JP6553390B2 - Method of manufacturing nanocrystalline soft magnetic alloy core and heat treatment apparatus - Google Patents

Description

  The present invention relates to a method of manufacturing a nanocrystalline soft magnetic alloy core and a heat treatment apparatus.

  Magnetic cores are widely used in products utilizing electric-magnetic conversion, such as transformers and motors, and are required to have small energy loss due to iron loss. A nanocrystalline soft magnetic alloy is known as one of the materials having a low core loss, and a magnetic core using this nanocrystalline soft magnetic alloy has been proposed. In order to manufacture a magnetic core with a nanocrystalline soft magnetic alloy, it is necessary to heat treat a material such as an amorphous alloy at an appropriate temperature to form a homogeneous nano-level structure and perform nanocrystallization. At this time, even if the temperature in the furnace is set and the material is heated, the material may generate heat due to crystallization, and the material may be heated exceeding the set temperature. In particular, such a situation is likely to occur as the size of the magnetic core increases. As a result, in the manufactured magnetic core, the soft magnetic properties are degraded, which reduces the commercial value.

  In order to avoid this, for example, Patent Document 1 below discloses a method of keeping the surface temperature of the magnetic core at a predetermined temperature by forcibly moving the atmospheric gas in the furnace in the process of heat-treating the material. In addition, as a method of performing uniform temperature rise and cooling on a material, for example, in Patent Document 2 below, after a wound iron core wound and formed with the material is housed in a storage container, a large number of wound iron cores are encased so as to wrap the entire wound iron core. There is disclosed a method of annealing a wound core through metal balls by putting metal balls and heating the storage container in this state.

Patent 3424767 JP-A-6-163294

  However, since the method of Patent Document 1 forcibly moves the atmospheric gas in the furnace, it is necessary to provide the heating furnace with a special mechanism for moving the gas. Furthermore, the material temperature is monitored and the atmospheric gas is moved. There is a problem of increasing the cost of equipment, such as control of timing. In addition, since the heated atmospheric gas is discharged from the outside of the furnace, a part of the energy required for heating in the furnace is wasted, which causes the operating cost of the heating furnace to be increased. Moreover, the method of patent document 2 has only many metal balls in point contact with an iron core, and the heat transfer between an iron core and a metal ball is limited. In addition, since many portions of the iron core surface that are not in contact with the metal sphere remain, heat transfer does not occur at those portions, which is insufficient for temperature control of the material.

  The present invention has been made in view of the above-described circumstances, and the temperature of the material is subjected to the heat treatment of nano-crystallization to develop good soft magnetic characteristics on the magnetic core formed by winding the amorphous alloy ribbon. The method of manufacturing a nanocrystalline soft magnetic alloy core capable of manufacturing a nanocrystalline soft magnetic alloy core having good soft magnetic characteristics, which can be surely suppressed by a simple configuration that the temperature is higher than the heat treatment set temperature, and An object of the present invention is to provide a heat treatment apparatus.

The method for producing a nanocrystalline soft magnetic alloy core according to the present invention is a method for producing a nanocrystalline soft magnetic alloy core having soft magnetic properties, which includes crystal grains having an average grain size of 100 nm or less, and is a sheet-like amorphous alloy . contact and molding the heated body of the core shape in a state wound around the core metal, the heated body formed in a state wound around the core metal, the high covering member thermal conductivity than the amorphous alloy heated body upper surface of the object to be heated in a state, the lower surface, and coating the outer peripheral side surface and a method comprising nanocrystals of an amorphous alloy by heat-treating the object to be heated which is coated with the coating member, only containing, metal core It has a hole and the covering member has a through hole which opens in the same manner as the opening of the hole of the core.

  Moreover, what was formed so that a to-be-heated body could be accommodated was used as a covering member, and the surface of a to-be-heated body may be coat | covered by accommodating a to-be-heated body in a covering member. Moreover, as a covering member, what was formed with the material containing copper may be used. Further, the heat treatment may include performing pre-heat treatment, performing crystallization heat treatment, and performing cooling treatment. Further, the crystallization heat treatment may be performed in a treatment chamber different from the preheat treatment and the cooling treatment. Further, the preheating treatment may be performed for a treatment time longer than the crystallization heat treatment.

The heat treatment apparatus of the present invention is a heat treatment apparatus for producing a nanocrystalline soft magnetic alloy core having soft magnetic properties, including crystal grains having an average crystal grain size of 100 nm or less, and a core for winding a sheet-like amorphous alloy. An upper surface, a lower surface, and an outer peripheral side surface of an object to be heated are covered with gold and an object to be heated, which is formed in a state wound around a core metal, wound on the core metal , and the thermal conductivity is higher than that of an amorphous alloy. A covering member, a first processing chamber for subjecting a heating target coated on the covering member to crystallization heat treatment to nano-crystallize an amorphous alloy, and an covering member disposed adjacent to the first processing chamber and covering the covering member A second processing chamber that performs at least one of preheating and cooling processing on the heating body , the cored bar has a hole, and the covering member opens in the same manner as the opening shape of the hole in the cored bar. It has a through hole .

  Further, the covering member may be formed so as to be able to accommodate the heated object. The covering member may be formed of a material containing copper.

  According to the present invention, the temperature of the material becomes higher than the heat treatment set temperature when the heat treatment of nano-crystallization for expressing good soft magnetic properties is performed on the magnetic core formed by winding the amorphous alloy ribbon. A nanocrystalline soft magnetic alloy core having good soft magnetic properties, which can be reliably suppressed with a simple configuration, can be manufactured.

  When the body to be heated is formed in a state in which a sheet-like amorphous alloy is wound around a core metal and the covering member covers the surface of the portion to be heated excluding the core metal, the core metal is used. Since the object to be heated is covered, the amount of use of the covering member can be reduced. Further, as the covering member, a member formed so as to be able to accommodate the heated object is used, and when the surface of the heated object is covered by accommodating the heated object in the covering member, the heated object is simply accommodated. Coating the object to be heated with the covering member. When the covering member is made of a material containing copper, the thermal conductivity is higher than that of the amorphous alloy, and the heat of the body to be heated can be smoothly transferred. In addition, when the heat treatment includes pre-heat treatment, crystallization heat treatment, and cooling treatment, nanocrystallization of the amorphous alloy can be reliably performed. Further, when the crystallization heat treatment is performed in a treatment chamber different from the preheat treatment and the cooling treatment, the heating temperature for the object to be heated can be easily set. In addition, when the preheating treatment is performed for a treatment time longer than the crystallization heat treatment, the nanocrystallization can be performed uniformly over the entire magnetic core. When the metal core has a hole, the surface area of the metal core is increased, so that the heat of the object to be heated can be smoothly transferred to the metal core.

