JP2012140665A - Method for manufacturing grain-oriented electromagnetic steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a magnetic domain refinement effect and a tension-imparting effect can be enjoyed more than enough by solving the problem of noise in the case of using, for a transformer, a grain-oriented electromagnetic steel sheet into which thermal strain is introduced.SOLUTION: When the grain-oriented electromagnetic steel sheet wound in a coiled form is subjected to magnetic domain refinement treatment which includes, in order, subjecting the steel sheet to final annealing; forming a tension-insulating film and subjecting the steel sheet to flattening annealing; and introducing a thermal strain region in a direction crossing a rolling direction of the steel sheet, the steel sheet after the flattening annealing is given a curve in which a bus line has a direction crossing the rolling direction, and the thermal strain region is introduced into the internal surface of the curve.

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet, and more particularly to a method for improving iron loss by subjecting a grain-oriented electrical steel sheet to a magnetic domain refinement process.

The grain-oriented electrical steel sheet is mainly used as an iron core of a transformer and is required to have excellent magnetization characteristics, particularly low iron loss.
For this purpose, it is important to highly align the secondary recrystallized grains in the steel sheet in the (110) [001] orientation (so-called Goth orientation) and to reduce impurities in the product steel sheet. However, controlling the crystal orientation and reducing impurities are limited in view of the manufacturing cost. Therefore, a technique for reducing the iron loss by introducing non-uniformity to the surface of the steel sheet by a physical method and subdividing the width of the magnetic domain, that is, a magnetic domain subdivision technique has been developed.

  For example, Patent Document 1 reduces the iron loss of a steel sheet by irradiating the final product plate with a laser, introducing a linear high dislocation density region (thermal strain region) into the steel sheet surface layer, and narrowing the magnetic domain width. Techniques to do this have been proposed. Further, Patent Document 2 discloses a method of introducing a linear high dislocation density region by radiating a plasma flame on the steel plate surface, and Patent Document 3 discloses a linear high dislocation density region by irradiating the steel plate surface with an electron beam. Each method has been proposed.

Japanese Patent Publication No.57-2252 JP-A 62-96617 JP-A-1-281708

  While the magnetic domain fragmentation treatment by introducing the thermal strain region described above can obtain a high magnetic domain fragmentation effect, noise is not generated when the grain-oriented electrical steel sheet into which such local thermal strain is introduced is used as a transformer. The problem of becoming larger can arise. These are particularly prominent when the amount of heat (strain) applied to the steel sheet is increased in an attempt to reduce the iron loss to the limit. This is because there are many fine and complicated auxiliary magnetic domains that occur in the thermal strain region and the region where the elastic strain is introduced in the surrounding area, and when such a large amount of auxiliary magnetic domains are used in the iron core of the transformer. This is to increase and complicate magnetostriction fluctuations in the magnetization process.

  Therefore, the present invention eliminates the problem of noise when the grain-oriented electrical steel sheet with such thermal strain introduced is used in a transformer, and can fully enjoy the magnetic domain fragmentation effect and the tension application effect. It aims to provide about.

  In order to solve the above-mentioned problems, the inventors diligently studied a method for introducing thermal strain. In addition, it has been found that it is extremely effective to introduce linear thermal strain, and the present invention has been completed.

That is, the gist configuration of the present invention is as follows.
A directionally-oriented electrical steel sheet wound in a coil shape is subjected to finish annealing, followed by formation of a tensile insulating coating and flattening annealing, and then a linear thermal strain region is introduced in a direction crossing the rolling direction of the steel sheet. In performing the magnetic domain refinement treatment, the steel plate after the flattening annealing is given a curve in which the bus bar intersects with the rolling direction, and the thermal strain region is introduced into the inner surface of the curve. A method for producing a grain-oriented electrical steel sheet.

  According to the present invention, when introducing thermal strain into the steel sheet, with a simple method of curving the steel sheet along the rolling direction with the surface to introduce thermal strain inside, reduction of transformer iron loss, It is possible to manufacture a grain-oriented electrical steel sheet that is compatible with noise reduction when used as an iron core of a transformer.

It is a figure which shows the point of the thermal strain introduction according to this invention. It is a figure which shows the specific example of thermal strain introduction. It is a figure which shows the specific example of thermal strain introduction. It is a figure which shows the specific example of thermal strain introduction. It is a figure which shows the point of the conventional thermal strain introduction.

