Grain-oriented electrical steel sheet and its manufacturing method

Abstract

This grain-oriented electrical steel sheet is characterized in that: the chemical composition of a base material steel sheet comprises, in mass%, Si: 2.5 to 4.5%, Mn: 0.01 to 1.00%, N: ≤ 0.01%, C: ≤ 0.01%, sol.Al: ≤ 0.01%, S: ≤ 0.01%, Se: ≤ 0.01%, P: 0.00 to 0.05%, Sb: 0.00 to 0.50%, Sn: 0.00 to 0.30%, Cr: 0.00 to 0.50%, Cu: 0.00 to 0.50%, Ni: 0.00 to 0.50%, and Bi: 0.0000 to 0.0100%, the remainder being Fe and impurities; a magnetic flux density B8 in a rolling direction of the grain-oriented electrical steel sheet is more than or equal to 1.93 T; in a direction intersecting the rolling direction of the grain-oriented electrical steel sheet, deformed regions that extend across the entire width of the grain-oriented electrical steel sheet are periodically formed at an interval L of 3-30 mm; the deformed regions have a width W of 0.2-30.6 mm; and a protruding portion having a maximum height Dprotrusion of 1-5 μm is formed on one surface of the deformed regions, and a recess portion having a maximum depth Drecess of 1-4 μm is formed on the opposite surface.

Description

[Technical Field]

[0001] The present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same. This application claims priority based on Japanese Patent Application No. 2022-060901, filed on March 31, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Grain-oriented electrical steel sheets are soft magnetic materials that are primarily used as iron core materials for transformers, and therefore require magnetic properties such as high magnetization and low core loss.

[0003] Iron loss is the power loss consumed as heat energy when an iron core is excited by an AC magnetic field, and from the perspective of energy conservation, iron loss should be as low as possible. The most important factor in determining iron loss characteristics is magnetic flux density (for example, B8: magnetic flux density in a magnetic field of 800 A / m), and the higher the magnetic flux density, the lower the iron loss. In grain-oriented electrical steel sheets, in order to increase the magnetic flux density, the crystal orientation is generally changed to the Goss orientation ({110} ) during the manufacturing process, which is good for magnetic properties. <001> By refining the magnetic domain structure of grain-oriented electrical steel sheets with high magnetic flux density, low iron loss can be achieved. To increase the degree of orientation concentration in the Goss orientation, a high-temperature, long-time finish annealing is usually performed. By finishing annealing, the {110} <001> Crystal grains that are concentrated in a certain direction, i.e., "Goss-oriented grains," grow to centimeter-order sizes while encroaching on the surrounding crystal grains (secondary recrystallization), resulting in a uniform crystal orientation (increased degree of concentration of crystal orientation).

[0004] In order to improve the orientation density, the techniques described in Patent Documents 1 to 3 involve rapid heating during the temperature-raising step of the decarburization annealing process, which enriches the steel sheet with Goss-oriented grains that serve as nuclei for secondary recrystallization. After secondary recrystallization, a large number of grains with a small deviation from the Goss orientation are formed. This crystalline structure achieves high magnetic flux density. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-62436 [Patent Document 2] Japanese Patent Application Publication No. 10-280040 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-096520 Summary of the Invention [Problem to be solved by the invention]

[0006] Specific methods for rapidly heating steel sheets include current heating and induction heating. However, to further reduce iron loss using the above-mentioned conventional techniques, the heating rate must be increased. This requires larger equipment, which increases facility and manufacturing costs. Furthermore, temperature unevenness within the steel sheet may become more pronounced, which may lead to deterioration of the steel sheet shape and variations in the magnetic properties of the final product. Furthermore, while increasing the heating rate compared to conventional methods enriches Goss-oriented grains, which serve as nuclei for secondary recrystallization, the {111} orientation, which promotes the growth of Goss-oriented grains during the secondary recrystallization process, also increases the temperature unevenness. <112> The oriented grains decrease. Thus, simply increasing the heating rate has limitations in terms of increasing the degree of orientation and achieving high magnetic flux density. Furthermore, when grain-oriented electrical steel sheets are used as iron core materials for transformers, it is also important to increase the space factor. Here, the space factor is roughly the ratio of the total volume of grain-oriented electrical steel sheets to the total volume (including gaps) of the laminate formed by stacking several grain-oriented electrical steel sheets.

[0007] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a grain-oriented electrical steel sheet that can be used to manufacture iron cores having high magnetic flux density and a high space factor, and a method for manufacturing the same. [Means for solving the problem]

[0008] In order to solve the above problems, according to one aspect of the present invention, there is provided a grain-oriented electrical steel sheet, wherein the chemical composition of the base steel sheet is, in mass %, Si: 2.5 to 4.5%, Mn: 0.01 to 1.00%, N: 0.01% or less, C: 0.01% or less, sol.Al: 0.01% or less, S: 0.01% or less, Se: 0.01% or less, P: 0.00 to 0.05%, Sb: 0.00 to 0.50%, Sn: 0.00 to 0.30%, Cr: 0.00 to 0.50%, Cu: 0.00 to 0.05%. The grain-oriented electrical steel sheet has a magnetic flux density B8 of 1.93 T or more in the rolling direction, and deformation regions extending across the entire width of the grain-oriented electrical steel sheet are periodically formed at intervals L of 3 mm or more and 30 mm or less in a direction intersecting the rolling direction of the grain-oriented electrical steel sheet, the width W of the deformation region being 0.2 mm or more and 30.6 mm or less, and one side of the deformation region has a maximum height D 凸 On the other side, a convex portion with a maximum depth D 凹 The grain-oriented electrical steel sheet is characterized in that recesses having a size of 1 μm or more and 4 μm or less are formed.

[0009] According to another aspect of the present invention, there is provided a grain-oriented electrical steel sheet, the chemical composition of the base steel sheet being, in mass %, Si: 2.5 to 4.5%, Mn: 0.01 to 1.00%, N: 0.01% or less, C: 0.01% or less, sol.Al: 0.01% or less, S: 0.01% or less, Se: 0.01% or less, P: 0.00 to 0.05%, Sb: 0.00 to 0.50%, Sn: 0.00 to 0.30%, Cr: 0.00 to 0.50%, Cu: 0.00 to 0.50%, N The grain-oriented electrical steel sheet has a magnetic flux density B8 of 1.93 T or more in the rolling direction thereof, and deformation regions extending across the entire width of the grain-oriented electrical steel sheet are periodically formed at intervals L of 3 mm or more and 30 mm or less in a direction intersecting the rolling direction thereof, the width W of the deformation region being 0.2 mm or more and 30.6 mm or less, and one side of the deformation region has a maximum height D 凸 On the other side, a convex portion with a maximum depth of D凹 The concave portion is formed with a size of 1 μm or more and 8 μm or less, and the steepness of the convex portion is 2D 凸 / W is 0.0001 or more and less than 0.0050.

[0010] Furthermore, within the deformation region, the ratio of the area of ​​crystal grains whose crystal orientation deviates from the Goss orientation by 15° or more to the total area of ​​the deformation region may be 5% or less.

[0011] The chemical composition of the base steel sheet may contain, in mass %, one or more elements selected from the group consisting of P: 0.01-0.05%, Sb: 0.01-0.50%, Sn: 0.01-0.30%, Cr: 0.01-0.50%, Cu: 0.01-0.50%, Ni: 0.01-0.50%, and Bi: 0.0001-0.0100%.

[0012] According to another aspect of the present invention, a method for manufacturing a steel sheet comprising the steps of: heating a slab having a chemical composition, in mass%, containing 2.5 to 4.5% Si, 0.01 to 1.00% Mn, 0.01 to 0.02% N, 0.02 to 0.10% C, 0.01 to 0.05% sol. Al, 0.01 to 0.05% S and / or Se in total, 0.01 to 0.05%, 0.00 to 0.05% P, 0.00 to 0.30% Sn, 0.00 to 0.50% Sb, 0.00 to 0.50% Cr, 0.00 to 0.50% Cu, 0.00 to 0.50% Ni, and 0.0000 to 0.0100% Bi, with the balance being Fe and impurities; and hot pressing the heated slab. a hot rolling process in which the hot rolled steel sheet is cold-rolled to obtain a hot rolled steel sheet; a hot rolled sheet annealing process in which the hot rolled steel sheet after the hot rolled sheet annealing process is cold-rolled to obtain a cold rolled steel sheet; a decarburization annealing process in which the cold rolled steel sheet is decarburized and annealed to obtain a decarburization annealed steel sheet; a finish annealing process in which an annealing separator is applied to the decarburization annealed steel sheet and then finish annealed to form a glass film on the surface of the decarburization annealed steel sheet to obtain a finish annealed sheet; and an insulating film forming process in which an insulating film forming liquid is applied to the finish annealed sheet and then heat treated to form an insulating film on the surface of the finish annealed sheet, 2 More than 1.2kg / mm2 For a cold-rolled steel sheet heated to a temperature of 200 ° C or more and 550 ° C or less under the following tension, in a direction intersecting the rolling direction, at an interval L within the range shown in the following formula (1), across the entire width of the cold-rolled steel sheet, Irradiating with a laser beam or an electron beam, cold rolled steel plate one side The method includes a partial rapid heating step in which the surface is partially rapidly heated, and a heating step in which the cold-rolled steel sheet after the partial rapid heating step is heated in a non-oxidizing atmosphere from a temperature range of 550°C or less to a temperature range of 750 to 950°C at an average heating rate of 5°C / sec or more and 2000°C / sec or less, and the steel sheet is placed in the partial rapid heating section where partial rapid heating is performed. The laser beam or the electron beam Provided is a method for producing a grain-oriented electrical steel sheet, characterized in that the following formulas (2) to (4) are satisfied when the average strength is P (W), the diameter in the rolling direction of the partially rapidly heated portion is Dl (mm), the diameter in the sheet width direction of the partially rapidly heated portion is Dc (mm), the scanning speed in the sheet width direction of the partially rapidly heated portion is Vc (mm / s), the irradiation energy density is Up = 4 / π × P / (Dl × Vc), and the instantaneous power density is Ip = 4 / π × P / (Dl × Dc). 3mm≦L≦30mm (1) L / 50≦Dl≦L / 2 (2) 5J / mm 2 ≦Up≦48J / mm 2 (3) 0.05kW / mm 2 ≦Ip≦4.99kW / mm 2 (4)

[0013] Here, the irradiation energy density Up may further satisfy the following formula (5). 5J / mm 2 ≦Up<62.5×DlJ / mm 2 (5)

[0014] The chemical composition of the slab may also contain, in mass %, one or more elements selected from the group consisting of P: 0.01-0.05%, Sn: 0.01-0.30%, Sb: 0.01-0.50%, Cr: 0.01-0.50%, Cu: 0.01-0.50%, Ni: 0.01-0.50%, and Bi: 0.0001-0.0100%. [Effects of the Invention]

[0015] According to the above-described aspects of the present invention, it is possible to provide a grain-oriented electrical steel sheet that can be used to manufacture an iron core having a high magnetic flux density and a high space factor, and a method for manufacturing the same. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an explanatory diagram showing the appearance of a grain-oriented electrical steel sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] <1. Investigation by the present inventors> Hereinafter, embodiments of the present invention will be described. First, the investigations conducted by the present inventors will be described. In response to the above-mentioned problems, the present inventors have conducted research and development of a new rapid heating technology. As a result, the present inventors have found that by applying various heating methods, such as laser beam, electron beam, infrared heating, dielectric heating, microwave heating, arc heating, plasma heating, induction heating, and current resistance heating, to a portion of the steel sheet, particularly by instantaneously heating the outermost surface and the surface layer (from the outermost surface to approximately 1 / 5t (t: sheet thickness) layer), it is possible to effectively enrich the Goss orientation in the steel sheet. Furthermore, by appropriately setting the annealing temperature rise rate for regions other than the partially heated region of this method, it is possible to enrich the Goss orientation in the region other than the partially heated region (including the region from the surface layer of the steel sheet to the back side of the heated surface). <112> As a result, it is possible to realize a grain-oriented electrical steel sheet with excellent magnetic properties.

