JP2001192785A - Grain oriented silicon steel sheet excellent in magnetic property, and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably manufacture a grain oriented silicon steel sheet excellent in magnetic properties on an industrial scale. SOLUTION: Si in an amount of 2.0-5.0 mass % is incorporated into the Fe matrix of a product sheet, and the area weighted mean value of maximum length of secondary recrystallized grains in a direction perpendicular to rolling direction is regulated to 30-300 mm. Further, with respect to the crystal orientation of the secondary recrystallized grains, the conditions of inequalities <α><=6 deg....(1) and <σ(β)><=2 deg....(2) (wherein, <α> is the area weighted mean value of the angle formed by a [001] axis situated nearest to the rolling direction among the [001] axes of secondary recrystallized grains and the rolling direction within the rolling plane; and <σ(β)> is the mean value of the standard deviation, in a direction perpendicular to the rolling direction, of the angle formed by the [001] direction of secondary recrystallized grains and the rolling plane) are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a transformer, a generator,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet which is suitable for use as an iron core material of an electric device such as a rotating machine and has excellent magnetic properties, particularly iron loss properties, and a method for producing the same.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used as materials for laminated iron cores and wound iron cores of transformers, and in terms of characteristics, energy loss (iron loss) particularly associated with power conversion from the viewpoint of reducing transmission and distribution costs. Is required to be small. One of the techniques for reducing iron loss is to align the <001> axis, which is the axis of easy magnetization of the iron crystal, with the rolling direction. The crystal structure of iron is called {110} <001> orientation called Goss orientation. High integration, high permeability is obtained,
It is known that iron loss decreases.

[0003] In order to obtain such a crystal structure integrated in the Goss orientation, a phenomenon called secondary recrystallization is used.
That is, in the thermal growth process of primary recrystallized grains, a desired structure can be obtained by preferentially growing crystal grains having the Goss orientation by utilizing abnormal grain growth with extremely strong orientation selectivity. At this time, it is important to control two points of orientation selectivity and abnormal grain growth rate in order to obtain a secondary recrystallized structure having a high degree of integration in the Goss orientation. For this purpose, the primary recrystallized structure before the secondary recrystallization is made to have a predetermined texture, and a precipitation-dispersed phase called an inhibitor that selectively suppresses the growth of the primary recrystallized grains is formed at a uniform and appropriate size. There is a need.

[0004] To achieve the latter object,
Japanese Patent Application Laid-Open No. 46-23820 discloses a technique of forming a complex precipitation phase of MnSe or MnS and AlN and acting as a strong inhibitor. However, when a crystal structure having a high degree of integration in the Goss orientation is obtained by these techniques, the iron loss of the product does not always decrease. The reason for this is that the secondary recrystallized grain size is inevitably coarsened.

In order to solve the above problem, Japanese Patent Publication No.
Japanese Patent No. 20745 discloses a technique for reducing iron loss by reducing the average grain size of secondary recrystallized grains, and Japanese Patent Publication No. 4-19296 discloses a technique for controlling the number and distribution of fine secondary grains. Each technology for reducing iron loss is disclosed. However, the technology for refining secondary grains is incompatible with the recent technical idea of grain-oriented electrical steel sheets that seeks to obtain a high magnetic flux density by growing only grains that are extremely close to the Goss orientation. This resulted in deterioration of characteristics.

Various techniques for preventing the deterioration of iron loss due to the coarsening of the secondary recrystallized grains by controlling the structure of the secondary recrystallized grains have been conventionally proposed.
In Japanese Patent No. 223, the iron loss characteristics of grain-oriented electrical steel sheets are governed by the angle between the [001] axis of the secondary recrystallized grains closest to the rolling direction and the rolled surface (hereinafter referred to as β angle). With this knowledge, a technique for obtaining a product with low iron loss by setting the β angle to 4 ° or less is disclosed. In addition, JP 54
Japanese Patent Application Laid-Open No. -40223 and Japanese Patent Application Laid-Open No. Sho 59-177349 disclose a technique in which a steel strip is corrugated at the time of secondary recrystallization to thereby control the β angle in an appropriate range. The above β angle is 4 °
The following control is a technique which has been generally achieved in recent years, but it is impossible to obtain a lower iron loss than today by simply reducing the β angle. In addition, it is industrially difficult to perform the final finish annealing in a wave shape.

On the other hand, the inventors have been developing materials focusing on the effect of reducing iron loss by improving the local magnetic flux density distribution inside the grain-oriented electrical steel sheet, and have improved the secondary recrystallization orientation distribution. Various techniques for making the distribution of the magnetic flux density inside the steel sheet uniform have been proposed (for example, see JP-A-8-4904).
No. 5, JP-A-8-288115 and JP-A-9-20
No. 9043). In these methods, the aspect ratio of the secondary recrystallized grains and the crystal orientation difference between the secondary recrystallized grains adjacent in the direction perpendicular to the rolling direction (the difference in the orientation in the rolling plane) are within an appropriate range. The main purpose is to reduce the non-uniformity of the magnetic flux distribution inside the material and improve the iron loss. However, when these techniques are applied, the effect of reducing iron loss can be obtained regardless of the presence or absence of the magnetic domain refining treatment, but the control of the crystal orientation becomes unstable, and sudden magnetic property deterioration may be caused. .

Further, Japanese Patent Application Laid-Open Nos.
No. 215419 discloses a technique in which secondary recrystallization is performed while applying a temperature gradient in the width direction of the steel strip, thereby obtaining a secondary recrystallized grain morphology advantageous for uniform magnetization with high magnetic flux density. However, it is industrially difficult to provide a temperature gradient in the width direction of the steel strip and to completely control even the form of the secondary recrystallized grains by using the temperature gradient, which is high in industrial difficulty and cost. There was a problem that it caused an increase.

In addition, the inventors have disclosed in Japanese Patent Application No. 10-201647 that secondary recrystallized grains having a maximum length in the rolling direction of 60 mm or more by incorporating As, Sb, and Bi in the material. A technique for obtaining a uniform magnetic flux density distribution inside the steel sheet has been disclosed, but this technique leaves a disadvantage in that it is difficult to control the frequency and orientation of fine grains scattered inside coarse secondary grains. I was

[0010]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems, and provides a grain-oriented electrical steel sheet having excellent magnetic properties suitable as an iron core material for a transformer or a generator. The purpose is to propose along with the method.

[0011]

Means for Solving the Problems In order to establish a technology capable of reducing iron loss without depending on fine crystal grains in a steel sheet, the present inventors have proposed a method for reducing the iron loss of a grain-oriented electrical steel sheet. As a result of research focusing on the influence of the shape and orientation of secondary recrystallized grains on the local magnetic flux density inside the steel sheet (hereafter,
It was found that it is important to improve the non-uniformity of the peak value and the phase non-uniformity of the local magnetic flux density. In order to improve the former non-uniformity, the width of the secondary recrystallized grains in the direction perpendicular to the rolling direction (the direction perpendicular to the rolling direction) is made sufficiently large, and the α angle (of the [001] axis of the Fe crystal) Of these, it is effective to reduce the angle between the rolling direction closest to the rolling direction and the rolling direction in the rolling plane), while to improve the latter non-uniformity, it is effective to equalize the β angle in the direction perpendicular to the rolling direction. Was found. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. A grain-oriented electrical steel sheet containing 2.0 to 5.0 mass% of Si in the product sheet iron, wherein the area-weighted average value of the maximum length in the direction perpendicular to the rolling direction of the secondary recrystallized grains is from 30 mm to 300 mm, and A grain-oriented electrical steel sheet having excellent magnetic properties, wherein the crystal orientation of secondary recrystallized grains satisfies the conditions of the following formulas (1) and (2). <Α> ≦ 6 ° --- (1) <σ (β)> ≦ 2 ° --- (2) where <α> is the rolling direction of the [001] axis of the secondary recrystallized grains. The area-weighted average value of the angle between the closest one and the rolling direction in the rolling plane. <Σ (β)>: Measure the angle β between the rolling surface and the [001] axis of the secondary recrystallized grains closest to the rolling direction in the rolling direction and the direction perpendicular to the rolling direction in the steel sheet, The standard deviation σ (β) of the distribution in the direction perpendicular to the rolling direction was obtained, and this was averaged in the rolling direction.

