JP6638599B2 - Wound iron core and method of manufacturing the wound iron core - Google Patents

Description

  The present invention relates to a wound iron core manufactured by using a grain-oriented electrical steel sheet having grooves formed by laser beam irradiation, and a method of manufacturing the wound iron core.

  A grain-oriented electrical steel sheet has a low energy loss (iron loss) when magnetized with a relatively small magnetizing force, and is therefore used, for example, when manufacturing a core of a transformer (transformer). The surface of the grain-oriented electrical steel sheet is usually coated with an insulating film. Thereby, insulation between the steel plate layers in the wound iron core is ensured.

  In the above-described grain-oriented electrical steel sheets, it is required to further reduce iron loss. As a measure for improving such iron loss, a method of forming a groove in a steel sheet has been used.

  For example, as disclosed in Patent Document 1 below, there is a method of forming a groove by electrolytic etching. In such a method, for example, using a steel sheet having a glass coating formed on the surface after secondary recrystallization, the glass coating on the surface is linearly removed by laser or a mechanical method, and a groove is formed in a portion where the ground iron is exposed by etching. To form However, in the electrolytic etching method, the process is complicated, the manufacturing cost is increased, and the processing speed is limited.

  Further, as disclosed in Patent Document 2, there is a method of forming a groove by a mechanical tooth press. However, in such a method, since the electromagnetic steel sheet is a very hard steel sheet containing about 3% of Si, abrasion and damage of the tooth mold are likely to occur. When the tooth form is worn, the groove depth varies, so that the iron loss improvement effect becomes non-uniform.

  As a method for solving the problem of the above-mentioned method, there is a method of forming a groove by irradiating a steel plate with a laser beam as disclosed in Patent Documents 3 and 4. In such a method, high-speed groove processing can be performed by a focused laser beam having a high power density. In addition, since non-contact processing is performed, it is possible to stably and uniformly perform groove processing by controlling laser power and the like.

Japanese Patent Publication No. Sho 62-54873 JP-B-62-53579 JP-A-6-57335 JP 2003-129135 A

  By the way, when a groove is formed by irradiating a laser beam, a melt or a molten re-solidified material (hereinafter, referred to as a melt or the like) is generated in a groove of a steel sheet. When such a melt or the like is generated, stress tends to concentrate. In such a case, there is a possibility that the grain-oriented electrical steel sheet may be cracked when the grain-oriented electrical steel sheet is bent during the production of the wound iron core.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to reduce the core loss of a wound iron core and to prevent the occurrence of cracks in a steel sheet during the manufacture of a wound iron core. It is to control.

  In order to solve the above-described problems, according to an aspect of the present invention, a laser beam is irradiated in a direction intersecting with a transport direction of a steel sheet to form a grain-oriented electrical steel sheet having grooves formed at predetermined intervals in the transport direction. A wound iron core formed by winding, wherein the formation state of a groove in a corner portion of the core is different from the formation state of a groove in a portion other than the corner portion of the wound iron core, A wound iron core is provided.

  In the above-mentioned wound iron core, a first groove whose extension direction is parallel to a width direction of the steel plate is formed in a portion other than the corner portion, and the first groove is formed in the corner portion. It does not have to be.

  Further, in the above-mentioned wound iron core, a first groove is formed in a portion other than the corner portion so as to extend in a direction parallel to a plate width direction of the steel plate. The second groove may be formed so as to intersect the width direction.

  In the above-mentioned wound iron core, a depth of a groove formed in the corner portion may be smaller than a depth of a groove formed in a portion other than the corner portion.

  In the above-mentioned wound iron core, the depth of the grooves formed at predetermined intervals in the transport direction may be 0.2 times or more the width of the grooves.

  In order to solve the above problems, according to another aspect of the present invention, a step of irradiating a laser beam in a direction intersecting with the transport direction of the grain-oriented electrical steel sheet, and forming grooves at predetermined intervals in the transport direction. Forming a wound iron core by winding a steel sheet having the grooves formed therein, wherein a portion corresponding to a corner portion of the wound iron core of the directional magnetic steel sheet is provided. The method of manufacturing a wound iron core is characterized in that the formation state of the groove is different from the formation state of the groove in a portion other than the corner portion.

