Carburizing apparatus and carburizing method

Abstract

The present invention provides a carburizing apparatus and carburizing method that can suppress the excessive supply of carburizing gas to the carburizing furnace, suppress the pressure drop inside the carburizing furnace, and suppress the increase in the carburizing treatment time. [Solution] The carburizing apparatus according to the present invention comprises a carburizing gas generator for generating carburizing gas, a carburizing furnace that partitions a heating chamber supplied with the carburizing gas from the carburizing gas generator and has a door that can be opened and closed to open and close the heating chamber to the outside, and a gas tank, wherein a portion of the atmospheric gas of the heating chamber can be supplied to and stored in the gas tank, and the atmospheric gas stored in the gas tank can be supplied to the heating chamber.

Description

[Technical Field]

[0001] The present invention relates to a carburizing apparatus and a carburizing method. [Background technology]

[0002] Carburizing furnaces used for carburizing treatment have been known for some time (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-004300 [Patent Document 1] Japanese Patent Publication No. 2024-004304 [Overview of the project] [Problems that the invention aims to solve]

[0004] Heat treatment processes, including carburizing, are very energy-intensive, and measures to reduce their environmental impact are required.

[0005] Current carburizing processes involve generating large quantities of carburizing gas in a carburizing gas generator called a transformation furnace, and supplying that gas to several carburizing furnaces. There is no problem if all the carburizing furnaces supplied with the gas are in operation, but with existing carburizing gas generators, it is difficult to change the amount of carburizing gas generated midway through the process. If there are furnaces that are not in operation, the gas for those furnaces is burned, releasing a large amount of CO2 into the atmosphere.

[0006] Furthermore, during the carburizing process, the door of the carburizing furnace is opened and closed at the time the workpiece is loaded and at the time of quenching, causing a decrease in pressure inside the furnace before and after these operations. Therefore, when the door of the carburizing furnace is opened and closed, it is necessary to supply a large amount of carburizing gas to the furnace to prevent atmospheric air from being drawn in.

[0007] The carburizing gas generator described in Patent Documents 1 and 2 is integrated with the furnace body, so there is little waste and it is a very eco-friendly device from the perspective of CO2 emissions. Also, since the pressure inside the carburizing furnace drops before and after the door of the carburizing furnace is opened and closed, a large amount of carburizing gas is required.

[0008] Here, the inventors have found that carburizing can be performed without supplying such a large amount of carburizing gas at timings other than before and after the door of the carburizing furnace is opened and closed. Therefore, it is conceivable to change the amount of carburizing gas generated midway so that the pressure inside the furnace does not drop before and after the door of the carburizing furnace is opened and closed. However, with existing carburizing gas generators, it is difficult to change the amount of carburizing gas generated midway.

[0009] On the other hand, a method of introducing nitrogen gas at the timing when the pressure inside the carburizing furnace drops to maintain the pressure inside the carburizing furnace is also conceivable. By doing so, it is possible to maintain the furnace pressure and prevent the entrainment of air while suppressing an increase in the amount of carburizing gas generated by the carburizing gas generator. However, in this method, since the atmosphere gas inside the carburizing furnace is diluted with nitrogen, it takes time to stabilize the composition of the atmosphere inside the carburizing furnace to the composition required for carburizing, and there is a problem that the time required for the carburizing process increases.

[0010] An object of the present invention is to provide a carburizing treatment apparatus and a carburizing method that can suppress an excessive supply of carburizing gas to a carburizing furnace, suppress a pressure drop inside the carburizing furnace, and suppress an increase in the time required for the carburizing process.

Means for Solving the Problems

[0011] The carburizing apparatus according to the first aspect of the present invention is (1) a carburizing gas generator that generates carburizing gas, a carburizing furnace that partitions a heating chamber to which the carburizing gas is supplied from the carburizing gas generator and includes a door that can be opened and closed so as to open and close the heating chamber to the outside, and a gas tank, It is a carburizing device that can supply and store a part of the atmospheric gas in the heating chamber to the gas tank, and can supply the atmospheric gas stored in the gas tank to the heating chamber.

[0012] A carburizing device as one embodiment of the present invention (2) It includes a pressure gauge for measuring the pressure in the heating chamber, The carburizing device according to (1) above, wherein the flow rate of the atmospheric gas supplied from the heating chamber to the gas tank can be adjusted according to the measured value of the pressure gauge.

[0013] A carburizing device as one embodiment of the present invention (3) It includes a concentration gauge for measuring the gas concentration of the atmospheric gas in the heating chamber, The carburizing device according to (1) or (2) above, wherein the supply state in which the atmospheric gas is supplied from the heating chamber to the gas tank and the supply stop state in which the atmospheric gas is not supplied from the heating chamber to the gas tank can be switched according to the measured value of the concentration gauge.

[0014] A carburizing device as one embodiment of the present invention (4) The carburizing device according to any one of (1) to (3) above, wherein at least one of the first flow rate, which is the flow rate of the carburizing gas supplied from the carburizing gas generator to the heating chamber, and the second flow rate, which is the flow rate of the atmospheric gas supplied from the gas tank to the heating chamber, can be adjusted so that the total flow rate is not more than a specified flow rate.

[0015] A carburizing method as the second aspect of the present invention (5) A carburizing method using a carburizing device, The carburizing device includes a carburizing gas generator for generating carburizing gas, A carburizing furnace comprising a heating chamber supplied with carburizing gas from the carburizing gas generator, and a door that can be opened and closed to open and close the heating chamber to the outside, Equipped with a gas tank, The carburizing method involves supplying a portion of the atmospheric gas from the heating chamber to the gas tank for storage, and then supplying the atmospheric gas stored in the gas tank to the heating chamber.

[0016] A carburizing method as one embodiment of the present invention is (6) The carburizing apparatus is equipped with a pressure gauge for measuring the pressure in the heating chamber. The carburizing method according to (5) above, wherein the flow rate of the atmospheric gas supplied from the heating chamber to the gas tank is adjusted according to the measurement value of the pressure gauge.