[0018] However, the above-mentioned manufacturing method of grain-oriented electrical steel sheet has a problem that the shape of the heated area is deteriorated (i.e., it is significantly deformed) because the steel sheet is subjected to partial rapid heating, and the space factor is reduced. In other words, when this grain-oriented electrical steel sheet is used in a transformer, it does not sufficiently contribute to improving the efficiency of the transformer.

[0019] Therefore, the present inventors conducted extensive research into a manufacturing method for grain-oriented electrical steel sheet that can achieve both good magnetic properties and sheet shape even when the steel sheet is subjected to partial rapid heating, and as a result, they obtained the following findings.

[0020] <2. Method of manufacturing grain-oriented electrical steel sheets> The method for manufacturing a grain-oriented electrical steel sheet according to this embodiment includes the following steps. (1) a hot rolling process in which a slab having a predetermined composition is heated and the heated slab is hot-rolled to form a hot-rolled steel sheet; (2) a hot-rolled steel sheet annealing process for annealing the hot-rolled steel sheet; (3) A cold rolling process in which the hot-rolled steel sheet after the hot-rolled sheet annealing process is cold-rolled to obtain a cold-rolled steel sheet; (4) a decarburization annealing step of subjecting the cold-rolled steel sheet to decarburization annealing to obtain a decarburization annealed steel sheet; (5) a finish annealing process in which an annealing separator is applied to the decarburized annealed steel sheet, and then finish annealing is performed to form a glass film on the surface of the decarburized annealed steel sheet to obtain a finish annealed sheet; (6) An insulating film forming process in which an insulating film forming liquid is applied to the finish-annealed sheet and then heat-treated to form an insulating film on the surface of the finish-annealed sheet. Each step will be described below. For steps or conditions not described, known steps and conditions can be applied.

[0021] (2-1. Hot rolling process) In the hot rolling process, a slab having a predetermined composition is heated, and the heated slab is hot-rolled to obtain a hot-rolled steel sheet. The heating temperature is not particularly limited, but is preferably 1100°C or higher. If the heating temperature is lower than 1100°C, inclusions formed in the slab cannot be dissolved, and there is a possibility that inhibitors will not be sufficiently formed in the hot rolling process or the hot-rolled sheet annealing process described below. Therefore, it is preferable that the slab heating temperature be 1100°C or higher. There is no upper limit for the slab heating temperature, but if the slab is heated at a temperature higher than 1450°C, the slab may melt, making hot rolling difficult. Therefore, the slab heating temperature is preferably 1450°C or lower.

[0022] The hot rolling conditions are not particularly limited and may be appropriately set based on the desired properties. The thickness of the hot rolled steel sheet obtained by hot rolling is preferably within the range of 1.0 mm to 4.0 mm, for example.

[0023] (2-2. Chemical composition of the slab) In order to obtain desirable magnetic properties for grain-oriented electrical steel sheets, the chemical composition of the slab to be subjected to hot rolling is set to the following range. In the following description, unless otherwise specified, the notation "%" represents "mass %" relative to the total mass of the slab.

[0024] Si: 2.5 to 4.5% Silicon (Si) is an extremely effective element for increasing the electrical resistance (resistivity) of steel and reducing eddy current loss, which constitutes part of iron loss. If the Si content of the slab is less than 2.5%, the resistivity is low and eddy current loss cannot be sufficiently reduced. Furthermore, the steel undergoes phase transformation during finish annealing, preventing secondary recrystallization from progressing sufficiently, making it difficult to achieve good magnetic flux density and low iron loss. Therefore, the Si content of the slab is set to 2.5% or more. The Si content of the slab is preferably 2.6% or more, and more preferably 2.7% or more.

[0025] On the other hand, if the Si content exceeds 4.5%, the steel sheet becomes embrittled and the sheet passing property during the manufacturing process deteriorates significantly. Therefore, the Si content of the slab is set to 4.5% or less. The Si content of the slab is preferably 4.4% or less, and more preferably 4.2% or less.

[0026] Mn: 0.01 to 1.00% Mn (manganese) is an important element that forms MnS or MnSe, which are major inhibitors. If the Mn content of the slab is less than 0.01%, the absolute amount of MnS or MnSe required to cause secondary recrystallization is insufficient. Therefore, the Mn content of the slab is set to 0.01% or more. The Mn content is preferably 0.03% or more, and more preferably 0.06% or more.

[0027] On the other hand, if the Mn content of the slab exceeds 1.00%, the steel undergoes phase transformation during finish annealing, secondary recrystallization does not proceed sufficiently, and good magnetic flux density and low iron loss cannot be obtained. Therefore, the Mn content of the slab is set to 1.00% or less. The Mn content is preferably 0.98% or less, and more preferably 0.96% or less.

[0028] N: 0.01 to 0.02% N (nitrogen) is an element that reacts with sol.Al (acid-soluble aluminum), which will be described later, to form AlN, which functions as an inhibitor. To form a sufficient amount of AlN, which functions as an inhibitor, the N content is set to 0.01% or more.

[0029] On the other hand, if the N content exceeds 0.02%, blisters (voids) are formed in the steel sheet during cold rolling, and the strength of the steel sheet increases, resulting in poor sheet threadability during production. Therefore, the N content of the slab is set to 0.020% or less.

[0030] C: 0.02 to 0.10% Carbon (C) is an element that improves magnetic flux density. However, if the C content of the slab exceeds 0.10%, productivity in the decarburization annealing process decreases. Furthermore, if the C content of the slab is high and decarburization is insufficient, the steel undergoes phase transformation during secondary recrystallization annealing (i.e., finish annealing), and secondary recrystallization does not proceed sufficiently. This prevents good magnetic flux density and low iron loss, and magnetic properties deteriorate due to magnetic aging. Therefore, the C content of the slab is set to 0.10% or less. A lower C content is preferable for productivity and reduced iron loss. From the viewpoints of productivity and reduced iron loss, the C content is preferably 0.09% or less, and more preferably 0.08% or less.

[0031] On the other hand, if the C content of the slab is less than 0.02%, the effect of improving the magnetic flux density cannot be obtained. Therefore, the C content of the slab is set to 0.02% or more. The C content is preferably 0.04% or more, and more preferably 0.06% or more.

[0032] sol.Al: 0.01-0.05% Sol-Al (acid-soluble aluminum) is a constituent element of the main inhibitor among compounds called inhibitors that affect secondary recrystallization in grain-oriented electrical steel sheets, and is an essential element in the base steel sheet according to this embodiment from the viewpoint of secondary recrystallization occurrence. If the sol-Al content of the slab is less than 0.01%, AlN, which functions as an inhibitor, is not sufficiently generated, resulting in insufficient secondary recrystallization. Therefore, the sol-Al content is set to 0.01% or more. The sol-Al content is preferably 0.02% or more.

[0033] On the other hand, if the sol.Al content exceeds 0.05%, AlN, which functions as an inhibitor, is not generated sufficiently, resulting in insufficient secondary recrystallization. Therefore, the sol.Al content is set to 0.05% or less. The sol.Al content is preferably 0.04% or less, and more preferably 0.03% or less.

[0034] S and Se: 0.01 to 0.05% S (sulfur) and Se (selenium) are important elements that react with the above-mentioned Mn to form the inhibitors MnS and MnSe. Since it is sufficient to form MnS or MnSe as the inhibitor, one of S and Se may be contained in the slab, or both may be contained in the slab. If the total content of one or both of S and Se is less than 0.01%, sufficient inhibitors will not be formed. Therefore, the total content of one or both of S and Se is set to 0.01% or more. The total content of one or both of S and Se is preferably 0.02% or more.

[0035] On the other hand, if the total content of one or both of S and Se exceeds 0.05%, it causes hot embrittlement and makes hot rolling extremely difficult. Therefore, the total content of one or both of S and Se is set to 0.05% or less. The total content of one or both of S and Se is preferably 0.04% or less, and more preferably 0.03% or less.

[0036] In addition to the elements mentioned above, the slab may contain one or more of the optional additional elements listed below.

[0037] P: 0.00 to 0.05% P (phosphorus) is an element that reduces workability in rolling. By setting the P content to 0.05% or less, excessive reduction in rolling workability can be prevented, and fractures during manufacturing can be suppressed. From this perspective, the P content is set to 0.05% or less. The P content is preferably 0.04% or less, and more preferably 0.03% or less.

[0038] The lower limit of the P content is not limited and may include 0.00%, but P is also an element that has the effect of improving the texture and magnetic properties. To obtain this effect, the P content may be 0.005% or more, or 0.01% or more.

[0039] Sn: 0.00 to 0.30% Sn (tin) is an element that has the effect of improving magnetic properties. Therefore, Sn may be contained in the slab. When Sn is contained, the Sn content is preferably 0.01% or more to effectively exhibit the effect of improving magnetic properties. In consideration of achieving both magnetic properties and coating adhesion, the Sn content is preferably 0.03% or more, and more preferably 0.05% or more.

[0040] On the other hand, if the Sn content exceeds 0.30%, the glass coating deteriorates significantly and sufficient tension for magnetic domain refinement is not obtained, resulting in poor core loss characteristics. Therefore, the Sn content is set to 0.30% or less. The Sn content is preferably 0.20% or less, and more preferably 0.10% or less.

[0041] Sb: 0.00 to 0.50% Sb (antimony) is an element that has the effect of improving magnetic properties. Therefore, it may be contained in the slab. When Sb is contained, the Sb content is preferably 0.01% or more in order to effectively exhibit the effect of improving magnetic properties. The Sb content is more preferably 0.02% or more. On the other hand, if the Sb content exceeds 0.50%, the adhesion of the glass film deteriorates. Therefore, the Sb content is set to 0.50% or less, and preferably 0.40% or less.

[0042] Cr: 0.00~0.50% Like Sn and Cu (described later), Cr (chromium) is an element that contributes to increasing the Goss orientation occupancy rate in the secondary recrystallized structure, thereby improving magnetic properties, and also contributes to improving the adhesion of the glass coating. Therefore, Cr may be contained in the slab. To achieve the above effects, the Cr content is preferably 0.01% or more, more preferably 0.02% or more, and even more preferably 0.03% or more.

[0043] On the other hand, if the Cr content exceeds 0.50%, Cr oxides are formed, resulting in a deterioration in magnetic properties. Therefore, the Cr content is set to 0.50% or less. The Cr content is preferably 0.30% or less, and more preferably 0.10% or less.

[0044] Cu: 0.00 to 0.50% Cu (copper) is an element that contributes to increasing the Goss orientation occupancy rate in the secondary recrystallization structure and also contributes to improving the adhesion of the glass coating. Therefore, it may be added. To obtain the above effects, the Cu content is preferably 0.01% or more. The Cu content is more preferably 0.02% or more, and even more preferably 0.03% or more.

[0045] On the other hand, if the Cu content exceeds 0.50%, the steel sheet becomes embrittled during hot rolling. Therefore, the Cu content of the slab is set to 0.50% or less. The Cu content is preferably 0.30% or less, and more preferably 0.10% or less.

[0046] Ni: 0.00 to 0.50% Ni (nickel) is an element effective in increasing electrical resistance and reducing iron loss. Ni is also an element effective in controlling the metal structure of a hot-rolled steel sheet and improving its magnetic properties. Therefore, Ni may be contained. To obtain the above effects, the Ni content is preferably 0.01% or more. The Ni content is more preferably 0.02% or more.

[0047] On the other hand, if the Ni content exceeds 0.50%, secondary recrystallization may become unstable. Therefore, the Ni content is set to 0.50% or less, and preferably 0.30% or less.

[0048] Bi: 0.0000 to 0.0100% Bi has the effect of strengthening the inhibitor function and improving magnetic properties. However, if the Bi content exceeds 0.0100%, Bi has a negative effect on glass film formation, so the Bi content is preferably 0.0100% or less. The Bi content is preferably 0.0050% or less, and more preferably 0.0030% or less. The lower limit of the Bi content may be 0%, but since the above-mentioned effects can be expected, the Bi content may be 0.0001% or more, or even 0.0005% or more.

