WO2022050053A1 - 方向性電磁鋼板 - Google Patents
方向性電磁鋼板 Download PDFInfo
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- WO2022050053A1 WO2022050053A1 PCT/JP2021/030260 JP2021030260W WO2022050053A1 WO 2022050053 A1 WO2022050053 A1 WO 2022050053A1 JP 2021030260 W JP2021030260 W JP 2021030260W WO 2022050053 A1 WO2022050053 A1 WO 2022050053A1
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- Prior art keywords
- magnetic domain
- steel sheet
- grain
- reflux
- iron loss
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- 229910000831 Steel Inorganic materials 0.000 title abstract description 66
- 239000010959 steel Substances 0.000 title abstract description 66
- 230000005381 magnetic domain Effects 0.000 claims abstract description 214
- 238000010992 reflux Methods 0.000 claims description 89
- 238000005096 rolling process Methods 0.000 claims description 37
- 229910001224 Grain-oriented electrical steel Inorganic materials 0.000 claims description 34
- 238000012545 processing Methods 0.000 claims description 9
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- 238000013467 fragmentation Methods 0.000 abstract 1
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 184
- 229910052742 iron Inorganic materials 0.000 description 84
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- 229910000976 Electrical steel Inorganic materials 0.000 description 6
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- 229910052839 forsterite Inorganic materials 0.000 description 5
- 239000010410 layer Substances 0.000 description 5
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
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- 229910019142 PO4 Inorganic materials 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
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- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
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- 239000007864 aqueous solution Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
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- GVALZJMUIHGIMD-UHFFFAOYSA-H magnesium phosphate Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O GVALZJMUIHGIMD-UHFFFAOYSA-H 0.000 description 1
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Images
Classifications
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- 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
- 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
- C21D10/00—Modifying the physical properties by methods other than heat treatment or deformation
- C21D10/005—Modifying the physical properties by methods other than heat treatment or deformation by laser shock processing
-
- 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
- C21D8/1277—Modifying the physical properties 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 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
- C21D8/1277—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a particular surface treatment
- C21D8/1288—Application of a tension-inducing coating
-
- 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
- C21D8/1294—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a localized treatment
-
- 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
- H01F1/18—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 with insulating coating
-
- 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
- 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
- C21D2221/00—Treating localised areas of an article
Definitions
- the present invention relates to a grain-oriented electrical steel sheet capable of simultaneously improving transformer loss and noise.
- Electrical steel sheets are mainly used for iron cores such as transformers, and their magnetic characteristics are required to be excellent, especially low iron loss.
- Methods for improving the magnetic properties of grain-oriented electrical steel sheets include improving the orientation (sharpening) of the crystal grains constituting the steel sheet in the Goss direction, increasing the tension applied to the steel sheet by the tension coating, and further to the steel sheet. Subdivision of magnetic domains by forming strains and grooves has been proposed.
- Patent Document 1 describes that the iron loss of a grain-oriented electrical steel sheet is reduced by optimizing the output and irradiation time of the electron beam.
- the iron loss is not always low. This is because the exciting magnetic flux when evaluating the iron loss of the directional electromagnetic steel plate itself is only the rolling direction component, whereas the exciting magnetic flux when the steel plate is actually used as the iron core of the transformer is the rolling direction component. This is because it has not only a rolling perpendicular component but also a rolling perpendicular component.
- the building is defined as the ratio of the transformer iron loss to the iron loss of the material steel plate.
- Factor (BF) is commonly used. When this BF is more than 1, it means that the iron loss of the transformer is larger than the iron loss of the material steel plate.
- the grain-oriented electrical steel sheet is a material having the lowest iron loss when magnetized in the rolling direction. Therefore, when it is incorporated in a transformer that is magnetized in a direction other than the rolling direction, its iron loss increases. And as a result, BF becomes larger than 1. That is, in order to improve the energy efficiency of the transformer, it is not enough that the iron loss of the material steel plate is low, but the BF is made as close to 1 as possible, that is, the iron loss value of the transformer is set to the iron loss of the material steel plate. It is important to get close to the value.
- Patent Document 2 discloses a technique for obtaining a good transformer iron loss by optimizing the dot spacing of electron beams irradiated in a dot sequence.
- Patent Document 3 a technique for reducing iron loss by focusing on the reflux magnetic domain generated during magnetic domain subdivision using laser irradiation and optimizing its shape and dimensions has also been proposed.
- transformers which are equipment that uses grain-oriented electrical steel sheets
- reduction of transformer iron loss and noise reduction are the main development issues related to iron core materials.
- Directional as an iron core material It goes without saying that if the iron loss of electrical steel sheets is reduced, the iron loss of transformers will be reduced, but in three-phase tripod (five-leg) transformers that are often used in general. It is known that the transformer loss increases more than the material steel loss, that is, the above-mentioned BF becomes larger than 1.
- the transformer is required to have low noise depending on its usage environment.
- transformer noise There are two types of transformer noise: no-load noise emitted from the iron core when there is no load, and load noise which consists of the sum of the noise of the iron core and the noise from the coil when there is no load.
- the iron core noise which is a cause of transformer noise, is strongly influenced by the iron core material, and it is said that the magnetic strain vibration of the iron core material is the main cause of the iron core noise. Therefore, it is desired that the grain-oriented electrical steel sheet has low iron loss, low BF, and low magnetostriction as a material for such a transformer.
- the non-heat-resistant magnetic domain subdivision method for grain-oriented electrical steel sheets which is often used as a manufacturing method to obtain a high iron loss reduction effect, introduces local linear strain into the steel sheet by some method as described above.
- This is a method of generating a linear recirculated magnetic domain region and reducing the 180 ° magnetic domain width by the effect of the magnetic poles generated in this region (hereinafter, also referred to as non-heat resistant magnetic domain subdivision processing).
- the conventional technology has not been able to cope with all of the reduction of iron loss of the material, the reduction of BF, and the prevention of deterioration of noise characteristics.
- Patent Document 1 discloses not only a technique for reducing iron loss of a steel sheet itself as described above, but also a technique for preventing deterioration of BF while improving noise characteristics.
- the BF deterioration prevention measure in this technique is through suppressing the warp of the plate by irradiating the electron beam. That is, such a technique is a measure for preventing deterioration in an extreme situation where the steel sheet is warped due to the magnetic domain subdivision treatment and the iron core iron loss is deteriorated. It is not a measure to improve the situation.
- Patent Document 2 is intended to improve the transformer BF in the grain-oriented electrical steel sheet which has been subjected to the non-heat resistant magnetic domain subdivision treatment. That is, in this technique, a point-series strain region is introduced, and by optimizing the size and spacing, iron loss in the direction perpendicular to rolling is reduced, which leads to improvement of BF. However, since this technique focuses only on the reflux magnetic domain generated by thermal strain, it cannot be said that the effect of improving BF is sufficient. Moreover, improvement of noise characteristics has not been pursued.
- Patent Document 3 The technique described in Patent Document 3 is intended to improve noise characteristics in a magnetic domain subdivided material by laser irradiation, but since it is based on a conventional laser irradiation method, the conditions for forming a reflux magnetic domain are not sufficient and transformation. The viewpoint of reducing the BF of the vessel is not considered.
