Heat treatment furnace

Abstract

The present disclosure aims to provide a structure capable of performing degreasing of a motor core before stress relief annealing without providing a heating device or a vacuum device dedicated to degreasing. A heat treatment furnace of one embodiment of the present disclosure includes a degreasing chamber 14 for degreasing of a motor core, a heating chamber 19 directly communicating with the degreasing chamber and configured to perform annealing of the motor core that has passed through the degreasing chamber using a modified gas generated by a modified gas generation device as an in-furnace atmosphere gas, and a gas flow forming portion GF configured to flow the modified gas of the heating chamber toward the degreasing chamber.

Description

Technical Field

[0001] This disclosure relates to heat treatment furnaces, and more particularly to heat treatment furnaces used in stress-relief annealing of motor cores. Background Technology

[0002] In the past, electromagnetic steel sheets have been used in electrical equipment, such as stationary devices like transformers or rotating devices like motors. For example, the core of a motor is manufactured by using a die to punch non-directional electromagnetic steel sheets of a specified thickness into stator or rotor shapes and then stacking them together.

[0003] However, during the blanking process, at the ends of the core material and in the case of press-fitted layers, residual strain, such as plastic strain and elastic strain, sometimes remains around the press-fitted portion. Therefore, to remove this strain, stress-relief annealing has traditionally been performed: the motor core is heated to approximately 700°C to 800°C in a non-oxidizing atmosphere such as carbon monoxide produced by the incomplete combustion of nitrogen, argon, or butane, and then slowly cooled. This slow cooling is performed to prevent strain in the motor core during cooling, thereby improving iron loss, and to prevent deterioration of its dimensional accuracy. For example, the slow cooling chamber is equipped with all or part of a stirring fan, air cooling pipes, and heaters. A cooling rate of approximately 25°C / hour is recommended for this slow cooling.

[0004] On the other hand, oil is used during the stamping process of the motor core, which then adheres to the surface of the motor core. Therefore, it is preferable to degrease before annealing. Thus, in order to remove the oil components adhering to the surface of the heat-treated object to be annealed, it is proposed to use chemicals, create a vacuum, or heat, for example, to operate a vacuum device or a heating device (see, for example, Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 6-306490

[0008] Patent Document 2: Japanese Patent Application Publication No. 2014-74566

[0009] Patent Document 3: Japanese Patent Application Publication No. 2017-166721 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The inventors conducted in-depth research and discovered a structure that allows for the removal of oil components adhering to the surface of a motor core during processes such as stamping without the need for special heating or vacuum devices, followed by continuous annealing. The object of this disclosure is to provide a structure that enables degreasing of the motor core before stress-relief annealing without requiring a dedicated heating or vacuum device for degreasing.

[0012] Methods for solving problems

[0013] One aspect of this disclosure provides a heat treatment furnace comprising: a degreasing chamber for degreasing a motor core; a heating chamber directly connected to the degreasing chamber, the heating chamber being configured to anneal the motor core having passed through the degreasing chamber using a modified gas generated by a modified gas generating device as the furnace atmosphere gas; and a gas flow forming section configured to cause the modified gas in the heating chamber to flow toward the degreasing chamber.

[0014] According to the heat treatment furnace with the above structure, the modified gas in the heating chamber flows to the degreasing chamber, and the heat of the modified gas can be used to heat the motor core, which is the object to be heat treated, in the degreasing chamber. Therefore, the degreasing of the motor core can be carried out in the degreasing chamber before stress-relief annealing, without the need for a dedicated heating or vacuum device for degreasing.

[0015] Preferably, the gas flow forming section includes: a partition wall that vertically separates at least half of the degreasing chamber, with the lower space of the partition wall directly communicating with the heating chamber and the upper space of the partition wall communicating with the heating chamber via the lower space; an air inlet member that guides air into the upper space; and a gas outlet disposed in the upper space. This structure facilitates the flow of modified gas from the heating chamber from the lower space towards the upper space, and enables further combustion of the modified gas in the upper space.

[0016] Preferably, the plurality of air inlet components are arranged to extend along the transport direction of the motor core, and extend toward the upper space through the space connecting the upper and lower spaces in the partition wall. This structure allows for more appropriate further combustion of the modified gas in the upper space.

[0017] Preferably, a flame curtain forming device is also provided at the upstream end of the degreasing chamber. This structure facilitates the flow of modified gas from the lower space to the upper space.

[0018] Preferably, the degreasing chamber also includes a heat exchanger to which the modified gas generated by the modified gas generating device flows before flowing into the heating chamber. This structure allows the heat from the modified gas generated by the modified gas generating device to be transferred to the gas in the degreasing chamber.

[0019] Preferably, the heat treatment furnace is also equipped with a blower located upstream of the degreasing chamber in the transport direction of the motor core, supplying air towards the motor core. This configuration allows for further degreasing of the motor core via the blower. The blower can be configured to utilize the radiated heat from this side of the heat treatment furnace to generate warm air. This is also excellent in terms of energy efficiency, further promoting degreasing.

[0020] Preferably, the aforementioned heat treatment furnace also has a cooling chamber directly connected to the heating chamber. This cooling chamber is configured to use the modified gas as the furnace atmosphere gas to cool the motor core that has passed through the heating chamber. According to this structure, the motor core that has passed through the heating chamber can be cooled more appropriately.

[0021] Invention Effects

[0022] According to the above-described manner of this disclosure, a heat treatment furnace having the above-described structure is provided, thereby enabling the degreasing of the motor core before stress-relief annealing without the need for a dedicated heating device or vacuum device for degreasing. Attached Figure Description

[0023] Figure 1 This is a schematic structural diagram showing the structure of the heat treatment furnace according to the first embodiment of this disclosure.

[0024] Figure 2 yes Figure 1 A cross-sectional view of the heating chamber of a heat treatment furnace in the direction of transport.

