Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/16—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of sheets
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/0206—Manufacturing of magnetic cores by mechanical means
  • H01F41/0233—Manufacturing of magnetic circuits made from sheets
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/008—Heat treatment of ferrous alloys containing Si
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1277—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a particular surface treatment
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1294—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a localised treatment
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/147—Alloys characterised by their composition
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/24—Magnetic cores
  • H01F27/245—Magnetic cores made from sheets, e.g. grain-oriented
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/33—Arrangements for noise damping
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2201/00—Treatment for obtaining particular effects
  • C21D2201/05—Grain orientation
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
  • H01F2027/348—Preventing eddy currents

Definitions

• the present invention relates to a grain-oriented electrical steel sheet and a manufacturing method thereof.
• This application claims priority based on Japanese Patent Application No. 2023-073594, filed on April 27, 2023, the contents of which are incorporated herein by reference.
• Grain-oriented electrical steel sheets are soft magnetic materials and are primarily used as iron core materials for transformers, and therefore require magnetic properties such as high magnetization characteristics and low core loss.
• 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, it is desirable to have as low iron loss as possible.
• the level of iron loss is affected by factors such as magnetic susceptibility, sheet thickness, coating tension, amount of impurities, electrical resistivity, crystal grain size, and magnetic domain size.
• Patent Document 1 shows that it is possible to easily reduce iron loss in both the L direction and
• Patent Document 2 discloses a method for manufacturing a grain-oriented electrical steel sheet in which linear closure domains are formed at approximately regular intervals and substantially perpendicular to the rolling direction of the steel sheet by scanning and irradiating the steel sheet with a continuous wave laser beam, thereby improving the iron loss characteristics.
• Patent Document 2 discloses that a grain-oriented electrical steel sheet with reduced iron loss can be obtained by using a laser in a TEM 00 mode in which the laser light intensity distribution in a cross section perpendicular to the beam propagation direction has the maximum intensity near the center of the optical axis, and by setting the focusing diameter d [mm] of the irradiation beam in the rolling direction, the scanning linear velocity V [mm/s] of the laser beam, and the average laser output P [W] within the ranges of 0 ⁇ d ⁇ 0.2 and 0.001 ⁇ P/V ⁇ 0.012.
• Patent Document 3 discloses a method for manufacturing a grain-oriented electrical steel sheet in which a laser beam is irradiated at equal intervals onto the surface of the grain-oriented electrical steel sheet to improve the magnetic properties.
• the laser is a pulsed Q-switched CO2 laser
• the irradiation beam shape is an ellipse with its major axis in the sheet width direction
• the irradiation power density of the laser pulse is set to be equal to or less than the coating damage threshold value on the steel sheet surface, thereby suppressing the occurrence of laser irradiation marks
• by setting the major axis length of the elliptical beam to be equal to or greater than the pulse beam irradiation interval in the sheet width direction successive pulse beams are superimposed on the steel sheet surface, providing accumulated irradiation energy necessary and sufficient for improving magnetic properties, suppressing laser irradiation marks, and obtaining an efficient magnetic domain control effect.
• magnetostriction of grain-oriented electromagnetic steel sheets is one of the causes of noise and vibration in transformers. Magnetostriction here refers to vibrations observed in the rolling direction of grain-oriented electromagnetic steel sheets, which are caused by slight changes in the external shape of the grain-oriented electromagnetic steel sheets due to changes in the strength of magnetization when the grain-oriented electromagnetic steel sheets are excited with alternating current. The magnitude of this magnetostriction is very small, on the order of 10-6 , but the magnetostriction generates vibrations in the iron core, which propagate to external structures such as the tank of the transformer and become noise.
• Patent Document 4 discloses a grain-oriented electrical steel sheet that has low core loss and produces little noise when incorporated into a transformer.
• Patent Document 4 discloses that closure domain regions are formed in which the width in the rolling direction on the steel sheet surface changes periodically, and that each of the closure domain regions satisfies the following conditions: a ratio (Wmax/Wmin) of the maximum width Wmax in the rolling direction on the steel sheet surface to the minimum width Wmin is 1.2 to 2.2, an average width Wave in the rolling direction on the steel sheet surface is 80 ⁇ m to 250 ⁇ m, a maximum depth D in the sheet thickness direction is 32 ⁇ m or more, and (Wave ⁇ D)/s is 0.0007 mm to 0.0016 mm, thereby realizing a better balance between iron loss and noise than before.