  As described above, according to the present invention, it is possible to suppress the occurrence of cracks in a steel sheet during the manufacture of a wound iron core, while reducing iron loss of the wound iron core.

It is a sectional view showing an example of composition of grain-oriented electrical steel sheet 10 concerning this embodiment. It is a perspective view showing an example of composition of iron core 50 concerning this embodiment. FIG. 3 is a schematic diagram showing a state in which a plurality of grain-oriented electrical steel sheets 10 constituting the wound iron core 50 of FIG. 2 are developed. It is a flowchart which shows an example of the manufacturing process of the iron core 50 which concerns on this embodiment. FIG. 2 is a schematic diagram illustrating a configuration example of a laser processing apparatus 100 according to the embodiment. It is a schematic diagram which shows the formation state of the groove | channel D in the grain-oriented electrical steel sheet 900 which concerns on a comparative example. It is a schematic diagram which shows the irradiation state of the laser beam in the corner corresponding part 34 and the non-corner corresponding part 32 of the grain-oriented electrical steel sheet 10. FIG. 3 is a schematic diagram showing a state of formation of grooves in a grain-oriented electrical steel sheet 10. It is a schematic diagram which shows the 1st modification of groove formation in a grain-oriented electrical steel sheet. It is a schematic diagram which shows the 2nd modification of groove formation in a grain-oriented electrical steel sheet.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the specification and the drawings, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.

<Overview of grain-oriented electrical steel sheets>
A grain-oriented electrical steel sheet is an electrical steel sheet in which the axes of easy magnetization of crystal grains of the steel sheet (body-centered cubic <100> direction) are substantially aligned with the rolling direction in the manufacturing process. The grain-oriented electrical steel sheet has a structure in which a plurality of magnetic domains whose magnetization is oriented in the rolling direction are arranged with a domain wall interposed therebetween. Since such a grain-oriented electrical steel sheet is easily magnetized in the rolling direction, it is suitable as an iron core material of a transformer in which the direction of the line of magnetic force flows almost uniformly.

  Transformers are generally roughly classified into stacking transformers and winding transformers. The grain-oriented electrical steel sheet according to the present embodiment is used as an iron core material of a wound transformer that is assembled into a transformer while winding deformation is applied to the steel sheet.

  FIG. 1 is a cross-sectional view illustrating an example of a configuration of a grain-oriented electrical steel sheet 10 according to the present embodiment. As shown in FIG. 1, the grain-oriented electrical steel sheet 10 includes a steel sheet main body (ground iron) 12, a glass coating 14 formed on both surfaces of the steel sheet main body 12, an insulating coating 16 formed on the glass coating 14, Having.

  The steel plate body 12 is made of an iron alloy containing Si. The composition of the steel sheet main body 12 is, for example, Si: 2.5% by mass to 4.0% by mass, C: 0.02% by mass to 0.10% by mass, Mn: 0.05% by mass to 0.1% by mass. 20% by mass or less, acid-soluble Al: 0.020% by mass to 0.040% by mass, N: 0.002% by mass to 0.012% by mass, S: 0.001% by mass to 0.010% by mass Hereinafter, P: 0.01% by mass to 0.04% by mass, with the balance being Fe and unavoidable impurities. The thickness of the steel plate body 12 is, for example, 0.15 mm or more and 0.35 mm or less.

  The glass coating 14 is made of, for example, a composite oxide such as forsterite (Mg2SiO4), spinel (MgAl2O4), and cordierite (Mg2Al4Si5O18). The thickness of the glass coating 14 is, for example, 1 μm.

  The insulating coating 16 is made of, for example, a coating liquid mainly composed of colloidal silica and a phosphate (such as magnesium phosphate and aluminum phosphate) or a coating liquid in which alumina sol and boric acid are mixed.

