WO2024063163A1 - Grain-oriented electrical steel sheet - Google Patents

Abstract

This grain-oriented electrical steel sheet comprises a base steel sheet, a forsterite coating film formed on the surface of the base steel sheet, and an insulation film formed on the surface of the forsterite coating film, wherein: the chemical composition of the base steel sheet contains 0.80 to 7.00% by mass of Si; the area ratio of crystal grains having a distance in the rolling direction between crystal grain boundaries in the surface of the base steel sheet of 3.0 mm to 13.0 mm inclusive is 70% or more; B8 that is a magnetic flux density generated by a magnetic force of 800 A/m is 1.88 T or more; W17/50 that is an iron loss where the frequency is 50 Hz and the maximum magnetic flux density is 1.7 T is 13.1×t2-4.3×t+1.2 (W/kg) or less where the sheet thickness is t (mm); and LvA200Hz that is a 200 Hz component of a magnetostriction waveform is 60 to 78 dBA.

Description

grain-oriented electrical steel sheet

The present invention relates to grain-oriented electrical steel sheets.
This application claims priority based on Japanese Patent Application No. 2022-151341 filed in Japan on September 22, 2022, the contents of which are incorporated herein.

In recent years, there has been an increasing demand for reduced noise and vibration in electromagnetic equipment such as transformers, and the grain-oriented electrical steel sheets used for transformer cores are suitable for low core loss as well as low noise and low vibration. Increasingly, there is a demand for materials with high quality. It is said that one of the causes of transformer noise and vibration in materials is the magnetostriction of grain-oriented electrical steel sheets. The magnetostriction referred to here refers to the fact that when a grain-oriented electrical steel sheet is excited with alternating current, the outer shape of the grain-oriented electrical steel sheet changes slightly due to changes in the strength of magnetization. The magnitude of this magnetostriction is extremely small, on the order of ^10-6 , but the magnetostriction causes vibrations in the iron core, which can cause vibrations in external structures such as transformer tanks. It propagates to create noise.

The magnetostrictive properties change depending on various factors, such as the structure and condition of the grain-oriented electrical steel sheet, specifically the degree of integration of crystal orientation, the tension applied to the steel sheet by the insulating film, and the strain inherent in the steel. When the magnetostrictive properties change, the noise level changes, and in some cases it is possible to reduce the noise.

For example, in Patent Document 1, a grain-oriented electrical steel sheet that can reduce noise from the member when used as a material for an electrical member has an average length DLmax of grains in the rolling direction of 12 mm or more, a coating tension is 1 MPa or less, the plate thickness is 0.35 mm or less, and the length of the grain in the rolling direction is divided into four regions, and from the grain boundaries existing in the two outer regions to the inside of the grain. For the region near the grain boundary where the pointing distance is within 2 mm, the absolute value of the submergence angle of the crystal orientation is β, (area of the region near the grain boundary where β is 4.0° or less)/(total area near the grain boundary) A grain-oriented electrical steel sheet is disclosed in which the area)≧0.50.

Furthermore, Patent Document 2 describes grain-oriented electrical steel sheets with excellent magnetostrictive properties: Si: 3.0 to 7.0 mass%, Mn: 0.04 to 0.15 mass%, Sb: 0.01 to 0.10 mass%. and Sn: 0.01 to 0.20 mass%, the balance is Fe and unavoidable impurities, and the tension imparting insulating film has a total of 10 MPa or more with the tensile stress due to the forsterite film. A grain-oriented electrical steel sheet comprising grains in which the average misorientation angle δ of the crystal orientation with the rolling direction as the rotation axis in Goss-oriented {110}<001> grains is 6° or less, and the grain is compressed in the rolling direction. A grain-oriented electrical steel sheet is disclosed that has a magnetostriction λ _pp of 1.7×10 ⁻⁶ or less when subjected to stress of 3.92 MPa and magnetized at 50 Hz and 1.7 T.

However, the above technology cannot be said to sufficiently improve iron loss characteristics (reduce iron loss). It is known that it is effective to irradiate the surface of a grain-oriented electrical steel sheet with a laser or the like to control the magnetic domain in order to lower iron loss, but the methods of Patent Documents 1 and 2 do not involve laser irradiation. Not applicable to wood.

As a technology for reducing iron loss and magnetostriction by laser beam irradiation, Patent Document 3 describes that B8, which is the magnetic flux density of a steel sheet generated by a magnetizing force of 800 A/m, is 1.92 T or more, and that the rolling direction and easy magnetization are The thickness direction component of the angular deviation of the axis (100) <001> is defined as the β angle, and the crystal grain contains a region in which the absolute value of β angle is 0.5° or less and a region between 2° and 6° at the same time. When the ratio of the total area to the total area of the steel plate is Rs, a grain-oriented electrical steel sheet with Rs of 30% to 100% is selected, and a fiber laser with a fiber core diameter of 5 μm to 400 μm is applied to the surface of the grain-oriented electrical steel sheet. A laser beam is applied periodically and substantially perpendicularly to the rolling direction of the grain-oriented electrical steel sheet, and the width of the surface irradiation mark of the laser beam in the rolling direction or the width of the reflux magnetic domain formed in the laser irradiated area in the rolling direction is A method for manufacturing a grain-oriented electrical steel sheet is disclosed in which the core loss is reduced compared to before the laser beam irradiation by irradiating the laser beam to a depth of 10 μm to 200 μm. Patent Document 3 discloses that according to the above method, a grain-oriented electrical steel sheet with extremely low iron loss and magnetostriction can be provided, especially in a grain-oriented electrical steel sheet with a high magnetic flux density.

However, according to studies conducted by the present inventors, it has been found that reducing the 200 Hz component of the magnetostrictive waveform is effective in reducing transformer noise. In the technique of Patent Document 3, the 200 Hz component of the magnetostrictive waveform was not studied, and the characteristics could not be said to be sufficient in some cases.

Furthermore, Patent Document 4 discloses a new and novel method that can produce a grain-oriented electrical steel sheet with lower core loss when rapid temperature increase is performed at a faster temperature increase rate than before in primary recrystallization annealing. An improved method for manufacturing a grain-oriented electrical steel sheet and a grain-oriented electrical steel sheet manufactured by the method are disclosed. Patent Document 4 indicates that the above technology can reduce noise while improving the magnetic characteristics of a transformer.

However, Patent Document 4 also does not consider the 200 Hz component of the magnetostrictive waveform. Further, Patent Document 4 states that it is assumed that the noise of the transformer increases due to magnetic domain control processing.

Japanese Patent No. 6606991 Japanese Patent No. 5896112 Japanese Patent No. 4616623 International Publication No. 2019/181952

As mentioned above, grain-oriented electrical steel sheets have traditionally been based on the premise of implementing magnetic domain control by laser irradiation to reduce iron loss, but grain-oriented electrical steel sheets that reduce the 200Hz component of the magnetostrictive waveform, which is correlated with transformer noise, are It was not disclosed.
Therefore, an object of the present invention is to provide a grain-oriented electrical steel sheet with low core loss and low noise, which is suitable for application to transformers and the like.

The present inventors conducted a study on reducing the noise of a transformer. As a result, it was found that the noise of the transformer has a strong correlation with the 200 Hz component of the magnetostrictive waveform, and that the noise of the transformer can be reduced by reducing the 200 Hz component of the magnetostrictive waveform.

