Method for manufacturing grain-oriented electrical steel sheet and grain-oriented electrical steel sheet

Abstract

To provide a grain-oriented silicon steel sheet in which the generation amount of closure domains is suppressed, the iron loss of the obtained grain-oriented silicon steel sheet is reduce, and jointly, noise reduction is realized, and a method for producing the same.SOLUTION: A finished annealed plate before magnetic domain segmentation treatment is subjected to light pickling treatment using a special light pickling solution, thus the generation amount of closure domains is suppressed, the increase of hysteresis loss is suppressed, the iron loss of a grain-oriented silicon steel sheet is reduced, and noise reduction is realize. In the obtained grain-oriented silicon steel sheet, before the application of magnetic domain segmentation treatment, eddy current loss is reduced by 0.07 W / kg or higher, the increase of hysteresis is 0.02 W / kg or lower, and a change in magnetostriction λp-p upon excitation to 1.7T is 0.2 μm / m or lower.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet and a grain-oriented electrical steel sheet. [Background technology]

[0002] Grain-oriented electrical steel sheets generally contain 2% to 5% by mass of Si as a steel sheet component, and the grain orientation of the steel sheet is called the Goss orientation, {110} <001> Grain-oriented electrical steel has excellent magnetic properties and is used, for example, as the core material for static inductors in transformers and other equipment.

[0003] In order to improve the magnetic properties of such grain-oriented electrical steel sheets, various technological developments have been made. In particular, with the recent demand for energy saving, grain-oriented electrical steel sheets are required to have even lower iron loss. In order to reduce the iron loss of grain-oriented electrical steel sheets, it is effective to increase the concentration of the crystal grains in the Goss orientation of the steel sheet to improve the magnetic flux density and reduce the hysteresis loss.

[0004] Grain-oriented electrical steel sheets used as base materials for wound transformers are required to reduce noise as well as reduce iron loss. Magnetic domain refinement is performed on electrical steel sheets to reduce iron loss. Magnetic domain refinement for reducing iron loss is generally performed by introducing distortion near the surface of the electrical steel sheet using laser irradiation or the like.

[0005] As a magnetic domain refinement method for introducing strain near the surface of an electrical steel sheet by laser irradiation or the like, for example, Patent Document 1 discloses that the iron loss of the obtained grain-oriented electrical steel sheet is reduced by suppressing the N content in the forsterite coating formed after final annealing to 3.0 mass% or less and performing a magnetic domain refinement process by laser irradiation. It also discloses that the iron loss improvement effect is further improved by suppressing the compositional variation of each forsterite by controlling the Al and Ti amounts in the forsterite coating and setting the standard deviation of the forsterite grain size to 1.0 times or less the average grain size.

[0006] Patent Document 2 discloses that by controlling the amount of crystalline forsterite in the glass coating applied to the surface of the steel sheet and the distribution of forsterite grains having a specific average crystal grain size within the steel sheet surface, a grain-oriented electrical steel sheet for laser magnetic domain control is provided that has a high magnetic domain control effect even at low laser power, and that the grain-oriented electrical steel sheet achieves a high level of low iron loss and low magnetostriction.

[0007] Patent Documents 1 and 2 propose various techniques for refining magnetic domains to obtain the effect of reducing iron loss, but make no proposal regarding achieving both the effects of reducing noise and iron loss. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2012-31512 A [Patent Document 2] JP 2019-002039 A Summary of the Invention [Problem to be solved by the invention]

[0009] The closure domains introduced on the surface of magnetic steel sheets by the magnetic domain refining process have a negative effect on noise. Transformers are required to reduce both noise and iron loss, and there is a particular demand for a magnetic domain refining method that has a minimal effect on noise.

[0010] In the present invention, the finish annealed sheet prior to the magnetic domain refinement treatment is subjected to light pickling treatment using a special light pickling solution, thereby increasing the heat transfer coefficient of precipitates such as MnS present in the surface layer of the steel sheet, concentrating the effects of the magnetic domain refinement treatment only on the surface layer of the steel sheet, and reducing the total amount of distortion, i.e., suppressing the amount of closure domains generated and also suppressing an increase in hysteresis loss, thereby reducing the iron loss of the obtained grain-oriented electrical steel sheet, and also achieving further noise reduction. [Means for solving the problem]