  According to the heat treatment apparatus of the present invention, a nanocrystalline soft magnetic alloy core having good soft magnetic properties can be efficiently produced.

  Further, when the covering member is formed to be able to accommodate the body to be heated, the covering member can cover the body to be heated by a simple operation such as accommodating the body to be heated. In addition, when the covering member is formed of a material containing copper, the thermal conductivity is higher than that of the amorphous alloy, and the heat of the body to be heated can be moved smoothly.

It is a flowchart which shows an example of the manufacturing method of the nanocrystal soft magnetic alloy magnetic core which concerns on embodiment. (A) is a perspective view which shows an example of a to-be-heated body, (B) is a perspective view which shows the state which notched part about the metal core used for shaping | molding of a to-be-heated body. (A)-(C) is a figure which shows the other example of a core metal, (A) and (B) are a cross-sectional perspective view, (C) is a perspective view. (A) And (B) is a perspective view which shows the other example of a metal core. An example which coat | covered the to-be-heated body with the coating | coated member is shown, (A) is a disassembled perspective view, (B) is a perspective view which shows the state which coat | covered the to-be-heated body. It is a perspective view which shows an example of the coating | coated member formed so that the to-be-heated body could be accommodated. It is a figure which shows an example of preheat processing, crystallization heat processing, and cooling processing. (A) is a figure which shows an example of the heat processing apparatus, (B) is a figure which shows the other example of a heat processing apparatus. It is a graph which shows the result of the iron loss test of the nanocrystal soft magnetic alloy magnetic core of an Example. It is a table | surface which shows an example which compared the case where it heat-treats a to-be-heated body without coat | covering with a coating | coated member, and the case where it coat | covers with the coating | coated member.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to this. Further, in the drawings, in order to describe the embodiment, a part or the whole is schematically described, and a part is described by appropriately changing the scale or the like, for example, describing the part largely or emphasizing. In each of the following drawings, directions in the drawings will be described using an XYZ coordinate system. In this XYZ coordinate system, a plane parallel to the horizontal plane is taken as an XY plane. An arbitrary direction parallel to the XY plane is expressed as an X direction, and a direction orthogonal to the X direction is expressed as a Y direction. Further, a direction (vertical direction) perpendicular to the XY plane is referred to as a Z direction. In each of the X direction, the Y direction, and the Z direction, the direction of the arrow in the figure is the + direction, and the direction opposite to the arrow direction is the − direction.

  The method of manufacturing a nanocrystalline soft magnetic alloy core according to the present embodiment is a method of manufacturing a nanocrystalline soft magnetic alloy core having soft magnetic characteristics, including crystal grains having an average crystal grain size of 100 nm or less, When applying heat treatment of nano-crystallization to express good soft magnetic properties to the magnetic core formed by winding, the temperature of the material is surely suppressed to be higher than the heat treatment setting temperature with a simple configuration, and soft magnetic A nanocrystalline soft magnetic alloy magnetic core with good characteristics can be manufactured.

  FIG. 1 is a flow chart showing an example of a method of manufacturing a nanocrystalline soft magnetic alloy core according to an embodiment. The following description is an example of the manufacturing method and does not limit the manufacturing method. As shown in FIG. 1, the method for manufacturing a nanocrystalline soft magnetic alloy magnetic core according to this embodiment forms a magnetic core-shaped object to be heated from an amorphous alloy (step S1). First, an amorphous alloy is prepared. An amorphous alloy is a metal in an amorphous state, and when heated under predetermined conditions, nanocrystals are formed and good soft magnetic properties are expressed.

  As an amorphous alloy used by this embodiment, the well-known thing used as a material of a nanocrystalline soft-magnetic alloy core can be used arbitrarily. For example, as an amorphous alloy, Fe-Nb-B, Fe-Nb-B-Sn, Fe-B, Fe-Si-B, Fe-Si-B-C, Fe-Si-B- Alloys such as P-based, Fe-Si-B-C-P-based, and Fe-P-B-based can be used. As such an amorphous alloy, for example, an amorphous alloy manufactured in a sheet shape by a liquid rapid cooling method (rapid solidification method) of a single roll method or a twin roll method can be used. When a sheet-like amorphous alloy is used, although the thickness is arbitrary, for example, one having a size of several tens of micrometers to several hundreds of micrometers can be used.

  A core-shaped object to be heated is formed using the above-described amorphous alloy. The shape of the magnetic core of the body to be heated and the method of molding the same are arbitrary. For example, as a forming method, a method of winding and forming a sheet-like amorphous alloy (amorphous alloy thin ribbon) around a core metal, a method of laminating and forming a sheet-like amorphous alloy, and the like can be used. The size of the object to be heated is arbitrarily set according to the size of the transformer or the like used.

  An example of the case where the object to be heated is formed in a state where a sheet-like amorphous alloy is wound around a cored bar will be described below. FIG. 2A is a perspective view showing an example of the heated body 1, and FIG. 2B is a perspective view showing a state where a part of the cored bar 2 used for molding the heated body 1 is cut out. The object to be heated 1 is formed into a rectangular cylindrical shape in which four corners are chamfered by winding the sheet-like amorphous alloy 3 around the core metal 2 a plurality of times as shown in FIG. 2 (A) It is. The cored bar 2 is formed of a metal material containing, for example, iron, nickel, tungsten, etc., and also functions as a covering member 8 (see FIG. 5A) described later. When the forming material of the core metal 2 is a material having a high thermal conductivity, the heat transfer from the body 1 to be heated can be performed more smoothly.

  The shape of the core metal 2 is appropriately determined depending on the shape of the nanocrystalline soft magnetic alloy core to be manufactured, but any shape may be used as long as the sheet-like amorphous alloy 3 can be wound. be able to. For example, as the core metal 2, one having a hole 4 may be used as shown in FIG. 2 (B). Since the hole 4 has a concave portion on the + Z side of the core metal, the cross section of the core metal 2 in the XZ plane and the cross section in the YZ plane are U-shaped. That is, the cored bar 2 has a shape in which the −Z side of the cylindrical part whose corners are chamfered is closed. When the metal core 2 has the hole 4, the surface area is increased, so that the heat from the heated body 1 can be transferred smoothly. Moreover, the core metal 2 shown in FIG. 2 is not limited to opening the + Z side of the hole 4, and for example, the + Z side of the hole 4 may be closed by a lid or the like (not shown). Whether or not the hole 4 is provided in the cored bar 2 is arbitrary. For example, the cored bar 2 may be in a bulk shape.