  The grain-oriented electrical steel sheet 10 having the above-described configuration is wound in a state where a plurality of sheets are stacked, and is used as a core 50 of a transformer (transformer) shown in FIG.

  FIG. 2 is a perspective view showing an example of the configuration of the wound iron core 50 according to the present embodiment. As shown in FIG. 2, the wound iron core 50 has a cubic shape, and a space is formed at the center side. The horizontal length of the outer periphery of the wound iron core 50 is A, the vertical length is B, and the depth length is C. The horizontal length of the inner circumference of the wound iron core 50 is a, the vertical length is b, and the depth of the inner circumference is the same as the depth of the outer circumference. The wound iron core 50 has corner portions 52 that are bent at the four corners during manufacturing. The corner portion 52 has, for example, an R shape. The wound iron core 50 is formed by stacking a plurality of grain-oriented electrical steel sheets 10 and, when expanded, becomes as shown in FIG. The X direction in FIG. 2 corresponds to the rolling direction in FIG. 3, and the Y direction in FIG. 2 corresponds to the sheet width direction in FIG.

  FIG. 3 is a schematic diagram showing a state in which a plurality of grain-oriented electrical steel sheets 10 constituting the wound iron core 50 of FIG. 2 are developed. In FIG. 3, it is assumed that the wound iron core 50 is manufactured by winding N directional electromagnetic steel sheets 10. Further, the grain-oriented electrical steel sheet 10-1 shown in FIG. 3 is located on the outermost side in the wound iron core 50, and the grain-oriented electrical steel sheet 10 -N is located on the innermost side in the wound iron core 50. The lengths of the N grain-oriented electrical steel sheets 10 in the rolling direction are different from each other. As shown in FIG. 3, the length in the rolling direction is shorter for the grain-oriented electrical steel sheet on the inner side.

  In the grain-oriented electrical steel sheet 10, in order to further reduce iron loss, a groove extending in a direction intersecting the transport direction (rolling direction) at the time of manufacturing the grain-oriented electrical steel sheet 10 is formed by a steel sheet body (ground iron) 12. Are formed at predetermined groove intervals in the rolling direction on the surface. Although details will be described later, the grooves are formed by irradiating the surface of the ground iron with a laser beam using a laser processing apparatus.

<Production method of wound iron core>
A method for manufacturing the wound iron core 50 according to the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart illustrating an example of a manufacturing process of the wound iron core 50 according to the present embodiment.

  As shown in FIG. 4, the manufacturing process of the wound iron core 50 includes a casting process S2, a hot rolling process S4, an annealing process S6, a cold rolling process S8, a decarburizing annealing process S10, and an annealing separator. It includes a coating step S12, a final annealing step S14, an insulating film forming step S16, a laser irradiation step S18, an insulating film forming step S20, and a steel sheet winding step S30.

  In the casting step S2, molten steel adjusted to a predetermined composition is supplied to a continuous casting machine to form an ingot continuously. In the hot rolling step S4, the ingot is heated to a predetermined temperature (for example, 1150 to 1400 ° C.) to perform hot rolling. Thereby, a hot-rolled material having a predetermined thickness (for example, 1.8 to 3.5 mm) is formed.

  In the annealing step S6, a heat treatment is performed on the hot-rolled material at, for example, a heating temperature of 750 to 1200 ° C. and a heating time of 30 seconds to 10 minutes. In the cold rolling step S8, the surface of the hot-rolled material is pickled and then cold-rolled. Thereby, a cold-rolled material having a predetermined thickness (for example, 0.15 to 0.35 mm) is formed.

  In the decarburizing annealing step S10, the cold-rolled material is heat-treated at, for example, a heating temperature of 700 to 900 ° C. and a heating time of 1 to 3 minutes to form a steel sheet body. On the surface of the steel plate body 12, an oxide layer mainly composed of silica (SiO2) is formed. In the annealing separator applying step S12, an annealing separator mainly composed of magnesia (MgO) is applied on the oxide layer of the steel plate body 12.