• Patent Document 5 discloses a grain-oriented electrical steel sheet in which local strain is introduced in a direction transverse to the rolling direction at periodic intervals with respect to the rolling direction, in which linear closure domain parts are formed in the vicinity of the strain, and in a demagnetized state, the grain-oriented electrical steel sheet has magnetic domains with a rolling-direction length of 1.2 mm or more extending from the closure domain part in the rolling direction, and further, the magnetic domains are formed at an average of 1.8 or more per mm in a region along the closure domain parts, and when the line spacing of the closure domain parts is s (mm), the width w (mm) of the closure domain parts and the depth h ( ⁇ m) of the closure domain parts in the sheet thickness direction satisfy the relationships 4 mm ⁇ s ⁇ 1.5 mm and hw/s ⁇ 0.9 ⁇ m.
• Patent Document 5 suggests that an index of the amount of strain introduced, expressed in hw/s, affects iron loss and noise.
• Patent Document 6 discloses a grain-oriented electrical steel sheet having closure domains formed linearly across the rolling direction and periodically in the rolling direction, characterized in that, with regard to strain distribution in a rolling direction cross section of a region in which the closure domains are formed, the maximum tensile strain in the sheet thickness direction is 0.45% or less, and the maximum tensile strain t (%) and maximum compressive strain c (%) in the rolling direction satisfy the relationship t+0.06 ⁇ t+c ⁇ 0.35, and when assembled into a transformer, the iron loss W17/ 50 is 0.90 W/kg or less, and the noise is less than 45 dBA.
• an object of the present invention is to provide a grain-oriented electrical steel sheet that has excellent iron loss characteristics and noise characteristics (low iron loss and low noise when incorporated into a transformer: excellent balance between iron loss and noise), and a manufacturing method thereof.
• the present inventors have investigated grain-oriented electrical steel sheets with low iron loss and excellent noise characteristics. As a result, they have found that while distortion caused by irradiation with energy rays such as lasers is essential for reducing iron loss, distortion caused by irradiation with energy rays varies greatly depending on the location, and there exists distortion that does not contribute to reducing iron loss and deteriorates noise characteristics. As a result of further investigations, the inventors have found that by irradiating the energy beam while only the surface layer is heated, it is possible to reduce the proportion of distortion that does not contribute to low iron loss and deteriorates noise characteristics, thereby improving the iron loss/noise balance.
• the present invention has been made in view of the above findings.
• the maximum value of the compressive elastic stress in the rolling direction measured using EBSD is 100 MPa or less, and the proportion of regions in which the compressive elastic stress in the rolling direction of 20 MPa or more has been introduced relative to the regions in which the compressive elastic stress has been introduced is 50% or more in terms of area ratio.
• a method for producing a grain-oriented electrical steel sheet includes a heating step of heating a steel sheet, and an irradiation step of irradiating the steel sheet after the heating step with an energy ray, In the irradiation step, the energy rays are irradiated in a state in which the temperature of the surface of the steel plate is 200° C. or higher and the temperature at a position 20 ⁇ m from the surface in the plate thickness direction is 100° C. or lower.
• the above aspect of the present invention makes it possible to provide a grain-oriented electrical steel sheet with excellent iron loss and noise characteristics, and a method for manufacturing the same.
• This section describes the grain-oriented electromagnetic steel sheet according to one embodiment of the present invention (the grain-oriented electromagnetic steel sheet according to this embodiment) and the manufacturing method of the grain-oriented electromagnetic steel sheet according to this embodiment.
• a strain that generates a large compressive elastic stress of more than 100 MPa in the rolling direction is introduced near the surface of the steel sheet irradiated with the laser, and a strain that generates a medium compressive elastic stress (about 20 to 100 MPa) in the rolling direction is introduced closer to the center of the sheet thickness direction than the strain, and a strain that generates a relatively small compressive elastic stress (less than 20 MPa) is introduced around them.
• a strain that generates the compressive elastic stress in the rolling direction that contributes to improving iron loss, so it is essential to control the distribution of the compressive elastic stress in the rolling direction.