2. 2. The grain-oriented electrical steel sheet according to 1 above, wherein the composition further contains Bi: 0.0003 to 0.05 mass% in the product sheet iron.

3. C: 0.03 to 0.10 mass%, Si: 2.0 to 5.
0 mass%, Mn: 0.04 to 0.15 mass%, S and / or S
e: 0.005 to 0.040 mass%, sol.Al: 0.015 to 0.035 mas
s%, N: 0.003 to 0.013 mass% and Bi: 0.001 to 0.0
A silicon steel slab with a composition containing 70 mass% is heated, hot-rolled, then combined with annealing and cold rolling to a final thickness, decarburized and then wound into coils In the method for manufacturing a grain-oriented electrical steel sheet comprising a series of steps of performing a final finish annealing after the decarburization annealing and before winding on a coil, to introduce a small strain to the steel strip, The method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the amount of strain to be introduced is adjusted so that the iron loss of the decarburized annealed sheet before and after the strain introduction satisfies the following formula (3). . Note 0.01 ≦ (W′−W) /W≦0.15 --- (3) where, W: iron loss of the decarburized annealed plate before strain introduction W _10/50 W ′: after strain introduction and before coil winding Loss of decarburized annealed steel sheet W _10/50

4. C: 0.03 to 0.10 mass%, Si: 2.0 to 5.
0 mass%, Mn: 0.04 to 0.15 mass%, S and / or S
e: 0.005 to 0.040 mass%, sol.Al: 0.015 to 0.035 mas
s%, N: 0.003 to 0.013 mass% and Bi: 0.001 to 0.0
A silicon steel slab with a composition containing 70 mass% is heated, hot-rolled, then combined with annealing and cold rolling to a final thickness, decarburized and then wound into coils In the method for manufacturing a grain-oriented electrical steel sheet comprising a series of steps of performing a final finish annealing, the final cold-rolled sheet thickness is set to 0.1 to 0.5 mm, and after the decarburizing annealing is completed and before winding on a coil. Radius of steel strip: 100 mm or more,
A direction that excels in magnetic properties, characterized by applying a process of bending a cylinder of 400 mm or less by 1/4 turn or more to return to a flat state, followed by a process of applying a tension of 20 to 110 MPa in the rolling direction. Manufacturing method of conductive electrical steel sheet.

5. C: 0.03 to 0.10 mass%, Si: 2.0 to 5.
0 mass%, Mn: 0.04 to 0.15 mass%, S and / or S
e: 0.005 to 0.040 mass%, sol.Al: 0.015 or less, B:
A silicon steel slab having a composition containing 0.0010 to 0.0100 mass%, N: 0.003 to 0.013 mass% and Bi: 0.001 to 0.070 mass% is heated, hot-rolled, and then combined with annealing and cold-rolling. After the final sheet thickness, subjected to decarburizing annealing, then in a method of manufacturing a grain-oriented electrical steel sheet consisting of a series of steps of winding the coil and then performing the final finish annealing, from the end of decarburizing annealing until winding to the coil In the meantime, a slight strain is introduced into the steel strip, and the amount of the strain to be introduced is adjusted so that the iron loss of the decarburized annealed plate before and after the strain introduction satisfies the following formula (3). A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties. Note 0.01 ≦ (W′−W) /W≦0.15 --- (3) where, W: iron loss of the decarburized annealed plate before strain introduction W _10/50 W ′: after strain introduction and before coil winding Loss of decarburized annealed steel sheet W _10/50

6. C: 0.03 to 0.10 mass%, Si: 2.0 to 5.
0 mass%, Mn: 0.04 to 0.15 mass%, S and / or S
e: 0.005 to 0.040 mass%, sol.Al: 0.015 or less, B:
A silicon steel slab having a composition containing 0.0010 to 0.0100 mass%, N: 0.003 to 0.013 mass% and Bi: 0.001 to 0.070 mass% is heated, hot-rolled, and then combined with annealing and cold-rolling. After the final sheet thickness, decarburizing annealing is performed, then the coil is wound and then subjected to final finishing annealing.In the method for manufacturing a grain-oriented electrical steel sheet, the final cold-rolled sheet thickness is reduced to 0.1 to 0.5 mm. At the same time, between the end of decarburization annealing and winding to a coil, the steel strip is bent at least 1/4 turn into a cylinder with a radius of 100 mm or more and 400 mm or less, and then returned to a flat state. Continue in the rolling direction
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by performing a treatment for applying a tension of 20 to 110 MPa.

[7] In 3, 4, 5, or 6, the silicon steel slab further comprises Cr and / or Cu: 0.05 to 0.1.
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by having a composition containing mass%.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The results of the research on which the present invention is based will be described below. A silicon steel slab having the component compositions indicated by symbols A to D in Table 1 was charged into a gas heating furnace, and heated at 1200 ° C and 60 ° C.
After heating for 1 minute, it was further heated at 1400 ° C. for 40 minutes by induction heating, and then hot-rolled into a hot-rolled sheet having a thickness of 2.2 mm. Subsequently, the sheet is annealed at 1000 ° C. for 1 minute, hot-rolled, and after being pickled, first cold-rolled to a thickness of 1.7 mm.
Intermediate annealing was performed for 1 minute at ℃, and after pickling, a final sheet thickness of 0.23 mm was obtained by secondary cold rolling. Then, in an atmosphere where the ratio of the partial pressure of water vapor to the partial pressure of hydrogen in a mixed atmosphere of hydrogen, nitrogen and water vapor (P (H ₂ O) / P (H ₂ )) = 0.50, 850 ° C., 10
After decarburizing annealing for 0 seconds, an annealing separator containing 5 mass% of TiO ₂ and the remainder substantially consisting of MgO was applied to the coil at a basis weight of 7 g / m ² per one side of the steel sheet. After winding, final annealing was performed at a maximum temperature of 1200 ° C. for 10 hours. Thereafter, the unreacted annealing separating agent was removed by washing with water, and an insulating tension coating containing magnesium phosphate and colloidal silica as main components was applied to obtain a product plate.

[0020]

[Table 1]

From the product sheet thus obtained, the rolling direction:
A test piece having a size of 500 mm and a width direction of 500 mm was collected and subjected to magnetic measurement by an SST test. Thereafter, each specimen was macro-etched, and the morphology of the secondary recrystallized grains was recorded. Also,
The crystal orientation of each part was measured by X-ray diffraction. The magnetic flux density B ₈ of each of the samples obtained by the above method was 1.94 T or more, but no clear relationship was observed between B ₈ and iron loss.

Then, next, as shown in the schematic diagram of FIG. 1, the area-weighted average value of the α-angle (absolute value) of the secondary recrystallized grains <
α> was determined for each specimen by the following equation (4).

(Equation 1) Here, the above Σ represents the crystal grain 1 ・
··· i ... N S is the sum of the areas of all the crystal grains in the specimen, and corresponds to the area of the entire specimen. Further, _Si is the area of the crystal grain i, and α _i is the angle (absolute value) between the [001] axis of the crystal grain i and the rolling direction in the rolling plane.

The maximum length L _i of the secondary recrystallized grains i in the direction perpendicular to the rolling direction is, as shown in FIG.
This line is contacted from both sides of the secondary recrystallized grain i of interest so as not to intersect with the secondary grain boundary, and is defined as the interval between these lines. Seeking L _i in accordance with this definition, the area weighted average value of the entire specimen <L>
Was determined by the following equation (5) for each specimen.