  In the final finish annealing step S14, a heat treatment is performed by inserting the steel sheet body 12 coated with the annealing separating agent into a batch type furnace in a state of being wound into a coil shape. The heat treatment conditions are, for example, a heating temperature of 1100 to 1300 ° C. and a heating time of 20 to 24 hours. At this time, so-called goth grains in which the rolling direction of the steel sheet main body 12 and the easy axis of magnetization coincide with each other are preferentially grown. As a result, a grain-oriented electrical steel sheet having a high crystal orientation (crystal orientation) after finish annealing is obtained. In the final finish annealing step S14, the oxide layer reacts with the annealing separating agent, and a glass coating 14 made of forsterite (Mg2SiO4) is formed on the surface of the steel plate body 12.

  In the insulating film forming step S16, the steel sheet main body 12 wound in a coil shape is unwound, stretched into a plate shape, and transported. Then, an insulating agent is applied and baked on the glass coating 14 formed on both surfaces of the steel plate body 12 to form an insulating coating 16. The steel plate main body 12 on which the insulating coating 16 is formed is wound into a coil shape.

  In the laser irradiation step S18, the steel plate body 12 wound up in a coil shape is unwound, stretched into a plate shape, and transported. Then, the laser beam is condensed and irradiated toward one surface of the steel sheet main body 12 by a laser irradiation apparatus described later, and the laser beam is scanned in a direction intersecting the rolling direction of the electromagnetic steel sheet conveyed in the rolling direction. Thereby, grooves extending in the cross direction are formed on the surface of the steel plate body 12 at predetermined intervals in the rolling direction. The focusing and irradiation of the laser beam may be performed from both the front surface and the back surface of the steel plate body 12.

  In the insulating film forming step S20, the insulating film 16 is formed on the steel plate body 12 in which the groove is formed, similarly to the insulating film forming step S16. That is, the second insulating film 16 is formed. Through the above-described series of steps, a grain-oriented electrical steel sheet having grooves extending in a direction intersecting the rolling direction formed on the surface of the steel sheet body (base iron) at predetermined groove intervals in the rolling direction is manufactured.

  In this manner, the glass coating 14 and the insulating coating 16 are formed on the surface of the steel sheet main body 12, and the grain-oriented electrical steel sheet 10 whose magnetic domain is controlled by laser irradiation is manufactured. That is, the above-described steps S2 to S20 are manufacturing steps of the grain-oriented electrical steel sheet 10.

  In the steel sheet winding step S30, first, the grain-oriented electromagnetic steel sheet 10 is cut by a predetermined length in the rolling direction to prepare a plurality of sheets. Then, a plurality of grain-oriented electromagnetic steel sheets 10 are wound in a stacked state, whereby the wound iron core 50 shown in FIG. 2 is manufactured.

  In the above description, the laser irradiation step S18 is performed after the insulating film forming step S16. However, the invention is not limited thereto. The laser irradiation step S18 may be performed before the insulating film forming step S16. For example, the laser irradiation step S18 may be performed after the cold rolling step S8. After the decarburizing annealing step S10, a laser irradiation step S18 may be performed. Further, after the final finish annealing step S14, a laser irradiation step S18 may be performed. In such a case, since the insulating film forming step S16 is performed after the laser irradiation step S18, the second insulating film forming step S20 becomes unnecessary, and the manufacturing process can be shortened.

<Configuration of laser processing device>
A configuration example of a laser processing apparatus 100 that forms a groove by irradiating a laser beam to the grain-oriented electrical steel sheet 10 will be described with reference to FIG. FIG. 5 is a schematic diagram illustrating a configuration example of the laser processing apparatus 100 according to the present embodiment.

  The laser processing device 100 irradiates a laser beam from above the insulating coating 16 of the grain-oriented electrical steel sheet 10 conveyed at a constant speed in the rolling direction in a cross direction intersecting the rolling direction to form a groove extending in the cross direction. Form. The intersecting direction is a direction that also intersects with the thickness direction of the steel sheet. As shown in FIG. 5, the laser processing apparatus 100 includes a plurality of laser oscillators 102, a plurality of transmission fibers 104, and a plurality of laser irradiation devices 106. In FIG. 5, three laser oscillators 102, a transmission fiber 104, and a laser irradiation device 106 are shown, but their configurations are the same.