- Patent Document 4 is intended to improve noise characteristics in magnetic domain controlled electrical steel sheets, but mainly only controls the volume fraction of the reflux magnetic domain, and is a transformer. Has not been shown to have any effect on BF. As a result, the improvement effect that combines iron loss and noise is not sufficient.
- Patent Document 5 defines the length of the reflux magnetic domain in the plate thickness direction and the rolling direction for the purpose of improving BF, but does not consider the noise of the transformer.
- Patent Document 6 is a technique for appropriately controlling the width, depth, and spacing of the reflux magnetic domains for the purpose of maximizing the effect of reducing iron loss by the magnetic domain subdivision treatment according to the plate thickness of the material. Is disclosed, but noise and BF are not considered.
- the present inventors have appropriately controlled the volume ratio of the recirculated magnetic domain and the area ratio of the steel sheet surface to appropriately control the grain-oriented electrical steel sheet which is the material of the transformer. It was found that a sufficiently low iron loss value can be obtained as iron loss, and when such a steel plate is used, the BF is also sufficiently low, so that the transformer iron loss is excellent and low noise characteristics can be realized. Obtained. The present inventors have completed the present invention based on such findings.
- the gist structure of the present invention is as follows.
- inventions excluding the invention described in the following paragraph 2 and the invention described in the following paragraph 3 from the invention described in the following paragraph 1 in the present specification are described in the invention 1 and the following paragraph 2.
- the invention described in paragraph 3 below is referred to as invention 2, and the invention described in paragraph 3 below is referred to as invention 3.
- 1. A grain-oriented electrical steel sheet having a tension film on its surface and subjected to magnetic domain subdivision processing by generating linear recirculation magnetic domains extending in the direction perpendicular to rolling and within 30 °.
- the plate thickness is T [mm]
- the depth of the recirculated magnetic domain based on the surface subjected to the magnetic domain subdivision treatment is d [mm]
- the average spacing of adjacent magnetic domains on the surface is L [mm. ]
- S R cross-sectional area of the recirculation magnetic domain in the cross section orthogonal to the linear strain region
- the width of the recirculation magnetic domain is w [mm].
- the average spacing L is 15 mm or less.
- the depth ratio r d of the reflux magnetic domain to the plate thickness calculated by (d / T) ⁇ 100 is 35% or more.
- the volume fraction r v of the reflux magnetic domain calculated by ⁇ S R / (LT) ⁇ ⁇ 100 is 0.30% or more and 3.0% or less.
- the depth ratio r d is 39% or more, and the volume fraction r v [%] and the area ratio r s [%] are expressed by the following equation (1):. r s ⁇ 2.6r v ⁇ ⁇ ⁇ (1) The grain-oriented electrical steel sheet according to 1 above, which satisfies the above relationship.
- the volume fraction r v is 0.75% or more, and the volume fraction r v [%] and the area fraction r s [%] are expressed by the following equation (2): r s ⁇ 1.2 r v +0.9 ⁇ ⁇ ⁇ (2) 2.
- a linear strain for generating a linear reflux magnetic domain is formed by arranging a plurality of strain introduction portions in a dotted line, and the diameter of the strain introduction portion is D [mm], and adjacent strains are adjacent to each other.
- D the diameter of the strain introduction portion
- adjacent strains are adjacent to each other.
- the present invention not only the improvement of the transformer iron loss by improving the magnetic properties of the grain-oriented electrical steel sheet but also the BF of the three-phase transformer is improved, which contributes to the production of a transformer having a lower iron loss and is non-heat resistant. It is possible to prevent deterioration of transformer noise, which tends to be disadvantageous, by using grain-oriented electrical steel sheets that have been subjected to magnetic domain subdivision processing. Further, according to the present invention, as a grain-oriented electrical steel sheet subjected to a non-heat-resistant magnetic domain subdivision treatment, it is possible to obtain a material having an excellent balance between iron loss and noise of a transformer.
- the surface of a directional electromagnetic steel plate provided with a tension coating is continuously or intermittently irradiated with a high energy beam in the direction perpendicular to rolling and within 30 ° to form a plurality of continuous lines or dots. Form distortion.
- the type of grain-oriented electrical steel sheet used as a base material is not particularly limited, and various known grain-oriented electrical steel sheets can be used.
- the grain-oriented electrical steel sheet used in the present invention has a tension coating on its surface.
- the type of the tension coating is not particularly limited, and for example, two layers consisting of a forsterite coating containing Mg 2SiO 4 as a main component formed in the final finish annealing and a phosphate-based tension coating formed on the forsterite coating.
- the coating can be used as a tension coating. Further, it is also possible to directly form a phosphate-based tension-applying insulating film on the surface of a steel sheet that does not have a forsterite film.
- the phosphate-based tension-applying insulating film can be formed, for example, by applying an aqueous solution containing metal phosphate and silica as main components to the surface of a steel plate and baking it.
- an aqueous solution containing metal phosphate and silica as main components to the surface of a steel plate and baking it.
- the tension film is not damaged by beam irradiation, it is not necessary to recoat for repair after beam irradiation, but if film damage occurs, the temperature is as low as 300 ° C or less. It is preferable to recoat with a coating that has both formable insulation and anticorrosion.
- the directional electromagnetic steel plate of the present invention is formed with a plurality of continuous linear or dotted strains (hereinafter, collectively referred to as "linear strains") extending linearly in a direction intersecting the rolling direction. Will be done. This strain has the effect of subdividing the magnetic domain and reducing iron loss.
- the plurality of linear strains are parallel to each other and are provided at predetermined intervals, which will be described later.
- a reflux magnetic domain is generated by the strain, and the strain and the reflux magnetic domain have the same magnitude at the same site under predetermined conditions, and the reflux magnetic domain is specified by a means described later.
- the direction of linear strain should be the direction perpendicular to rolling, or the inclination from the direction perpendicular to rolling should be within a predetermined range. Has been done. Also in the present invention, the direction of the linear strain region is within 30 ° from the direction perpendicular to rolling.
- the plurality of linear strains can be formed by irradiating the surface of a steel sheet having a tension film with a focused high-energy beam.
- the type of high-energy beam is not particularly limited, but among them, the electron beam is characterized by the effect of suppressing film damage due to the high acceleration voltage and the ability to control the beam at high speed. Therefore, it is preferable to use an electron beam in the present invention.
- Irradiation of the high energy beam is performed while scanning the beam from the width end of the steel sheet to the other width end using one or more irradiation devices (for example, an electron gun).
- the scanning direction of the beam shall be a direction orthogonal to the rolling direction (rolling perpendicular direction), or a direction in which the angle with the rolling perpendicular direction is within 30 °.
- the reflux magnetic domain generated linearly is the average value of the distance between the adjacent magnetic domain and the center (the distance between the centers in the direction orthogonal to the direction in which the adjacent reflux magnetic domain extends), that is, the average distance L (FIG. 1). (See) is 15 mm or less. If this average spacing L exceeds 15 mm, a sufficient magnetic domain subdivision effect cannot be obtained, and the iron loss of the steel sheet after magnetic domain subdivision increases. On the other hand, the average spacing L is preferably 3 mm or more.