[0017] A carburizing method as one embodiment of the present invention is (7) The carburizing apparatus is equipped with a concentration meter for measuring the gas concentration of the atmospheric gas in the heating chamber. The carburizing method according to (5) or (6) above, which switches between a supply state in which the atmospheric gas is supplied from the heating chamber to the gas tank and a supply stop state in which the atmospheric gas is not supplied from the heating chamber to the gas tank, according to the measurement value of the concentration meter.

[0018] A carburizing method as one embodiment of the present invention is (8) The carburizing method according to any one of (5) to (7) above, wherein the first flow rate, which is the flow rate of the carburizing gas supplied from the carburizing gas generator to the heating chamber, and the second flow rate, which is the flow rate of the atmosphere gas supplied from the gas tank to the heating chamber, are adjusted so that the sum of the first flow rate and the second flow rate is less than or equal to a specified flow rate. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a carburizing apparatus and a carburizing method that can suppress the excessive supply of carburizing gas to the carburizing furnace, suppress the pressure drop inside the carburizing furnace, and suppress the increase in the carburizing treatment time. [Brief explanation of the drawing]

[0020] [Figure 1] This is a diagram illustrating a carburizing apparatus according to one embodiment of the present invention. [Figure 2] Figure 1 shows a flowchart illustrating an example of a carburizing method using the carburizing apparatus. [Figure 3] This diagram shows a carburizing apparatus in which a portion of the atmospheric gas from the heating chamber is supplied to and stored in a gas tank. [Figure 4] This diagram shows a carburizing apparatus with the door open, supplying atmospheric gas stored in the gas tank to the heating chamber. [Figure 5] This figure shows the various measurement results from Example 1. [Figure 6] This figure shows the various measurement results in Comparative Example 1. [Figure 7] This figure shows the various measurement results in Comparative Example 2. [Figure 8] This figure shows the various measurement results in Comparative Example 3. [Modes for carrying out the invention]

[0021] Hereinafter, embodiments of the carburizing apparatus and carburizing method according to the present invention will be illustrated with reference to the drawings. In each figure, identical components are denoted by the same reference numerals.

[0022] <Carburizing apparatus 1> Figure 1 is a schematic diagram showing a carburizing apparatus 1 as one embodiment of the carburizing apparatus according to the present invention. The carburizing apparatus 1 is used to carburize a product X. The product X may be, for example, a basket containing a sample to be carburized.

[0023] As shown in Figure 1, the carburizing apparatus 1 comprises a carburizing gas generator 10, a carburizing furnace 20, a gas tank 30, an extraction line 40, and a supply line 50.

[0024] The carburizing gas generator 10 generates carburizing gas. The carburizing gas includes carbon monoxide gas, hydrogen gas, and an inert gas. Specifically, the carburizing gas generator 10 includes a combustion unit that generates combustion gas by incomplete combustion of a hydrocarbon gas and a combustion-supporting gas, a reforming unit that reforms a portion of the combustion gas into carbon monoxide gas and hydrogen gas, a dilution unit that dilutes the reformed gas with a hydrocarbon gas and an inert gas such as nitrogen gas, and a catalyst unit that heats a metallic catalyst unit by burning the diluted gas with a heater or gas discharged from a carburizing furnace to generate carburizing gas. However, the configuration of the carburizing gas generator 10 is not limited to the configuration of this embodiment, as long as it is capable of generating carburizing gas.

[0025] The carburizing furnace 20 is supplied with carburizing gas from a carburizing gas generator 10 and contains a heating chamber 22 capable of accommodating the processed product X. The carburizing furnace 20 is also equipped with a door 24 that can be opened and closed to open and close the heating chamber 22 to the outside. The heating chamber 22 is opened to the outside when the door 24 is opened (see Figure 4). In this state, the processed product X can be put into and taken out of the heating chamber 22 from the outside. On the other hand, the heating chamber 22 is closed to the outside when the door 24 is closed (see Figures 1 and 3). The specific configuration of the door 24 is not particularly limited, but the door 24 may be configured to open and close by sliding, for example.

[0026] As shown in Figure 1, in the carburizing apparatus 1 of this embodiment, the carburizing gas generator 10 and the carburizing furnace 20 are directly connected without the need for other elements. In other words, the carburizing gas generator 10 and the carburizing furnace 20 are integrated. Therefore, the carburizing gas generated by the carburizing gas generator 10 is supplied directly to the heating chamber 22 without the need for other elements interposed between the carburizing gas generator 10 and the carburizing furnace 20. This improves the overall energy efficiency of the carburizing apparatus 1. However, the configuration of the carburizing apparatus 1 is not limited to that of this embodiment. For example, the carburizing gas generator 10 and the carburizing furnace 20 may be indirectly connected via other elements.

[0027] A pressure gauge 26 is connected to the carburizing furnace 20 to measure the pressure in the heating chamber 22. A concentration meter 28 is also connected to the carburizing furnace 20 to measure the gas concentration of the atmospheric gas in the heating chamber 22. Specifically, the concentration meter 28 in this embodiment measures the gas concentrations of carbon monoxide and hydrogen in the atmospheric gas of the heating chamber 22. However, the concentration meter 28 may be configured to measure the gas concentrations of other gases in addition to carbon monoxide and hydrogen.

[0028] The gas tank 30 is capable of storing gas. The gas tank 30 may be constructed to have heat resistance and pressure resistance. A pressure gauge 32 is connected to the gas tank 30 to measure the pressure inside the gas tank 30. For the sake of explanation, the pressure gauge 26 connected to the carburizing furnace 20 will be referred to as the "carburizing furnace pressure gauge 26," and the pressure gauge connected to the gas tank 30 will be referred to as the "gas tank pressure gauge 32."

[0029] The extraction line 40 connects the carburizing furnace 20 and the gas tank 30. Therefore, in the carburizing apparatus 1, a portion of the atmospheric gas from the heating chamber 22 can be supplied to the gas tank 30 through the extraction line 40.