• the strain that generates a large compressive elastic stress and the strain that generates a relatively small compressive elastic stress have a small contribution to reducing iron loss and deteriorate noise characteristics. Therefore, in the grain-oriented electrical steel sheet according to this embodiment, the strain that generates a large compressive elastic stress is not present, and the presence of the strain that generates a relatively small compressive elastic stress is suppressed, thereby increasing the proportion of the strain that generates a medium-strength compressive elastic stress in the strain that is introduced. The presence of strain can be evaluated by elastic stress.
• the maximum value of compressive elastic stress in the rolling direction measured using EBSD is 100 MPa or less, and the proportion of regions where a compressive elastic stress of 20 MPa or more has been introduced to the total number of regions where a compressive elastic stress has been introduced is 50% or more in terms of area ratio.
• the maximum value of the compressive elastic stress in the rolling direction exceeds 100 MPa (there is a strain that generates a large compressive elastic stress), the noise characteristics deteriorate.
• the ratio of the region with a compressive elastic stress of 20 MPa or more is less than 50% in area ratio (the ratio of low-intensity strain in the strain-introduced region is large), the noise characteristics deteriorate, or the introduced strain is small, so that the iron loss increases (iron loss characteristics deteriorate).
• the maximum value of the compressive elastic stress in the rolling direction is more than 60 MPa and not more than 100 MPa.
• the ratio of the region into which a strain of a strength causing a compressive elastic stress of 20 MPa or more is introduced is 50% or more in terms of area ratio.
• the maximum value of the compressive elastic stress in the rolling direction and the proportion of the compressive elastic stress of 20 MPa or more introduced are determined by the following method.
• a map measurement is performed by electron backscatter diffraction (EBSD) on a cross section (in grain-oriented electrical steel sheets, the energy beam is generally irradiated while being scanned in the sheet width direction, so that the cross section is usually in the sheet thickness direction perpendicular to the scanning direction of the energy beam) in the rolling direction and in the sheet thickness direction.
• the measurement area is a region having a width twice as wide as the irradiation width of the energy beam and centered on the irradiation position of the energy beam.
• the EBSD analysis surface needs to be subjected to a surface treatment to remove mechanical distortion due to polishing or cross-section processing.
• a method may be used in which the analysis surface is mirror-polished and then the processing distortion layer due to polishing is sputtered and removed with an argon ion beam.
• an electron beam is irradiated in steps of 2 ⁇ m or less to a sample whose observation surface is tilted 70 degrees with respect to the irradiation direction of the electron beam to obtain an EBSD image.
• the obtained image is saved at 956 x 956 pixels, and a strain calculation is performed using CrossCourt4 from BLG Vantage to calculate the magnitude and direction of the strain, and the elastic stress in the rolling direction is calculated from the results.
• the reference point for the strain and elastic stress may be the point farthest from the energy beam irradiation position within the measurement range of the cross section of the grain-oriented electrical steel sheet, or in its vicinity (within a range of about 10 pixels).
• a region where a compressive elastic stress in the rolling direction of 10 MPa or more exists is defined as a region where elastic stress has been introduced, and the maximum value of the compressive elastic stress in the rolling direction in this region where elastic stress has been introduced and the area ratio of the region where a compressive elastic stress in the rolling direction of 20 MPa or more has been introduced are calculated.
• a glass coating and/or an insulating coating which will be described later, is formed on the surface, the cross section of the base steel sheet is the object of measurement, since no elastic stress is introduced into the glass coating or the insulating coating.
• grain-oriented electrical steel sheet comes into contact with rolling rolls, resulting in the formation of unevenness in the rolling direction.
• the rolling direction of grain-oriented electrical steel sheet can be determined by visually checking the unevenness.
• the grain-oriented electrical steel sheet according to the present embodiment may be made of a steel sheet, but may have a glass coating or an insulating coating on the steel sheet (base steel sheet). Also, the steel sheet may have a glass coating on it, and an insulating coating on the glass coating.
• the grain-oriented electrical steel sheet according to this embodiment is characterized by the distribution of elastic stress introduced into the steel sheet as described above. Therefore, the chemical compositions of the base steel sheet, glass coating, and insulating coating of the grain-oriented electrical steel sheet are not limited, but for example, the base steel sheet, glass coating, and insulating coating having the chemical compositions shown below can be used.