  The laser oscillator 102 emits, for example, a high-power laser beam. The transmission fiber 104 is an optical fiber that transmits a laser beam emitted from the laser oscillator 102 to the laser irradiation device 106.

  As a type of the laser oscillator 102, a fiber laser or a disk laser is preferable from the viewpoints of being excellent in micro light-collecting characteristics and forming a narrow groove. A fiber laser or a disk laser has a wavelength in the near ultraviolet region to the near infrared region (for example, 1 μm band), so that a laser beam can be transmitted by an optical fiber, and a relatively compact laser beam is transmitted by the optical fiber. The laser processing device 100 can be realized. Further, the laser oscillator 102 may be a continuous wave laser or a pulse laser.

  The laser irradiation device 106 focuses and scans the laser beam transmitted from the laser oscillator 102 by the transmission fiber 104 onto the grain-oriented electrical steel sheet 10. Here, the condensing shape of the laser beam is an elliptical shape, for example, from the viewpoint of suppressing generation of a melt due to laser irradiation. The width over which one laser irradiation device 106 can scan a laser beam may be smaller than the width of the grain-oriented electrical steel sheet 10, but a plurality of laser irradiation devices 106 are arranged in the plate width direction as shown in FIG. Accordingly, the laser beam can be scanned over the entire width of the grain-oriented electrical steel sheet 10.

  In the above description, the condensing shape of the laser beam on the grain-oriented electrical steel sheet 10 is an elliptical shape, but is not limited to this. For example, the condensing shape of the laser beam may be a perfect circle.

In the above description, the laser oscillator 102 is a fiber laser or a disk laser. However, the present invention is not limited to this. For example, the laser oscillator 102 may be a CO ₂ laser.

<Generation of cracks due to bending of steel sheet during winding transformer manufacturing>
The grain-oriented electrical steel sheet having the groove is used as an iron core (winding iron core) of a winding transformer. Then, at the time of manufacturing the wound iron core, bending processing of the grain-oriented electrical steel sheet is performed. During such bending, the steel plate may be broken due to the groove.

  Here, as a comparative example, a directional magnetic steel sheet having grooves D perpendicular to the rolling direction (in other words, grooves D parallel to the sheet width direction) formed as shown in FIG. The crack will be described.

  FIG. 6 is a schematic diagram illustrating a state of formation of the groove D in the grain-oriented electrical steel sheet 900 according to the comparative example. In bending of a grain-oriented electrical steel sheet, the rolling direction of the steel sheet is usually bent. In FIG. 6, a groove D is formed in a corner corresponding part 910 corresponding to a corner part of a wound iron core in a grain-oriented electromagnetic steel sheet 900 in a direction parallel to the width direction of the steel sheet. The length in the rolling direction of the corner corresponding portion 910 is a length L. FIG. 6 shows that only one groove is formed in the corner corresponding portion 910 having a length L, but a plurality of grooves are actually formed. When the groove D is formed in the corner corresponding portion 910 in parallel to the width direction of the steel sheet, the width direction of the groove D is the same as the bending direction, so that the possibility of cracking of the steel sheet increases. .

  Causes of the cracking of the steel sheet include a melt or a molten re-solidified material (hereinafter, referred to as a melt or the like) generated in the groove of the steel sheet when the groove D is formed by irradiating the laser beam. When such a melt or the like is generated, the stress tends to concentrate, so that the possibility of the steel sheet breaking when bending the steel sheet is increased.

  In the grain-oriented electrical steel sheet, the groove D may be formed deeply from the viewpoint of improving iron loss and the like. In such a case, the ratio of the depth of the groove to the width of the groove increases, and cracks are likely to occur.