(Equation 2) Here, the above-mentioned L _i is the maximum length in the direction perpendicular to the rolling direction of the secondary recrystallized grains i, the S _i is the area of the grains i. Also,
Σ is the sum of the crystal grains 1... I... N contained in the specimen. Note that the α-angle and the length in the direction perpendicular to the rolling direction of each crystal grain both increase as the area of the crystal grain increases as the area of the crystal grain increases.
In (4) and (5), the area weighted average value multiplied by the area ratio was used.

FIG. 2 shows the relationship between <L> and iron loss W _{17/50 of} each test _piece , classified by <α>. As is evident from the figure, <α> is 6 ° or less and <L> is 30 to 300.
In the case of mm, an excellent iron loss value where W _17/50 is _less than 0.85 W / kg is obtained.

As described above, the reason why low iron loss can be obtained by reducing <α> is that, as shown in FIG.
It is considered that the reduction in the angle reduces unevenness in the magnetic flux density caused by the component in the rolling direction in the grain boundary. That is, when the α angle is large, not only does the amount of magnetic pole generation on the grain boundaries in the rolling direction increase, but also the [001]
The area of the portion where the magnetic flux density decreases extending in the axial direction increases, and the distribution of the magnetic flux density becomes non-uniform.

The reduction of iron loss due to the increase of <L> is as follows.
As shown in FIG. 4, it is considered that the area of the portion where the magnetic flux decreases due to the α angle decreases with the increase in the length of the secondary grains in the direction perpendicular to the rolling direction. Therefore, <α>, <L
It can be considered that the reduction of the iron loss by the control of> is achieved by making the local magnetic flux density distribution uniform.

As described above, it is possible to reduce iron loss to some extent by controlling <L> and <α>. However, as shown in FIG. From this, it is understood that the influence of another factor on the iron loss value is not small. Where <
Under a secondary recrystallized structure in which L> 30 to 300 mm, which is larger in the direction perpendicular to the rolling direction than before, it is important to reduce the non-uniformity of the β angle in the direction perpendicular to the rolling direction of the steel strip in order to reduce iron loss. As expected. The knowledge that formed the basis of this prediction is shown below.

When there is a portion having a different β angle in the direction perpendicular to the rolling direction of the steel strip, the magnetic flux density waveform inside each grain is measured by a probe method (T. IEE Japan, Vol. 115-A, 50 (1995), Theoretical Evaluation of Local Magnetic Flux Density Measurement Accuracy by Needle Method "). As a result, as shown in FIG. 5, when the secondary recrystallized grains having different β angles exist side by side in the direction perpendicular to the rolling direction of the steel strip, even when the entire sample is controlled to have a sine wave,
Due to the difference in the magnetic domain width, a local excitation phase is shifted. That is, in the grain (1) having a small magnetic domain width, the magnetization progresses faster than the average magnetic flux density in the low magnetic flux density region, and in the grain (2) having the large magnetic domain width, the progress is slow. As a result, distortion occurs in the local magnetic flux density waveform, and eddy current loss increases.

It is considered that such a phase shift of the local magnetic flux density due to the difference in the magnetic domain width is caused by an effect that the eddy current generated at the domain wall position delays the movement of the domain wall. On the other hand, when there is a difference in the β angle between the regions arranged in the rolling direction, the magnetic flux in the sample is continuous in the rolling direction, so that no distortion occurs in the local magnetic flux waveform. From the above, the direction orthogonal to the magnetization direction,
That is, in the grain-oriented electrical steel sheet, it has been newly found that equalizing the β angle in the direction perpendicular to the rolling is important for reducing iron loss.

Based on the above newly obtained knowledge, the inventors found that the cause of the variation in iron loss remaining after the optimization of <L> and <α> shown in FIG. _Therefore , the relationship between the variation and the iron loss W _17/50 was investigated. That is, since the magnetic domain width at each position depends on the β angle, the intention was to make the magnetic domain width uniform in the direction perpendicular to the rolling, thereby suppressing the cause of the increase in iron loss due to the uneven magnetic domain width.

The variation of the β angle (absolute value) in the direction perpendicular to the rolling direction of the steel strip was converted into a numerical value in the form of a standard deviation, and the value averaged over the rolling direction was defined as <σ (β)>. That is, as shown in FIG. 6 and the following equation (6), <σ (β)> is a line 1.
M is drawn at regular intervals, and points 1 at regular intervals on this line j
··········· Measures β angle at N, finds standard deviation σ (β) of β angle at line j, and averages this at lines 1 ... j M Can be

(Equation 3)

Hereinafter, the entire area of the sample having a width of 500 mm and a length of 500 mm is pitched by 20 mm in the direction perpendicular to the rolling direction and in the rolling direction.
The crystal orientation was measured in a mesh at a pitch of 40 mm, and <σ (β)> was determined using the results. In FIG. 7, <L> is
30~200 mm, <α> iron loss W _17/50 and the standard deviation of the direction perpendicular to the rolling direction of the β angle of the sample when it is in the range of 6 ° or less <sigma
(Β)>. As is clear from FIG.
In addition to the control of L> and <β>, when <σ (β)> is 2.0 ° or less, W _17/50 is less than 0.80 W / kg. Iron loss values have been obtained.

Next, a method of manufacturing a grain-oriented electrical steel sheet having the above secondary recrystallized structure was examined. From the slabs of the components shown in Table 1, 30 mm ≦ <L> ≦ 200 mm, <α
> ≦ 6 °, <σ (β)> ≦ 2.0 °
× 500 mm) was obtained, A: 5%,
B: 15%, C: 35%, D: 55%. Therefore, it can be seen that it is effective to add Bi to the material in order to obtain a secondary recrystallized structure satisfying the above conditions. However, with such a probability, it is difficult to industrially obtain good magnetic characteristics over the entire length of the coil.

Therefore, the present inventors have conducted further research on this point, and as a result, after performing decarburizing annealing, a process of introducing a minute strain into a decarburized annealed plate immediately before being wound on a coil is performed. However, it has been found that it is extremely effective in satisfying the conditions of the secondary recrystallization structure and obtaining good magnetic properties. Hereinafter, the details of the clarification will be described.

The decarburized annealed sheet obtained from the slabs represented by the symbols A, B, and C in Table 1 in the same process as the above-described experiment was subjected to a slight strain by bending and applying a tensile tension. After being wound on the coil, an annealing separator was applied, and final finishing annealing was performed. Here, the curvature bending process of the steel strip is performed as shown in FIG.
As shown in FIG. 1, the steel strip 2 was wound around a rotating roll 1. The tension was applied in the rolling direction while conveying the steel strip. From the product sheet thus obtained, 20 SST specimens having a length in the rolling direction of 500 mm and a width of 500 mm were sampled, and the iron loss W _17/50 and the magnetic flux density B ₈ were measured, and the average value was determined. The magnetic properties of the product sheet obtained under each condition were obtained.

Table 2 shows the radius of the roll subjected to the bending treatment and the pull.
Tensile tension, rate of change in iron loss of decarburized annealed sheet (W'-W) / W ×
100 (%), maximum in the direction perpendicular to the rolling of secondary recrystallized grains
Area weighted average of length <L>, area weight of α angle (absolute value)
Weighted average <α>, average of standard deviation of β angle in width direction <σ
(Β)> and iron loss W_17/50 Is shown. Where W, W '
Is the iron in the decarburized annealed plate in the unstrained state and after the introduction of strain
Loss W _10/50 (Maximum magnetic flux density Bm: 1.0 T, excitation frequency:
50Hz). Also, the amount of strain introduced into the decarburized annealed plate is large.
The higher the W after the introduction of strain_10/50 Are in a relationship of rising
Where (W′−W) / W is the strain introduced into the decarburized annealed sheet.
It can be said that it represents a quantity. W 'and W are width: 100 mm, length
Length: 280 mm specimen size, magnetic flux sine with single-plate magnetometer
Measured under wave conditions. Iron loss W 'after strain introduction is an annealing separator
Measurement of decarburized annealed plate just after being wound on coil after coating
Value. W is the sample after W 'measurement, with almost no grain growth
Does not occur Strain removal annealing in an Ar atmosphere at 700 ° C for 30 minutes
The value after the measurement was taken. In addition, the Si and Bi components in the steel
Table 1 also shows the results of the analysis.