Furthermore, when the surface of a grain-oriented electrical steel sheet is irradiated with a laser to reduce iron loss, magnetostriction generally increases. That is, there is a trade-off relationship between reducing iron loss and reducing magnetostriction. Therefore, conventionally, when reducing magnetostriction, it was necessary to select conditions that reduce magnetostriction by sacrificing the effect of reducing iron loss to some extent by adjusting irradiation conditions such as laser intensity.
However, it is difficult to further reduce iron loss and magnetostriction at the same time only by adjusting the laser irradiation conditions.
Therefore, the present inventors investigated a method of reducing magnetostriction (particularly the 200 Hz component of the magnetostrictive waveform) without impairing core loss by controlling the structure of a grain-oriented electrical steel sheet.
As a result, it was found that by controlling the grain size (particularly the distance between grain boundaries in the rolling direction), magnetostriction can be reduced without impairing core loss. In addition, it has been found that it is effective to change the curvature of the steel sheet by taking special measures during winding to control the grain size.

The present invention was made in view of the above findings. The gist of the invention is as follows.
[1] A grain-oriented electrical steel sheet according to one aspect of the present invention includes a base steel plate, a forsterite film formed on the surface of the base steel plate, an insulating film formed on the surface of the forsterite film, , the chemical composition of the base steel plate contains Si: 0.80 to 7.00% in mass %, and the distance between grain boundaries of crystal grains in the rolling direction on the surface of the base steel plate is 3.0 mm or more and 13.0 mm or less, the area ratio of the crystal grains is 70% or more, and the magnetic flux density B8 generated by a magnetizing force of 800 A/m is 1.88 T or more, and the base steel plate When the plate thickness is t in mm, the iron loss W17/50 when the frequency is 50 Hz and the maximum magnetic flux density is 1.7 T is 13.1×t ² -4. in W/kg. 3×t+1.2 or less, and LvA200Hz, which is the 200Hz component of the magnetostrictive waveform, is 60 to 78 dBA.
[2] In the grain-oriented electrical steel sheet according to [1], a plurality of linear strains extending in a direction intersecting the rolling direction are formed on the surface of the base steel sheet, and the plurality of linear strains are formed on the surface of the base steel sheet. The strain interval in the rolling direction may be 3 to 10 mm.
[3] The grain-oriented electrical steel sheet according to [1] or [2] is characterized in that, in the base steel sheet, the area ratio of rectangular reflux magnetic domains observed on the surface is 10% or less, and The width of the main magnetic domain may be 1.2 mm or less.
[4] In the grain-oriented electrical steel sheet according to [1] or [2], when the magnetic flux density is 1.92T or more and the plate thickness is 0.18 to 0.23 mm, the W17/50 is It may be 0.74 W/kg or less.
[5] In the grain-oriented electrical steel sheet according to [3], when the magnetic flux density is 1.92T or more and the plate thickness is 0.18 to 0.23 mm, the W17/50 is 0.74 W/ It may be less than kg.

According to the above aspect of the present invention, it is possible to provide a grain-oriented electrical steel sheet with low iron loss and noise (excellent iron loss characteristics and noise characteristics).

This is an example of the observed magnetic domain pattern. It is a figure explaining a reflux magnetic domain (lancet). FIG. 6 is a diagram showing an example of the arrangement of spacers placed between steel plates in a winding process. It is a figure which shows the example of the aspect which applies an annealing separator in a winding process.

A grain-oriented electrical steel sheet according to an embodiment of the present invention (a grain-oriented electrical steel sheet according to the present embodiment) includes a base steel plate, a forsterite film formed on the surface of the base steel plate, and a forsterite film formed on the surface of the forsterite film. and an insulating film formed.
Further, in the grain-oriented electrical steel sheet according to the present embodiment, the chemical composition of the base material steel sheet contains Si: 0.80 to 7.00% in mass %, and the surface of the base material steel sheet contains crystals in the rolling direction. The area ratio of crystal grains in which the distance between grain boundaries is 3.0 mm or more and 13.0 mm or less is 70% or more, and B8, which is the magnetic flux density generated by a magnetizing force of 800 A/m, is 1.88 T or more. When the plate thickness is expressed as t in mm, the iron loss W17/50 when the frequency is 50 Hz and the maximum magnetic flux density is 1.7 T is expressed as 13.1×t ² - in W/kg. 4.3×t+1.2 or less, and LvA200Hz, which is the 200Hz component of the magnetostrictive waveform, is 60 to 78 dBA.
Each will be explained below.

<Base material steel plate>
(chemical composition)
Si: 0.80-7.00%
Si (silicon) is an element that increases the electrical resistance of grain-oriented electrical steel sheets and improves core loss characteristics. If the Si content is less than 0.80%, a sufficient eddy current loss reduction effect cannot be obtained. Therefore, the Si content is set to 0.80% or more. The Si content is preferably 1.00% or more, more preferably 1.20% or more.
On the other hand, if the Si content exceeds 7.00%, the steel plate becomes brittle and may break during rolling. In addition, the workability of the grain-oriented electrical steel sheet is reduced. Therefore, the Si content is set to 7.00% or less. The Si content is preferably 6.80% or less, more preferably 6.70% or less, even more preferably 4.00% or less.

As long as the base steel sheet included in the grain-oriented electrical steel sheet according to the present embodiment contains 0.80 to 7.00% Si in mass% as a chemical composition, the content of other elements is not particularly limited. Not done.
However, in addition to Si, the following elements may be included in the ranges shown below as components (elements) constituting the chemical composition, depending on the properties required as a grain-oriented electrical steel sheet. In the present embodiment, % concerning the content of each element is mass % unless otherwise specified.

C: 0.070% or less C (carbon) is an element effective in controlling the structure of the steel sheet in the manufacturing process up to the completion of the decarburization annealing process. However, when the C content exceeds 0.070%, the magnetic properties of the grain-oriented electrical steel sheet, which is a product sheet, deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the C content is preferably 0.070% or less. The C content is more preferably 0.050% or less, still more preferably 0.020% or less. The lower the C content, the better, but even if the C content is reduced to less than 0.0001%, the effect of structure control will be saturated and the manufacturing cost will only increase. Therefore, the C content may be 0.0001% or more.

Mn: 0.01-0.50%
Mn (manganese) is an element that combines with S to form MnS during the manufacturing process. These precipitates function as inhibitors (suppressants of normal grain growth) and cause secondary recrystallization to occur in steel. Mn is an element that also improves the hot workability of steel. When the Mn content is less than 0.01%, the above effects cannot be sufficiently obtained. Therefore, the Mn content is preferably 0.01% or more. The Mn content is more preferably 0.02% or more.
On the other hand, when the Mn content exceeds 0.50%, secondary recrystallization does not occur and the magnetic properties of the steel deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the Mn content is preferably 0.50% or less. The Mn content is more preferably 0.20% or less, still more preferably 0.10% or less.

N: 0.0100% or less N (nitrogen) is an element that combines with Al in the manufacturing process to form AlN that functions as an inhibitor. When the N content exceeds 0.0100%, an excessive amount of inhibitor remains in the grain-oriented electrical steel sheet, and the magnetic properties deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the N content is preferably 0.0100% or less. The N content is more preferably 0.0080% or less.
On the other hand, although the lower limit of the N content is not particularly defined, even if the N content is reduced to less than 0.0010%, the manufacturing cost will only increase. Therefore, the N content may be 0.0010% or more.

sol. Al: 0.030% or less sol. Al (acid-soluble aluminum) is an element that combines with N to form AlN that functions as an inhibitor during the manufacturing process of grain-oriented electrical steel sheets. However, the sol. When the Al content exceeds 0.030%, an excessive amount of inhibitor remains in the base steel sheet, and the magnetic properties deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, sol. The Al content is preferably 0.030% or less. sol. The Al content is more preferably 0.020% or less, still more preferably 0.015% or less. sol. Although the lower limit of the Al content is not particularly defined, even if it is reduced to less than 0.0001%, the manufacturing cost will only increase. Therefore, sol. The Al content may be 0.0001% or more.