[0025] Figure 3 It is along Figure 2 A cross-sectional view along line III-III.

[0026] Figure 4 It is along Figure 2 A cross-sectional view along line IV-IV.

[0027] Figure 5 It is a graph showing the relationship between the mixing ratio of air and fuel gas and the composition ratio of the modified gas produced when they are burned.

[0028] Figure 6 yes Figure 1 A cross-sectional schematic diagram of the anterior chamber in a heat treatment furnace.

[0029] Figure 7Observed from the upstream side Figure 1 A diagram of the hood of the front chamber in a heat treatment furnace.

[0030] Figure 8 It is shown Figure 1 A flowchart of the process for treating materials in a heat treatment furnace.

[0031] Figure 9 This is a cross-sectional schematic diagram showing a portion of the structure of the heat treatment furnace according to the second embodiment of this disclosure. Detailed Implementation

[0032] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Identical components (or structures) are labeled with the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0033] Figure 1 A schematic structure of the heat treatment furnace 10 according to the first embodiment of this disclosure is shown. In this heat treatment furnace 10, a transfer table 12, a front chamber 14 serving as a degreasing chamber, a first heating chamber 16, a second heating chamber 18, a cooling chamber 20, a rear chamber (outlet chamber) 22, and a transfer table 24 are continuously arranged in the direction in which the heat-treated workpiece W, which serves as a motor core, is transported by the transfer unit (hereinafter referred to as the "transfer direction" or "length direction"). The transfer table 12 is provided with a blower 26 located upstream of the front chamber 14 in the transfer direction of the heat-treated workpiece W, and the blower 26 supplies air to the heat-treated workpiece W on the transfer table 12. In addition, the heating chamber 19 is constructed by having a first heating chamber 16 and a second heating chamber 18, and these heating chambers 16 and 18 can be further integrated into one unit.

[0034] The heat treatment furnace 10 is equipped with a mesh belt conveyor 30 driven by a motor 28 as a transport unit for transporting the heat-treated material W through the heat treatment furnace 10 and along the transport direction. Furthermore, the transport unit is not limited to the mesh belt conveyor 30 and can be configured with various known structures.

[0035] Heating chamber 16 and heating chamber 18, as follows Figure 2 Set up direct connectivity as shown, and respectively as follows: Figure 3 and Figure 4 As shown, it is rectangular in cross-section perpendicular to the transport direction, and is formed to be surrounded by a heat-insulating wall 32 made of ceramic fibers. Figure 3 and Figure 4 As shown, the heat insulation wall 32 is formed by attaching it to the inner surfaces of the two outer walls 34 and the upper and lower outer walls 36, 38, etc. of the heat treatment furnace 1. In addition, the heat insulation wall 32 is not limited to being made of ceramic fiber, for example, it can also be made of heat-resistant brick.

[0036] like Figures 2 to 4 As shown, in the first heating chamber 16 and the second heating chamber 18, multiple crossbeam materials 40 extending in a direction perpendicular to the transport direction (width direction) are mounted on the lower heat insulation wall 32 between the two outer walls 34. Furthermore, multiple longitudinal beam materials 42 extending in the transport direction via the first heating chamber 16 and the second heating chamber 18 are arranged on the crossbeam materials 40. The crossbeam materials 40 and longitudinal beam materials 42 are arranged intersectingly to form a support structure 44. The support structure 44 formed by the intersecting arrangement of the crossbeam materials 40 and longitudinal beam materials 42 supports a mesh belt conveyor 30 from below, which carries the heat-treated material W, which serves as the motor core, as it travels.

[0037] like Figures 1-4 As shown, in the first heating chamber 16 and the second heating chamber 18, multiple heaters 46 extending in the width direction are arranged at intervals below the upper heat insulation wall 32 in the transport direction. Furthermore, regarding the second heating chamber 18, as... Figure 1 , Figure 2 as well as Figure 4 As shown, multiple heaters 46 extending along the width direction are spaced apart in the transport direction above the lower heat insulation wall 32 and below the longitudinal beam material 42. These heaters 46 heat the workpiece W to be heat-treated, performing the prescribed heat treatment.

[0038] The modified gas inlet 48, described later, is located in... Figure 1 One second heating chamber 18 is provided relative to the heating chamber 19, but multiple chambers may be provided instead of just one. Furthermore, it may be provided not only in the second heating chamber 18, but also in the first heating chamber 16, cooling chamber 20, etc. Here, the inlet 48 is located near the downstream end of the second heating chamber 18. The gas flow forming section GF (described later) promotes the flow of the modified gas from the heating chamber 19 toward the front chamber 14, which serves as the degreasing chamber. This provides the modified gas to the second heating chamber 18 in a manner that actively flows upstream from the second heating chamber 18 toward the first heating chamber 16, and then toward the front chamber 14. Furthermore, since the inlet 48 is located near the downstream end of the second heating chamber 18, the modified gas can also be adequately supplied to the adjacent cooling chamber 20 of the second heating chamber 18.

[0039] Additionally, a fire curtain forming device 50 is provided at the upstream end of the front chamber 14, which serves as the degreasing chamber. To suppress the inflow of air from the upstream side of the front chamber 14 into the heating chamber 19, which includes the first heating chamber 16 and the second heating chamber 18, and the front chamber 14, a fire curtain forming device 50 (see reference) is provided as a type of curtain forming device. Figure 1 and Figure 6The front chamber 14 is connected to the cooling chamber 20 via the heating chamber 19, and together with the heating chamber 19 and the cooling chamber 20, forms a passage, i.e., the furnace interior, for transporting the heat-treated material W. The fire curtain forming apparatus 50 has a burner device 50a. The burner device 50a is positioned at the upstream end of the front chamber 14, specifically below the upstream inlet of the front chamber 14. A flame is generated from below the mesh belt conveyor 30 upwards via the burner device 50a, thereby forming a flame-based curtain, i.e., a fire curtain. However, the fire curtain forming apparatus 50 is not limited to this structure and may have other structures. Furthermore, for example, in addition to the structure of forming a curtain of combustion gases, i.e., a fire curtain, as in the fire curtain forming apparatus 50, the curtain forming apparatus may also be configured to use at least a portion of an inert gas and / or nitrogen, thereby forming a gaseous curtain.

