WO2023007952A1 - 巻鉄心および巻鉄心の製造方法 - Google Patents
巻鉄心および巻鉄心の製造方法 Download PDFInfo
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- WO2023007952A1 WO2023007952A1 PCT/JP2022/023038 JP2022023038W WO2023007952A1 WO 2023007952 A1 WO2023007952 A1 WO 2023007952A1 JP 2022023038 W JP2022023038 W JP 2022023038W WO 2023007952 A1 WO2023007952 A1 WO 2023007952A1
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- compressive stress
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- 238000004519 manufacturing process Methods 0.000 title claims description 22
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 335
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Images
Classifications
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- 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 by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
-
- 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
-
- 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
- H01F27/24—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
- 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
Definitions
- the present invention relates to a wound core and a method for manufacturing the wound core, and more particularly to a wound core for a transformer and a method for manufacturing the wound core, which are made from grain-oriented electrical steel sheets.
- a grain-oriented electrical steel sheet having a crystal structure in which the ⁇ 001> orientation, which is the axis of easy magnetization of iron, is highly aligned in the rolling direction of the steel sheet, is particularly used as a core material for power transformers.
- Transformers are broadly classified into stacked core transformers and wound core transformers according to their core structure.
- a laminated core transformer is one in which a core is formed by stacking steel plates cut into a predetermined shape.
- a wound core transformer has a core formed by winding steel sheets. There are various requirements for transformer cores, but the most important is that the iron loss be small.
- the iron loss is small as a characteristic required for the grain-oriented electrical steel sheet that is the iron core material.
- a high magnetic flux density is also required to reduce the excitation current in the transformer and reduce copper loss.
- This magnetic flux density is evaluated by the magnetic flux density B8(T) at a magnetizing force of 800 A/m, and generally, the higher the degree of azimuth integration in the Goss orientation, the greater the B8.
- An electrical steel sheet with a high magnetic flux density generally has a small hysteresis loss and is excellent in iron loss characteristics. Also, in order to reduce iron loss, it is important to highly align the crystal orientation of the secondary recrystallized grains in the steel sheet with the Goss orientation and to reduce impurities in the steel composition.
- Patent Literature 1 and Patent Literature 2 describe a heat-resistant magnetic domain refining method in which linear grooves having a predetermined depth are formed on the surface of a steel sheet.
- the aforementioned Patent Document 1 describes means for forming grooves by means of gear-shaped rolls.
- Patent Document 2 describes means for forming linear grooves on the surface of a steel sheet by etching.
- iron loss material iron loss
- iron loss in transformers is often larger than material iron loss.
- the value obtained by dividing the iron loss value (transformer iron loss) when an electromagnetic steel sheet is used as the core of a transformer by the iron loss value of the material obtained by the Epstein test, etc. is generally called the building factor (BF) or distraction. It is called factor (DF). That is, BF generally exceeds 1 in transformers, and if BF can be reduced, transformer iron loss can be reduced.
- the factor (BF factor) that causes the transformer iron loss in the wound core transformer to increase compared to the material iron loss is the magnetic flux concentration inside the core caused by the difference in the magnetic path length, the steel plate joint.
- in-plane eddy current loss at steel plate joints will be described.
- a wound core for a transformer is provided with a cut portion for inserting a winding. After the winding is inserted into the core from the cut portion, the steel plates are joined together by providing a lap portion.
- the magnetic flux crosses the adjacent steel plate in the direction perpendicular to the plane, so an in-plane eddy current is generated. Therefore, the iron loss will increase locally.
- strain during processing also causes an increase in iron loss. If strain is introduced by slitting the steel sheet, bending during core processing, or the like, the magnetic properties of the steel sheet deteriorate, and the iron loss of the transformer increases. In the case of a wound core, it is common to perform so-called strain relief annealing, in which annealing is performed at a temperature higher than the temperature at which strain is released after processing the core.
- Patent Document 3 an electromagnetic steel sheet having magnetic properties inferior to those on the outer peripheral side of the core is placed on the inner peripheral side of the core where the magnetic path length is short, and an electromagnetic steel sheet having magnetic properties superior to those on the inner peripheral side of the core on the outer peripheral side of the core where the magnetic path length is long. It is disclosed that by arranging the magnetic steel sheets, the concentration of the magnetic flux to the inner peripheral side of the iron core is avoided, and the iron loss of the transformer is effectively reduced.
- Patent Document 4 discloses an iron core design method that reduces transformer iron loss by controlling the concentration of magnetic flux and the resulting deterioration of iron loss by combining multiple types of magnetic steel sheets with different magnetic permeability and iron loss. .
- An object of the present invention is to provide a wound core with excellent magnetic properties and low transformer core loss without using two or more materials with different magnetic properties, and a method for manufacturing the same.
- a wound core having a flat portion and a corner portion adjacent to the flat portion, a wrap portion on the flat portion, and a bent portion on the corner portion.
- the iron loss deterioration rate under compressive stress (iron loss at compressive stress of 5 MPa) / (iron loss without compressive stress)
- the iron loss at a compressive stress of 5 MPa and the iron loss when there is no compressive stress in the above formula are iron losses (W / kg) measured under the conditions of a frequency of 50 Hz and a maximum magnetization of 1.7 T
- the iron loss at a compressive stress of 5 MPa is the iron loss measured at a compressive stress of 5 MPa in the rolling direction of the iron core material.
- a wound core having a flat portion and a corner portion adjacent to the flat portion, a wrap portion on the flat portion, and a bent portion on the corner portion. of magnetic material is wound to form a core.
- a method is adopted in which a steel sheet is wound into a cylinder, then pressed so that the corners thereof have a certain curvature, and formed into a rectangular shape.
- the corner portions of the wound core are bent in advance, and the bent steel plates are overlapped to form the wound core.
- the iron core formed by this method has bent portions (bending portions) at the corner portions.
- An iron core formed by the former method is generally called a tranco core, and an iron core formed by the latter method is generally called a uni-core or a duo-core depending on the number of steel plate joints provided.