S: 0.010% or less S (sulfur) is an element that combines with Mn in the manufacturing process to form MnS that functions as an inhibitor. However, when the S content exceeds 0.010%, the magnetic properties deteriorate due to the remaining inhibitor. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the S content is preferably 0.010% or less. The S content in the grain-oriented electrical steel sheet is preferably as low as possible. For example, it is less than 0.001%. However, even if the S content in the grain-oriented electrical steel sheet is reduced to less than 0.0001%, the manufacturing cost will only increase. Therefore, the S content in the grain-oriented electrical steel sheet may be 0.0001% or more.

Remainder: Fe and Impurities The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment may contain, for example, the above-mentioned elements, and the remainder may be Fe and impurities. However, for the purpose of improving magnetic properties etc., P, Cr, Sn, Cu, Se, Sb, and Mo may be further contained in the ranges shown below (the lower limit is 0% as they do not need to be contained). be). Furthermore, even if any one or two or more of W, Nb, Ti, Ni, Bi, Co, and V are contained as elements other than these in a total amount of 1.0% or less, the directionality according to the present embodiment may be improved. It does not impede the effectiveness of the electromagnetic steel sheet.
Here, impurities are those that are mixed in from ore or scrap as raw materials or from the manufacturing environment when the base material steel sheet is industrially manufactured, and the effects of the grain-oriented electrical steel sheet according to this embodiment. It means an element that is allowed to be contained in a content that does not have a negative effect on.

P: 0-0.030%
P (phosphorus) is an element that reduces workability in rolling. By controlling the P content to 0.030% or less, it is possible to suppress excessive deterioration of rolling workability and to suppress breakage during manufacturing. From this point of view, the P content is preferably 0.030% or less. The P content is more preferably 0.020% or less, and even more preferably 0.010% or less.
There is no lower limit for the P content, and the P content may be 0%, but in practical steel sheets, the practical lower limit for the P content is 0.0001%. P is also an element that has the effect of improving texture and magnetic properties. In order to obtain this effect, the P content may be set to 0.001% or more, or may be set to 0.005% or more.

Cr: 0 to 0.50%
Cr (chromium) is an element that contributes to an increase in the Goss orientation occupancy rate in the secondary recrystallized structure and improves magnetic properties. In order to obtain the above effect, the Cr content is preferably 0.01% or more, more preferably 0.05% or more, and even more preferably 0.10% or more.
On the other hand, if the Cr content exceeds 0.50%, Cr oxides are formed and the magnetic properties deteriorate, so the Cr content is preferably 0.50% or less, more preferably 0.30% or less, and further preferably 0.15% or less.

Sn: 0-0.50%
Sn (tin) is an element that contributes to improving magnetic properties through primary recrystallization structure control. In order to obtain the effect of improving magnetic properties, the Sn content is preferably 0.01% or more. The Sn content is more preferably 0.02% or more, still more preferably 0.03% or more.
On the other hand, if the Sn content exceeds 0.50%, secondary recrystallization becomes unstable and magnetic properties deteriorate. Therefore, the Sn content is preferably 0.50% or less. The Sn content is more preferably 0.30% or less, still more preferably 0.10% or less.

Cu: 0-0.50%
Cu (copper) is an element that contributes to an increase in the Goss orientation occupancy in the secondary recrystallized structure. Cu is an optional element in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment. Therefore, the lower limit of the Cu content is 0%, but in order to obtain the above effects, it is preferable that the Cu content is 0.01% or more. The Cu content is more preferably 0.02% or more, still more preferably 0.03% or more.
On the other hand, if the Cu content exceeds 0.50%, the steel sheet becomes brittle during hot rolling. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, the Cu content is preferably 0.50% or less. The Cu content is more preferably 0.30% or less, still more preferably 0.10% or less.

Se: 0-0.020%
Se (selenium) is an element that has the effect of improving magnetic properties. Therefore, it may be included. When Se is contained, the content is preferably 0.001% or more in order to exhibit a good effect of improving magnetic properties. The Se content is more preferably 0.003% or more, and still more preferably 0.006% or more.
On the other hand, if the Se content exceeds 0.020%, the adhesion of the forsterite film deteriorates. Therefore, it is preferable that the Se content is 0.020% or less. The Se content is more preferably 0.015% or less, even more preferably 0.010% or less.

Sb: 0-0.50%
Sb (antimony) is an element that has the effect of improving magnetic properties. Therefore, it may be included. When Sb is contained, the content is preferably 0.005% or more in order to exhibit a good effect of improving magnetic properties. The Sb content is more preferably 0.01% or more, and still more preferably 0.02% or more.
On the other hand, if the Sb content exceeds 0.50%, the adhesion of the forsterite film will deteriorate significantly. Therefore, it is preferable that the Sb content is 0.50% or less. The Sb content is more preferably 0.30% or less, still more preferably 0.10% or less.

Mo: 0-0.10%
Mo (molybdenum) is an element that has the effect of improving magnetic properties. Therefore, it may be included. When Mo is contained, the Mo content is preferably 0.01% or more in order to exhibit a good effect of improving magnetic properties. The Mo content is more preferably 0.02% or more, and still more preferably 0.03% or more.
On the other hand, if the Mo content exceeds 0.10%, cold rolling properties may deteriorate and breakage may occur. Therefore, it is preferable that the Mo content is 0.10% or less. The Mo content is more preferably 0.08% or less, still more preferably 0.05% or less.

As mentioned above, the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet in this embodiment is the above-mentioned C, Si, Mn, N, sol. Contains Al and S, with the remainder consisting of Fe and impurities, or C, Si, Mn, N, sol. Contains the elements Al and S, and further contains one or more of P, Cr, Sn, Cu, Se, Sb, Mo, W, Nb, Ti, Ni, Bi, Co, and V, with the remainder being Fe and impurities. For example, it consists of: The total content of the elements W to V may be 0.05% or less.

The content of Si in the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment is determined by the method prescribed in JIS G 1212 (1997) (silicon quantitative method). Specifically, when the above-mentioned chips are dissolved in acid, silicon oxide precipitates out, so this precipitate (silicon oxide) is filtered off with a filter paper, the mass is measured, and the Si content is determined. .
Other chemical compositions of the base steel plate may be determined by a well-known component analysis method. Specifically, chips are generated from a base steel plate using a drill, the chips are collected, and the collected chips are dissolved in acid to obtain a solution. ICP-AES is performed on the solution to perform elemental analysis of the chemical composition.
However, elements that are difficult to measure with ICP-AES, such as C content and S content, are determined by the well-known high frequency combustion method (combustion-infrared absorption method). Specifically, the above-mentioned solution may be burned by high-frequency heating in an oxygen stream, and the generated carbon dioxide and sulfur dioxide may be detected to determine the C content and S content. Further, the N content may be determined using the well-known inert gas melting-thermal conductivity method.
In the grain-oriented electrical steel sheet according to the present embodiment, if a forsterite film and/or an insulating film are formed on the surface, these films are removed before measuring the chemical composition of the base steel sheet.
The insulation film is formed by immersing a grain-oriented electrical steel sheet in a sodium hydroxide aqueous solution containing 30-50% by mass of NaOH and 50-70% by mass of H ₂ O at 80-90°C for 7-10 minutes. , can be removed.
Further, the grain-oriented electrical steel sheet from which the insulating film has been removed is washed with water, and then dried with a warm air blower for a little less than 1 minute. By immersing the dried grain-oriented electrical steel sheet (grain-oriented electrical steel sheet without an insulating film) in a hydrochloric acid aqueous solution containing 30 to 40% by mass of HCl and at 80 to 90°C for 1 to 10 minutes, Forsterite film can be removed.
By washing the base steel plate after immersion with water, and drying it with a hot air blower for a little less than 1 minute after rinsing with water, the base steel plate can be taken out from the grain-oriented electrical steel sheet having a forsterite film and an insulating film.

