Annealing method for iron core and jig for annealing

Abstract

To provide an annealing method for an iron core and a jig for annealing that can suppress the deterioration of dimensional accuracy in an iron core.SOLUTION: An annealing method for a stator core 10 comprises a placement process and an annealing process. In the placement process, a stator core 10 is placed on a placement surface 20a of a jig for annealing 20 that is formed from a material having a linear expansion coefficient different from that of the stator core 10. In the annealing process, the stator core 10 placed on the placement surface 20a is annealed. The placement surface 20a is formed with a plurality of protrusions 22 spaced apart from each other, which support the stator core 10 from below.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an annealing method and an annealing jig for an iron core. [Background technology]

[0002] Conventionally, motor cores for rotating electrical machines are composed of laminated cores in which multiple plate-shaped core pieces are stacked. Because the core pieces are formed by punching steel sheets, residual stresses from punching can cause distortion in the core pieces. Annealing the laminated core in an atmospheric gas is known as a method for removing such distortion.

[0003] Patent Document 1 discloses a method of annealing a laminated iron core placed on a plate-shaped pallet in an annealing furnace. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-132434 Summary of the Invention [Problem to be solved by the invention]

[0005] In the method described in Patent Document 1, if the linear expansion coefficients of the laminated core and the pallet are different, the laminated core and the pallet will have different amounts of thermal expansion and will also have different amounts of thermal contraction. Therefore, when the laminated core is annealed, the laminated core and the pallet move relative to each other, i.e., the laminated core and the pallet slide against each other. As a result, shear forces act on the laminated core, which can deform the laminated core and reduce its dimensional accuracy.

[0006] It should be noted that this problem does not only arise when annealing laminated cores for rotating electrical machines, but also occurs similarly when annealing various types of cores that utilize the principle of electromagnetic induction. [Means for solving the problem]

[0007] The annealing method for an iron core to solve the above problem is an annealing method for annealing an iron core, and includes a placing step of placing the iron core on a placing surface of an annealing jig formed from a material having a different linear expansion coefficient from that of the material of the iron core, and an annealing step of annealing the iron core placed on the placing surface, wherein the placing surface has a plurality of protrusions formed thereon that support the iron core from below and are spaced apart from one another.

[0008] According to the above configuration, when the iron core is annealed, the iron core is supported from below by the multiple protrusions of the annealing jig. Therefore, the contact area between the iron core and the annealing jig is smaller than when the entire lower surface of the iron core is in contact with the annealing jig. This reduces the shear force acting on the iron core when the iron core and the annealing jig move relative to each other during annealing due to the difference in their linear expansion coefficients. Therefore, it is possible to prevent a decrease in the dimensional accuracy of the iron core.

[0009] Furthermore, when an iron core is annealed, an oxide film is formed on the surface of the iron core due to a chemical reaction with the atmospheric gas. To improve the corrosion resistance and rust prevention properties of the iron core, it is desirable for an oxide film to be formed on the entire surface of the iron core. However, if the entire underside of the iron core comes into contact with the annealing jig, it becomes difficult for the atmospheric gas to reach the underside of the iron core, making it difficult for an oxide film to form on the underside of the iron core.

[0010] In this regard, with the above-described configuration, since the multiple protrusions are spaced apart from one another, gaps are formed between the protrusions and the underside of the iron core. By allowing atmospheric gas to enter these gaps, the atmospheric gas can more easily reach the underside of the iron core. Therefore, an oxide film is more likely to form on the underside of the iron core.

[0011] In addition, a method for annealing an iron core to solve the above problem is an annealing method for annealing an iron core, comprising a placing step of placing the iron core on a placing surface of an annealing jig formed from a material having a different linear expansion coefficient from the material of the iron core, and an annealing step of annealing the iron core placed on the placing surface, wherein the annealing jig has a base material and a coating that covers the surface of the base material and constitutes the placing surface, and the coefficient of friction between the coating and the iron core is smaller than the coefficient of friction between the base material and the iron core.

[0012] According to the above configuration, since a coating is formed on the surface of the base material, the frictional force generated between the annealing jig and the iron core can be reduced compared to when no coating is formed. This reduces the shear force acting on the iron core when the iron core and the annealing jig move relative to each other during annealing due to the difference in their linear expansion coefficients. Therefore, it is possible to suppress a decrease in the dimensional accuracy of the iron core.