- a structure in which a bent portion is provided at the corner formed by the latter method is suitable.
- a grain-oriented electrical steel sheet (magnetic flux density B8: 1.89 T, W17/50: 0.86 W/kg) with a thickness of 0.23 mm having one single-phase trunk core and two uni-cores having the shape shown in FIG. They were wound and shaped, and strain relief annealing was performed on one of the Truncco core and Unicore under the same conditions.
- a wound core was produced by winding 50 turns and performing no-load excitation at a magnetic flux density of 1.5 T and a frequency of 60 Hz.
- a one-turn search coil was arranged at the position shown in FIG. 4, and the magnetic flux density distribution in the iron core was investigated.
- FIG. 5 shows the maximum values of the magnetic flux densities of the iron cores of each quarter thickness from the inner winding (inner side) to the outer winding (outer side). It can be seen that both the tranco core (with strain relief annealing) and the unicore (with strain relief annealing and without strain relief annealing) have a higher magnetic flux density in the inner winding, and the concentration of magnetic flux occurs. Comparing the tranco core and the unicore, it was found that the unicore had less magnetic flux concentration.
- the reason why the concentration of magnetic flux is alleviated by providing a uni-core, that is, a bend at the corner, is presumed as follows. Deformation twins and the like remain in the bent portion of the uni-core even after the strain relief annealing, and the magnetic permeability is locally reduced compared to other portions. If such a portion with extremely low magnetic permeability exists, magnetic flux above a certain level cannot pass through. Therefore, even if there is a magnetic path length difference, it is difficult for the magnetic flux to concentrate only inside the iron core. That is, it is presumed that the concentration of magnetic flux does not occur in the inner winding portion of the uni-core compared to the truncated core which has a small magnetic permeability and does not have a bent portion.
- FIG. 6 shows the maximum values of the magnetic flux densities of the iron cores of each 1/4 thickness from the inner winding to the outer winding in the unicores produced from each material (grain-oriented electrical steel sheet).
- the ratio of the length of the outer circumference to the length of the inner circumference of the iron core (the length of the outer circumference/the length of the inner circumference) is 1.80 or less. shows the results of investigating the effect of on magnetic flux concentration.
- the iron core with a 0.23 mm thickness grain-oriented electrical steel sheet (magnetic flux density B8: 1.89 T, W17/50: 0 .86 W/kg).
- a winding of 50 turns was applied, and no-load excitation was performed at a magnetic flux density of 1.5 T and a frequency of 60 Hz.
- a one-turn search coil was arranged at the position shown in FIG. 4, and the magnetic flux density distribution in the iron core was investigated.
- concentration of FIG. 8 shows the relationship between the ratio of the length of the outer circumference to the length of the inner circumference (the length of the outer circumference/the length of the inner circumference) and the concentration of the magnetic flux inside the core in each core shape.
- the concentration of the magnetic flux inside the core was small.
- the length of the inner circumference was calculated by 2(c+d)+4f ⁇ ( ⁇ 2 ⁇ 2).
- the length of the perimeter was calculated by 2(a+b)+4e ⁇ ( ⁇ 2 ⁇ 2).
- the length of the inner circumference and the length of the outer circumference may be calculated from the length of each location as shown in Table 2, or the length of the inner circumference and the length of the outer circumference may be measured.
- FIG. 10 shows the relationship between the iron loss deterioration rate under compressive stress of the grain-oriented electrical steel sheet as the material and the transformer iron loss.
- the transformer core loss decreased in the region where the core loss deterioration rate under compressive stress was 1.50 or less.
- Iron loss deterioration due to magnetic domain disturbance due to compressive stress and iron loss increase due to residual strain and twinning in the wound core are correlated. , it is presumed that the increase in iron loss can be suppressed even when the magnetic flux is concentrated inside the iron core.
- a wound core made of a grain-oriented electrical steel sheet The wound core has a flat portion and a corner portion adjacent to the flat portion, the flat portion has a lap portion, the corner portion has a bent portion, and the wound core is viewed from the side.
- the ratio of the length of the outer circumference to the length of the inner circumference is 1.80 or less
- the grain-oriented electrical steel sheet has a magnetic flux density B8 of 1.84 T or more and 1.91 T or less when the magnetic field strength H is 800 A / m, and the iron loss deterioration rate under compressive stress obtained by the following formula is 1.50 or less.
- Iron loss deterioration rate under compressive stress (iron loss at compressive stress of 5 MPa) / (iron loss without compressive stress)
- the iron loss at a compressive stress of 5 MPa and the iron loss when there is no compressive stress in the above formula are iron losses (W / kg) measured under the conditions of a frequency of 50 Hz and a maximum magnetization of 1.7 T
- the iron loss at a compressive stress of 5 MPa is the iron loss measured at a compressive stress of 5 MPa in the rolling direction of the grain-oriented electrical steel sheet.
- Iron loss deterioration rate under compressive stress (iron loss at compressive stress of 5 MPa) / (iron loss without compressive stress)
- the iron loss at a compressive stress of 5 MPa and the iron loss when there is no compressive stress in the above formula are iron losses (W / kg) measured under the conditions of a frequency of 50 Hz and a maximum magnetization of 1.7 T
- the iron loss at a compressive stress of 5 MPa is the iron loss measured at a compressive stress of 5 MPa in the rolling direction of the grain-oriented electrical steel sheet.
- the present invention it is possible to provide a wound core with excellent magnetic properties and low transformer core loss, and a method for manufacturing the same. According to the present invention, it is possible to obtain a wound core excellent in magnetic properties with small transformer iron loss without using two or more kinds of materials having different magnetic properties (iron loss). According to the present invention, the complexity of iron core design such as arrangement of materials required when two or more kinds of materials having different magnetic properties are used is reduced, and a wound core excellent in magnetic properties with small iron loss is provided. It can be obtained with high manufacturability.
- FIG. 1 is a schematic diagram illustrating a magnetic path inside the core and a magnetic path outside the core of a wound core.