- the processing time can be shortened and the production efficiency can be improved, the strain region formed in the steel becomes excessively large, and the hysteresis loss and the magnetostriction increase. Can be prevented.
- the interval between the reflux magnetic domains is the interval between the center widths of the reflux magnetic domains observed on the surface of the steel sheet.
- the average interval L is an average interval for 10 or more linear recirculation magnetic domains. For example, if 10 magnetic domains are taken into consideration and the total interval is L 10 , the average interval L is calculated as L 10/9 .
- the upper limit of the depth ratio r d is not particularly limited and may be 100%.
- the volume fraction r v should be 0.75% or more.
- the volume fraction r v of the reflux magnetic domain can be obtained by observing the magnetic domain in a cross section orthogonal to the linear strain region. That is, as shown in FIG. 1, the cross-sectional area of the recirculated magnetic domain in the cross section orthogonal to the linear strain region determined by magnetic domain observation is S R [mm 2 ], the plate thickness is T [mm], and the plate thickness is T [mm]. Using the above-mentioned average spacing L [mm] of the recirculated magnetic domains, the volume ratio r v of the recirculated magnetic domains can be calculated by ⁇ SR / (LT) ⁇ ⁇ 100.
- a sample is prepared with a cross section orthogonal to the linear strain region as an observation surface, buffed for a long time until the influence of processing is not recognized, and then Kerr. It can be obtained from the image by observing the magnetic domain by the effect. From the image thus obtained, the reflux magnetic domain portion can be determined by the difference in pattern from the surrounding non-processed portion, and the area thereof can be obtained as the cross-sectional area S R.
- the method of observing the magnetic domain is not particularly limited, but a method using the Kerr effect is suitable.
- the vicinity of the surface (1/4 of the plate thickness) is referred to as the surface layer portion of the steel plate, and the direction toward the center of the plate thickness (1/2 of the remaining plate thickness) from the surface layer portion is referred to as the inner layer portion of the steel plate. ..
- the depth ratio r d of the reflux magnetic domain to the plate thickness is set to a certain value or more, and further, the BF which is a factor of increasing the iron loss of the transformer is reduced.
- the BF of the transformer can be further reduced.
- the present invention it is possible to suppress the increase in noise of the transformer under the condition that the depth and volume of the recirculation magnetic domain are sufficiently increased in order to reduce the iron loss of the transformer.
- the reason for this is considered as follows. Since the recirculated magnetic domain tends to generate a magnetization component in the direction perpendicular to the rolling of the steel sheet, the BF is primarily improved as the volume of the recirculated magnetic domain increases. This is because the generation of the magnetization component in the direction perpendicular to the rolling direction is the largest at the T-joint or L-junction of the three-phase product core transformer, and the magnetization behavior at these parts strongly affects the BF. It is considered.
- the rotational magnetic flux of the T-joint or the L-joint is carried by the magnetization component in the rolling direction due to the movement of the 180 ° domain wall and the magnetization component in the rolling perpendicular direction due to the change in the magnetic domain structure.
- the progress of magnetization in the direction perpendicular to rolling becomes easy, and BF is excellent. Therefore, primarily, the larger the volume of the reflux magnetic domain, the more the BF tends to improve.
- the iron loss of the steel sheet will increase because the change and the change in magnetization in the direction perpendicular to the rolling inside the recirculation magnetic domain interfere with each other.
- the 180 ° magnetic domain structure portion starting from the reflux magnetic domain. It is presumed that changes in the magnetic domain structure of the magnetic domain are unlikely to occur.
- the area ratio r s of the recirculated magnetic domain is set to a certain value or less with respect to the volume ratio r v of the recirculated magnetic domain and the distribution of the recirculated magnetic domain in the plate thickness direction is made more uniform, the recirculated magnetic domain in the surface layer portion and the inner layer portion of the steel plate. Since the difference in the volume ratio r v of the above is reduced, it is considered that the iron loss in the portion where the rotational magnetic flux is generated is improved and the transformer loss (BF) is improved.
- the rotational magnetic flux refers to a state in which the locus of the vector tip is two-dimensional with respect to the origin of the magnetization vector when the time change of the magnetization vector is followed, and the shape is a circle, an ellipse, a rhombus, or a shape close to these. means.
- the width w is obtained by measuring the widths of five or more places by changing the places in the plate surface of the steel plate and as the average value.
- a magnetic domain observation using magnetic powder a magnetic domain observation using magnetic powder, a magnetic domain observation by the Faraday effect, and a method using a high voltage SEM are suitable.
- the width of the reflux magnetic domain may be determined by observing the magnetic domain by the Kerr effect after removing the insulating tension film on the plate surface to make it a mirror surface.
- the width w (mean value) of the reflux magnetic domain is obtained by measuring the width wi of 10 or more points at arbitrary different positions at intervals of 0.2 to 5 mm for one linear magnetic domain region.
- the average value ⁇ wi> can be obtained, and such measurement can be performed on 10 or more linear perfusion magnetic domain regions and calculated as the average value thereof.
- the average spacing L of the reflux magnetic domains is calculated by measuring the spacing L N of N linear perfusion magnetic domains (N ⁇ 10) and using L N / (N-1).
- the depth d of the reflux magnetic domain refers to the distance between the deepest point and the surface of the steel sheet in the reflux magnetic domain, as observed at any place in the steel sheet as shown in FIG. Further, for the cross-sectional area S R , the area of the reflux magnetic domain portion having a different magnetic domain pattern from the surrounding non-processed portion may be obtained by image processing.
- the depth d and the cross-sectional area S R of the reflux magnetic domain are obtained by measuring the depths and cross-sectional areas of five or more places in the steel plate at different places from the viewpoint of ensuring the measurement accuracy, and calculating each as the average value.
- the magnetostriction can be used to derive the volume fraction r v and the depth ratio r d of the reflux magnetic domain. Since the volume of the recirculated magnetic domain and the magnetostriction ⁇ 0-P are closely related, it is possible to derive the volume ratio r v by the magnetostriction ⁇ 0-P .
- the depth of the reflux magnetic domain can be obtained from the volume ratio r v and the width w of the reflux magnetic domain assuming that the cross-sectional shape of the reflux magnetic domain is rectangular, but in reality, it is shown in the schematic diagram shown in FIG. As you can see, there is a deviation from the rectangle.
- the cross-sectional shape is rectangular, the cross-sectional area S R of the reflux magnetic domain is wd, but according to the research by the present inventors, the actual cross-sectional area S R is about 80% of wd. ..
- the depth ratio r d of the reflux magnetic domain to the plate thickness can be obtained by the following equation (f).
- the derivation of the volume fraction r v and the depth ratio r d as described above is A ⁇ 1.2 D, and can be applied when it is difficult to determine the volume of the reflux magnetic domain by magnetic domain observation.
- the non-heat-resistant magnetic domain subdivision treatment in the present invention is a single or combination of methods capable of locally introducing linear strain into a steel plate, such as an electron beam, a laser beam, a plasma flame, and mechanical contact of terminals. Although it can be used, in order to achieve the requirements of the present invention, a method using an electron beam capable of generating a recirculation magnetic domain deep into a steel plate is particularly suitable.
- the conditions for performing the magnetic domain subdivision process by electron beam irradiation will be described in more detail.