[0011] The gist of the present invention is (1) In order, By mass% 、S i:2.5%~4.5%, Mn:0.01%~0.15%, C: 0.020~0.100%, S and Se: 0.001~0.050%, acid-soluble Al: 0.010~0.050%, N: 0.002~0.015%, Cr: 0.300% or less, Cu: 0.400% or less, P: 0.500% or less, Sn: 0.300% or less, Sb: 0.300% or less, Ni: 1.000% or less, Bi: 0.020% or less and the balance being Fe and impurities, to obtain a hot-rolled steel sheet; The hot-rolled steel sheet is subjected to hot-rolled sheet annealing. Fever Obtaining a rolled annealed sheet; A step of cold rolling the hot-rolled annealed sheet to obtain a cold-rolled steel sheet; A step of subjecting the cold-rolled steel sheet to decarburization annealing; A step of applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after decarburization annealing, and then performing finish annealing to obtain a finish annealed sheet; A step of subjecting the finish annealed sheet to light pickling to remove the annealing separator; A process of applying an insulating coating liquid to the steel sheet from which the annealing separator has been removed, and performing flattening annealing; a step of subjecting the obtained flattened annealed sheet to a magnetic domain refining treatment by a thermal distortion imparting means; A method for producing a grain-oriented electrical steel sheet comprising: The light pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, and the total concentration of each element is 0.0001 to 0.1000 mass %in can be, The pH is between -1 and 5, The liquid temperature is 15°C or higher and 100°C or lower. The time for which the finish annealed sheet is immersed in the light pickling solution is 5 seconds or more and 200 seconds or less. A method for producing a grain-oriented electrical steel sheet comprising the steps of: (2) The method for producing a grain-oriented electrical steel sheet according to (1) above, wherein the thermal distortion imparting means is selected from a laser and an electron beam. (3) By mass percent 、S i: 2.50-4.50%, Mn: 0.01-0.15% C: 0.085% or less, acid-soluble Al: 0.065% or less, N: 0.012% or less, Cr: 0.3% or less, Cu: 0.4% or less, P: 0.5% or less, Sn: 0.3% or less, Sb: 0.3% or less, Ni: 1% or less, S and Se, total 0.001 to 0.050%, Bi: 0.02% or less and the balance being Fe and impurities, and the magnetic steel sheet is subjected to magnetic domain refinement by a thermal distortion imparting means, Compared to before the magnetic domain refining treatment Eddy current loss is reduced by more than 0.07W / kg. The increase in hysteresis loss is 0.02 W / kg or less, The change in magnetostriction λp-p when excited to 1.7 T is 0.2 μm / m or less. A directional electrical steel sheet. (4) The grain-oriented electrical steel sheet according to (3) above, wherein the thermal distortion imparting means is selected from a laser and an electron beam. Effect of the Invention

[0012] According to the present invention, the effect of the magnetic domain refining treatment during manufacturing is concentrated only on the surface layer portion of the steel sheet, reducing the total amount of distortion and suppressing the amount of closure domains generated, thereby suppressing an increase in hysteresis loss, reducing iron loss in the grain-oriented electrical steel sheet, and reducing noise. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Preferred embodiments of the present invention will be described in detail below. Unless otherwise specified, the expression "A to B" for numerical values ​​A and B means "A or more and B or less." In such an expression, when a unit is added only to numerical value B, the unit is also applied to numerical value A.

[0014] One embodiment of the present invention is a method for producing a grain-oriented electrical steel sheet having the following configuration. In order, by mass%, 、S i:2.5%~4.5%, Mn:0.01%~0.15%, C: 0.020~0.100%, S and Se: 0.001~0.050%, acid-soluble Al: 0.010~0.050%, N: 0.002~0.015%, Cr: 0.300% or less, Cu: 0.400% or less, P: 0.500% or less, Sn: 0.300% or less, Sb: 0.300% or less, Ni: 1.000% or less, Bi: 0.020% or less and the balance being Fe and impurities, to obtain a hot-rolled steel sheet; The hot-rolled steel sheet is subjected to hot-rolled sheet annealing. Fever Obtaining a rolled annealed sheet; A step of cold rolling the hot-rolled annealed sheet to obtain a cold-rolled steel sheet; A step of subjecting the cold-rolled steel sheet to decarburization annealing; A step of applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after decarburization annealing, and then performing finish annealing to obtain a finish annealed sheet; A step of subjecting the finish annealed sheet to light pickling to remove the annealing separator; A process of applying an insulating coating liquid to the steel sheet from which the annealing separator has been removed, and performing flattening annealing; a step of subjecting the obtained flattened annealed sheet to a magnetic domain refining treatment by a thermal distortion imparting means; A method for producing a grain-oriented electrical steel sheet comprising: The light pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, and the total concentration of each element is 0.0001 to 0.1000 mass %in can be, The pH is between -1 and 5, The liquid temperature is 15°C or higher and 100°C or lower. The time for which the finish annealed sheet is immersed in the light pickling solution is 5 seconds or more and 200 seconds or less. A method for producing a grain-oriented electrical steel sheet comprising the steps of:

[0015] The method for manufacturing the grain-oriented electrical steel sheet according to this embodiment will be specifically described below.

[0016] [Slab composition] First, the composition of the slab used in the grain-oriented electrical steel sheet according to this embodiment will be described. In the following, unless otherwise specified, the notation "%" will represent "mass %". The remainder of the slab other than the elements described below is Fe and impurities. Here, impurities refer to components contained in raw materials or components mixed in during the manufacturing process, and components that are not intentionally contained in the steel sheet. The chemical composition of the slab, which is the material for the grain-oriented electrical steel sheet, is basically similar to the composition of the grain-oriented electrical steel sheet. However, in the manufacture of general grain-oriented electrical steel sheets, some of the contained elements are discharged outside the system by decarburization annealing and purification annealing during the manufacturing process, so that the chemical composition of the slab, which is the material, and the grain-oriented electrical steel sheet, which is the final product, are different. The slab composition can be appropriately adjusted taking into account the effects of decarburization annealing and purification annealing during the manufacturing process so that the grain-oriented electrical steel sheet has the desired characteristics.