  The shape, size and number of the holes 4 formed in the core metal 2 are arbitrary. 3A to 3C are diagrams showing another example of the cored bar 2, in which FIGS. 3A and 3B are cross-sectional perspective views, and FIG. 3C is a perspective view. For example, as shown in FIG. 3A, the cored bar 2a has holes 4a formed on the surface on the + Z side and the surface on the −Z side, respectively, and the cross section in the XZ plane and the cross section in the YZ plane are H-shaped. May be formed. That is, the cored bar 2 has a shape having a partition wall inside a cylindrical part whose corners are chamfered. The depths (lengths in the Z direction) of the two hole portions 4a may be the same or different. In addition, the two holes 4a may close one or both of the + Z side and the −Z side, for example, with a lid (not shown) or the like.

  As shown in FIG. 3B, the cored bar 2b may have two slit-shaped holes 4b on each of the + Z side surface and the −Z side surface. The hole 4b is not limited to be formed on both the + Z side surface and the −Z side surface, and may be formed only on the + Z side surface, for example, or only on the −Z side surface. May be formed. Moreover, in each surface, the number of the holes 4 b is arbitrary, and may be, for example, 1 to 3 or 5 or more. Further, the shape of the hole 4 b is not limited to the slit shape, and the cross section may be circular, elliptical, oval or the like. Moreover, although the hole 4b is arrange | positioned in the vicinity of an outer peripheral side surface (surface around which the amorphous alloy 3 is wound), it is not limited to this and may be formed away from the outer peripheral side surface. The hole 4b may be formed on the outer peripheral side surface.

  Moreover, the thing of a shape like the metal core 2c shown in FIG.3 (C) may be sufficient. The metal core 2c is provided with a plurality of ribs 5a to 5c and a plurality of openings 6 inside a cylindrical portion whose corners are chamfered, and has a plurality of holes 4c in the cylindrical portion. The rib 5a is disposed in parallel with the XY plane at the central portion in the Z direction inside the cylindrical shape of the core 2c. The rib 5b is disposed in parallel with the YZ plane at a central portion in the X direction. The rib 5c is disposed in parallel to the ZX plane in the central portion in the Y direction. Thus, when it has a plurality of ribs 5a-5c, the strength of the core metal 2c can be maintained and the surface area can be expanded. The plurality of openings 6 are formed on four side surfaces. When the opening 6 is provided, the fluidity of the gas phase on the surface of the cored bar 2c facing the opening 6 becomes high, and the heat of the body to be heated 1 can be smoothly transferred through the gas phase. In addition, the number of ribs 5a-5c is arbitrary. For example, the number of the ribs 5a to 5c may be two, or four or more. Also, the number of openings 6 is arbitrary. For example, the number of openings 6 may be one to three, or five or more. The shape of the opening 6 is also arbitrary, and may be a circular shape, an elliptical shape, an oval shape, or a slit shape instead of the rectangular shape as illustrated.

  Further, the core metal 2 may be formed in combination with a material having a high thermal conductivity. FIGS. 4A and 4B are perspective views showing another example of the core metal 2. The core metal 2d shown in FIG. 4 (A) is a core metal 2b shown in FIG. 3 (B) in which a plurality of holes 4b are inserted with a heat conducting member 7d formed of a material having high thermal conductivity. . In this case, a part with high thermal conductivity is partially formed in the cored bar 2d, and heat from the heated body 1 can be smoothly transferred via the heat conductive member 7d. For example, copper is used as the heat conducting member 7d. The heat conducting member 7d may be formed in substantially the same shape as the hole 4b, and may be detachably attached to the hole 4b.

  Further, in the core metal 2e shown in FIG. 4B, a heat conducting member 7e formed of a material having a high thermal conductivity is inserted into each of the four openings 6 of the core metal 2c shown in FIG. 3C. It is done. Also in this case, similarly to the above, a part of the cored bar 2e having a high thermal conductivity is formed, and the heat of the heated body 1 can be smoothly transferred through the heat conductive member 7e. For example, copper is used for the heat conducting member 7e in the same manner as described above. Further, the heat conducting member 7 e may be formed in a shape substantially the same as the opening 6 and may be detachable from the opening 6.

  The above-described cored bars 2, 2a to 2e may be formed by cutting out from a bulk, or may be integrally formed by casting or the like. In addition, the core metals 2 and 2a to 2e may be formed by combining a plurality of members in advance (joining). When the core metal 2 and 2a to 2e have the rigidity capable of maintaining the shape of the heating target 1 in which the sheet-like amorphous alloy 3 is wound and can withstand the heat treatment, they are integrally formed. Any of the combination and the case of being formed in combination may be applied, and may be determined by the production cost of the core metal 2 or the like.

  Next, as shown in FIG. 1, the surface is covered in a state of being in contact with the body to be heated 1 with a covering member 8 having a thermal conductivity higher than that of the amorphous alloy 3 (step S2). As a result, the covering member 8 is in a state in which heat transfer is possible with respect to the heated body 1. FIG. 5 shows an example in which the object to be heated 1 is covered with the covering member 8, (A) is an exploded perspective view, and (B) is a perspective view showing a state where the object to be heated 1 is covered. The shape of the covering member 8 is appropriately set in accordance with the shape and size of the body to be heated 1 and may be any shape and size as long as it can be coated in contact with the body to be heated 1 Can be used.

  For example, as shown in FIG. 5A, the heated body 1 can be covered using a plurality of covering members 8. The covering member 8 includes a first member 10 that contacts and covers the + Z side of the heated body 1, a second member 11 that contacts and covers the outer peripheral side surface of the heated body 1, and −Z of the heated body 1. And a third member 12 contacting and covering the side. When the first member 10, the second member 11, and the third member 12 cover the heated body 1, the first member 10 and the second member 11 come into contact with each other, and the second member 11 and the third member 12 are in contact with each other. The members 12 are dimensioned to contact each other. The covering member 8 is formed of a material having a thermal conductivity higher than that of the amorphous alloy 3. For example, the covering member 8 is formed of a material containing a material having high thermal conductivity such as copper or tungsten. Especially, when formed with the material containing copper, since heat conductivity is high, the movement of the heat | fever with respect to the to-be-heated body 1 can be performed efficiently.

