JP6160649B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a method for producing a so-called grain-oriented electrical steel sheet in which crystal grains are Miller indices and {110} planes are accumulated on the plate surface and <001> orientation is accumulated in the rolling direction. The grain-oriented electrical steel sheet is a soft magnetic material and is mainly used as an iron core of electrical equipment such as a transformer.

It is known that grain oriented electrical steel sheets exhibit excellent magnetic properties by accumulating crystal grains in {110} <001> orientation (hereinafter referred to as Goth orientation) by secondary recrystallization annealing (for example, , See Patent Document 1).
And, as an index of magnetic characteristics, the main _component is iron loss W _17/50 per kg of steel plate when magnetized up to 1.7T with magnetic field strength: magnetic flux density B _{8 at} 800A / m and excitation frequency: 50Hz AC magnetic field. It is used for.

  One of the means for reducing iron loss in grain-oriented electrical steel sheets is to highly accumulate crystal grains after secondary recrystallization annealing in the Goth direction. In order to increase the Goss orientation accumulation degree after secondary recrystallization annealing, the grain boundary mobility difference is set so that only sharp Goss orientation grains grow preferentially, that is, the texture of the primary recrystallization plate. It is important to suppress the growth of recrystallized grains other than the Goss orientation by using a precipitate called an inhibitor.

Here, as a predetermined primary recrystallized structure in which only sharp goth-oriented grains can preferentially grow, {554} <225> -oriented grains and {12 4 1] <014> -oriented grains are known. By accumulating these oriented grains in a well-balanced and highly integrated manner in the matrix of the primary recrystallization plate, Goss oriented grains can be highly accumulated after the secondary recrystallization annealing.
For example, in Patent Document 2, in the primary recrystallization annealed plate, the texture near the surface layer of the steel plate is represented by Bunge's Euler angle from directions of φ ₁ = 0 °, φ = 15 °, φ ₂ = 0 °. Within 10 ° or the maximum orientation within 10 ° from the orientation of φ ₁ = 5 °, Φ = 20 °, φ ₂ = 70 °, and the texture of the central layer of the steel sheet is also indicated by Bunge's Euler angle In the case where the maximum orientation is within 5 ° from the orientation of φ ₁ = 90 °, Φ = 60 °, and φ ₂ = 45 °, a secondary recrystallized annealing plate showing stable and excellent magnetic properties can be obtained. It is disclosed.

As an inhibitor utilization technique, for example, Patent Document 1 discloses a method using AlN and MnS, and Patent Document 3 discloses a method using MnS and MnSe, both of which are industrially put into practical use. .
In the method using these inhibitors, uniform fine dispersion of the inhibitor is an ideal state, but in order to achieve this, slab heating before hot rolling must be performed at a high temperature of 1300 ° C. or higher. However, excessive coarsening of the slab crystal structure occurs with high-temperature slab heating. The slab structure is the {100} <011> direction, which is mainly a hot-rolling stable direction, and such coarsening of the slab structure results in significant inhibition of secondary recrystallization and greatly deteriorates magnetic properties. Cause. For this reason, in a high-temperature slab heating type grain-oriented electrical steel sheet using an inhibitor, about 0.03 to 0.08% of C is contained in the material for the purpose of destroying a coarse slab structure by utilizing α-γ transformation during hot rolling. It is essential. Nonetheless, if C remains in the product plate, the magnetic properties of the product plate will be significantly deteriorated. Therefore, decarburization annealing is performed in any process after hot rolling, and the C content in the product plate is reduced to about 0.003% or less. Reduction is also essential.

  Thus, in the manufacturing method of the grain-oriented electrical steel sheet using the conventional inhibitor, it requires a lot of energy for high-temperature slab heating, and requires a decarburization annealing process, which increases the manufacturing cost. There was a problem.

In order to solve the above problem, for example, in Patent Document 4, the slab heating temperature is set to a low temperature of 1200 ° C. or less, and in the slab heating stage, an inhibitor-forming element such as Al, N, Mn, S or the like is introduced into the steel. (Al, Si) after decarburization annealing and annealing in a strongly reducing atmosphere, for example, in a mixed atmosphere of NH ₃ and H ₂ , while annealing the steel plate A so-called nitriding treatment technique has been disclosed in which an inhibitor having N as a main composition is formed so that a magnetic property equivalent to that of high-temperature slab heating is exhibited even in low-temperature slab heating.

Patent Document 5 discloses that for a silicon steel slab containing C ≦ 0.02%, the rough hot rolling start temperature is set to 1250 ° C. or lower, the cumulative rolling reduction at 900 ° C. or higher is 80% or higher, and at least one pass is 35%. Disclosed is a method of breaking the slab structure even in low-C materials by performing strain accumulation rolling so that the cumulative reduction ratio at 900 ° C. or lower is 40% or higher after recrystallization hot rolling by applying a reduction of more than 50%. Has been.
However, this method does not cause high-temperature slab heating even though it contains an inhibitor element such as Al or N, so that fine precipitation of the inhibitor does not occur, and nitriding as described above is also performed. Therefore, there is a problem that the primary recrystallized grain growth inhibiting ability is insufficient and the magnetic characteristics are deteriorated. In addition, since there is no regulation in the cooling conditions after annealing before the final cold rolling, the amount of solid solution elements (C, N, etc.) could not be controlled.