(microstructure)
In the grain-oriented electrical steel sheet according to this embodiment, the grain size in the rolling direction is controlled in its microstructure. Specifically, the area ratio of crystal grains on the surface of the base steel plate, where the distance between grain boundaries in the rolling direction is 3.0 mm or more and 13.0 mm or less, is 70% or more.
Grain boundaries transverse to the rolling direction change the magnetic domain pattern. In particular, as the distance between the grain boundaries becomes shorter, the 200 Hz component (sometimes referred to as LvA200 Hz) of the magnetostrictive waveform decreases. This is presumed to be due to the fact that as the distance between grain boundaries becomes shorter, the width of the main magnetic domain becomes narrower, which has the effect of suppressing the reflux magnetic domain (lancet) within the grains.
If the area ratio of crystal grains in which the distance between grain boundaries in the rolling direction (grain boundary spacing) is 3.0 mm or more and 13.0 mm or less is less than 70%, the effect of reducing LvA 200 Hz cannot be sufficiently obtained. The area ratio of crystal grains having a grain boundary interval of 3.0 mm or more and 13.0 mm or less is preferably 75% or more, more preferably 80% or more, and even more preferably 90% or more. The upper limit of the area ratio is not limited and may be 100%.
The reason why the grains whose area ratio is to be controlled are grains (regions) in which the distance between grain boundaries is 3.0 mm or more and 13.0 mm or less is that for grains with a grain boundary spacing of more than 13.0 mm, This is because the domain wall interval is not sufficiently narrowed, and the effect of reducing LvA200Hz is small. On the other hand, from the point of view of reducing LvA200Hz, it is preferable to have a short grain boundary spacing, but there is a concern that crystal grains with a grain boundary spacing of less than 3.0 mm may impede the movement of domain walls and deteriorate iron loss characteristics. It is from.
FIG. 1 shows an example of a magnetic domain pattern observed in a grain-oriented electrical steel sheet according to this embodiment.

In order to obtain the above microstructure, there is a method of irradiating the base steel plate with a laser so that its scanning direction crosses the rolling direction, but care must be taken to avoid producing fine grains on the irradiation marks. Irradiation is preferred. By preventing the generation of fine grains, it is possible to suppress the generation of crystal grains on the surface of the base steel sheet in which the distance between the grain boundaries of grains in the rolling direction is less than 3.0 mm.
The average grain size in the rolling direction is preferably 3.0 to 20.0 mm.
If the average crystal grain size is small, it becomes difficult to make the area ratio of crystal grains with a distance between grain boundaries (grain boundary spacing) of 3.0 mm or more and 13.0 mm or less in the rolling direction to 70% or more. At the same time, there is a concern that the movement of the domain walls will be hindered, leading to deterioration of core loss characteristics. On the other hand, if the average grain size exceeds 20.0 mm, it becomes difficult to increase the area ratio of crystal grains having a size of 3.0 mm or more and 13.0 mm or less to 70% or more, and there is a concern that noise may increase.

The area ratio of crystal grains in which the distance between grain boundaries in the rolling direction is 3.0 mm or more and 13.0 mm or less can be determined by the following method.
First, the distance between grain boundaries in the rolling direction is measured by observing magnetic domains on the surface of a grain-oriented electrical steel sheet using a magnetic domain observation element. Specifically, the surface of a grain-oriented electrical steel sheet is observed using a reflection electron microscope or an MO sensor that utilizes the Faraday effect, and images are obtained. , is determined by determining the grain boundaries and measuring the distance between the grain boundaries in the rolling direction.
The area ratio of crystal grains with a predetermined grain boundary spacing is determined by observing an area of 100 mm in the width direction of the surface and 500 mm in the rolling direction, and in this observation range, the inter-grain boundary distance in the rolling direction is 3.0 mm or more.13. It is determined by dividing the area of crystal grains of 0 mm or less by the area of the measurement region (when expressed as a percentage, it is set as ×100). At that time, using a scale along the rolling direction, identify crystal grains that deviate from 3.0 mm to 13.0 mm, measure the area, and subtract it from the area of the measurement area. (crystal grains having an inter-grain boundary distance of 3.0 mm or more and 13.0 mm or less) may be measured.
In addition, when making the above measurements, by drawing a 500 mm straight line from end to end in the rolling direction of the observation range and dividing the length of this straight line by the number of grain boundaries that intersect with this, the average in the rolling direction can be calculated. Particle size can also be measured.
The area ratio is measured on the surface of the base steel plate. According to the above method, it is possible to measure even if a forsterite film and an insulating film are formed on the base steel sheet, so there is no need to remove the forsterite film and insulating film when making measurements. It may be measured from

In the grain-oriented electrical steel sheet according to the present embodiment, as shown in FIG. 2, in the magnetic domains observed on the surface of the base steel sheet, short strip-shaped return magnetic domains (lancets) 100 are present in the main magnetic domain. In the grain-oriented electrical steel sheet according to the present embodiment, it is preferable that the area ratio of the reflux magnetic domain (lancet) 100 be 10% or less of the whole. If the area ratio of the reflux magnetic domain 100 exceeds 10%, it becomes difficult to obtain a predetermined magnetic flux density and iron loss. The lower limit of the area ratio is not limited and may be 0%.
Further, in the grain-oriented electrical steel sheet according to the present embodiment, it is preferable that the width of the main magnetic domain, which appears divided into stripes observed on the surface, be 1.2 mm or less. If the width increases beyond this, lancets 100 are likely to occur, making it difficult to obtain predetermined magnetic flux density and iron loss. More preferably, the width of the main domain is 1.0 mm or less, and even more preferably 0.9 mm or less. The width of the main magnetic domain is influenced by the average grain size in the rolling direction, and the intensity of strain caused by differences in laser irradiation conditions and curvature in the coil state.

The area ratio of the reflux magnetic domain and the width of the main magnetic domain are measured on the surface of the base steel plate in an area of 100 mm in the width direction x 500 mm in the rolling direction using a measuring instrument such as CMOS-MagView that utilizes the magneto-optical effect. According to this method, magnetic domains can be observed even in coated electromagnetic steel sheets. Thereafter, the area of the surface of the steel plate of the lancet is measured based on the obtained image, the proportion of its presence in the whole is evaluated, and the width of the main magnetic domain is measured. However, observation is performed in a demagnetized state.

(Magnetic properties)
The grain-oriented electrical steel sheet according to this embodiment has its magnetic domain controlled by laser irradiation, and has excellent magnetic properties. Specifically, B8, which is the magnetic flux density generated by a magnetizing force of 800 A/m, is 1.88 T or more, and when the thickness of the base steel plate is expressed in mm, the frequency is 50 Hz, and the maximum magnetic flux is W17/50, which is the iron loss when the density is 1.7T, is equal to or less than 13.1×t ² −4.3×t+1.2 in unit W/kg. If B8 is less than 1.88T or W17/50 is more than 13.1×t ² -4.3×t+1.2W/kg, the magnetic properties cannot be said to be sufficient.
Although it is preferable that B8 be higher, if the area of the crystal grains mentioned above is increased, the practical upper limit is about 1.95T, so B8 may be set to 1.95T or less.
Moreover, the plate thickness t is the nominal thickness, and if t=0.23 mm, W17/50 is 0.90 W/kg or less.
B8 and W17/50 are achieved by controlling fine regions such as texture and magnetic domains by controlling the manufacturing method including laser irradiation, but there are multiple factors that change magnetic properties and it is easy to measure. isn't it. Therefore, the grain-oriented electrical steel sheet according to the present embodiment is defined by the values of B8 and W17/50.
As for magnetic properties, B8 preferably has a value of 1.92T or more. Further, the iron loss is preferably such that W17/50 is 0.74 W/kg or less when the plate thickness (t) is in the range of 0.18 to 0.23 mm.