[0037]

[Table 2]

As is apparent from Table 2, the material containing Bi in steel is wound around a roll having a radius of 100 to 400 mm after decarburizing annealing and before being wound into a coil shape. By performing the treatment and the treatment of applying a tension of 20 to 110 MPa in the rolling direction, the iron loss change rate (W′−W) / W × 100 (%) of the decarburized annealed sheet is in the range of 1 to 15%. It can be seen that a grain-oriented electrical steel sheet having excellent desired magnetic properties was obtained as a result. In addition, the iron loss value of the steel sheet C with the Bi content of 0.0006 mass% in the base steel of the product sheet is lower than that of the steel B with the Bi content in the sheet steel of the product sheet being 0.0002 mass%. It was found that Bi was desirably contained in the steel plate of the product plate in a certain amount or more.

As described above, it is not necessarily clear why the introduction of a small strain into the steel strip after the decarburizing annealing makes it possible to produce a desired low iron loss grain-oriented electrical steel sheet. , By introducing a small strain into the decarburized annealed sheet containing Bi, Bi dispersed in steel
It is presumed that strain was accumulated in the vicinity of the precipitate, and that the nucleation of secondary recrystallization with a small deviation of the β angle in the direction perpendicular to the rolling was promoted. Incidentally, the proper amount of strain for such secondary recrystallized grains in the control of nucleation, can be sensitively measured by the change in iron loss of the decarburization annealed sheet, the proper range is iron loss W _{10
/ 50} change rate (W′−W) / W × 100 (%)
It is considered to be in the range of 15%. Further, due to the micro-strain introduced into the primary recrystallization structure, the secondary grains are easily elongated in the direction perpendicular to the rolling, and the effect of increasing <L> is also present.

Here, in order to introduce the above-mentioned amount of distortion into the inside of the steel sheet, the steel strip is bent at a radius of curvature of 100 to 400 mm, and is flattened.
It is effective to perform a process of applying a tension of 20 to 110 MPa. The reason is that the above-mentioned strain is effectively introduced around the precipitates by the bending treatment, the treatment for flattening the same again, and the subsequent treatment for applying tension in the rolling direction. Further, as shown in FIG. 8, by winding the steel strip so that the rolling direction is substantially perpendicular to the axis of the cylinder,
Uniform strain is introduced in the direction perpendicular to the rolling, and β
It is expected that the angular deviation can be reduced.

Next, the reason why the constituent elements of the grain-oriented electrical steel sheet according to the present invention are limited to the above ranges will be described.・ Si content in product sheet iron: 2.0 to 5.0 mass% Si is necessary to increase iron resistance to reduce iron loss and to stabilize α phase of iron to enable high-temperature heat treatment. It is an element and requires at least 2.0 mass%, but if it exceeds 5.0 mass%, cold rolling becomes difficult, so the Si content is
Limited to 2.0-5.0 mass%.

Bi content in product steel plate iron: 0.0003 to 0.05 mass
% Bi is, AlN, MnS, MnSe, Cu 2-x Se, by coexisting with precipitation distributed inhibitors such as Cu _2-x S, enhance normal grain growth inhibiting force, there is a function of improving the magnetic flux density . Here, by preventing all Bi from disappearing from the steel at the time of the final finish annealing, it is possible to hold the suppressing force up to a high temperature range as compared with the conventional grain-oriented electrical steel sheet material. It is considered that the azimuth integration degree of <α> ≦ 6 ° can be improved. Also, by adding Bi to the steel, secondary recrystallized grains grow sufficiently in the direction perpendicular to the rolling, and as defined in the present invention, <L> is 30 to 30 times larger than a normal grain-oriented electrical steel sheet.
Values in the range of 300 mm are obtained. Therefore, Bi is preferably present in the ground iron of the product plate, and the Bi content is 0.0003 ma.
If less than ss%, a sufficient effect cannot be obtained. But Bi
If the amount exceeds 0.05 mass%, the hysteresis loss and the coating deteriorate, so the Bi content in the product sheet iron is preferably set to about 0.0003 to 0.05 mass%.

The area-weighted average value (<L>) of the maximum length of the secondary recrystallized grains in the direction perpendicular to the rolling direction is 30 to 300 mm. The [001] axis of the secondary recrystallized grains which is closest to the rolling direction. Area-weighted average (<α>) of the angle between the material and the rolling direction in the rolling plane: <6 ° or less As shown in FIG. 3 described above, the area-weighted average of the α angle of the secondary recrystallized grains <α> By lowering the area weighted average <L> of the maximum length in the direction perpendicular to the rolling sufficiently,
The occurrence of non-uniform magnetic flux density due to the shift of the α angle between the secondary recrystallized grains is suppressed, and the iron loss is reduced. Here, <α> needs to be 6 ° or less in order to make the magnetic flux density distribution uniform, and if it exceeds 6 °, the effect of uniformizing the magnetic flux distribution is not sufficient, leading to deterioration of iron loss. 6 °
Limited to the following. On the other hand, even if <α> is 6 ° or less,
If <L> is less than 30 mm, the distribution of the local magnetic flux density becomes non-uniform and iron loss is deteriorated. When <L> exceeds 300 mm, not only does the effect of uniformizing the magnetic flux distribution become saturated, but also secondary grains having poor crystal orientations grow and iron loss deteriorates. Limited to the range of 30 to 300 mm. Here, as a method of obtaining <α>, the direction and area of each crystal grain are measured and weighted and integrated, and the direction is measured at measurement points provided in a lattice shape in the steel sheet, and a simple average of these is taken. There are methods.

Average value of standard deviation (<σ (β)>) of the angle formed by the [001] direction of the secondary recrystallized grains with the rolling surface in the direction perpendicular to the rolling direction (<σ (β)>): 2 ° or less β in the direction perpendicular to the rolling direction of the steel strip Average of standard deviation of angle (<σ
Limiting (β)>) to 2 ° or less is an important requirement of the present invention, and by satisfying this requirement, as described with reference to FIG. Eddy current loss due to waveform distortion due to the phase shift of the above can be prevented. The phase shift of the magnetic flux waveform can be reduced by reducing the difference in the magnetic domain width in the direction perpendicular to the rolling direction of the steel sheet, and in order to achieve this object, the variation in the β angle in the direction perpendicular to the rolling direction is reduced. And the variation of the β angle can be quantified by <σ (β)>. When trying to obtain a further low iron loss under the condition that the peak value of the local magnetic flux density is optimized by the appropriate control of <α> and <L>, the distortion of the local magnetic flux waveform is also reduced at the same time. It is effective to limit <σ (β)> to 2 ° or less. Here, if <σ (β)> is larger than 2 °, a waveform distortion due to a phase shift of the local magnetic flux waveform occurs, and the overall iron loss deteriorates.
<Σ (β)> ≦ 2 °.

In order to determine <α> and <σ (β)>, it is necessary to measure the distribution of crystal orientation in the steel sheet. The measurement interval is 5 to 30 mm in the direction perpendicular to the rolling direction. ,
It is preferably 5 to 100 mm in the rolling direction. The measurement area may be about 200 to 800 mm in the direction perpendicular to the rolling direction and about 200 to 800 mm in the rolling direction. The measurement value of <σ (β)> slightly changes due to the difference in the measurement interval and the measurement region, but does not significantly affect the limited range of the present invention.

