first temperature, After the first heating step, a main atmosphere gas introduction step is performed in which a nitriding atmosphere gas or a soft nitriding atmosphere gas is introduced into the processing furnace, A second heating step is performed to heat the nitriding atmosphere gas or soft nitriding atmosphere gas in the processing furnace to a second temperature in order to nitride or soft nitride the metal member, Equipped with, In the activation atmosphere gas introduction step, the activation atmosphere gas is introduced into the processing furnace via the activation atmosphere gas introduction piping. During at least a portion of the first heating step, the activated atmosphere gas introduction step is performed simultaneously. During the aforementioned period, a liquid organic solvent is intermittently introduced multiple times into the activated atmosphere gas introduction piping. A processing method characterized by the following. [Claim 2] The first heating temperature is 400°C to 500°C. The processing method according to feature 1. [Claim 3] The aforementioned activated atmosphere gas contains ammonia gas. The organic solvent is a compound containing at least one hydrocarbon. The processing method according to claim 1 or 2. [Claim 4] The organic solvent is one of formamide, xylene, and toluene. The processing method according to feature 3. [Claim 5] The organic solvent is added in amounts of 10 to 80 ml at a time, at a nearly uniform rate over 1 second to 2 minutes, and added 2 to 6 times with intervals of 10 minutes or more between additions. The processing method according to claim 3 or 4. [Claim 6] The aforementioned activated atmosphere gas contains ammonia gas. The organic solvent is a compound containing at least one type of chlorine. The processing method according to either claim 1 or 2. [Claim 7] The organic solvent is one of trichloroethylene, tetrachloroethylene, and tetrachloroethane. The processing method according to feature 6. [Claim 8] The organic solvent is added in amounts of 10 to 80 ml at a time, at a nearly uniform rate over 1 second to 2 minutes, and added 2 to 6 times with intervals of 10 minutes or more between additions. The processing method according to feature 7. [Claim 9] A method for processing metal components using a processing furnace, A metal component input step in which metal components are placed into the processing furnace, The process includes an activated atmosphere gas introduction step in which an activated atmosphere gas is introduced into the processing furnace, A first heating step in which the activated atmosphere gas in the processing furnace is heated to a first temperature, After the first heating step, a main atmosphere gas introduction step is performed in which a nitriding atmosphere gas or a soft nitriding atmosphere gas is introduced into the processing furnace, A second heating step is performed to heat the nitriding atmosphere gas or soft nitriding atmosphere gas in the processing furnace to a second temperature in order to nitride or soft nitride the metal member, Equipped with, During the first heating step, a liquid organic solvent is intermittently introduced into the processing furnace multiple times. A processing method characterized by the following. [Claim 10] Processing furnace and A metal member feeding mechanism for feeding metal members into the aforementioned processing furnace, An atmospheric gas introduction pipe is provided so as to be in communication with the processing furnace and introduces atmospheric gas into the processing furnace, An organic solvent feeding device that intermittently introduces a liquid organic solvent multiple times into the aforementioned atmospheric gas introduction piping, A heating device for heating the atmospheric gas inside the processing furnace to a predetermined temperature, A metal processing apparatus characterized by comprising: [Claim 11] The organic solvent injection device has a check valve on the upstream side of the atmospheric gas introduction piping. The apparatus according to claim 10. [Claim 12] A dehumidifying device is installed in the middle of the aforementioned atmospheric gas introduction piping. The apparatus according to claim 10 or 11, characterized in that it is a processing apparatus. [Claim 13] The metal member input mechanism is configured to insert and remove the metal member horizontally into and out of the processing furnace. The processing apparatus according to any one of claims 10 to 12. [Claim 14] The aforementioned atmosphere gas is an activated atmosphere gas. A second processing furnace for nitriding or soft nitriding is provided separately from the aforementioned processing furnace. The apparatus according to any one of claims 10 to 13. [Claim 15] Processing furnace and A metal member feeding mechanism for feeding metal members into the aforementioned processing furnace, An atmospheric gas injection pipe is provided so as to be in communication with the processing furnace and introduces atmospheric gas into the processing furnace, An organic solvent feeding device that intermittently feeds liquid organic solvent into the aforementioned processing furnace multiple times, A heating device for heating the atmospheric gas inside the processing furnace to a predetermined temperature, A metal processing apparatus characterized by comprising: [Explanation of symbols]

[0180] 1 Processing Unit 1' First Processing Unit 1” Second Processing Unit 3. Atmospheric gas concentration detection device 4. Nitride Potential Controller 7. Furnace opening / closing lid 8. Agitation fan 9. Stirring fan drive motor 12. Atmosphere gas detection piping 13. In-furnace nitriding potential calculation device 14. Gas introduction volume control device 15 Parameter setting device 20 In-reactor gas supply section 21. Unit 1 of the in-reactor gas supply section 22 First supply amount control device 23. First supply valve 25. Second In-Core Gas Supply Unit 26 Second supply amount control device 27 Second supply valve 29. In-reactor gas introduction piping 30 Gas flow output adjustment device 31 Programmable Logic Controllers 40. In-furnace gas exhaust piping 41 Exhaust gas combustion decomposition unit 201h Heater 202 Cylinder 203 Stirring fan 204 Cylinder 205 Gas inlet pipe 206 Gas exhaust system 208 Lid 209 Fans 300 Organic solvent feeding device 301 Tank 302 Organic solvent input pipe 303 Pump 304 Check valve 305 Organic solvent input control device 331 Dehumidification equipment 335 Dehumidification equipment 400 Mobile Furnaces S Metal component 501 Processing Unit 501' First Processing Unit 501” Second Processing Unit 561 Third In-Core Gas Supply Unit 562 Third supply amount control device 563 Third supply valve