- FIG. 2 is a schematic diagram illustrating crossing of magnetic flux in the direction perpendicular to the plane of a steel plate at a steel plate joint.
- FIG. 3 is an explanatory view (side view) for explaining the shapes of experimentally produced trancocores and unicores.
- FIG. 4 is an explanatory diagram for explaining the arrangement of the search coils when examining the magnetic flux density distribution in the iron core.
- FIG. 5 is a diagram showing the results of an investigation on the magnetic flux concentration in the iron cores of the tranco core and the unicore.
- FIG. 1 is a schematic diagram illustrating a magnetic path inside the core and a magnetic path outside the core of a wound core.
- FIG. 2 is a schematic diagram illustrating crossing of magnetic flux in the direction perpendicular to the plane of a steel plate at a steel plate joint.
- FIG. 3 is an explanatory view (
- FIG. 6 is a diagram showing the result of investigating the influence of the magnetic flux density B8 of the iron core material on the magnetic flux concentration in the iron core of the uni-core.
- FIG. 7 is an explanatory diagram (side view) explaining the shape of an experimentally produced iron core.
- FIG. 8 is a diagram showing the relationship between the ratio of the length of the outer circumference to the length of the inner circumference in each iron core shape and the concentration of the magnetic flux inside the iron core.
- FIG. 9 is a diagram showing the results of investigating the influence of the magnetic flux density B8 of the iron core material on the iron loss of the unicore.
- FIG. 10 is a diagram showing the relationship between the iron loss deterioration rate under compressive stress of the iron core material and the transformer iron loss.
- FIG. 11 is an explanatory view (side view) for explaining the shape of the trunk core produced in the example.
- FIG. 12 is an explanatory view (side view) explaining the shape of the unicore produced in the example.
- a wound core having a flat portion and a corner portion adjacent to the flat portion, a wrap portion on the flat portion, and a bent portion on the corner portion;
- the length ratio of the inner circumference is 1.80 or less
- (A) is satisfied by selecting a wound core manufacturing method generally called uni-core or duo-core type.
- a known method can be adopted as a method for manufacturing the wound core. More specifically, when using a Unicore manufacturing machine manufactured by AEM, when the design size is read into the manufacturing machine, the steel plate is sheared to the size according to the design drawing, and the processed steel plate with bent parts is processed one by one. Since it is produced, the wound core can be produced by laminating the processed steel plates.
- the outer circumference and inner circumference of the iron core in the condition (B) refer to the outer circumference and inner circumference of the iron core when viewed from the side, respectively. That is, the length of the outer circumference of the iron core is measured along the outside (outer surface) of the outermost grain-oriented electrical steel sheet (raw material) of the grain-oriented electrical steel sheets (materials) that make up the wound core when the core is viewed from the side. It is the length of one turn in the winding direction of the grain-oriented electrical steel sheet, and the length of the inner circumference of the iron core is the inner side of the innermost grain-oriented electrical steel sheet among the grain-oriented electrical steel sheets that constitute the wound core.
- the upper limit of the ratio of the length of the outer circumference to the length of the inner circumference of the iron core needs to be 1.80.
- the ratio is preferably 1.70 or less, more preferably 1.60 or less.
- the lower limit of the ratio is not specified in terms of characteristics, it is determined by the relationship between the core size and the thickness because the core thickness decreases when the ratio approaches 1. As an example, the lower limit of said ratio is 1.05.
- a grain-oriented electrical steel sheet having a magnetic flux density B8 of 1.84 T or more and 1.91 T or less when the magnetic field strength H is 800 A / m is used.
- Magnetic properties are measured by the Epstein test. .
- the Epstein test is carried out by a known method such as IEC standards or JIS standards.
- the result of the single plate magnetic measurement test (SST) may be substituted.
- SST single plate magnetic measurement test
- a test sample is taken from the tip and tail ends of the steel sheet coil, the Epstein test is performed, the magnetic flux density B8 is measured, and the average value is adopted as the representative characteristic.
- materials may be selected based on the characteristic values (average values and guaranteed values) of steel sheets provided by steel material manufacturers.
- the magnetic flux density B8 is preferably 1.86 T or more.
- Compressive stress is applied to the compression side at 5 MPa uniaxially in the rolling direction of the steel sheet.
- the method of applying the compressive stress is not particularly specified, for example, there is a method of fixing one side of the steel plate with a clamp or the like and applying stress from the opposite side with a pusher or the like. At that time, it is necessary to uniformly apply stress along the rolling direction so that the steel plate does not buckle.
- the steel plate may be fixed vertically in the vertical direction within a range that does not hinder the measurement.
- the iron loss in the absence of compressive stress is the iron loss measured without application of compressive stress.
- a grain-oriented electrical steel sheet having a core loss deterioration rate of 1.50 or less under the compressive stress is used as the core material.
- the iron loss deterioration rate under the compressive stress is preferably 1.45 or less.
- the lower limit of the iron loss deterioration rate under the compressive stress is not particularly limited, as an example, the lower limit of the iron loss deterioration rate under the compressive stress is 1.05.
- the properties of the grain-oriented electrical steel sheet other than (C) and (D), the composition, the manufacturing method, etc. are not particularly limited. .
- composition and manufacturing method of the grain-oriented electrical steel sheet suitable as the material for the wound core of the present invention are described below.
- the chemical composition of the grain-oriented electrical steel sheet slab may be any chemical composition that causes secondary recrystallization.
- an inhibitor for example, when using an AlN-based inhibitor, Al and N are used, and when using an MnS/MnSe-based inhibitor, appropriate amounts of Mn and Se and/or S are included. good. Of course, both inhibitors may be used together.
- the preferable contents of Al, N, S and Se are respectively Al: 0.010 to 0.065% by mass, N: 0.0050 to 0.0120% by mass, S: 0.005 to 0.030 % by mass, Se: 0.005 to 0.030% by mass.
- the present invention can also be applied to grain-oriented electrical steel sheets with limited Al, N, S, and Se contents and no inhibitors.