[0017] The composition of the slab used in the manufacture of the grain-oriented electrical steel sheet according to the invention is 、S Contains i: 2.50 to 4.50%, Mn: 0.01 to 0.15%.

[0018] The Si (silicon) content is 2.5 to 4.5%. Si increases the electrical resistance of the steel sheet, thereby reducing eddy current loss, which is one of the causes of iron loss. If the Si content is less than 2.5%, it is not preferable because it becomes difficult to sufficiently suppress the eddy current loss of the final grain-oriented electrical steel sheet. If the Si content exceeds 4.5%, it is not preferable because the workability of the grain-oriented electrical steel sheet decreases. Therefore, the Si content is 2.5% to 4.5%, and preferably 2.7 to 4.0%.

[0019] The content of Mn (manganese) is 0.01 to 0.15%. Mn forms MnS and MnSe, which are inhibitors that affect secondary recrystallization. If the content of Mn is less than 0.01%, the absolute amount of MnS and MnSe that cause secondary recrystallization is insufficient, which is not preferable. If the content of Mn is more than 0.15%, it is not preferable because it becomes difficult to dissolve Mn during slab heating. In addition, if the content of Mn is more than 0.15%, it is not preferable because the precipitate size of MnS and MnSe, which are inhibitors, tends to become coarse, and the optimal size distribution as an inhibitor is impaired. Therefore, the content of Mn is 0.01 to 0.15%, preferably 0.03 to 0.13%.

[0020] The components other than Si and Mn can be the following components. For example, the components other than Si and Mn are, by mass%, C: 0.020-0.100%, S and Se: 0.001-0.050%, acid-soluble Al: 0.010-0.050%, N: 0.002-0.015%, Cr: 0.020-0.100%, S and Se: 0.001-0.050%, Cr: 0.020-0.015 ... :0 .300% or less, Cu :0 .400% or less, P :0 .500% or less, Sn :0 .300% or less, Sb :0 .300% or less, Ni :1 .000% or less, Bi:0 It may contain up to .020%.

[0021] The C (carbon) content is 0.02 to 0.10%. C has various roles, but if the C content is less than 0.02%, the grain size becomes excessively large when the slab is heated, which increases the iron loss value of the final grain-oriented electrical steel sheet, which is not preferable. If the C content exceeds 0.10%, the decarburization time becomes long during decarburization after cold rolling, which increases the manufacturing cost, which is not preferable. Also, if the C content exceeds 0.10%, decarburization is likely to be incomplete, which is not preferable because it may cause magnetic aging in the final grain-oriented electrical steel sheet. Therefore, the C content is 0.02 to 0.10%, and preferably 0.05 to 0.09%.

[0022] The total content of S (sulfur) and Se (selenium) is 0.001 to 0.050%. S and Se form an inhibitor together with the above-mentioned Mn. Both S and Se may be contained in the slab, but at least one of them should be contained in the slab. If the total content of S and Se is outside the above range, it is not preferable because a sufficient inhibitor effect cannot be obtained. Therefore, the total content of S and Se is 0.001 to 0.050%, preferably 0.001 to 0.040%.

[0023] The content of acid-soluble Al (acid-soluble aluminum) is 0.01 to 0.05%. Acid-soluble Al constitutes an inhibitor necessary for producing a grain-oriented electrical steel sheet with high magnetic flux density. If the content of acid-soluble Al is less than 0.01%, the amount of acid-soluble Al is insufficient, and the inhibitor strength is insufficient, which is not preferable. If the content of acid-soluble Al is more than 0.05%, the AlN precipitated as an inhibitor becomes coarse, which is not preferable, and therefore the inhibitor strength is reduced. Therefore, the content of acid-soluble Al is 0.01 to 0.05%, and preferably 0.01 to 0.04%.

[0024] The N (nitrogen) content is 0.002 to 0.015%. N forms AlN, which is an inhibitor, together with the above-mentioned acid-soluble Al. If the N content is outside the above range, it is not preferable because a sufficient inhibitor effect cannot be obtained. Therefore, the N content is 0.002 to 0.015%, and preferably 0.002 to 0.012%.

[0025] In addition, the slab used in the manufacture of the grain-oriented electrical steel sheet according to the present embodiment may contain, in addition to the above-mentioned elements, one or more elements selected from the group consisting of Cu: 0.4% or less, P: 0.5% or less, Sn: 0.3% or less, Sb: 0.3% or less, Ni: 1.0% or less, and Bi: 0.02% or less, in mass%, in place of a portion of the remaining Fe, in order to improve magnetic properties. In the slab according to one embodiment, the Cr content may be 0.02% or more, the Bi content may be 0.0005% or more, the Sb content may be 0.005% or more, and the Mo content may be 0.005% or more, in mass%.

[0026] A slab is formed by casting molten steel adjusted to the above-described composition. The method for casting the slab is not particularly limited. In research and development, even if a steel ingot is formed in a vacuum melting furnace or the like, the same effects as when a slab is formed can be confirmed for the above-described components.