Claims

1. A method for processing metal components using a processing furnace, A metal component input step in which metal components are placed into the processing furnace, The process includes an activated atmosphere gas introduction step in which an activated atmosphere gas is introduced into the processing furnace, A first heating step involves heating the activated atmosphere gas in the processing furnace to a first temperature, After the first heating step, a main atmosphere gas introduction step is performed in which a nitriding atmosphere gas or a soft nitriding atmosphere gas is introduced into the processing furnace. A second heating step is performed to heat the nitriding atmosphere gas or soft nitriding atmosphere gas in the processing furnace to a second temperature in order to nitride or soft nitride the metal member, Equipped with, During the first heating step, a liquid organic solvent is intermittently introduced into the processing furnace multiple times. The aforementioned activated atmosphere gas contains ammonia gas. The organic solvent is a compound containing at least one hydrocarbon. A processing method characterized by the following.

2. The organic solvent is one of formamide, xylene, and toluene. The processing method according to feature 1.

3. A method for processing metal components using a processing furnace, A metal component input step in which metal components are placed into the processing furnace, The process includes an activated atmosphere gas introduction step in which an activated atmosphere gas is introduced into the processing furnace, A first heating step involves heating the activated atmosphere gas in the processing furnace to a first temperature, After the first heating step, a main atmosphere gas introduction step is performed in which a nitriding atmosphere gas or a soft nitriding atmosphere gas is introduced into the processing furnace. A second heating step is performed to heat the nitriding atmosphere gas or soft nitriding atmosphere gas in the processing furnace to a second temperature in order to nitride or soft nitride the metal member, Equipped with, During the first heating step, a liquid organic solvent is intermittently introduced into the processing furnace multiple times. The aforementioned activated atmosphere gas contains ammonia gas. The organic solvent is a compound containing at least one type of chlorine. A processing method characterized by the following.

4. The organic solvent is one of trichloroethylene, tetrachloroethylene, and tetrachloroethane. The processing method according to feature 3.

5. In the activation atmosphere gas introduction step, the activation atmosphere gas is introduced into the processing furnace via the activation atmosphere gas introduction piping. During at least a portion of the first heating step, the activated atmosphere gas introduction step is carried out simultaneously. During the aforementioned period, a liquid organic solvent is intermittently introduced multiple times into the activated atmosphere gas introduction piping. The processing method according to any one of features 1 to 4.

6. The organic solvent is added in amounts of 10 to 80 ml at a time, at a nearly uniform rate over 1 second to 2 minutes, and added 2 to 6 times with intervals of 10 minutes or more between additions. The processing method according to feature 5.

7. The first temperature is 400°C to 500°C. The processing method according to any one of features 1 to 6.

8. Processing furnace and A metal member feeding mechanism for feeding metal members into the aforementioned processing furnace, An atmospheric gas injection pipe is provided so as to be in communication with the processing furnace and introduces atmospheric gas into the processing furnace, An organic solvent feeding device that intermittently feeds liquid organic solvent into the aforementioned processing furnace multiple times, A heating device for heating the atmospheric gas inside the processing furnace to a predetermined temperature, Equipped with, The aforementioned atmosphere gas is an activated atmosphere gas. The aforementioned activated atmosphere gas contains ammonia gas. The organic solvent is a compound containing at least one hydrocarbon. A metal processing apparatus characterized by the following:

9. The organic solvent is one of formamide, xylene, and toluene. The apparatus according to feature 8.

10. Processing furnace and A metal member feeding mechanism for feeding metal members into the aforementioned processing furnace, An atmospheric gas injection pipe is provided so as to be in communication with the processing furnace and introduces atmospheric gas into the processing furnace, An organic solvent feeding device that intermittently feeds liquid organic solvent into the aforementioned processing furnace multiple times, A heating device for heating the atmospheric gas inside the processing furnace to a predetermined temperature, Equipped with, The aforementioned atmosphere gas is an activated atmosphere gas. The aforementioned activated atmosphere gas contains ammonia gas. The organic solvent is a compound containing at least one type of chlorine. A metal processing apparatus characterized by the following:

11. The organic solvent is one of trichloroethylene, tetrachloroethylene, and tetrachloroethane. The apparatus according to the feature described in 10.

12. The organic solvent feeding device is configured to intermittently feed liquid organic solvent into the processing furnace multiple times via the atmospheric gas introduction piping. The processing method according to any one of 8 to 11, characterized by the features described above.

13. The organic solvent injection device has a check valve on the upstream side of the atmospheric gas introduction piping. The apparatus according to any one of 8 to 12, characterized by the following:

14. A dehumidifying device is installed in the middle of the aforementioned atmospheric gas introduction piping. The apparatus according to any one of claims 8 to 13.

15. The metal member input mechanism is configured to insert and remove the metal member horizontally into and out of the processing furnace. The apparatus according to any one of the features 8 to 14.

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