JP4705382B2 - Unidirectional electrical steel sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a unidirectional electrical steel sheet excellent in iron loss characteristics subjected to magnetic domain control by laser irradiation and a method for manufacturing the same.

Unidirectional electrical steel sheets are required to reduce iron loss from the viewpoint of energy saving. As its method, as a method for producing a unidirectional electrical steel sheet in Patent Document 1, a method of reducing iron loss by introducing a linear strain substantially perpendicular to the rolling direction and periodically in the rolling direction by YAG laser irradiation. Is disclosed. The principle of this method called laser magnetic domain control is that the 180 ° domain wall interval is subdivided and iron loss is reduced due to surface distortion caused by laser beam scanning irradiation.
On the other hand, it is preferable to increase the thickness of the unidirectional electrical steel sheet in order to reduce the burden of the lamination work of the steel sheets in the product transformer manufacturing process. Therefore, a unidirectional electrical steel sheet with lower iron loss has been required even for thick materials.

Patent Document 2 discloses a manufacturing method that takes into account the plate thickness of a laser irradiation material. This discloses a method in which the integrated irradiation energy density and the laser power density on the scan line of the laser beam irradiation are changed according to the plate thickness, and the iron loss improvement is optimized at each plate thickness.
Japanese Patent Publication No. 6-19112 JP 2000-328139 A

Although the prior art discloses that the local integrated irradiation energy density and the laser power density are changed in accordance with the thickness of the unidirectional electrical steel sheet, the irradiation beam diameter is considered with respect to the thickness change. It was not constant.
An object of the present invention is to provide a unidirectional electrical steel sheet that obtains high iron loss improvement by changing the laser irradiation conditions according to the thickness of the unidirectional electrical steel sheet and a method for manufacturing the same.

  As a result of diligent research on low iron loss unidirectional electrical steel sheets subjected to magnetic domain control by laser irradiation, the inventors of the present invention have studied the shape of the reflux magnetic domain due to strain introduced by laser irradiation according to the plate thickness and the rolling of laser irradiation. By controlling the interval in the direction, the inventors have devised a unidirectional electrical steel sheet having a much lower iron loss than the conventional one and a manufacturing method capable of realizing it.

The gist of the present invention is described below.
(1) In a unidirectional electrical steel sheet in which distortion is induced by linearly irradiating a laser beam in the rolling direction in a line or a sequence of dots perpendicular to the rolling direction and performing magnetic domain control, the unidirectional electromagnetic steel The thickness of the steel sheet is t (mm), and the rolling direction width of the linear irradiation trace of the laser beam measured by observation with an optical microscope or the rolling direction width of the circulating magnetic domain generated by the laser beam irradiation is w (mm). ) and, when the irradiation interval in a rolling direction of irradiation before Symbol laser beam and PL (mm), that satisfy the following equation (provided that the land of the laser beam depressions formed by irradiation morphism or groove surface of the steel sheet If you Yusuke iron, and grain-oriented electrical steel sheet linear irradiation signatures laser beam is characterized.) except for the case of 0 <w ≦ 0.2 in steel sheet having a thickness of t = 0.23.
1.3 × 10 ⁻⁴ ≦ π / 8 × (w × w) / (t × PL) ≦ 1.3 × 10 ⁻²
(2) In a unidirectional electrical steel sheet in which distortion is introduced by linear irradiation of a laser beam periodically in the rolling direction and a magnetic domain control is performed in a linear or dot sequence perpendicular to the rolling direction. the thickness of the steel sheet and t (mm), the rolling direction width of the linear irradiation signatures of the laser beam measured by observation with an optical microscope, or the rolling direction width of the closure domains to be produced by the laser beam w (mm ) and, when the irradiation interval in a rolling direction of irradiation before Symbol laser beam and PL (mm), w is at 0.05mm or more and 0.2mm or less, to further satisfy the following equation (where the laser If you have a recess or groove formed in the irradiation morphism beam of the steel sheet surface in the base steel, and, in steel sheet having a thickness of t = 0.23 linear irradiation signatures of the laser beam is 0 <a w ≦ 0.2 Unidirectional electricity characterized by Steel plate.
7.0 × 10 ⁻⁴ ≦ π / 8 × (w × w) / (t × PL) ≦ 1.3 × 10 ⁻²

