JP2002294416A - Grain-oriented electro magnetic steel sheet with low core loss, and manufacturing method and manufacturing apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a grain-oriented electromagnetic steel sheet with reduced core loss and magnetostriction. SOLUTION: The grain-oriented electromagnetic steel sheet with low core loss has linear or discontinuously linear grooves in an approximately transverse direction against a rolling direction, and has secondary recrystallized grain boundaries penetrating through the sheet thickness under parts of 15% or more and 90% or less of the total groove length. The manufacturing method includes heating the sheet to a recrystallization temperature after a final cold rolling, forming the linear or discontinuously linear grooves in the approximately transverse direction against the rolling direction by machining, and then annealing it for the purpose of secondary recrystallization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet used for a static induction machine such as a transformer, which has a reduced iron loss, and a method and an apparatus for manufacturing the same.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used for stationary inductors typified by transformers. The characteristics to be satisfied are that the energy loss, that is, iron loss, when excited by alternating current is small, that the permeability is high in the used excitation range of the equipment and that it can be easily excited, and that the magnetostriction that causes noise is small. Can be In particular, since the transformer is continuously excited for a long period of time from installation to disposal and continues to generate energy loss, T.P. is an index indicating the value of the transformer. O.
C. (Total Owning Cost).

In order to reduce the iron loss of the grain-oriented electrical steel sheet, many developments have been made so far. That is,
Increasing the integration in the (110) [001] orientation called the Goss orientation, increasing the content of solid solution elements such as Si, which increase the electrical resistance, reducing the thickness of the steel sheet, and ceramics that give surface tension to the steel sheet For example, providing a film or an insulating film, and reducing the size of crystal grains.
However, there is a limit to iron loss improvement by these metallurgical methods, and reduction of iron loss by other methods has been required.

In response to this problem, A. Fiedler, W. Pepperho
f proposes a method of reducing iron loss by forming a groove on the surface of a grain-oriented electrical steel sheet with a cutter or the like and changing the magnetic domain structure (US Pat. No. 3,646,575). A grain-oriented electrical steel sheet generally has a magnetic domain structure in which slab-shaped magnetic domains having magnetization components in mutually opposite directions are alternately arranged, and these domains are magnetized by expanding / reducing under an external magnetic field. Therefore, when the grain-oriented electrical steel sheet is magnetized,
Magnetization change occurs only at the boundary (domain wall) between adjacent magnetic domains. An eddy current flows in the steel sheet with this change in magnetization,
It accounts for 60 to 70% of the causes of iron loss described above (eddy current loss). The eddy current loss is proportional to the square of the eddy current, and the eddy current is proportional to the moving speed of the domain wall. When the magnetic domain width is reduced, the number of sites where eddy currents are generated increases, but the moving speed of the domain wall decreases in inverse proportion to the magnetic domain width. As a result, the eddy current loss decreases substantially in proportion to the magnetic domain width.

[0005] Various proposals have been made to make this magnetic domain segmentation technique industrially applicable. For example, as disclosed in Japanese Patent Publication No. 58-5968, a method in which a small ball having a diameter of 0.2 to 10 mm is rotated while being pressed against the surface of a steel sheet to introduce distortion without scratching the surface.
No. 252, a method of applying a small plastic strain by irradiating a laser beam in a direction substantially perpendicular to the rolling direction, as disclosed in Japanese Patent Application Laid-Open No. Sho 62-96617, to generate a plasma flame in a direction substantially perpendicular to the rolling direction. There is a method of emitting light linearly. All of these are techniques for introducing fine plastic strain into a steel sheet and subdividing magnetic domains using magnetic domains having a magnetization component perpendicular to the rolling direction stabilized by the reverse effect of magnetostriction. The effect was lost due to the strain relief annealing at the time of manufacturing.

In addition, a heat-resistant magnetic domain refining method which does not lose its effect even by strain relief annealing has been studied with respect to these magnetic domain refining methods. For example, after finish annealing as disclosed in Japanese Patent Publication No. 63-48404. The steel plate is formed with a gear-shaped roll to form a linear, dotted or dashed concave portion.
A method of generating fine crystal grains by heat treatment at 0 ° C. or higher,
Alternatively, a method of forming a groove on the surface of a steel sheet by photo-etching as disclosed in Japanese Patent Publication No. 5-69284, and a method of forming a groove by baking a resist film by gravure printing and electrolytic corrosion as disclosed in Japanese Patent Publication No. 8-6140. A method of doing so has been proposed. These methods reduce the increase in magnetostatic energy due to the magnetic poles generated in the grooves / fine crystal grains.
The basic principle is to compensate by reducing the width of the slab-shaped magnetic domain, and the effect is not lost by the strain relief annealing.