[0040] Furthermore, a gas burner 52 for generating modified gas is provided in the first heating chamber 16. This gas burner 52 is substantially the same as the structure already proposed by the inventors (see Patent Documents 2 and 3), therefore, here, according to... Figure 1 , Figure 2 as well as Figure 3 Only a brief overview is provided. Furthermore, here, the gas burner 52 is an example of an atmosphere gas generating device, particularly a modified gas generating device.

[0041] The gas burner 52 is disposed in the first heating chamber 16 below the mesh belt conveyor 30, and has a burner body 54 made of radiant tubes, a supply cylinder 56, an exhaust passage 58 formed around the supply cylinder 56, a raw material gas supply cylinder 60, and a spark rod 62 disposed in the raw material gas supply cylinder 60.

[0042] Pilot feed gas for combustion is supplied to the burner body 54 from the pilot feed gas source 64 via the feed gas supply cylinder 60, and a premixed gas obtained by pre-mixing air and feed gas (i.e., fuel gas) is drawn from the supply cylinder 56 and supplied to the burner body 54. Butane, propane, etc. are used as the feed gas.

[0043] Furthermore, voltage is applied to the spark rod 62, which serves as the ignition unit, using a spark power supply 66 to ignite it, thereby causing the pilot gas to burn within the burner body 54. After combustion is initiated by ignition, combustion is maintained by a premixed gas.

[0044] The heat generated by the gas burner 52 is used to heat the material W to be heat-treated, which is then placed into the first heating chamber 16. The modified gas produced by this combustion passes through the exhaust passage 58, preheats the premixed gas in the preheating section 68, and is then discharged from the gas burner 52. The modified gas thus generated is, for example, a DX gas, which is a pyrogenic modified gas and contains CO, CO2, H2, H2O, and N2 (see reference). Figure 5 ).

[0045] like Figure 1 As shown, the modified gas discharged from the gas burner 52 is supplied to the heating chamber 18 through the inlet 48 via the modified gas supply path 70. A water-cooled heat exchanger 72 and a refrigerated dehydrator 74 are sequentially arranged on the modified gas supply path 70.

[0046] During the process of the modified gas passing through the modified gas supply path 70, the temperature drops to about 40°C in the water-cooled heat exchanger 72, and then drops to about 5°C and is dehydrated in the refrigerated dehydrator 74 before being sent to the second heating chamber 18.

[0047] Furthermore, the first heating chamber 16, the second heating chamber 18, and the cooling chamber 20 are arranged in this order along the transport direction and are interconnected. Therefore, the refrigerated dehydrator 74 can also be connected to the cooling chamber 20 in addition to the second heating chamber 18, so as to provide the modified gas that has been cooled and dehydrated as described above directly from the refrigerated dehydrator 74 to the second heating chamber 18 and the cooling chamber 20.

[0048] Furthermore, the equipment configured in the modified gas supply path 70 is not limited to the water-cooled heat exchanger 72 and the refrigerated dehydrator 74; it may also be configured with equipment corresponding to the desired heat treatment. For example, a CO2 adsorption device may be provided instead of either or both of the water-cooled heat exchanger 72 and the refrigerated dehydrator 74, or a CO2 adsorption device may be provided in addition to the water-cooled heat exchanger 72 and the refrigerated dehydrator 74.

[0049] Furthermore, a modified gas combustion device 76 is provided in the front chamber 14, which is connected to the upstream side of the heating chamber 19 having the first heating chamber 16 and the second heating chamber 18 described above. The gas flow forming section GF is configured to include the modified gas combustion device 76. The gas flow forming section GF is configured to direct the modified gas from the heating chamber 19 toward the front chamber 14, which serves as a degreasing chamber. Figure 6 and Figure 7 As shown, the modified gas combustion device 76 includes a partition wall 78, an air inlet pipe 80, and an exhaust gas outlet 82. The specific structure of the front chamber 14 with the modified gas combustion device 76 will be described below.

[0050] like Figure 6As shown, the interior of the antechamber 14 is vertically divided by a generally horizontal partition wall 78 extending in the transport direction. The partition wall 78 vertically separates at least half of the antechamber 14, specifically at least half downstream in the transport direction, and more specifically at least 70% downstream in the transport direction. By providing the partition wall 78, the antechamber 14 is substantially divided into a space above the partition wall 78 (upper space) 78u and a space below the partition wall 78 (lower space) 78d. The lower space 78d communicates directly with the first heating chamber 16 of the heating chamber 19, and the upper space 78u communicates with the heating chamber 19 via the lower space 78d. Although in Figure 6 Not shown in the figure, but the space 78d below the partition wall 78 becomes the loading chamber 84 equipped with the mesh belt conveyor 30 and is directly connected to the first heating chamber 16.

[0051] The upper space 78u above the partition wall 78 becomes a modified gas combustion chamber 86 surrounded by a ceramic fiber heat insulation wall 32. The front end of the modified gas combustion chamber 86 in the transport direction ( Figure 6 The right end of the chamber is closed, and an exhaust outlet 82 is provided facing upwards. Exhaust gases generated by combustion in the modified gas combustion chamber 86 are discharged from the exhaust outlet 82.