The effect of reducing iron loss by <σ (β)> is exhibited regardless of the presence or absence of the magnetic domain refining process. This is because, as a method of the artificial magnetic domain refining treatment, a method of providing a linear groove almost perpendicular to the rolling direction on the surface of the grain-oriented electrical steel sheet, or a method of introducing a linear strain by laser or plasma flame, etc. However, in these methods, the magnetic domain width cannot be said to be completely subdivided because the magnetic permeability is deteriorated. In other words, it is actually impossible to extremely push the magnetic domain subdivision in order to make the magnetic domain width uniform in all portions, because this causes deterioration of the magnetic permeability. Therefore, the non-uniformity of the magnetic domain width due to the β angle is a factor that increases iron loss even in a magnetic domain-oriented magnetic steel sheet. In order to completely eliminate this, it is necessary to appropriately control <σ (β)>. Is important.

Next, the reasons for limitation regarding the method for producing a grain-oriented electrical steel sheet of the present invention will be described. First, the reasons for limiting the slab components will be described. C: 0.03 to 0.10 mass% C is not only an element useful for improving the hot-rolled structure by utilizing transformation, but also an element useful for generating Goss-oriented crystal grains, and at least 0.03 mass%. However, C content is limited to the range of 0.03 to 0.10 mass%, since if it exceeds 0.10 mass%, decarburization failure occurs in decarburization annealing.

Si: 2.0 to 5.0 mass% Si is an element necessary for increasing the electrical resistance of the product plate to reduce iron loss, and stabilizing α of iron to enable high-temperature heat treatment. At least 2.0 mass% is required, but if it exceeds 5.0 mass%, cold rolling becomes difficult.
Limited to 2.0-5.0 mass%.

Mn: 0.04 to 0.15 mass% Mn not only effectively contributes to the improvement of hot brittleness of steel, but also forms precipitates such as MnS and MnSe when S and Se are mixed. It functions as an inhibitor. However, when the amount of Mn is less than 0.04 mass%, the above effect is insufficient.On the other hand, when the amount of Mn exceeds 0.15 mass%, the particle size of precipitates such as MnSe becomes coarse and the effect as an inhibitor is lost. It was limited to the range of 0.04 to 0.15 mass%.

S and / or Se: 0.005 to 0.040 mass
% Se and S combine with Mn and Cu to form MnSe, MnS, Cu _2-x S
e, is a useful component that forms Cu _2-x S and exhibits an inhibitory action as a dispersed second phase in steel. These Se, S
If the total content of is less than 0.005 mass%, the effect of the addition is poor. On the other hand, if it exceeds 0.040 mass%, not only the solid solution during slab heating becomes incomplete, but also the cause of defects on the surface of the product plate Therefore, the content is limited to the range of 0.005 to 0.040 mass% in either case of single addition or composite addition.

Sol.Al: 0.015 to 0.035 mass% Al is a useful element that forms AlN in the steel and acts as an inhibitor as a dispersed second phase. Enables appropriate control of recrystallized grains. However, if the content is less than 0.015 mass%, the amount of AlN deposited cannot be sufficiently ensured.
%, AlN precipitates coarsely and loses its effect as an inhibitor.
The content was set in the range of 0.035 mass%.

Sol.Al: 0.015 mass% or less, B: 0.0010-
0.0100 mass% BN is a precipitate having an inhibitory effect equivalent to that of AlN, and when used simultaneously with Bi, effectively acts on controlling the morphology of secondary recrystallized grains. However, the B content is 0.0010
If it is less than mass%, the amount of BN deposited is not sufficiently ensured. On the other hand, if it exceeds 0.0100 mass%, BN coarse precipitates to deteriorate the magnetic properties of the product sheet.
The range was limited to 0.0100 mass%. Here, in order to obtain fine precipitation and dispersion of BN, if Al is present simultaneously, AlN
And BN tends to be unevenly deposited. Therefore, BN
Al is desirably 0.015 mass% or less in order to further enhance the effect of B. Therefore, when B is contained, sol.
Al was limited to a range of 0.015 mass% or less.

N: 0.003 to 0.013 mass% N is an element necessary for forming a precipitated dispersed phase of AlN or BN, and 0.003 to 0.013 mass% is added to make AlN or BN function well as an inhibitor. Need to be done. Because if the amount added is less than 0.003mass%
The precipitation of AlN and BN becomes insufficient, and the addition amount is 0.013
If the amount exceeds mass%, swelling or the like occurs during slab heating.

Bi: 0.001 to 0.070 mass% Bi preferentially concentrates at the grain boundaries of the primary recrystallized grains and lowers the mobility of the grain boundaries during final finish annealing to lower the secondary recrystallization temperature. It is considered that the effect is improved by increasing the crystal orientation. As a result, the α angle of the secondary recrystallized grains is reduced, and it is possible to form a secondary grain structure that achieves <α> ≦ 6 °. Further, as described above, by leaving Bi in the steel up to the high temperature range of the final annealing and not completely purifying it from the steel, the growth property of secondary recrystallization in the direction perpendicular to the rolling is increased, and this is defined in the present invention. A secondary recrystallized grain structure having <L> can be formed. Therefore, good magnetic properties can be obtained by leaving an appropriate amount of Bi remaining in the base steel after the final finish annealing. However, when the amount of Bi is less than 0.001 mass%, disappearance from the steel occurs early and desired secondary recrystallized grains cannot be obtained.
If added in excess of mass%, the residual amount in the product sheet steel will be excessive and the hysteresis loss will deteriorate.
Limited to the range of 1 to 0.07 mass%.

Cr and / or Cu: 0.05 to 1.0 mass% In a material containing Bi in the material, the forsterite film formed on the steel sheet surface is deteriorated by the final finish annealing, but Cr and Cu are added to the steel. By doing so, it is possible to improve the appearance of the coating film, whereby a sufficient tension is applied to the steel sheet surface, thereby contributing to a reduction in iron loss. It is considered that such an effect of Cr and Cu is caused by a change in the structure of a subscale mainly composed of SiO ₂ generated on the surface of the steel sheet by decarburizing annealing.
In addition, Cu, like Mn, is also useful as an element that combines with Se or S to form precipitates and increase the suppressing power.
It is remarkable in the range of 0.05 to 0.50 mass%. When the content of Cr or Cu is less than 0.05 mass%, the above-mentioned effect of improving the film cannot be obtained. On the other hand, when the content exceeds 1.0 mass%, carbides, nitrides of Cr or sulfides of Cu, selenides are used. Is coarsely precipitated, lowering the suppressing power and deteriorating the magnetic properties. Therefore, it is contained in the above range in either case of single addition or composite addition.

Although the basic components have been described above, Sb, As, Mo, P, Sn, Ge,
The addition of Te, V, Nb, etc., alone or in combination is effective for further improving the magnetic properties. Sb,
As has the effect of increasing the suppressing power by segregating at the grain boundaries similarly to Bi, and it is desirable to add As in any range of 0.001 to 0.10 mass%. Mo has the effect of sharpening the nuclei of secondary grains to the Goss orientation, and the effect is remarkable in the range of 0.001 to 0.20 mass%. P, like Sb, is an element that segregates at the grain boundaries to increase the suppressing power. However, if it is less than 0.010 mass%, the effect of addition is poor, and if it exceeds 0.030 mass%, the magnetic properties and surface properties become unstable. , 0.010-0.030 ma
ss% is preferable. Sn and Ge are components effectively acting to reduce iron loss by increasing the generation frequency of secondary recrystallized grains, and both are preferably contained in the range of 0.005 to 0.20 mass%. Te, V, Nb is MnT
By forming precipitates such as e, VN, NbN, NbC, etc., they have the function of further increasing the ability to suppress normal grain growth, and are desirably added in the range of 0.005 to 0.10 mass%.