- the amounts of Al, N, S and Se are preferably suppressed to Al: 100 mass ppm or less, N: 50 mass ppm or less, S: 50 mass ppm or less, and Se: 50 mass ppm or less.
- C 0.08% by mass or less C is added to improve the texture of the hot-rolled sheet.
- the C content exceeds 0.08% by mass, it becomes difficult to reduce the C content to 50 ppm by mass or less at which magnetic aging does not occur during the manufacturing process, so the C content is 0.08% by mass or less.
- the lower limit of the C content it is not particularly necessary to set a lower limit because secondary recrystallization is possible even with a material that does not contain C. That is, the C content may be 0% by mass.
- Si 2.0 to 8.0% by mass Si is an element effective in increasing the electric resistance of steel and improving iron loss.
- the Si content is 2.0% by mass or more, a sufficient iron loss reduction effect can be obtained more easily.
- the Si content is 8.0% by mass or less, significant deterioration in workability can be suppressed, and a decrease in magnetic flux density can be easily suppressed. Therefore, the Si content is preferably in the range of 2.0 to 8.0% by mass.
- Mn 0.005 to 1.000% by mass
- Mn is an element necessary for improving hot workability.
- the Mn content is 0.005% by mass or more, the effect of addition can be easily obtained.
- the Mn content is 1.000% by mass or less, it becomes easier to suppress the decrease in the magnetic flux density of the product sheet. Therefore, the Mn content is preferably in the range of 0.005 to 1.000% by mass.
- Cr 0.02 to 0.20% by mass Cr is an element that promotes the formation of a dense oxide film at the interface between the forsterite film and the base iron. Although it is possible to form an oxide film without adding Cr, adding 0.02% by mass or more of Cr is expected to expand the suitable range of other components. Further, when the Cr content is 0.20% by mass or less, it is possible to suppress the oxide film from becoming too thick, and it becomes easy to suppress the deterioration of the coating peeling resistance. Therefore, the Cr content is preferably in the range of 0.02 to 0.20% by mass.
- the slab for grain-oriented electrical steel sheets preferably has the above components as basic components.
- the slab can appropriately contain the following elements in addition to the above components.
- Ni 0.03 to 1.50% by mass
- Sn 0.010 to 1.500% by mass
- Sb 0.005 to 1.500% by mass
- Cu 0.02 to 0.20% by mass
- P At least one selected from 0.03 to 0.50% by mass
- Mo 0.005 to 0.100% by mass
- Ni is an element useful for improving the structure of the hot-rolled sheet and improving the magnetic properties.
- the Ni content is 0.03% by mass or more, the effect of improving the magnetic properties can be more easily obtained.
- the Ni content is 1.50% by mass or less, it is possible to suppress the secondary recrystallization from becoming unstable, and it becomes easy to reduce the risk of deterioration of the magnetic properties of the product sheet. Therefore, when Ni is contained, the Ni content is preferably in the range of 0.03 to 1.50% by mass.
- Sn, Sb, Cu, P and Mo are elements useful for improving magnetic properties, respectively, and when the content of each component is at least the lower limit of the content of each component described above, the effect of improving the magnetic properties is more likely to be obtained. .
- the content of each component is equal to or less than the upper limit of the above-described content, it becomes easier to reduce the possibility that the growth of secondary recrystallized grains is inhibited. Therefore, when Sn, Sb, Cu, P, and Mo are contained, it is preferable that the content of each element is set in the above range.
- the balance other than the above components is unavoidable impurities and Fe mixed in the manufacturing process.
- heating temperature is preferably 1150 to 1450°C.
- Hot rolling After the heating, hot rolling is performed. After casting, hot rolling may be performed immediately without heating. In the case of thin cast slabs, hot rolling may be performed, or hot rolling may be omitted. When hot rolling is carried out, it is preferable to carry out the rolling temperature of the final pass of rough rolling at 900° C. or higher and the rolling temperature of the final pass of finish rolling at 700° C. or higher.
- the hot-rolled sheet annealing temperature is preferably in the range of 800 to 1100° C. in order to develop the Goss texture in the product sheet to a high degree. If the hot-rolled sheet annealing temperature is lower than 800°C, the band structure in the hot rolling remains, making it difficult to achieve a primary recrystallized structure with uniform grains and inhibiting the development of secondary recrystallization. There is a risk. On the other hand, if the hot-rolled sheet annealing temperature exceeds 1100° C., the grain size after the hot-rolled sheet annealing becomes too coarse, which may make it extremely difficult to achieve a uniform primary recrystallization structure.
- the intermediate annealing temperature is preferably 800°C or higher and 1150°C or lower. Also, the intermediate annealing time is preferably about 10 to 100 seconds.
- decarburization annealing After that, decarburization annealing is performed. In the decarburization annealing, it is preferable to set the annealing temperature to 750 to 900° C., the oxidizing atmosphere PH 2 O/PH 2 to 0.25 to 0.60, and the annealing time to about 50 to 300 seconds.
- the annealing separator preferably contains MgO as a main component and is applied in an amount of about 8 to 15 g/m 2 .
- finish annealing is performed for the purpose of secondary recrystallization and formation of a forsterite coating. It is preferable that the annealing temperature is 1100° C. or higher and the annealing time is 30 minutes or longer.
- a flattening process planarizing annealing
- an insulating coating can be applied to the surface of the steel sheet before or after flattening annealing.
- the insulation coating here means a coating (tension coating) that applies tension to the steel sheet in order to reduce iron loss.
- Tensile coatings include inorganic coatings containing silica, ceramic coatings by physical vapor deposition, chemical vapor deposition, and the like.
- the iron loss deterioration rate under compressive stress decreases as the tensile tension applied to the steel sheet by the surface coating (forsterite coating and insulation coating) increases.
- the thickness of the tension coating may be increased, but there is concern about deterioration of the space factor.
- an inorganic coating containing silica there is a measure such as promoting glass crystallization by raising the baking temperature. Applying a film with a low coefficient of thermal expansion such as a ceramic coating is also effective in obtaining strong tension.