<Measures to suppress cracking of steel sheet>
In order to prevent the above-described cracking of the steel sheet, in the grain-oriented electrical steel sheet 10 according to the present embodiment, the formation state of the groove in a portion corresponding to the corner portion 52 of the wound iron core 50 (hereinafter, also referred to as a corner corresponding portion). However, this is different from the formation state of the groove in a portion corresponding to a portion other than the corner portion 52 of the wound iron core 50 (hereinafter, also referred to as a non-corner corresponding portion). An example of a groove formation state will be described with reference to FIGS. 7 and 8.

  FIG. 7 is a schematic diagram showing a laser beam irradiation state at the corner corresponding portion 34 and the non-corner corresponding portion 32 of the grain-oriented electrical steel sheet 10. FIG. 8 is a schematic diagram illustrating a state of formation of grooves in the grain-oriented electrical steel sheet 10. The corner corresponding portion 34 is a region having a length L in the rolling direction of the grain-oriented electrical steel sheet 10. The grain-oriented electrical steel sheet 10-1 shown in FIG. 3 is obtained by cutting a part of the grain-oriented electrical steel sheet 10 shown in FIG. 7 in the rolling direction.

  In the present embodiment, as shown in FIG. 8, the non-corner corresponding portion 32 is formed with a parallel groove D1 whose extending direction is parallel to the width direction of the steel plate. On the other hand, no parallel groove is formed in the corner corresponding portion 34. Specifically, as shown in FIG. 7, by turning off the operation of the laser irradiation device 106 for the corner corresponding portion 34, no groove is formed in the corner corresponding portion 34.

  By not forming a groove in the corner corresponding portion 34, cracking of the steel sheet due to the groove can be effectively prevented. On the other hand, since the corner corresponding portion 34 is sufficiently smaller than the non-corner corresponding portion 32, even if the groove is not formed in the corner corresponding portion 34, the groove is formed in the non-corner corresponding portion 32. 50 can suppress a decrease in the effect of improving iron loss. Therefore, according to the present embodiment, it is possible to suppress the occurrence of cracks in the grain-oriented electrical steel sheet 10 at the time of manufacturing the wound iron core 50 while reducing the core loss of the wound iron core 50. In FIG. 8, the groove is shown as a single line connected over the entire area in the plate width direction, but is not limited thereto, and the groove may be formed intermittently in the plate width direction. .

  By the way, it has been found that deepening the groove is effective for improving the iron loss improvement. Therefore, in the present embodiment, the grooves are formed so as to increase the depth without increasing the width. For example, the depth of the groove is at least 0.2 times the width of the groove. The depth of the groove is specifically about 20 μm.

  When the groove D having such a large depth is formed, the steel sheet may be cracked during bending of the grain-oriented electrical steel sheet. On the other hand, since the parallel groove D1 is not formed in the portion corresponding to the corner portion 52 of the wound iron core 50 of the grain-oriented electrical steel sheet as in the present embodiment, even if the groove depth is large, the bending process is performed. In this case, cracking of the steel sheet can be effectively suppressed.

  In the above description, while the parallel groove D1 is formed in the non-corner corresponding portion 32, the groove is not formed in the corner corresponding portion 34, but the present invention is not limited to this. For example, a groove may be formed as shown in FIGS.

  FIG. 9 is a schematic diagram showing a first modification of forming grooves in the grain-oriented electrical steel sheet 10. Also in the first modified example, the non-corner corresponding portion 32 is formed with a parallel groove D1 whose extending direction is parallel to the plate width direction, as in FIG. On the other hand, in the corner corresponding portion 34, unlike FIG. 8, a parallel groove D2 is formed. Here, the depth of the parallel groove D2 formed in the corner corresponding portion 34 is smaller than the depth of the parallel groove D1 formed in the non-corner corresponding portion 32. In the first modification, the parallel groove D1 corresponds to a first groove, and the parallel groove D2 corresponds to a second groove.