• the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment may be a known steel sheet, and the chemical composition is not particularly limited. However, in order to obtain the characteristics generally required for a grain-oriented electrical steel sheet, it is preferable that the following components (elements) constituting the chemical composition are included. In the present embodiment, the percentages relating to the content of each element are mass percentages unless otherwise specified. When the grain-oriented electrical steel sheet according to the present embodiment does not have a glass coating or an insulating coating, it can be said that the chemical composition of the base steel sheet is the chemical composition of the grain-oriented electrical steel sheet.
• C 0.010% or less
• C (carbon) is an element effective for controlling the structure of the steel sheet in the process up to the completion of the decarburization annealing process in the manufacturing process.
• the C content is preferably 0.010% or less.
• the C content is more preferably 0.005% or less. The lower the C content, the more preferable it is, but even if the C content is reduced to less than 0.0001%, the effect of grain control is saturated and the manufacturing cost is only increased. Therefore, the C content may be 0.0001% or more.
• Si 3.00-4.00%
• Silicon (Si) is an element that increases the electrical resistance of grain-oriented electrical steel sheets and improves their core loss characteristics. If the Si content is less than 3.00%, a sufficient eddy current loss reduction effect cannot be obtained. Therefore, the Si content is preferably 3.00% or more, more preferably 3.10% or more, and further preferably 3.20% or more. On the other hand, if the Si content exceeds 4.00%, the grain-oriented electrical steel sheet becomes embrittled and the sheet passing property is significantly deteriorated. In addition, the workability of the grain-oriented electrical steel sheet is deteriorated, and the steel sheet is likely to break during rolling. For this reason, the Si content is preferably 4.00% or less, more preferably 3.80% or less, and further preferably 3.70% or less.
• Mn 0.01-0.50% Mn (manganese) is an element that combines with S to form MnS during the manufacturing process. These precipitates act as inhibitors (suppressors of normal grain growth) and cause secondary Mn also enhances the hot workability of steel. If the Mn content is less than 0.01%, the above effects cannot be fully obtained. Therefore, the Mn content is preferably 0.01% or more, and more preferably 0.02% or more. On the other hand, if the Mn content exceeds 0.50%, secondary recrystallization does not occur, and the magnetic properties of the steel deteriorate. The Mn content is preferably 0.50% or less, more preferably 0.20% or less, and further preferably 0.10% or less.
• N 0.010% or less
• N nitrogen
• the N content is preferably 0.010% or less.
• the N content is more preferably 0.008% or less.
• the lower limit of the N content is not particularly specified, but reducing the N content to less than 0.001% would only increase the manufacturing cost, so the N content may be 0.001% or more.
• Sol. Al 0.020% or less
• Sol. Al (acid-soluble aluminum) is an element that combines with N to form AlN, which functions as an inhibitor, during the manufacturing process of the grain-oriented electrical steel sheet.
• the sol. Al content of the steel sheet (base steel sheet) exceeds 0.020%, the inhibitor remains excessively in the steel sheet, and the magnetic properties are reduced. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the sol. Al content is preferably 0.020% or less.
• the sol. Al content is more preferably 0.010% or less, and further preferably less than 0.001%.
• the lower limit of the sol. Al content is not particularly specified, but even if it is reduced to less than 0.0001%, the manufacturing cost will only increase. Therefore, the sol. Al content may be 0.0001% or more.
• S 0.010% or less
• S (sulfur) is an element that combines with Mn in the manufacturing process to form MnS, which functions as an inhibitor.
• the S content is preferably 0.010% or less.
• the S content in the grain-oriented electrical steel sheet is preferably as low as possible. For example, it is less than 0.001%.
• the S content in the base steel sheet of the grain-oriented electrical steel sheet may be 0.0001% or more.
• P phosphorus
• P is an element that reduces workability in rolling. By setting the P content to 0.030% or less, it is possible to suppress excessive reduction in rolling workability and to suppress breakage during manufacturing. From this viewpoint, it is preferable that the P content is 0.030% or less.
• the P content is more preferably 0.020% or less, and further preferably 0.010% or less.
• the lower limit of the P content may include 0%, but since the detection limit of chemical analysis is 0.0001%, the substantial lower limit of the P content in practical steel sheets is 0.0001%.
• P is also an element that has the effect of improving the texture and the magnetic properties. To obtain this effect, the P content may be 0.001% or more, or may be 0.005% or more.
• the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment may contain, for example, the above-mentioned elements, with the balance being Fe and impurities.
• Cr, Sn, Cu, Se, Sb, and Mo may also be contained in the ranges shown below.