[0030] The extraction line 40 is equipped with a filter 42, an extraction flow rate adjustment valve 44, a pump 46, and an on / off valve 48. The filter 42 removes impurities such as soot contained in the atmospheric gas discharged from the heating chamber 22. The filter 42 may be, for example, a membrane filter. The extraction flow rate adjustment valve 44 adjusts the flow rate of the atmospheric gas supplied from the heating chamber 22 to the gas tank 30. The extraction flow rate adjustment valve 44 may be, for example, a globe valve, ball valve, gate valve, butterfly valve, etc. The pump 46 pumps the atmospheric gas from the heating chamber 22 to the gas tank 30. The pump 46 may be, for example, a diaphragm pump, etc. The on / off valve 48 opens and closes the extraction line 40. The on / off valve 48 may be, for example, an air-operated valve, a solenoid valve, etc.

[0031] The supply line 50 connects the gas tank 30 and the carburizing furnace 20. Therefore, the carburizing apparatus 1 can supply the atmospheric gas stored in the gas tank 30 to the heating chamber 22 through the supply line 50.

[0032] The supply line 50 is equipped with an on / off valve 52 and a supply flow rate adjustment valve 54. The on / off valve 52 opens and closes the supply line 50. The on / off valve 52 may be, for example, an air-operated valve or a solenoid valve. The supply flow rate adjustment valve 54 adjusts the flow rate of the atmospheric gas supplied from the gas tank 30 to the heating chamber 22. The supply flow rate adjustment valve 54 may be, for example, a globe valve, a ball valve, a gate valve, a butterfly valve, etc. For the sake of explanation, the on / off valve 48 provided in the extraction line 40 will be referred to as the "extraction on / off valve 48," and the on / off valve 52 provided in the supply line 50 will be referred to as the "supply on / off valve 52."

[0033] The carburizing apparatus 1 includes a discharge line 60 that branches off from the extraction line 40. The discharge line 60 branches off from the extraction line 40 at a position between the filter 42 and the extraction flow rate adjustment valve 44. All of the gas discharged from the heating chamber when the atmospheric gas is not recovered into the gas tank 30, and the remaining atmospheric gas when only a portion of the atmospheric gas discharged from the heating chamber is recovered into the gas tank 30, are discharged to the outside of the carburizing apparatus 1 through the discharge line 60. The gas discharged to the outside of the carburizing apparatus 1 through the discharge line 60 is burned and then released into the atmosphere.

[0034] According to the carburizing apparatus 1 with the above configuration, a portion of the atmospheric gas from the heating chamber 22 can be supplied to and stored in the gas tank 30, and the atmospheric gas stored in the gas tank 30 can be supplied to the heating chamber 22. Specifically, according to the carburizing apparatus 1, a portion of the atmospheric gas from the heating chamber 22 can be supplied to and stored in the gas tank 30 through the extraction line 40, and the atmospheric gas stored in the gas tank 30 can be supplied to the heating chamber 22 through the supply line 50. When a portion of the atmospheric gas from the heating chamber 22 is supplied to and stored in the gas tank 30 through the extraction line 40, the extraction valve 48 is in the open state and the supply valve 52 is in the closed state (see Figure 3). Also, when the atmospheric gas stored in the gas tank 30 is supplied to the heating chamber 22 through the supply line 50, the extraction valve 48 is in the closed state and the supply valve 52 is in the open state (see Figure 4).

[0035] Furthermore, the carburizing apparatus 1 allows for adjustment of the flow rate of the atmospheric gas supplied from the heating chamber 22 to the gas tank 30 according to the measurement value of the carburizing furnace pressure gauge 26. Specifically, the flow rate of the atmospheric gas supplied from the heating chamber 22 to the gas tank 30 can be adjusted by operating the extraction flow rate adjustment valve 44 according to the measurement value of the carburizing furnace pressure gauge 26.

[0036] Furthermore, the carburizing apparatus 1 can switch between a supply state in which atmospheric gas is supplied from the heating chamber 22 to the gas tank 30, and a supply stop state in which atmospheric gas is not supplied from the heating chamber 22 to the gas tank 30, according to the measurement value of the concentration meter 28. Specifically, the supply state and the supply stop state can be switched by operating the supply on / off valve 52 to open and close the supply line 50 according to the measurement value of the concentration meter 28.

[0037] Furthermore, the carburizing apparatus 1 allows adjustment of at least one of the first flow rate, which is the flow rate of carburizing gas supplied from the carburizing gas generator 10 to the heating chamber 22, and the second flow rate, which is the flow rate of atmospheric gas supplied from the gas tank 30 to the heating chamber 22, so that the sum of these two flow rates is less than or equal to a specified flow rate. The "specified flow rate" is the gas flow rate determined by the carburizing furnace manufacturer that allows the carburizing furnace 20 to be operated safely. The specified flow rate for the carburizing furnace 10 in this embodiment is 10 Nm³ 3 The flow rate is / h. As described above, in the carburizing apparatus 1 of this embodiment, the carburizing gas generator 10 is integrated with the carburizing furnace 20. Therefore, in the carburizing apparatus 1 of this embodiment, the first flow rate can be adjusted by adjusting the type and flow rate of gas supplied to the carburizing gas generator 10, and by adjusting the amount of carburizing gas generated by the carburizing gas generator 10. In addition, in the carburizing apparatus 1 of this embodiment, the second flow rate can be adjusted by operating the supply flow rate adjustment valve 54. Thus, the carburizing apparatus 1 of this embodiment is configured to allow adjustment of both the first and second flow rates. However, the carburizing apparatus 1 may be configured to allow adjustment of only one of the first or second flow rates.

[0038] Furthermore, if the carburizing gas generator 10 and the carburizing furnace 20 are not integrated but connected via other components, the carburizing apparatus 1 may be equipped with a flow rate adjustment unit between the carburizing gas generator 10 and the carburizing furnace 20 that can adjust the amount of carburizing gas supplied from the carburizing gas generator 10 to the heating chamber 22. In this way, the carburizing apparatus 1 can be configured to allow adjustment of the first flow rate. The flow rate adjustment unit may include, for example, a valve body such as a globe valve, ball valve, gate valve, or butterfly valve.