  The first member 10 is formed in a rectangular plate shape having a through hole 13 in the center. The through hole 13 is formed so as to open in substantially the same shape as the opening shape of the hole 4 of the core metal 2. The first member 10 covers the surface on the + Z side of the portion of the body to be heated 1 excluding the core metal 2 (see FIG. 5B). The second member 11 is formed in a band shape and wound around the outer peripheral side surface of the body to be heated 1 to cover the outer peripheral side surface of the body to be heated 1 (see FIG. 5B). At this time, the end portions of the second member 11 may be in contact with each other, or the end portions may be partially overlapped. Similar to the first member 10, the third member 12 is formed in a rectangular plate shape having a through hole 14 at the center. The through hole 14 is formed so as to open in substantially the same shape as the opening shape of the hole 4 of the cored bar 2. The third member 12 covers the surface on the -Z side of the portion of the body 1 to be heated excluding the core metal 2 (see FIG. 5B).

  The covering member 8 covers the body to be heated 1 with the first member 10, the second member 11 and the third member 12, as shown in FIG. 5 (B). Thereby, the surface can be covered in a state in which it is in contact with the heated body 1 other than the cored bar 2 using the covering member 8 having higher thermal conductivity than the amorphous alloy 3. In addition, the form of coating | cover by the coating | coated member 8 is not limited to what is shown in FIG. For example, the heated body 1 may be covered with the covering member 8 including the cored bar 2. Further, for example, the object to be heated 1 may be spirally wound and covered using a tape-shaped covering member 8 having a thin film thickness.

  Moreover, between the 1st member 10 and the 2nd member 11, and between the 2nd member 11 and the 3rd member 12 may be joined, for example with a joining material etc., and also in FIG.5 (B). As shown, it may be held by clamps C1, C2. The clamps C1 and C2 are illustrated in a simplified manner. The clamp C <b> 1 sandwiches the first member 10 and the third member 12, holds the first member 10 and the third member 12 in close contact with the heated body 1, and does not come off the heated body 1. The clamp C <b> 2 sandwiches the core metal 2 and the second member 11, holds them in close contact with the heated body 1, and prevents them from being detached from the heated body 1. Further, a plurality of the clamps C1 and C2 may be disposed at a constant interval or a predetermined interval.

  FIG. 6 is a perspective view showing an example of a covering member 8 </ b> A formed so as to accommodate the heated body 1. As shown in FIG. 6, the covering member 8A includes a first member 10A serving as a lid, a third member 12A serving as a bottom, and a second rising portion in the + Z direction from the outer periphery of the third member 12A. And a member 11A. The first member 10A, the second member 11A, and the third member 12A are formed of a material having a higher thermal conductivity than that of the amorphous alloy 3, such as copper, as in the case of the covering member 8 described above. Further, the first member 10A is provided with a through hole 13A that opens substantially in the same manner as the opening shape of the hole 4 of the core metal 2. Similarly, the third member 12A is provided with a through hole 14A that opens substantially in the same manner as the opening shape of the hole 4 of the core metal 2.

  The body to be heated 1 is accommodated inside the second member 11A and closed by the first member 10A, so that the surface on the + Z side, the outer peripheral side surface, and the surface on the −Z side of the body to be heated 1 are each The first member 10A, the second member 11A, and the third member 12A are coated in a contact state. The first member 10A and the second member 11A may be joined by a joining material or the like, or a clamp C2 as shown in FIG. 5B may be used. Further, the through-holes 13A and 14A may not be formed on the covering member 8A.

  The covering members 8, 8 </ b> A described above do not have to cover the entire surface of the heated body 1 as long as it is in contact with at least a part of the heated body 1. For example, the covering members 8, 8 </ b> A may cover at least one of the + Z side surface, the −Z side surface, and the outer peripheral side surface of the heated body 1.

  By using the covering member 8 </ b> A shown in FIG. 6, the object to be heated 1 can be covered with the covering member 8 by a simple operation of accommodating the object 1 to be heated in the covering member 8 </ b> A. Further, since the covering members 8 and 8A cover the surface of the portion to be heated 1 excluding the core metal 2, the core metal 2 is used as a part of the covering member, and the usage amount of the covering members 8 and 8A Can be reduced.

  Next, as shown in FIG. 1, the amorphous alloy 3 is nanocrystallized by heat-treating the heated object 1 covered with the covering member 8 (step S3). In this step, a nanocrystalline soft magnetic alloy core having good soft magnetic properties, including at least a portion of crystal grains having an average crystal grain size of 100 nm or less, is completed. In addition, the "nanocrystal soft-magnetic alloy" in this embodiment means the alloy which contained the crystal grain whose average grain size is 100 nm or less in at least one part.

  The heat treatment of step S3 is performed including preheating treatment (step S31), crystallization heat treatment (step S32), and cooling treatment (step S33). The preheating processing in step S31 means processing in which heating is performed at a temperature lower than the temperature at which the amorphous alloy 3 is nano-crystallized. The crystallization heat treatment in step S32 means a treatment for heating the amorphous alloy 3 to be nanocrystallized. The cooling process of step S33 means a process of cooling the nanocrystallized object 1. However, as the heat treatment of step S3, performing the processing of steps S31 to S33 as shown in FIG. 1 is an example, and other heat treatment may be applied.

  FIG. 7 is a diagram illustrating an example of the pre-heat treatment in step S31, the crystallization heat treatment in step S32, and the cooling treatment in step S33. As shown in FIG. 7, first, the temperature of the object to be heated 1 is raised from normal temperature to the preheating temperature, and heating is performed. The conditions of temperature rise before the preheating treatment are arbitrary. FIG. 7 shows an example in which the heated body 1 is heated from 20 ° C. (normal temperature) to 400 ° C. in about 45 minutes, and the temperature rising rate of the heated body 1 is about 8.44 ° C./minute. However, the rate of temperature increase is not limited to this, and for example, the rate of temperature increase may be greater than 8.44 ° C./min or may be smaller.