Hereinafter, the method of the present invention will be described in detail.
In the present invention, the directional electrical steel sheet wound up in a coil shape is subjected to finish annealing, and then the coil steel sheet is flattened by removing the coil curl by flattening annealing, and then, as shown in FIG. A curve in which the bus bar intersects with the rolling direction of the steel sheet is given to the inner surface 2 of the curve, and a linear thermal strain region is introduced by an energy beam 3 such as a laser or an electron beam.

Here, when the steel plate 1 is curved, in the case of a continuous coil, it is possible to take a method such as winding around a roll or guide plate through which the energy beam 3 is transmitted, or following a guide roll having a small interval. In the case of a cut plate, a method such as pressing against a guide having a predetermined curvature can be taken.
That is, as the guide roll through which the energy beam 3 is transmitted, the steel sheet 1 can be wound around the roll 4 by using, for example, a guide roll 4 that transmits the laser light 3b from the oscillator 3a as shown in FIG. In addition, as a guide roll which permeate | transmits a laser beam, what uses glass, resin, etc. which have a high transmittance | permeability with respect to the wavelength of the laser beam to irradiate is applicable.
As a guide plate through which the energy beam 3 passes, for example, a slit (or window) 5a for passing the energy beam 3 is provided in the guide plate 5 as shown in FIG. 3, and the energy beam 3 passes through such a gap. It is possible to make it.
Furthermore, when using guide rolls arranged at a small interval, for example, as shown in FIG. 4, when guiding the steel sheet 1 while curving the steel sheet 1 by arranging a large number of small-diameter rolls 6, gaps between the rolls 6 are formed. It is also possible to irradiate the steel plate 1 with the energy beam 3.

  Note that the preferred range of the curvature radius of the curve when bending is different depending on the thickness of the target steel plate, but is generally not less than 200 times and not more than 2000 times the plate thickness. That is, if the radius of curvature is smaller than 200 times the plate thickness, the warpage of the steel plate due to bending remains even after the introduction of thermal strain, making it difficult to process the transformer. On the other hand, when it exceeds 2000 times, the effect of bending described later is reduced.

  In addition, it is important that the curve be given in a direction in which the bus bar intersects the rolling direction. In particular, it is preferable to provide a curve in which the generatrix of the curved surface is orthogonal to the rolling direction, but the angle α (see FIG. 1B) formed by the generatrix of the curved surface with respect to the direction perpendicular to the rolling is within 45 °. I just need it.

When the steel sheet is subjected to the above-described curve, the generatrix direction of the curved surface and the direction in which the thermal strain is linearly introduced are substantially parallel. The reason why noise is reduced when a steel plate that has undergone such a process is applied to a transformer by introducing thermal distortion into a linear shape by giving this curvature is not clear, but it is considered as follows. .
In other words, compressive stress is acting on the inner surface of the curved steel sheet, and as a result, distortion caused by thermal expansion of the steel sheet due to instantaneous heating is generated with a smaller amount of heat input. As a result of the reduction in the total amount of necessary thermal strain, it is presumed that the amount of auxiliary magnetic domains formed is also reduced, and the amount of change in magnetostriction during magnetization of the transformer core is reduced. Therefore, it is considered effective that the generatrix direction of the curved surface and the direction in which the thermal strain is linearly introduced are substantially parallel.

  Here, the introduction of the thermal strain needs to be after the finish annealing and the formation of the tension insulating coating. Heat treatment at a high temperature is necessary for finish annealing for growing goth-oriented secondary recrystallization, which is a characteristic of grain-oriented electrical steel sheets, and for formation of a tensile insulating film and manifestation of a tension effect. However, since such high-temperature treatment removes or reduces the strain introduced into the steel sheet, for example, if the tension coating is baked after the introduction of thermal strain, the compressive stress due to the introduced strain is eliminated, and the effect of magnetic domain subdivision is eliminated. Disappears. Therefore, high-temperature treatment such as formation of a tension coating must be performed before the introduction of thermal strain in the present invention.