[0013] In addition, an annealing jig for solving the above problem is an annealing jig that has a mounting surface on which the iron core is placed when annealing the iron core, and is made of a material that has a different linear expansion coefficient from the material of the iron core, and the mounting surface has a plurality of protrusions that are spaced apart from each other and support the iron core from below.

[0014] According to the above configuration, it is possible to achieve effects similar to those of the first iron core annealing method. In addition, an annealing jig for solving the above problem has a mounting surface on which the iron core is placed when annealing the iron core, and is formed from a material with a different linear expansion coefficient than the material of the iron core, and has a base material and a coating that covers the surface of the base material and forms the mounting surface, and the coefficient of friction between the coating and the iron core is smaller than the coefficient of friction between the base material and the iron core.

[0015] According to the above configuration, it is possible to achieve effects similar to those of the second iron core annealing method. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing a stator core of the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a crimped portion of the stator core of FIG. [Figure 3] FIG. 3 is a cross-sectional view showing the annealing jig of the first embodiment. [Figure 4] FIG. 4 is a plan view showing the annealing jig of FIG. [Figure 5] FIG. 5 is a cross-sectional view showing the stator core during annealing. [Figure 6] FIG. 6 is a cross-sectional view showing an annealing jig according to the second embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing an annealing jig according to the third embodiment. [Figure 8] FIG. 8 is a plan view showing the annealing jig of the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] [First embodiment] A first embodiment in which the iron core annealing method and annealing jig are embodied as a method for annealing a stator core of a rotating electrical machine and an annealing jig used in the method will be described below with reference to Figures 1 to 5. Note that in each drawing, for the sake of convenience, some of the configuration may be shown exaggerated or simplified.

[0018] First, the stator core 10 will be described. (Stator core 10) As shown in FIG. 1, the stator core 10 is generally cylindrical and has a central hole 10a. The stator core 10 is formed by stacking a plurality of thin-plate-shaped iron core pieces 11. The iron core pieces 11 are formed, for example, by punching an iron-based magnetic material such as an electromagnetic steel sheet. The stator core 10 is an example of an "iron core" and a "laminated iron core."

[0019] Hereinafter, the lamination direction of stator core 10 will be simply referred to as the lamination direction, the circumferential direction of stator core 10 will be simply referred to as the circumferential direction, and the radial direction of stator core 10 will be simply referred to as the radial direction. The stator core 10 has an annular yoke 12 and a plurality of teeth 13. The plurality of teeth 13 extend radially inward from the yoke 12 and are spaced apart from one another in the circumferential direction.

[0020] Between the teeth 13 adjacent to each other in the circumferential direction, a slot 14 is formed, which opens radially inward and extends radially. The stator core 10 has a plurality of mounting portions 15 for fixing the stator core 10 to a case of a rotating electrical machine (not shown). The mounting portions 15 protrude radially outward from the outer periphery of the yoke 12 and are spaced apart from one another in the circumferential direction. The stator core 10 of this embodiment has three mounting portions 15. Each mounting portion 15 has a mounting hole 15a that penetrates the mounting portion 15 in the stacking direction. The stator core 10 and the case are fixed by bolts (not shown) that are inserted into each mounting hole 15a.

[0021] The stator core 10 has a plurality of crimped portions 16 provided at intervals in the circumferential direction on the yoke 12. The stator core 10 is configured by stacking a plurality of core blocks, each of which is formed by crimping a plurality of core pieces 11 together at the crimped portions 16. The core blocks are joined to each other by, for example, welding.

[0022] As shown in Fig. 2, the crimping portion 16 includes a dowel 16a formed in a predetermined core piece 11 and a through hole 16b formed in an iron core piece 11 different from the iron core piece 11 on which the dowel 16a is formed. The dowel 16a bulges out on one side in the stacking direction of the iron core pieces 11. The iron core pieces 11 on which the dowels 16a are formed are joined to each other by crimping the dowels 16a in a concave-convex relationship. The iron core piece 11 on which the dowel 16a is formed and the iron core piece 11 on which the through hole 16b is formed are joined to each other by fitting the dowel 16a into the through hole 16b.