  The preheating process of step S31 is performed by heating the to-be-heated body 1 for a predetermined time at the above-described preheating process temperature (for example, 400 ° C.). By performing the preheating process, the amorphous alloy 3 (the body to be heated 1) can be gradually heated from normal temperature to be surely brought into a high temperature state, and can be surely transferred to the crystallization heat treatment which is the next step It becomes. The purpose of the preheating treatment is to uniformly heat treat the entire magnetic core with nanocrystallization heat treatment, and keep the whole magnetic core at a uniform temperature at a temperature lower than the nanocrystallization temperature before performing the heat treatment for crystallization.

The conditions for the preheating process in step S31 are appropriately determined depending on the composition, size, etc. of the amorphous alloy 3, but under conditions that nanocrystallization does not proceed at a temperature lower than the temperature at which the amorphous alloy 3 nanocrystals. If there is, it can be performed under any conditions. For example, the conditions for the preheating treatment can be about 50 to 200 ° C. lower than the temperature at which nanocrystallization starts, and can be performed for 30 minutes or more. For example, in the case of the Fe-Nb-B-based or Fe-Nb-B-Sn-based amorphous alloy 3, the preheating can be performed at 300 to 450 ° C. for 30 minutes or more. Although the example which is heating the to-be-heated body 1 at about 400 degreeC for about 60 minutes is shown in FIG. 7, it is not limited to this. Further, the pre-heat treatment in step S31 may be performed in a longer time than the crystallization heat treatment in later step S32. Thereby, the amorphous alloy 3 can be reliably prepared for nanocrystallization.

  Following the pre-heat treatment, a crystallization heat treatment in step S32 is performed. By performing the crystallization heat treatment, at least a part of the amorphous alloy 3 is nano-crystallized. The conditions for the crystallization heat treatment are appropriately determined depending on the composition of the amorphous alloy 3 and the like, but can be performed under any conditions as long as the temperature at which nanocrystallization is performed. For example, the crystallization heat treatment in step S32 can be performed at a temperature higher than the temperature at which nanocrystallization of the amorphous alloy 3 is started for 30 to 60 minutes. In FIG. 7, although the example to which the to-be-heated body 1 is heated at about 650 degreeC for about 30 minutes is shown, it is not limited to this. By this crystallization heat treatment, at least a part of the amorphous alloy 3 is nanocrystallized. Note that all or substantially all of the amorphous alloy 3 may be nano-crystallized by the crystallization heat treatment. In this specification, “at least a part” is used to mean that all or almost all of the amorphous alloy 3 is included, and the part necessary for obtaining good soft magnetic properties is intended to be nanocrystallized. Yes.

  For example, in the case of an Fe-Nb-B-based or Fe-Nb-B-Sn-based amorphous alloy, the crystallization heat treatment in step S32 is performed at a temperature of 500 to 700 ° C. for 30 to 60 minutes. The crystallization heat treatment in step S32 may be performed in a processing chamber different from the preheating treatment in step S31 and the cooling treatment in step S33 described later. Thereby, the setting of the heating temperature with respect to the to-be-heated body 1 can be performed easily.

  In the crystallization heat treatment in step S32, the object to be heated 1 is heated in a state of being covered by the covering member 8 (including the core metal 2). Thereby, the object to be heated 1 is indirectly heated by being heated through the covering member 8, and the state in which the influence of the heating on the object to be heated 1 is alleviated as compared with the case without the covering member 8. It has become. That is, the covering member 8 has a buffering function against the heating of the heated body 1. Further, even if the heated body 1 generates heat when the heated body 1 (amorphous alloy 3) is heated and crystallized, the heat moves to the covering member 8 and is dissipated. Thereby, it can prevent that the to-be-heated body 1 is heated exceeding suitable heat processing conditions, and can suppress that the soft magnetic characteristic of a nanocrystal soft magnetic alloy falls.

  Following the crystallization heat treatment, a cooling process of step S33 is performed. As a result, a nanocrystalline soft magnetic alloy core containing crystal grains having an average crystal grain size of 100 nm or less and having good soft magnetic properties is completed. The cooling process can be performed under any conditions. For example, the object to be heated 1 may be cooled at room temperature in a predetermined processing chamber, or may be cooled by gradually decreasing the heating temperature in the processing chamber. The cooling rate can be set arbitrarily. Although FIG. 7 shows a cooling process of leaving at room temperature after the crystallization heat treatment in step S32, the present invention is not limited thereto. In the cooling process of step S33, the object to be heated 1 may be cooled using a fluid. For example, the cooling process is performed by cooling the heated object 1 by directly or indirectly contacting the heated object 1 with a gas such as air, nitrogen gas, carbon dioxide, or a liquid such as water, oil, or fluorinate. Also good. For example, in the case of a gas, the object to be heated 1 may be cooled by blowing with a fan or the like.

  As described above, by performing the heat treatment of the body to be heated 1 by the preheating process of step S31, the crystallization heat treatment of step S32, and the cooling process of step S33, the nanocrystallization of the amorphous alloy 3 is reliably performed. be able to. Whether or not the heat treatment in step S3 is performed by a method including the above-described preheat treatment, crystallization heat treatment, and cooling treatment (steps S31 to S33) is arbitrary.

  In addition, the atmosphere gas in the case of each above-mentioned heat processing is arbitrary. As the atmosphere gas, for example, a gas inert to the body 1 to be heated, such as nitrogen gas, argon gas, helium gas, etc., may be used, and other gases, air (dry air), etc. may be used. May be used. Further, the atmosphere gas at the time of each heat treatment may be appropriately supplied into the furnace as needed, or may be exhausted from the furnace.

  As the heat treatment in step S3, an apparatus that performs preheat treatment, crystallization heat treatment, and cooling treatment (steps S31 to S33) can be performed using any apparatus. FIG. 8A shows an example of the heat treatment apparatus, and FIG. 8B shows another example of the heat treatment apparatus. In FIGS. 8A and 8B, the heat treatment devices 15 and 15a are schematically shown. As shown in FIG. 8A, the heat treatment apparatus 15 is an apparatus that performs heat treatment on the heated object 1 covered with the covering member 8. The heat treatment apparatus 15 is configured to include a covering member 8, a table 16, a first treatment chamber 17, and a second treatment chamber 18. The covering member 8 is similar to that shown in FIG. 5 described above, and instead, the covering member 8A shown in FIG. 6 may be used. The table 16, the second processing chamber 18 and the first processing chamber 17 are arranged adjacent to one another in this order in the + X direction. By this arrangement, the heat treatment can be quickly performed on the body 1 to be heated.