B8 and W17/50 are measured using a single sheet magnetic property measurement method (Single Sheet Tester) according to JIS C 2556:2015, using a test piece cut out from a grain-oriented electrical steel sheet with a size of 100 mm in the width direction and 500 mm in the rolling direction. SST).

(Noise characteristics)
In the grain-oriented electrical steel sheet according to the present embodiment, LvA200Hz, which is the 200Hz component of the magnetostrictive waveform, is 60 to 78 dBA. Thereby, when used as a material for a transformer, the noise of the transformer can be reduced. When LvA200Hz exceeds 78 dB, the noise reduction effect is small. On the other hand, when ensuring predetermined magnetic characteristics, it is not easy to make LvA200Hz less than 60 dBA, so LvA200Hz is made to be 60 dBA or more.

LvA200Hz is determined by measuring the expansion and contraction of the steel plate using a laser Doppler vibration measuring device in accordance with IEC standard IEC 606404-17 ED1.
During the measurement, the expansion and contraction of the steel plate is generated by applying a 50 Hz magnetic field from the outside. After obtaining the length expansion/contraction with respect to time as a magnetostrictive waveform, this waveform is subjected to frequency analysis, separated into 100 Hz and 200 Hz components, and evaluated.

As a result of magnetic domain control, the grain-oriented electrical steel sheet according to the present embodiment has the above-mentioned B8 and W17/50, and has an LvA of 200 Hz of 60 to 78 dBA. That is, the grain-oriented electrical steel sheet according to this embodiment is a magnetic domain control material.
Although the method of magnetic domain control is not limited, it is preferable to perform magnetic domain control by, for example, performing laser irradiation under the conditions described below. In this case, a plurality of linear strains extending in a direction intersecting the rolling direction are formed on the surface of the base steel plate, and the intervals between the plurality of linear strains in the rolling direction are 3 to 10 mm. Therefore, the interval between the plurality of linear strains in the rolling direction is preferably 3 to 10 mm.
The interval between linear strains in the rolling direction is the distance in the rolling direction from the center of a linear strain in the width direction to the center of an adjacent linear strain in the width direction.
Further, the width of the linear strain in the rolling direction is preferably 250 μm or less in terms of contributing to improving iron loss characteristics. The linear shape includes a continuous linear shape and a dotted linear shape.

The location where linear strain exists can be analyzed using a residual strain measurement technique using X-ray diffraction (for example, K. Iwata, et. al, j. Appl. Phys. 117.17A910 (2015)). Further, if traces of energy ray irradiation can be confirmed on the surface of the steel plate, the traces of irradiation may be directly determined as distortion.
Regarding the observed linear strain, set a certain distance L of at least L > 5 mm in the rolling direction, count the number n of strains existing there, and calculate L/n as the linear strain. It may also be the interval in the rolling direction. The width of the linear strain in the rolling direction may be the average value of the widths of each of the n measured lines.

(plate thickness)
The thickness of the base steel plate of the grain-oriented electrical steel sheet according to this embodiment is not limited, but when considering application to the core of a transformer that requires low iron loss and low noise, it is 0.17~ Preferably, it is 0.30 mm.
The thinner the plate thickness is, the more the effect of reducing eddy current loss can be enjoyed, and the better the iron loss can be obtained. Therefore, the upper limit of the preferable plate thickness of the base steel plate is 0.30 mm. On the other hand, special equipment is required to manufacture a base steel plate with a thickness of less than 0.17 mm, which is unfavorable in terms of production, such as increased manufacturing costs. Therefore, the lower limit of the industrially preferable plate thickness is 0.17 mm. Preferably it is 0.18 to 0.23 mm.

<Forsterite film>
In the grain-oriented electrical steel sheet according to this embodiment, a forsterite film (also referred to as a glass film) is formed on the surface of the base steel sheet. The forsterite film may be any known film. Generally, it is an inorganic film whose main component is magnesium silicate.
The forsterite film is formed during finish annealing when an annealing separator containing magnesia (MgO) applied to the surface of the base steel plate reacts with components on the surface of the base steel plate, and the annealing separator and base metal It has a composition derived from the components of the steel plate, and consists of a structure containing _four Mg ₂ SiO phases (50 area % or more) as the main phase and _four MgAl ₂ O phases. Other than these phases, about 1% or less of precipitates may be included.

<Insulating film>
In the grain-oriented electrical steel sheet according to this embodiment, an insulating film (tension-providing insulating film) is formed on the surface of the forsterite film. The insulating film may be any known film used in the art.
The insulating film reduces eddy current loss by imparting electrical insulation to the grain-oriented electrical steel sheet, thereby improving the core loss characteristics of the grain-oriented electrical steel sheet (reducing core loss). Furthermore, in addition to the above-mentioned electrical insulation properties, the insulating film provides various properties such as corrosion resistance, heat resistance, and slip properties. Furthermore, the insulating film has the function of imparting tension to the grain-oriented electrical steel sheet. By applying tension to the grain-oriented electrical steel sheet to facilitate domain wall movement in the grain-oriented electrical steel sheet, the iron loss of the grain-oriented electrical steel sheet can be reduced (the iron loss characteristics can be improved). The insulating film is formed, for example, by applying a coating liquid containing metal phosphate and silica as main components to the surface of the forsterite film and baking it.

<Manufacturing method>
The grain-oriented electrical steel sheet according to this embodiment can be manufactured by a manufacturing method including the following steps.
(i) Hot rolling step of hot rolling a steel billet having a predetermined chemical composition to obtain a hot rolled sheet (hot rolled steel sheet) (ii) Cold rolling the hot rolled sheet to obtain a cold rolled sheet (iii) A decarburization annealing step of subjecting the cold rolled sheet to decarburization annealing (iv) An annealing separator containing MgO to the cold rolled sheet after the decarburization annealing step (v) A final annealing step in which the material is coated, wound into a coil shape, and final annealed (v) An insulating film forming step (v) in which an insulating film is formed on the surface of the cold rolled sheet after the final annealing to obtain a grain-oriented electrical steel sheet ( vi) Laser irradiation step of irradiating the grain-oriented electrical steel sheet provided with the insulating film with a laser Further, the method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment may further include the following steps.
(I) A hot-rolled plate annealing step for annealing the hot-rolled sheet (II) A nitriding step for increasing the amount of nitrogen in the cold-rolled sheet In the method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment, the above (iv) finishing It is characterized by the annealing process and (vi) laser irradiation process. Preferred conditions in these steps will be explained below. In other steps, known manufacturing conditions for grain-oriented electrical steel sheets can be applied.
Each process will be explained.