  The shallower the groove, the less likely it is for the steel plate to crack when bent. Therefore, by forming the shallow groove D2 in the corner corresponding portion 34, it is possible to suppress the occurrence of bending of the steel sheet due to the groove D2 during the manufacture of the wound iron core 50. The parallel groove D2 is formed by reducing the intensity of the laser beam irradiated by the laser irradiation device 106 (see FIG. 9). That is, the parallel groove D1 and the parallel groove D2 can be formed by one laser irradiation device 106.

  FIG. 10 is a schematic view showing a second modification of the formation of the grooves in the grain-oriented electrical steel sheet 10. Also in the second modified example, the non-corner corresponding portion 32 is formed with the parallel groove D1 whose extending direction is parallel to the plate width direction as in FIG. On the other hand, in the corner corresponding portion 34, unlike FIG. 8, an inclined groove D3 whose extending direction intersects the plate width direction is formed. In the second modification, the parallel groove D1 corresponds to the first groove, and the inclined groove D3 corresponds to the second groove.

  Since the extending direction of the inclined groove D3 intersects the plate width direction perpendicular to the bending direction at the time of bending the steel plate (in other words, since the width direction of the inclined groove D3 is not the same direction as the bending direction), At the time of manufacturing the core 50, generation of cracks in the steel sheet due to the inclined groove D3 can be suppressed. Here, a larger angle (also referred to as an inclined angle of the inclined groove) θ between the extending direction of the inclined groove and the sheet width direction is more effective for preventing cracking of the steel sheet. In the present embodiment, the inclined groove is formed such that the inclination angle θ is 15 degrees or more. The parallel groove D1 and the inclined groove D3 shown in FIG. 10 are formed by another laser irradiation device 106.

<Example>
An example for confirming the effectiveness of the grain-oriented electrical steel sheet according to the above-described embodiment will be described.

The grain-oriented electrical steel sheet according to the present example is manufactured as follows.
First, Si: 3.0% by mass, C: 0.05% by mass, Mn: 0.1% by mass, acid-soluble Al: 0.02% by mass, N: 0.01% by mass, S: 0.01% by mass %, P: 0.02% by mass, the balance being Fe and unavoidable impurities. This slab was subjected to hot rolling at 1280 ° C. to produce a hot-rolled material having a thickness of 2.3 mm. Next, heat treatment was performed on the hot-rolled material under the condition of 1000 ° C. × 1 minute. After the heat treatment, an acid washing treatment was performed, and then cold rolling was performed to produce a cold-rolled material having a thickness of 0.23 mm. This cold-rolled material was subjected to decarburization annealing at 800 ° C. for 2 minutes. Next, on both surfaces of the cold-rolled material after the decarburizing annealing, an annealed separating material containing magnesia as a main component was applied. Then, in a state where the cold-rolled material coated with the annealing separation material was wound into a coil shape, the cold-rolled material was charged into a batch-type furnace and subjected to finish annealing at 1200 ° C. for 20 hours. Thereby, a steel plate ground steel (steel plate main body 12) having a glass coating formed on the surface was produced. Next, an insulating material made of aluminum phosphate was applied on the glass film 14 and baked (850 ° C. × 1 minute) to form a first insulating film.

  Next, the steel sheet main body 12 on which the glass coating 14 and the insulating coating were formed was irradiated with a laser beam to form a groove on the surface of the steel sheet main body 12. At this time, for example, as shown in FIG. 8, a parallel groove D1 may be formed in the non-corner corresponding portion 32 of the grain-oriented electrical steel sheet 10, and no groove may be formed in the corner corresponding portion 34. Alternatively, a shallow groove D2 may be formed in the corner corresponding portion 34 as shown in FIG. 9, or an inclined groove D3 may be formed in the corner corresponding portion 34 as shown in FIG.

  Here, the laser irradiation device 106 shown in FIG. 5 was used as the laser irradiation device. The irradiation conditions were a laser beam intensity of 1000 W, a beam scanning speed of 30 m / s, and an irradiation pitch of 3 mm. The shape of the laser beam is elliptical, the rolling direction of the beam diameter is 0.1 mm, and the scanning direction of the beam diameter is 0.3 mm. Under these irradiation conditions, a groove having a width of 50 μm and a depth of 20 μm was formed.