- Magnetic domain refining treatment In order to reduce the iron loss of the steel sheet, it is preferable to apply a magnetic domain refining treatment.
- the magnetic domain refining technology is a technology for reducing the core loss by refining the width of the magnetic domains by introducing non-uniformity to the surface of the steel sheet by a physical method. Magnetic domain refining techniques are roughly divided into heat-resistant magnetic domain refining whose effect is not impaired by strain relief annealing, and non-heat-resistant magnetic domain refining whose effect is reduced by strain relief annealing.
- the present invention can be applied to any of a steel sheet not subjected to magnetic domain refining treatment, a steel sheet subjected to heat-resistant magnetic domain refining treatment, and a steel sheet subjected to non-heat-resistant magnetic domain refining treatment.
- Non-heat-resistant magnetic domain refining treatment generally involves irradiating a steel sheet after secondary recrystallization with a high-energy beam (laser, etc.). This is a process for refining magnetic domains by forming a field.
- a high-energy beam laser, etc.
- a steel sheet subjected to heat-resistant magnetic domain refining treatment is more suitable.
- a heat-resistant magnetic domain refining treatment method a known technique such as forming linear grooves of a predetermined depth on the surface of the steel sheet can be applied.
- Example 1 11 and Tables 5, 12 and 6, and grain-oriented electrical steel sheets, which are core materials shown in Table 7, single-phase tranco-cores and uni-cores were produced.
- strain relief annealing was performed at 800° C. for 2 hours. After annealing, the iron core was unwound from the joint and a 50-turn winding coil was inserted. Further, in conditions 42 to 47, the wound coil was inserted without performing the strain relief annealing. Then, under the conditions of excitation magnetic flux density (Bm) of 1.5 T and frequency (f) of 60 Hz, transformer iron loss was measured.
- Bm excitation magnetic flux density
- f frequency
- the Epstein test result of the core material (in the case of non-heat-resistant magnetic domain refining, the single plate magnetic measurement result) is taken as the material iron loss, and the iron loss increase rate BF in the transformer iron loss for that material iron loss is asked.
- Table 5 (in the case of tranco core), the length of the inner circumference was calculated by 2(c+d) ⁇ 8f ⁇ (1 ⁇ 90(°)/360(°)).
- the length of the outer circumference was calculated by 2(a+b)-8e ⁇ (1- ⁇ 90(°)/360(°)).
- the length of the inner circumference and the length of the outer circumference of the Unicore in Table 6 were calculated in the same manner as in Table 2.