As a method for introducing thermal strain, a known method such as pulse oscillation such as YAG laser, CO ₂ laser, or fiber laser, or continuous oscillation, electron beam irradiation, plasma flame irradiation, or the like can be employed. The thermal strain is introduced linearly in a direction intersecting with the rolling direction, preferably in a direction perpendicular to the rolling direction, but may be continuous linear or dotted. This linear strain introduction region is formed repeatedly at intervals of 2 mm or more and 20 mm or less in the rolling direction.
In addition, it is suitable for the depth of the distortion introduce | transduced into a steel plate to be about 5-30 micrometers.

Further, it is known that the iron loss of the grain-oriented electrical steel sheet subjected to the magnetic domain refinement treatment is smaller when the orientation accumulation of secondary recrystallization is higher. B ₈ (magnetic flux density when magnetized at 800 A / m) is often used as a measure of orientation accumulation, but the grain-oriented electrical steel sheet used in the present invention has a B ₈ of 1.88 T or more, more preferably 1.92 T or more. Is preferred.
Such a grain-oriented electrical steel sheet with a high magnetic flux density has a small magnetostriction, which is advantageous for reducing the noise of the transformer. In the present invention, thermal strain can be introduced at a lower output than before, and as a result, changes in magnetostriction due to thermal strain can be suppressed, and noise can be reduced by utilizing the low magnetostriction of the material.

The tension insulation coating formed on the surface of the electrical steel sheet may be a conventionally known tension insulation coating, but it is a glassy tension insulation coating mainly composed of a phosphate such as aluminum phosphate or magnesium phosphate and silica. Preferably there is.
The tension coating baking and the flattening annealing may be performed simultaneously or separately.

The grain-oriented electrical steel sheet according to the present invention may be a conventionally known grain-oriented electrical steel sheet. For example, an electromagnetic steel material containing Si: 2.0 to 8.0% by mass may be used.
Si: 2.0 to 8.0 mass%
Si is an element effective in increasing the electrical resistance of steel and improving iron loss. However, if the content is less than 2.0% by mass, a sufficient iron loss reduction effect cannot be achieved, while 8.0% by mass. If it exceeds 1, the workability is remarkably lowered and the magnetic flux density is also lowered. Therefore, the Si content is preferably in the range of 2.0 to 8.0% by mass.

Further, other basic components and optional addition components of Si will be described as follows.
C: 0.08% by mass or less C is added to improve the texture. However, if it exceeds 0.08% by mass, it is difficult to reduce C to 50 ppm by mass or less at which no magnetic aging occurs during the manufacturing process. Therefore, the content is preferably 0.08% by mass or less. In addition, regarding the lower limit, since a secondary recrystallization is possible even for a material not containing C, it is not particularly necessary to provide it.

Mn: 0.005 to 1.0 mass%
Mn is an element necessary for improving the hot workability. However, if the content is less than 0.005% by mass, the effect of addition is poor, whereas if it exceeds 1.0% by mass, the magnetic flux density of the product plate decreases. The amount of Mn is preferably in the range of 0.005 to 1.0 mass%.

  Here, when an inhibitor is used to cause secondary recrystallization, for example, Al and N are used when an AlN inhibitor is used, and Mn is used when an MnS / MnSe inhibitor is used. An appropriate amount of Se and / or S may be contained. Of course, both inhibitors may be used in combination. The preferred contents of Al, N, S and Se in this case are Al: 0.01 to 0.065 mass%, N: 0.005 to 0.012 mass%, S: 0.005 to 0.03 mass% and Se: 0.005 to 0.03 mass%, respectively. .

Furthermore, the present invention can also be applied to grain-oriented electrical steel sheets in which the contents of Al, N, S, and Se are limited and no inhibitor is used.
In this case, the amounts of Al, N, S and Se are preferably suppressed to Al: 100 mass ppm or less, N: 50 mass ppm or less, S: 50 mass ppm or less, and Se: 50 mass ppm or less, respectively.

In addition to the above basic components, the following elements can be appropriately contained as magnetic property improving components.
Ni: 0.03-1.50% by mass, Sn: 0.01-1.50% by mass, Sb: 0.005-1.50% by mass, Cu: 0.03-3.0% by mass, P: 0.03-0.50% by mass, Mo: 0.005-0.10% by mass and Cr: At least one selected from 0.03 to 1.50 mass%
Ni is an element useful for improving the magnetic properties by improving the hot-rolled sheet structure. However, if the content is less than 0.03% by mass, the effect of improving the magnetic properties is small. On the other hand, if the content exceeds 1.5% by mass, the secondary recrystallization becomes unstable and the magnetic properties deteriorate. Therefore, the amount of Ni is preferably in the range of 0.03 to 1.5 mass%.