Furthermore, in Patent Document 6, for a silicon steel slab containing C: 0.0005 to 0.004%, rough hot rolling is started in a temperature range of 1000 ° C to 1200 ° C, and if necessary, in a temperature range of 700 ° C to 1100 ° C. After annealing for a short time, cold rolling at least once with one or intermediate annealing in between, and heating the steel plate in the temperature range of 850 ℃ to 1050 ℃ for more than 1 second and less than 200 seconds. A method for performing nitriding is disclosed.
However, even in this method, although inhibitor elements such as Al and N are contained, high temperature slab heating is not performed, so that fine precipitation of the inhibitor does not occur, and nitriding treatment as described above is also performed. Therefore, there is a problem that the primary recrystallized grain growth inhibiting ability is insufficient and the magnetic characteristics are deteriorated. In addition, since there is no regulation in the cooling conditions after annealing before the final cold rolling, there remains a problem in that the amount of solid solution elements (C, N, etc.) cannot be controlled.

On the other hand, in Patent Document 7, a technique for developing secondary recrystallization without including an inhibitor component in the slab is being studied, and a technique capable of causing secondary recrystallization without containing an inhibitor component ( Inhibitorless method) was developed. This inhibitorless method is a technology that uses secondary steel with higher purity and develops secondary recrystallization by texture (control of texture).
Inhibitorless method does not require slab heating at high temperature, and it is possible to produce grain-oriented electrical steel sheets at a low cost. As a result, there is a problem that the magnetic characteristics of the products are likely to vary.
In addition, in this technique, since control of the texture is an important factor, many techniques such as warm rolling for texture control have been proposed, but if this texture control cannot be performed sufficiently, Compared to the technique using an inhibitor, the degree of integration in the Goth direction after secondary recrystallization was low, and the magnetic flux density tended to be low.

Japanese Patent Publication No. 40-15644 JP 2001-60505 A Japanese Patent Publication No. 51-13469 Japanese Patent Laid-Open No. 5-1112827 Japanese Patent Laid-Open No. 57-114614 JP-A-6-346147 JP 2000-129356 A

Materials Transactions, Vol.54 No.01 (2013) pp.14-21

  As described above, for example, the conventional primary recrystallization texture control technique such as Patent Document 2 is a manufacturing technique of a high-temperature slab heating type (heating temperature: 1200 ° C. or more) using an inhibitor. For the purpose of destroying the structure of coarse slabs using the γ transformation, there is a restriction that it is essential to contain about 0.03 to 0.08% of C in the material, and a good range within the restriction is specified. It was just technology.

  The present invention solves the above-mentioned problem, without restricting the inclusion of a relatively large amount of C, it is possible to effectively grow goth-oriented grains to obtain good magnetic properties, and high yield, It aims at proposing the manufacturing method of the grain-oriented electrical steel sheet which has low cost and high productivity.

Now, in order to solve the above-mentioned problems, the inventors have made extensive studies by paying attention to the solute C amount of the steel sheet before the final cold rolling.
As a result, it has been found that the magnetic properties of the product plate are remarkably improved by reducing the solute C amount of the steel plate before the final cold rolling to the limit.
Specifically, the amount of C in the slab is limited to 0.0005% or more and 0.005% or less in terms of mass%, the amount of Si is limited to a range of 2.0 to 4.5% in mass%, and after the heating step immediately before the final cold rolling. By controlling the average cooling rate between 800 and 200 ° C within an appropriate range in relation to the amount of dissolved C and Si in the slag, the aging index AI (Aging Index) of the steel plate before final cold rolling is 70 MPa. It has become clear that the magnetic properties are improved.

  Further, by adjusting the temperature increase rate of primary recrystallization annealing to 10 ° C./s or more and 200 ° C./s or less, {554} <225 with respect to the random strength of the texture of the central layer of the thickness of the primary recrystallization annealing plate. > The strength ratio was 12 or more, and the ratio of {554} <225> strength to {111} <110> strength could be 7 or more, and it was revealed that the magnetic characteristics were further improved.

As described above, in the manufacturing methods proposed so far, it may be difficult to stably realize good magnetic properties.
The present invention uses a component according to an inhibitorless component in which sol.Al is suppressed to less than 100 ppm, and precipitates silicon nitride (Si ₃ N ₄ ) instead of AlN by applying nitriding while avoiding high-temperature slab heating. Thus, by functioning as a suppressive force for normal grain growth, variation in characteristics is greatly reduced, and it is possible to produce a grain-oriented electrical steel sheet having industrially stable and good characteristics.