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Abstract
Description
(1)平面部と該平面部に隣接するコーナー部を有し、前記平面部にラップ部を有し、前記コーナー部に屈曲部を有する巻鉄心とすること
(2)鉄心素材として、磁場の強さHが800A/mのときの磁束密度B8が1.91T以下である方向性電磁鋼板を用いること
(3)鉄心の外周の長さと内周の長さの比(外周の長さ/内周の長さ)が1.80以下であること
(4)磁場の強さHが800A/mのときの磁束密度B8が1.84T以上である方向性電磁鋼板を用いること
(5)下記式で求められる圧縮応力下での鉄損劣化率が1.50以下である方向性電磁鋼板を用いること
圧縮応力下での鉄損劣化率=(圧縮応力5MPaにおける鉄損)/(圧縮応力がない場合の鉄損)
ここで、上記式中の圧縮応力5MPaにおける鉄損および圧縮応力がない場合の鉄損は、それぞれ周波数50Hz、最大磁化1.7Tの条件で測定された鉄損(W/kg)であり、かつ、前記圧縮応力5MPaにおける鉄損は、鉄心素材の圧延方向への圧縮応力5MPaにおいて測定された鉄損である。
巻鉄心は、方向性電磁鋼板などの磁性体を巻き回してコアとする。一般的には、鋼板を筒状に巻き取った後、コーナー部をある曲率となるようにプレスし、矩形状に成形する方法がとられる。一方、別の製造方法として、巻鉄心のコーナー部となる部分を予め曲げ加工し、曲げ加工した鋼板を重ね合わせることにより巻鉄心とする方法がある。この方法により形成された鉄心は、コーナー部に折り曲げ部(屈曲部)を有する。前者の方法により形成された鉄心はトランココア、後者の方法により形成された鉄心は、設けられる鋼板接合部の数によりユニコアあるいはデュオコアと一般的に称する。磁束の集中を緩和するためには、後者の方法により形成されたコーナー部に折り曲げ部(屈曲部)を設ける構造が適する。
実験的に、ユニコアの鉄心内の磁束集中に及ぼす、磁束密度B8の影響を調査した結果を示す。図3に示す形状の単相のユニコアを、表1に示す磁束密度B8の異なる0.23mm厚の方向性電磁鋼板で作製した。50巻きの巻き線を施し、磁束密度1.5T、周波数60Hzの無負荷励磁を行った。図4に示す位置に、1巻きの探りコイルを配置し、鉄心内の磁束密度分布を調査した。図6に各素材(方向性電磁鋼板)で作製したユニコアにおける、内巻きから外巻きにかけて各1/4厚さの鉄心の磁束密度の最大値を示す。その結果、素材である方向性電磁鋼板の磁束密度B8が小さいほど、磁束の集中が緩和される傾向にあるが、1.91T以下ではその傾向は飽和した。
実験的に、鉄心の内側と外側の磁路長差が、磁束集中に及ぼす影響を調査した結果を示す。図7と表2に示す形状にて、鉄心の内周と外周の長さの比率を変えた鉄心を0.23mm厚の方向性電磁鋼板(磁束密度B8:1.89T、W17/50:0.86W/kg)にて作製した。50巻きの巻き線を施し、磁束密度1.5T、周波数60Hzの無負荷励磁を行った。図4に示す位置に、1巻きの探りコイルを配置し、鉄心内の磁束密度分布を調査した。外巻きから内巻きにかけて、磁束密度が大きくなっているが、最内巻き位置(位置(i))と最外巻き位置(位置(iv))とでの磁束密度の差を、内側への磁束の集中と定義する。図8に各鉄心形状における外周の長さと内周の長さの比(外周の長さ/内周の長さ)と、鉄心内側への磁束の集中の関係を示す。外周の長さと内周の長さの比率が小さいほど、鉄心の内側と外側の磁路長差が小さくなるために、鉄心内側への磁束の集中は小さくなった。特に、外周の長さと内周の長さの比が1.80以下の範囲では、鉄心内側への磁束の集中は小さかった。
なお、表2において、内周の長さは、2(c+d)+4f×(√2-2)で算出した。また、外周の長さは、2(a+b)+4e×(√2-2)で算出した。また、a、bは、それぞれa=c+2w、b=d+2wで算出した。
なお、内周の長さ、外周の長さは、表2のような各箇所の長さから算出してもよいし、内周の長さ、外周の長さをそれぞれ実測してもよい。
一般に磁性体の鉄損は、励磁磁束密度の増加に対し、飽和磁化に近づくにつれて非線形に急速に増加していく。よって、鉄心内側に磁束が集中し、局所的な磁束密度が大きくなった場合、均一な磁束密度分布の場合よりも鉄損が大きくなることは前述の通りである。飽和磁化の観点では、飽和磁化が大きい程、非線形な鉄損増加が抑制できることから、鉄損の増加は抑制できる。飽和磁化は電磁鋼板では主にSi量によって決定されるが、実用的な励磁磁束密度領域で鉄損増加に効くのは、鉄心素材の磁束密度B8である。実験的に、ユニコアの鉄損に及ぼす、鉄心素材の磁束密度B8の影響を調査した結果を示す。図3に示す形状の単相のユニコアを、表3に示す磁束密度B8の異なる0.23mm厚の方向性電磁鋼板で作製した。50巻きの巻き線を施し、磁束密度1.5T、周波数60Hzの無負荷励磁を行い、鉄損を測定した。結果を図9に示す。素材である方向性電磁鋼板の磁束密度B8が1.84T以上1.91T以下の領域で、鉄損が小さくなった。先に説明した低B8による磁束集中緩和の効果と、高B8による鉄損増加の減少の効果により、上記の範囲にて鉄損が小さくなったのだと推定される。
磁束が集中し鉄損が大きくなる鉄心の内側は、加工による歪みが残留しやすい部分である。一般に、歪みが残存すると、該部分の磁区構造が乱れ、透磁率が劣化し、鉄心全体の鉄損が劣化する。また、加工後に歪み取り焼鈍を実施した場合も、矩形折り曲げ部においては、双晶が存在し、残留歪みと同様に、該部分の磁区構造が乱れ、透磁率が劣化し、鉄心全体の鉄損が劣化する。つまり、残留歪みや双晶による鉄損増加が抑えられれば、鉄心の内側に磁束が集中した場合でも、鉄損増加が抑制できる。
[1]方向性電磁鋼板を素材として構成された巻鉄心であって、
前記巻鉄心は、平面部と該平面部に隣接するコーナー部を有し、前記平面部にラップ部を有し、前記コーナー部に屈曲部を有し、かつ、前記巻鉄心を側面視したときの外周の長さと内周の長さの比(外周の長さ/内周の長さ)が1.80以下であり、
前記方向性電磁鋼板は、磁場の強さHが800A/mのときの磁束密度B8が1.84T以上1.91T以下であり、かつ、下記式で求められる圧縮応力下での鉄損劣化率が1.50以下である、巻鉄心。
圧縮応力下での鉄損劣化率=(圧縮応力5MPaにおける鉄損)/(圧縮応力がない場合の鉄損)