- it is preferable to increase the beam current but in this case, the width of the recirculation magnetic domain on the surface layer portion of the steel sheet becomes large, and the condition of the present invention cannot be satisfied. Therefore, in the magnetic domain subdivision-oriented electrical steel sheet of the present invention, it is necessary to allow a thin electron beam to reach deep into the plate thickness, and it is preferable to appropriately combine the existing manufacturing methods described below.
- the acceleration voltage is high. This is because the higher the acceleration voltage, the higher the material permeability of the electron beam. By increasing the acceleration voltage sufficiently, the electron beam can easily pass through the tension film, but when the acceleration voltage is high, the heat generation center in the ground iron becomes a position farther (deeper) from the plate thickness surface. , The depth of the reflux magnetic domain in the plate thickness direction can be increased. Further, when the acceleration voltage is high, there is an advantage that the beam diameter can be easily reduced. In order to obtain such an effect, the acceleration voltage is preferably 80 kV or more, and more preferably 100 kV or more.
- the acceleration voltage exceeds 400 kV
- the electron beam reaches the opposite side of the irradiation of the steel sheet and the effect is saturated. Therefore, the advantage of exceeding 400 kV is small, and it is preferable to set it to 400 kV or less.
- the beam diameter in the direction orthogonal to the scanning direction of the beam, the more advantageous it is to improve the material iron loss.
- it is effective to reduce the electron beam diameter according to the acceleration voltage. be.
- the acceleration voltage is Va [kV]
- the beam diameter should be 80 kV ⁇ Va ⁇ 200 kV and the beam diameter [ ⁇ m] ⁇ -0.85 Va +270, and when Va> 200 kV, the beam diameter should be 100 ⁇ m or less.
- the reason for limiting these beam diameters is that deep reflux magnetic domains are generated as the acceleration voltage increases, and it is necessary to narrow the beam diameter in order to keep the volume of the reflux magnetic domains within the range specified in the present invention. ..
- the acceleration voltage exceeds 200 kV
- the formation depth of the reflux magnetic domain is almost equal to or more than the plate thickness, so that the effect of narrowing the beam diameter is saturated. Therefore, it is sufficient to set the beam diameter to 100 ⁇ m or less.
- the beam diameter in the present invention is defined as the half-value width of the beam profile measured by the slit method (using a slit having a width of 0.03 mm), and when the steel plate surface has an elliptical beam shape, the scanning direction is used.
- the length in the orthogonal direction is defined as the beam diameter.
- the lower limit of the beam diameter in the direction orthogonal to the scanning direction is not particularly limited, but is preferably 8 ⁇ m or more. If the beam diameter in the direction orthogonal to the scanning direction is less than 8 ⁇ m, the working distance needs to be extremely small, and the area that can be deflected and irradiated by one electron beam source is significantly reduced.
- the beam diameter in the direction orthogonal to the scanning direction is 8 ⁇ m or more, it is possible to irradiate a wide range with one electron beam source.
- the beam diameter in the direction orthogonal to the scanning direction is more preferably 30 ⁇ m or more.
- the beam current is preferably small from the viewpoint of reducing the beam diameter. If the beam current is too large, it becomes difficult to converge the beam due to the Coulomb repulsive force between the electrons. Therefore, in the present invention, it is preferable that the beam current is 30 mA or less. The beam current is more preferably 20 mA or less. On the other hand, if the beam current is too small, the strain required to obtain a sufficient magnetic domain subdivision effect cannot be formed. Therefore, in the present invention, it is preferable that the beam current is 0.5 mA or more. The beam current is more preferably 1 mA or more, and further preferably 2 mA or more.
- Example 1 The hot-rolled plate, which is the base material of the directional electromagnetic steel plate, is annealed by hot-rolled plate, then annealed to the final plate thickness (0.23 mm or 0.18 mm) by cold rolling, and then annealed and separated with MgO as the main component. After the agent was applied, final finish annealing was performed to prepare a directional electromagnetic steel plate having a forsterite coating. Next, an insulating tension film containing colloidal silica and magnesium phosphate was formed on the surface of the forsterite film. After that, the surface of the steel sheet was irradiated with an electron beam to form a plurality of linear strain regions extending in a direction intersecting the rolling direction.
- the average scanning speed of the electron beam was 100 m / s.
- the angle (line angle) of the linear strain with respect to the rolling direction was set to 90 °.
- Other processing conditions are as shown in Table 1.
- the magnetic properties of the steel sheet thus obtained were evaluated by a single plate magnetic test method under magnetic flux sinusoidal conditions with a maximum magnetic flux density of 1.7 T and a frequency of 50 Hz.
- the iron core of the three-phase tripod transformer for testing (outer dimensions 500 mm x 500 mm, width of legs and joints 100 mm (rectangular cross section), stacking thickness 50 mm, joining method: step wrap type (wrap length 3 mm)) ) was prepared and the transformer iron loss was measured.
- the transformer iron loss here is the unloaded iron loss of the transformer, the maximum magnetic flux density of the iron core leg is 1.7T, the loss of frequency 50Hz is measured, and the value is divided by the mass of the iron core (unit: W / kg). did.
- the value obtained by dividing the transformer iron loss obtained in the above process by the material iron loss measured on a single plate was defined as BF.
- the width w of the recirculated magnetic domain was obtained by observing the magnetic domain using magnetic powder on the surface of the steel sheet, and it is shown in Table 1.
- the area ratio r s of the recirculated magnetic domain was calculated by Eq. (A) using L of.
- L is obtained by measuring the interval L N of N linear perfusion magnetic domains (N ⁇ 10) and using L N / (N-1).
- the magnetic domain was observed by the Kerr effect, the formation state of the recirculated magnetic domain in the plate thickness direction was investigated, the depth d of the recirculated magnetic domain, the cross-sectional area S R. Asked.
- the depths and cross-sectional areas of 10 points are measured at different locations in the steel sheet, and d and S R are obtained as the average values of each, and the depth ratio r d is calculated by equations (b) and (c). , Volume fraction r v were calculated respectively.
- FIG. 2 shows the relationship between the depth ratio r d of the recirculation magnetic domain and the transformer iron loss for an electromagnetic steel sheet having a plate thickness of 0.23 mm.
- the material loss tends to be improved, which tends to improve the transformer iron loss, but the present invention is particularly applicable. Under these conditions, it can be seen that the transformer iron loss is improved more than the effect considered from the depth of the reflux magnetic domain. It is also shown that the effect of improving the transformer iron loss is greater in the order of the condition conforming to the invention 3, the condition conforming to the invention 2, and the condition conforming to the invention 1.
- FIG. 3 shows the relationship between the volume fraction r v and the BF of the reflux magnetic domain.
- the BF tends to decrease as the volume fraction r v of the reflux magnetic domain increases, but under the conditions of the present invention, the volume fraction of the reflux magnetic domain tends to decrease. It can be seen that the BF is improved more than the effect of r v , and the effect is higher in the order of the condition conforming to the invention 3, the condition conforming to the invention 2, and the condition conforming to the invention 1.
- FIG. 4 shows the balance between transformer iron loss and transformer noise.