[0052] The upstream end of the transport direction of the anterior chamber 14 becomes the transport inlet 88 for the heat-treated object W, but a [missing information - likely a device or equipment] is installed at this upstream end. Figure 6 and Figure 7 The hood 90 is as shown. The hood 90 is installed on the upper side of the upstream end of the front chamber 14 from the upstream side in the transport direction. An opening (opening portion) 92 is provided in the lower part of the hood 90 for transporting the heat-treated material W into the front chamber 14, and an exhaust portion 94 is formed in the upper part of the hood 90. When the hood 90 is installed, the opening portion 92 divides and forms a part of the transport inlet 88, the opening portion 92 of the hood 90 is located exactly upstream in the transport direction of the lower space 78d, and the exhaust portion 94 of the hood 90 is located exactly upstream in the transport direction of the upper space 78u.

[0053] An exhaust outlet 95 is provided above the exhaust section 94, facing upwards. Additionally, one or more air inlet pipes 80, in this case three, are installed on the front wall 96 of the cover 90, penetrating the exhaust section 94 and extending into the modified gas combustion chamber 86. The air inlet pipes 80 are air inlet components that guide air into the upper space 78u. The multiple air inlet pipes 80 are respectively arranged to extend along the transport direction of the heat-treated material W, which serves as the motor core, and extend towards the upper space 78u through the space 78m in the partition wall 78 connecting the upper space 78u and the lower space 78d. Figure 6 As shown, the front end of each air inlet pipe 80 ( Figure 6The right end of the air inlet pipe 80 extends in the transport direction of the heat treatment furnace 10 to a position downstream of the upstream end of the partition wall 78. However, the front end of the air inlet pipe 80 may also be designed to be located at the same position as the upstream end of the partition wall 78 in the transport direction of the heat treatment furnace 10 or terminate in front of it. The extension length of the front end of the air inlet pipe 80 may be designed to allow for smooth flow of the modified gas from below and above the partition wall 78.

[0054] The gas flow forming section GF is configured as a modified gas combustion device 76 with the above-described structure. Therefore, the modified gas used as the furnace atmosphere gas in the heat treatment furnace 10, particularly in the second heating chamber 18 and the first heating chamber 16, is drawn towards the modified gas combustion chamber 86 in the lower space 78d, thus flowing from the downstream side to the upstream side in the transport direction. Then, this modified gas flows from the base end side (i.e., the upstream side) of the loading chamber 84, which serves as the degreasing chamber, into the modified gas combustion chamber 86 in the upper space 78u, and reacts with the air introduced from the air inlet pipe 80 in the modified gas combustion device 76, thereby undergoing combustion within the modified gas combustion chamber 86. The combusted gas, i.e., the exhaust gas, is then mainly discharged from the exhaust gas outlet 82. The exhaust gas may also be discharged from the exhaust gas outlet 95.

[0055] In addition, purification devices, such as catalyst devices, for purifying and treating exhaust gases can be installed at exhaust gas outlets 82 and 95.

[0056] And, as Figure 6 As shown, the aforementioned burner device 50a is provided below the opening 92 on the lower side of the cover 90. Therefore, the fire curtain generated by the burner device 50a of the fire curtain forming apparatus 50 prevents the modified gas flowing from the downstream side to the upstream side toward the front chamber 14 in the transport direction from being directly discharged from the inlet of the heat treatment furnace 10, and also helps to promote the flow of modified gas from the downstream side.

[0057] The aforementioned blower 26 is also provided. This blower 26 is located upstream of the front chamber 14, which serves as the degreasing chamber, in the transport direction, and blows air towards the heat-treated object W, which is the motor core. The blower 26 is supported on a transport table 12 (not shown) by a support member, which is open instead of forming a passageway like the front chamber 14, the first heating chamber 16, and the second heating chamber 18. The air supplied by the blower 26 can be either ambient temperature air or heated air, but in this case, ambient temperature air is used. Furthermore, from the perspective of improving the degreasing effect on the motor core, the blower 26 could be configured to have a heater and a fan to deliver hot air, but here, from an energy-saving perspective, it is configured to deliver ambient temperature air without a heater. In this case, from the viewpoint of further expecting an auxiliary degreasing effect and energy saving, the blower 26 is more preferably configured to generate warm air by using the heat dissipation heat from the heat treatment furnace 10 side during air supply. This can be achieved, for example, by installing a blower 26 outside the inlet 88 of the heat-treated material W to supply air upstream. Thus, the blower 26 is not limited to being installed on the loading table 12 itself, but can be installed in other locations. Furthermore, for example, a heat exchanger can be installed around the gas burner 52, such as in the exhaust passage 58, the outlet of the heating chamber 19 of the heat treatment furnace 10, or the upstream end of the cooling chamber 20, so that the heat extracted from there can be utilized in the blower 26. The blower 26 is not limited to this structure and can have various configurations. For example, the blower 26 can be integrally installed in the heat treatment furnace 10, or it can be installed in the heat treatment furnace 10 in a removable or movable manner, and it can have various configurations to promote degreasing of the motor core upstream of the front chamber 14.

[0058] Although not shown, the cooling chamber 20 has a cooling unit, such as a water cooling system, to cool the heat-treated material W that has passed through the second heating chamber 18 at a predetermined cooling rate.

[0059] Furthermore, various modifications can be made to the heat treatment furnace 10 with the above-described structure. For example, the following modifications can be made: No partition door is provided between the first heating chamber 16 and the second heating chamber 18, but a partition door may be provided. Similarly, no partition door is provided between the second heating chamber 18 and the cooling chamber 20, but a partition door may be provided.

[0060] As previously described, each heater 46 installed in the first heating chamber 16 and the second heating chamber 18 of the heating chamber 19 is controlled to achieve the corresponding target temperature for the set chamber. In order to control the operation of the heater 46 and / or the gas burner 52, etc., a control device can be provided to control the furnace temperature, furnace atmosphere, etc. to achieve the desired state.