[0023] (Annealing jig 20) Next, the annealing jig 20 used when annealing the stator core 10 will be described. 3 and 4, the annealing jig 20 is a jig on which the stator core 10 is placed when annealing the stator core 10. The annealing jig 20 also functions as a transport jig for transporting the stator core 10 to an annealing furnace 40, which will be described later.

[0024] The annealing jig 20 has a flat plate shape and is made of a material having a linear expansion coefficient different from that of the material of the stator core 10. The annealing jig 20 is made of, for example, stainless steel.

[0025] The annealing jig 20 has a mounting surface 20a on which the stator core 10 is mounted. The mounting surface 20a is larger than the lower surface, which is one end surface of the stator core 10 in the lamination direction. The mounting surface 20a is formed with a flat surface 21 and a plurality of fine protrusions 22 protruding from the flat surface 21. The protrusions 22 support the lower surface of the stator core 10 from below. The protrusions 22 are formed spaced apart from one another over the entire mounting surface 20a. The protrusions 22 protrude from the flat surface 21 by a height of, for example, several μm to several mm. The plurality of protrusions 22 are formed by, for example, shot blasting or transferring a mold shape.

[0026] (Annealing method) Next, a method for annealing the stator core 10 will be described. The annealing method includes a placing step and an annealing step.

[0027] 3, in the placing step, the stator core 10 is placed on the placing surface 20a of the annealing jig 20. At this time, the stator core 10 and the annealing jig 20 are in contact only at the plurality of protrusions 22. As a result, a gap G into which atmospheric gas enters is formed between the flat portion 21, the plurality of protrusions 22, and the underside of the stator core 10.

[0028] As shown in FIG. 5, in the annealing step, the annealing jig 20 on which the stator core 10 is placed is transported into the annealing furnace 40 by the transport device 30. The conveying device 30 is, for example, a belt conveyor having an endless belt 31 and a pulley 32 that drives the belt 31.

[0029] Next, the annealing furnace 40 filled with the atmospheric gas is heated to anneal the stator core 10. The atmospheric gas is, for example, nitrogen gas. When the stator core 10 is annealed, a chemical reaction with the atmospheric gas causes an oxide film to be formed on the surface of the stator core 10. This oxide film has the function of improving the corrosion resistance and rust prevention properties of the stator core 10.

[0030] <Actions and Effects of This Embodiment> (1-1) The annealing method for the stator core 10 includes a mounting step and an annealing step. In the mounting step, the stator core 10 is mounted on a mounting surface 20a of an annealing jig 20 made of a material having a different linear expansion coefficient from the material of the stator core 10. In the annealing step, the stator core 10 mounted on the mounting surface 20a is annealed. A plurality of protrusions 22 are formed on the mounting surface 20a, which support the stator core 10 from below and are spaced apart from one another.

[0031] According to the above configuration, when the stator core 10 is annealed, the stator core 10 is supported from below by the multiple protrusions 22 of the annealing jig 20. Therefore, the contact area between the stator core 10 and the annealing jig 20 is smaller than when the entire lower surface of the stator core 10 is in contact with the annealing jig 20. This makes it possible to reduce the shear force acting on the stator core 10 when the stator core 10 and the annealing jig 20 move relative to each other during annealing due to a difference in their linear expansion coefficients. Therefore, it is possible to suppress a decrease in the dimensional accuracy of the stator core 10.

[0032] Furthermore, when the stator core 10 is annealed, an oxide film is formed on the surface of the stator core 10 due to a chemical reaction with the atmospheric gas. In order to improve the corrosion resistance and rust prevention properties of the stator core 10, it is desirable that an oxide film be formed on the entire surface of the stator core 10. However, if the entire lower surface of the stator core 10 comes into contact with the annealing jig 20, it becomes difficult for the atmospheric gas to reach the lower surface of the stator core 10, and therefore it becomes difficult for an oxide film to be formed on the lower surface of the stator core 10.

[0033] In this regard, with the above configuration, the multiple protrusions 22 are spaced apart from one another, so that gaps G are formed between the protrusions 22 and the underside of the stator core 10. By allowing atmospheric gas to enter these gaps G, the atmospheric gas can more easily reach the underside of the stator core 10. Therefore, an oxide film is more likely to be formed on the underside of the stator core 10.