(3) In the method for producing a unidirectional electrical steel sheet in which a magnetic beam is controlled by introducing a strain in a linear shape or a point sequence perpendicular to the rolling direction and periodically irradiating a laser beam in the rolling direction. When the thickness of the magnetic steel sheet is t (mm), the condensing diameter of the laser beam in the rolling direction is dl (mm), and the irradiation interval in the rolling direction of the laser beam irradiation is PL (mm), satisfying the formula (However, if you have a form with the recess or groove in the irradiation morphism laser beam of the steel sheet surface in the base steel, and a linear irradiation signatures of the laser beam in steel sheet having a thickness of t = 0.23 method of manufacturing a grain-oriented electrical steel sheet but which is characterized in.) except for the case of 0 <w ≦ 0.2.
3.3 × 10 ⁻⁴ ≦ dl × dl / (t × PL) ≦ 3.3 × 10 ⁻²
(4) In the method for producing a unidirectional electrical steel sheet in which a magnetic beam is controlled by introducing a strain in a linear shape or a point sequence perpendicular to the rolling direction and periodically irradiating a laser beam in the rolling direction. When the thickness of the conductive electromagnetic steel sheet is t (mm), the condensing diameter in the rolling direction of the laser beam is dl (mm), and the irradiation interval in the rolling direction of the laser beam irradiation is PL (mm), dl was a 0.05mm or more and 0.2mm or less, further to satisfy the following equation (provided that if you have a recess or groove formed in the irradiation morphism laser beam of the steel sheet surface in the base steel, and plate thickness t = 0.23 steel sheet, except for the case where the linear irradiation trace of the laser beam is 0 <w ≦ 0.2).
1.8 × 10 ⁻³ ≦ dl × dl / (t × PL) ≦ 3.3 × 10 ⁻²
(5) The laser beam producing method of the grain-oriented electrical steel sheet according to (3) or (4), wherein the output from a continuous wave fiber laser device.

  According to the present invention, an electrical steel sheet having excellent iron loss characteristics can be obtained according to the thickness of the unidirectional electrical steel sheet. By using the unidirectional electrical steel sheet of the present invention, a highly efficient and small transformer can be manufactured with a low work load.

In the method of improving iron loss by introducing linear distortion at a constant interval by a laser on the surface of a unidirectional electrical steel sheet, a laser beam against a difference in sheet thickness is introduced. With regard to the irradiation conditions, in particular, focusing on the shape of the circulating magnetic domain, the distribution of the circulating magnetic domain, and the irradiation pitch, the present inventors have found a unidirectional electrical steel sheet with excellent iron loss characteristics that can be industrially realized and a method for manufacturing the same.
Hereinafter, the unidirectional electrical steel sheet and the manufacturing method thereof according to the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view of a laser beam irradiation method according to the present invention. In this example, the laser beam LB output from the laser device 3 was scanned and irradiated onto the unidirectional electrical steel sheet (steel sheet) 1 using the polygon mirror 4 and the fθ lens 5. The condensing diameter dl in the rolling direction of the laser beam was changed by changing the distance between the fθ lens 5 and the steel plate 1.
Reference numeral 6 denotes a cylindrical lens or a plurality of cylindrical group lenses, and a condensing shape from a circular shape to an elliptic shape is obtained by changing the condensing diameter (scan direction length) dc in the beam scanning direction of the condensing spot of the laser beam as necessary. Used to control. FIG. 1 shows an example of a set of a laser and a scanning device, but a plurality of similar devices may be arranged in the plate width direction according to the plate width of the steel plate.