ここで、上記式中の圧縮応力5MPaにおける鉄損および圧縮応力がない場合の鉄損は、それぞれ周波数50Hz、最大磁化1.7Tの条件で測定された鉄損(W/kg)であり、かつ、前記圧縮応力5MPaにおける鉄損は、前記方向性電磁鋼板の圧延方向への圧縮応力5MPaにおいて測定された鉄損である。
[2]前記方向性電磁鋼板は、耐熱型の磁区細分化処理が施されたものである、[1]に記載の巻鉄心。
[3]方向性電磁鋼板を素材として構成され、平面部と該平面部に隣接するコーナー部を有し、前記平面部にラップ部を有し、前記コーナー部に屈曲部を有する巻鉄心の製造方法であって、
前記巻鉄心を側面視したときの前記巻鉄心の外周の長さと内周の長さの比(外周の長さ/内周の長さ)を1.80以下とし、
前記方向性電磁鋼板として、磁場の強さHが800A/mのときの磁束密度B8が1.84T以上1.91T以下であり、かつ、下記式で求められる圧縮応力下での鉄損劣化率が1.50以下である方向性電磁鋼板を用いる、巻鉄心の製造方法。
圧縮応力下での鉄損劣化率=(圧縮応力5MPaにおける鉄損)/(圧縮応力がない場合の鉄損)
ここで、上記式中の圧縮応力5MPaにおける鉄損および圧縮応力がない場合の鉄損は、それぞれ周波数50Hz、最大磁化1.7Tの条件で測定された鉄損(W/kg)であり、かつ、前記圧縮応力5MPaにおける鉄損は、前記方向性電磁鋼板の圧延方向への圧縮応力5MPaにおいて測定された鉄損である。
[4]前記方向性電磁鋼板は、耐熱型の磁区細分化処理が施されたものである、[3]に記載の巻鉄心の製造方法。
本発明によれば、磁気特性の異なる2種類以上の素材を使用した場合に必要となる素材の配置等の鉄心設計の煩雑さが低減され、鉄損が小さい磁気特性に優れた巻鉄心を、製造性高く得ることができる。
上述の通り、低鉄損となる変圧器巻鉄心を達成するには、以下の条件を満たす必要がある。
(A)平面部と該平面部に隣接するコーナー部を有し、前記平面部にラップ部を有し、前記コーナー部に屈曲部を有する巻鉄心とすること
(B)鉄心の外周の長さと内周の長さの比が1.80以下であること
上述の通り、低鉄損となる変圧器巻鉄心を達成するには、以下の条件を満たす必要がある。
磁気特性の測定は、エプスタイン試験により行う。エプスタイン試験はIEC規格あるいはJIS規格等の公知の方法で実施する。あるいは、非耐熱型の磁区細分化材など、エプスタイン試験による磁束密度B8の評価が困難な場合には、単板磁気測定試験(SST)による結果を代用しても良い。巻鉄心製造に関し、上記の磁束密度B8の好適範囲による選別を行う際には、方向性電磁鋼板コイルの代表特性を用いるべきである。具体的には、鋼板コイルの先尾端にて、試験サンプルを採取し、エプスタイン試験を行い磁束密度B8を測定し、その平均値を代表特性として採用する。あるいは、鋼材メーカが提供する鋼板の特性値(平均値及び保証値)を基に、材料の選別を行っても良い。前記磁束密度B8は、好ましくは1.86T以上である。
圧縮応力下での鉄損劣化率=(圧縮応力5MPaにおける鉄損)/(圧縮応力がない場合の鉄損)
上記の式中で定義される、圧縮応力5MPaにおける鉄損、圧縮応力がない場合の鉄損は、同一の単板磁気測定装置にて周波数50Hz、最大磁化1.7Tの条件にて測定される鉄損(W/kg)であり、かつ、前記圧縮応力5MPaにおける鉄損は、鉄心素材となる方向性電磁鋼板の圧延方向への圧縮応力5MPaにおいて測定される鉄損である。圧縮応力は、鋼板の圧延方向一軸に5MPaにて圧縮側に印加される。圧縮応力の印可方法は、特に規定しないが、例えば鋼板の一方向側をクランプ等で固定し、その反対側からプッシャー等で応力を加える方法がある。その際には、鋼板が座屈しないように、圧延方向に沿って均一に応力を加える必要がある。また座屈を防止するために、鋼板を、面直方向上下に測定に支障がない範囲で固定しても良い。なお、前記圧縮応力がない場合の鉄損は、圧縮応力を印加せずに測定した鉄損である。本発明では、上述のように、鉄心素材として、前記圧縮応力下での鉄損劣化率が1.50以下である方向性電磁鋼板を用いる。前記圧縮応力下での鉄損劣化率は、1.45以下が好ましい。なお、前記圧縮応力下での鉄損劣化率の下限は特に限定されないが、一例として、前記圧縮応力下での鉄損劣化率の下限は1.05である。
本発明において、方向性電磁鋼板用スラブの成分組成は、二次再結晶が生じる成分組成であればよい。また、インヒビターを利用する場合、例えばAlN系インヒビターを利用する場合であればAlおよびNを、またMnS・MnSe系インヒビターを利用する場合であればMnとSeおよび/またはSを適量含有させればよい。勿論、両インヒビターを併用してもよい。この場合におけるAl、N、SおよびSeの好適含有量はそれぞれ、Al:0.010~0.065質量%、N:0.0050~0.0120質量%、S:0.005~0.030質量%、Se:0.005~0.030質量%である。
Cは、熱延板組織の改善のために添加をする。しかしながら、C含有量が、0.08質量%を超えると製造工程中に磁気時効の起こらない50質量ppm以下までCを低減することが困難になるため、C含有量は0.08質量%以下とすることが好ましい。なお、C含有量の下限に関しては、Cを含まない素材でも二次再結晶が可能であるので特に設ける必要はない。すなわち、C含有量は0質量%であってもよい。
Siは、鋼の電気抵抗を高め、鉄損を改善するのに有効な元素である。Si含有量が2.0質量%以上であると十分な鉄損低減効果がより得られやすくなる。一方、Si含有量が8.0質量%以下であると、著しい加工性の低下を抑制でき、また磁束密度の低下も抑制しやすくなる。そのため、Si含有量は2.0~8.0質量%の範囲とすることが好ましい。
Mnは、熱間加工性を良好にする上で必要な元素である。Mn含有量が0.005質量%以上であると、その添加効果が得られやすくなる。一方、Mn含有量が1.000質量%以下であると製品板の磁束密度の低下を抑制しやすくなる。そのため、Mn含有量は、0.005~1.000質量%の範囲とすることが好ましい。
Crは、フォルステライト被膜と地鉄との界面に、緻密な酸化被膜形成を促進する元素である。Crを添加しなくても酸化被膜形成は可能であるが、Crを0.02質量%以上添加することによって他成分の好適範囲の拡大などが期待できる。また、Cr含有量が0.20質量%以下であると、酸化被膜が厚くなりすぎるのを抑制でき、耐コーティング剥離性の劣化を抑制しやすくなる。そのため、Cr含有量は、0.02~0.20質量%の範囲とすることが好ましい。