The present invention is based on the above findings, and the gist of the present invention is as follows.
1. In mass%, C: 0.0005 to 0.005%, Si: 2.0 to 4.5%, Mn: 0.005 to 0.3%, S and / or Se (total): 0.05% or less, sol. Al: less than 0.010%, N: (14.00 /26.98) x [% sol.Al] or more and 0.008% or less, the remainder of the steel slab composed of Fe and inevitable impurities is heated and then hot-rolled, and hot-rolled sheet annealed as necessary After the above, the grain thickness of the grain-oriented electrical steel sheet is obtained by a series of processes in which a final thickness is obtained by cold rolling at least once with intermediate or intermediate annealing, followed by primary recrystallization annealing and further secondary recrystallization annealing. In manufacturing,
Using the solid solution C amount parameter X calculated from the following equation (1), the average cooling rate R (° C./s) between 800 and 200 ° C. after the heating step immediately before the final cold rolling is expressed as (2) A method for producing a grain-oriented electrical steel sheet, wherein the aging index AI of the steel sheet before final cold rolling is set to 70 MPa or less by making the upper limit average cooling rate _RH or less calculated from the equation.
X = [% Si] /28.09+100 [% C] /12.01 (1)
R _H = 10 / X (2)
However, in the formula (1), [% M] indicates the content of M element (mass%)

2. By adjusting the average temperature increase rate between 500-700 ° C. of the primary recrystallization annealing to 10 ° C./s or more and 200 ° C./s or less, the random strength of the texture of the thickness center layer of the primary recrystallization annealing plate 2. The directional electromagnetic wave according to 1 above, wherein a ratio of {554} <225> intensity to 12 or more and a ratio of {554} <225> intensity to {111} <110> intensity is 7 or more Manufacturing method of steel sheet.

3. The steel slab is further in mass%, Ni: 0.005-1.5%, Sn: 0.005-0.50%, Sb: 0.005-0.50%, Cu: 0.005-1.5%, Cr: 0.005-0.10%, P: 0.005-0.50 % And Mo: 1 or 2 types or more selected from 0.005-0.50% are contained, The manufacturing method of the grain-oriented electrical steel sheet of said 1 or 2 characterized by the above-mentioned.

4). The steel slab further contains one or more kinds selected from Ti: 0.001 to 0.1%, Nb: 0.001 to 0.1%, and V: 0.001 to 0.1% by mass%. The manufacturing method of the grain-oriented electrical steel sheet as described in any one of 1-3.

5. The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 4, wherein an additional inhibitor treatment is performed at any stage from the primary recrystallization annealing to the secondary recrystallization annealing.

6). 6. The method for producing a grain-oriented electrical steel sheet according to 5, wherein a nitriding treatment is performed as the additional inhibitor treatment.

7). As the additional inhibitor treatment, one or more selected from sulfides, sulfates, selenides and selenates are added to the annealing separator applied to the steel plate before the secondary recrystallization annealing. The method for producing a grain-oriented electrical steel sheet according to 5 above.

8). The method for producing a grain-oriented electrical steel sheet according to any one of 1 to 7, wherein a magnetic domain refinement process is performed at any stage after the final cold rolling.

9. 9. The method for producing a grain-oriented electrical steel sheet according to 8, wherein the magnetic domain subdividing treatment is performed by electron beam irradiation on the steel sheet after the secondary recrystallization annealing.

Ten. 9. The method for producing a grain-oriented electrical steel sheet according to 8 above, wherein the magnetic domain refinement treatment is performed by laser irradiation of the steel sheet after the secondary recrystallization annealing.

According to the present invention, the primary recrystallized plate texture can be controlled so as to be strongly accumulated in the Goss direction in the product plate. Therefore, after the secondary recrystallization annealing, it has superior magnetic properties as compared with the conventional case. It becomes possible to manufacture a grain-oriented electrical steel sheet. In particular, even with a thin steel plate with a thickness of 0.23 mm for which it is difficult to achieve a high magnetic flux density, excellent magnetic properties such that the magnetic flux density B ₈ after secondary recrystallization annealing is 1.92 T or more can be obtained. it can.
In addition, by adjusting the average temperature increase rate between 500-700 ° C. of primary recrystallization annealing to 10 ° C./s or more and 200 ° C./s or less, excellent magnetic properties with a magnetic flux density B ₈ of 1.93 T or more can be obtained. Can do.
Further, when the additional inhibitor treatment is performed, extremely excellent magnetic properties such that the magnetic flux density B ₈ is 1.94 T or more and further 1.95 T or more can be obtained.
Moreover, it is possible to achieve an excellent iron loss characteristic in which the iron loss W _17/50 after the magnetic domain subdivision treatment is 0.70 W / kg or less.
Also noteworthy is the low cost by lowering the slab heating temperature, possibly eliminating decarburization annealing, and improving the product yield by uniform organization in the longitudinal direction, width direction and thickness direction of the coil. Can be achieved.
In addition, it is possible to manufacture an ultrathin material by reducing the rolling load due to the low C, and it is possible to further reduce the iron loss without increasing the cost.