(Hot rolling process)
In the hot rolling process, a steel piece such as a slab is heated and then hot rolled to obtain a hot rolled plate. The heating temperature of the steel piece is not particularly limited, but it is preferably within the range of 1100 to 1450°C.
The hot rolling conditions are not particularly limited and may be appropriately set based on the required characteristics. The thickness of the hot rolled sheet obtained by hot rolling is preferably within the range of 2.0 to 3.0 mm, for example.
The chemical composition of the steel slab should be set in a preferable range to obtain the chemical composition of the base steel plate mentioned above, taking into account the manufacturing process after the hot rolling process (taking into account changes in the chemical composition in each process). do it.

(Hot rolled plate annealing process)
The hot rolled sheet annealing process is a process of annealing a hot rolled sheet manufactured through a hot rolling process. By performing such an annealing treatment, recrystallization occurs in the steel sheet structure, making it possible to realize good magnetic properties. Therefore, it may be implemented.
When hot-rolled sheet annealing is performed, a hot-rolled sheet manufactured through a hot rolling process may be annealed according to a known method. The annealing conditions are not particularly limited, but, for example, the hot rolled sheet can be annealed in a temperature range of 900 to 1200° C. for 10 seconds to 5 minutes. The means for heating the hot-rolled sheet during annealing is also not particularly limited, and any known heating method may be employed. Two-stage annealing may be performed in which the annealing temperature is changed midway through.

(cold rolling process)
In the cold rolling step, the hot rolled sheet after the hot rolled sheet annealing step is subjected to cold rolling including a plurality of passes to obtain a cold rolled sheet. The cold rolling may be a single cold rolling (a series of cold rolling without intervening intermediate annealing), or before the final pass of the cold rolling process, the cold rolling is interrupted and at least one or two or more intermediate annealings are performed. Then, cold rolling may be performed multiple times with intermediate annealing.
When performing intermediate annealing, it is preferable to maintain the temperature at 1000 to 1200°C for 5 to 180 seconds. The annealing atmosphere is not particularly limited. The number of times of intermediate annealing is preferably 3 times or less in consideration of manufacturing cost.
In the cold rolling step, the hot rolled sheet may be cold rolled to obtain a cold rolled sheet according to a known method. For example, the final rolling reduction can be in the range of 80-95%. By setting the final rolling reduction to 80 to 95%, it is possible to obtain Goss nuclei in which the {110}<001> orientation has a high degree of accumulation in the rolling direction, and to suppress destabilization of secondary recrystallization.
The final rolling reduction is the cumulative rolling reduction of cold rolling, and in the case of intermediate annealing, the final rolling reduction is the cumulative rolling reduction of cold rolling after the final intermediate annealing.
Further, before the cold rolling process, the surface of the hot rolled sheet may be pickled under known conditions.

(Decarburization annealing process)
In the decarburization annealing step, the cold rolled sheet is decarburized and annealed. In decarburization annealing, the cold-rolled sheet is primarily recrystallized, and C, which has an adverse effect on magnetic properties, is removed from the steel sheet. Further, in the decarburization annealing step, the number of Goss nuclei is increased in order to make secondary recrystallized grains obtained during final annealing described later finer. Considering that the grain boundaries themselves function as magnetic poles (sites where leakage magnetic flux is generated), the magnetostatic energy of the entire system increases as the secondary recrystallized grains become finer. That is, the driving force of magnetic domain refining becomes high.
The conditions for decarburization annealing may be within a known range, and examples include conditions in which the annealing temperature is 750 to 900° C. and held for 10 to 600 seconds in a wet hydrogen or nitrogen atmosphere. In terms of controlling the average grain size in consideration of the balance between iron loss and noise, the optimal decarburization annealing temperature is about 835 to 845°C.

(Nitriding process)
In the nitriding process, the amount of nitrogen in the steel sheet is increased. The nitriding process is performed at one or more of the following timings: during the decarburization annealing process, between the decarburization annealing process and the final annealing process, or during the temperature increase process of the final annealing process until the start of secondary recrystallization. It's fine if you do it.
Methods for increasing the amount of nitrogen in a steel sheet include controlling the amount of nitrogen in the steel sheet by annealing it in an atmosphere containing a gas capable of nitriding; An example of this method is to add a powder capable of nitriding, such as, into an annealing separator.

(Final annealing process)
In the final annealing process, a predetermined annealing separator is applied to one or both sides of the cold-rolled sheet obtained in the decarburization annealing process or which has been further nitrided, and then wound into a coil shape and finished. Perform annealing.
When manufacturing the grain-oriented electrical steel sheet according to the present embodiment, a certain curvature or more is given to the steel sheet (steel strip) when it is wound into a coil. Thereby, the distance between grain boundaries in the rolling direction is controlled, and the area ratio of crystal grains having a distance between grain boundaries of 3.0 to 13.0 mm is increased.
There are two methods for giving curvature:
(a) During winding, a spacer is placed between the steel plates.
(b) Periodically changing the amount of annealing separator applied.
Below, (a) and (b) will be explained.
Even without performing (a) or (b), a curvature is imparted to the steel plate when it is made into a coil. Moreover, a larger curvature is given to the inside of the coil than to the outside. However, in normal winding, it is not possible to impart a sufficient curvature to the steel sheet to obtain the grain-oriented electrical steel sheet according to the present embodiment even on the inside of the coil, which has a relatively large curvature.

(a) Arranging spacers between steel plates In this method, as shown in Fig. 3, when winding a steel plate 1 into a coil, ceramic round bars are placed as spacers 2 periodically perpendicular to the winding direction. The curvature of the steel plate is changed periodically. The steel plate is given a curvature by meandering so as to alternately touch the front surface, the back surface, the front surface, the back surface, etc. with respect to the spacers 2 adjacent to each other in the rolling direction of the steel plate.
If the curvature is small, the area ratio of crystal grains having a distance between grain boundaries of 3.0 to 13.0 mm cannot be sufficiently increased. On the other hand, if the curvature is too large, a preferable crystal orientation cannot be obtained and the magnetic properties deteriorate. In order to obtain a predetermined curvature, the diameter (φ) of the spacer 2 (ceramic round bar) is 3 to 20 mm, and the interval between the spacers 2 (L1 in FIG. 3) is 15 to 100 mm with respect to the rolling direction of the steel plate 1. do.

(b) Periodically changing the amount of annealing separator 3 applied In this method, as shown in Fig. 4, by changing the amount (thickness) of the annealing separator 3 applied, the steel plate becomes wavy along the rolling direction. so that it becomes
In order to impart a constant curvature, the annealing separator is applied so that the wave height (h in FIG. 4) changes by 3 to 20 mm at a period of 15 to 100 mm (L2 in FIG. 4) with respect to the rolling direction of the steel plate 1. Apply (place) 3.

The annealing separator is applied to the cold-rolled sheet for the purpose of preventing seizure between the inside and outside of the windings of the coil and to form a forsterite film.
In the method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment, an annealing separator containing MgO as a main component (for example, containing 80% by mass or more) is used as the annealing separator to be applied. By using an annealing separator containing MgO as a main component, a forsterite film can be formed on the surface of the base steel plate. If MgO is not the main component, no primary film (forsterite film) is formed. This is because the forsterite film is a Mg ₂ SiO ₄ or MgAl ₂ O ₄ compound and lacks Mg necessary for the formation reaction.
The annealing separator may further contain TiO ₂ . Including TiO ₂ has the effect of suppressing formation defects of the glass film. The content of TiO ₂ is, for example, 0 to 10% by mass.
The annealing separator can be mixed with water to form a slurry and applied to the steel plate.

After winding into a coil, finish annealing is performed. For example, the temperature is raised to 1150 to 1250° C. in an atmospheric gas containing hydrogen and nitrogen, and the temperature is maintained in that temperature range for 10 to 60 hours.