上記成分組成を有するスラブを、常法に従い加熱する。加熱温度は、1150~1450℃が好ましい。
上記加熱後に、熱間圧延を行う。鋳造後、加熱せずに直ちに熱間圧延を行ってもよい。薄鋳片の場合には、熱間圧延を行うこととしてもよく、あるいは、熱間圧延を省略してもよい。熱間圧延を実施する場合は、粗圧延最終パスの圧延温度を900℃以上、仕上げ圧延最終パスの圧延温度を700℃以上で実施することが好ましい。
その後、必要に応じて熱延板焼鈍を施す。このとき、ゴス組織を製品板において高度に発達させるためには、熱延板焼鈍温度として800~1100℃の範囲が好適である。熱延板焼鈍温度が800℃未満であると、熱間圧延でのバンド組織が残留し、整粒した一次再結晶組織を実現することが困難になり、二次再結晶の発達が阻害されるおそれがある。一方、熱延板焼鈍温度が1100℃を超えると、熱延板焼鈍後の粒径が粗大化しすぎるために、整粒した一次再結晶組織の実現が極めて困難となるおそれがある。
その後、1回または中間焼鈍を挟む2回以上の冷間圧延を施す。中間焼鈍温度は800℃以上1150℃以下が好適である。また、中間焼鈍時間は、10~100秒程度とすることが好ましい。
その後、脱炭焼鈍を行う。脱炭焼鈍では、焼鈍温度を750~900℃とし、酸化性雰囲気PH2O/PH2を0.25~0.60とし、焼鈍時間を50~300秒程度とすることが好ましい。
その後、焼鈍分離剤を塗布する。焼鈍分離剤は、主成分をMgOとし、塗布量を8~15g/m2程度とすることが好適である。
その後、二次再結晶およびフォルステライト被膜の形成を目的として仕上げ焼鈍を施す。焼鈍温度は1100℃以上とし、焼鈍時間は30分以上とすることが好ましい。
その後、平坦化処理(平坦化焼鈍)および絶縁コーティングを施す。なお、絶縁コーティングを施す際の絶縁コーティングの塗布・焼き付け処理にて平坦化処理も同時に行い、形状を矯正することも可能である。平坦化焼鈍は、焼鈍温度を750~950℃とし、焼鈍時間10~200秒程度で実施するのが好適である。本発明では、平坦化焼鈍前または後に、鋼板表面に絶縁コーティングを施すことができる。ここでの絶縁コーティングとは、鉄損低減のために、鋼板に張力を付与するコーティング(張力コーティング)を意味する。張力コーティングとしては、シリカを含有する無機系コーティングや、物理蒸着法、化学蒸着法等によるセラミックコーティング等が挙げられる。
鋼板の鉄損を低減させるために、磁区細分化処理を施すことは好適である。磁区細分化技術とは、鋼板の表面に対して物理的な手法で不均一性を導入することにより、磁区の幅を細分化して鉄損を低減する技術である。磁区細分化技術は大きく分けて、歪み取り焼鈍において効果が損じない耐熱型の磁区細分化と、歪み取り焼鈍により効果が減じる非耐熱型の磁区細分化に分けられる。本発明においては、磁区細分化処理がされていない鋼板、耐熱型の磁区細分化処理が施された鋼板、非耐熱型の磁区細分化処理が施された鋼板いずれにも適用することができる。
図11および表5、図12および表6に示す鉄心形状と、表7に示す鉄心素材である方向性電磁鋼板にて、単相のトランココア及びユニコアを作製した。条件1~41には、成型後、800℃で2時間の歪み取り焼鈍を行い、焼鈍後、接合部より鉄心を巻きほぐし、50Turn(50巻き)の巻き線コイルを挿入した。また、条件42~47には、前記歪み取り焼鈍を行わずに、前記巻き線コイルを挿入した。そして、励磁磁束密度(Bm)1.5T、周波数(f)60Hzの条件で、変圧器鉄損を測定した。同条件での、鉄心素材のエプスタイン試験結果(非耐熱型の磁区細分化の場合は単板磁気測定結果)を素材鉄損とし、その素材鉄損に対する変圧器鉄損における鉄損増加率BFを求めた。なお、表5(トランココアの場合)において、内周の長さは、2(c+d)-8f×(1-π×90(°)/360(°))で算出した。また、外周の長さは、2(a+b)-8e×(1-π×90(°)/360(°))で算出した。また、a、bは、それぞれa=c+2w、b=d+2wで算出した。表6のユニコアの内周の長さ、外周の長さは、表2と同様に算出した。
Claims (4)
- 方向性電磁鋼板を素材として構成された巻鉄心であって、
前記巻鉄心は、
平面部と該平面部に隣接するコーナー部を有し、前記平面部にラップ部を有し、前記コーナー部に屈曲部を有し、かつ、前記巻鉄心を側面視したときの外周の長さと内周の長さの比(外周の長さ/内周の長さ)が1.80以下であり、
前記方向性電磁鋼板は、
磁場の強さHが800A/mのときの磁束密度B8が1.84T以上1.91T以下であり、かつ、下記式で求められる圧縮応力下での鉄損劣化率が1.50以下である、巻鉄心。
圧縮応力下での鉄損劣化率=(圧縮応力5MPaにおける鉄損)/(圧縮応力がない場合の鉄損)
ここで、上記式中の圧縮応力5MPaにおける鉄損および圧縮応力がない場合の鉄損は、それぞれ周波数50Hz、最大磁化1.7Tの条件で測定された鉄損(W/kg)であり、かつ、前記圧縮応力5MPaにおける鉄損は、前記方向性電磁鋼板の圧延方向への圧縮応力5MPaにおいて測定された鉄損である。 - 前記方向性電磁鋼板は、耐熱型の磁区細分化処理が施されたものである、請求項1に記載の巻鉄心。
- 方向性電磁鋼板を素材として構成され、平面部と該平面部に隣接するコーナー部を有し、前記平面部にラップ部を有し、前記コーナー部に屈曲部を有する巻鉄心の製造方法であって、
前記巻鉄心を側面視したときの前記巻鉄心の外周の長さと内周の長さの比(外周の長さ/内周の長さ)を1.80以下とし、
前記方向性電磁鋼板として、磁場の強さHが800A/mのときの磁束密度B8が1.84T以上1.91T以下であり、かつ、下記式で求められる圧縮応力下での鉄損劣化率が1.50以下である方向性電磁鋼板を用いる、巻鉄心の製造方法。
圧縮応力下での鉄損劣化率=(圧縮応力5MPaにおける鉄損)/(圧縮応力がない場合の鉄損)
ここで、上記式中の圧縮応力5MPaにおける鉄損および圧縮応力がない場合の鉄損は、それぞれ周波数50Hz、最大磁化1.7Tの条件で測定された鉄損(W/kg)であり、かつ、前記圧縮応力5MPaにおける鉄損は、前記方向性電磁鋼板の圧延方向への圧縮応力5MPaにおいて測定された鉄損である。 - 前記方向性電磁鋼板は、耐熱型の磁区細分化処理が施されたものである、請求項3に記載の巻鉄心の製造方法。
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