It is the graph which showed the influence of the cooling rate after hot-rolled sheet annealing on the aging index AI of a hot-rolled sheet annealed sheet (steel sheet after hot-rolled sheet annealing and before final cold rolling). It is the graph which showed the influence of the aging index AI of a hot-rolled sheet annealing board to the random strength ratio with respect to the thickness center layer of a primary recrystallization annealing board. It is the graph which showed the influence of the aging index AI of the hot-rolled sheet annealing board on the magnetic flux density B8 of a product board. It is the graph which showed the influence of the temperature increase rate between 500-700 degreeC in the time of primary recrystallization annealing on the random strength ratio with respect to the thickness center layer of a primary recrystallization annealing board. It is the graph which showed the influence of the sheet thickness center layer to the random strength ratio of the primary recrystallization annealing board on magnetic flux density B8 of a product board.

Hereinafter, the present invention will be specifically described.
First, the experiment that led to the present invention will be described. In addition, unless otherwise indicated, "%" display regarding a steel plate component shall mean the mass%.
The balance is three types of steel consisting of Fe and inevitable impurities, Steel A (C: 0.0009%, Si: 2.91%, Mn: 0.08%, S: 0.003%, Se: 0.008%, sol.Al: 0.0057%, N : 0.0034%), Steel B (C: 0.0024%, Si: 3.44%, Mn: 0.07%, S: 0.004%, Se: 0.008%, sol.Al: 0.0062%, N: 0.0035%) and Steel C (C : 0.0042%, Si: 3.97%, Mn: 0.07%, S: 0.003%, Se: 0.008%, sol.Al: 0.0061%, N: 0.0033%) After heating to 1200 ° C, 2.3mm thickness Until hot rolled. Next, after hot-rolled sheet annealing at 1000 ° C for 60 s, after cooling between 800-200 ° C at an average cooling rate of 20-100 ° C / s, cold rolling to 0.23 mm thickness, then at 800 ° C for 30 s Primary recrystallization annealing was performed. The temperature rising rate between 500 and 700 ° C. during the primary recrystallization annealing was 30 ° C./s.
Next, after applying an annealing separator containing MgO as the main component to the steel sheet surface, secondary recrystallization annealing is performed at 1200 ° C for 50 hours, followed by application of phosphate-based insulation tension coating. Then, flattening annealing for the purpose of baking and flattening of the steel strip was performed to obtain a product, and a test piece under each condition was obtained.

FIG. 1 shows the results of examining the effect of the cooling rate after hot-rolled sheet annealing on the aging index AI (Aging Index) of a hot-rolled sheet annealed sheet (steel sheet before final cold rolling).
As for the aging index AI, a No. 5 tensile test piece was cut out from the full thickness sample of the steel sheet before the final cold rolling according to JIS Z 2241, and the initial strain rate was 1 × 10 ^-3 and the nominal strain was 7.5%. After pre-straining, heat treatment at 100 ° C for 30 minutes, perform tensile test again at initial strain rate of 1 × 10 ^-3 , and yield stress during post-annealing test (if yield point phenomenon occurs, lower yield point) ) To a value obtained by reducing the tensile stress when 7.5% pre-strain was applied.

Here, X shown in the following formula (1) is set as a solid solution C amount parameter, and using this X, an upper limit value R of an average cooling rate between 800 and 200 ° C. after hot-rolled sheet annealing of each steel sheet. _{When H} is set as shown in the following formula (2), the upper limit average cooling rate R _H of the present invention between 800 and 200 ° C. after annealing of the hot rolled sheet calculated from the steel compositions of steels A, B and C is They are 90 ° C / s, 70 ° C / s, and 57 ° C / s, respectively.
X = [% Si] /28.09+100 [% C] /12.01 (1)
R _H = 10 / X (2)
As shown in FIG. 1, the aging index AI decreased as the amount of material C decreased. And when the average cooling rate R between 800-200 degreeC after hot-rolled sheet annealing satisfy | fills R <= _RH , the aging index AI became 70 MPa or less.

Next, FIG. 2 shows {{}} <225> strength and {554} <225> strength of the center thickness layer of the primary recrystallization annealed plate (the steel plate after the primary recrystallization annealing). 111} <ratio to <110> strength) shows the results of examining the influence of the aging index AI of the hot-rolled sheet annealed sheet.
Regarding the crystal orientation of the primary recrystallized annealed plate, the thinned sample polished to the thickness center layer was etched with 10% nitric acid for 30 seconds and X-ray Schulz method (110), (200), (211) The surface was measured, ODF (Orientation Distribution Function) analysis was performed from the data, and the intensity of each crystal orientation was calculated. The analysis was performed by ADC (Arbitrarily Defind Cell) method using ResMat software Textools. As for the intensity ratio of {554} <225> orientation with respect to random intensity, (φ ₁ , Φ, φ ₂ ) = (90, 60, 45) in Bunge's Euler angle display, and intensity of {111} <110> orientation The ratio was (φ ₁ , Φ, φ ₂ ) = (60, 55, 45).
As shown in FIG. 2, as the aging index AI of the hot-rolled sheet annealed sheet decreases, the {554} <225> strength of the center thickness layer of the primary recrystallized annealed sheet increases, and the {554} <225> strength. To {111} <110> strength also increased.