  Using the continuous wave fiber laser apparatus having a fiber core diameter of 10 μm, the present inventors investigated the iron loss by irradiating the surface of the unidirectional electrical steel sheet having various thicknesses with a linear laser beam substantially perpendicular to the rolling direction. It was. In this experiment, irradiation traces may or may not occur on the surface of the steel sheet depending on the irradiation conditions of the laser irradiation. When an irradiation mark is generated, the width of the irradiation mark in the rolling direction is observed with an optical microscope, and the width of the circulating magnetic domain in the rolling direction generated by the irradiation is observed using reflected electrons of a scanning electron microscope having an acceleration voltage of 200 kV. Measured with As a result, the width of the irradiation mark and the width of the reflux magnetic domain were almost the same.

  When no irradiation mark was generated, the width of the reflux magnetic domain was measured. In the following description, the irradiation mark or the width of the reflux magnetic domain is treated as the same, and the irradiation width w (mm) in the rolling direction. FIGS. 4 and 5 show the results of examining the relationship between the rolling direction irradiation width w generated on the surface by laser irradiation and the iron loss and the relationship between the laser irradiation interval PL in the rolling direction and the iron loss in various thicknesses, respectively. The irradiation width w in the rolling direction was controlled by the laser irradiation beam diameter dl.

In order to reduce the iron loss, the average irradiation energy density Ua (mJ / mm ² ) and the plate width direction scanning speed Vc (m / s) of the laser beam in the plate width direction were changed under each condition. Ua (mJ / mm ² ) is PL (mm), Vc (m / s), and laser power is P (W), Ua (mJ / mm ² ) = P / (Vc × PL) Defined by The iron loss was measured for W _17/50 with an SST (Single Sheet Tester) measuring instrument. W _17/50 is the iron loss when the frequency is 50 Hz and the maximum magnetic flux density is 1.7 T.

In the unidirectional electrical steel sheet sample used in this example, when the plate thickness is _{0.23 mm} , the range of W _17/50 before laser irradiation is 0.80 to 0.85 W / kg, and the plate thickness is 0. In the case of 27 mm, the range of W _17/50 before laser irradiation is 0.80 to _0.90 W / kg, and when the plate thickness is 0.30 mm, the range of W _17/50 before laser irradiation is It was 0.95-1.00 W / kg.

As shown in FIG. 4, from the measurement results of the rolling direction irradiation width w and the iron loss at the sheet thickness t, it was found that the optimum rolling direction irradiation width w increases as t increases. The present inventors consider the reason as follows.
As shown in FIG. 6, generally, the strain introduced by laser irradiation is considered to be isotropically distributed concentrically starting from the surface irradiation portion, and its depth is estimated to be about half of the irradiation width w in the rolling direction. The When w is constant, since the proportion of the depth of distortion introduced by laser irradiation decreases as the plate thickness increases, the irradiation width w in the rolling direction is set to obtain the magnetic domain fragmentation effect when the plate thickness is large. It is considered effective to increase the distortion in the depth direction by increasing the width.

  On the other hand, as shown in FIG. 5, the iron loss is minimized when the plate thickness t is increased from the measurement result of the relationship between the interval (rolling direction pitch) PL of the laser beam irradiation in the plate thickness t and the iron loss. It has been found that the interval of the rolling direction pitch PL becomes smaller. Considering this result, it is considered that when PL is constant, the interaction between linear strains in the rolling direction becomes weaker as the plate thickness increases. In other words, it is considered that the irradiation interval needs to be narrowed in order to obtain the magnetic domain refinement effect.

  From the above two experimental results and considerations, the present inventors have found that the magnetic domain refinement effect for reducing the iron loss depends on the thickness t, the irradiation width w in the rolling direction, that is, the amount of strain and the interaction between the irradiation interval PL, that is, strain. I thought it was closely related to size. In other words, we hypothesized that there is an optimal value for the amount and distribution of the circulating magnetic domains that are approximately proportional to the amount of strain corresponding to the plate thickness. That is, it was considered that there exists an optimum range in the ratio of the plate thickness t × the interval PL and the strain area π / 8 × (w × w) as a constant cross-sectional area as shown in FIG. In order to confirm the truth of this hypothesis, the following experiment and analysis were further performed.