[0049] Remainder: Fe and impurities The chemical composition of the slab used in the method for producing a grain-oriented electrical steel sheet according to this embodiment may contain the above-mentioned elements, with the balance being Fe and impurities. Here, the impurities refer to elements that are mixed in from raw materials such as ore or scrap, or from the production environment, during industrial production of the base steel sheet, and that are permissible to be contained in amounts that do not adversely affect the function of the grain-oriented electrical steel sheet according to this embodiment.

[0050] The chemical compositions of the slabs described above can be measured by common analytical methods. For example, the steel compositions can be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). C and S can be measured using the combustion-infrared absorption method, N can be measured using the inert gas fusion-thermal conductivity method, and O can be measured using the inert gas fusion-non-dispersive infrared absorption method.

[0051] (2-3. Hot-rolled sheet annealing process) The hot-rolled steel sheet annealing process is a process of annealing the hot-rolled steel sheet manufactured through the hot rolling process. By performing such annealing treatment, recrystallization occurs in the steel sheet structure, making it possible to achieve good magnetic properties.

[0052] In the hot-rolled steel sheet annealing step of this embodiment, the hot-rolled steel sheet manufactured through the hot rolling step may be annealed according to a known method. The means for heating the hot-rolled steel sheet during annealing is not particularly limited, and known heating methods can be adopted. The annealing conditions are also not particularly limited, but for example, the hot-rolled steel sheet may be annealed in a temperature range of 900 to 1200°C for 10 seconds to 5 minutes.

[0053] (2-4. Cold rolling process) In the cold rolling process, the hot-rolled steel sheet after the hot-rolled sheet annealing process is subjected to cold rolling including multiple passes to obtain a cold-rolled steel sheet. The cold rolling may be a single cold rolling, or may be multiple cold rolling passes in which the cold rolling is interrupted before the final pass of the cold rolling process and at least one or two intermediate annealings are performed between the cold rolling passes. In addition, the type of rolling mill used in the cold rolling is not limited, and may be a tandem rolling mill, a reverse rolling mill, or a rolling method combining these.

[0054] When intermediate annealing is performed, it is preferable to hold the steel sheet at a temperature of 1000 to 1200°C for 5 to 180 seconds. The annealing atmosphere is not particularly limited. In consideration of production costs, the number of times intermediate annealing is performed is preferably three or less. Furthermore, before the cold rolling step, the surface of the hot-rolled steel sheet may be pickled under known conditions.

[0055] (2-5. Decarburization annealing process) In the decarburization annealing process, the cold-rolled steel sheet is subjected to decarburization annealing to produce a decarburization annealed steel sheet. In the decarburization annealing process, the cold-rolled steel sheet undergoes primary recrystallization and carbon, which adversely affects magnetic properties, is removed from the steel sheet. Details of the decarburization annealing process will be described later.

[0056] (2-6. Finish annealing process) In the final annealing step, a predetermined annealing separator is applied to one or both sides of the decarburized annealed steel sheet obtained in the decarburization annealing step, and then the steel sheet is subjected to final annealing. In this way, a final annealed sheet is produced. <001> Crystal grains that are concentrated in a certain orientation, i.e., "Goss-oriented grains," grow to centimeter-order sizes while encroaching on the surrounding crystal grains (secondary recrystallization), resulting in a uniform crystal orientation (increased orientation concentration). Finish annealing is generally performed for a long period of time while the steel sheet is wound into a coil. Therefore, prior to finish annealing, an annealing separator is applied to the decarburized annealed steel sheet and then dried to prevent seizure between the inside and outside of the coil windings.

[0057] The annealing separator to be applied is one that contains MgO as its main component (for example, at a weight fraction of 80% or more). By using an annealing separator that contains MgO as its main component, a glass film can be formed on the surface of the base steel sheet. If MgO is not the main component, the glass film will not be formed. This is because the glass film is an Mg2SiO4 or MgAl2O4 compound, and if MgO is not the main component, there will be a shortage of Mg, which is necessary for the formation reaction. The glass film may or may not be formed.

[0058] The finish annealing may be carried out, for example, in an atmospheric gas containing hydrogen and nitrogen, by raising the temperature to 1150 to 1250°C and annealing at that temperature range for 10 to 60 hours.

[0059] (2-7. Insulation film forming process) In the insulating film forming process, an insulating film forming solution is applied to a finish-annealed steel sheet, and then a heat treatment is performed to form an insulating film on the surface of the finish-annealed steel sheet. This heat treatment forms an insulating film on the surface of the finish-annealed steel sheet. For example, the insulating film forming solution may contain colloidal silica and phosphate. The insulating film forming solution may also contain chromium. Furthermore, to reduce iron loss, a magnetic domain refining process may be performed after the insulating film is formed. For example, a mechanical distortion such as a groove may be imparted using a roller or the like, or a linear thermal distortion may be imparted using a laser or the like.

[0060] (2-8. Details of the decarburization annealing process) Next, the decarburization annealing step will be described in detail. The decarburization annealing step includes a partial rapid heating step and a temperature increasing step. (2-8-1. Partial rapid heating process) The partial rapid heating process was carried out in a non-oxidizing atmosphere at a rate of 0.2 kg / mm 2 More than 1.2kg / mm 2 A cold-rolled steel sheet is heated to a temperature of 200°C or more and 550°C or less under the following tension, and the surface of the cold-rolled steel sheet is rapidly heated partially across the entire width of the cold-rolled steel sheet in a direction intersecting the rolling direction (for example, 30 to 150 degrees, preferably 60 to 120 degrees, more preferably 80 to 100 degrees, and more preferably a direction approximately perpendicular to the rolling direction (90 degrees)) at an interval L within the range shown in the following formula (1). 3mm≦L≦30mm (1)

[0061] The non-oxidizing atmosphere is, for example, a nitrogen atmosphere. As long as the hydrogen gas content in the atmosphere is less than 4% by volume, the atmosphere may contain 100 ppm or less of oxygen. If the atmosphere in the partial rapid heating step is not a non-oxidizing atmosphere, magnetic deterioration due to oxidation of the portion irradiated with the laser (partial rapid heating portion), which will be described later, and magnetic deterioration due to oxidation during heating of the cold-rolled steel sheet may occur.

[0062] The heating temperature of the cold-rolled steel sheet is 200°C or higher and lower than 550°C. If the heating temperature of the cold-rolled steel sheet is lower than 200°C, the shape of the cold-rolled steel sheet may be deteriorated due to insufficient temperature. Furthermore, if the heating temperature of the cold-rolled steel sheet exceeds 550°C, magnetic deterioration due to recovery may occur. The heating temperature of the cold-rolled steel sheet is preferably 250°C or higher, more preferably 300°C or higher. The heating temperature of the cold-rolled steel sheet is preferably 500°C or lower, more preferably 450°C or lower.

[0063] The tension applied to the cold-rolled steel sheet is 0.2 kg / mm ​​in the rolling direction (sheet running direction). 2 More than 1.2kg / mm 2 The tension is 0.2 kg / mm ​​or less. 2 If the tension is less than 1.2 kg / mm, the shape of the cold-rolled steel sheet may deteriorate due to insufficient tension. 2 If the tension exceeds 0.3 kg / mm, magnetic deterioration may occur. 2 More preferably, it is 0.4 kg / mm 2 The tension is preferably 1.1 kg / mm 2 and more preferably 1.0 kg / mm 2 is.

[0064] Specific means for partially and rapidly heating a cold-rolled steel sheet include, for example, irradiation with a laser beam or an electron beam (hereinafter, these will be collectively referred to as "beam"), infrared heating, dielectric heating, microwave heating, arc heating, plasma heating, induction heating, and current resistance heating. In this embodiment, the surface of the cold-rolled steel sheet is partially and rapidly heated by irradiating the cold-rolled steel sheet with a beam at an interval L across the entire width thereof. Here, the interval L is 3 mm or more and 30 mm or less. If the interval L is less than 3 mm, the effect of this embodiment cannot be obtained. If the interval L exceeds 30 mm, the effect of this embodiment is reduced.

[0065] The distance L is preferably 5 mm or more, and more preferably 7 mm or more. The distance L is preferably 25 mm or less, and more preferably 20 mm or less.

[0066] Furthermore, when the intensity input to a partial rapid heating section (e.g., a laser focusing section) where partial rapid heating is performed is P (W), the rolling direction diameter of the partial rapid heating section (e.g., the diameter in the rolling direction among the laser focusing diameters) is Dl (mm), the sheet width direction diameter of the partial rapid heating section (e.g., the diameter in the sheet width direction among the laser focusing diameters) is Dc (mm), the sheet width direction scanning speed of the partial rapid heating section (e.g., the laser scanning speed) is Vc (mm / s), the irradiation energy density is Up=4 / π×P / (Dl×Vc), and the instantaneous power density is Ip=4 / π×P / (Dl×Dc), the following formulas (2) to (4) are satisfied. L / 50≦Dl≦L / 2 (2) 5J / mm 2 ≦Up≦48J / mm 2 (3) 0.05kW / mm 2 ≦Ip≦4.99kW / mm 2 (4)

[0067] The beam diameter Dl is between L / 50 and L / 2. If the beam diameter Dl is less than L / 50, the partially rapidly heated area will be insufficient, resulting in insufficient secondary recrystallization nuclei and poor secondary recrystallization. If the beam diameter Dl exceeds 2 / L, the partially rapidly heated area will be excessive, resulting in insufficient orientation to promote the growth of secondary recrystallization nuclei and poor secondary recrystallization orientation.

[0068] The light collection diameter Dl is preferably L / 25 or more, and more preferably 3L / 50 or more. The light collection diameter Dl is preferably 9L / 20 or less, and more preferably 2L / 5 or less.

[0069] The irradiation energy density Up is expressed as 4 / π×P / (Dl×Vc), and is 5J / mm 2 More than 48J / mm 2 The irradiation energy density is set to 5 J / mm or less. 2 If the irradiation energy density is less than 48 J / mm, the recrystallization and grain growth of the steel sheet surface will not progress sufficiently, and the effect of rapid heating will not be obtained. 2If the irradiation energy density exceeds 48 J / mm, the structure of the steel sheet surface becomes significantly coarse due to excessive heat input, resulting in secondary recrystallization defects. 2 It is limited to the following:

[0070] The irradiation energy density Up is preferably 45 J / mm 2 or less, and more preferably 40 J / mm 2 More preferably, it is 62.5×DlJ / mm or less. 2 That is, it is preferable that the irradiation energy density Up further satisfies the following formula (5): 5J / mm 2 ≦Up<62.5×DlJ / mm 2 (5)

[0071] The irradiation energy density Up is preferably 7 J / mm 2 More preferably, 9 J / mm 2 That's all.

[0072] The instantaneous power density is expressed as Ip = 4 / π × P / (Dl × Dc), which is 0.05 kW / mm 2 Over 4.99kW / mm 2 The instantaneous power density is 0.05kW / mm 2 If the instantaneous power density is less than 4.99 kW / mm, the effect of rapid heating will not be obtained and the magnetism will be inferior. 2 If it exceeds this limit, scratches will appear on the steel plate.

[0073] The instantaneous power density is preferably 0.07 kW / mm 2 More preferably, it is 0.09 kW / mm 2 The instantaneous power density is preferably 4.0 kW / mm 2 More preferably, it is 3.0 kW / mm 2 The following is the result.

[0074] (2-8-2. Heating process) In the heating process, the cold-rolled steel sheet after the partial rapid heating process is heated in a non-oxidizing atmosphere from a temperature range of 550°C or less to a temperature range of 750 to 950°C at an average heating rate of 5°C / s or more and 2000°C / s or less. If the temperature of the cold-rolled steel sheet after the partial rapid heating process is higher than the temperature at the start of the heating process, the cold-rolled steel sheet is temporarily cooled. Here, the average refers to the time average. If the heating rate is less than 5°C / s, the correspondence orientation that promotes the growth of secondary recrystallization nuclei becomes excessive, resulting in inferior magnetic properties. If the heating rate exceeds 2000°C / s, the correspondence orientation decreases, resulting in inferior magnetic properties.