Next, FIG. 3 shows the results of examining the influence of the aging index AI of the hot-rolled sheet annealing plate on the magnetic flux density B ₈ of the product plate.
As shown in FIG. 3, the magnetic flux density improved as the aging index AI of the hot-rolled sheet annealed plate decreased. In particular, the magnetic flux density B ₈ ≧ 1.92T was achieved by controlling AI ≦ 70 MPa.

Furthermore, the influence of the temperature rising rate during the primary recrystallization annealing was examined in detail.
Contains C: 0.0037%, Si: 3.26%, Mn: 0.08%, sol.Al: 0.004%, N: 0.0027%, S: 0.005% and Se: 0.017%, with the balance being Fe and inevitable impurities The slab was heated to 1180 ° C. and then hot-rolled to a thickness of 2.5 mm. Subsequently, after hot-rolled sheet annealing at 1000 ° C. for 60 s, 800 to 200 ° C. was cooled at an average cooling rate of 30 ° C./s. Here, when X = [% Si] /28.09+100 [% C] /12.01, the upper limit average cooling rate R _H (= 800 to 200 ° C.) after hot-rolled sheet annealing calculated from the steel composition. 10 / X) is 68 ° C./s. Next, after cold rolling to a thickness of 0.23 mm, primary recrystallization annealing was performed at 800 ° C. for 20 s. The rate of temperature increase between 500 and 700 ° C. during primary recrystallization annealing was varied in the range of 10 to 300 ° C./s.
Next, after applying an annealing separator containing MgO as the main component to the steel sheet surface, secondary recrystallization annealing is performed at 1220 ° C for 50 hours, followed by application of phosphate-based insulation tension coating. Then, flattening annealing for the purpose of baking and flattening of the steel strip was performed to obtain a product, and a test piece under each condition was obtained.

  FIG. 4 shows the primary effects on the ratio of the center thickness of the primary recrystallized annealing plate to the random strength ({554} <225> strength and the ratio of {554} <225> strength to {111} <110> strength). The result of having investigated about the influence of the temperature increase rate between 500-700 degreeC at the time of recrystallization annealing is shown.

  As shown in FIG. 4, the {554} <225> strength of the central thickness layer of the primary recrystallization annealed plate increases as the rate of temperature increase between 500 and 700 ° C. during the primary recrystallization anneal decreases. , {554} <225> strength to {111} <110> strength also increased. Further, by setting the temperature increase rate of primary recrystallization annealing to 200 ° C./s or less, the {554} <225> strength ratio is 12 or more, and the ratio of {554} <225> strength to {111} <110> strength. Was able to be 7 or more.

FIG. 5 shows the {111} strength ratio ({554} <225> strength and {554} <225> strength) of the thickness center layer of the primary recrystallization annealed plate on the magnetic flux density (B ₈ ) of the product plate. } <Ratio to <110> strength) The results of the investigation are shown.
As shown in the figure, the {554} <225> strength ratio is 12 or more and the ratio of {554} <225> strength to {111} <110> strength is 7 in the thickness center layer of the primary recrystallization annealed plate. with more became magnetic flux density (B ₈₎ ≧ 1.93T.

From the above results, in order to increase the magnetic flux density of the product plate, the cooling rate between 800-200 ° C. after the hot-rolled sheet annealing is controlled to be lower than the upper limit average cooling rate _RH calculated from the material C amount and the Si amount. By doing this, it became clear that the aging index AI of the steel sheet before the final cold rolling can be reduced, that is, it is important to reduce the amount of solute C.
In addition, the average temperature increase rate between 500 to 700 ° C. of primary recrystallization annealing is adjusted to 200 ° C./s or less, and the {554} <225> strength ratio is set to 12 in the thickness center layer of the primary recrystallization annealing plate. As described above, it is clear that the magnetic flux density can be further increased by setting the ratio of {554} <225> strength to {111} <110> strength to 7 or more.

As the aging index of the steel sheet decreases before the final cold rolling, that is, the amount of dissolved C decreases, the {554} <225> strength and {554} <225> strength {111} < The reason why the ratio of 110> intensity has increased is not necessarily clear, but the inventors consider as follows.
When the amount of material C is reduced, the amount of solid solution C in the grains is reduced and the amount of carbides precipitated at the grain boundaries is reduced, so that the grain boundary restraint force is reduced. As a result, the shear band during cold rolling is reduced. As a result, the local deformation region is reduced and a sharp cold-rolled texture is formed. Moreover, the aging index of the steel plate before the final cold rolling is controlled by controlling the cooling rate between 800-200 ° C. after the hot-rolled sheet annealing to the upper limit average cooling rate _RH calculated from the material C amount and the Si amount. As a result of effectively reducing AI, it is considered that {554} <225>, which is the main orientation, is sharpened in the primary recrystallization annealing.