Next, the reasons for limiting the method for producing a grain-oriented electrical steel sheet of the present invention will be described.・ Amount of strain of decarburized annealed sheet: 0.01 ≦ (W′−W) /W≦0.15 After decarburizing annealing, Bi is introduced into steel by introducing micro-strain into the decarburized annealed sheet until it is wound on a coil. The growth of secondary recrystallized grains of the material contained in the steel in the direction perpendicular to the rolling direction is sufficiently ensured, and the fluctuation of the β angle in the direction perpendicular to the rolling direction can be reduced. The amount of strain for obtaining such an effect is suitably determined by the iron loss W _10/50 of the decarburized annealed plate.
Good magnetic properties can be obtained when (W'-W) / W is in the range of 0.01 to 0.15. When (W′−W) / W is less than 0.01, a desired β angle distribution cannot be obtained because the amount of strain of the decarburized annealed plate is insufficient. On the other hand, if it exceeds 0.15, the amount of strain becomes excessive and the generation of secondary grains having a poor crystal orientation is promoted, so that the magnetic properties deteriorate. For the above reasons, the strain amount of the decarburized annealed plate is 0.01 ≦ (W′−W) /W≦0.15 at the iron loss W _10/50 .
Limited to the range.

Here, the measurement of W _10/50 of the decarburized annealed sheet is as follows:
It can be measured with an SST (single-plate magnetic tester) or an Epstein tester under the condition of a magnetic flux sine wave. As a test piece size at the time of measurement, it is preferable to use a sample having a sample width of 50 mm or more in order to eliminate the influence of strain introduced into an edge portion by shearing. Note that the sample for measuring the iron loss value W after the introduction of the strain may be collected at any time immediately after being wound around the coil after the strain introduction process. For the iron loss W in the unstrained state, the sample after the introduction of strain was annealed in Ar at 700 ° C. for 30 minutes, then the temperature was reduced so that no strain was introduced, the internal strain was removed, and the iron loss was measured. Can be obtained. In addition to the above-described offline measurement, a method of continuously measuring a steel strip while winding it into a coil state is also applicable.After the steel strip exits the annealing furnace,
W is measured by laying a continuous iron loss measuring device before the maximum tension is applied, and after the maximum tension is applied, the continuous iron loss measuring device is laid before the coil is wound into a coil shape and W ′ is measured. It is possible to measure.

· Final cold-rolled sheet thickness: 0.1 to 0.5 mm · After the decarburizing annealing and before winding into a coil, bend the steel strip at a radius of curvature of 100 to 400 mm over 1/4 circumference or more. Processing to return to a flat state, followed by 20 to 110 MPa
The treatment for imparting tension in the rolling direction of the steel Bi is contained in the steel as the amount of strain measured at the iron loss _{W10 / 50} of the decarburized annealed sheet, and by securing the above amount, a desired product sheet can be obtained. . In order to secure such a distortion amount, a steel strip having a thickness of 0.1 to 0.5 mm is required to have a radius of curvature of 100 to 400 mm.
It is preferable to wind it around a 1 / 4-periphery or more around a mm cylinder, flatten it again, and then apply tension in the rolling direction with a tension of 20 to 110 MPa. If the radius of curvature in the case of the bending process is less than 100 mm, excessive strain is introduced and the magnetic properties are rather deteriorated. On the other hand, if the radius of curvature exceeds 400 mm, the effect is not exhibited because the amount of introduced strain is small. Such a bending process is applied to 1 /
By performing at least 4 circumferences (90 °), a desired amount of strain can be obtained over the entire width of the steel strip. Further, it is considered that the strain required for the entire width is uniformly introduced by performing a bending process and then flattening, so that the radius of curvature: 10
After the bending process of 0 to 400 mm, a process of returning to a flat state at least once is preferably performed. It is effective to perform such a winding process on rolls in a multiplex manner with a plurality of rolls after decarburizing annealing. At this time, in order to introduce an appropriate amount of strain to the steel sheet, the rolls of the plurality of rolls are required. The minimum value of the radius of curvature must be 100 mm or more and 400 mm or less.

Here, when the plate thickness is less than 0.1 mm, the introduction of strain is insufficient, while when it exceeds 0.5 mm, the amount of introduced strain becomes excessive and the magnetic characteristics are deteriorated. In addition, by making the axial direction of the roll performing the bending process perpendicular to the rolling direction of the steel sheet,
Uniform strain is introduced in the direction perpendicular to the rolling direction of the steel strip, and a desired secondary recrystallized structure is easily obtained. Such a bending process can be effectively performed by optimizing the radius of the pride roll, the steering roll, and the like. In addition, after such bending and unbending treatment, by applying a tension of 20 to 110 MPa in the rolling direction of the steel sheet, fine plastic strain is uniformly introduced into the entire steel sheet, and a desired secondary recrystallized structure is obtained. Will be able to If the tension here is less than 20 MPa, the amount of strain introduction is insufficient, while if it exceeds 110 MPa, the amount of strain introduction becomes excessive, leading to deterioration of magnetic properties.
It was limited to the range of Pa. Here, if the tension of the steel sheet changes from after decarburization annealing to coil winding, the maximum value of the tension is
It is good to be 20-110MPa.

Although the essential steps of the manufacturing method of the present invention have been described above, the magnetic properties can be further improved by using various conventionally known techniques. -Magnetic domain refining treatment In producing a grain-oriented electrical steel sheet by the above-described method, iron loss can be more effectively reduced by using a commonly known magnetic domain refining treatment in combination. The reason is that <L
This is because the uniformity of the peak value of the local magnetic flux waveform by the control of> and <α> contributes to the reduction of iron loss even after the magnetic domain refinement. Further, even in the magnetic domain refining material, the non-uniformity of the magnetic domain width in the direction perpendicular to the rolling direction due to the β angle is present to deteriorate the iron loss. It also works effectively to reduce iron loss of chemical materials. The heat-resistant magnetic domain subdivision method is to form grooves by etching in the final cold-rolled sheet or the steel sheet after final finish annealing, or to mechanically form grooves in the final finish annealed sheet or the plate after applying the insulation coating with a gear roll. A forming method and other groove forming techniques can be used. In addition, non-heat-resistant magnetic domain subdivision methods include:
A method of introducing strain by local heating using laser light or plasma can be used in combination. These exhibit a magnetic domain refining effect by being introduced linearly at an angle of 45 ° to 90 ° with respect to the rolling direction. The interval between the linear grooves (or strain regions) is preferably in the range of 1 to 50 mm.

Mirror-finish treatment Non-formation of forsterite film Normally, forsterite formed on the surface of a grain-oriented electrical steel sheet during final finish annealing,
It is known that it exerts a magnetic domain refining effect and has an effect of reducing eddy current loss, but has an effect of increasing hysteresis loss due to the development of anchors in the ground iron. Therefore, the hysteresis loss can be reduced by applying a coating having a tension-imparting effect and an insulating effect after the surface of the ground iron is mirror-finished. The present invention mainly reduces the eddy current loss by controlling the distribution of the magnetic flux density inside the steel sheet to an ideal state through control of the secondary recrystallized grains, and reduces the hysteresis loss due to the mirror surface treatment. By simultaneously performing the reduction, the iron loss can be reduced very effectively. In order to obtain a smooth ground iron surface, it is effective to remove oxides on the surface of the final finish annealing plate by mechanical polishing or pickling, and then to perform mirror finishing by pickling or electrolytic treatment. In addition, the use of a technique that does not form forsterite on the steel sheet surface in the final finish annealing and the application of a method that combines this with the above-mentioned mirror finishing treatment also effectively work to reduce iron loss. Examples of such a method include a method using alumina or the like as a refining agent, MgO
There is a method of adding a chloride therein, and any method is applicable.

As a method of forming an insulating / tensile film on the final finish annealed plate having a mirror-finished surface as described above, any conventionally known method such as an ion plantation method or a sol-gel method can be applied.