[0061] For the control of the control device, various sensors can be installed in the heat treatment furnace 10. An oxygen sensor capable of measuring oxygen partial pressure can be installed, but other sensors such as a temperature sensor capable of measuring temperature can also be installed. For example, a hydrogen sensor capable of measuring hydrogen partial pressure, a dew point sensor capable of measuring the dew point inside the heat treatment furnace 10, a CO sensor capable of measuring carbon monoxide partial pressure, and a CO2 sensor capable of measuring carbon dioxide partial pressure can also be installed. At this time, the outputs or output signals from the various sensors mentioned above, such as the temperature sensor, are input to the control device, which has a processor (e.g., CPU) and a memory (e.g., ROM, RAM). Based on these inputs from the various sensors, the control device performs calculations according to a predetermined program, thereby outputting operating signals to the heater 46 and / or the gas burner 52, etc.

[0062] In the heat treatment furnace 10, the workpiece W to be heat-treated is placed on the loading table 12, exposed to air from the blower 26, and transported through the inlet opening 92, sequentially passing through the front chamber 14, the first heating chamber 16, the second heating chamber 18, and the cooling chamber 20, exiting from the outlet of the rear chamber 22, and arriving at the unloading table 24. In the heat treatment furnace 10, the downstream of the heating chamber 18 is directly connected to the cooling chamber 20 without a slow cooling chamber. Therefore, the workpiece W to be heat-treated exiting the heating chamber 19, which has the first heating chamber 16 and the second heating chamber 18, is immediately cooled in the cooling chamber 20. In addition, in conventional heat treatment furnaces used for annealing general motor cores, a slow cooling chamber is provided downstream of the heating chamber 18 and upstream of the cooling chamber 20 for slow cooling of the workpiece W; this slow cooling chamber can also be provided in the heat treatment furnace 10.

[0063] Furthermore, the length of the cooling chamber 20 in the longitudinal direction, i.e., the transport direction, can be designed based on the target cooling rate of the heat-treated object W in the cooling chamber 20. Alternatively, the cooling chamber 20 can be constructed by dividing it into multiple cooling sections and connecting these cooling sections along the transport direction.

[0064] In the heat treatment furnace 10, an outlet is provided at the downstream end of the cooling chamber 20. That is, the cooling chamber 20 is connected to the outlet of the heat treatment furnace 10 without a bluing treatment chamber. In other words, in one embodiment of this disclosure, the heat treatment furnace 10 does not continuously perform bluing treatment after stress-relief annealing. However, it is not excluded that a bluing treatment chamber may be provided on the downstream side of the cooling chamber 20. That is, a bluing treatment chamber may also be provided on the downstream side of the cooling chamber 20. Bluing treatment refers to the process of blowing in high dew point gases such as water vapor during the cooling of the annealing furnace to generate an oxide film on the surface of the steel plate. More specifically, it refers to the process of introducing high dew point gases in a treatment chamber at 350°C to 550°C to generate an oxide coating such as iron(II) (FeO) or magnetite (Fe3O4) on the surface of the heat-treated object. In addition, bluing treatment is performed to improve the corrosion resistance and rust prevention of the punched end face. However, by using DX gas containing moisture as the furnace atmosphere gas in the heating chamber 18 to the cooling chamber 20, the same effect as that of the case with bluing treatment can be obtained even without bluing treatment, but a detailed explanation is omitted here.

[0065] Here, the material to be heat-treated, W, will be described. The starting material for the heat-treated material is an electromagnetic steel sheet; in a more specific embodiment, it is a non-directional electromagnetic steel sheet used in the core of a motor (motor core), etc. It can also be a directional electromagnetic steel sheet used in the core of a transformer, etc. The electromagnetic steel sheet is a soft magnetic material, requiring excellent magnetic properties, especially low iron loss.

[0066] Non-directional electromagnetic steel sheets are typically manufactured by a single recrystallization and grain growth process based on continuous annealing after ironmaking, steelmaking, hot rolling, and cold rolling. The manufactured non-directional electromagnetic steel sheets are then subjected to a prescribed punching process, such as stacking multiple sheets in a die to form a laminated material. The electromagnetic steel sheets are stacked by methods such as welding, bonding, and / or pressing. This results in a low-iron-loss motor core, which is then subjected to stress-relief annealing in the heat treatment furnace 10. However, the heat-treated material is not limited to being manufactured by this method. Furthermore, the motor core subjected to heat treatment as described below is not limited to being obtained through such stacking; stacking may not be required.

[0067] Furthermore, there are no particular limitations on the composition of the electromagnetic steel sheet used in the heat treatment furnace of this disclosure and / or in providing the heat treatment method of this disclosure. For example, steel sheets specified in JISC2552, JISC2553, and JISC2555 are preferred. Additionally, there are no particular limitations on the thickness of the electromagnetic steel sheet used.

[0068] In addition, according to Figure 8 The heat treatment method for the above-mentioned heat-treated material in the heat treatment furnace 10 will be described. Figure 8A flowchart illustrating an example of the heat treatment method of this embodiment is shown.

[0069] like Figure 8 As shown, the heat treatment method of this embodiment includes the following steps:

[0070] The first process (step S801) involves degreasing the motor core, which is the object to be heat-treated.

[0071] In the second step (step S803), a modified gas is used as the furnace atmosphere to anneal the motor core that has undergone the first step; and

[0072] In the third step (step S805), a modified gas is used as the furnace atmosphere gas to cool the motor core obtained in the second step at a specified cooling rate.

[0073] The first process (step S801) is the process of degreasing the motor core, i.e., the heat-treated material W, and is called the degreasing process. The first process includes a degreasing process using air supply, i.e., step A (step S801a), and a degreasing process using heating, i.e., step B (step S801b).

[0074] In step A (step S801a), degreasing is promoted by blowing air toward the workpiece W to be heat-treated using a blower 26. This air supply can be either room temperature air or heated air, but room temperature air is used here. The oil used in the stamping process of the motor core is usually a highly volatile oil, so even room temperature air can be expected to achieve a sufficient degreasing effect. For example, the oil adhering to the surface of the motor core will evaporate substantially in 2 to 3 hours if placed at a temperature of 25°C. Furthermore, the blower 26 is supported by a support member (not shown) on the loading table 12, which is open rather than forming a passageway like the front chamber 14, the first heating chamber 16, and the second heating chamber 18. Therefore, the air supply from the blower 26 can be used to allow the oil components adhering to the surface of the workpiece W to evaporate naturally, thereby promoting degreasing.