- the transformer iron loss and the transformer noise are in a contradictory relationship, but as shown in FIG. 4, a material having an excellent balance between the transformer iron loss and the transformer noise can be obtained under the conditions conforming to the present invention. The effect is higher in the order of the condition conforming to the invention 3, the condition conforming to the invention 2, and the condition conforming to the invention 1.
- Example 2 In the same manner as in Example 1, a directional electromagnetic steel sheet having a thickness of 0.23 mm is subjected to magnetic domain subdivision treatment using an electron beam, and strained portions connected in a dotted line are introduced into the steel sheet to introduce a non-heat resistant magnetic domain. Subdivision was performed. At this time, the substantially circular electron beam diameter D and the distance A between the centers of the adjacent strain introduction portions were set as the conditions shown in Table 2. Using the obtained grain-oriented electrical steel sheet, the same transformer evaluation as in Example 1 was performed, and the transformer iron loss and noise were evaluated. The results are shown in Table 2.
- FIG. 5 shows the change in transformer iron loss with respect to the change in A / D for Nos. 1 to 9 in Table 2.
- Table 2 shows the results of FIG. 5 and Table 2, by further satisfying the relationship of 1.2D ⁇ A ⁇ 3D (that is, 1.2 ⁇ A / D ⁇ 3) with respect to the conditions of the inventions 1, 2 and 3. Since the iron loss of the electrical steel sheet is further improved and the BF and the transformer noise are not deteriorated, the transformer has achieved even better performance.
- the present invention makes it possible to obtain a non-heat resistant magnetic domain subdivided material having excellent transformer characteristics (iron loss, noise).
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Abstract
Description
例えば、特許文献1には、電子ビームの、出力や照射時間を適正化することによって、方向性電磁鋼板の鉄損を低減することが記載されている。
これは、方向性電磁鋼板自体の鉄損を評価する際の励磁磁束は圧延方向成分のみであるのに対して、鋼板を変圧器の鉄心として実際に使用する際の励磁磁束は、圧延方向成分だけでなく圧延直角方向成分も有しているためである。
すなわち、変圧器のエネルギ効率を向上させるためには、素材鋼板の鉄損が低いだけでは足りずに、このBFを可能な限り1に近づける、すなわち変圧器の鉄損値を素材鋼板の鉄損値に近づけることが肝要になる。
したがって、方向性電磁鋼板素材そのものの鉄損低減のみを追求するのは、最終製品である変圧器特性に改善のためには適当ではなく、素材鉄損とともに変圧器におけるBFの低減に寄与する材料を追求することが求められる。
このため、方向性電磁鋼板には、かかる変圧器の素材として、低鉄損、低BFと同時に低磁歪であることが望まれている。
したがって、非耐熱型磁区細分化処理を施した方向性電磁鋼板においては、かかる点からも、騒音特性の劣化を極力防止することが重要となる。
すなわち、かかる技術は、磁区細分化処理によって鋼板が反って鉄心鉄損の劣化するような極端な状況での劣化を防止するための方策であり、板の反りが顕著でない状況において、BFを積極的に改善するための方策とはなっていない。
しかしながら、この技術は熱歪によって生成する還流磁区のみに着眼しているため、BFの改善効果としては十分とは言えない。また、騒音特性の改善は追求されていない。
本発明者らは、かかる知見に基づき本発明を完成させた。
1.表面に張力被膜を備え、圧延直角方向と30°以内の方向に延びた線状の還流磁区を生成させることによる磁区細分化処理を施した方向性電磁鋼板であって、
板厚をT[mm]とし、前記磁区細分化処理を施した面を基準にした前記還流磁区の深さをd[mm]とし、前記面での隣接する還流磁区の平均間隔をL[mm]とし、直線状の歪領域と直交する断面における前記還流磁区の断面積をSR[mm2]とし、前記還流磁区の幅をw[mm]とするとき、
前記平均間隔Lが、15mm以下であり、
(d/T)×100で算出される板厚に対する前記還流磁区の深さ比率rdが、35%以上であり、
{SR/(LT)}×100で算出される前記還流磁区の体積率rvが、0.30%以上、3.0%以下であり、
(w/L)×100で算出される前記還流磁区の面積率rsが、0.50%以上、4.0%以下である、方向性電磁鋼板。
rs≦2.6rv・・・(1)
の関係を満たす前記1に記載の方向性電磁鋼板。
rs≦1.2rv+0.9・・・(2)
の関係を満たす前記2に記載の方向性電磁鋼板。
1.2D≦A≦3D・・・(d)
の関係を満たす前記1~3のいずれかに記載の方向性電磁鋼板。
[方向性電磁鋼板]
本発明では、張力被膜を備えた方向性電磁鋼板の表面に、高エネルギービームを、圧延直角方向と30°以内の方向に連続的または間欠的に照射することによって複数の連続線状または点列状の歪を形成する。母材として使用される方向性電磁鋼板の種類は特に限定されず、各種公知の方向性電磁鋼板を使用することができる。