[0039] <Carburizing Method> Next, a carburizing method as one embodiment of the carburizing method according to the present invention, using the carburizing apparatus 1 described above, will be explained. As shown in Figure 2, the carburizing method of this embodiment includes a seasoning step S1, a product input step S2, a reheating step S3, a preheating step S4, a carburizing step S5, a diffusion step S6, a cooling step S7, a soaking step S8, an oil cooling step S9, and a product removal step S10.

[0040] In the carburizing method of this embodiment, first, a seasoning step S1 is performed. In the seasoning step S1, seasoning is carried out to create an atmosphere for carburizing. Specifically, in the seasoning step S1 of this embodiment, carburizing gas generated by the carburizing gas generator 10 is supplied to the heating chamber 22, and the atmosphere in the heating chamber 22 is adjusted to an atmosphere for carburizing.

[0041] Next, the product loading process S2 is performed. In the product loading process S2, the door 24 of the carburizing furnace 20 is opened (see Figure 4), and the product X is placed into the heating chamber 22. At this time, the opening of the door 24 of the carburizing furnace 20 lowers the pressure and temperature of the heating chamber 22. In addition, the placement of the product X at room temperature into the heating chamber 22 lowers the temperature of the heating chamber 22.

[0042] Next, the reheating process S3 is performed. In the reheating process S3, with the door 24 of the carburizing furnace 20 closed, the temperature of the heating chamber 22, which had decreased in the product loading process S2, is restored to a predetermined temperature.

[0043] Next, the preheating process S4 is performed. In the preheating process S4, the heating chamber 22, which was reheated in the reheating process S3, is maintained at that temperature for a while.

[0044] Next, the carburizing process S5 is performed. In the carburizing process S5, carburizing gas is supplied to the heating chamber 22 from the carburizing gas generator 10 so that the atmosphere in the heating chamber 22 has the desired composition, and this state is maintained for a predetermined time.

[0045] Next, a diffusion process S6 is performed to move the carbon from the surface layer of the treated product X into the interior.

[0046] Next, a cooling step S7 is performed to slightly lower the temperature of the heating chamber 22, and then a soaking step S8 is performed to maintain the temperature of the heating chamber 22 at the temperature lowered in the cooling step S7 for a while.

[0047] Next, the oil cooling process S9 is performed. In the oil cooling process S9, the door 24 of the carburizing furnace 20 is opened (see Figure 4) to quench the processed product X, and the processed product X in the heating chamber 22 is placed into the oil bath. At this time, the temperature and pressure of the heating chamber 22 decrease as the door 24 is opened. In the oil cooling process S9, the processed product X is immersed in the oil bath for about 20 minutes to transform from an austenite structure to a martensitic structure.

[0048] Finally, the door 24 of the carburizing furnace 20 is opened (see Figure 4), and the processed product X is removed from the heating chamber 22 in a process called product removal S10. At this time, the temperature and pressure of the heating chamber 22 decrease as the door 24 is opened.

[0049] As described above, the seasoning process S1, the reheating process S3, the preheating process S4, the carburizing process S5, the diffusion process S6, the cooling process S7, and the soaking process S8 are performed with the door 24 closed (see Figures 1 and 3). On the other hand, the product loading process S2, the oil cooling process S9, and the product removal process S10 are performed with the door 24 open (see Figure 4). When the door 24 is opened, the atmospheric gas in the heating chamber 22 is released to the outside, and the pressure in the heating chamber 22 decreases. If the pressure in the heating chamber 22 decreases too much, the heating chamber 22 will become negative pressure, and there is a risk that air will be drawn into the carburizing furnace 20.

[0050] In contrast, in the carburizing method of this embodiment, a portion of the atmospheric gas in the heating chamber 22 is supplied to a gas tank for storage, and the atmospheric gas stored in the gas tank 30 is supplied to the heating chamber 22. By doing so, it is possible to suppress the excessive supply of carburizing gas to the carburizing furnace 20, suppress the pressure drop inside the carburizing furnace 20 (heating chamber 22), and suppress the increase in the carburizing treatment time.

[0051] Specifically, in the carburizing method of this embodiment, carburizing gas is continuously supplied from the carburizing gas generator 10 to the heating chamber 22 while the seasoning process S1 to the processed product removal process S10 are being executed. Here, the amount of carburizing gas required to be supplied to the heating chamber 22 during normal operation with the door 24 closed is 2 Nm³. 3 However, when the door 24 is open, in order to suppress the pressure drop in the heating chamber 22, gas is supplied to the heating chamber 22 at a specified flow rate (for example, 10 Nm³). 3 It is necessary to supply it at a rate of 10 Nm³ / h. However, it is usually difficult to change the flow rate of the carburizing gas supplied from the carburizing gas generator 10 to the heating chamber 22 midway through. Therefore, conventionally, the gas flow rate is adjusted to match the required gas flow rate when the door 24 is open, and is set to 10 Nm³ whether the door 24 is closed or open. 3 Carburizing gas was supplied from the carburizing gas generator 10 to the heating chamber 22 at a constant flow rate of / h. However, as mentioned above, during normal operation with the door 24 closed, the amount of carburizing gas supplied to the heating chamber 22 was the amount of carburizing gas required for the carburizing process (for example, 2 Nm³). 3 Since only ( / h) is needed, this method had issues from an efficiency standpoint.