  The table 16 is used to carry the object 1 into or out of the first processing chamber 17. Note that whether or not the heat treatment apparatus 15 includes the table 16 is arbitrary. In addition, a plurality of rollers R are disposed at constant intervals or at predetermined intervals on the top surface of the table 16 or at the bottom of the first processing chamber 17 and the second processing chamber 18. Some or all of the plurality of rollers R are rotationally driven by a driving device (not shown) so that the heated body 1 placed thereon can be transferred in the + X direction or the −X direction. In addition, it is not limited that the roller R is used for transfer of the to-be-heated body 1, The arbitrary structures which can transfer the to-be-heated body 1 are applied. For example, instead of the roller R, a rail is laid on the table 16 and the bottom of the first processing chamber 17 and the second processing chamber 18 along the X direction, and a movable stage is used along this rail Good. In this case, the object to be heated 1 is placed on the stage, and the object to be heated 1 is transferred by the movement of the stage.

  The first processing chamber 17 nanocrystallizes the amorphous alloy by performing a crystallization heat treatment (step S32 in FIG. 1) on the heated object 1 covered with the covering member 8. The second processing chamber 18 performs at least one of preheating (step S31 in FIG. 1) and cooling (step S33 in FIG. 1) on the body 1 to be heated. Thus, when the preheating treatment and the crystallization heat treatment are performed in a treatment chamber different from the crystallization heat treatment, the treatment chamber can be set in a state suitable for each treatment, and each treatment can be efficiently performed. it can.

  The first processing chamber 17 and the second processing chamber 18 are formed so as to be able to heat the object 1 to a predetermined temperature. For example, the first processing chamber 17 and the second processing chamber 18 respectively include furnace chambers 19 and 20 and heating devices 21 and 22 such as electric heaters, and the heating devices 21 and 22 set the furnace chambers 19 and 20 to a predetermined temperature. Can be set. For example, a heat insulating material or the like may be arranged on the inner wall or the outer wall of the furnace chambers 19 and 20 so as to keep the temperature in the furnace. In addition, the furnace chambers 19 and 20 may be provided with gas inlets and gas outlets not shown. The atmosphere in the furnace chambers 19 and 20 can be adjusted by introducing the gas through the gas inlet. The first processing chamber 17 and the second processing chamber 18 are provided with a door portion that can be opened and closed (not shown), and the furnace chambers 19 and 20 are sealed by closing the door portion, and the furnace chamber is opened by opening the door portion. The object 1 to be heated can be carried into or out of the board 19 or 20.

Moreover, the apparatus which cools the part exposed to the exterior using a fluid may be provided in the table 16, the 1st process chamber 17, and the 2nd process chamber 18. As shown in FIG. In addition, the second processing chamber 18 may be provided with a device for blowing a cooling gas to the heated object 1, such as a gas stirring device such as a fan or a nozzle device for ejecting air. An apparatus may be provided to spray a liquid for cooling such as water onto the body 1 to be heated.

  When the heat treatment apparatus 15 performs the heat treatment of the heated object 1 (step S3 in FIG. 1), first, the heat treatment apparatus 15 drives the roller R to the heated object 1 placed on the −X side of the table 16 to be heated. The heating body 1 is transferred in the + X direction and carried into the second processing chamber 18. After carrying in the to-be-heated body 1 in the 2nd process chamber 18, the heating apparatus 22 is driven and the inside of the furnace chamber 20 is heated. After the temperature in the furnace chamber 20 is raised to the temperature necessary for the preheating process, the object to be heated 1 is preheated for a predetermined heating time. At this time, the heating device 21 of the first processing chamber 17 is driven to raise the temperature of the furnace chamber 19 to a temperature necessary for the crystallization heat treatment.

  Subsequently, after the pre-heat treatment, the roller R is driven to transfer the heated object 1 from the second processing chamber 18 in the + X direction and carried into the first processing chamber 17. Since the inside of the furnace chamber 19 of the first processing chamber 17 is heated to a temperature necessary for the crystallization heat treatment, the crystallization heat treatment of the heated body 1 is started almost simultaneously with the loading into the furnace chamber 19. At this time, the driving of the heating device 22 in the second processing chamber 18 is stopped, and, for example, the inside of the furnace chamber 20 is cooled to a normal temperature by introducing outside air or the like into the furnace chamber 20. Be started.

  Subsequently, after the crystallization heat treatment, the roller R is driven to transfer the heated object 1 from the first processing chamber 17 in the −X direction, and is carried into the second processing chamber 18. Since the inside of the furnace chamber 20 is cooled to the normal temperature in the second processing chamber 18, the cooling process of the body 1 to be heated is started almost simultaneously with the loading into the furnace chamber 20. Subsequently, after the object to be heated 1 is cooled, the roller R is driven to transfer the object to be heated 1 in the −X direction, and the object to be heated 1 is unloaded from the second processing chamber 18. Thus, the to-be-heated body 1 will be in the state which returned to the position before heat processing, after heat processing was completed.

  As described above, according to the heat treatment apparatus 15 described above, the heat treatment can be efficiently performed on the heating target 1 coated on the covering member 8. In addition, since the crystallization heat treatment is performed in a treatment chamber different from the other treatment, the temperature in the furnace chamber 19 necessary for the nanocrystallization can be set with high accuracy.

  Next, as illustrated in FIG. 8B, the heat treatment apparatus 15 a includes a covering member 8, a table 16, a first processing chamber 17, a second processing chamber 18, and a third processing chamber 23. Configured. The heat treatment apparatus 15 is different from the heat treatment apparatus 15 shown in FIG. 8A in that a third treatment chamber 23 is disposed on the + X side of the first treatment chamber 17. The table 16, the second processing chamber 18, the first processing chamber 17 and the third processing chamber 23 are arranged in this order in the X direction and arranged adjacent to each other. The covering member 8, the table 16, the first processing chamber 17 and the second processing chamber 18 are the same as the above-described heat treatment apparatus 15. The third processing chamber 23 includes a furnace chamber 24 and a heating device 25, and is provided with a plurality of rollers R for transporting the body 1 to be heated. Further, the third processing chamber 23 may be provided with a door (not shown) for carrying in or out the object 1 to be heated, an air supply device for introducing outside air into the furnace chamber 24, and the like.