By adjusting the temperature increase rate of the primary recrystallization annealing to 200 ° C./s or less, the {554} <225> strength of the primary recrystallization annealing plate and the {111} <110> strength of the {554} <225> strength The reason why the ratio to the ratio has increased is not necessarily clear, but the inventors consider as follows.
At the time of primary recrystallization annealing, it is known that recrystallization starts from an orientation with high accumulated energy because energy accumulated by rolling differs in each crystal orientation. Increasing the rate of temperature increase in primary recrystallization annealing acts in the direction to eliminate this accumulated energy difference, and the primary recrystallization texture is in the direction of randomization, and therefore has the opposite effect to the technical idea of the present invention. It will be. Therefore, it is clear that the rate of temperature rise is preferably on the low speed side, and in the present invention, a good primary recrystallization texture is formed when the rate of temperature rise between 500 and 700 ° C. is 200 ° C./s or less. . More preferably, the temperature between 500 and 700 ° C. is 10 ° C./s or more and 100 ° C./s or less. The lower limit of the temperature increase rate is preferably a rate at which primary recrystallization is completed in a short time, assuming continuous annealing, and is 10 ° C./s from this viewpoint.

Further, as the {554} <225> strength and {554} <225> / {111} <110> strength ratio of the primary recrystallized annealed plate increases, the secondary recrystallized annealed plate (steel plate after secondary recrystallized anneal) The reason why the magnetic flux density is improved is not necessarily clear, but the inventors consider as follows.
As described in Non-Patent Document 1, based on the secondary recrystallization theory based on the high energy grain boundary theory, a grain boundary having an orientation difference angle of 25 ° to 40 ° has a high mobility. That is, by forming a primary recrystallization texture having 25 ° to 40 ° with respect to the Goth orientation, a sharp Goth orientation is selected during the secondary recrystallization. The azimuth difference angle with respect to the Goth azimuth is 29.5 ° for {554} <225> and 46.0 ° for {111} <110>. On the other hand, the azimuth difference angle with respect to an azimuth rotated by 20 ° from the Goss azimuth about ND // <110> is 35.5 ° for {554} <225> and 36.6 ° for {111} <110>. In other words, the presence of {111} <110> primary recrystallized grains facilitates selection of orientation grains that deviate from the Goss orientation with respect to ND // <110> as the axis when selecting secondary recrystallization nuclei. Cause deterioration of magnetic properties. Therefore, it is considered essential to increase {554} <225> primary recrystallized grains and decrease {111} <110> in order to achieve high magnetic flux density of the secondary recrystallization annealed plate. It is done.

  At the time of primary recrystallization annealing, it is known that recrystallization starts from an orientation with high accumulated energy because energy accumulated by rolling differs in each crystal orientation. Increasing the rate of temperature increase in primary recrystallization annealing works to eliminate this accumulated energy difference, and primary recrystallization texture is in the direction of randomization, and therefore has the opposite effect to the technical idea of the present invention. become. Therefore, it is clear that the rate of temperature rise is preferably on the low speed side, and in the present invention, a good primary recrystallization texture is formed when the rate of temperature rise between 500 and 700 ° C. is 200 ° C./s or less. . On the other hand, the lower limit of the rate of temperature rise is preferably a rate at which primary recrystallization is completed in a short time assuming continuous annealing, and is 10 ° C./s from this viewpoint.

Moreover, in the component system having a sol.Al content of less than 0.01%, the variation in characteristics is suppressed by nitriding, and the reason why even better magnetic characteristics are manifested is not necessarily clear, but is considered as follows.
That is, in contrast to the conventional intragranular precipitation type inhibitor of AlN, in the present invention, silicon generally contained in the grain-oriented electrical steel sheet by about several percent is precipitated as silicon nitride (Si ₃ N ₄ ) by nitriding in an intermediate step, By using it as an inhibitor, the same grain growth inhibiting power is obtained regardless of the number of nitride-forming elements (Al, Ti, Cr, V, etc.). Silicon nitride, unlike (Al, Si) N, in which Si is dissolved in AlN, has poor consistency with the crystal lattice of steel and has a complex crystal structure with covalent bonds, so it is fine in the grains. It is known that it is extremely difficult to precipitate in the steel, and the steel according to the present invention also selectively precipitates at the grain boundaries. Moreover, compared with the conventional intragranular precipitation type of AlN, the amount of precipitation in the steel of the present invention using a large amount of silicon is also increased, and a uniform inhibition effect can be imparted over the entire length. It is considered that the characteristic variation is suppressed.