  Next, a second insulating coating was formed on the steel plate body 12 in which the groove was formed. Thereby, a grain-oriented electrical steel sheet 10 as shown in FIG. 1 is manufactured. Then, after cutting the grooved directional electromagnetic steel sheet 10 by a predetermined length in the rolling direction, a plurality of directional electromagnetic steel sheets 10 are wound in a stacked state, whereby the wound iron core shown in FIG. 50 are manufactured.

<Summary>
As described above, in the grain-oriented electrical steel sheet 10 according to the present embodiment, the formation state of the groove in the corner corresponding portion 34 corresponding to the corner portion 52 of the wound iron core 50 is a portion other than the corner portion 52 of the wound iron core 50. Is different from the state of formation of the groove in the non-corner corresponding portion 32 corresponding to.

  Specifically, while the parallel groove D1 is formed in the non-corner corresponding portion 32, the groove is not formed in the corner corresponding portion. Alternatively, a shallow groove D2 is formed in the corner corresponding portion 34, or an inclined groove D3 is formed in the corner corresponding portion 34. Accordingly, it is possible to suppress the occurrence of cracks in the steel sheet during the manufacture of the wound iron core 50 due to the grooves formed in the corner corresponding portions 34. On the other hand, since the corner corresponding portion 34 is only a small area in the wound iron core 50, even if the groove is not formed in the corner corresponding portion 34, the non-corner corresponding portion 32 is formed with the groove. A reduction in the effect of improving the iron loss of the iron core 50 can be suppressed. Therefore, according to the present embodiment, it is possible to suppress the occurrence of cracks in the grain-oriented electrical steel sheet 10 at the time of manufacturing the wound iron core 50 while reducing the core loss of the wound iron core 50.

  As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention pertains can conceive various changes or modifications within the scope of the technical idea described in the claims. It is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Oriented electromagnetic steel sheet 12 Steel sheet main body 14 Glass coating 16 Insulating coating 32 Non-corner corresponding part 34 Corner corresponding part 50 Winding iron core 52 Corner part 100 Laser processing device 102 Laser oscillator 104 Transmission fiber 106 Laser irradiation device D1, D2, D3 Groove

Claims (6)

A laser beam is irradiated in a direction intersecting with the transport direction of the steel sheet, a wound iron core formed by winding a grain-oriented electrical steel sheet having grooves formed at predetermined intervals in the transport direction,
A wound iron core, wherein a state of formation of a groove in a corner portion of the wound iron core is different from a state of formation of a groove in a portion other than the corner portion of the wound iron core. The wound iron core according to claim 1,
In a portion other than the corner portion, a first groove whose extension direction is parallel to a width direction of the steel plate is formed,
The wound iron core, wherein the first groove is not formed in the corner portion. The wound iron core according to claim 1,
A first groove is formed in a portion other than the corner portion so that an extending direction is parallel to a width direction of the steel plate,
The wound iron core, wherein a second groove is formed in the corner portion so that an extending direction intersects the plate width direction. The wound iron core according to claim 1,
A wound iron core, wherein a depth of a groove formed in the corner portion is smaller than a depth of a groove formed in a portion other than the corner portion. The wound iron core according to any one of claims 1 to 4,
A wound iron core, wherein the depth of the grooves formed at predetermined intervals in the transport direction is at least 0.2 times the width of the grooves. A step of irradiating a laser beam in a direction intersecting with the transport direction of the grain-oriented electrical steel sheet, and forming grooves at predetermined intervals in the transport direction,
Winding a steel sheet having the groove formed thereon to form a wound iron core;
A method for manufacturing a wound iron core, comprising:
A method for manufacturing a wound iron core, wherein a state of formation of a groove in a portion corresponding to a corner of the core of the grain-oriented magnetic steel sheet is different from a state of formation of a groove in a part other than the corner. .

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