[0034] (1-2) The stator core 10 is formed by laminating a plurality of thin plate-shaped core pieces 11. Each of the core pieces 11 constituting the stator core 10 is thin and therefore has low rigidity. Therefore, when a shear force acts on the stator core 10 due to the relative movement between the stator core 10 and the annealing jig 20 during annealing, the core pieces 11 are likely to deform. As a result, the dimensional accuracy of the stator core 10 is likely to decrease.

[0035] In this regard, according to the above configuration, the contact area between the stator core 10 and the annealing jig 20 is reduced by the multiple protrusions 22, thereby reducing the shear force acting on the core piece 11, and thereby suppressing a decrease in the dimensional accuracy of the stator core 10.

[0036] [Second embodiment] The second embodiment will be described below, focusing on the differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant description will be omitted.

[0037] In the second embodiment, the configuration of an annealing jig 120 is different from that of the annealing jig 20 of the first embodiment. As shown in FIG. 6, the annealing jig 120 has a base material 123 having a flat portion 21 and a plurality of protrusions 22, and a coating 124 covering the surfaces of the plurality of protrusions 22.

[0038] The base material 123 has the same configuration as the annealing jig 20 of the first embodiment. That is, the base material 123 is made of a material having a linear expansion coefficient different from that of the material of the stator core 10.

[0039] The coating 124 covers the entire surface of the base material 123. The surface of the coating 124 forms the mounting surface 120a of the annealing jig 120. A gap G is formed between the protrusions 22 on which the coating 124 is formed. The coefficient of friction between the coating 124 and the stator core 10 is smaller than the coefficient of friction between the base material 123 and the stator core 10. The coating 124 preferably has heat resistance. The coating 124 is, for example, chrome plating.

[0040] The annealing method of this embodiment is the same as the annealing method of Embodiment 1. That is, in the annealing step, the stator core 10 placed on the mounting surface 120a formed by the coating 124 is annealed.

[0041] <Actions and Effects of This Embodiment> According to the second embodiment, in addition to the actions and effects (1-1) and (1-2) of the first embodiment, the following actions and effects can be achieved.

[0042] (2-1) The annealing jig 120 has a base material 123 having a plurality of protrusions 22, and a coating 124 that covers the surfaces of the plurality of protrusions 22 and forms the mounting surface 120a. The coefficient of friction between the coating 124 and the stator core 10 is smaller than the coefficient of friction between the base material 123 and the stator core 10.

[0043] According to the above configuration, since the coating 124 is formed on the surface of the protrusions 22, the frictional force generated between the annealing jig 120 and the stator core 10 can be reduced compared to when the coating 124 is not formed. This makes it possible to reduce the shear force acting on the stator core 10 when the stator core 10 and the annealing jig 120 move relative to each other during annealing due to the difference in their linear expansion coefficients. Therefore, it is possible to suppress a decrease in the dimensional accuracy of the stator core 10.

[0044] [Third embodiment] The following describes the third embodiment, focusing on the differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant description will be omitted.

[0045] In the third embodiment, the configuration of an annealing jig 220 differs from that of the annealing jig 20 of the first embodiment. As shown in FIG. 7, the annealing jig 220 has a flat plate-shaped substrate 223 and a coating 224 covering the surface of the substrate 223.

[0046] The base material 223 is the annealing jig 20 of the first embodiment without the plurality of protrusions 22. That is, the base material 223 is made of a material having a linear expansion coefficient different from that of the material of the stator core 10.

[0047] The coating 224 covers the entire surface of the base material 223. The surface of the coating 224 forms the mounting surface 220a of the annealing jig 220. The coefficient of friction between the coating 224 and the stator core 10 is smaller than the coefficient of friction between the base material 223 and the stator core 10. The coating 224 preferably has heat resistance. The coating 224 is, for example, chrome plating.

[0048] The annealing method of this embodiment is the same as the annealing method of Embodiment 1. That is, in the annealing step, the stator core 10 placed on the placement surface 220a formed by the coating 224 is annealed.

[0049] <Actions and Effects of This Embodiment> According to the third embodiment, in addition to the effects and advantages (1-2) of the first embodiment, the following effects and advantages can be achieved.

[0050] (3-1) The annealing jig 220 has a base material 223 and a coating 224 that covers the surface of the base material 223 and forms the mounting surface 220a. The coefficient of friction between the coating 224 and the stator core 10 is smaller than the coefficient of friction between the base material 223 and the stator core 10.