[0027] [Process to make hot-rolled steel sheet] The cast slab is heated at a predetermined temperature, and the heated slab is hot-rolled to be processed into a hot-rolled steel sheet. The thickness of the hot-rolled steel sheet after processing may be, for example, 1.8 mm to 3.5 mm. If the thickness of the hot-rolled steel sheet is less than 1.8 mm, the temperature of the steel sheet after hot rolling becomes low, and the amount of AlN precipitated in the steel sheet increases, making secondary recrystallization unstable, and the magnetic properties of the grain-oriented electrical steel sheet having a final thickness of 0.23 mm or less are degraded, which is not preferable. If the thickness of the hot-rolled steel sheet is more than 3.5 mm, the rolling load in the cold rolling process becomes large, which is not preferable.

[0028] [Annealing process] The hot-rolled steel sheet may be subjected to normal hot-rolled annealing to obtain a hot-rolled annealed sheet. By subjecting the hot-rolled steel sheet to hot-rolled annealing, the grain structure of the hot-rolled steel sheet can be adjusted, and more stable secondary recrystallization can be obtained.

[0029] [Process to make cold-rolled steel sheet] The hot-rolled steel sheet is pickled and then processed into a cold-rolled steel sheet by a single cold rolling process or multiple cold rolling processes with intermediate annealing. In addition, the steel sheet may be heat-treated at about 300°C or less between passes of cold rolling, between rolling roll stands, or during rolling. In such a case, the magnetic properties of the final grain-oriented electrical steel sheet can be improved. The hot-rolled steel sheet may be rolled by three or more cold rolling passes, but since multiple cold rolling passes increase the manufacturing cost, it is preferable to roll the hot-rolled steel sheet by one or two cold rolling passes. When cold rolling is performed by reverse rolling such as a Sendzimir mill, the number of passes in each cold rolling pass is not particularly limited, but is preferably 9 passes or less from the viewpoint of manufacturing cost.

[0030] [Decarburization annealing process] Next, decarburization annealing is performed. The cold-rolled steel sheet is subjected to heat treatment (i.e., decarburization annealing) under a predetermined temperature condition (for example, heating at 700 to 900°C for 1 to 3 minutes). When the decarburization annealing is performed, the carbon in the cold-rolled steel sheet is reduced to a predetermined amount or less, and a primary recrystallization structure is formed. In addition, in the decarburization annealing, an oxide layer containing silica (SiO2) as a main component is formed on the surface of the cold-rolled steel sheet.

[0031] Next, an annealing separator is applied. In this process, an annealing separator containing magnesia (MgO) as a main component is applied to the surface of the cold-rolled steel sheet (the surface of the oxide layer).

[0032] [Finishing annealing process] Next, the cold-rolled steel sheet coated with the annealing separator is subjected to heat treatment (i.e., finish annealing) under a predetermined temperature condition (for example, heating at 1100 to 1300°C for 20 to 24 hours). When the finish annealing is performed, secondary recrystallization occurs in the cold-rolled steel sheet, and the cold-rolled steel sheet is purified. As a result, a cold-rolled steel sheet is obtained that has the above-mentioned chemical composition of the steel sheet and whose crystal orientation is controlled so that the magnetization easy axis of the crystal grains coincides with the rolling direction X.

[0033] Furthermore, when the above-mentioned finish annealing treatment is performed, the oxide layer containing silica as a main component reacts with the annealing separator containing magnesia as a main component to form a glass film containing composite oxides such as forsterite (Mg2SiO4) on the surface of the steel sheet. In the finish annealing process, the finish annealing treatment is performed with the steel sheet wound in a coil shape. By applying the annealing separator to the surface of the steel sheet, it is possible to prevent seizure from occurring on the coiled steel sheet.

[0034] [Light pickling process] Subsequently, the finish annealed steel sheet is lightly pickled to remove any annealing separator remaining on the surface.

[0035] The light pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, the total concentration of each element is 0.0001 to 0.1000%, and the pH is -1 to 5. The temperature of the pickling solution is 15°C to 100°C, and the steel sheet is immersed in the light pickling solution for 5 seconds to 200 seconds.

[0036] If the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the light pickling solution is less than 0.0001%, the effect of modifying the residual MnS / Se surface in the thickness direction is insufficient, which is not preferable. If the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the light pickling solution is more than 0.1000%, the effect of improving the magnetic property is saturated and the cost of the light pickling solution increases, which is not preferable. Therefore, the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the light pickling solution is 0.0001 to 0.1000%.

[0037] If the pH of the light pickling solution is less than -1, the acidity becomes too strong and the glass film on the steel sheet surface is removed, which is not preferable. If the pH of the light pickling solution is more than 5, the effect of modifying the residual MnS / Se surface by the light pickling treatment becomes insufficient, which is not preferable. Therefore, the pH of the light pickling solution is from -1 to 5.

[0038] If the temperature of the light pickling solution is less than 15°C, the effect of modifying the residual MnS / Se surface by the light pickling treatment will be insufficient, which is not preferable. If the temperature of the light pickling solution is more than 100°C, the handling of the pickling solution will be difficult, which is not preferable. Therefore, the temperature of the light pickling solution is 15°C or more and 100°C or less.