[0075] The decarburization annealing process removes carbon, which adversely affects magnetic properties, from the steel sheet, and enriches the Goss orientation in the surface layer of the laser-irradiated area. <112> Furthermore, deformation of the laser-irradiated portion can be suppressed, and the space factor can be increased. Therefore, according to this embodiment, it is possible to provide a method for manufacturing a grain-oriented electrical steel sheet that can achieve both good magnetic properties and a good sheet shape, even when the steel sheet is subjected to partial rapid heating using a laser beam, an electron beam, or the like.

[0076] (2-9. Nitriding) In addition to the above-described treatments, a nitriding treatment may be performed. The nitriding treatment may be performed, for example, after the decarburization is completed in the decarburization annealing step. The nitriding treatment may be performed under well-known conditions. For example, preferred nitriding conditions are as follows. Nitriding temperature: 700~850℃ Atmosphere inside the nitriding furnace (nitriding atmosphere): An atmosphere containing gases with nitriding properties such as hydrogen, nitrogen, and ammonia

[0077] If the nitriding temperature is 700°C or higher or 850°C or lower, nitrogen easily penetrates into the steel sheet during nitriding. If nitriding is performed within this temperature range, the amount of nitrogen inside the steel sheet can be preferably secured. Therefore, fine AlN is preferably formed in the steel sheet before secondary recrystallization. As a result, secondary recrystallization is preferably exhibited during finish annealing. The time for which the steel sheet is held at the nitriding temperature is not particularly limited, but may be, for example, 10 to 60 seconds.

[0078] <3. Composition of grain-oriented electrical steel sheets> (3-1.Chemical composition) Next, the structure of the grain-oriented electrical steel sheet manufactured by the above-mentioned manufacturing method of grain-oriented electrical steel sheet will be described. First, the chemical composition of the grain-oriented electrical steel sheet will be described. In the following description, unless otherwise specified, the notation "%" represents "mass %" with respect to the total mass of the base steel sheet. The base steel sheet refers to the steel sheet portion of the grain-oriented electrical steel sheet.

[0079] Si: 2.5 to 4.5% Silicon (Si) is an extremely effective element for increasing the electrical resistance (resistivity) of steel and reducing eddy current loss, which constitutes part of iron loss. If the Si content of the base steel sheet is less than 2.5%, the resistivity is low and eddy current loss cannot be sufficiently reduced. Furthermore, the steel undergoes phase transformation during secondary recrystallization annealing, which prevents sufficient secondary recrystallization, making it difficult to achieve good magnetic flux density and low iron loss. Therefore, the Si content of the base steel sheet is set to 2.5% or more. The Si content of the slab is preferably 2.6% or more, and more preferably 2.7% or more.

[0080] On the other hand, if the Si content exceeds 4.5%, the steel sheet becomes embrittled and the sheet passing property during the manufacturing process deteriorates significantly. Therefore, the Si content of the base steel sheet is set to 4.5% or less. The Si content of the base steel sheet is preferably 4.4% or less, and more preferably 4.2% or less.

[0081] Mn: 0.01 to 1.00% In grain-oriented electrical steel sheets, Mn exists as solute Mn. Solute Mn increases resistivity and can reduce iron loss. For this reason, grain-oriented electrical steel sheets may contain Mn at a content of 0.01 to 1.00%. However, solute Mn has a smaller effect of increasing resistivity than Si, and the content is also small, so the effect is limited.

[0082] N: 0.01% or less As mentioned above, N is a raw material for AlN, which is an inhibitor, but it is also an element that adversely affects the magnetic properties of grain-oriented electrical steel sheets, so it is preferable to keep the N content as low as possible. In this embodiment, the N content is set to 0.01% or less. The lower limit includes 0, but since it is industrially difficult to achieve a completely zero N content, the substantial lower limit is about 0.0005%.

[0083] C: 0.01% or less Since C is an element that adversely affects the magnetic properties of grain-oriented electrical steel sheets, it is preferable that its content be as low as possible. In this embodiment, the C content is set to 0.01% or less. The lower limit includes 0, but since it is industrially difficult to make it completely 0, the substantial lower limit is about 0.0005%.

[0084] Sol.Al: 0.01% or less As mentioned above, sol. Al is a raw material for AlN, which is an inhibitor. However, since it is also an element that adversely affects the magnetic properties of grain-oriented electrical steel sheets, it is preferable that the amount of sol. Al is as small as possible. In this embodiment, the sol. Al content is set to 0.01% or less. The lower limit includes 0, but since it is industrially difficult to achieve a completely zero content, the practical lower limit is about 0.0005%.

[0085] S: 0.01% or less, Se: 0.01% or less S and Se are raw materials for the inhibitors MnS and MnSe, but they also have a negative effect on the magnetic properties of grain-oriented electrical steel sheets, so it is preferable to keep their contents as low as possible. In this embodiment, the S and Se contents are set to 0.01% or less. The lower limit includes 0, but since it is industrially difficult to achieve a completely zero content, the substantial lower limit is about 0.0005%.

[0086] The grain-oriented electrical steel sheet may further contain, as optional additional elements, one or more selected from the group consisting of P: 0.00-0.05%, Sb: 0.00-0.50%, Sn: 0.00-0.30%, Cr: 0.00-0.50%, Cu: 0.00-0.50%, Ni: 0.00-0.50%, and Bi: 0.0000-0.0100%. The preferred contents and properties of these elements are as described above. The remainder of the grain-oriented electrical steel sheet is iron and impurities. The definition of impurities is as described above.

[0087] The chemical compositions of the base steel sheet described above may be measured by a common analytical method. For example, the steel compositions may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). C and S may be measured using the combustion-infrared absorption method, N may be measured using the inert gas fusion-thermal conductivity method, and O may be measured using the inert gas fusion-non-dispersive infrared absorption method.

[0088] (3-2. Characteristics of Grain-Oriented Electrical Steel Sheets) The magnetic flux density B8 of the grain-oriented electrical steel sheet in the rolling direction is 1.93 T or more. As such, the grain-oriented electrical steel sheet according to this embodiment has high magnetic properties. The magnetic flux density B8 of the grain-oriented electrical steel sheet in the rolling direction is preferably 1.94 T or more, and more preferably 1.95 T or more. In order to achieve a magnetic flux density B8 of 1.94 T or more, for example, the irradiation energy density Up is set to 5 to 41 J / mm 2 The temperature increase rate in the temperature increase step may be set to 20 to 1500° C. / second.

[0089] Deformation regions are periodically formed across the entire width of the grain-oriented electrical steel sheet at intervals L of 3 mm or more and 30 mm or less in a direction intersecting the rolling direction of the grain-oriented electrical steel sheet (for example, at an angle of 30 to 150 degrees relative to the rolling direction). These deformation regions are formed by the decarburization annealing process described above. The width W of the deformation region is 0.2 mm or more and 30.6 mm or less. One side of the deformation region has a maximum height D 凸 On the other side, a convex portion with a maximum depth of D 凹 A depression with a maximum height of 4 μm or less is formed on one side of the deformation region. 凸 On the other side, a convex portion with a maximum depth of D 凹 The concave portion is 8 μm or less, and the convex portion has a steepness of 2D 凸 / W is 0.0001 or more and less than 0.0050. In this way, the degree of deformation in the deformation region, which is the region irradiated with the laser, is kept low, making it possible to increase the space factor. The appearance of the grain-oriented electrical steel sheet is shown in Figure 1(a) and Figure 1(b). Figure 1(a) is a plan view of the grain-oriented electrical steel sheet, and Figure 1(b) is a side cross-sectional view of the deformation region (a cross-sectional view perpendicular to the surface of the grain-oriented electrical steel sheet). Maximum height D 凸 and maximum depth D 凹 The lower limit of this is about 1 μm when partial rapid heating is applied, since some deformation of the steel sheet occurs. The symbol T in Figure 1(b) indicates the thickness of the grain-oriented electrical steel sheet.

[0090] Here, the maximum height D 凸 A convex portion of 8 μm or less is formed on the opposite surface, and the maximum depth D 凹 When a concave portion of 8 μm or less is formed, the steepness of the convex portion 2D 凸 It is preferable that / W is 0.0001 or more and less than 0.0050. In this case, the space factor can be further increased. 凸 In order to make / W 0.0001 or more and less than 0.0050, for example, in the above-mentioned decarburization annealing step, Up is set to 62.5 × DlJ / mm 2 The maximum height D on one side of the deformation area 凸 On the other side, a convex portion of 5 μm or less is formed, and the maximum depth D 凹When a recess of 4 μm or less is formed, the steepness 2D 凸 In other words, according to the method for manufacturing the grain-oriented electrical steel sheet described above, the maximum height D 凸 is at least 8 μm or less, and the maximum depth D 凹 The maximum height of the convex part D is 8 μm or less. 凸 exceeds 5 μm, or the maximum depth D 凹 If the value exceeds 4 μm, the steepness 2D 凸 It is preferable that / W is 0.0001 or more and less than 0.0050. When calculating the steepness, the maximum height D 凸 The unit of is set to mm to match the unit of the width W of the deformation area, and then the steepness is calculated.

[0091] Furthermore, it is preferable that the ratio (area ratio) of the area of ​​crystal grains (abnormal grains) whose crystal orientation deviates from the Goss orientation by 15° or more to the total area of ​​the deformation region is 5% or less. This further improves the magnetic properties of the grain-oriented electrical steel sheet. To obtain such a crystal orientation, for example, in the above-mentioned decarburization annealing step, Up is set to 48 J / mm 2 The following would suffice.

[0092] Therefore, the grain-oriented electrical steel sheet according to this embodiment can achieve both good magnetic properties and sheet shape. That is, the grain-oriented electrical steel sheet according to this embodiment can be used to manufacture an iron core having a high magnetic flux density and a high space factor. [Example]

[0093] <1. Example 1> Next, the effects of one embodiment of the present invention will be explained in more detail using examples, but the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples. Various conditions can be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

[0094] A slab was prepared having a chemical composition, in mass %, of C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.02%, sol. Al: 0.03%, N: 0.01%, with the remainder being Fe and impurities.

[0095] This slab was heated to 1350°C in a heating furnace. The heated slab was subjected to a hot rolling process to produce a hot-rolled steel sheet with a thickness of 2.3 mm. The hot-rolled steel sheet was annealed in a hot-rolled sheet annealing process, and then cold-rolled to produce a cold-rolled steel sheet with a thickness of 0.22 mm. The cold-rolled steel sheet after the cold rolling process was subjected to a decarburization annealing process. In this decarburization annealing process, before heating, one side of the steel sheet was subjected to partial rapid heating using a laser beam under the conditions shown in Tables 1A to 1C. In Example 1, the focusing diameter Dl in the rolling direction and the laser irradiation interval L were varied. The laser scanning direction was set to 90 degrees relative to the rolling direction. At this time, the focusing diameter Dc in the width direction and the scanning speed Vc were adjusted so that the irradiation energy density Up and instantaneous power density Ip did not fluctuate.

[0096] After partial rapid heating, the steel sheet was heated in a non-oxidizing atmosphere containing hydrogen and nitrogen at the heating rates shown in Tables 1D to 1F to cause primary recrystallization, and then the decarburization annealing temperature was set to 830°C and soaked for 60 seconds. At this time, the atmosphere in the heat treatment furnace where the decarburization annealing treatment was performed was a humid atmosphere containing hydrogen and nitrogen. After decarburization annealing, an annealing separator (water slurry) mainly composed of MgO was applied to the surface of the steel sheet, and then the steel sheet was wound into a coil. The coiled steel sheet was subjected to finish annealing.

[0097] The steel sheets after the final annealing process were subjected to an insulating film forming process. In the insulating film forming process, an insulating coating agent mainly composed of colloidal silica and phosphate was applied to the surface (on the glass film) of the grain-oriented electrical steel sheet after the final annealing process, and then baked. In this way, an insulating film, which is a tension insulating film, was formed on the glass film. Grain-oriented electrical steel sheets of each test number were manufactured using the above manufacturing process.