[0051] According to the above configuration, since coating 224 is formed on the surface of base material 223, the frictional force generated between annealing jig 220 and stator core 10 can be reduced compared to when coating 224 is not formed. This makes it possible to reduce the shear force acting on stator core 10 when stator core 10 and annealing jig 220 move relative to each other during annealing due to the difference in their linear expansion coefficients. Therefore, it is possible to suppress a decrease in the dimensional accuracy of stator core 10.

[0052] [Fourth embodiment] The following describes the fourth embodiment, focusing on the differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant description will be omitted.

[0053] In the fourth embodiment, the configuration of an annealing jig 320 is different from that of the annealing jig 20 of the first embodiment. As shown in Fig. 8, the mounting surface 320a of the annealing jig 320 is formed with a flat portion 21 and a plurality of fine protrusions 322 protruding from the flat portion 21. The plurality of protrusions 322 extend radially from the center of the mounting surface 320a. More specifically, the mounting surface 320a has a plurality of protrusion groups 322G, each of which includes a plurality of protrusions 322 aligned on the same line at intervals from one another, radially arranged around the center of the mounting surface 320a in the planar direction. Each of the protrusions 322 has an elliptical shape that is long in the radial direction and centered on the center of the mounting surface 320a. The plurality of protrusions 322 are formed, for example, by transferring the shape of a mold.

[0054] In the mounting step of this embodiment, the stator core 10 is mounted on the mounting surface 320a so that the central portion of the mounting surface 320a is surrounded by the outer edge of the lower surface, which is the contact surface of the stator core 10 that contacts the mounting surface 320a. More specifically, the stator core 10 is mounted on the mounting surface 320a so that the central portion of the mounting surface 320a is surrounded by the center hole 10a of the stator core 10. The annealing step of this embodiment is the same as the annealing step of the first embodiment.

[0055] <Actions and Effects of This Embodiment> According to the fourth embodiment, in addition to the actions and effects (1-1) and (1-2) of the first embodiment, the following actions and effects can be achieved.

[0056] (4-1) The multiple protrusions 322 extend radially from the center of the mounting surface 320a. In the mounting step, the stator core 10 is mounted on the mounting surface 320a so that the center of the mounting surface 320a is surrounded by the outer edge of the lower surface of the stator core 10 that is in contact with the mounting surface 320a.

[0057] According to the above configuration, the radial direction of the stator core 10 and the direction in which each protrusion 322 extends tend to coincide. As a result, when the stator core 10 thermally expands and contracts in the radial direction before and after annealing the stator core 10, the protrusions 322 move in the radial direction in accordance with the thermal expansion and contraction of the mounting surface 320a. Therefore, compared to when each protrusion 322 extends in a direction perpendicular to the radial direction, for example, an increase in the area over which each protrusion 322 slides against the lower surface of the stator core 10 can be suppressed. Therefore, the shear force acting on the stator core 10 can be reduced.

[0058] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0059] In the second embodiment, the coating 124 may cover only the surface of the protrusion 22 . In the second and third embodiments, the coatings 124, 224 may be a type of plating other than chrome plating. Also, the coatings 124, 224 may be formed by, for example, PVD (physical vapor deposition) or CVD (chemical vapor deposition).

[0060] In the second and third embodiments, when an insulating coating is formed on the surface of the iron core piece 11, it is preferable that the coefficient of friction between the coating 124, 224 of the annealing jig 120, 220 and the insulating coating is smaller than the coefficient of friction between the base material 123, 223 and the insulating coating.

[0061] In the fourth embodiment, the coating 124 of the second embodiment can also be applied. That is, the annealing jig 320 may have the coating 124 covering the surfaces of the protrusions 322. In each embodiment, the core blocks of the stator core 10 do not have to be joined to each other by welding. The core blocks may be crimped to each other with dowels 16a, or may be joined to each other via a resin material.

[0062] The iron core annealing method and annealing jig can also be embodied as various iron core annealing methods that utilize the principle of electromagnetic induction, and annealing jigs used in the methods. Such iron cores may be rotor cores for rotating electrical machines or iron cores for transformers. Furthermore, the iron core is not limited to those constructed by stacking multiple thin-plate iron core pieces, and may be formed from a single magnetic material.