[0052] Therefore, in the carburizing method of this embodiment, the flow rate of the carburizing gas supplied from the carburizing gas generator 10 to the heating chamber 22 is set to 2 Nm³. 3 The flow rate is set to / h. Then, when the door 24 is closed, the atmospheric gas from the heating chamber 22 is gradually recovered and stored in the gas tank 30. When the door 24 is open, 8 Nm of gas is released from the gas tank 30 into the heating chamber of the carburizing furnace 20. 3 The atmosphere gas is supplied at a flow rate of / h. As a result, when the door 24 is open, the carburizing furnace 20 receives a total of 10 Nm³ of gas from the carburizing gas generator 10 and the gas tank 30. 3Gas at a flow rate of / h is supplied. That is, in the carburizing method of the present embodiment, the flow rate of the carburizing gas supplied from the carburizing gas generator 10 to the carburizing furnace 20 is smaller than the total flow rate of the gas supplied to the heating chamber 22 when the door 24 is open. More specifically, in the carburizing method of the present embodiment, among the steps of the seasoning step S1 to the workpiece removal step S10, in each of the seasoning step S1, the reheating step S3, the preheating step S4, the carburizing step S5, the diffusion step S6, the cooling step S7, and the soaking step S8, the supply amount of gas to the heating chamber 22 is 2 Nm 3 / h or less, which is the rated flow rate (10 Nm 3 / h) of the carburizing furnace 1, and in each of the workpiece loading step S2, the oil cooling step S9, and the workpiece removal step S10, the supply amount of gas to the heating chamber 22 is 10 Nm 3 / h, which is the rated flow rate of the carburizing furnace 1. By doing so, it is possible to suppress an excessive supply of the carburizing gas from the carburizing gas generator 10 to the carburizing furnace 20 and suppress a pressure drop in the heating chamber 22.

[0053] Further, in the carburizing method of the present embodiment, a part of the atmospheric gas in the heating chamber 22 is stored in the gas tank 30, and the stored atmospheric gas is supplied to the heating chamber 22 again. Therefore, compared with the case of supplying, for example, nitrogen gas or the like to the heating chamber 22 to suppress a pressure drop in the heating chamber 22, the atmospheric gas in the heating chamber 22 is difficult to be diluted. As a result, it is possible to suppress an increase in the time required to stabilize the composition of the atmospheric gas in the carburizing furnace 20 (heating chamber 22) to the composition required for carburizing, and suppress an increase in the time required for the carburizing process. Furthermore, since the atmosphere in the heating chamber 22 is stabilized, it is possible to perform a carburizing process in which defective products are less likely to occur.

[0054] As described above, in the carburizing method of the present embodiment, carburizing gas is supplied from the carburizing gas generator 10 to the heating chamber 22 at a flow rate of 2 Nm 3 / h, and atmospheric gas is supplied from the gas tank 30 to the heating chamber of the carburizing furnace 20 at a flow rate of 8 Nm 3 / h. However, the specific numerical settings of each flow rate are not limited to the numerical settings of the present embodiment and may be appropriately changed according to the rated flow rate of the carburizing apparatus, the processing conditions of the carburizing process, and the like.

[0055] In the carburizing method of this embodiment, when the door 24 is closed, a portion of the atmospheric gas from the heating chamber 22 is supplied to the gas tank for storage. "When the door 24 is closed, a portion of the atmospheric gas from the heating chamber 22 is supplied to the gas tank for storage" means that a portion of the atmospheric gas from the heating chamber 22 is supplied to the gas tank for storage at any time when the door 24 is closed. In other words, the storage operation of supplying a portion of the atmospheric gas from the heating chamber 22 to the gas tank for storage does not need to be performed at all times when the door 24 is closed. Specifically, this storage operation may be performed only at any time suitable for recovering the atmospheric gas while the seasoning process S1, reheating process S3, preheating process S4, carburizing process S5, diffusion process S6, cooling process S7, and soaking process S8 are being performed. For example, this storage operation may be performed only while the seasoning process S1, preheating process S4, and carburizing process S5 are being performed.

[0056] Furthermore, in the carburizing method of this embodiment, when the door 24 is open, the atmospheric gas stored in the gas tank 30 is supplied to the heating chamber 22. "When the door 24 is open, the atmospheric gas stored in the gas tank 30 is supplied to the heating chamber 22" means that the atmospheric gas stored in the gas tank 30 is supplied to the heating chamber 22 at any time when the door 24 is open. In other words, the supply operation of supplying atmospheric gas from the gas tank 30 to the heating chamber does not need to be performed at all times when the door 24 is open. However, it is preferable that this supply operation is always performed when the door 24 is open to a extent that the processed product X can be put in and taken out of the heating chamber 22. By doing so, a pressure drop in the heating chamber 22 can be reliably suppressed. Moreover, it is even more preferable that this supply operation be performed at all times when the door 24 is open. By doing so, a pressure drop in the heating chamber 22 can be more reliably suppressed.

[0057] Furthermore, in order to more reliably suppress the pressure drop in the heating chamber 22, it is even more preferable to start supplying atmospheric gas from the gas tank 30 to the heating chamber 22 a predetermined time before opening the door 24, and to stop supplying atmospheric gas from the gas tank 30 to the heating chamber 22 after a predetermined time has elapsed after closing the door 24. Specifically, the supply of atmospheric gas from the gas tank 30 to the heating chamber 22 is started a predetermined time before starting the processed product loading process S2, and the supply of atmospheric gas from the gas tank 30 to the heating chamber 22 is stopped after a predetermined time has elapsed after the processed product loading process S2 is completed. Also, the supply of atmospheric gas from the gas tank 30 to the heating chamber 22 is started a predetermined time before starting the oil cooling process S9, and the supply of atmospheric gas from the gas tank 30 to the heating chamber 22 is stopped after a predetermined time has elapsed after the oil cooling process S9 is completed. Furthermore, the supply of atmospheric gas from the gas tank 30 to the heating chamber 22 is started a predetermined time before starting the processed product removal process S10, and the supply of atmospheric gas from the gas tank 30 to the heating chamber 22 is stopped after a predetermined time has elapsed after the processed product removal process S10 is completed. However, in order to suppress the excessive supply of carburizing gas from the carburizing gas generator 10 to the carburizing furnace 20, it is preferable to refrain from supplying atmospheric gas from the gas tank 30 to the heating chamber 22 as much as possible when the door 24 is closed. For this reason, the above predetermined time is preferably 60 seconds, more preferably 30 seconds, and even more preferably 10 seconds.