[0098] (1-1. Removal of the film) The chemical composition of the base steel sheet can be measured by a known elemental analysis method. First, the primary coating (glass coating) and secondary coating (insulating coating) are removed from the base steel sheet by the following method. Specifically, the grain-oriented electrical steel sheet with the secondary coating is removed by immersing it in a high-temperature alkaline solution. The composition, temperature, and immersion time of the alkaline solution can be adjusted as appropriate. For example, the grain-oriented electrical steel sheet with the secondary coating is immersed in a sodium hydroxide aqueous solution of 30 to 50 mass% NaOH and 50 to 70 mass% HO at 80 to 90°C for 5 to 10 minutes, and then rinsed and dried. This process removes the secondary coating from the grain-oriented electrical steel sheet.

[0099] Furthermore, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in high-temperature hydrochloric acid to remove the coating. The concentration, temperature, and immersion time of the hydrochloric acid may be adjusted as appropriate. For example, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in 30 to 40 mass % hydrochloric acid at 80 to 90°C for 1 to 5 minutes, and then rinsed with water and dried. Through these steps, a base steel sheet from which the secondary coating and primary coating have been removed is obtained.

[0100] (1-2. Chemical composition measurement test of base steel plate) The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet of each test number was measured by the following method. First, the primary coating and secondary coating of the grain-oriented electrical steel sheet were removed by the above-mentioned method to extract the base steel sheet. Using the base steel sheet, the chemical composition of the base steel sheet was analyzed based on the following [Method for measuring the chemical composition of steel sheet]. Chips were collected from the obtained base steel plate. The collected chips were dissolved in acid to obtain a solution. The solution was subjected to ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) to perform elemental analysis of the chemical composition. The C content and S content were determined by the well-known high-frequency combustion method (combustion-infrared absorption method). The N content was determined using the well-known inert gas fusion-thermal conductivity method. Specifically, the measurements were performed using a Shimadzu component analyzer (product name: ICPS-8000).

[0101] As a result of the analysis, in Example 1, the chemical composition of the base steel plate for all test numbers contained, in mass%, C: 0.01% or less, Si: 3.3%, Mn: 0.08%, S: 0.01% or less, sol.Al: 0.01% or less, N: 0.01% or less, with the remainder being Fe and impurities.

[0102] The magnetic properties (magnetic flux density B8 value) of the grain-oriented electrical steel sheets of each test number were evaluated in accordance with JIS C2556 (2015). The obtained magnetic flux densities B8 are shown in Tables 1D to 1F.

[0103] The shape of the deformed area of ​​the grain-oriented electrical steel sheet of each test number was measured by the following method. That is, a commercially available surface roughness measuring device (SE3500, manufactured by Kosaka Laboratory) was used, the stylus of the detection part was SE2555N (tip curvature radius 2 μm), the measurement length in the rolling direction was 15 mm per measurement, and the surface roughness was measured five times consecutively for a total length of 75 mm. The measurements were carried out on both the front and back. Within the measurement range on the front and back, W and D were measured at five points on each side. 凸 , D 凹 The width W of the deformation area and the maximum depth D of the depression on one side of the deformation area were measured and evaluated based on the average value. 凹 and the maximum height D of the convex part on the rear side of the deformation area 凸 are shown in Tables 1D to 1F.

[0104] Furthermore, the space factor of the grain-oriented electrical steel sheet of each test number was evaluated in accordance with JIS C2550-5 (2020). The obtained space factors are shown in Tables 1D to 1F.

[0105] Furthermore, the area ratio of abnormal grains in the deformed region of the grain-oriented electrical steel sheet of each test number was measured using the following method. Specifically, using a Laue diffractometer, the crystal orientation was measured in the width direction of the grain-oriented electrical steel sheet at 2 mm intervals in the region of width W of the deformed region along the longitudinal centerline of the deformed region. Then, the number of measurement points showing abnormal grains with a deviation angle of 15° or more from the Goss orientation was extracted from the crystal orientation of each measurement point, and the ratio of these measurement points to the total number of measurement points was defined as the area ratio of abnormal grains. However, for steel Nos. that had magnetically inferior strengths of less than 1.93 T in the magnetic property measurements described above, the area ratio of abnormal grains measured using the Laue diffractometer was not performed. The obtained area ratios of abnormal grains are shown in Tables 1D to 1F.

[0106] Referring to Tables 1A to 1F, steels Nos. 1 to 10 had a small laser irradiation interval L, which resulted in an excessive laser effect, and the magnetic flux density was inferior at less than 1.93 T.

[0107] Steel Nos. 61 to 70 had a large laser irradiation interval L, so the laser irradiation effect was small and the magnetic properties were inferior, less than 1.93 T.

[0108] In steels Nos. 11, 21, 31, 41, and 51, the focused beam diameter Dl in the rolling direction was small compared to the laser irradiation interval L, so the size of the rapidly heated portion was insufficient and the magnetic flux density was inferior at less than 1.93 T.

[0109] Steels Nos. 20, 30, 40, 50, and 60 had a large focused beam diameter Dl in the rolling direction relative to the laser irradiation interval L, resulting in excessively rapid heated portions and inferior magnetic flux densities of less than 1.93 T. For the steel Nos. other than those mentioned above, all manufacturing process conditions were appropriate, and therefore the magnetic flux density was excellent at 1.93 T or more, and the space factor was also high at 96% or more.

[0110] [Table 1A]

[0111] [Table 1B]

[0112] [Table 1C]

[0113] [Table 1D]

[0114] [Table 1E]

[0115] [Table 1F]

[0116] <2. Example 2> A slab was prepared having a chemical composition, in mass %, of C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.02%, sol. Al: 0.03%, N: 0.01%, with the remainder being Fe and impurities.

[0117] This slab was heated to 1350°C in a heating furnace. The heated slab was subjected to a hot rolling process to produce a hot-rolled steel sheet with a thickness of 2.3 mm. The hot-rolled steel sheet was annealed in a hot-rolled sheet annealing process, and then cold-rolled to produce a cold-rolled steel sheet with a thickness of 0.22 mm. The cold-rolled steel sheet after the cold rolling process was subjected to a decarburization annealing process. In this decarburization annealing process, before heating, one side of the steel sheet was subjected to partial rapid heating using a laser beam under the conditions shown in Tables 2A to 2C. The laser scanning direction was set at 90° with respect to the rolling direction. At this time, the focused beam diameter Dc in the width direction and the scanning speed Vc were changed so as to vary the irradiation energy density Up and the instantaneous power density Ip.

[0118] After partial rapid heating, the steel sheet was heated in a non-oxidizing atmosphere containing hydrogen and nitrogen at the heating rates shown in Tables 2D to 2F to cause primary recrystallization, and then the decarburization annealing temperature was set to 830°C and soaked for 60 seconds. At this time, the atmosphere in the heat treatment furnace where the decarburization annealing treatment was performed was a humid atmosphere containing hydrogen and nitrogen. After decarburization annealing, an annealing separator (water slurry) mainly composed of MgO was applied to the surface of the steel sheet, and then the steel sheet was wound into a coil. The coiled steel sheet was subjected to finish annealing.

[0119] The steel sheets after the final annealing process were subjected to an insulating film forming process. In the insulating film forming process, an insulating coating agent mainly composed of colloidal silica and phosphate was applied to the surface (on the glass film) of the grain-oriented electrical steel sheet after the final annealing process, and then baked. In this way, an insulating film, which is a tension insulating film, was formed on the glass film. Grain-oriented electrical steel sheets of each test number were manufactured using the above manufacturing process.

[0120] (2-1. Removal of the film) The chemical composition of the base steel sheet can be measured by a known elemental analysis method. First, the primary coating and secondary coating are removed from the base steel sheet by the following method. Specifically, the grain-oriented electrical steel sheet with the secondary coating is removed by immersing it in a high-temperature alkaline solution. The composition, temperature, and immersion time of the alkaline solution can be adjusted as appropriate. For example, the grain-oriented electrical steel sheet with the secondary coating is immersed in a sodium hydroxide aqueous solution of 30 to 50 mass% NaOH and 50 to 70 mass% H2O at 80 to 90°C for 5 to 10 minutes, and then rinsed and dried. This process removes the secondary coating from the grain-oriented electrical steel sheet. Furthermore, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in high-temperature hydrochloric acid to remove the coating. The concentration, temperature, and immersion time of the hydrochloric acid may be adjusted as appropriate. For example, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in 30 to 40 mass % hydrochloric acid at 80 to 90°C for 1 to 5 minutes, and then rinsed with water and dried. Through these steps, a base steel sheet from which the secondary coating and primary coating have been removed is obtained. (2-2. Chemical composition measurement test of base steel plate) The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet of each test number was measured by the following method. First, the primary coating and secondary coating of the grain-oriented electrical steel sheet were removed by the above-mentioned method to extract the base steel sheet. Using the base steel sheet, the chemical composition of the base steel sheet was analyzed based on the following [Method for measuring the chemical composition of steel sheet]. Chips were collected from the obtained base steel plate. The collected chips were dissolved in acid to obtain a solution. The solution was subjected to ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) to perform elemental analysis of the chemical composition. The C content and S content were determined by the well-known high-frequency combustion method (combustion-infrared absorption method). The N content was determined using the well-known inert gas fusion-thermal conductivity method. Specifically, the measurements were performed using a Shimadzu component analyzer (product name: ICPS-8000).

[0121] As a result of the analysis, in Example 2, the chemical composition of the base steel plate for all test numbers contained, in mass%, C: 0.01% or less, Si: 3.3%, Mn: 0.08%, S: 0.01% or less, sol.Al: 0.01% or less, N: 0.01% or less, with the remainder being Fe and impurities.

[0122] The magnetic properties (magnetic flux density B8 value) of the grain-oriented electrical steel sheets of each test number were evaluated in accordance with JIS C2556 (2015). The obtained magnetic flux densities B8 are shown in Tables 2D to 2F.

[0123] The shape of the deformed area of ​​the grain-oriented electrical steel sheet of each test number was measured by the following method. That is, a commercially available surface roughness measuring device (SE3500, manufactured by Kosaka Laboratory) was used, the stylus of the detection part was SE2555N (tip curvature radius 2 μm), the measurement length in the rolling direction was 15 mm per measurement, and the surface roughness was measured five times consecutively for a total length of 75 mm. The measurements were carried out on both the front and back. Within the measurement range on the front and back, W and D were measured at five points on each side. 凸 , D 凹The average value of these values ​​was used for evaluation. However, for steel No. 1, where Ip was excessive and scratches were clearly present in the laser irradiated area, evaluation with a roughness meter was not performed. The width W of the deformed area and the maximum depth D of the recess on one side of the deformed area were calculated. 凹 and the maximum height D of the convex part on the rear side of the deformation area 凸 are shown in Tables 2D to 2F.

[0124] Furthermore, the space factor of the grain-oriented electrical steel sheet of each test number was evaluated in accordance with JIS C2550-5 (2020). The obtained space factors are shown in Tables 2D to 2F.

[0125] Furthermore, the area ratio of abnormal grains in the deformed region of the grain-oriented electrical steel sheet of each test number was measured using the following method. Specifically, using a Laue diffractometer, the crystal orientation was measured in the width direction of the grain-oriented electrical steel sheet at 2 mm intervals in the width direction of the deformed region along the center line of the longitudinal direction of the deformed region in an area of ​​width W. Then, the number of measurement points showing abnormal grains with a deviation angle of 15° or more from the Goss orientation was extracted from the crystal orientation of each measurement point, and the ratio of these measurement points to the total number of measurement points was defined as the area ratio of abnormal grains. However, for steel Nos. that had magnetically inferior strengths of less than 1.93 T in the magnetic property measurements described above, the area ratio of abnormal grains measured using the Laue diffractometer was not performed. The obtained area ratios of abnormal grains are shown in Tables 2D to 2F.