[0064]

EXAMPLES Example 1 A silicon steel slab having the composition shown by the symbols A to F in Table 3 was charged into a gas heating furnace, heated to 1230 ° C, held for 60 minutes, and further heated to 1400 ° C by induction heating. After heating for 40 minutes, a hot-rolled sheet having a thickness of 2.5 mm was formed by hot rolling. Then, hot rolled sheet annealing is performed at 1000 ° C for 1 minute, and after pickling, the thickness is reduced to 1.6 mm by primary cold rolling, and then intermediate annealing is performed at 1050 ° C for 1 minute. 0.23 by cold rolling
mm. Then, P (H
₂ O) / P (H ₂ ) = 0.50 atmosphere, after decarburizing annealing at 850 ° C for 100 seconds, wrapping 1/2 round around a 300 mm radius roll,
After making it flat, a tension of 39.2 MPa was continuously applied in the rolling direction of the steel strip, an annealing separator was applied, and the coil was wound. Here, as an annealing separator, 5 mass% of TiO ₂ was used.
%, The balance being substantially composed of MgO.
It was applied at a basis weight of g / m ² . Final finish annealing is 900 ~
The average heating rate at 1100 ° C is 15 ° C / h, and the maximum temperature is 12
00 ° C. × 10 hours. Next, after the unreacted annealing separator was removed by washing with water, an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was formed. Thereafter, a linear strain was introduced by irradiation with a plasma flame at an interval of 10 mm in the rolling direction and at an angle of 80 ° with the rolling direction, and the magnetic domain was subdivided. From the product sheet thus obtained, the length in the rolling direction: 500 mm, the width direction: 50
A 0 mm SST specimen was collected and subjected to magnetic measurement by SST. Table 4 shows the rate of change in iron loss of the decarburized annealed sheet (W'-W).
/ W × 100 (%), area-weighted average value <L> of the maximum length in the direction perpendicular to the rolling direction of the secondary recrystallized grains, area-weighted average value <α> of the α angle (absolute value), β angle in the width direction Mean values <σ (β)> of the standard deviation and magnetic properties before and after the magnetic domain refinement processing.

[0065]

[Table 3]

[0066]

[Table 4]

As shown in Table 4, the secondary recycling according to the present invention
In a product plate having a grain structure, W _17/50 0.80 W / kg
Hereinafter, in the magnetic domain refining material, W_17/50 Is 0.70 W / kg or less
Excellent magnetic properties are obtained.
For symbols C, D, E, and F where Bi was 0.0003 mass% or more
W_17/50 Excellent magnetic properties of less than 0.65 W / kg
Could be obtained.

Example 2 A silicon steel slab having the composition indicated by symbol E in Table 3 was charged into a gas heating furnace, heated to 1230 ° C., held for 60 minutes, and further heated at 1400 ° C. for 40 minutes by induction heating. After heating, a hot-rolled sheet having a thickness of 2.2 mm was formed by hot rolling. Then 1100
A hot rolled sheet was annealed at 2 ° C. for 2 minutes, pickled, and then cold rolled to a final sheet thickness of 0.23 mm. After that, an angle with the rolling direction by resist etching treatment: 85 °, spacing: 4m
m, a width of 100 μm, and a depth of 15 μm were formed. Next, P (H ₂ O) / P (H ₂ ) of the atmosphere in the soaking process is 0.55.
After decarburizing annealing at 830 ° C for 100 seconds in an atmosphere of 1, the steel strip is conveyed while being wound around multiple rolls for 1/4 turn or more, then flattened, and tension is continuously applied in the rolling direction of the steel strip. After that, an annealing separating agent was applied and wound around a coil. Here, the diameter of the roll around which the steel strip was wound and the tension in the rolling direction after flattening the steel strip were changed as shown in Table 5. As the annealing separator, TiO ₂ : 7 mass%, Sr (OH) ₂ :
A coating material containing 2 mass% and the balance substantially consisting of MgO was applied at a basis weight of 7 g / m ² . The final finish annealing was performed at an average heating rate of 900 ° C. to 1100 ° C. at 20 ° C./h and a maximum temperature of 1200 ° C. × 10 hours. After that, the unreacted annealing separator was removed by washing with water, and an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was applied to obtain a product plate. From the product sheet thus obtained, the length in the rolling direction: 500 mm, the width direction: 500 mm
The SST specimens were sampled and subjected to magnetic measurement by SST. Table 5 shows the radius of the roll subjected to the bending treatment, the tensile tension,
Rate of change of iron loss of decarburized annealed sheet (W'-W) / W x 100
(%), The area weighted average value <L> of the maximum length in the direction perpendicular to the rolling direction of the secondary recrystallized grains, the area weighted average value <α> of the α angle (absolute value), and the standard deviation of the β angle in the width direction. Average value <σ
(Β)>, the magnetic flux density B ₁₀ , and the iron loss W _17/50 .

[0069]

[Table 5]

As shown in Table 5, by introducing appropriate strain into the decarburized annealed sheet according to the present invention, the iron loss W
Extremely good magnetic properties with _17/50 below 0.65 W / kg were obtained.

Example 3 Silicon steel slabs having various component compositions shown in Table 6 were charged into a gas heating furnace, heated to 1230 ° C., held for 60 minutes, and further heated at 1400 ° C. for 30 minutes by induction heating. After heating,
A hot-rolled sheet having a thickness of 2.7 mm was formed by hot rolling. Then 95
After subjecting to hot-rolled sheet annealing at 0 ° C for 1 minute, pickling, primary cold rolling to a thickness of 1.9 mm, intermediate annealing at 1050 ° C for 1 minute, pickling, and secondary cold rolling The final thickness was 0.23 mm by rolling. Then, P (H ₂ O) / P (H ₂ )
After decarburizing annealing at 830 ° C for 100 seconds in an atmosphere of 0.45, wind it onto a bridle roll with a radius of 200 mm for 1/2 turn or more, flatten it, and then continue 68.6 M in the rolling direction of the steel strip.
After applying a tension of Pa, the incinerated separating agent was applied and wound around a coil. BiCl ₃ : 5mass
%, The balance being substantially composed of MgO,
It was applied at a basis weight of 7 g / m ² per side. In the final finish annealing, the average heating rate at 900 to 1100 ° C was 12 ° C / h, and the maximum temperature was 1200 ° C for 10 hours. Next, after the unreacted annealing separating agent was removed by washing with water, an insulating tension coating mainly composed of aluminum phosphate containing colloidal silica was formed. Thereafter, a plasma jet was linearly irradiated at an angle of 75 ° with respect to the rolling direction and at an interval of 5 mm in the rolling direction to perform a magnetic domain refining treatment. From the product sheet thus obtained, an SST specimen having a length in the rolling direction: 500 mm and a length in the direction perpendicular to the rolling direction: 500 mm was sampled and subjected to magnetic measurement by SST. Table 7 shows the rate of change in iron loss (W′−W) / W × 100 (%) of the decarburized annealed sheet, the area weighted average value <L> of the maximum length in the direction perpendicular to the rolling direction of the secondary recrystallized grains, α
Area-weighted average <α> of angle (absolute value), average <σ (β)> of standard deviation of β angle in width direction, magnetic flux density B ₁₀ , iron loss W
_17/50 and the results of examining the coating appearance are shown.

[0072]

[Table 6]

[0073]

[Table 7]

As shown in Table 7, in the _grain- oriented electrical steel sheet of the present invention, a product sheet having excellent magnetic properties with a W _17/50 of less than 0.65 W / kg was obtained. Symbols C, D, F, containing 0.0003 mass% or more of Bi in iron
G, H, I, J, in K, product sheets having excellent magnetic properties when W _17/50 is below 0.60 W / kg is obtained. Also,
Symbols B, C, D, F, G, H, I, J, L, N, O and P containing Cu or Cr in the range of 0.05 to 1.0 mass%
Shows that a good coating appearance is obtained.