[0058] In the carburizing method of this embodiment, a portion of the atmospheric gas from the heating chamber 22 is supplied to the gas tank 30 for storage through the extraction line 40. In addition, in the carburizing method of this embodiment, the atmospheric gas stored in the gas tank 30 is supplied to the heating chamber 22 through the supply line 50. When a portion of the atmospheric gas from the heating chamber 22 is supplied to the gas tank 30 for storage through the extraction line 40, the extraction valve 48 is opened and the supply valve 52 is closed (see Figure 3). When the atmospheric gas stored in the gas tank 30 is supplied to the heating chamber 22 through the supply line 50, the extraction valve 48 is closed and the supply valve 52 is open (see Figure 4).

[0059] In the carburizing method of this embodiment, the flow rate of the atmospheric gas supplied from the heating chamber 22 to the gas tank 30 is adjusted according to the measurement value of the carburizing furnace pressure gauge 26. Specifically, the flow rate of the atmospheric gas supplied from the heating chamber 22 to the gas tank 30 is adjusted according to the measurement value of the carburizing furnace pressure gauge 26 so that the flow rate does not cause the pressure in the heating chamber 22 to become negative. In this way, it is possible to suppress the pressure in the heating chamber 22 from becoming negative. More specifically, from the viewpoint of safely operating the carburizing furnace 1, it is preferable to adjust the flow rate of the atmospheric gas supplied from the heating chamber 22 to the gas tank 30 so that the pressure in the heating chamber 22 is 2 Pa or more, more preferably 5 Pa or more, even more preferably 10 Pa or more, even more preferably 30 Pa or more, and even more preferably 50 Pa or more. Furthermore, it is preferable that the flow rate of the atmospheric gas supplied from the heating chamber 22 to the gas tank 30 be less than or equal to the gas flow rate required in each of the following processes: seasoning process S1, reheating process S3, preheating process S4, carburizing process S5, diffusion process S6, cooling process S7, and soaking process S8. In the carburizing method of this embodiment, the flow rate of the atmospheric gas supplied from the heating chamber 22 to the gas tank 30 is adjusted by operating the extraction flow rate adjustment valve 44.

[0060] In the carburizing method of this embodiment, the supply state, in which atmospheric gas is supplied from the heating chamber 22 to the gas tank 30, and the supply stop state, in which atmospheric gas is not supplied from the heating chamber 22 to the gas tank 30, are switched according to the measurement value of the concentration meter 28. In this way, the atmospheric gas in the heating chamber 22 can be stored in the gas tank 30 only when the atmospheric gas has a composition suitable for carburizing. As a result, when atmospheric gas is supplied from the gas tank 30 to the heating chamber 22, the atmospheric gas in the heating chamber 22 is less likely to be diluted, and as a result, the increase in the time required for the carburizing treatment can be further suppressed. Specifically, in the carburizing method of this embodiment, when the carbon monoxide gas concentration and hydrogen gas concentration of the atmospheric gas in the heating chamber 22 measured by the concentration meter 28 are both above a predetermined value, the supply state is set in which atmospheric gas is supplied from the heating chamber 22 to the gas tank 30, and when the carbon monoxide gas concentration and hydrogen gas concentration of the atmospheric gas in the heating chamber 22 measured by the concentration meter 28 are both below a predetermined value, the supply stop state is set in which atmospheric gas is not supplied from the heating chamber 22 to the gas tank 30. The predetermined values ​​for carbon monoxide and hydrogen gas concentrations may be set appropriately depending on the conditions of the carburizing treatment. For example, the predetermined value for carbon monoxide gas concentration may be 15%, and the predetermined value for hydrogen gas concentration may be 30%. In the carburizing method of this embodiment, the supply state and the supply stop state are switched by operating the supply on / off valve 52 to open and close the supply line 50.

[0061] In the carburizing method of this embodiment, at least one of the first flow rate, which is the flow rate of carburizing gas supplied from the carburizing gas generator 10 to the heating chamber 22, and the second flow rate, which is the flow rate of atmospheric gas supplied from the gas tank 30 to the heating chamber 22, is adjusted so that the sum of these two flow rates is less than or equal to a specified flow rate. By doing so, the flow rate of gas supplied to the carburizing furnace 20 can be kept below the specified flow rate, and the carburizing process can be carried out safely. In the carburizing method of this embodiment, when adjusting the first flow rate, the type and flow rate of gas supplied to the carburizing gas generator 10 are adjusted to adjust the amount of carburizing gas generated by the carburizing gas generator 10. In the carburizing method of this embodiment, when adjusting the second flow rate, the supply flow rate adjustment valve 54 is operated. However, the first flow rate is more difficult to adjust than the second flow rate. Therefore, in the carburizing method, it is preferable to adjust only the second flow rate so that the sum of the first and second flow rates is less than or equal to a specified flow rate.

[0062] Furthermore, if the carburizing gas generator 10 and the carburizing furnace 20 are not integrated but are connected via other components, and a flow rate adjustment unit is provided between the carburizing gas generator 10 and the carburizing furnace 20 that can adjust the amount of carburizing gas supplied from the carburizing gas generator 10 to the heating chamber 22, the first flow rate may be adjusted by operating this flow rate adjustment unit. [Examples]