[0007]

As described above, iron loss of grain-oriented electrical steel sheets has been remarkably improved.
Energy consumption is increasing due to industrialization, and concerns about depletion of fossil energy resources and demand for global warming due to CO ₂ require further reduction of iron loss. In addition, substation facilities are being built in urban areas, and there is a need to reduce noise generated by transformers.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a low iron loss grain-oriented electrical steel sheet using groove formation on the surface of the steel sheet, and as a result, selectively formed secondary recrystallized grain boundaries below the groove. It has been found that by forming, a grain-oriented electrical steel sheet with extremely low iron loss and low noise is manufactured. That is, the gist of the present invention has the following configuration.

(1) A linear groove is formed in a direction substantially perpendicular to the rolling direction, and a secondary recrystallized grain boundary is present in a portion of 15% or more and 90% or less of the length of the groove. Low iron loss oriented magnetic steel sheet. (2) After the grain-oriented electrical steel sheet is finally cold-rolled and heated to the recrystallization temperature, a linear groove is formed by machining in a direction substantially perpendicular to the rolling direction, and then subjected to secondary recrystallization annealing. A method for producing a low iron loss grain-oriented electrical steel sheet, wherein a secondary recrystallized grain boundary is present in a portion of 15% or more and 90% or less in length of a linear groove. (3) The method for producing a low iron loss grain-oriented electrical steel sheet according to the above (2), wherein decarburization is performed by annealing in wet hydrogen before mechanical recrystallization annealing after machining. (4) The method for producing a low iron loss grain-oriented electrical steel sheet according to (2) or (3), wherein the heating method up to the recrystallization temperature is electric heating or induction heating. (5) In the manufacturing process of grain-oriented electrical steel sheets, a heating device for heating the cold-rolled sheet to the recrystallization temperature after the final cold-rolling, and machining linear or discontinuous linear grooves in a direction substantially perpendicular to the rolling direction. An apparatus for manufacturing a grain-oriented electrical steel sheet having a low iron loss, wherein a groove forming apparatus formed by the method is incorporated. (6) The apparatus for producing a low iron loss grain-oriented electrical steel sheet according to the above (5), wherein the heating by the heating device is electric heating or induction heating. (7) The apparatus for producing a low iron loss grain-oriented electrical steel sheet according to (5), wherein the heating device and the groove forming device are incorporated in an annealing device for decarburization in wet hydrogen. (8) The apparatus for producing a low iron loss grain-oriented electrical steel sheet according to the above (7), wherein the heating up to the recrystallization temperature is electric heating or induction heating.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
% Si and a cold-rolled sheet (sheet thickness 0.23 mm) of a grain-oriented electrical steel sheet containing MnS and AlN as inhibitor components,
After mechanically forming a linear groove on one side of the steel sheet surface in a direction substantially perpendicular to the rolling direction, the sample was heated to 650 ° C. to recrystallize 90% or more of the steel sheet. % Or more, and then re-crystallize 90% or more of the steel sheet by heating up to 650 ° C without mechanical processing. A sample was prepared.

These samples were soaked in wet hydrogen at a soaking temperature of 850.
After annealing for decarburization at 2 ° C. for 2 minutes, an annealing separator of MgO was applied to the surface of the steel sheet, annealing was performed at 1200 ° C. for 20 hours for secondary recrystallization. After the secondary recrystallization annealing, a linear groove was mechanically formed on one surface of the steel sheet in a direction substantially perpendicular to the rolling direction in the same manner as described above.
The distance between the linear grooves was 5 mm, and the groove depth was 16 μm. From these samples, cut out a single plate magnetic measurement sample,
The strain relief annealing was performed at 800 ° C. for 3 hours. Table 1 shows the results of the magnetic measurement of each sample. The iron loss, the magnetic flux density, and the magnetostriction are values measured under a magnetic flux sine wave condition in a state where no stress is applied to the steel sheet.