(Insulating film formation process)
In the insulating film forming step, an insulating film (tension-applying insulating film) is formed on one or both sides of the cold-rolled sheet after finish annealing. The conditions for forming the insulating film are not particularly limited, and a known insulating film treatment liquid may be used to apply and dry the treatment liquid by a known method. By forming an insulating film on the surface of the steel sheet, it is possible to further improve the magnetic properties of the grain-oriented electrical steel sheet.
The surface of the steel plate on which the insulating film will be formed must have undergone any pretreatment such as degreasing with alkali or pickling with hydrochloric acid, sulfuric acid, phosphoric acid, etc. before applying the treatment solution. Alternatively, the surface may be as it is after finish annealing without being subjected to any of these pre-treatments.
The insulating film formed on the surface of the steel sheet is not particularly limited as long as it can be used as an insulating film for grain-oriented electrical steel sheets, and any known insulating film can be used. Examples of such an insulating film include a film containing phosphate and colloidal silica as main components. Further, a composite insulating film mainly composed of an inorganic substance and further containing an organic substance can be mentioned. Here, the composite insulating film is composed mainly of at least one of metal chromates, metal phosphates, or inorganic substances such as colloidal silica, Zr compounds, and Ti compounds, with fine organic resin particles dispersed therein. It is an insulating film. In particular, from the perspective of reducing the environmental impact during manufacturing, which has been an increasing need in recent years, insulating films using metal phosphates, Zr or Ti coupling agents, or carbonate or ammonium salts of these as starting materials are becoming more important. Sometimes used.

(Laser irradiation process)
In the laser irradiation process, a laser beam is irradiated onto a grain-oriented electrical steel sheet on which an insulating film has been formed to perform magnetic domain control. This allows the magnetic properties to be improved.
As the laser irradiation conditions, for example, the laser input energy Ua is 1.0 to 4.0 mJ/mm ² and the laser power density Ip is 500 to 4000 W/mm ² . Further, the laser beam is arranged so as to extend in a direction crossing the rolling direction (for example, at an angle of 60 to 120 degrees to the rolling direction) (preferably from one end in the width direction of the steel sheet to the other end). ) The steel plate is irradiated multiple times (preferably over the entire length of the steel sheet) so that the interval PL in the rolling direction is 3 to 10 mm and the respective irradiation directions are substantially parallel.
If Ua is less than 1.0 mJ/mm ² or Ip is less than 500 W/mm ² , a sufficient magnetic domain refining effect cannot be obtained. On the other hand, if Ua exceeds 4.0 mJ/mm ² or Ip exceeds 4000 W/mm ² , the noise characteristics deteriorate. This is thought to be due to the generation of many reflux magnetic domains. Ip is preferably 2000 W/mm ² or less.

Hereinafter, the grain-oriented electrical steel sheet according to the present invention will be specifically explained using Examples. The examples shown below are merely examples, and the grain-oriented electrical steel sheet according to the present invention is not limited to the examples below.

<Example 1>
C: 0.055%, Si: 0.86-3.15%, Mn: 0.14%, S: 0.007%, sol. A steel slab containing Al: 0.027%, Cr: 0.12%, N: 0.0075%, and the balance consisting of Fe and impurities was heated to 1150°C and then hot rolled to a plate thickness of 2.3 mm. It was made into a hot rolled sheet.
Next, this hot-rolled sheet was annealed. In hot-rolled sheet annealing, the sheet was heated to 1120°C and held for 180 seconds, then lowered to 900°C and held at that temperature for 120 seconds. Thereafter, it was rapidly cooled using hot water at 100°C.
Thereafter, after pickling, cold rolling was performed to obtain a cold rolled plate having a thickness of 0.23 mm.
Next, this cold-rolled sheet (steel sheet) was subjected to decarburization annealing in which the temperature was heated to the temperature listed in Table 1 in a wet hydrogen and nitrogen atmosphere and held for 150 seconds.
After decarburization annealing, the cold rolled sheet is heated to 750° C. in an atmosphere consisting of 25% N ₂ and 75% H ₂ with NH ₃ added, and held at that temperature for 30 seconds to form a steel sheet. A nitriding treatment was performed to increase the N content to 180 ppm.
After the nitriding treatment, a known annealing separator containing MgO and TiO ₂ as main components and containing Na, B, Cl, etc. was applied, and final annealing was performed at 1200° C. for 20 hours. At that time, spacers were placed between the steel plates at regular intervals so that the steel plates became wavy, and the steel plates were wound into a coil shape, and then finish annealing was performed. The diameter of the spacer (ceramic rod) and the spacing between the spacers were as shown in Table 1. After final annealing, a forsterite film was formed on the surface.
After finishing annealing, a coating liquid containing chromic anhydride and aluminum phosphate as main components is applied to the surface of this steel plate (a steel plate with a forsterite film formed on the surface of the base steel plate), and baking annealing is performed. , an insulating film was formed.
Thereafter, the surface of the steel plate on which the insulating film was formed was irradiated with a laser beam to perform magnetic domain refinement (magnetic domain control). At that time, the laser input energy and laser power density were as shown in Table 1. The scanning direction of the laser beam (the direction in which the irradiation marks extend) is 90° to the rolling direction, and the interval in the rolling direction between adjacent laser beam irradiation positions (the interval in the rolling direction of multiple linear strains) ) was set to 4 mm.

The steel sheet after magnetic domain control (grain-oriented electrical steel sheet) is subjected to the above-mentioned method to determine the chemical composition, the proportion of crystal grains with a distance between grain boundaries in the rolling direction of 3.0 to 13.0 mm, the area ratio of lancets, The width of the striped main magnetic domain, the magnetic properties (B8 and W17/50), and the value of LvA200Hz were determined. The magnetic domain observation at this time was performed in a demagnetized state. In addition, the average grain size in the rolling direction on the surface and the width of linear strains formed at 4 mm intervals in the rolling direction over the entire area of the steel plate (average of multiple linear strains) were also determined. .
The results are shown in Table 1.
The contents of each element are not shown in the table except for Si, but the C content is 0.014 to 0.055%, the S content is 0.001 to 0.007%, and sol. The Al content was 0.011 to 0.027%, and the N content was 0.0049 to 0.0075%. No major changes were observed in the Mn content and Cr content compared to the slab stage.

As can be seen from Table 1, in the example of the present invention, the area ratio of crystal grains on the surface of the base steel sheet where the distance between grain boundaries in the rolling direction is 3.0 mm or more and 13.0 mm or less is 70%. As above, B8, which is the magnetic flux density generated by a magnetizing force of 800 A/m, is 1.88 T or more, and W17/50 is 13.1×t ² −4.3×t+1. 2 or less, and LvA200Hz is 60 to 78 dBA. No fine grains were observed on the irradiation marks.
On the other hand, in the comparative example, one or more of the above points were outside the scope of the present invention, and iron loss and noise could not be sufficiently reduced at the same time.
For example, No. In No. 12, the decarburization annealing temperature is slightly low, and although the Ip is 1100 W/ ^mm2 , the average grain size is as small as 2.8 mm, and accordingly, the distance between grain boundaries of grains in the rolling direction is 3.0 mm or more. The area ratio of crystal grains having a diameter of 13.0 mm or less was small. In addition, B8 was low, iron loss was high, and LvA200Hz was high.
No. In No. 13, the decarburization annealing temperature is slightly high, the average grain size is as large as 20.2 mm, and accordingly, the area ratio of crystal grains in which the distance between the grain boundaries in the rolling direction is 3.0 mm or more and 13.0 mm or less is It was small. As a result, LvA200Hz was high.
No. In No. 16, the laser input energy Ua was relatively high at 4.1 mJ/mm ² , and as a result, the LvA of 200 Hz was high.
No. In No. 17 as well, the laser input energy Ua was relatively high at 4.4 mJ/mm ² , and as a result, the LvA of 200 Hz was high.
No. In No. 19, the diameter of the spacer and the interval between the spacers were not within the preferred range, so the average grain size was as large as 21.2 mm, and the distance between grain boundaries of grains in the rolling direction was 3.0 mm or more and 13.0 mm or less. The area ratio of crystal grains was small. As a result, LvA200Hz was high.
No. In No. 20, the laser power density Ip was as low as 200 W/m ² , and the area ratio of crystal grains in which the distance between grain boundaries in the rolling direction was 3.0 mm or more and 13.0 mm or less was small. As a result, iron loss was high.