[0063] <Example 1> (Regular flow rate is 10 Nm 3 In a carburizing furnace at / h, 2Nm 3 Gas is supplied at / h, and the recovered gas is used to feed the processed material at 8.0 Nm³. 3 / h supply) The various measurement results for Example 1 are shown in Figure 5. Gas recovery and supply were performed during the carburizing process, which involved a carburizing temperature of 930°C, a carburizing time of 50 minutes, and a CP of 0.8. Gas is supplied from the carburizing gas generator at a rate of 2 Nm³. 3 After supplying 1.2 Nm³ / h and the gas concentration in the carburizing furnace has stabilized, seasoning is performed. 3Gas recovery was performed at a rate of / h. The pressure inside the carburizing furnace at that time was 50 Pa. Gas recovery was carried out for 120 minutes, and the amount of gas recovered was 2.4 Nm³. 3 The gas was recovered. At that time, the gas composition inside the carburizing furnace was 41.5% H2, 20.9% CO, and 0.2% CO2. The gas composition inside the gas tank was equivalent to that inside the carburizing furnace. Next, simultaneously with the input of the processed material, 8.0 Nm of gas was released from the gas tank. 3 Gas at a rate of / h was supplied to the carburizing furnace. Upon gas supply, the pressure inside the carburizing furnace dropped to -100 Pa, but quickly recovered to 350 Pa. At that time, the gas composition inside the carburizing furnace was 37.9% H2, 19.1% CO, and 0.4% CO2. Gas was supplied from the gas tank for 15 minutes. The gas composition inside the carburizing furnace was 41.5% H2, 20.9% CO, and 0.2% CO2. After that, the temperature was restored for about 50 minutes, and then the carburizing treatment was performed simultaneously with 1.2 Nm 3 Gas recovery was performed at a rate of / h. The pressure inside the carburizing furnace at this time was 50 Pa. After the carburizing treatment, the treated product is oil-cooled, and at the same time, 8.0 Nm of gas is supplied from the gas tank. 3 Gas at a rate of / h was supplied to the carburizing furnace. Upon gas supply, the pressure inside the carburizing furnace was -100 Pa, but it quickly recovered to 350 Pa. At that time, the gas composition inside the carburizing furnace was 41.0% H2, 20.7% CO, and 0.2% CO2. Gas was supplied from the gas tank for 5 minutes. Subsequently, the processed material was removed, and at the same time, 8.0 Nm of gas was released from the gas tank. 3 Gas at a rate of / h was supplied to the carburizing furnace. Upon gas supply, the pressure inside the carburizing furnace was -100 Pa, but it quickly recovered to 350 Pa. At that time, the gas composition inside the carburizing furnace was 40.3% H2, 20.4% CO, and 0.2% CO2. Gas was supplied from the gas tank for 5 minutes. The carburizing process was completed without any problems.

[0064] <Comparative Example 1> (Regular flow rate is 10 Nm 3In a carburizing furnace at / h, 10 Nm 3 (supplying / h) The various measurement results for Comparative Example 1 are shown in Figure 6. A carburizing treatment process was carried out at a carburizing temperature of 930°C for 50 minutes, with a CP of 0.8. Gas is supplied from the carburizing gas generator at a rate of 10 Nm³. 3 The gas was supplied at a rate of / h, and seasoning was performed after the gas concentration inside the carburizing furnace stabilized. The pressure inside the carburizing furnace at that time was 350 Pa. The gas composition inside the carburizing furnace at that time was 41.0% H2, 20.8% CO, and 0.2% CO2. When the next material to be processed was added, the pressure inside the carburizing furnace was -100 Pa, but it quickly recovered to 350 Pa. At that time, the gas composition inside the carburizing furnace was 37.9% H2, 19.0% CO, and 0.4% CO2. Afterward, the furnace was reheated for about 50 minutes, followed by carburizing. The pressure inside the carburizing furnace at this time was 350 Pa. After the carburizing treatment, when the treated product was oil-cooled, the pressure inside the carburizing furnace was -100 Pa, but it quickly recovered to 350 Pa. At that time, the gas composition inside the carburizing furnace was 40.1% H2, 20.8% CO, and 0.2% CO2. After the processed material was removed, the pressure inside the carburizing furnace was -100 Pa, but it quickly recovered to 350 Pa. At that time, the gas composition inside the carburizing furnace was 40.3% H2, 20.4% CO, and 0.2% CO2. The carburizing process was completed without any problems, but 10 Nm 3 By continuously supplying at / h, 53Nm was achieved compared to Example 1. 3 I wasted gas.

[0065] <Comparative Example 2 (See Figure 7)> (Regular flow rate is 10 Nm 3 In a carburizing furnace at / h, 2Nm 3 (supplying / h) The various measurement results for Comparative Example 2 are shown in Figure 7. A carburizing treatment process was carried out at a carburizing temperature of 930°C for 50 minutes, with a CP of 0.8. Gas is supplied from the carburizing gas generator at a rate of 2 Nm³. 3The gas was supplied at a rate of / h, and seasoning was performed after the gas concentration inside the carburizing furnace stabilized. The pressure inside the carburizing furnace at that time was 150 Pa. The gas composition inside the carburizing furnace at that time was 41.0% H2, 20.8% CO, and 0.2% CO2. When the next sample was added, the pressure inside the carburizing furnace reached -1000 Pa, and the oxygen concentration inside the furnace increased, so the carburizing process was stopped.

[0066] <Comparative Example 3> (Regular flow rate is 10 Nm 3 In a carburizing furnace with a rate of / h, the gas recovery amount in Example 1 was 1.2 Nm³. 3 (When changed from / h to 1.6Nm3 / h) The various measurement results for Comparative Example 3 are shown in Figure 8. In a carburizing treatment process with a carburizing temperature of 930°C, a carburizing time of 50 minutes, and a CP of 0.8, 8.0 Nm³ of N2 gas was used. 3 We decided to supply it at / h. Gas is supplied from the carburizing gas generator at a rate of 2 Nm³. 3 The gas was supplied at a rate of / h, and seasoning was performed after the gas concentration inside the carburizing furnace stabilized. The pressure inside the carburizing furnace at that time was 50 Pa. The gas composition inside the carburizing furnace at that time was 41.0% H2, 20.7% CO, and 0.2% CO2. Next, simultaneously with the input of the material to be processed, N2 was supplied to the carburizing furnace at a rate of 8.0 Nm3 / h. The gas supply caused the pressure inside the carburizing furnace to drop to -100 Pa, but it quickly recovered to 350 Pa. However, the gas composition inside the carburizing furnace at that time decreased significantly, with H2 at 4.7%, CO at 2.3%, and CO2 at 0.2%. N2 gas was supplied for 15 minutes. After that, the sample was rewarmed for about 50 minutes, but because the concentrations of H2 and CO were low, it was kept warm for another 100 minutes. Subsequently, a carburizing treatment was performed. The pressure inside the carburizing furnace at this time was 50 Pa. After carburizing, the treated product is oil-cooled, and at the same time, 8.0 Nm 3N2 gas at a rate of 0 / h was supplied to the carburizing furnace. Upon gas supply, the pressure inside the carburizing furnace dropped to -100 Pa, but quickly recovered to 350 Pa. At that time, the gas composition inside the carburizing furnace was 7.0% H2, 4.0% CO, and 0.1% CO2. N2 gas was supplied for 5 minutes. Subsequently, the processed material is removed, and at the same time, 8.0 Nm 3 N2 gas was supplied to the carburizing furnace at a rate of 0 / h. The pressure inside the carburizing furnace dropped to -100 Pa upon gas supply, but quickly recovered to 350 Pa. At that time, the gas composition inside the carburizing furnace was 7.1% H2, 3.6% CO, and 0.1% CO2. N2 gas was supplied for 5 minutes. The carburizing process was completed without any problems, but the carburizing time was 120 minutes longer than in Example 1.