[0126] Referring to Tables 2A to 2F, steels Nos. 1 to 10 had a low instantaneous power density Ip, a small rapid heating effect by laser heating, and a magnetic flux density of less than 1.93 T, which was inferior.

[0127] Steel Nos. 61 to 70 had a high instantaneous power density Ip, and significant defects were generated due to laser heating, which resulted in a deterioration in magnetic flux density and an inferior value of less than 1.93 T.

[0128] Steels Nos. 11, 21, 31, 41, and 51 had a low irradiation energy density Up, a small rapid heating effect due to laser heating, and a magnetic flux density of less than 1.93 T, making them inferior.

[0129] Steels No. 10, 20, 30, 40, 50, and 60 had a high irradiation energy density Up, resulting in excessive heat input due to laser heating, and were inferior with a magnetic flux density of less than 1.93 T.

[0130] Steel Nos. 7-9, 17-19, 27-29, 37-39, 47-49, and 57-59 had a large irradiation energy density Up relative to the focused diameter Dl, and a large steepness. The D convexity was also large, significantly degrading the space factor, resulting in an inferior result of less than 96%. The manufacturing process conditions for all other steel Nos. were appropriate, resulting in an excellent magnetic flux density of 1.93 T or more and a high space factor of 96% or more. [Table 2A]

[0131] [Table 2B]

[0132] [Table 2C]

[0133] [Table 2D]

[0134] [Table 2E]

[0135] [Table 2F]

[0136] <3. Example 3> A slab was prepared having a chemical composition, in mass %, of C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.02%, sol. Al: 0.03%, N: 0.01%, with the remainder being Fe and impurities.

[0137] This slab was heated to 1350°C in a heating furnace. The heated slab was subjected to a hot rolling process to produce a hot-rolled steel sheet with a thickness of 2.3 mm. The hot-rolled steel sheet was annealed in a hot-rolled sheet annealing process, and then cold-rolled to produce a cold-rolled steel sheet with a thickness of 0.22 mm. The cold-rolled steel sheet after the cold rolling process was subjected to a decarburization annealing process. In this decarburization annealing process, before heating, one side of the steel sheet was subjected to partial rapid heating using a laser beam under the conditions shown in Tables 3A to 3C. The laser scanning direction was set at 90° with respect to the rolling direction. At this time, the focal diameter Dc in the width direction and the scanning speed Vc were changed so as to vary the irradiation energy density Up and the instantaneous power density Ip. The differences from Example 2 are the focal diameter Dl in the rolling direction and the scanning speed Vc.

[0138] After partial rapid heating, the steel sheet was heated in a non-oxidizing atmosphere containing hydrogen and nitrogen at the heating rates shown in Tables 3D to 3F to cause primary recrystallization, and then the decarburization annealing temperature was set to 830°C and soaked for 60 seconds. At this time, the atmosphere in the heat treatment furnace where the decarburization annealing treatment was performed was a humid atmosphere containing hydrogen and nitrogen. After decarburization annealing, an annealing separator (water slurry) mainly composed of MgO was applied to the surface of the steel sheet, and then the steel sheet was wound into a coil. The coiled steel sheet was subjected to finish annealing.

[0139] The steel sheets after the final annealing process were subjected to an insulating film forming process. In the insulating film forming process, an insulating coating agent mainly composed of colloidal silica and phosphate was applied to the surface (on the glass film) of the grain-oriented electrical steel sheet after the final annealing process, and then baked. In this way, an insulating film, which is a tension insulating film, was formed on the glass film. Grain-oriented electrical steel sheets of each test number were manufactured using the above manufacturing process.

[0140] (3-1. Removal of the film) The chemical composition of the base steel sheet can be measured by a known elemental analysis method. First, the primary coating and secondary coating are removed from the base steel sheet by the following method. Specifically, the grain-oriented electrical steel sheet with the secondary coating is removed by immersing it in a high-temperature alkaline solution. The composition, temperature, and immersion time of the alkaline solution can be adjusted as appropriate. For example, the grain-oriented electrical steel sheet with the secondary coating is immersed in a sodium hydroxide aqueous solution of 30 to 50 mass% NaOH and 50 to 70 mass% H2O at 80 to 90°C for 5 to 10 minutes, and then rinsed and dried. This process removes the secondary coating from the grain-oriented electrical steel sheet.

[0141] Furthermore, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in high-temperature hydrochloric acid to remove the coating. The concentration, temperature, and immersion time of the hydrochloric acid may be adjusted as appropriate. For example, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in 30 to 40 mass % hydrochloric acid at 80 to 90°C for 1 to 5 minutes, and then rinsed with water and dried. Through these steps, a base steel sheet from which the secondary coating and primary coating have been removed is obtained.

[0142] (3-2. Chemical composition measurement test of base steel plate) The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet of each test number was measured by the following method. First, the primary coating and secondary coating of the grain-oriented electrical steel sheet were removed by the above-mentioned method to extract the base steel sheet. Using the base steel sheet, the chemical composition of the base steel sheet was analyzed based on the following [Method for measuring the chemical composition of steel sheet]. Chips were collected from the obtained base steel plate. The collected chips were dissolved in acid to obtain a solution. The solution was subjected to ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) to perform elemental analysis of the chemical composition. The C content and S content were determined by the well-known high-frequency combustion method (combustion-infrared absorption method). The N content was determined using the well-known inert gas fusion-thermal conductivity method. Specifically, the measurements were performed using a Shimadzu component analyzer (product name: ICPS-8000).

[0143] As a result of the analysis, in Example 3, the chemical composition of the base steel plate for all test numbers contained, in mass%, C: 0.01% or less, Si: 3.3%, Mn: 0.08%, S: 0.01% or less, sol.Al: 0.01% or less, N: 0.01% or less, with the remainder being Fe and impurities.

[0144] The magnetic properties (magnetic flux density B8 value) of the grain-oriented electrical steel sheets of each test number were evaluated in accordance with JIS C2556 (2015). The obtained magnetic flux densities B8 are shown in Tables 3D to 3F.

[0145] The shape of the deformed area of ​​the grain-oriented electrical steel sheet of each test number was measured by the following method. That is, a commercially available surface roughness measuring device (SE3500, manufactured by Kosaka Laboratory) was used, the stylus of the detection part was SE2555N (tip curvature radius 2 μm), the measurement length in the rolling direction was 15 mm per measurement, and the surface roughness was measured five times consecutively for a total length of 75 mm. The measurements were carried out on both the front and back. Within the measurement range on the front and back, W and D were measured at five points on each side. 凸 , D 凹 The average value of these values ​​was used for evaluation. However, for steel No. 1, where Ip was excessive and scratches were clearly present in the deformed area, evaluation with a roughness meter was not performed. The width W of the deformed area and the maximum depth D of the recess on one side of the deformed area were calculated. 凹 and the maximum height D of the convex part on the rear side of the deformation area 凸 are shown in Tables 3D to 3F.

[0146] Furthermore, the space factor of the grain-oriented electrical steel sheet of each test number was evaluated in accordance with JIS C2550-5 (2020). The obtained space factors are shown in Tables 3D to 3F.

[0147] Furthermore, the area ratio of abnormal grains in the deformed region of the grain-oriented electrical steel sheet of each test number was measured using the following method. Specifically, using a Laue diffractometer, the crystal orientation was measured in the width direction of the grain-oriented electrical steel sheet at 2 mm intervals in the width direction of the deformed region along the center line of the longitudinal direction of the deformed region in an area of ​​width W. Then, the number of measurement points showing abnormal grains with a deviation angle of 15° or more from the Goss orientation was extracted from the crystal orientation of each measurement point, and the ratio of these measurement points to the total number of measurement points was defined as the area ratio of abnormal grains. However, for steel Nos. that had magnetically inferior strengths of less than 1.93 T in the magnetic property measurements described above, the area ratio of abnormal grains measured using the Laue diffractometer was not performed. The obtained area ratios of abnormal grains are shown in Tables 3D to 3F.

[0148] Referring to Tables 3A to 3F, steels Nos. 1 to 10 had a low instantaneous power density Ip, a small rapid heating effect by laser heating, and a magnetic flux density of less than 1.93 T, which was inferior.

[0149] Steel Nos. 61 to 70 had a high instantaneous power density Ip, and significant defects were generated due to laser heating, which resulted in a deterioration in magnetic flux density and an inferior value of less than 1.93 T.

[0150] Steels Nos. 11, 21, 31, 41, and 51 had a low irradiation energy density Up, a small rapid heating effect due to laser heating, and a magnetic flux density of less than 1.93 T, making them inferior.

[0151] Steels Nos. 10, 20, 30, 40, 50, and 60 had a high irradiation energy density Up, which resulted in excessive heat input due to laser heating, and the magnetic flux density deteriorated to less than 1.93T.

[0152] For the steel Nos. other than those mentioned above, all manufacturing process conditions were appropriate, and therefore the magnetic flux density was excellent at 1.93 T or more, and the space factor was also high at 96% or more.

[0153] [Table 3A]

[0154] [Table 3B]

[0155] [Table 3C]

[0156] [Table 3D]

[0157] [Table 3E]

[0158] [Table 3F]

[0159] <4. Example 4> A slab was prepared having a chemical composition, in mass %, of C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.02%, sol. Al: 0.03%, N: 0.01%, with the remainder being Fe and impurities.

[0160] This slab was heated to 1350°C in a heating furnace. The heated slab was subjected to a hot rolling process to produce a hot-rolled steel sheet with a thickness of 2.3 mm. The hot-rolled steel sheet was subjected to a hot-rolled sheet annealing process in which annealing was performed, and then cold rolling was performed to produce a cold-rolled steel sheet with a thickness of 0.22 mm. The cold-rolled steel sheet after the cold rolling process was subjected to a decarburization annealing process. In this decarburization annealing process, before heating, partial rapid heating was performed on one side of the steel sheet using a laser beam under the conditions shown in Table 4A. The laser scanning direction was at an angle of 90 degrees to the rolling direction.

[0161] After partial rapid heating, the steel sheet was heated in a non-oxidizing atmosphere containing hydrogen and nitrogen at the heating rate shown in Table 4B to cause primary recrystallization, and then the decarburization annealing temperature was set to 830°C and soaked for 60 seconds. In Example 4, the heating rate was varied. At this time, the atmosphere in the heat treatment furnace where the decarburization annealing treatment was performed was a humid atmosphere containing hydrogen and nitrogen. An annealing separator (water slurry) mainly composed of MgO was applied to the surface of the steel sheet after decarburization annealing, and the steel sheet was then wound into a coil. The coiled steel sheet was then subjected to finish annealing.

[0162] The steel sheets after the final annealing process were subjected to an insulating film forming process. In the insulating film forming process, an insulating coating agent mainly composed of colloidal silica and phosphate was applied to the surface (on the glass film) of the grain-oriented electrical steel sheet after the final annealing process, and then baked. In this way, an insulating film, which is a tension insulating film, was formed on the glass film. Grain-oriented electrical steel sheets of each test number were manufactured using the above manufacturing process.

[0163] (4-1. Removal of the film) The chemical composition of the base steel sheet can be measured by a known elemental analysis method. First, the primary coating and secondary coating are removed from the base steel sheet by the following method. Specifically, the grain-oriented electrical steel sheet with the secondary coating is removed by immersing it in a high-temperature alkaline solution. The composition, temperature, and immersion time of the alkaline solution can be adjusted as appropriate. For example, the grain-oriented electrical steel sheet with the secondary coating is immersed in a sodium hydroxide aqueous solution of 30 to 50 mass% NaOH and 50 to 70 mass% H2O at 80 to 90°C for 5 to 10 minutes, and then rinsed and dried. This process removes the secondary coating from the grain-oriented electrical steel sheet.

[0164] Furthermore, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in high-temperature hydrochloric acid to remove the coating. The concentration, temperature, and immersion time of the hydrochloric acid may be adjusted as appropriate. For example, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in 30 to 40 mass % hydrochloric acid at 80 to 90°C for 1 to 5 minutes, and then rinsed with water and dried. Through these steps, a base steel sheet from which the secondary coating and primary coating have been removed is obtained.