Sn, Sb, Cu, P, Cr and Mo are elements useful for improving the magnetic properties, respectively, but if any of them is less than the lower limit of each component described above, the effect of improving the magnetic properties is small. If the upper limit amount of each component described above is exceeded, the development of secondary recrystallized grains is hindered.
The balance other than the above components is inevitable impurities and Fe mixed in the manufacturing process.

  The steel slab having the component composition described above is a grain oriented electrical steel sheet in which a tensile insulating coating is formed after secondary recrystallization annealing through a process generally following that of grain oriented electrical steel sheets. That is, hot rolling is performed after slab heating, and the final sheet thickness is obtained by one or two cold rollings with intermediate annealing, followed by decarburization and primary recrystallization annealing, and then, for example, MgO as a main component. Apply an annealing separator, apply final finishing annealing including secondary recrystallization process and purification process, perform the above operation, and apply and baked with an insulating coat made of colloidal silica and magnesium phosphate, for example .

The directional electrical steel sheet coil (plate thickness: 0.23 mm) after final finish annealing was applied with flattening annealing and at the same time applied and baked. The grain-oriented electrical steel sheet contains 3.4% by mass of Si, and the tension insulating coating is obtained by baking a chemical solution composed of colloidal silica, magnesium phosphate, and chromic acid formed on the forsterite coating. . A sample having a width of 100 mm and a length of 500 mm with the rolling direction as the longitudinal direction was taken from this coil, and the magnetic properties were measured with a single-plate magnetometer. Iron loss at excitation conditions of 1.7 T and 50 Hz of this grain-oriented electrical steel sheet was measured. W _17/50 was 0.90 W / kg, and the magnetic flux density B _{8 at a} magnetizing force of 800 A / m was 1.93 T.

Next, this sample was subjected to a magnetic domain fragmentation treatment in which a pulse laser or an electron beam was irradiated. At this time, a stainless steel plate is prepared as a guide in which the cut plate is curved with a predetermined radius of curvature along the longitudinal direction, the sample is fixed along the stainless steel plate to give a curve, and as shown in FIG. The laser or electron beam was set in the irradiation device so that the inner surface of the curved portion was irradiated. Further, some samples were irradiated with an energy beam (laser or electron beam) 3 in a flat state (no curvature) as shown in FIG.
That is, irradiation was performed by changing the output of the laser or electron beam, and the conditions were confirmed that the iron loss was sufficiently reduced to 0.78 W / kg, and 500 sheets were processed under each condition. The irradiation conditions of the pulse laser and the electron beam are as shown in the margin of Table 1. Here, the output of the laser or electron beam is shown in terms of the amount of heat per 1 cm of the steel sheet surface.

In addition, these cut plates are bevel cut so that they become members of a three-phase, three-legged model transformer, and an iron core is constructed by laminating 100 sheets in an alternating stack with a wrap width of 10mm, at 1.7T and 50Hz. The iron loss and the noise at that time (measured at 300mm from the iron core) were measured.
As shown in Table 1, the results of these measurements are shown in Table 1. When the material that has been subjected to magnetic domain refinement treatment according to the present invention is used as an iron core, compared to a material that has been subjected to magnetic domain refinement treatment in a flat state as in the prior art. The noise was reduced by about 2 dB or more.

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Inner side surface 3 Energy beam 3a Oscillator 3b Laser beam 4 Guide roll 5 Guide plate 5a Slit 6 Roll

Claims (1)

A directionally-oriented electrical steel sheet wound in a coil shape is subjected to finish annealing, followed by formation of a tensile insulating coating and flattening annealing, and then a linear thermal strain region is introduced in a direction crossing the rolling direction of the steel sheet. In performing the magnetic domain refinement treatment, the steel plate after the flattening annealing is given a curve in which the bus bar intersects with the rolling direction, and the thermal strain region is introduced into the inner surface of the curve. A method for producing a grain-oriented electrical steel sheet.

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