Hereinafter, the component composition of the steel slab which is a raw material will be described.
C: 0.0005% or more and 0.005% or less C is one of the characteristics in the present invention. As described above, from the viewpoint of improving the characteristics and omitting decarburization annealing, the lower the amount of C, the better. Therefore, the amount is limited to 0.005% or less. On the other hand, considering the cost increase due to the increased decarburization load at the time of component adjustment and modern refining technology, the practical content was set to 0.0005% as the lower limit. However, even when it exceeds 0.005%, after the precipitation treatment before the final cold rolling, specifically, annealing at 100 to 500 ° C. for a long time, the amount of solid solution C is reduced by performing slow cooling about the furnace cooling. If possible, the same effect as the present invention can be exhibited.

Si: 2.0% to 4.5%
Si is an extremely effective element for increasing the electrical resistance of steel and reducing eddy current loss that constitutes a part of iron loss. When Si is added to the steel sheet, the electrical resistance increases monotonously up to a content of 11%, but the workability is significantly reduced when the content exceeds 4.5%. On the other hand, if the content is less than 2.0%, the electric resistance becomes small and good iron loss characteristics cannot be obtained. Therefore, the Si content is set to 2.0% to 4.5%.

Mn: 0.005% to 0.3%
Mn combines with S and Se to form MnS and MnSe, and these MnS and MnSe act as an inhibitor that suppresses the growth of normal grains in the temperature rising process of secondary recrystallization annealing. However, if the amount of Mn is less than 0.005%, the absolute amount of the inhibitor is insufficient, so that the ability to suppress normal grain growth is insufficient. On the other hand, if the amount of Mn exceeds 0.3%, in order to completely dissolve Mn in the slab heating process before hot rolling, not only slab heating at high temperature is required, but also the inhibitor precipitates coarsely. In addition, the ability to suppress normal grain growth is reduced. Therefore, the Mn content is set to 0.005% or more and 0.3% or less.

S and / or Se (total): 0.05% or less S and Se combine with Mn to form an inhibitor, but if the total content of one or two species is less than 0.001%, the absolute amount as a trace inhibitor is S and Se are preferably contained in an amount of 0.001% or more because they are insufficient and the suppression of normal grain growth is insufficient. On the other hand, if the content exceeds 0.05%, de-S and De-Se are incomplete in secondary recrystallization annealing, which causes iron loss deterioration. Therefore, the total amount of one or two selected from S and Se is 0.05% or less. In addition, in order to exhibit the addition effect of S and Se more effectively, it is preferable to set it as 0.01% or more.

sol.Al: less than 0.010%
Al forms a dense oxide film on the surface, making it difficult to control the amount of nitridation during nitridation or inhibiting decarburization. Therefore, Al is suppressed to less than 0.010% in terms of sol.Al. . However, Al, which has a high oxygen affinity, can reduce the amount of dissolved oxygen in the steel by adding a small amount in steelmaking and reduce oxide inclusions that lead to deterioration of properties. It is preferable to contain 0.003% or more, and this can suppress deterioration of magnetic characteristics.

N: (14.00 / 26.98) × [% sol.Al] or more and 0.008% or less In the present invention, silicon nitride is precipitated, and therefore, N or more N deposited as AlN with respect to the amount of Al contained. It is important to contain in advance. Since AlN is bonded at a ratio of 1: 1, by adding N of 1 or more in atomic weight ratio, that is, (14.00 / 26.98) or more to Al content [% sol.Al], steel is contained. The trace amount N contained therein can be deposited as silicon nitride. On the other hand, since N may cause defects such as blisters during slab heating, it is necessary to suppress N to 0.008% or less. Desirably, it is 0.006% or less.

The basic components of the present invention have been described above. However, in the present invention, the following elements can be appropriately contained as necessary.
Ni: 0.005% to 1.5%
Since Ni is an austenite-forming element, Ni is a useful element for improving the hot rolled sheet structure and improving magnetic properties by utilizing the austenite transformation. However, if the content is less than 0.005%, the effect of improving the magnetic properties is small. On the other hand, if the content is more than 1.5%, the workability deteriorates and the plateability deteriorates, and the secondary recrystallization becomes unstable and magnetic. Since the characteristics deteriorate, Ni is set in the range of 0.005 to 1.5%.

Sn: 0.005% to 0.50%, Sb: 0.005% to 0.50%, Cu: 0.005% to 1.5%, Cr: 0.005% to 0.10%, P: 0.005% to 0.50% and Mo: 0.005% or more 0.50%
Less than
Sn, Sb, Cu, Cr, P and Mo are all useful elements for improving the magnetic properties. However, if the respective contents are less than the lower limit of the above range, the effect of improving the magnetic properties is poor. When the respective contents exceed the upper limit of the above range, secondary recrystallization becomes unstable, leading to deterioration of magnetic properties. Therefore, Sn is 0.005% to 0.50%, Sb is 0.005% to 0.50%, Cu is 0.005% to 1.5%, Cr is 0.005% to 0.10%, P is 0.005% to 0.50%, and Mo is 0.005. % To 0.50% or less, respectively.