<Example 2>
C: 0.070%, Si: 3.08-3.24%, Mn: 0.09%, S: 0.006%, sol. A steel slab containing Al: 0.026%, Cr: 0.11%, N: 0.0076%, with the remainder Fe and impurities was heated to 1140°C and hot rolled to a plate thickness of 2.4 mm. It was made into a hot rolled sheet.
Next, this hot-rolled sheet was annealed. In hot-rolled sheet annealing, the sheet was heated to 1120°C and held for 180 seconds, then lowered to 900°C and held at that temperature for 120 seconds. Thereafter, it was rapidly cooled using hot water at 100°C.
Thereafter, after pickling, cold rolling was performed to obtain a cold rolled plate having a thickness of 0.23 mm.
Next, this cold-rolled sheet (steel sheet) was subjected to decarburization annealing in which the temperature was heated to the temperature shown in Table 2 in a wet hydrogen and nitrogen atmosphere and held for 150 seconds.
After decarburization annealing, a known annealing separator containing MgO and TiO ₂ as main components and containing Na, B, Cl, etc. was applied, and final annealing was performed at 1200° C. for 20 hours. At that time, as shown in Figure 4, an annealing separator was distributed between the steel plates so that the thickness varied at regular intervals, the steel plates were wound into a coil, and final annealing was performed. . The annealing separator was applied in varying thicknesses so that the steel plate would have a wavy shape with wave height varying in the wave period (in the rolling direction) shown in Table 2. After final annealing, a forsterite film was formed on the surface.
After finish annealing, a coating liquid containing chromic anhydride and aluminum phosphate as main components is applied to the surface of this steel plate (a steel plate with a forsterite film formed on the surface of the base steel plate), and baking annealing is performed. An insulating film was formed.
Thereafter, the surface of the steel plate on which the insulating film was formed was irradiated with a laser beam to perform magnetic domain refinement (magnetic domain control). At that time, the laser input energy and laser power density were as shown in Table 2. The scanning direction of the laser beam (extending direction of the irradiation marks) was set at 90° with respect to the rolling direction, and the interval between adjacent laser beam irradiation positions in the rolling direction was 4 mm.

The steel sheet after magnetic domain control (grain-oriented electrical steel sheet) is subjected to the above-mentioned method to determine the chemical composition, the proportion of crystal grains with a distance between grain boundaries in the rolling direction of 3.0 to 13.0 mm, the area ratio of lancets, The width of the striped main magnetic domain, the magnetic properties (B8 and W17/50), and the value of LvA200Hz were determined. Magnetic domain observation was performed in a demagnetized state. In addition, the average grain size in the rolling direction on the surface and the width of a plurality of linear strains formed at 4 mm intervals in the rolling direction (average of a plurality of linear strains) were also determined.
The results are shown in Table 2.
The contents of each element other than Si are not shown in the table, but the C content is 0.016 to 0.070%, the S content is 0.001 to 0.006%, and the sol.Al content is , 0.010 to 0.026%, and the N content was 0.0051 to 0.0076%. No major changes were observed in the Mn content and Cr content compared to the slab stage.

As can be seen from Table 2, in the example of the present invention, the area ratio of crystal grains on the surface of the base steel plate, where the distance between grain boundaries in the rolling direction is 3.0 mm or more and 13.0 mm or less, is 70%. As above, B8, which is the magnetic flux density generated by a magnetizing force of 800 A/m, is 1.88 T or more, and W17/50 is 13.1×t ² −4.3×t+1. 2 or less, and LvA200Hz is 60 to 78 dBA. Here, the laser was irradiated transversely to the rolling direction of the steel plate, but no fine grains were generated on the irradiation marks.
On the other hand, in the comparative example, one or more of the above points were outside the scope of the present invention, and iron loss and noise could not be sufficiently reduced at the same time.
No. In No. 24, even if the decarburization annealing temperature is slightly low and the laser power density is within a preferable range, the area ratio of crystal grains in which the distance between the grain boundaries in the rolling direction is 3.0 mm or more and 13.0 mm or less is It was small. Furthermore, B8 was low, LvA200Hz was high, and W17/50 was high.
No. In No. 25, the decarburization annealing temperature was slightly high, the average grain size was large, and the area ratio of crystal grains with a distance between grain boundaries in the rolling direction of 3.0 to 13.0 mm was low. As a result, LvA200Hz was high. Also, W17/50 was high.
No. 26, No. In No. 27, the laser input energy was large, and as a result, the LvA of 200 Hz was high. Also, W17/50 was high.
No. In No. 28, the wave period was large, so the average grain size was large, and the area ratio of crystal grains in which the distance between grain boundaries in the rolling direction was 3.0 mm or more and 13.0 mm or less was small. As a result, LvA200Hz was high.

100 Lancet (reflux magnetic domain)
1 Steel plate 2 Spacer 3 Annealing separator L1 Spacer interval L2 Period h Wave height

Claims (5)

1. base material steel plate,
   a forsterite film formed on the surface of the base steel plate;
   an insulating film formed on the surface of the forsterite film;
   Equipped with
   The chemical composition of the base steel plate contains Si: 0.80 to 7.00% in mass %,
   The area ratio of crystal grains on the surface of the base material steel plate whose distance between grain boundaries in the rolling direction is 3.0 mm or more and 13.0 mm or less is 70% or more,
   B8, which is the magnetic flux density generated by a magnetizing force of 800 A/m, is 1.88 T or more,
   When the thickness of the base steel plate is expressed as t in mm, the iron loss W17/50 when the frequency is 50 Hz and the maximum magnetic flux density is 1.7 T is 13.1 x t in W/kg. ² -4.3×t+1.2 or less,
   LvA200Hz, which is the 200Hz component of the magnetostrictive waveform, is 60 to 78 dBA,
   A grain-oriented electrical steel sheet characterized by:
2. A plurality of linear strains extending in a direction intersecting the rolling direction are formed on the surface of the base steel plate, and an interval of the plurality of linear strains in the rolling direction is 3 to 10 mm.
   The grain-oriented electrical steel sheet according to claim 1, characterized in that:
3. In the base steel plate, the area ratio of strip-shaped reflux magnetic domains observed on the surface is 10% or less, and the width of the striped main magnetic domain is 1.2 mm or less,
   The grain-oriented electrical steel sheet according to claim 1 or 2, characterized in that:
4. When the magnetic flux density is 1.92T or more and the plate thickness is 0.18 to 0.23 mm, the W17/50 is 0.74 W/kg or less,
   The grain-oriented electrical steel sheet according to claim 1 or 2, characterized in that:
5. When the magnetic flux density is 1.92T or more and the plate thickness is 0.18 to 0.23 mm, the W17/50 is 0.74 W/kg or less,
   The grain-oriented electrical steel sheet according to claim 3, characterized in that:

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