The ratio of the area of strain in the cross section in the rolling direction of the steel sheet (hereinafter referred to as strain ratio η) is defined as π / × (w × w) / (t × PL), and the strain ratio η The result of investigating the relationship of iron loss W _17/50 is shown in FIG. In FIG. 2, when the deterioration rate with respect to the minimum iron loss at each plate thickness indicated by the dotted line is defined as (final iron loss−minimum iron loss) / minimum iron loss × 100%, at any plate thickness In addition, when the strain ratio η is 1.3 × 10 ⁻⁴ or more and 1.3 × 10 ⁻² or less shown by a dotted line, a deterioration rate of 5% or less shown by a one-dot chain line can be realized.

When the strain ratio η is less than 1.3 × 10 ⁻⁴ , this mainly corresponds to the irradiation condition where w is very small and the PL is wide, and the domain fragmentation hardly occurs because the interaction of the linear strain is weak. Iron loss is not reduced. On the other hand, when the strain ratio η is greater than 1.3 × 10 ⁻² , this corresponds to the irradiation condition where w is very large and the PL is narrow, and the individual linear strain is excessive. The iron loss is not reduced because the hysteresis loss increases.

FIG. 3 shows iron loss according to irradiation width w in the rolling direction of FIG. From this, in order to obtain a unidirectional electrical steel sheet having a deterioration rate of 4% or less indicated by a two-dot chain line in the figure with smaller iron loss, the irradiation width w in the rolling direction is 0.05 mm or more and 0.2 mm or less, and the strain ratio It is desirable that η is in a range of 7.0 × 10 ⁻⁴ or more and 1.3 × 10 ⁻² or less indicated by a dotted line.

The rolling direction irradiation width w substantially matches the rolling direction diameter dl of the focused laser beam. Therefore, in the method for producing a unidirectional electrical steel sheet of the present invention, w in the strain ratio η = π / 8 × (w × w) / (t × PL) is replaced with dl, and dl × dl / (t × PL). Is within the range of 3.3 × 10 ⁻⁴ or more and 3.3 × 10 ⁻² or less, a unidirectional electrical steel sheet having excellent iron loss characteristics can be produced.
Preferably, dl is 0.05 mm or more and 0.2 mm or less, and dl × dl / (t × PL) is 1.8 × 10 ⁻³ or more and 3.3 × 10 ⁻² or less.
The unidirectional electrical steel sheet obtained by this irradiation method has a small iron loss as compared with Patent Document 2 of the prior art in which dl is 0.2 mm or more.
According to the present invention, since the unidirectional electrical steel sheet having excellent iron loss characteristics at various plate thicknesses can be obtained, the industrial significance of the present invention is extremely large.

It is a schematic diagram of the apparatus used for the unidirectional electrical steel sheet manufacturing method of this invention. It is a related figure of distortion ratio eta = pi / _8x ( _wxw ) / ( _txPL ) in various board thickness, and iron loss _W17 / ₅₀ . FIG. _{5 is} a relationship diagram of strain ratios η = π / 8 × (w × w) / (t × PL) and iron loss W _17/50 in various plate thicknesses, and is a relationship diagram shown for each irradiation width w in the rolling direction. It is a related figure of the rolling direction irradiation width w and iron loss _{W17 / 50} in various board thickness (irradiation pitch is fixed 4 mm). It is a related figure of irradiation pitch PL and iron loss _{W17 / 50} in various board thickness (rolling direction irradiation width w is fixed to 0.1 mm). It is a schematic diagram explaining distortion ratio (eta).