[0165] (4-2. Chemical composition measurement test of base steel plate) The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet of each test number was measured by the following method. First, the primary coating and secondary coating of the grain-oriented electrical steel sheet were removed by the above-mentioned method to extract the base steel sheet. Using the base steel sheet, the chemical composition of the base steel sheet was analyzed based on the following [Method for measuring the chemical composition of steel sheet]. Chips were collected from the obtained base steel plate. The collected chips were dissolved in acid to obtain a solution. The solution was subjected to ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) to perform elemental analysis of the chemical composition. The C content and S content were determined by the well-known high-frequency combustion method (combustion-infrared absorption method). The N content was determined using the well-known inert gas fusion-thermal conductivity method. Specifically, the measurements were performed using a Shimadzu component analyzer (product name: ICPS-8000).

[0166] As a result of the analysis, in Example 4, the chemical composition of the base steel plate for all test numbers contained, in mass%, C: 0.01% or less, Si: 3.3%, Mn: 0.08%, S: 0.01% or less, sol.Al: 0.01% or less, N: 0.01% or less, with the remainder being Fe and impurities.

[0167] The magnetic properties (magnetic flux density B8 value) of the grain-oriented electrical steel sheets of each test number were evaluated in accordance with JIS C2556 (2015). The obtained magnetic flux density B8 values ​​are shown in Table 4B.

[0168] The shape of the deformed area of ​​the grain-oriented electrical steel sheet of each test number was measured by the following method. That is, a commercially available surface roughness measuring device (SE3500, manufactured by Kosaka Laboratory) was used, the stylus of the detection part was SE2555N (tip curvature radius 2 μm), the measurement length in the rolling direction was 15 mm per measurement, and the surface roughness was measured five times consecutively for a total length of 75 mm. The measurements were carried out on both the front and back. Within the measurement range on the front and back, W and D were measured at five points on each side. 凸 , D 凹The width W of the deformation area and the maximum depth D of the depression on one side of the deformation area were measured and evaluated based on the average value. 凹 and the maximum height D of the convex part on the rear side of the deformation area 凸 is shown in Table 4B.

[0169] Furthermore, the space factor of the grain-oriented electrical steel sheet of each test number was evaluated in accordance with JIS C2550-5 (2020). The obtained space factors are shown in Table 4B.

[0170] Furthermore, the area ratio of abnormal grains in the deformed region of each grain-oriented electrical steel sheet was measured using the following method. Specifically, using a Laue diffractometer, the crystal orientation was measured in the width direction of the grain-oriented electrical steel sheet at 2 mm intervals along the center line of the deformation region in the longitudinal direction of the deformation region in an area of ​​width W. Then, the number of measurement points showing abnormal grains with a deviation angle of 15° or more from the Goss orientation was extracted from the crystal orientation of each measurement point, and the ratio of these measurement points to the total number of measurement points was defined as the area ratio of abnormal grains. However, for steel No. 1, which had a magnetically inferior strength of less than 1.93 T in the magnetic property measurements described above, the area ratio of abnormal grains measured using the Laue diffractometer was not performed. The obtained area ratios of abnormal grains are shown in Table 4B.

[0171] Referring to Tables 4A and 4B, in Steels Nos. 1, 14 and 27, the heating rate was slow, and the rapid heating effect by laser heating alone was insufficient to provide secondary recrystallization nuclei, resulting in inferior magnetic flux densities of less than 1.93 T.

[0172] Steels Nos. 13, 26, and 39 had a fast heating rate, which reduced the orientation that promotes the growth of secondary recrystallization nuclei, and the magnetic flux density was inferior at less than 1.93 T.

[0173] For the steel Nos. other than those mentioned above, all manufacturing process conditions were appropriate, and therefore the magnetic flux density was excellent at 1.93 T or more, and the space factor was also high at 96% or more.

[0174] [Table 4A]

[0175] [Table 4B]

[0176] <5. Example 5> A slab was prepared having a chemical composition, in mass %, of C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.02%, sol. Al: 0.03%, N: 0.01%, with the remainder being Fe and impurities.

[0177] This slab was heated to 1350°C in a heating furnace. The heated slab was subjected to a hot rolling process to produce a hot-rolled steel sheet with a thickness of 2.3 mm. The hot-rolled steel sheet was subjected to a hot-rolled sheet annealing process in which annealing was performed, and then cold rolling was performed to produce a cold-rolled steel sheet with a thickness of 0.22 mm. The cold-rolled steel sheet after the cold rolling process was subjected to a decarburization annealing process. In this decarburization annealing process, before heating, partial rapid heating was performed on one side of the steel sheet using a laser beam under the conditions shown in Table 5A. The laser scanning direction was 90 degrees relative to the rolling direction. In Example 5, the tension applied to the cold-rolled steel sheet and the temperature of the cold-rolled steel sheet during laser beam irradiation were varied.

[0178] After partial rapid heating, the steel sheet was heated in a non-oxidizing atmosphere containing hydrogen and nitrogen at the heating rate shown in Table 5B to cause primary recrystallization, and then the decarburization annealing temperature was set to 830°C and soaked for 60 seconds. At this time, the atmosphere in the heat treatment furnace where the decarburization annealing treatment was performed was a humid atmosphere containing hydrogen and nitrogen. After decarburization annealing, an annealing separator (water slurry) mainly composed of MgO was applied to the surface of the steel sheet, and then the steel sheet was wound into a coil. The coiled steel sheet was subjected to finish annealing.

[0179] The steel sheets after the final annealing process were subjected to an insulating film forming process. In the insulating film forming process, an insulating coating agent mainly composed of colloidal silica and phosphate was applied to the surface (on the glass film) of the grain-oriented electrical steel sheet after the final annealing process, and then baked. In this way, an insulating film, which is a tension insulating film, was formed on the glass film. Grain-oriented electrical steel sheets of each test number were manufactured using the above manufacturing process.

[0180] (5-1. Removal of the film) The chemical composition of the base steel sheet can be measured by a known elemental analysis method. First, the primary coating and secondary coating are removed from the base steel sheet by the following method. Specifically, the grain-oriented electrical steel sheet with the secondary coating is removed by immersing it in a high-temperature alkaline solution. The composition, temperature, and immersion time of the alkaline solution can be adjusted as appropriate. For example, the grain-oriented electrical steel sheet with the secondary coating is immersed in a sodium hydroxide aqueous solution of 30 to 50 mass% NaOH and 50 to 70 mass% H2O at 80 to 90°C for 5 to 10 minutes, and then rinsed and dried. This process removes the secondary coating from the grain-oriented electrical steel sheet.

[0181] Furthermore, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in high-temperature hydrochloric acid to remove the coating. The concentration, temperature, and immersion time of the hydrochloric acid may be adjusted as appropriate. For example, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in 30 to 40 mass % hydrochloric acid at 80 to 90°C for 1 to 5 minutes, and then rinsed with water and dried. Through these steps, a base steel sheet from which the secondary coating and primary coating have been removed is obtained.

[0182] (5-2. Chemical composition measurement test of base steel plate) The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet of each test number was measured by the following method. First, the primary coating and secondary coating of the grain-oriented electrical steel sheet were removed by the above-mentioned method to extract the base steel sheet. Using the base steel sheet, the chemical composition of the base steel sheet was analyzed based on the following [Method for measuring the chemical composition of steel sheet]. Chips were collected from the obtained base steel plate. The collected chips were dissolved in acid to obtain a solution. The solution was subjected to ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) to perform elemental analysis of the chemical composition. The C content and S content were determined by the well-known high-frequency combustion method (combustion-infrared absorption method). The N content was determined using the well-known inert gas fusion-thermal conductivity method. Specifically, the measurements were performed using a Shimadzu component analyzer (product name: ICPS-8000).

[0183] As a result of the analysis, in Example 5, the chemical composition of the base steel plate for all test numbers contained, in mass%, C: 0.01% or less, Si: 3.3%, Mn: 0.08%, S: 0.01% or less, sol.Al: 0.01% or less, N: 0.01% or less, with the remainder being Fe and impurities.

[0184] The magnetic properties (magnetic flux density B8 value) of the grain-oriented electrical steel sheets of each test number were evaluated in accordance with JIS C2556 (2015). The obtained magnetic flux density B8 values ​​are shown in Table 5B.

[0185] The shape of the deformed area of ​​the grain-oriented electrical steel sheet of each test number was measured by the following method. That is, a commercially available surface roughness measuring device (SE3500, manufactured by Kosaka Laboratory) was used, the stylus of the detection part was SE2555N (tip curvature radius 2 μm), the measurement length in the rolling direction was 15 mm per measurement, and the surface roughness was measured five times consecutively for a total length of 75 mm. The measurements were carried out on both the front and back. Within the measurement range on the front and back, W and D were measured at five points on each side. 凸 , D 凹 The width W of the deformation area and the maximum depth D of the depression on one side of the deformation area were measured and evaluated based on the average value. 凹 and the maximum height D of the convex part on the rear side of the deformation area 凸 is shown in Table 5B.

[0186] Furthermore, the space factor of the grain-oriented electrical steel sheet of each test number was evaluated in accordance with JIS C2550-5 (2020). The obtained space factors are shown in Table 5B.

[0187] Furthermore, the area ratio of abnormal grains in the deformed region of each grain-oriented electrical steel sheet was measured using the following method. Specifically, using a Laue diffractometer, the crystal orientation of the width W of the deformed region was measured along the longitudinal centerline of the deformed region at 2 mm intervals in the width direction of the grain-oriented electrical steel sheet. Then, the number of measurement points showing abnormal grains with a deviation angle of 15° or more from the Goss orientation was extracted from the crystal orientation of each measurement point, and the ratio of these measurement points to the total number of measurement points was defined as the area ratio of abnormal grains. However, for steel Nos. with magnetically inferior properties of less than 1.93 T in the magnetic property measurements described above, the area ratio of abnormal grains measured using the Laue diffractometer was not performed. The obtained area ratios of abnormal grains are shown in Table 5B.

[0188] Referring to Tables 5A and 5B, steels Nos. 1 to 5 had low tension during laser heating, large irregularities in the deformed region, steepness of 0.01 or more, and space factor of less than 96%.

[0189] Steel Nos. 21 to 25 had high tension during laser heating, which led to deterioration of the primary recrystallization texture, resulting in inferior magnetic properties, with a magnetic flux density B8 of less than 1.93T.

[0190] Steels Nos. 6, 11, and 16 had low temperatures during laser heating, and the shape deterioration due to the sudden temperature change in the deformation area was significant, the deformation area had large irregularities, and the steepness was 0.01 or more, with a space factor of less than 96%.

[0191] Steels Nos. 10, 15, and 20 had high temperatures during laser heating, and recrystallization had progressed before laser heating, preventing the partial rapid heating effect, resulting in inferior magnetic flux densities of less than 1.93T.

[0192] For the steel Nos. other than those mentioned above, all manufacturing process conditions were appropriate, and therefore the magnetic flux density was excellent at 1.93 T or more, and the space factor was also high at 96% or more.

[0193] [Table 5A]

[0194] [Table 5B]

[0195] 6. Example 6 A slab was prepared whose chemical composition contained the components shown in Table 6A, with the balance being Fe and impurities. This slab was heated to 1350°C in a heating furnace. The heated slab was subjected to a hot rolling process to produce a hot-rolled steel sheet with a thickness of 2.3 mm. The hot-rolled steel sheet was annealed in a hot-rolled sheet annealing process, and then cold-rolled to produce a cold-rolled steel sheet with a thickness of 0.22 mm. The cold-rolled steel sheet was subjected to a decarburization annealing process. In this decarburization annealing process, before heating, one side of the steel sheet was subjected to partial rapid heating using a laser beam under the conditions shown in Table 6B. The laser scanning direction was at an angle of 90 degrees to the rolling direction.