[0039] When the time for which the steel sheet is immersed in the light pickling solution in the light pickling treatment is less than 5 seconds, the effect of modifying the surface of the residual MnS / Se by the light pickling treatment becomes insufficient, which is not preferable. When the time for which the steel sheet is immersed in the light pickling solution in the light pickling treatment exceeds 200 seconds, the equipment becomes long and large, which is not preferable. Therefore, the time for which the steel sheet is immersed in the light pickling solution in the light pickling treatment is 5 seconds or more and 200 seconds or less.

[0040] When light pickling is performed under the above-mentioned conditions, the precipitates in the steel, MnS, are replaced by sulfides such as Cu in the surface layer of the steel sheet, or are coated with Cu, etc., so that the heat transfer coefficient of these precipitates themselves increases, and the heat transfer coefficient of the surface layer of the steel sheet containing these precipitates also increases. Here, the "surface layer of the steel sheet" refers to a depth of about 10 μm from the surface of the steel sheet. In addition, "replacement" refers to the Mn portion of the originally formed MnS being replaced by Cu, etc. derived from the light pickling solution, and MnS being replaced with sulfides such as Cu, and "coated" refers to the new precipitation of Cu, etc. derived from the pickling solution around the originally formed MnS. Since such a phenomenon in the present invention is not affected by the precipitation method of Cu, etc., either the substitution with sulfides such as Cu, or the coating with Cu, etc. may occur during the pickling treatment. This makes it possible to increase the heat propagation effect of laser irradiation, etc., which imparts thermal distortion, in the surface layer of the steel sheet.

[0041] [Application of insulating coating liquid ~ Flattening annealing process] An insulating coating containing, for example, aluminum phosphate or colloidal silica as a main component is applied to the surface of the steel sheet that has been lightly pickled. The components of the insulating coating are not particularly limited as long as the steel sheet is provided with insulation and tension. Thereafter, flattening annealing is performed under a predetermined temperature condition (for example, 840 to 920°C), and finally, a grain-oriented electrical steel sheet is obtained.

[0042] [Magnetic domain subdivision processing] The flattened annealed sheet is subjected to a magnetic domain refinement treatment by a thermal strain imparting means, which uses a laser or an electron beam to irradiate the surface of the steel sheet substantially perpendicular to the rolling direction to locally impart plastic strain.

[0043] When a laser is used as a heat applying means, a high-power laser generally used for industrial purposes, such as a fiber laser, a YAG laser, a semiconductor laser, or a CO2 laser, can be used as a laser light source. A pulsed laser or a continuous wave laser can also be used as a laser light source. As the laser light, it is preferable to use a single mode laser with high focusing ability.

[0044] As the conditions for the laser light irradiation, for example, it is preferable to set the laser output to 200W to 3000W, the laser light focusing spot diameter in the rolling direction (i.e., the diameter including 86% of the laser output, hereinafter abbreviated as 86% diameter) to 10μm to 200μm, the laser light focusing spot diameter in the sheet width direction (86% diameter) to 10μm to 1000μm, and the laser scanning speed to 5m / s to 50m / s. These laser irradiation conditions are appropriately adjusted so that low iron loss and low magnetostriction can be achieved at the same time.

[0045] When an electron beam is used as the heat application means, the electron beam irradiation device may be, for example, a normal electron beam irradiation device using a filament, a grid, an electron gun, an electromagnetic lens, and a deflection coil.

[0046] The irradiation conditions of the electron beam are preferably, for example, acceleration voltage: 50 kV to 350 kV, beam current: 0.3 mA to 50 mA, beam irradiation diameter: 10 μm to 500 μm, irradiation interval: 3 mm to 20 mm, and scan speed: 5 m / sec to 80 m / sec. These electron beam irradiation conditions are appropriately adjusted so that low iron loss and low magnetostriction can be achieved at the same time.

[0047] Another embodiment of the present invention is a grain-oriented electrical steel sheet obtained by the above-mentioned method for producing a grain-oriented electrical steel sheet of the present invention. 、S i: 2.50-4.50%, Mn: 0.01-0.15% C: 0.085% or less, acid-soluble Al: 0.065% or less, N: 0.012% or less, Cr: 0.3% or less, Cu: 0.4% or less, P: 0.5% or less, Sn: 0.3% or less, Sb: 0.3% or less, Ni: 1% or less, S and Se, total 0.001 to 0.050%, Bi: 0.02% or lessand the balance being Fe and impurities, and which has been subjected to a magnetic domain refinement treatment by a thermal distortion imparting means, wherein the grain-oriented electrical steel sheet has an eddy current loss reduced by 0.07 W / kg or more compared to before the magnetic domain refinement treatment, an increase in hysteresis loss is 0.02 W / kg or less, and a change in magnetostriction λp-p when excited to 1.7 T is 0.2 μm / m or less.

[0048] [Steel plate composition] First, the chemical composition of the steel sheet used in the grain-oriented electrical steel sheet according to the present invention will be described. In the following, unless otherwise specified, the notation "%" represents "mass%." The balance of the steel sheet other than the elements described below is Fe and impurities.