[0075] In step B (step S801b), the stacked motor core, i.e., the heat-treated material W, is heated in the front chamber 14 at a temperature within a predetermined temperature range (hereinafter, the predetermined first temperature range) to promote degreasing. This first step, including step B, is primarily performed to remove oil components such as stamping oil adhering to the motor core, which is the heat-treated material W. Alternatively, step A may be omitted, and the first step may consist solely of step B. Furthermore, the first step may include a further degreasing step in addition to step B of steps A and B, or both. The first temperature range is a temperature region that does not affect the characteristics of the heat-treated material W, for example, it is set to 500°C or below. The modified gas combustion device 76 of the gas flow forming section is designed to maintain such a temperature in the lower space 78d of the front chamber 14. The first temperature range can be set to 100°C or higher, and preferably 200°C or higher.

[0076] The second step (step S803) is to anneal (heat treat) the stacked motor core in heating chamber 19. During forming processes such as punching and pressing, plastic strain and localized strain in the core caused by residual stress are generated. Therefore, annealing is performed in this second step to remove the strain. In this second step, the motor core is heated to a specified time at the stress-relief annealing temperature, preferably at a homogenization temperature. In the first heating chamber 16, the heating to the homogenization temperature is mainly performed, while in the second heating chamber 18, the homogenization heating treatment is essentially performed. There are no particular limitations on the annealing conditions, but the motor core is typically held at a temperature of approximately 750°C to 850°C for approximately 30 minutes to approximately 2 hours. Thus, the temperature range in the second step (hereinafter, the specified second temperature range) is higher than the aforementioned first temperature range. Furthermore, in the third process described below, the motor core is cooled at a rate exceeding 300°C / hour instead of being cooled slowly. Therefore, the heat treatment in the second process is referred to as annealing or annealing treatment, and the second process is referred to as the annealing process.

[0077] The third step (step S805) is a process in which the motor core, which underwent annealing in the second step, is cooled in the cooling chamber 20 at a predetermined cooling rate that does not constitute quenching, but here at a cooling rate exceeding 300°C per hour. This third step is referred to here as the cooling step. The cooling chamber 20 is configured to be directly connected to the heating chamber 19 on the downstream side of the heating chamber 19, therefore, this third step (cooling step) is performed immediately after the second step (annealing step).

[0078] The cooling rate in the third step can be a rate exceeding 300°C per hour (i.e., 300°C / hour < cooling rate). By achieving a cooling rate exceeding 300°C per hour, the processing time can be shortened. Furthermore, to achieve a cooling rate exceeding 300°C per hour, a forced cooling device (e.g., a forced cooling fan) can be added in addition to a simple cooling unit. Alternatively, the cooling rate can be, for example, below 700°C / hour, below 600°C / hour, or below 500°C / hour. This disclosure does not exclude the possibility of slow cooling in part or all of the third step, such as cooling at a rate of approximately 25°C / hour, or cooling at a rate between 25°C / hour and 300°C / hour.

[0079] Furthermore, the cooling of the motor core in the cooling chamber 20 of the third process at this cooling rate is performed at least at the temperature of the second process (annealing process), preferably within a temperature range of 500°C to 850°C. The aforementioned cooling rate is the average cooling rate within this temperature range. Alternatively, cooling of the motor core at a cooling rate exceeding 300°C / hour can also be performed within a temperature range from the temperature of the second process to 300°C.

[0080] Furthermore, as described above, the heat treatment method of this embodiment does not exclude the above-described processes (see reference 1). Figure 8 In addition to the above, further bluing treatment may be performed. That is, bluing treatment may also be performed after the third process. When bluing treatment is not performed after the third process, the cooling of the motor core at a cooling rate exceeding 300°C / hour can be carried out in the temperature range from the temperature in the second process to 300°C. However, this does not preclude the possibility that when bluing treatment is performed after the third process, the motor core can be cooled at that cooling rate in the temperature range from the temperature in the second process to 300°C, which is lower than 500°C.

[0081] Furthermore, in the degreasing process in step B of the first process, the annealing process in the second process, and the cooling process in the third process, an exothermic modified gas is used as the furnace atmosphere gas. Examples of exothermic modified gases include DX gas. However, the modified gas used in the heat treatment furnace 10 is not limited to DX gas; for example, endothermic modified gases (such as RX gas) are not excluded.

[0082] During cooling in the cooling chamber 20 in the third step, it is preferable that the oxygen partial pressure of the cooling atmosphere in the system within the cooling chamber 20 is above the lower of the oxygen equilibrium partial pressure of 3 / 2Fe + O2 = 1 / 2Fe3O4 and the oxygen equilibrium partial pressure of 2Fe + O2 = 2FeO, and below the oxygen equilibrium partial pressure of 4 / 3Fe + O2 = 2 / 3Fe2O3. This is to properly control the oxidation of the motor core, which can be understood using the Ellingham diagram representing the standard formation free energy of iron oxide. To achieve this atmosphere, the operation of the gas burner 52, which serves as a modified gas generating device, can be controlled.

[0083] The heat treatment furnace 10 with the above-described structure has a front chamber 14, which serves as the degreasing chamber, configured as a gas flow forming section GF with the same structure. This allows the modified gas from the heating chamber 19 to flow from the downstream side to the upstream side, i.e., towards the front chamber 14, in the transport direction. This modified gas is the atmosphere gas used in the annealing of the motor core, and therefore is at a high temperature. Thus, the workpiece W to be heat-treated, which is the motor core, passes through the front chamber 14, thereby undergoing degreasing. In this way, the front chamber 14, serving as the degreasing chamber, does not require a dedicated heating device for degreasing, i.e., a heater or a vacuum device, such as a vacuum pump. Therefore, the heat treatment furnace 10 is highly energy-efficient.