[0063] <Additional Notes> The above embodiment includes the configurations described in the following supplementary notes. [Appendix 1] A method for annealing an iron core, comprising: a placing step of placing the iron core on a placing surface of an annealing jig made of a material having a different linear expansion coefficient from that of the material of the iron core; and an annealing step of annealing the iron core placed on the placing surface, wherein the placing surface has a plurality of protrusions formed thereon that support the iron core from below and are spaced apart from one another.

[0064] [Appendix 2] The annealing jig has a base material having the plurality of protrusions and a coating that covers the surfaces of the plurality of protrusions and forms the mounting surface, and the coefficient of friction between the coating and the iron core is smaller than the coefficient of friction between the base material and the iron core. [Appendix 1]

[0065] [Appendix 3] A method for annealing an iron core described in [Appendix 1] or [Appendix 2], wherein the plurality of protrusions extend radially from a center of the mounting surface, and in the mounting step, the iron core is placed on the mounting surface so that the center of the mounting surface is surrounded by the outer edge of the contact surface of the iron core that contacts the mounting surface.

[0066] [Appendix 4] A method for annealing an iron core according to any one of [Appendix 1] to [Appendix 3], wherein the iron core is a laminated iron core formed by stacking a plurality of thin plate-shaped iron core pieces. [Explanation of symbols]

[0067] G...gap 10... Stator core 10a…Center hole 11...Iron core piece 12…York 13...Teeth 14...Slot 15...Mounting part 15a...Mounting hole 16... Crimping part 16a...Double 16b...Through hole 20, 120, 220, 320... Annealing jig 20a, 120a, 220a, 320a...Placement surface 21...Plane part 22,322…protrusion 30...Transportation device 31...Belt 32...pulley 40...Annealing furnace 123,223…Base material 124,224...Coating 322G…Protrusion group

Claims

1. A method for annealing an iron core, comprising: a placing step of placing the iron core on a placing surface of an annealing jig made of a material with a linear expansion coefficient different from that of the material of the iron core; an annealing step of annealing the iron core placed on the placement surface, The mounting surface is provided with a plurality of projections spaced apart from one another and supporting the iron core from below. Annealing method for iron cores.

2. the annealing jig includes a base material having the plurality of protrusions, and a coating that covers surfaces of the plurality of protrusions and constitutes the mounting surface, a coefficient of friction between the coating and the iron core is smaller than a coefficient of friction between the substrate and the iron core; The method for annealing an iron core according to claim 1 .

3. the plurality of protrusions extend radially from a center of the placement surface, In the placing step, the iron core is placed on the placing surface such that a central portion of the placing surface is surrounded by an outer edge of a contact surface of the iron core that contacts the placing surface. The method for annealing an iron core according to claim 1 .

4. A method for annealing an iron core, comprising: a placing step of placing the iron core on a placing surface of an annealing jig made of a material with a linear expansion coefficient different from that of the material of the iron core; an annealing step of annealing the iron core placed on the placement surface, the annealing jig has a base material and a coating that covers a surface of the base material and forms the mounting surface, a coefficient of friction between the coating and the iron core is smaller than a coefficient of friction between the substrate and the iron core; Annealing method for iron cores.

5. The iron core is a laminated iron core formed by stacking a plurality of thin plate-shaped iron core pieces. The method for annealing an iron core according to any one of claims 1 to 4.

6. An annealing jig having a mounting surface on which an iron core is placed during annealing of the iron core, the annealing jig being made of a material having a linear expansion coefficient different from that of a material of the iron core, The mounting surface is provided with a plurality of projections spaced apart from one another and supporting the iron core from below. Annealing jig.

7. a base material having the plurality of protrusions; and a coating that covers the surfaces of the plurality of protrusions and constitutes the mounting surface, a coefficient of friction between the coating and the iron core is smaller than a coefficient of friction between the substrate and the iron core; The annealing jig according to claim 6.

8. The plurality of protrusions extend radially from a central portion of the mounting surface. The annealing jig according to claim 6 or 7.

9. An annealing jig having a mounting surface on which an iron core is placed during annealing of the iron core, the annealing jig being made of a material having a linear expansion coefficient different from that of a material of the iron core, The device has a base material and a coating that covers a surface of the base material and forms the mounting surface, a coefficient of friction between the coating and the iron core is smaller than a coefficient of friction between the substrate and the iron core; Annealing jig.

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