[0196] After partial rapid heating, the steel sheet was heated in a non-oxidizing atmosphere containing hydrogen and nitrogen at the heating rate shown in Table 6C to cause primary recrystallization, and then the decarburization annealing temperature was set to 830°C and soaked for 60 seconds. At this time, the atmosphere in the heat treatment furnace where the decarburization annealing treatment was performed was a humid atmosphere containing hydrogen and nitrogen. After decarburization annealing, an annealing separator (water slurry) mainly composed of MgO was applied to the surface of the steel sheet, and then the steel sheet was wound into a coil. The coiled steel sheet was then subjected to finish annealing.

[0197] The steel sheets after the final annealing process were subjected to an insulating film forming process. In the insulating film forming process, an insulating coating agent mainly composed of colloidal silica and phosphate was applied to the surface (on the glass film) of the grain-oriented electrical steel sheet after the final annealing process, and then baked. In this way, an insulating film, which is a tension insulating film, was formed on the glass film. Grain-oriented electrical steel sheets of each test number were manufactured using the above manufacturing process.

[0198] (6-1. Removal of the film) The chemical composition of the base steel sheet can be measured by a known elemental analysis method. First, the primary coating and secondary coating are removed from the base steel sheet by the following method. Specifically, the grain-oriented electrical steel sheet with the secondary coating is removed by immersing it in a high-temperature alkaline solution. The composition, temperature, and immersion time of the alkaline solution can be adjusted as appropriate. For example, the grain-oriented electrical steel sheet with the secondary coating is immersed in a sodium hydroxide aqueous solution of 30 to 50 mass% NaOH and 50 to 70 mass% H2O at 80 to 90°C for 5 to 10 minutes, and then rinsed and dried. This process removes the secondary coating from the grain-oriented electrical steel sheet.

[0199] Furthermore, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in high-temperature hydrochloric acid to remove the coating. The concentration, temperature, and immersion time of the hydrochloric acid may be adjusted as appropriate. For example, the grain-oriented electrical steel sheet from which the secondary coating has been removed and from which the primary coating remains is immersed in 30 to 40 mass % hydrochloric acid at 80 to 90°C for 1 to 5 minutes, and then rinsed with water and dried. Through these steps, a base steel sheet from which the secondary coating and primary coating have been removed is obtained.

[0200] (6-2. Chemical composition measurement test of base steel plate) The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet of each test number was measured by the following method. First, the primary coating and secondary coating of the grain-oriented electrical steel sheet were removed by the above-mentioned method to extract the base steel sheet. Using the base steel sheet, the chemical composition of the base steel sheet was analyzed based on the following [Method for measuring the chemical composition of steel sheet]. Chips were collected from the obtained base steel plate. The collected chips were dissolved in acid to obtain a solution. The solution was subjected to ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) to perform elemental analysis of the chemical composition. The C content and S content were determined by the well-known high-frequency combustion method (combustion-infrared absorption method). The N content was determined using the well-known inert gas fusion-thermal conductivity method. Specifically, the measurements were performed using a Shimadzu component analyzer (product name: ICPS-8000).

[0201] As a result of the analysis, in Example 6, the chemical composition of the base steel plate contained the components shown in Table 6A, with the balance being Fe and impurities.

[0202] The magnetic properties (magnetic flux density B8 value) of the grain-oriented electrical steel sheets of each test number were evaluated in accordance with JIS C2556 (2015). The obtained magnetic flux density B8 values ​​are shown in Table 6C.

[0203] The shape of the deformed area of ​​the grain-oriented electrical steel sheet of each test number was measured by the following method. That is, a commercially available surface roughness measuring device (SE3500, manufactured by Kosaka Laboratory) was used, the stylus of the detection part was SE2555N (tip curvature radius 2 μm), the measurement length in the rolling direction was 15 mm per measurement, and the surface roughness was measured five times consecutively for a total length of 75 mm. The measurements were carried out on both the front and back. Within the measurement range on the front and back, W and D were measured at five points on each side. 凸 , D 凹 The width W of the deformation area and the maximum depth D of the depression on one side of the deformation area were measured and evaluated based on the average value. 凹 and the maximum height D of the convex part on the rear side of the deformation area 凸 is shown in Table 6C.

[0204] Furthermore, the space factor of the grain-oriented electrical steel sheet of each test number was evaluated in accordance with JIS C2550-5 (2020). The obtained space factors are shown in Table 6C.

[0205] Furthermore, the area ratio of abnormal grains in the deformed region of each grain-oriented electrical steel sheet was measured using the following method. Specifically, using a Laue diffractometer, the crystal orientation was measured in the width direction of the grain-oriented electrical steel sheet at 2 mm intervals along the center line of the deformation region in the longitudinal direction of the deformation region in an area of ​​width W. Then, the number of measurement points showing abnormal grains with a deviation angle of 15° or more from the Goss orientation was extracted from the crystal orientation at each measurement point, and the ratio of these measurement points to the total number of measurement points was defined as the area ratio of abnormal grains. However, for steel No. 1, which had a magnetically inferior strength of less than 1.93 T in the magnetic property measurements described above, the area ratio of abnormal grains measured using the Laue diffractometer was not performed. The obtained area ratios of abnormal grains are shown in Table 6C.

[0206] Referring to Tables 6A to 6C, Steels Nos. 1 to 19 had appropriate chemical compositions of the slabs and appropriate manufacturing process conditions, and therefore had excellent magnetic flux densities of 1.93 T or more and high space factors of 96% or more.

[0207] [Table 6A]

[0208] [Table 6B]

[0209] [Table 6C]

[0210] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

Claims

1. A grain-oriented electrical steel sheet, The chemical composition of the base steel plate is, in mass%, Si: 2.5-4.5%, Mn: 0.01-1.00%, N: 0.01% or less, C: 0.01% or less, sol. Al: 0.01% or less, S: 0.01% or less, Se: 0.01% or less, P: 0.00-0.05%, Sb: 0.00 to 0.50%, Sn: 0.00-0.30%, Cr: 0.00-0.50%, Cu: 0.00-0.50%, Ni: 0.00 to 0.50%, and Bi: 0.0000 to 0.0100%, the balance being Fe and impurities; a magnetic flux density B8 in the rolling direction of the grain-oriented electrical steel sheet is 1.93 T or more, and deformation regions extending across the entire width of the grain-oriented electrical steel sheet are periodically formed in a direction intersecting the rolling direction of the grain-oriented electrical steel sheet at intervals L of 3 mm or more and 30 mm or less, The width W of the deformation region is 0.2 mm or more and 30.6 mm or less, On one side of the deformation region, a maximum height D 凸 On the other side, a convex portion having a maximum depth D 凹 A grain-oriented electrical steel sheet having recesses of 1 μm or more and 4 μm or less formed therein.

2. A grain-oriented electrical steel sheet, The chemical composition of the base steel plate is, in mass%, Si: 2.5-4.5%, Mn: 0.01-1.00%, N: 0.01% or less, C: 0.01% or less, sol. Al: 0.01% or less, S: 0.01% or less, Se: 0.01% or less, P: 0.00-0.05%, Sb: 0.00 to 0.50%, Sn: 0.00-0.30%, Cr: 0.00-0.50%, Cu: 0.00-0.50%, Ni: 0.00 to 0.50%, and Bi: 0.0000 to 0.0100%, the balance being Fe and impurities; a magnetic flux density B8 in the rolling direction of the grain-oriented electrical steel sheet is 1.93 T or more, and deformation regions extending across the entire width of the grain-oriented electrical steel sheet are periodically formed at intervals L of 3 mm or more and 30 mm or less in a direction intersecting the rolling direction of the grain-oriented electrical steel sheet, The width W of the deformation region is 0.2 mm or more and 30.6 mm or less, On one side of the deformation region, a maximum height D 凸 On the other side, a convex portion having a maximum depth D 凹 The concave portions are formed with a steepness 2D of 1 μm or more and 8 μm or less. 凸 / W is 0.0001 or more and less than 0.0050.

3. 3. The grain-oriented electrical steel sheet according to claim 1, wherein the ratio of an area of ​​crystal grains whose crystal orientation deviates from the Goss orientation by 15° or more in the deformation region to a total area of ​​the deformation region is 5% or less.

4. The chemical composition of the base steel plate is, in mass%, P: 0.01-0.05%, Sb: 0.01 to 0.50%, Sn: 0.01-0.30%, Cr: 0.01-0.50%, Cu: 0.01 to 0.50%, Ni: 0.01 to 0.50%, and Bi: 0.0001-0.0100%, The grain-oriented electrical steel sheet according to claim 1 or 2, comprising one or more selected from the group consisting of:

5. A method for manufacturing the grain-oriented electromagnetic steel sheet according to claim 1 or 2, In mass%, Si: 2.5-4.5%, Mn: 0.01-1.00%, N: 0.01-0.020%, C: 0.02-0.10%, sol. Al: 0.01 to 0.05%, S and Se: 0.01 to 0.05% in total, P: 0.00-0.05%, Sn: 0.00-0.30%, Sb: 0.00 to 0.50%, Cr: 0.00-0.50%, Cu: 0.00-0.50%, Ni: 0.00 to 0.50%, and Bi: 0.0000 to 0.0100%; a hot rolling step of heating a slab having a chemical composition with the balance being Fe and impurities, and hot rolling the heated slab to obtain a hot-rolled steel sheet; a hot-rolled sheet annealing step of annealing the hot-rolled steel sheet; A cold rolling process in which cold rolling is performed on the hot-rolled steel sheet after the hot-rolled sheet annealing process to obtain a cold-rolled steel sheet; a decarburization annealing step of subjecting the cold-rolled steel sheet to decarburization annealing to obtain a decarburization annealed steel sheet; a finish annealing step of applying an annealing separator to the decarburization-annealed steel sheet and then performing finish annealing to form a glass film on the surface of the decarburization-annealed steel sheet to obtain a finish annealed sheet; an insulating film forming step of applying an insulating film forming liquid to the finish-annealed sheet and then performing a heat treatment to form an insulating film on the surface of the finish-annealed sheet, The decarburization annealing step is carried out in a non-oxidizing atmosphere at a temperature of 0.2 kg / mm ２ 1.2kg / mm ​​or more ２ a partial rapid heating step of irradiating the cold-rolled steel sheet, which has been heated to a temperature of 200°C or more and 550°C or less, under a tension of 0°C or less with a laser beam or an electron beam in a direction intersecting the rolling direction at an interval L within the range shown in the following formula (1) across the entire width of the cold-rolled steel sheet, to partially rapid heat one side surface of the cold-rolled steel sheet; a heating step of heating the cold-rolled steel sheet after the partial rapid heating step in a non-oxidizing atmosphere from a temperature range of 550°C or less to a temperature range of 750 to 950°C at an average heating rate of 5°C / sec or more and 2000°C / sec or less; Including, The average intensity of the laser beam or the electron beam input to the partial rapid heating portion where the partial rapid heating is performed is defined as P (W), The rolling direction diameter of the partial rapid heating portion is defined as Dl (mm), The diameter in the plate width direction of the partial rapid heating portion is Dc (mm), The scanning speed in the plate width direction of the partial rapid heating section is Vc (mm / s), The irradiation energy density is Up=4 / π×P / (Dl×Vc), When the instantaneous power density is Ip=4 / π×P / (Dl×Dc), A method for producing a grain-oriented electrical steel sheet, characterized in that the following formulas (2) to (4) are satisfied: 3 mm ≦ L ≦ 30 mm (1) L / 50≦Dl≦L / 2 (2) 5J / mm ２ ≦Up≦48J / mm ２ (3) 0.05kW / mm ２ ≦Ip≦4.99kW / mm ２ (4)

6. The method for producing a grain-oriented electrical steel sheet according to claim 5, wherein the irradiation energy density Up further satisfies the following formula (5): 5J / mm ２ ≦Up<62.5×DlJ / mm ２ (5)

7. The chemical composition of the slab, in mass %, is P: 0.01-0.05%, Sn: 0.01-0.30%, Sb: 0.01 to 0.50%, Cr: 0.01-0.50%, Cu: 0.01 to 0.50%, Ni: 0.01 to 0.50%, and Bi: 0.0001-0.0100%, The method for producing a grain-oriented electrical steel sheet according to claim 5, characterized in that the steel sheet contains one or more selected from the group consisting of:

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