• W, Nb, Ti, Ni, Bi, Co, and V are contained in a total of 1.0% or less, this does not impair the effect of the grain-oriented electrical steel sheet according to this embodiment.
• impurities refer to elements that are mixed in from raw materials such as ore or scrap, or from the manufacturing environment, during industrial production of the base steel sheet, and 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.
• Cr 0-0.50% Cr (chromium) is an element that contributes to increasing the Goss orientation occupancy rate in the secondary recrystallized structure and improves the magnetic properties.
• the Cr content is set to 0.01% or more. It is preferable that the content of C be 0.01% or more, more preferably 0.02% or more, and further preferably 0.03% or more.
• the Cr content is preferably 0.50% or less. is more preferably 0.30% or less, and further preferably 0.10% or less.
• Sn 0-0.50%
• Sn (tin) is an element that contributes to improving magnetic properties through controlling the primary recrystallized structure.
• the Sn content is 0.01% or more.
• the amount is more preferably 0.02% or more, and further preferably 0.03% or more.
• the Sn content is preferably 0.50% or less.
• the amount is more preferably 0.30% or less, and further preferably 0.10% or less.
• Cu 0-0.50%
• Cu (copper) is an element that contributes to an increase in the Goss orientation occupancy rate in the secondary recrystallized structure.
• Cu is an optional element in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment.
• the lower limit of the Cu content is 0%, but in order to obtain the above-mentioned effects, the Cu content is preferably 0.01% or more.
• the Cu content is more preferably 0.02% or more. More preferably, it is 0.03% or more.
• the Cu content exceeds 0.50%, the steel sheet becomes embrittled during hot rolling.
• the Cu content is preferably 50% or less, more preferably 0.30% or less, and further preferably 0.10% or less.
• Se is an element that has a magnetic property improving effect. Therefore, it may be contained.
• the content is set to 0.001% or more in order to effectively exhibit the magnetic property improving effect.
• the Se content is more preferably 0.003% or more, and further preferably 0.006% or more.
• the Se content is preferably 0.020% or less.
• the Se content is more preferably 0. It is preferably 0.015% or less, and more preferably 0.010% or less.
• Sb 0-0.50% Sb (antimony) is an element that has a magnetic property improving effect. Therefore, it may be contained. When Sb is contained, the content is set to 0.005% or more in order to effectively exhibit the magnetic property improving effect.
• the Sb content is more preferably 0.01% or more, and further preferably 0.02% or more.
• the Sb content is preferably 0.50% or less.
• the Sb content is more preferably It is preferably 0.30% or less, and more preferably 0.10% or less.
• Mo 0-0.10%
• Mo molybdenum
• Mo is an element that has a magnetic property improving effect. Therefore, it may be contained.
• the Mo content is set to 0.01% in order to effectively exhibit the magnetic property improving effect.
• the Mo content is more preferably 0.02% or more, and further preferably 0.03% or more.
• Mo content is more preferably 0.08% or less, and further preferably 0.05% or less.
• the chemical composition of the base steel sheet of the grain-oriented electromagnetic steel sheet according to this embodiment (when the grain-oriented electromagnetic steel sheet according to this embodiment consists only of a base steel sheet, it can also be said to be the chemical composition of the grain-oriented electromagnetic steel sheet according to this embodiment) can be, for example, one that contains the essential elements described above, with the balance consisting of Fe and impurities, or one that contains the essential elements described above and further contains one or more optional elements, with the balance consisting of Fe and impurities.
• the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment is determined by a known composition analysis method. Specifically, a drill is used to generate chips from the base steel sheet, the chips are collected, and the collected chips are dissolved in acid to obtain a solution. ICP-AES is performed on the solution to perform elemental analysis of the chemical composition.
• the Si content in the chemical composition of the base steel sheet is determined by the method (silicon quantitative determination method) specified in JIS G 1212 (1997). Specifically, when the above-mentioned cutting chips are dissolved in acid, silicon oxide is precipitated, and this precipitate (silicon oxide) is filtered out with filter paper and the mass is measured to determine the Si content.
• the C content and S content are determined by the well-known high-frequency combustion method (combustion-infrared absorption method). Specifically, the above-mentioned solution is combusted by high-frequency heating in an oxygen stream, and the generated carbon dioxide and sulfur dioxide are detected to determine the C content and S content.