本発明で使用される方向性電磁鋼板は、表面に張力被膜を備えている。張力被膜の種類は特に限定されず、例えば、最終仕上げ焼鈍において形成されたMg2SiO4を主成分とするフォルステライト被膜と、さらにその上に形成されたリン酸塩系張力被膜からなる2層被膜を、張力被膜として使用することができる。
また、フォルステライト被膜を有していない鋼板の表面に、リン酸塩系の張力付与型絶縁被膜を直接形成することもできる。前記リン酸塩系の張力付与型絶縁被膜は、例えば、金属リン酸塩とシリカを主成分とする水溶液を、鋼板の表面に塗布し、焼付けることによって形成することができる。
なお、本発明では、ビーム照射によって張力被膜が損傷を受けない場合は、ビーム照射後に補修のための再コートを行う必要は無いが、被膜損傷が起こるような場合には300℃以下の低温で形成可能な絶縁と防食とを兼ねたコーティングで再コートを行うのが好ましい。
本発明の方向性電磁鋼板には、圧延方向と交差する方向に直線的に延びる連続線状または点列状の歪(以下、「直線状の歪」と総称することがある。)が複数形成される。この歪は、磁区を細分化して、鉄損を低減する作用を有している。前記複数の直線状の歪は互いに平行であり、後述する所定の間隔で設けられている。
なお、上記歪により還流磁区が生成されるが、かかる歪と還流磁区は、所定条件下では、同じ部位で同じ大きさであり、還流磁区は、後述する手段により特定される。
非耐熱型磁区細分化処理を施した方向性電磁鋼板においては、直線状の歪の方向は圧延直角方向とするか、圧延直角方向からの傾斜を所定の範囲内とするのがよいことが知られている。本発明においても、直線状の歪領域の方向は圧延直角方向から30°以内とする。
上記複数の直線状の歪は、張力被膜を備える鋼板の表面へ、収束された高エネルギービームを照射することによって形成することができる。高エネルギービームの種類は特に限定されないが、中でも、電子ビームは、高加速電圧化による被膜損傷の抑制効果や、高速でビーム制御ができるなどの特徴がある。そのため、本発明では電子ビームを用いることが好ましい。
本発明において線状に生成される還流磁区は、隣接する還流磁区との間隔(隣接する還流磁区が延びる方向と直交する方向での中心間の距離)の平均値、即ち平均間隔L(図1参照)を、15mm以下とする。この平均間隔Lが15mmを超えると十分な磁区細分化効果が得られず、磁区細分化後の鋼板の鉄損が増加する。一方、かかる平均間隔Lは3mm以上とすることが好ましい。該平均間隔Lを3mm以上とすることによって、処理時間を短縮して生産効率を高めることができ、鋼中に形成される歪領域が過度に大きくなってヒステリシス損と磁気歪が増加してしまうことを防止することができる。
なお、還流磁区の間隔は、図1に示すように、鋼板表面で観察した還流磁区の幅中央間の間隔である。また、平均間隔Lは、線状の還流磁区の10本以上について平均した間隔とする。例えば還流磁区10本分を考慮し、その合計の間隔をL10とすると、平均間隔Lは、L10/9で算出される。
方向性電磁鋼板素材の鉄損を十分に改善するためには、板厚方向にできるだけ均一に磁極を導入するのが理想的であり、還流磁区の深さとしては、非耐熱磁区細分化処理を施した面から板厚を基準にして十分に深いのがよい。
本発明では、板厚に対する還流磁区の深さの比率、即ち深さ比率rdを35%以上とすることで、十分に低い鉄損値が得られる。さらにかかる深さ比率rdを39%以上とすることで、より低い鉄損値に到達することが可能である。
また、還流磁区をより深くすることにより、還流磁区の体積率rvおよび還流磁区の面積率rsを、後述にて規定する範囲に制御することが可能となる。なお、深さ比率rdの上限は特に限定されず、100%であっても良い。
還流磁区の体積率rvが大きいと、還流磁区部分を起点とした圧延直角方向への磁束の流れが容易となるため、鉄心内の磁束が圧延方向以外にも流れる必要がある三脚鉄心においてBFが改善される。体積率rvは、十分なBF改善効果を得るために0.30%以上とすることが必要である。また、体積率rvは、3.0%を超えるとヒステリシス損の増加による鉄損の劣化を招くため、3.0%以下とする必要がある。また、変圧器鉄損をさらに理想的に低減するには、体積率rvを0.75%以上とすればよい。
なお、還流磁区の体積率rvは、直線状の歪領域と直交する断面を磁区観察することによって求めることができる。すなわち、図1を参照する通り、磁区観察によって確定された直線状の歪領域と直交する断面における還流磁区の断面積をSR[mm2]とし、板厚をT[mm]とし、また、上述した還流磁区の平均間隔L[mm]を用いて、還流磁区の体積率rvは、{SR/(LT)}×100で算出することができる。
図1に模式的に示した還流磁区は、直線状の歪領域と直交する断面を観察面とした試料を作製し、加工の影響が認められなくなるまで長時間のバフ研磨を施してから、カー効果による磁区観察を行うことで画像から得られる。このようにして得られた画像から、周囲の非処理部とのパターンの違いによって還流磁区部分を確定して、その面積を断面積SRとして求めることができる。
なお、磁区観察の方法は特に限定しないが、カー効果を用いる方法が適している。また、以下、上記断面の、表面近傍(板厚の1/4)を鋼板の表層部、かかる表層部より板厚中心方向(残りの板厚の1/2の部分)を鋼板の内層部という。
本発明の最も重要なポイントは、還流磁区の面積率rsを所定範囲とする点、さらに好ましくは体積率rvに対して一定の関係をもって面積率rsを低減する点にある。なお、還流磁区の面積率rsは、ビーム照射面において評価することとし、かかる面での還流磁区の幅w[mm]と前記平均間隔L[mm)とを用いて、(w/L)×100で算定することができる。
還流磁区は、鋼板の圧延直角方向に磁化成分を生じやすいため、一次的には還流磁区の体積が増加するに従ってBFが改善する。というのは、圧延直角方向の磁化成分の生成が最も大きいのは三相積鉄心変圧器のT接合部あるいはL接合部であり、これら部分での磁化挙動がBFに強く影響しているからと考えられている。すなわち、T接合部あるいはL接合部の回転磁束は、180°磁壁の移動による圧延方向の磁化成分と、磁区構造変化による圧延直角方向の磁化成分により担われており、非耐熱磁区細分化処理材の還流磁区部分の内部では圧延直角方向の磁化の進行が容易になってBFに優れる。したがって、一次的には、還流磁区の体積が大きい方が、BFが改善する傾向となる。
なお、表層部でのみ還流磁区の体積を増加させ、内層部での還流磁区の分布が不均一な状態になると、回転磁束が生じる部分において、表層部では180°磁区構造部分の圧延方向の磁化変化と還流磁区の内部での圧延直角方向の磁化変化とが互いに阻害し合うため、鋼板の鉄損が増加すると予想される。また、ビーム照射を片面からしか行わず還流磁区が存在しないような板厚方向の下部(還流磁区が導入された面と反対側の面付近)では、還流磁区を起点とした180°磁区構造部分の磁区構造変化は起きにくいと推定される。
これに対し、還流磁区の体積率rvに対して還流磁区の面積率rsを一定以下とし、板厚方向の還流磁区分布をより均一にすると、鋼板の表層部と内層部とにおける還流磁区の体積率rvの差が低下するため、回転磁束が生じる部分の鉄損が改善され、変圧器損失(BF)が改善すると考えられる。
なお、上記回転磁束とは、磁化ベクトルの時間変化を追ったとき、磁化ベクトルの原点に対しベクトル先端の軌跡が2次元的であり、円や楕円、菱形やこれらに近い形状となった状態を意味する。
よって、発明1の通り、還流磁区の面積率rsを0.50%以上4.0%以下の範囲とするのが、BFの低減を通じた騒音低減に有効であり、さらに高い効果を得るためには、発明2の通り、式(1):rs≦2.6rvの関係を満たすようにする。また、この効果をより一層高めるには、発明3の通り、式(2):rs≦1.2rv+0.9の関係を満たすようにすればよい。