[0012]

[Table 1]

As can be seen from Table 1, the iron loss and the magnetostriction of the above sample are superior to those of the other samples.
FIG. 1 shows the secondary recrystallized structures of these samples. FIG. 1 a)
Is a schematic diagram of the secondary recrystallization structure of the present invention example, b) is a schematic diagram of the secondary recrystallization structure of the comparative example, and c) is a photograph of the secondary recrystallization structure of the present invention example. Thus, while the grain boundary of the sample has no relation to the position of the groove, the position of the lower part of the groove and the position of the secondary recrystallized grain boundary in a considerable part of the sample are consistent. I understand. In addition, in the example of the present invention, it can be seen that the secondary recrystallized grain boundaries crossing the groove are separated by the groove.

The present inventors have conducted more detailed experiments and found the following relationship. That is, as shown in FIG. 2, when the ratio of the length of the groove where the secondary recrystallized grain boundary exists below the groove to the total length of the introduced groove is 15% or more and 90% or less, excellent iron loss is obtained. Have. In this series of experiments, 3.1% Si
A cold-rolled sheet of grain-oriented electrical steel containing AlN and MnS is heated to 800 ° C. at a heating rate of 300 ° C./sec. It was processed and then subjected to the same treatment as in the above experiment to perform secondary recrystallization.

The reason why the above-described excellent iron loss value can be obtained is that a composite effect of a magnetic domain control effect by a linear groove and a magnetic domain control effect by a regularly introduced secondary recrystallization grain boundary is considered. Presumed. It is considered that the improvement in iron loss due to this combined effect is small when the grain boundaries introduced are too small, and rather small when the grain boundaries are too large.

The reason why the magnetostriction is reduced by introducing an appropriate amount of linear grooves and secondary recrystallized grain boundaries is as follows.
A lancet-assisted magnetic domain (eg, Alex Hubertet.al.Z.Angew.Phys., 19,521-52) generated when the crystal orientation of secondary recrystallized grains deviates from the ideal Goss orientation.
9, (1965)) compensates for the effect of shrinking the grain-oriented electrical steel sheet when excited by the magnetic field, and the effect of stretching the grain-oriented electrical steel sheet when excited by the auxiliary domains generated in the grooves or secondary recrystallized grain boundaries. It is estimated that this has occurred. Further, in the example of the present invention, the fact that the secondary recrystallized grain boundaries crossing the grooves are separated by the grooves is also presumed to be one of the reasons described above.

Hereinafter, embodiments of the present invention will be described. As the components of the grain-oriented electrical steel sheet of the present invention, any conventionally known component compositions are suitable, but the following are representative compositions. When Si is added in a large amount, the electric resistance increases and the iron loss characteristics are improved. However, if it exceeds 4.8%, cracks are likely to occur during rolling. Also 0.
If it is less than 8%, γ transformation occurs at the time of finish annealing, and the crystal orientation is impaired.

C is an element effective in controlling the primary recrystallized structure, but has an adverse effect on the magnetic properties. Therefore, it is necessary to remove carbon before the finish annealing. If C is more than 0.085%, the decarburization annealing time will be long and productivity will be impaired.

The so-called inhibitors required to cause secondary recrystallization include AlN-based, MnS-based, and Mn-based.
Although any of the Se-based alloys does not impair the intention of the present invention, the AlN-based alloy is most suitable for obtaining a lower iron loss. In this case, the acid-soluble Al is preferably 0.01 to 0.065% at which the secondary recrystallization is stable.

If N exceeds 0.012%, voids in the steel sheet called blisters are generated during cold rolling, so it is desirable to keep the N or less. In addition, trace amounts of Cu, S
The inclusion of b, Mo, Bi, Ti, etc. in steel does not impair the gist of the present invention.

The steel slab thus obtained is heated, hot-rolled, and if necessary, subjected to hot-rolled sheet annealing, and then cold-rolled once or twice with intermediate annealing to obtain a final sheet thickness. After that, if necessary, decarburization annealing in wet hydrogen, Mg
An annealing separator mainly composed of O is applied to the surface, and final finish annealing for the purpose of secondary recrystallization is performed.