[0084] Furthermore, the front chamber 14, which serves as the degreasing chamber, is connected to the heating chamber 19, thus allowing it to receive radiant heat from the heating chamber 19. Consequently, the heat-treated material W, which serves as the motor core, passes through the front chamber 14, thereby further degreasing the heat-treated material W.

[0085] Furthermore, the front chamber 14, which serves as the degreasing chamber, is configured as a gas flow forming section GF with the aforementioned structure. Therefore, in the modified gas combustion chamber 86 of the front chamber 14, the modified gas reacts with air to produce combustion. Through this combustion, the front chamber 14 is further heated, thereby further promoting the degreasing of the heat-treated material W, which serves as the motor core, in the front chamber.

[0086] Furthermore, the modified gas from the combustion chamber 19 flows from the intake chamber 84 (corresponding to the lower space 78d) of the partition wall 78 of the front chamber 14 to the modified gas combustion chamber 86 (corresponding to its upper space 78u), preferably undergoes combustion and is discharged from the exhaust outlets 82 and 95. Therefore, oil and other substances volatilized in the front chamber 14 will not remain inside the front chamber 14, and flow towards the combustion chamber 19 can also be prevented. Consequently, there is no need to install a dedicated heating or vacuum device for degreasing.

[0087] Furthermore, a blower 26 is installed upstream of the pre-chamber 14. The airflow from the blower 26 further promotes the degreasing of the heat-treated material W, which serves as the motor core, before annealing. As is well known, the blower 26 typically requires less energy than the heater. Even with this blower 26, the heat treatment furnace 10 is superior in energy saving compared to using a dedicated heating device or vacuum device for degreasing.

[0088] Next, according to Figure 9 The heat treatment furnace according to the second embodiment of this disclosure will be described. The heat treatment furnace of the second embodiment differs from the heat treatment furnace 10 of the first embodiment in that it has a structure that allows the heat from the modified gas discharged from the gas burner 52 to be flexibly utilized in the front chamber 14, which serves as a degreasing chamber. Otherwise, it has the same structure as the heat treatment furnace 10. Therefore, only the differences between the heat treatment furnace of the second embodiment and the heat treatment furnace 10 will be described below, and other descriptions will be omitted.

[0089] The modified gas generated in the gas burner 52 has a temperature close to 900°C. In the heat treatment furnace 10 of the first embodiment, the gas is cooled via a water-cooled heat exchanger 72 and a refrigerated dehydrator 74, thereby removing moisture from the gas to a certain extent. To effectively and flexibly utilize the heat dissipation at this time, such as... Figure 9 As shown, heat exchangers 97 and 98 are installed in the anterior chamber 6. Figure 9 This is a sectional view perpendicular to the transport direction of a portion of the antechamber 14. Heat exchangers 97 and 98 are disposed on the wall defining the lower space 78d of the antechamber 14. Figure 1 As shown, the heat treatment furnace in the second embodiment also has two gas burners 52, and therefore two heat exchangers 97 and 98. Here, the modified gas from one gas burner 52 is supplied to one heat exchanger 97, and the modified gas from the other gas burner 52 is supplied to the other heat exchanger 98. However, this does not limit the number of heat exchangers. Furthermore, the number of gas burners and the number of heat exchangers can be different.

[0090] The modified gas supply path 70 is connected to the corresponding gas burner 52 via heat exchangers 97 and 98. Heat exchangers 97 and 98 are respectively installed between the gas burner 52 and the water-cooled heat exchanger 72 in the modified gas supply path 70. Therefore, the heat of the high-temperature modified gas is transferred to the gas in the lower space 78d via heat exchangers 97 and 98, i.e., the modified gas, for heating the modified gas, i.e., degreasing the motor core.

[0091] Thus, the heat treatment furnace according to the second embodiment, having heat exchangers 97 and 98, can utilize the heat of the modified gas before cooling and dehydration in the water-cooled heat exchanger 72 and the refrigerated dehydrator 74 to heat the modified gas in the lower space 78d, i.e., the transfer chamber 84. This allows for more appropriate promotion of degreasing in the front chamber 14. Consequently, the heat treatment furnace of the second embodiment more effectively and flexibly utilizes the heat dissipation of the modified gas, and therefore is superior in energy saving compared to the heat treatment furnace 10 described above.

[0092] The following describes the embodiments.

[0093] (Example 1)

[0094] As an example, multiple motor cores prepared as described above were subjected to the following treatment using a heat treatment furnace having a structure substantially similar to that of the first embodiment described above. This heat treatment furnace has the same structure as the heat treatment furnace 10 described above, except that it does not have a blower 26. Specifically, for each of the prepared motor cores, degreasing was performed in the front chamber 14 (a degreasing chamber) (first step), followed by annealing in the heating chamber 19 (second step), and then cooling in the cooling chamber 20 (third step), thereby performing stress-relief annealing. Furthermore, the heating for degreasing in the front chamber 14 in the first step was performed at a temperature of 200°C to 300°C, which is a predetermined first temperature range, and here at approximately 250°C for a predetermined first time, approximately 10 minutes. Furthermore, in the second process, the heat treatment temperature in the second heating chamber 18 of the heating chamber 19 is set to a temperature of 750°C to 850°C, which is a predetermined second temperature zone higher than the predetermined first temperature zone. In the third process, the cooling rate is set to approximately 350°C per hour within the temperature zone from the heat treatment temperature to 500°C. Additionally, DX gas, which is a heat-generating modified gas, is used as the atmosphere gas. Thus, the motor cores of Examples 1 to 6 are obtained.