• the N content is determined by the well-known inert gas fusion-thermal conductivity method. However, if a glass coating and/or an insulating coating (tension-applying insulating coating) is formed on the surface, the glass coating and insulating coating shall be removed before the measurement.
• the insulating coating can be removed by immersing the grain-oriented electrical steel sheet in an aqueous sodium hydroxide solution containing 30 to 50 mass % NaOH and 50 to 70 mass % H 2 O at 80 to 90° C. for 7 to 10 minutes.
• the grain-oriented electrical steel sheet from which the insulating coating has been removed is washed with water, and then dried with a hot air blower for just under one minute (for example, about 10 to 50 seconds).
• the dried grain-oriented electrical steel sheet (grain-oriented electrical steel sheet not provided with an insulating coating) can be immersed in an aqueous hydrochloric acid solution containing 30 to 40 mass % HCl at 80 to 90° C. for 1 to 10 minutes to remove the glass coating.
• the base steel sheet after immersion is rinsed with water, and then dried with a hot air blower for just under one minute (for example, about 10 to 50 seconds), whereby the base steel sheet can be removed from the grain-oriented electrical steel sheet having the glass coating and the insulating coating.
• the thickness of the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment is not limited, but is preferably 0.17 to 0.30 mm when considering application to the iron core of a transformer, which requires low noise and low vibration as well as low iron loss.
• special equipment is required to manufacture a base steel sheet with a thickness of less than 0.17 mm, which is undesirable from the standpoint of production, such as increasing manufacturing costs. Therefore, the industrially preferred lower limit of the thickness is 0.17 mm.
• the grain-oriented electrical steel sheet according to the present embodiment may have a known glass coating formed on the surface of the base steel sheet.
• the glass coating is an inorganic coating mainly composed of magnesium silicate.
• the glass coating is formed by the reaction of an annealing separator containing magnesia (MgO) applied to the surface of the base steel sheet with the components of the surface of the base steel sheet during finish annealing, and has a composition derived from the components of the annealing separator and the base steel sheet, and is composed of a structure containing a main phase (50 area % or more) Mg 2 SiO 4 phase and a MgAl 2 O 4 phase. In addition to these phases, precipitates may be contained in an amount of about 1 area % or less.
• MgO magnesia
• a known insulating coating may be formed on the surface of the base steel sheet or on the surface of the glass coating.
• the insulating coating imparts electrical insulation to the grain-oriented electrical steel sheet, thereby reducing eddy current loss and improving the iron loss characteristics of the grain-oriented electrical steel sheet (reducing iron loss).
• the insulating coating also provides various other characteristics such as corrosion resistance, heat resistance, and slipperiness. Furthermore, the insulating coating has the function of applying tension to the grain-oriented electrical steel sheet.
• the insulating coating is formed, for example, by applying a coating liquid mainly composed of metal phosphate and silica to the surface of the glass coating and baking it.
• the grain-oriented electrical steel sheet according to this embodiment has the above-mentioned elastic stress distribution (strain distribution for generating elastic stress distribution), the effect can be obtained regardless of the manufacturing method. Therefore, although the manufacturing method is not limited, the grain-oriented electrical steel sheet according to this embodiment can be obtained according to the manufacturing method described below.
• the energy rays are irradiated in a state in which the temperature of the surface of the steel plate is 200° C. or higher and the temperature at a position 20 ⁇ m from the surface in the plate thickness direction is 100° C. or lower.
• the steel sheet (grain-oriented electrical steel sheet that has been finish-annealed and has not been subjected to magnetic domain control) is heated prior to irradiation with energy rays.
• the energy rays are irradiated in a state where the temperature of the surface of the steel sheet is 200° C. or higher and the temperature at a position 20 ⁇ m from the surface in the sheet thickness direction is 100° C. or lower. Therefore, in the heating step, it is necessary to rapidly heat only the surface layer close to the surface.
• the heating method is not limited, but for example, in the case of roll heating or heating by radiation heat, although the surface is heated, a sufficient temperature rise rate cannot be ensured.
• the temperature rises to the inside due to heat transfer, and it is not possible to achieve a state in which the surface temperature is 200°C or more and the temperature at a position 20 ⁇ m from the surface is 100°C or less.