In the above steps, it is a feature of the present invention that the steel sheet which has been subjected to the cold rolling, the primary recrystallized steel sheet is mechanically subjected to linear or discontinuous groove processing and then subjected to the secondary recrystallization. By this process, a secondary recrystallized grain boundary is formed in most of the lower portion of the groove, and excellent iron loss characteristics and magnetostriction characteristics are exhibited.

Regarding the method of mechanically forming grooves, any of a method using a gear type roll disclosed in Japanese Patent Publication No. 62-53579 and a method using a press disclosed in Japanese Patent Publication No. 06-63037 may be used. You may. The shape of the groove to be formed is preferably a continuous or discontinuous linear groove substantially perpendicular to the rolling direction, particularly a continuous linear groove. The effect is greatest in the direction perpendicular to the rolling direction, but the effect is not significantly changed within 30 ° from the direction perpendicular to the rolling direction. Although a straight shape is desirable for machining the tool, the effect is not lost even if the groove is curved. For curves,
The direction of the center line should be within 30 ° from the direction perpendicular to the rolling.

The width of the linear groove is 10 to 300 μm and the depth is 5
Although it is preferable that the groove interval is 1 to 20 mm in the rolling direction, even if it is out of this range, the effect of the present invention is not necessarily not exhibited. Although the groove processing is sufficiently effective only on one side, it is not contrary to the idea of the present invention even if it is performed on both sides.

The primary recrystallization preferably completes a recrystallization ratio of 50% or more, more preferably 90% or more, as observed in the metal structure of the cross section, but does not necessarily limit the conditions of the present invention. The recrystallization temperature is desirably 600 ° C. or higher when the recrystallization ratio is 50%, and 650 ° C. or higher when the recrystallization ratio is 90%. As a method of primary recrystallization, a method using a general annealing furnace, a method using electric heating, and a method using induction heating do not impair the idea of the present invention. Therefore, a method using electric heating or induction heating is preferable.

The steel sheet having a groove formed on the surface thus obtained is subjected to annealing for the purpose of decarburization and primary recrystallized grain growth in wet hydrogen, if necessary, but only to the extent that magnetic aging does not occur. When C is not contained in the steel component, the effect of the annealing may be used in the first half of the secondary recrystallization annealing described below.

Thereafter, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet and subjected to high-temperature secondary recrystallization annealing. At this time, an annealing separator mainly composed of Al ₂ O ₃ is used, and M
It is also possible to take a step in which a ceramic coating made of g ₂ SiO _{4 is} not formed. In the secondary recrystallization annealing, after the above wet hydrogen annealing with optionally NH ₃ gas as in JP-A-2-77525 and the like, an atmosphere gas such as NH ₃ before the secondary recrystallization annealing A by nitriding from
Reinforcing the 1N inhibitor or reinforcing the AlN-based inhibitor by nitriding in a N ₂ atmosphere before the secondary recrystallization annealing does not impair the effects of the present invention. When C is contained only to the extent that magnetic aging does not occur, primary recrystallized grain growth is performed in the first half of the secondary recrystallization annealing, and decarburization in wet hydrogen and primary recrystallized grain growth are performed. It is also possible to omit the annealing for the purpose.

[0028]

The present invention will be further described below with reference to examples. (Example 1) 3.3% by mass of Si, MnSe and AlN,
Inhibitor component of Sb (Mn: 0.07 by mass)
%, Se: 0.02%, acid-soluble Al: 0.025%,
N: 0.008%, Sb: 0.04%)
After a cold rolled sheet having a thickness of mm was heated to 700 ° C. in an annealing furnace at 30 ° C./sec and recrystallized 100%, (A) samples A and (B) in which linear grooves were formed using a gear-type roll After transferring the groove pattern by gravure printing, each of the samples B subjected to the groove processing by electrolytic etching was annealed in wet hydrogen at 850 ° C. for 100 seconds, and an annealing separator mainly composed of MgO was applied to the surface of the steel sheet. For 17 hours.
The groove shape of both A and B is linear, the angle is 12 ° from the direction perpendicular to the rolling, the groove interval is 3 mm, the groove width is 100 μm, and the groove depth is 20 μ.
m. Table 2 shows the respective iron loss values. It can be seen that the core loss of the material A having the lower grain boundary ratio in the range of the present invention is lower than that of the material B.