[還流磁区の面積率rs]
評価する電磁鋼板を消磁後、鋼板表面における還流磁区の幅を求め、還流磁区の面積率rsを算出する。具体的に、還流磁区の面積率rs[%]は、還流磁区の平均間隔L[mm]、還流磁区の幅w[mm](平均幅)を用いて、下式(a):
rs=(w/L)×100・・・(a)
により算出することができる。
上記面積率rsの値の精度を確保するため、上記幅wは、鋼板の板面内の場所を変えて5か所以上の幅を測定し、その平均値として求める。板面から還流磁区の幅を確定するための磁区観察の方法としては、磁性粉体を用いた磁区観察やファラデー効果による磁区観察、高電圧SEM用いた方法が適している。また、板面の絶縁張力被膜を除去し鏡面化してからカー効果による磁区観察を行い、還流磁区の幅を確定してもよい。
更に具体的に、還流磁区の幅w(平均値)は、1本の線状の還流磁区領域について、0.2~5mm間隔の任意の異なる位置での10か所以上の幅wiを測定してその平均値<wi>を求め、このような測定を線状の還流磁区領域10本以上に対して行い、それらの平均値として算出することができる。
また、還流磁区の平均間隔Lは、N本(N≧10)の線状の還流磁区の間隔LNを測定し、LN/(N-1)により算出する。
直線状の歪領域が延びる方向と直交する断面において、カー効果による磁区観察を行い、板厚方向の還流磁区の生成状況を調査し、還流磁区の深さd[mm)および断面積SR[mm2]を求める。そして、板厚に対する還流磁区の深さ比率rd[%]、還流磁区の体積率rv[%]は、板厚T[mm]も用いて、それぞれ下式(b)及び下式(c):
rd=(d/T)×100・・・(b)
rv={SR/(LT)}×100・・・(c)
により算出することができる。
ここで、還流磁区の深さdは、鋼板内の任意の場所で図1に示したように観察されるように、還流磁区部で、最も深い点と鋼板表面との距離を言う。また、断面積SRは、周囲の非処理部と磁区のパターンが異なる還流磁区部分の面積を画像処理により求めれば良い。また、還流磁区の深さdおよび断面積SRは、測定精度確保の観点から、鋼板内で場所を変えて5箇所以上の深さおよび断面積を測定し、それぞれその平均値として求める。
還流磁区を生成させるための直線状の歪を、複数の歪導入部を離散的(点列状)に配置させて形成することにより、より有効に鉄損を低減することが可能となる。この理由の詳細は、明らかではないが、歪導入部を起点として還流磁区が生成し、照射線方向に連結して線状の磁区細分化効果を発揮するとき、点列状の配置であれば、ヒステリシスを劣化させる原因となる歪の導入量(導入体積)を低下させることが可能となるためと考えられる。ここで、エネルギービーム径が歪導入部の領域に対応するため、歪導入部の直径は、エネルギービーム径としてよい。そして、このような歪導入部の直径(すなわちエネルギービーム径)をD[mm]とし、隣接する歪導入部の中心間の距離をA[mm]とするとき、下式(d):
1.2D≦A≦3.0D・・・(d)
の関係を満たせば、材料の鉄損を有効に低減し、同時に本発明のBFや変圧器騒音の改善効果を保つことができる。
1.2D≦A のとき、材料の鉄損低減が図られる理由は、上記のように、最低限の歪導入量で還流磁区を有効に生成させつつ、ヒステリシス損の増加を防止できるからであり、一方、A>3.0Dであると、還流磁区の生成が不十分となり、磁区細分化効果が損なわれる。そのため、式(d)の関係を満たすことが好ましい。
ここで、還流磁区生成のために複数の歪導入部を点列状に配置した場合には、照射線内の位置により還流磁区の生成面積が異なっているため、図1に示したような圧延直角方向と直交する断面での磁区観察による断面積SRの決定が困難となる。
歪導入部は、エネルギービームの中心から半径D/2の領域で広がるところ、隣接する歪導入部が重なるか、または十分に近接している場合(A<1.2Dである場合)には、連続的とみなすことができる。一方、A≧1.2Dである場合には、還流磁区の生成が不均一となるか、もしくは図1のような鋼板面内の照射方向と直交する断面で観察したとき、還流磁区の深さを観察することができなくなる。
このような場合には、磁歪を用いて還流磁区の体積率rv、ひいては深さ比率rdを導出することができる。還流磁区の体積と磁歪λ0-Pは密接な関係を持つことから、磁歪λ0-Pによって、体積率rvを導出することが可能である。これは、磁化の進行によって、板厚方向および圧延垂直方向の磁化成分を有する還流磁区が消失し、圧延方向の磁化成分を持つようになると、鋼板は圧延方向に伸長することになり、材料の磁束密度が最大となった瞬間で最も材料の伸びが大きくなるからである。
そこで、還流磁区を有する状態でのλ0-P Dと歪取り焼鈍によって還流磁区を消失させた状態のλ0-P Pとの差分であるΔλ0-P =λ0-P D - λ0-P Pにより、還流磁区の体積を評価することが可能である。ここでは、最大磁束密度Bm=1.7T、50Hzの磁束正弦波交流磁化条件において磁化させたときの磁歪波形から上記を算出することとした。また、歪取り焼鈍は、700~760℃程度で行うこととする。歪取り焼鈍温度が低すぎると、エネルギービームにより導入した歪を十分に除去することができない。また、歪取り焼鈍温度が高すぎると、コーティング品質の変化などが生じて磁歪特性の変化の評価精度が低下する。
本発明者らの研究によれば、還流磁区の体積率が1.0%のとき、Δλ0-Pが2.6×10-7程度であったので、下記式(e)にて、任意の材料の還流磁区の体積率rv[%]を求めることができる。
rv = {1.0/(2.6×10-7)}×Δλ0-P
= 3.85×106×Δλ0-P ・・・(e)
rv = {SR/(LT)}×100 = {0.80wd/(LT)}×100
rd = (d/T)×100 = {L/(0.80w)}×rv
= {L/(0.80w)}×(3.85×106×Δλ0-P)
= 4.81×(L/w)×Δλ0-P×106 ・・・(f)
また、板厚方向に深い還流磁区を生じさせるにはビーム電流を大きくするとよいが、この場合は鋼板の表層部の還流磁区幅が大きくなり、本発明の条件を満たすことができなくなる。従って、本発明の磁区細分化方向性電磁鋼板では、細い電子ビームを板厚深くまで到達させることが必要であり、以下に述べる既存の製造手法を適正に組み合わせることが好ましい。
電子ビームを用いる場合、その加速電圧は高い方が好ましい。これは、加速電圧が高いほど、電子ビームの物質透過性が高まるためである。加速電圧を十分に大きくすることによって、電子ビームが張力被膜を透過しやすくなるが、加速電圧が高いと、地鉄中での発熱中心が板厚表面からより離れた(深い)位置となるため、板厚方向における還流磁区の深さを大きくすることができる。さらに、加速電圧が高いと、ビーム径を小さくしやすいという利点がある。このような効果を得るために、加速電圧を80kV以上とするのがよく、100kV以上とすることがより好ましい。一方、加速電圧400kV超えでは鋼板の照射反対側まで電子ビームが達して効果が飽和するので、400kV超えとする利点は小さく、400kV以下とすることが好ましい。
ビームの走査方向と直交する方向におけるビーム径は、小さいほど素材鉄損の向上に有利であるが、本発明の効果を得るためには加速電圧に応じて電子ビーム径を小さくすることが有効である。具体的には、加速電圧をVa[kV]としたとき、80kV≦Va≦200kVでビーム径[μm]≦-0.85 Va +270とし、Va>200kVではビーム径100μm以下とするのがよい。