[0049] The composition of the steel sheet used in the grain-oriented electrical steel sheet of the present invention is {110} <001> It has a favorable composition for controlling the Goss texture accumulated in the orientation. 、S Contains i: 2.50 to 4.50%, Mn: 0.01 to 0.15%.

[0050] (Si: 2.50~4.50%) The content of Si (silicon) is 2.50 to 4.50%. Si increases the electrical resistance of the steel sheet, thereby reducing eddy current loss, which is one of the causes of iron loss. If the content of Si is less than 2.50%, it is not preferable because it becomes difficult to sufficiently suppress the eddy current loss of the final grain-oriented electrical steel sheet. If the content of Si is more than 4.50%, it is not preferable because the workability of the grain-oriented electrical steel sheet decreases. Therefore, the content of Si is 2.50 to 4.50%, and preferably 2.70 to 4.00%.

[0051] (Mn: 0.01 to 0.15%) The content of Mn (manganese) is 0.01 to 0.15%. Mn forms MnS and MnSe, which are inhibitors that affect secondary recrystallization. If the content of Mn is less than 0.01%, the absolute amount of MnS and MnSe that cause secondary recrystallization is insufficient, which is not preferable. If the content of Mn is more than 0.15%, it is not preferable because it becomes difficult to dissolve Mn during slab heating. In addition, if the content of Mn is more than 0.15%, it is not preferable because the precipitate size of MnS and MnSe, which are inhibitors, tends to become coarse, and the optimal size distribution as an inhibitor is impaired. Therefore, the content of Mn is 0.01 to 0.15%, preferably 0.03 to 0.13%.

[0052] The components other than Si and Mn may be the components contained in ordinary grain-oriented electrical steel sheets. For example, the components other than Si and Mn are, by mass%, C :0 .085% or less, acid soluble Al :0 .065% or less, N :0 .012% or less, Cr :0 .3% or less, Cu :0 .4% or less, P :0 .5% or less, Sn :0 .3% or less, Sb :0 .3% or less, Ni :1 %, S and Se are 0.001 to 0.050% in total, Bi :0 It may contain up to .02%.

[0053] The balance of the steel sheet other than the above-mentioned components is Fe and impurities. Here, the impurity elements refer to components contained in raw materials or components mixed in during the manufacturing process, but not intentionally contained in the steel sheet.

[0054] [Total iron loss] The total energy loss that occurs in grain-oriented electrical steel sheet when it is excited with an AC current is called iron loss (here, we will call it "total iron loss" because it is the sum of eddy current loss and hysteresis loss, which will be described later). Usually, total iron loss is measured by a method using an Epstein tester in JIS C 2550-1 or a method using a single sheet tester in JIS C 2556:2015. Both measuring instruments use the same measurement principle, in which an excitation force is applied to the test piece by passing an AC excitation current through an excitation winding (primary winding) that surrounds the test piece, and the resulting magnetization (magnetic polarization) of the test piece is measured by measuring the induced electromotive force generated in a search coil (secondary winding) that also surrounds the test piece, thereby measuring the magnetic polarization (magnetic flux density) in the test piece. The total iron loss is measured by inputting the magnetic polarization signal and the excitation force signal into a power meter.

[0055] [Eddy current loss] The "eddy current loss" in this invention refers to the iron loss caused by eddy currents generated in a steel sheet by induced electromotive force during AC excitation, and is calculated by subtracting hysteresis loss from total iron loss. Alternatively, there is a method of calculating it from the slope of the change in the value obtained by dividing the total iron loss by the excitation frequency (frequency separation).

[0056] The grain-oriented electrical steel sheet according to the present invention has eddy current loss reduced by 0.07 W / kg or more compared to the electrical steel sheet before being subjected to the magnetic domain refinement treatment. The reason why eddy current loss is reduced by more than 0.07 W / kg is believed to be that the amount of closure domains formed by the residual strain introduced by the magnetic domain refinement treatment is sufficient, resulting in a significant magnetic domain refinement effect. For this reason, in the grain-oriented electrical steel sheet according to the present invention, the amount of closure domains generated is controlled.

[0057] The eddy current loss was measured as follows. The iron loss is measured by AC magnetic measurement using the Epstein test method specified in JIS C 2550-1 or the single sheet magnetic measurement method specified in JIS C 2556, and the hysteresis loss described below is subtracted to obtain the iron loss.

[0058] [Hysteresis loss] The "hysteresis loss" in the present invention refers to an iron loss component that is not dependent on the excitation frequency, and is determined by multiplying the loss determined by DC magnetic measurement by the excitation frequency.

[0059] The grain-oriented electrical steel sheet according to the present invention has an increase in hysteresis loss of 0.02 W / kg or less compared to the electrical steel sheet before being subjected to the magnetic domain refinement treatment. The reason why the increase in hysteresis loss is less than 0.02 W / kg is believed to be because the residual strain induced by the domain refinement treatment is localized near the surface, and the closure domains that are formed are also localized near the surface, so as not to impede the domain wall motion that is necessary for the magnetization process. For this reason, in the grain-oriented electrical steel sheet according to the present invention, the amount of closure domains generated is controlled.