Explanation of symbols

1: Electromagnetic steel plate 2: Laser irradiation trace 3: Laser device 4: Scanning mirror, polygon mirror 5: Condensing lens, fθ lens 6: Cylindrical lens, assembled cylindrical lens LB: Laser beam P: Laser power Vc: Scan in the plate width direction Speed PL: Rolling direction irradiation pitch w: Rolling direction irradiation width dl: Condensing diameter in the rolling direction of the laser beam dc: Condensing diameter in the scanning direction of the laser beam

Claims (5)

In a unidirectional electrical steel sheet that has been subjected to magnetic domain control by irradiating laser beams periodically in the rolling direction and introducing a strain in a line perpendicular to the rolling direction or in a sequence of dots, the plate of the unidirectional electrical steel sheet the thickness and t (mm), the rolling direction width of the linear irradiation signatures of the laser beam measured by observation with an optical microscope, or, the rolling direction width of the closure domains generated by irradiation of the laser beam w (mm) and then, when the irradiation interval in a rolling direction of irradiation before Symbol laser beam and PL (mm), that satisfy the following equation (where the indentations or grooves formed in the irradiation morphism laser beam surface of the steel sheet base iron If you Yusuke in, and, grain-oriented electrical steel sheet linear irradiation signatures laser beam is characterized.) except for the case of 0 <w ≦ 0.2 in steel sheet having a thickness of t = 0.23.
1.3 × 10 ⁻⁴ ≦ π / 8 × (w × w) / (t × PL) ≦ 1.3 × 10 ⁻² In a unidirectional electrical steel sheet that has been subjected to magnetic domain control by irradiating laser beams periodically in the rolling direction and introducing a strain in a line perpendicular to the rolling direction or in a sequence of dots, the plate of the unidirectional electrical steel sheet The thickness is t (mm) , the width in the rolling direction of the linear irradiation trace of the laser beam measured by observation with an optical microscope , or the width in the rolling direction of the circulating magnetic domain generated by the laser beam is w (mm) , when the irradiation interval in a rolling direction of irradiation before Symbol laser beam and PL (mm), w is at 0.05mm or more and 0.2mm or less, further to satisfy the following equation (where the laser beam irradiation If you have a form with the recess or groove in elevation of the steel sheet surface in the base steel, and, unless the linear irradiation signatures of laser beam is 0 <w ≦ 0.2 in steel sheet having a thickness of t = 0.23 .) Unidirectional electrical steel sheet characterized by
7.0 × 10 ⁻⁴ ≦ π / 8 × (w × w) / (t × PL) ≦ 1.3 × 10 ⁻² In a method for producing a unidirectional electrical steel sheet, in which a linear or point sequence perpendicular to the rolling direction and a laser beam are periodically irradiated in the rolling direction to introduce strain and perform magnetic domain control, the unidirectional electrical steel sheet When the plate thickness of the laser beam is t (mm), the condensing diameter of the laser beam in the rolling direction is dl (mm), and the irradiation interval in the rolling direction of the laser beam irradiation is PL (mm), the following equation is satisfied: be (although, if you have a form with the recess or groove in the irradiation morphism laser beam of the steel sheet surface in the base steel, and a linear irradiation signatures of the laser beam in steel sheet having a thickness of t = 0.23 is 0 < (except for the case of w ≦ 0.2).
3.3 × 10 ⁻⁴ ≦ dl × dl / (t × PL) ≦ 3.3 × 10 ⁻² In a method for producing a unidirectional electrical steel sheet, in which a linear or point sequence perpendicular to the rolling direction and a laser beam are periodically irradiated in the rolling direction to introduce strain and perform magnetic domain control, the unidirectional electrical steel sheet When the plate thickness of the laser beam is t (mm), the condensing diameter of the laser beam in the rolling direction is dl (mm), and the irradiation interval in the rolling direction of the laser beam irradiation is PL (mm), dl is 0. and a 0.2mm inclusive 05Mm, further satisfying the following equation (provided that if you have a recess or groove formed in the irradiation morphism laser beam of the steel sheet surface in the base steel, and plate thickness t = 0. 23). A method for producing a unidirectional electrical steel sheet, characterized in that the number of laser beam linear irradiation traces is 23 in the case of 0 <w ≦ 0.2.
1.8 × 10 ⁻³ ≦ dl × dl / (t × PL) ≦ 3.3 × 10 ⁻²   The said laser beam is output from a continuous wave fiber laser apparatus, The manufacturing method of the unidirectional electrical steel sheet of Claim 3 or Claim 4 characterized by the above-mentioned.

Images