[0067] <Comparative Example 4> (In a carburizing furnace with a specified flow rate of 10 Nm3 / h, the amount of gas recovered in Example 1 was 1.2 Nm 3 (When changed from / h to 1.6Nm3 / h) During the carburizing process, which involves a carburizing temperature of 930°C, a carburizing time of 50 minutes, and a CP of 0.8, gas recovery and supply are performed. After supplying gas to the gas generator, seasoning is performed once the gas concentration in the carburizing furnace has stabilized, at 1.6 Nm³. 3 Gas recovery was performed at a rate of / h. At that time, the pressure inside the carburizing furnace decreased to 2 Pa. Due to a significant drop in pressure inside the carburizing furnace, gas recovery was terminated out of concern about an explosion inside the furnace caused by air entrainment. The carburizing process was terminated prematurely due to a drop in furnace pressure.

[0068] The carburizing apparatus and carburizing method according to the present invention are not limited to the specific configurations shown in the embodiments described above, and various modifications, changes, and combinations are possible as long as they do not depart from the scope of the claims. [Industrial applicability]

[0069] The present invention relates to a carburizing apparatus and a carburizing method. [Explanation of Symbols]

[0070] 1: Carburizing apparatus 10: Carburizing gas generator 20: Carburizing furnace 22:Heating chamber 24: Door 26: Carburizing furnace pressure gauge 30: Gas tank 32: Gas tank pressure gauge 40: Extraction line 42: Filter 44: Extraction flow rate adjustment valve 46: Pump 48: Extraction valve 50: Supply Line 52: Supply switch valve 54: Supply flow rate adjustment valve 60: Discharge line S1: Seasoning process S2: Process of introducing processed products S3: Rewarming process S4: Preheating process S5: Carburizing process S6: Diffusion process S7: Temperature cooling process S8: Soaking process S9: Oil cooling process S10: Process for removing processed products X: Processed product

Claims

1. A carburizing gas generator that produces carburizing gas, A carburizing furnace comprising a heating chamber supplied with carburizing gas from the carburizing gas generator, and a door that can be opened and closed to open and close the heating chamber to the outside, Equipped with a gas tank, A carburizing apparatus capable of supplying and storing a portion of the atmospheric gas from the heating chamber to the gas tank, and capable of supplying the atmospheric gas stored in the gas tank to the heating chamber.

2. The heating chamber is equipped with a pressure gauge for measuring the pressure, The carburizing apparatus according to claim 1, wherein the flow rate of the atmospheric gas supplied from the heating chamber to the gas tank can be adjusted according to the measurement value of the pressure gauge.

3. The heating chamber is equipped with a concentration meter for measuring the gas concentration of the atmospheric gas, The carburizing apparatus according to claim 1 or 2, which can switch between a supply state in which the atmospheric gas is supplied from the heating chamber to the gas tank and a supply stop state in which the atmospheric gas is not supplied from the heating chamber to the gas tank, depending on the measurement value of the concentration meter.

4. The carburizing apparatus according to claim 1 or 2, wherein at least one of the first flow rate and the second flow rate can be adjusted so that the sum of the first flow rate, which is the flow rate of the carburizing gas supplied from the carburizing gas generator to the heating chamber, and the second flow rate, which is the flow rate of the atmosphere gas supplied from the gas tank to the heating chamber, is less than or equal to a specified flow rate.

5. A carburizing method using a carburizing apparatus, The carburizing apparatus includes a carburizing gas generator that generates carburizing gas, A carburizing furnace comprising a heating chamber supplied with carburizing gas from the carburizing gas generator, and a door that can be opened and closed to open and close the heating chamber to the outside, Equipped with a gas tank, A carburizing method comprising supplying a portion of the atmospheric gas from the heating chamber to the gas tank for storage, and supplying the atmospheric gas stored in the gas tank to the heating chamber.

6. The carburizing apparatus is equipped with a pressure gauge for measuring the pressure in the heating chamber. The carburizing method according to claim 5, wherein the flow rate of the atmospheric gas supplied from the heating chamber to the gas tank is adjusted according to the measurement value of the pressure gauge.

7. The carburizing apparatus is equipped with a concentration meter for measuring the gas concentration of the atmospheric gas in the heating chamber. The carburizing method according to claim 5 or 6, wherein, in accordance with the measurement value of the concentration meter, the method switches between a supply state in which the atmospheric gas is supplied from the heating chamber to the gas tank and a supply stop state in which the atmospheric gas is not supplied from the heating chamber to the gas tank.

8. The carburizing method according to claim 5 or 6, wherein at least one of the first flow rate, which is the flow rate of the carburizing gas supplied from the carburizing gas generator to the heating chamber, and the second flow rate, which is the flow rate of the atmospheric gas supplied from the gas tank to the heating chamber, is adjusted so that the sum of the first flow rate and the second flow rate is less than or equal to a specified flow rate.

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