[0060] The hysteresis loss was measured as follows. It is calculated by multiplying the iron loss obtained by DC magnetic measurement using the Epstein test method specified in JIS C 2550-1 or the single sheet magnetic measurement method specified in JIS C 2556 by the excitation frequency.

[0061] [Magnetostriction λp-p] In the present invention, "magnetostriction λp-p" refers to the absolute value of the difference between the minimum and maximum values ​​of magnetostriction deformation when excited with an alternating current. In other words, it is |λmax-λmin|. However, the value converted to the value of magnetostriction deformation when the reference sample length is set to 1 m is used.

[0062] The grain-oriented electrical steel sheet according to the present invention has a change in magnetostriction λp-p of 0.2 μm / m or less when excited at 1.7 T. The reason why the change in magnetostriction λp-p is less than 0.2 μm / m is believed to be that the residual strain introduced by the magnetic domain refinement process is localized near the surface and is not large as a total volume fraction of the closure domains, so that the amount of magnetostrictive deformation when the closure domains disappear during magnetization is small. For this reason, when the grain-oriented electrical steel sheet according to the present invention is used in a transformer, noise generation is reduced.

[0063] The method for measuring the magnetostriction λp-p is as follows. A rectangular sample cut so that its length is parallel to the rolling direction is inserted into an excitation frame, and magnetostriction deformation when excited with AC is measured using a non-contact optical measuring device such as the laser Doppler method. The measured waveform of magnetostriction deformation is stored in a transient memory, and magnetostriction λp-p can be calculated from the maximum and minimum values ​​of magnetostriction deformation within one period of the excitation waveform of the sample measured separately with a search coil.

[0064] Plate Thickness The thickness of the grain-oriented electrical steel sheet of the present invention is preferably 0.1 to 0.5 mm, and more preferably 0.15 to 0.35 mm.

[0065] The electrical steel sheet according to the present invention has reduced iron loss (eddy current loss, hysteresis loss), and when used in a transformer, reduces noise generation. This effect is believed to be due to the light pickling performed on the finish annealed sheet during the production of the grain-oriented electrical steel sheet.

[0066] When the finish annealed sheet is lightly pickled under the above-mentioned light pickling conditions, the precipitates in the steel, MnS, are replaced by sulfides such as Cu in the surface layer of the steel sheet, or are coated with Cu, etc., so that the heat transfer coefficient of these precipitates themselves increases, and the heat transfer coefficient of the surface layer of the steel sheet containing these precipitates also increases. This makes it possible to increase the heat transfer effect of laser irradiation, etc., which imparts thermal strain, in the surface layer of the steel sheet. In the present invention, the strain induced by irradiation with a laser or the like is concentrated only in the surface layer by increasing the heat transfer coefficient only on the surface of the steel sheet, thereby reducing the total amount of strain. In other words, the magnetic domain refinement effect is obtained while suppressing the amount of closure domain generation. In addition, the reduction in the total amount of strain also suppresses the increase in hysteresis loss due to irradiation with a laser or the like. EXAMPLES

[0067] The grain-oriented electrical steel sheet obtained by the manufacturing method of the present invention will be described in more detail below with reference to examples. Note that the examples shown below are merely examples of the grain-oriented electrical steel sheet according to the present embodiment, and the grain-oriented electrical steel sheet according to the present embodiment is not limited to the examples shown below.

[0068] A slab having a chemical composition containing, in mass fractions, 3.0% Si, 0.08% C, 0.05% acid-soluble Al, 0.01% N, 0.12% Mn, 0.05% Cr, 0.04% Cu, 0.01% P, 0.02% Sn, 0.01% Sb, 0.005% Ni, 0.007% S, 0.001% Se, with the remainder being Fe and impurities, was hot rolled to obtain a hot-rolled steel sheet having a thickness of 2.3 mm.

[0069] Next, the above hot-rolled steel sheets were subjected to an annealing treatment under temperature conditions of heating at 1000° C. for 1 minute. After the annealing treatment, cold rolling was performed to obtain a cold-rolled steel sheet having a thickness of 0.23 mm. Subsequently, the cold-rolled steel sheet was subjected to a decarburization annealing treatment under the temperature condition of heating at 800°C for 2 minutes, and then an annealing separator containing magnesia (MgO) as a main component was applied to the surface of the cold-rolled steel sheet.

[0070] Next, the cold-rolled steel sheet coated with the annealing separator was subjected to a finish annealing treatment under the temperature condition of heating at 1200°C for 20 hours. As a result, a steel sheet was obtained that had the above-mentioned chemical composition, had a crystal orientation controlled so that the magnetization easy axis of the crystal grains coincided with the rolling direction, and had a glass film formed on the surface.

[0071] The surface of the finish annealed sheet was subjected to light pickling treatment using the light pickling solution and conditions shown in Table 1. Then, an insulating coating solution containing colloidal silica and phosphate was applied onto the glass film, and flattening annealing was performed under temperature conditions of heating at 850°C for 1 minute, finally obtaining a grain-oriented electrical steel sheet with a glass film and an insulating film.

[0072] As an example (invention example), light pickling was performed using a light pickling solution within the range of the present invention, and as a comparative example, a light pickling solution outside the range of the present invention was used. The components, concentrations, pH values, and immersion times of the light pickling solutions used in the examples and comparative examples are shown in Table 1.