• the steel sheet is heated to the inside, so it is not possible to achieve a state in which the surface temperature is 200°C or more and the temperature at a position 20 ⁇ m from the surface is 100°C or less. Therefore, it is preferable to apply high-frequency heating as a method for rapidly heating only the surface layer.
• the frequency is 1000 Hz or more.
• ⁇ Irradiation step> the steel sheet after the heating step is irradiated with energy rays in a state in which the surface temperature is 200° C. or higher and the temperature at a position 20 ⁇ m from the surface in the sheet thickness direction is 100° C. or lower. If the time from the completion of the heating step becomes long, even if the surface temperature is 200° C. or higher and the temperature at a position 20 ⁇ m from the surface in the plate thickness direction is 100° C. or lower at the time of the completion of the heating step, the temperature difference between the surface temperature and the temperature at a position 20 ⁇ m from the surface in the plate thickness direction will gradually decrease due to heat transfer, and the above-mentioned temperature distribution state cannot be maintained.
• the irradiation step within 10 seconds from the completion of the heating step.
• the steel sheet (grain-oriented electrical steel sheet) has a glass coating or an insulating coating on the surface of the base steel sheet
• the "surface" used as the reference for the temperature measurement position is the surface of the base steel sheet.
• the surface temperature and the temperature at a position 20 ⁇ m in the thickness direction can be measured using a thermocouple attached to the surface and an embedded thermocouple.
• the temperature at a position 20 ⁇ m from the surface in the thickness direction can be calculated using high-frequency heating simulation software.
• JMAG manufactured by Daiichi Kiden Co., Ltd. can be used as the software.
• a grain-oriented electrical steel sheet is obtained having an elastic stress distribution in which the maximum compressive elastic stress in the rolling direction inside the steel sheet is 100 MPa or lower and the proportion of regions where a compressive elastic stress in the rolling direction of 20 MPa or higher is introduced to the total of regions where compressive elastic stress has been introduced is 50% or higher in terms of area ratio.
• strain that generates a large compressive elastic stress in the rolling direction is introduced near the surface of the steel plate irradiated with the laser, strain that generates a medium compressive elastic stress is introduced closer to the center in the plate thickness direction than that strain, and strain that generates a small compressive elastic stress is introduced around these.
• strain and the associated elastic stress
• the temperature distribution in the grain-oriented electrical steel sheet at the time of irradiation with the energy beam is as described above, the introduction of strain by the laser irradiation hardly occurs near the surface, which is at a high temperature, and only strain that generates a small compressive elastic stress in the rolling direction remains. This makes it possible to suppress the generation of strain that generates a large compressive elastic stress. Furthermore, even in the medium-temperature and low-temperature portions, which are lower in temperature than near the surface, the strain introduced by the energy beam irradiation is weaker than in the case where no pre-heating is performed, and the generation of strain that generates a small compressive elastic stress is also suppressed.
• the strain that generates a large compressive elastic stress and a small compressive elastic stress, which do not contribute to magnetic domain refining and deteriorate the noise characteristics, and the strain that generates a small compressive elastic stress are suppressed, and an ideal state for obtaining an excellent iron loss/noise balance is obtained, in which the proportion of strain that generates a medium compressive elastic stress that contributes to magnetic domain refining is high.
• the surface temperature is 200° C. or higher during energy beam irradiation, if the temperature at a position 20 ⁇ m from the surface is also high, only distortion that generates a small compressive elastic stress in the rolling direction remains, and sufficient magnetic domain refinement effect cannot be obtained.
• the temperature at a position 20 ⁇ m from the surface is 100° C. or lower, if the surface temperature is also less than 200° C., the heating effect cannot be obtained.
• the energy beam to be irradiated is not limited as long as it can induce strain by heat, but in a method of periodically heating the steel sheet such as a pulsed laser, strain is induced deep from the surface of the steel sheet by melting the steel sheet, so the irradiation of the energy beam is limited to continuous irradiation.
• the laser is preferably a fiber laser.
• the steel sheet subjected to the heating step and the irradiation step may be a known grain-oriented electrical steel sheet, and the manufacturing method thereof is not particularly limited. That is, a grain-oriented electrical steel sheet manufactured by any manufacturing method may be subjected to heating and laser irradiation. A typical grain-oriented electrical steel sheet is manufactured by a manufacturing method including the following steps.