  In this heat treatment apparatus 15 a, the object to be heated 1 is preheated in the second treatment chamber 18, the crystallizing heat treatment of the object 1 is performed in the first treatment chamber 17, and the cooling treatment is performed in the third treatment chamber 23. When the heat treatment apparatus 15a performs the heat treatment (step S3 of FIG. 1) of the object to be heated 1, first, the roller R is driven to the object to be heated 1 placed on the -X side of the table 16 to The heating body 1 is transferred in the + X direction and carried into the second processing chamber 18. The preheat treatment of the body 1 to be heated in the second treatment chamber 18 is the same as the heat treatment apparatus 15 described above. Subsequently, after the pre-heat treatment, the roller R is driven to transfer the heated object 1 from the second processing chamber 18 in the + X direction and carried into the first processing chamber 17. The crystallization heat treatment of the heated body 1 in the first treatment chamber 17 is the same as that of the heat treatment apparatus 15 described above.

  Subsequently, after the crystallization heat treatment, the roller R is driven to transfer the heated object 1 in the + X direction, and is carried from the first processing chamber 17 into the third processing chamber 23. In the third processing chamber 23, since the furnace chamber 24 is set to room temperature, the cooling process of the body 1 to be heated is started almost simultaneously with the loading into the furnace chamber 24. Subsequently, after the object to be heated 1 is cooled, the roller R is driven to transfer the object to be heated 1 in the + X direction, and the object to be heated 1 is unloaded from the third processing chamber 23. Although not shown, a table for carrying out the heated body 1 may be disposed on the + X side of the third processing chamber 23.

  Thus, after the heat treatment is completed, the object to be heated 1 is carried out to a position different from the position before the heat treatment. Further, unlike the heat treatment apparatus 15, the roller R only needs to transfer the object to be heated 1 only in the + X direction. Therefore, the drive control of the roller R is simple, and the apparatus configuration can be simplified.

  Moreover, since the to-be-heated body 1 is moved to + X direction, it is also possible to perform the preheat process, the crystallization heat treatment, and the cooling process on the to-be-heated body 1 simultaneously. For example, while the object to be heated 1 is subjected to crystallization heat treatment in the first processing chamber 17, another object to be heated 1 may be carried into the second processing chamber 18 and subjected to pre-heat treatment. Further, for example, when the heated object 1 is transferred at a constant speed in the + X direction, the furnace chamber 19 of the first processing chamber 17, the furnace chamber 20 of the second processing chamber 18, and the furnace chamber 24 of the third processing chamber 23, The processing time in each process can be set by changing the length in each X direction. As described above, by performing at least two of the pre-heat treatment, the crystallization heat treatment, and the cooling treatment at the same time, the heat treatment can be efficiently performed on the plurality of heated objects 1.

  Thus, according to the above-mentioned heat treatment apparatus 15a, it has the same effect as the above-mentioned heat treatment apparatus 15. Furthermore, since the heated body 1 is transferred in one direction and each process is performed in a specific processing chamber, temperature management in each process is easy, and the heated body 1 can be easily heat-treated. In the heat treatment apparatus 15a, it is arbitrary whether or not the third treatment chamber 23 is provided. For example, without providing the third processing chamber 23, the cooling process of the object to be heated 1 may be performed simply by leaving it in the open air.

  Hereinafter, the present invention will be specifically described by way of Examples and Comparative Examples, but the present invention is not limited thereto.

[Example]
The performance evaluation test of the nanocrystalline soft magnetic alloy core manufactured by the method of manufacturing the nanocrystalline soft magnetic alloy core described above was conducted.

  The nanocrystalline soft magnetic alloy magnetic core was manufactured as follows. First, a core-shaped to-be-heated body 1 shown in FIG. 2 (A) was formed. The body 1 to be heated was molded in a state where a sheet-like amorphous alloy 3 was wound around the cored bar 2. The core metal 2 is formed of a metal material containing iron as a main component, and shown in FIG. 2A, the length in the Y direction is 50 mm, the length in the X direction is 144 mm, and the thickness in the Z direction is The one of 25 mm was used. In addition, as the amorphous alloy 3, a 50 mm wide sheet made of an Fe-Nb-B based alloy was used. The size of the molded object 1 to be heated was 194 mm in length in the Y direction, 100 mm in length in the X direction, and 25 mm in thickness in the Z direction, as shown in FIG.

  Next, the surface of the body to be heated 1 excluding the core metal 2 was covered in a state of being in contact with the body to be heated 1 by the covering member 8 shown in FIGS. 5 (A) and 5 (B). The covering member 8 is made of a metal material mainly composed of copper and has a thickness of about 10 mm. As samples for evaluation, a plurality of heated bodies 1 covered with the covering member 8 and a plurality of heated bodies 1 not covered with the covering member 8 (comparative example) were prepared.

  Next, the amorphous alloy 3 was nano-crystallized by heat-treating each heating target 1. The heat treatment was performed by performing a preheating treatment, a crystallization heat treatment, and a cooling treatment using a heat treatment apparatus 15 shown in FIG. About the heat processing of the to-be-heated body 1, it carried out in substantially the same way as FIG. First, in the second treatment chamber 18, the heated body 1 is heated from room temperature to 400 ° C. at a heating rate of about 10 ° C./min, and the heated body 1 is held at 400 ° C. for 60 minutes for pre-heat treatment. Went. Immediately after the pre-heat treatment, crystallization heat treatment was performed by holding the object 1 to be heated at a plurality of crystallization heat treatment temperatures for a plurality of treatment times. Immediately after the crystallization heat treatment, the object to be heated 1 was cooled at room temperature. Through the above steps, a nanocrystalline soft magnetic alloy core containing crystal grains having an average crystal grain size of 100 nm or less was manufactured.

  Next, the performance evaluation test of the nanocrystalline soft magnetic alloy core was conducted. The performance evaluation test was performed by measuring the iron loss of the nanocrystalline soft magnetic alloy core. The core loss is measured by attaching the primary coil and the secondary coil to the core metal of the manufactured nanocrystalline soft magnetic alloy core removed, and using an AC BH measuring device, a sine of magnetic flux density 1.33 T, frequency 50 Hz It did by giving the alternating magnetic field of the wave. In addition, the measurement of the iron loss of all the samples was performed on the same conditions except the temperature and time of crystallization heat processing. The temperature and time of the crystallization heat treatment for each sample are as shown in FIG. Moreover, the graph of FIG. 9 has shown the relationship of the temperature of a heat treatment for crystallization, and an iron loss about each sample. As shown in FIG. 9, the one produced by the method for producing a nanocrystalline soft magnetic alloy core using the covering member 8 is the same as the covering member 8 under the conditions of all crystallization heat treatment temperatures and crystallization heat treatment times tested. It was confirmed that there was little iron loss compared with the to-be-heated body 1 which does not use.