[0095] (evaluate)

[0096] The iron loss of the motor core before and after the heat treatment furnace was evaluated as a characteristic feature.

[0097] As a device for measuring the iron loss of motor core, the stator core magnetic characteristic test device "DAC-LST-3" manufactured by Sogen Electric Co., Ltd. was used. The magnetic flux density was set to 1T and the measurement frequency was set to 300Hz for measurement.

[0098] Table 1 shows the iron loss values ​​(W / kg) of the motor cores in Examples 1 to 6 of this invention.

[0099] Table 1

[0100]

[0101] As shown in Table 1, in the embodiment where degreasing is performed in the first step before the second annealing step, the iron loss value decreased during processing in the heat treatment furnace 10, demonstrating a significant improvement. Furthermore, this is consistent with the change in iron loss value when slow cooling occurs after annealing in the heating chamber 19.

[0102] (Example 2)

[0103] In the heat treatment furnace of Example 1, a motor core, which is the object to be heat-treated, was immersed in oil and allowed to flow sequentially from the degreasing chamber to the heating chamber. The changes in the atmospheric gas caused by the volatilization of the oil were investigated. The oil used was "G-6339F" manufactured by Nippon Oil Co., Ltd. This oil (G-6339F) is a very representative working oil, especially widely used as stamping oil for motor cores. Furthermore, in this embodiment, the operation of each heater 16 was controlled such that the first heating chamber 16 and the second heating chamber 18 were maintained at approximately 800°C. Additionally, DX gas, a heat-generating modified gas, was used as the atmospheric gas.

[0104] (evaluate)

[0105] In Example 2, multiple motor cores were used as test pieces, and each motor core was sequentially moved from the degreasing chamber to the heating chamber. The furnace atmosphere 16a in the first heating chamber 16 at this time was collected (refer to...). Figure 2 ) and the furnace atmosphere 18a of the second heating chamber 18 (refer to) Figure 2 The CO2 and CO concentrations in the atmosphere were measured using a CO2 sensor and a CO sensor, respectively, for 16a and 18a.

[0106] The measurement results of CO2 concentration (%) and CO concentration (%) in the furnace atmosphere 16a of the first heating chamber 16 are shown in Table 2. The measurement results of CO2 concentration (%) and CO concentration (%) in the furnace atmosphere 18a of the second heating chamber 18 are shown in Table 3. In Tables 2 and 3, "before treatment" refers to the motor core as the object to be heat-treated before treatment; "during treatment" refers to the motor core being in either the first heating chamber 16 or the second heating chamber 18; and "after treatment" refers to the motor core having passed through this location and a specified time has elapsed. The average of the measurements "before treatment" is set to 1.00, and values ​​equivalent to each measurement based on this value are shown in Tables 2 and 3, respectively.

[0107] Table 2

[0108]

[0109] Table 3

[0110]

[0111] As shown in Tables 2 and 3, the CO2 and CO concentrations during and after the treatment are not significantly different from those before treatment, having approximately the same values. This indicates that the gas flow generated by the gas flow forming section GF from the downstream side to the upstream side in the furnace atmosphere can appropriately generate oil volatilization and maintain the furnace atmosphere in an appropriate state.

[0112] The representative embodiments of this disclosure have been described above, but this disclosure is not limited thereto and various modifications are possible. Various substitutions and modifications can be made as long as they do not depart from the spirit and scope of this disclosure as defined in the claims.

[0113] Label Explanation

[0114] 10: Heat treatment furnace; 14: Front chamber (degreasing chamber); 16: First heating chamber; 18: Second heating chamber; 19: Heating chamber; 20: Cooling chamber; 26: Blower; 76: Modified gas combustion device; 78: Partition wall; 80: Air inlet pipe; 82: Exhaust gas outlet; 86: Modified gas combustion chamber; 95: Exhaust gas outlet; 97, 98: Heat exchangers; GF: Gas flow forming section.

Claims

1. A heat treatment furnace, comprising: Degreasing chamber, used for degreasing motor iron core; A heating chamber, which is directly connected to the degreasing chamber, is configured to use modified gas generated by the modified gas generating device as the furnace atmosphere gas to anneal the motor core that has passed through the degreasing chamber. A conveying unit that conveys the motor core along the conveying direction; and A gas flow forming section is configured to direct the modified gas from the heating chamber toward the degreasing chamber. The conveying unit has a motor-driven mesh belt conveyor that carries the motor core and moves along it. The gas flow forming section has: A partition wall separates at least half of the degreasing chamber vertically, and the lower space of the partition wall becomes a loading chamber equipped with the mesh belt conveyor and is directly connected to the heating chamber, while the upper space of the partition wall is connected to the heating chamber via the lower space. An air inlet component that guides air into the upper space; and A gas outlet is located in the upper space.

2. The heat treatment furnace according to claim 1, wherein, The plurality of air inlet components are respectively arranged to extend along the transport direction of the motor core, and extend toward the upper space through the space in the partition wall that connects the upper space and the lower space.

3. The heat treatment furnace according to claim 1 or 2, wherein, A fire curtain forming device is also provided at the upstream end of the degreasing chamber.

4. The heat treatment furnace according to claim 1 or 2, wherein, The degreasing chamber also has a heat exchanger to which the modified gas generated by the modified gas generating device flows before flowing to the heating chamber.

5. The heat treatment furnace according to claim 1 or 2, wherein, The heat treatment furnace is also equipped with a blower, which is located upstream of the degreasing chamber in the transport direction of the motor core and blows air toward the motor core.

6. The heat treatment furnace according to claim 5, wherein, The blower is configured to generate warm air by using the heat dissipated from the heat treatment furnace side during air supply.

7. The heat treatment furnace according to claim 1 or 2, wherein, The heat treatment furnace also has a cooling chamber that is directly connected to the heating chamber, and the cooling chamber is configured to use the modified gas as the furnace atmosphere gas to cool the motor core that has passed through the heating chamber.

Images