• a hot rolling process in which a steel piece such as a slab is heated and hot-rolled into a hot-rolled steel sheet;
• a hot-rolled sheet annealing process for subjecting the hot-rolled steel sheet to hot-rolled sheet annealing;
• a pickling process for pickling the hot-rolled steel sheet after the hot-rolled steel sheet annealing process;
• a cold rolling process in which the hot-rolled steel sheet after the pickling process is cold-rolled once or multiple times including annealing to obtain a cold-rolled steel sheet; a decarburization annealing step of subjecting the cold-rolled steel sheet to decarburization annealing;
• a finish annealing process in which an annealing separator mainly composed of MgO powder is applied to the front and back surfaces of the cold-rolled steel sheet after the decarburization annealing process, which is the base steel sheet, and then dried and finish annealed to form a glass coating;
• Al 0.010 to 0.040%, Mn: 0.01 to 0.50%, N: 0.020% or less, S: 0.005 to 0.040%, P: 0.030% or less, Cu: 0 to 0.50%, Cr: 0 to 0.50%, Sn: 0 to 0.50%, Se: 0 to 0.020%, Sb: 0 to 0.50%, Mo: 0 to 0.10%, with the balance being Fe and impurities.
• the grain-oriented electrical steel sheet of the present invention will be described in more detail using examples.
• the examples shown below are merely examples of the grain-oriented electrical steel sheet and its manufacturing method according to the present invention, and the grain-oriented electrical steel sheet and its manufacturing method according to the present invention are not limited to the examples below.
• a number of samples measuring 500 mm in the rolling direction and 100 mm in the sheet width direction were cut out from a grain-oriented electrical steel sheet having a thickness of 0.23 mm and a chemical composition containing 0.08% C, 3.20% Si, 0.12% Mn, 0.050% acid-soluble Al, with the balance being Fe and impurities, and these samples were either not heated or heated by high-frequency heating or roll heating, and laser irradiation was performed in a state in which the surface and a position 20 ⁇ m from the surface in the sheet thickness direction had temperatures shown in Table 1.
• the temperature at a position 20 ⁇ m from the surface in the sheet thickness direction was calculated using high-frequency heating simulation software. The following conditions were adopted as the laser irradiation conditions.
• Scanning direction Sheet width direction Scanning pitch PL (spacing in the rolling direction): 5.0 mm Power density Ip of laser irradiation: 500 to 10,000 (W/mm 2 ) (listed in the table) Input energy Ua: 0.1 to 5.0 (mJ/mm 2 ) (listed in the table) Laser source: Fiber laser
• the grain-oriented electrical steel sheet after laser irradiation was subjected to EBSD analysis using the method described above to determine the maximum compressive elastic stress in the rolling direction, and the ratio (area ratio in the table) of the region where a compressive elastic stress of 20 MPa or more and 100 MPa or less was introduced to the region where a compressive elastic stress was introduced (region where a compressive elastic stress in the rolling direction of 10 MPa or more exists) in a cross section parallel to the rolling direction and the sheet thickness direction.
• the noise characteristics and magnetic characteristics (iron loss) of the grain-oriented electrical steel sheets after laser irradiation were evaluated by the following method.
• the magnetostriction of the grain-oriented electrical steel sheet after laser irradiation was measured by an AC magnetostriction measurement method using a magnetostriction measurement device equipped with a laser Doppler vibrometer, an excitation coil, an excitation power supply, a magnetic flux detection coil, an amplifier, and an oscilloscope. Specifically, an AC magnetic field was applied to the sample so that the maximum magnetic flux density in the rolling direction was 1.7 T, and the change in length of the sample due to the expansion and contraction of the magnetic domains was measured with a laser Doppler vibrometer to obtain a magnetostriction signal.
• the obtained magnetostriction signal was subjected to Fourier analysis to obtain the amplitude Cn of each frequency component fn (n is a natural number equal to or greater than 1) of the magnetostriction signal.
• the A correction coefficient ⁇ n of each frequency component fn was used to obtain the magnetostriction rate level LVA (dB) shown by the following formula.
• LVA 20 ⁇ Log( ⁇ ( ⁇ ( ⁇ c ⁇ 2 ⁇ fn ⁇ n ⁇ Cn/ ⁇ 2) 2 )/Pe0)
• the present invention provides a grain-oriented electrical steel sheet with excellent iron loss and noise characteristics, and a manufacturing method thereof, and therefore has high industrial applicability.

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