  Moreover, the temperature of the amorphous alloy 3 part at the time of crystallization heat processing was measured about some samples. The results are shown in FIG. In FIG. 10, the crystallization heat treatment is performed at different temperatures using a sample using the covering member 8 and a sample not using the covering member 8. As shown in FIG. 10, when the crystallization heat treatment is performed without covering the covering member 8, the maximum temperature of the amorphous alloy 3 during the crystallization heat treatment is 673 although the crystallization heat treatment temperature is as low as 560.degree. The temperature rose to ℃ and was about 113 ℃ higher than the crystallization heat treatment temperature. This means that the amorphous alloy 3 generates heat as the crystals are formed by the crystallization heat treatment, and the temperature rises. On the other hand, when covered with the covering member 8 at the time of the crystallization heat treatment, the maximum temperature of the amorphous alloy 3 at the time of the crystallization heat treatment is only about 24 ° C. higher than the crystallization heat treatment temperature although the crystallization heat treatment temperature is high at 650 ° C. ing. From this result, it is confirmed that the covering member 8 suppresses the temperature rise of the amorphous alloy 3 accompanying the crystal formation by the crystallization heat treatment.

  That is, in the heated body 1 that is not covered with the covering member 8, the temperature of the heated body 1 is significantly higher than the temperature of the crystallization heat treatment due to heat generation of the material during the crystallization heat treatment. As a result, the temperature of the heated body 1 exceeds an appropriate heat treatment condition, which causes an increase in iron loss as shown in FIG. On the other hand, in the object to be heated 1 covered with the covering member 8, even when the crystallization heat treatment is performed, the heat generation of the material is suppressed or the heat generation of the material is absorbed. It is suppressed that the temperature is significantly higher than the set temperature.

  As a result of this performance evaluation test, by covering the object to be heated 1 with the covering member 8, the temperature rise accompanying the crystallization of the amorphous alloy 3 is effectively suppressed, and the amorphous material is obtained at a temperature close to the target crystallization heat treatment temperature. By performing the crystallization heat treatment of the alloy, it is possible to prevent the soft magnetic properties of the obtained nanocrystalline soft magnetic alloy core from being deteriorated. From this, it is understood that the method of manufacturing a nanocrystalline soft magnetic alloy core can produce a nanocrystalline soft magnetic alloy core having good soft magnetic properties.

  As described above, according to the method of manufacturing a nanocrystalline soft magnetic alloy core according to the embodiment, the temperature of the material is higher than the heat treatment set temperature when the amorphous alloy which is the material of the nanocrystalline soft magnetic alloy core is heat treated Can be reliably suppressed with a simple configuration, and a nanocrystalline soft magnetic alloy core having good soft magnetic properties can be manufactured.

  Although the embodiments and examples of the present invention have been described above, the technical scope of the present invention is not limited to the above embodiments and examples. For example, one or more of the requirements described in the above embodiments and examples may be omitted. Moreover, the requirements described in the above embodiments and examples can be combined as appropriate. In the above-described embodiment, the heat treatment apparatuses 15 and 15a having a plurality of treatment chambers are shown, but a heat treatment apparatus having one treatment chamber may be used.

DESCRIPTION OF SYMBOLS 1 ... Heating body, 2, 2a-2e ... Core metal, 3 ... Amorphous alloy, 4, 4a-4c ... Hole part, 8, 8A ... Coating member, 15, 15a ... Heat processing apparatus, 17 ... 1st processing chamber, 18 ... Second processing chamber

Claims (9)

A method of manufacturing a nanocrystalline soft magnetic alloy core having soft magnetic properties, comprising a crystal grain having an average crystal grain size of 100 nm or less, comprising:
Forming a core-shaped object to be heated in a state in which a sheet-like amorphous alloy is wound around a core metal;
The upper surface, the lower surface, and the outer peripheral side surface of the body to be heated in a state in which the body to be heated, which is molded in a state wound around the cored bar, is in contact with the body to be heated by a covering member having a thermal conductivity higher than that of the amorphous alloy. Covering the
Nano-crystallizing the amorphous alloy by heat-treating the object-to-be-heated coated with the covering member;
The cored bar has a hole, and the covering member has a through hole that opens in the same manner as the shape of the hole in the cored bar. As the covering member, one formed so as to be able to accommodate the object to be heated is used.
The method for producing a nanocrystalline soft magnetic alloy core according to claim 1, wherein the surface of the body to be heated is covered by housing the body to be heated in the covering member.   The method for manufacturing a nanocrystalline soft magnetic alloy magnetic core according to claim 1 or 2, wherein the covering member is made of a material containing copper.   The nanocrystalline soft magnetic alloy core according to any one of claims 1 to 3, wherein the heat treatment includes performing preheat treatment, performing crystallization heat treatment, and performing cooling treatment. Manufacturing method.   The method for manufacturing a nanocrystalline soft magnetic alloy core according to claim 4, wherein the crystallization heat treatment is performed in a treatment chamber different from the preheating treatment and the cooling treatment.   The method for producing a nanocrystalline soft magnetic alloy core according to claim 4, wherein the preheating treatment is performed for a treatment time longer than the crystallization heat treatment. A heat treatment apparatus for producing a nanocrystalline soft magnetic alloy core having soft magnetic properties, comprising a crystal grain having an average crystal grain size of 100 nm or less, comprising:
A core metal for winding sheet-like amorphous alloy,
The upper surface, the lower surface, and the outer peripheral side surface of the body to be heated are covered with the body to be heated, which is molded in a state of being wound around the core, wound around the core metal, and the thermal conductivity is higher than that of the amorphous alloy. A high covering member,
A first processing chamber for performing a crystallization heat treatment on the heating target coated on the covering member to nanocrystallize the amorphous alloy;
A second treatment chamber that is disposed adjacent to the first treatment chamber and that performs at least one of a preheat treatment and a cooling treatment on the heated body covered with the covering member;
The heat treatment apparatus, wherein the cored bar has a hole, and the covering member has a through hole that opens in the same manner as the opening shape of the hole of the cored bar.   The heat treatment apparatus according to claim 7, wherein the covering member is formed so as to be able to accommodate the body to be heated.   The heat treatment apparatus according to claim 7, wherein the covering member is formed of a material containing copper.

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