走査方向と直交する方向におけるビーム径の下限は特に限定されないが、8μm以上とすることが好ましい。走査方向と直交する方向におけるビーム径を8μm未満にすると、ワーキングディスタンスを極度に小さくする必要があり、1つの電子ビーム源によって偏向照射可能な領域が大幅に減少してしまう。
一方、走査方向と直交する方向におけるビーム径が8μm以上であれば、1つの電子ビーム源によって広い範囲に対して照射を行うことが可能だからである。なお、走査方向と直交する方向におけるビーム径は、30μm以上とすることがより好ましい。
ビーム電流は、ビーム径縮小の観点からは小さい方が好ましい。ビーム電流が大きすぎると、電子同士のクーロン反発力によって、ビームを収束させることが困難となる。そのため、本発明では、ビーム電流を30mA以下とすることが好ましい。なお、ビーム電流は20mA以下とすることがより好ましい。一方、ビーム電流が小さすぎると、十分な磁区細分化効果を得るために必要な歪を形成することができない。そのため、本発明では、ビーム電流を0.5mA以上とすることが好ましい。なお、ビーム電流は1mA以上とすることがより好ましく、2mA以上とすることがさらに好ましい。
方向性電磁鋼板の母材となる熱延板を熱延板焼鈍した後、冷間圧延により最終板厚(0.23mmまたは0.18mm)としてから脱炭焼鈍を施し、MgOを主成分とする焼鈍分離剤を塗布した後、最終仕上げ焼鈍を行って、フォルステライト被膜を備えた方向性電磁鋼板を作製した。次いで、コロイダルシリカとリン酸マグネシウムを含有する絶縁張力被膜を前記フォルステライト被膜の表面に形成した。その後、鋼板の表面に電子ビームを照射し、圧延方向と交差する方向に延びる複数の直線状の歪領域を形成した。電子ビームの平均走査速度は100m/sとした。また、直線状の歪の、圧延方向に対する角度(線角度)は90°とした。ビーム径Dと歪導入部の間隔Aの関係は、A=0.8Dとした。その他の処理条件は、表1に示した通りである。
かくして得られた鋼板の磁気特性を、単板磁気試験法により最大磁束密度1.7T、周波数50Hzの磁束正弦波条件で評価した。
続いて、上記鋼板から試験用の三相三脚変圧器の鉄心(外寸500mm×500mm、脚および継鉄の幅100mm(矩形断面)、積層厚50mm、接合方法:ステップラップ式(ラップ長3mm))を作製し、変圧器鉄損を測定した。ここでの変圧器鉄損は、変圧器の無負荷鉄損とし、鉄心脚部の最大磁束密度1.7T、周波数50Hzの損失を測定し、鉄心の質量で除した値(単位W/kg)とした。以上の過程で得られた変圧器鉄損を単板での測定による素材鉄損で除した値をBFとした。
上記鋼板に対して消磁(到達最大磁束密度1.95T、周波数50Hz)を施してから、かかる鋼板の表面に対して磁性粉体を用いた磁区観察により還流磁区の幅wを求め、表1に記載のLを用い、還流磁区の面積率rsを式(a)により算出した。なお、wについては鋼板内部の場所を変化させwを測定し、10か所の平均値を求めた。また、LはN本(N≧10)の線状還流磁区の間隔LNを測定し、LN /(N-1)で求めている。
さらに、鋼板の線状の歪領域が延びる方向と直交する断面において、カー効果による磁区観察を行い、板厚方向の還流磁区の生成状況を調査し、還流磁区の深さd、断面積SRを求めた。ここでは、鋼板内で場所を変えて10箇所の深さおよび断面積を測定し、それぞれの平均値としてd及びSRを求め、式(b)、式(c)により、深さ比率rd、体積率rvをそれぞれ算出した。
概略の関係としては従来から知られているように、還流磁区の深さが深くなるに従って、素材損失が改善し、これにより変圧器鉄損も改善される傾向にあるが、中でも本発明に該当する条件では、還流磁区の深さから考えられる効果以上に変圧器鉄損が改善していることがわかる。
また、発明3に適合する条件、発明2に適合する条件、発明1に適合する条件の順に変圧器鉄損の改善効果が大きいことも併せて示されている。
ここでは、それぞれの条件ごとにみると、従来から知られているように、還流磁区の体積率rvが増加するに従いBFが低下する傾向にあるが、本発明の条件では還流磁区の体積率rvの効果以上にBFが改善しており、発明3に適合する条件、発明2に適合する条件、発明1に適合する条件の順にその効果が高いことがわかる。
一般に、非耐熱型の磁区細分化材では、還流磁区の導入量が多いほど鉄損改善効果が高い反面、交流励磁に伴う還流磁区の生成消滅の変化量が大きくなるため、磁歪振幅の増加が発生し変圧器騒音が増加する。このように、変圧器鉄損と変圧器騒音は背反する関係にあるが、図4に示すように、本発明に適合する条件では変圧器鉄損と変圧器騒音のバランスが優れた材料が得られており、発明3に適合する条件、発明2に適合する条件、発明1に適合する条件の順にその効果が高い。
実施例1と同様の方法で、板厚0.23mmの方向性電磁鋼板に対し電子ビームによる磁区細分化処理を施し、鋼板に対して点列状に連なる歪部を導入して非耐熱型の磁区細分化を行った。このとき、ほぼ円形の電子ビーム径Dおよび隣接する歪導入部の中心間の間隔Aを、表2に示した条件とした。
得られた方向性電磁鋼板を用いて、実施例1と同様の変圧器評価を行い、変圧器鉄損と騒音を評価した。この結果を表2に示す。
Claims (4)
- 表面に張力被膜を備え、圧延直角方向と30°以内の方向に延びた線状の還流磁区を生成させることによる磁区細分化処理を施した方向性電磁鋼板であって、
板厚をT[mm]とし、前記磁区細分化処理を施した面を基準にした前記還流磁区の深さをd[mm]とし、前記面での隣接する還流磁区の平均間隔をL[mm]とし、直線状の歪領域と直交する断面における前記還流磁区の断面積をSR[mm2]とし、前記還流磁区の幅をw[mm]とするとき、
前記平均間隔Lが、15mm以下であり、
(d/T)×100で算出される板厚に対する前記還流磁区の深さ比率rdが、35%以上であり、
{SR/(LT)}×100で算出される前記還流磁区の体積率rvが、0.30%以上、3.0%以下であり、
(w/L)×100で算出される前記還流磁区の面積率rsが、0.50%以上、4.0%以下である、方向性電磁鋼板。 - 前記深さ比率rdが39%以上であって、前記体積率rv[%]と前記面積率rs[%]とが、下式(1):
rs≦2.6rv・・・(1)
の関係を満たす請求項1に記載の方向性電磁鋼板。 - 前記体積率rvが0.75%以上であって、前記体積率rv[%]と前記面積率rs[%]とが、下式(2):
rs≦1.2rv+0.9・・・(2)
の関係を満たす請求項2に記載の方向性電磁鋼板。 - 線状の還流磁区を生成させるための直線状の歪が、複数の歪導入部が点列状に配置されることで形成され、前記歪導入部の直径をD[mm]とし、隣接する歪導入部の中心間の間隔をA[mm]とするとき、下式(d):
1.2D≦A≦3D・・・(d)
の関係を満たす請求項1~3のいずれかに記載の方向性電磁鋼板。
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CN115989328A (zh) | 2023-04-18 |
KR20230034355A (ko) | 2023-03-09 |
EP4209602A4 (en) | 2024-02-21 |
JP7287506B2 (ja) | 2023-06-06 |
US20230304123A1 (en) | 2023-09-28 |
JPWO2022050053A1 (ja) | 2022-03-10 |
EP4209602A1 (en) | 2023-07-12 |
MX2023002632A (es) | 2023-03-22 |
CA3187406A1 (en) | 2022-03-10 |
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