[0075]

As described above, according to the present invention, it is possible to obtain a grain-oriented electrical steel sheet which is stable on an industrial scale and has excellent magnetic properties, especially excellent iron loss properties. Perform great achievements.

[Brief description of the drawings]

FIG. 1 shows a method of deriving an area weighted average <L> of the maximum length of a secondary recrystallized grain in a direction perpendicular to the rolling direction and an area weighted average <α> of an α angle (absolute value) of a secondary recrystallized grain. FIG.

FIG. 2 shows the area weighted average <L> of the maximum length of the secondary recrystallized grains in the direction perpendicular to the rolling direction and the area weighted average <α> of the α angle (absolute value) of the secondary recrystallized grains. ₉ is a graph showing the effect on _17/50 .

FIG. 3 is an explanatory diagram of an influence of a length of a secondary recrystallized grain in a direction perpendicular to the rolling direction on a local magnetic flux density distribution.

FIG. 4 is an explanatory diagram of an influence of an α angle of a secondary recrystallized grain on a local magnetic flux density distribution.

FIG. 5 is a diagram showing a local magnetic flux density waveform in a case where regions having different magnetic domain widths exist in a direction perpendicular to the rolling direction of the steel strip.

FIG. 6: Average value of standard deviation of β angle in the direction perpendicular to rolling <σ
It is a schematic diagram which shows the derivation method of (beta)>.

FIG. 7: Average value of standard deviation of β angle in the direction perpendicular to rolling <σ
It is a graph which shows the relationship between (β)> and iron loss _{W17 / 50} .

FIG. 8 is a diagram showing a procedure for winding a steel strip around a cylinder (roll).

[Explanation of symbols]

 1 roll 2 steel strip 3 roll radius

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/16 H01F 1/16 B (72) Inventor Tadashi Tadashi Nakanishi 1-chome Mizushima Kawasaki-dori, Kurashiki City, Okayama Prefecture None) Mizushima Works, Kawasaki Steel Corporation (72) Inventor Mitsumasa Kurosawa 1-chome, Mizushima Kawasaki-dori, Kurashiki City, Okayama Pref. PA06 5E041 AA02 AA19 CA02 CA04 HB05 HB07 HB11 NN01 NN06 NN17

Claims (7)

[Claims] 1. A grain-oriented electrical steel sheet containing 2.0 to 5.0 mass% of Si in a product sheet iron, wherein the area-weighted average value of the maximum length of secondary recrystallized grains in a direction perpendicular to the rolling direction is 30 mm or more.
300 mm or less, and the crystal orientation of the secondary recrystallized grains is as follows (1),
A grain-oriented electrical steel sheet having excellent magnetic properties, which satisfies the condition of equation (2). <Α> ≦ 6 ° --- (1) <σ (β)> ≦ 2 ° --- (2) where <α> is the rolling direction of the [001] axis of the secondary recrystallized grains. The area-weighted average value of the angle between the closest one and the rolling direction in the rolling plane. <Σ (β)>: Measure the angle β between the rolling surface and the [001] axis of the secondary recrystallized grains which is closest to the rolling direction in the rolling direction and the direction perpendicular to the rolling direction in the steel sheet, The standard deviation σ (β) of the distribution in the direction perpendicular to the rolling direction was obtained, and this was averaged in the rolling direction. 2. The grain-oriented electrical steel sheet according to claim 1, wherein the product sheet iron further has a composition further containing Bi: 0.0003 to 0.05 mass%. 3. C: 0.03 to 0.10 mass%, Si: 2.0 to 5.0 mass%, Mn: 0.04 to 0.15 mass%, S and / or Se: 0.005 to 0.040 mass%, sol.Al: 0.015 to 0.035 mass% , N: 0.003 to 0.013 mass% and Bi: 0.001 to 0.070 mass% A silicon steel slab having a composition containing, after heating, hot-rolled, and then combined with annealing and cold-rolling to obtain a final sheet thickness. After that, in a method for producing a grain-oriented electrical steel sheet comprising a series of steps of performing decarburizing annealing, then winding the coil, and then performing final finish annealing, the steel sheet is formed after the decarburizing annealing until the coil is wound. The micro-strain shall be introduced into the band, and the amount of strain to be introduced at that time shall be as follows.
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, wherein the method is adjusted to satisfy the expression (3). Note 0.01 ≦ (W′−W) /W≦0.15 --- (3) where, W: iron loss of the decarburized annealed plate before strain introduction W _10/50 W ′: after strain introduction and before coil winding Loss of decarburized annealed steel sheet W _10/50 4. C: 0.03 to 0.10 mass%, Si: 2.0 to 5.0 mass%, Mn: 0.04 to 0.15 mass%, S and / or Se: 0.005 to 0.040 mass%, sol.Al: 0.015 to 0.035 mass% , N: 0.003 to 0.013 mass% and Bi: 0.001 to 0.070 mass% A silicon steel slab having a composition containing, after heating, hot-rolled, and then combined with annealing and cold-rolling to obtain a final sheet thickness. After that, in a method for manufacturing a grain-oriented electrical steel sheet comprising a series of steps of performing decarburizing annealing, then winding the coil and performing final finishing annealing, the final cold-rolled sheet thickness is set to 0.1 to 0.5 mm, and decarburization is performed. Between the end of the annealing and the time the coil is wound around the coil, the steel strip has a radius of 10
Bending at least 1/4 turn to a cylinder of 0 mm or more and 400 mm or less and then returning to a flat state, followed by 20 to 11 in the rolling direction
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, comprising performing a treatment of applying a tension of 0 MPa. 5. C: 0.03 to 0.10 mass%, Si: 2.0 to 5.0 mass%, Mn: 0.04 to 0.15 mass%, S and / or Se: 0.005 to 0.040 mass%, sol.Al: 0.015 mass% or less, A silicon steel slab having a composition containing B: 0.0010 to 0.0100 mass%, N: 0.003 to 0.013 mass%, and Bi: 0.001 to 0.070 mass% is heated, hot-rolled, and then subjected to annealing and cold rolling. Combining the final sheet thickness, decarburizing annealing, then winding the coil, and then performing the final finishing annealing in a method for manufacturing a grain-oriented electrical steel sheet, comprising winding the coil after decarburizing annealing. In the meantime, the microstrain shall be introduced into the steel strip, and the amount of strain to be introduced at that time shall be as follows:
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, wherein the method is adjusted to satisfy the expression (3). Note 0.01 ≦ (W′−W) /W≦0.15 --- (3) where, W: iron loss of the decarburized annealed plate before strain introduction W _10/50 W ′: after strain introduction and before coil winding Loss of decarburized annealed steel sheet W _10/50 6. C: 0.03 to 0.10 mass%, Si: 2.0 to 5.0 mass%, Mn: 0.04 to 0.15 mass%, S and / or Se: 0.005 to 0.040 mass%, sol.Al: 0.015 mass% or less, A silicon steel slab having a composition containing B: 0.0010 to 0.0100 mass%, N: 0.003 to 0.013 mass%, and Bi: 0.001 to 0.070 mass% is heated, hot-rolled, and then subjected to annealing and cold rolling. After the final thickness is combined, the steel sheet is subjected to decarburization annealing, then wound into a coil, and then subjected to final finishing annealing. mm and between the end of the decarburization annealing and the winding of the steel strip to a radius of 10 mm.
Bending at least 1/4 turn to a cylinder of 0 mm or more and 400 mm or less and then returning to a flat state, followed by 20 to 11 in the rolling direction
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, comprising performing a treatment of applying a tension of 0 MPa. 7. The silicon steel slab according to claim 3, further comprising Cr and / or Cu: 0.05 to 1.0.
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by having a composition containing mass%.