[0073] [Table 1]

[0074] After light pickling, the eddy current loss and hysteresis loss of the electrical steel sheets of the above-mentioned Examples and Comparative Examples were measured by the above-mentioned measuring method.

[0075] Subsequently, the surface of the steel sheet was irradiated with a laser and an electron beam, respectively, to impart thermal strain to the surface of the steel sheet.

[0076] The laser light irradiation device used was a fiber laser manufactured by IPG Inc. The laser light irradiation conditions were adjusted as follows: laser output 300 W, laser light focusing spot diameter (86% diameter) in the rolling direction was 50 μm, laser light focusing spot diameter (86% diameter) in the plate width direction was 100 μm, laser scanning speed was 50 m / s, and laser scanning pitch (spacing PL) was 3 mm.

[0077] The electron beam irradiation device used was a Mitsubishi Electric electron beam irradiation device. The electron beam irradiation conditions were as follows: acceleration voltage 150 kV, beam current 3.0 mA, beam irradiation diameter Φ200 μm, scanning speed 20 m / s, and irradiation interval 4 mm.

[0078] The total iron loss, eddy current loss, and hysteresis loss of the obtained electrical steel sheets of the examples and comparative examples were measured using the above-mentioned measuring method, and compared with the eddy current loss and hysteresis loss values ​​after the magnetic domain refinement treatment. The eddy current loss and hysteresis loss values ​​are those at the time of sinusoidal excitation with an excitation frequency of 50 Hz and a maximum magnetic flux density of 1.7 T. The magnetostriction λp-p at an excitation frequency of 50 Hz and excitation to 1.7 T was also measured. Table 2 shows the results before and after the magnetic domain refinement treatment by laser light irradiation, and the difference before and after the treatment. Table 3 shows the results before and after the magnetic domain refinement treatment by electron beam irradiation, and the difference before and after the treatment.

[0079] [Table 2-1] [Table 2-2]

[0080] [Table 3-1] [Table 3-2]

[0081] As shown in Tables 2 and 3, if the light pickling solution and pickling conditions after the final annealing are not within the range of the present invention, the grain-oriented electrical steel sheet subjected to the magnetic domain refinement treatment will have an improvement in eddy current loss of less than 0.07 W / kg, an increase in hysteresis loss of more than 0.02 W / kg, or a change in magnetostriction λp-p when excited at 1.7 T of more than 0.2 μm / m, or all of these will occur, resulting in a grain-oriented electrical steel sheet having desirable magnetic properties. The eddy current loss indicates the degree of the effect of the magnetic domain refinement treatment, and in order to obtain a low iron loss material, it is preferable that the eddy current loss is larger. However, the increase in hysteresis loss due to the magnetic domain refinement treatment is a contradictory phenomenon that can be said to be a side effect of the magnetic domain refinement treatment, and it is preferable that the eddy current loss is smaller in order to obtain a low iron loss material. In addition, the change in the magnetostriction peak value due to the magnetic domain refinement treatment indicates the magnitude of modulation of the magnetostriction waveform, and it is preferable that the change is smaller in order to obtain a low-noise transformer.

[0082] From these results, it is apparent that by carrying out pickling treatment under light pickling conditions within the range of the present invention, noise was further reduced compared to the comparative example.

Claims

1. In order, By mass%, Si: 2.5% to 4.5%, Mn: 0.01% to 0.15%, C: 0.020-0.100%, S and Se: 0.001 to 0.050% in total, Acid-soluble Al: 0.010 to 0.050%, N: 0.002-0.015%, Cr: 0.300% or less, Cu: 0.400% or less, P: 0.500% or less, Sn: 0.300% or less, Sb: 0.300% or less, Ni: 1.000% or less, A step of hot rolling a slab containing Bi: 0.020% or less and the balance being Fe and impurities to obtain a hot rolled steel sheet; A step of subjecting the hot-rolled steel sheet to hot-rolled sheet annealing to obtain a hot-rolled annealed sheet; A step of cold rolling the hot-rolled annealed sheet to obtain a cold-rolled steel sheet; A step of subjecting the cold-rolled steel sheet to decarburization annealing; A step of applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after decarburization annealing, and then performing finish annealing to obtain a finish annealed sheet; A step of subjecting the finish annealed sheet to light pickling to remove the annealing separator; A process of applying an insulating coating liquid to the steel sheet from which the annealing separator has been removed, and performing flattening annealing; a step of subjecting the obtained flattened annealed sheet to a magnetic domain refining treatment by a thermal distortion imparting means; A method for producing a grain-oriented electrical steel sheet comprising: The light pickling solution contains one or more elements selected from Cu, Hg, Ag, Pb, Cd, Co, Zn, and Ni, and the total concentration of each element is 0.0001 to 0.1000 mass%, The pH is -1 or more and 5 or less, The liquid temperature is 15°C or higher and 100°C or lower, The time for which the finish annealed sheet is immersed in the light pickling solution is 5 seconds or more and 200 seconds or less. A method for producing a grain-oriented electrical steel sheet comprising the steps of:

2. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the thermal distortion imparting means is selected from the group consisting of a laser and an electron beam.

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