[0029]

[Table 2]

Embodiment 2 FIG. 3 shows an example of a preferred apparatus for forming a linear groove in the production of a grain-oriented electrical steel sheet according to the present invention. That is, the cold-rolled sheet 1 wound around the coil of the grain-oriented electrical steel sheet is unwound and passes through the heating device 2, and is heated to a recrystallization temperature or higher to recrystallize the steel sheet. The heating means may be either electric heating or induction heating. Next, the steel sheet is introduced into the groove forming apparatus 3 and machined to form a linear or discontinuous groove on the surface of the steel sheet, and then subjected to annealing for decarburization in the annealing apparatus 4 to obtain Mg.
The process from applying an annealing separator mainly composed of O to the surface of a steel sheet by a coater 5 and winding the same around a coiler 6 will be described. Although FIG. 3 shows a series of steps of the heating device 2, the groove forming device 3, and the annealing device 4, the heating device and the groove forming device may be incorporated in an annealing device for decarburization.

[0031]

According to the present invention described above, a grain-oriented electrical steel sheet with reduced iron loss and magnetostriction can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram of a steel sheet surface showing a positional relationship between a groove and a secondary recrystallized grain boundary. The dotted line indicates the position of the groove, and the solid line indicates the position of the secondary recrystallized grain boundary. The thick solid line indicates the portion where the secondary recrystallized grain boundary is below the groove. a) is a present invention example, b) is a comparative example. c) is a metallographic photograph on the steel sheet surface in the example of the present invention.

FIG. 2 is a view _showing the relationship between the abundance ratio of the secondary recrystallized grain boundaries penetrating the thickness of the lower part of the linear groove to the total groove length and the iron loss W _17/50 .

FIG. 3 is a diagram showing an example of an apparatus for forming a substantially linear groove in a direction substantially perpendicular to a rolling direction by heating a cold-rolled sheet of grain-oriented electrical steel sheet, followed by annealing.

[Explanation of symbols]

 1: Cold rolled sheet 2: Heating device 3: Groove forming device 4: Annealing device 5: Coater 6: Coiler

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigekazu Oba 2-6-3 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Steel Corporation (72) Inventor Tsutomu Kobayashi 1 Fujimachi, Hirohata-ku, Himeji-shi, Japan F-term in Hirohata Works (reference) 4K033 AA02 DA02 MA00 PA06 5E041 AA02 CA02 HB11 HB15 HB19 NN01 NN15 NN17

Claims (8)

[Claims] The present invention is characterized in that it has a linear groove in a direction substantially perpendicular to the rolling direction, and a secondary recrystallized grain boundary exists in a portion of 15% or more and 90% or less in length of the groove lower part. Low iron loss oriented electrical steel sheet. 2. After the grain-oriented electrical steel sheet is finally cold-rolled and heated to a recrystallization temperature, a linear groove is formed by machining in a direction substantially perpendicular to the rolling direction, and then a secondary recrystallization annealing is performed. As a result, the length of the lower part of the linear groove is 15% or more 9
A method for producing a low iron loss grain-oriented electrical steel sheet, wherein a secondary recrystallized grain boundary is present in a portion of 0% or less. 3. The decarburization is performed by annealing in wet hydrogen after mechanical processing and before secondary recrystallization annealing.
A method for producing a low iron loss grain-oriented electrical steel sheet as described in the above. 4. The method for producing a low iron loss grain-oriented electrical steel sheet according to claim 2, wherein the heating method up to the recrystallization temperature is electric heating or induction heating. 5. A heating device for heating a cold rolled sheet to a recrystallization temperature after final cold rolling in a grain-oriented electrical steel sheet manufacturing process,
An apparatus for manufacturing a low iron loss grain-oriented electrical steel sheet, comprising a groove forming apparatus for forming a linear or discontinuous linear groove in a direction substantially perpendicular to a rolling direction by machining. 6. The apparatus according to claim 5, wherein the heating by the heating device is electric heating or induction heating. 7. The apparatus according to claim 5, wherein the heating device and the groove forming device are incorporated in an annealing device for decarburization in wet hydrogen. 8. The apparatus according to claim 7, wherein the heating up to the recrystallization temperature is electric heating or induction heating.