Ti: 0.001% to 0.1%, Nb: 0.001% to 0.1% and V: 0.001% to 0.1%
Ti, Nb, and V are all elements that precipitate as carbides and nitrides and are effective in reducing solid solution C and N. However, if the respective contents are less than the lower limit of the above range, the magnetic properties are improved. On the other hand, if the respective contents exceed the upper limit of the above range, precipitates composed of the elements remaining on the product plate cause deterioration of iron loss. Accordingly, Ti is contained in the range of 0.001% to 0.1%, Nb is contained in the range of 0.001% to 0.1%, and V is contained in the range of 0.001% to 0.1%.

Next, the manufacturing method of this invention is demonstrated.
The steel slab having the above component composition is hot-rolled after slab heating. Slab heating temperature shall be 1200 ℃ or less. This is because as the slab heating temperature is lowered, the slab particle size is refined and the amount of accumulated strain during hot rolling increases, which is effective for refinement of the hot-rolled sheet structure.

After hot rolling, if necessary, the hot rolled sheet structure is improved by annealing the rolled sheet. The hot-rolled sheet annealing at this time is preferably performed under conditions of a soaking temperature: 800 ° C. or more and 1200 ° C. or less, and a soaking time: 2 s or more and 300 s or less.
If the soaking temperature of hot-rolled sheet annealing is less than 800 ° C., the improvement of the hot-rolled sheet structure is not complete, and an unrecrystallized portion remains, so that a desired structure may not be obtained. On the other hand, when the soaking temperature exceeds 1200 ° C, the dissolution of AlN, MnSe and MnS proceeds, the inhibitor repressing power is insufficient in the secondary recrystallization process, and the secondary recrystallization does not occur, resulting in deterioration of magnetic properties. Will cause. Therefore, it is preferable that the soaking temperature of the hot-rolled sheet annealing is 800 ° C. or more and 1200 ° C. or less.
Further, if the soaking time is less than 2 s, the high temperature holding time is short, and thus there is a possibility that an unrecrystallized portion remains and a desired structure cannot be obtained. On the other hand, when the soaking time exceeds 300 s, the dissolution of AlN, MnSe, and MnS proceeds, the effect of trace inhibitors weakens, and the heterogeneity of the structure before nitriding progresses, resulting in the magnetic properties of the secondary recrystallization annealed plate. Characteristics deteriorate. Accordingly, the soaking time for hot-rolled sheet annealing is preferably 2 s or more and 300 s or less.

When the intermediate annealing described later is not performed, the cooling treatment after the hot-rolled sheet annealing is one of the features of the present invention, and as described above, the cooling rate between 800 to 200 ° C. after the hot-rolled sheet annealing is set. In addition, by controlling the upper limit average cooling rate _RH or less calculated from the material C amount and the Si amount, the aging index AI of the steel plate before the final cold rolling can be reduced to 70 MPa or less. Characteristics can be obtained.
The temperature range where the average cooling rate during cooling should be controlled between 800-200 ° C. is because this temperature range is carbide (Fe ₃ C, ε-carbide, etc.) or nitride (AlN, Si ₃ N _4). This is because the solid solution of C and N can be effectively reduced by adjusting the average cooling rate in this temperature range.

In the present invention, since it is important to reduce the amount of solute C before the final cold rolling, hot rolling is not performed, and rolling is performed to the final thickness by one cold rolling (that is, intermediate annealing). In the case of not performing (3), it is important to reduce the amount of solute C in the hot rolled sheet. That is, in this case, the average cooling rate R (° C./s) between 800 to 200 ° C. after hot rolling may be controlled to be equal to or lower than the upper limit average cooling rate _RH calculated by the material C amount and the Si amount.

In the present invention, the hot-rolled sheet annealing is not performed, and the steel sheet may be rolled to the final sheet thickness by two or more cold rollings that sandwich the intermediate annealing. In this case, the intermediate annealing is preferably performed at a soaking temperature of 800 ° C. or more and 1200 ° C. or less and a soaking time of 2 s or more and 300 s or less based on the same idea as hot-rolled sheet annealing. Also in this case, the cooling rate between 800 and 200 ° C. after the intermediate annealing is set to the upper limit average cooling rate _RH calculated from the material C amount and the Si amount, so that the steel sheet before the final cold rolling The aging index AI can be reduced to 70 MPa or less, whereby good magnetic properties can be obtained.

As described above, in the present invention, when performing the intermediate annealing, the cooling rate between 800 to 200 ° C. after the intermediate annealing is set, and when performing the hot-rolled sheet annealing without performing the intermediate annealing, the cooling rate between 800 to 200 after the hot-rolled sheet annealing is performed. Cooling rate between 200 ° C, if neither intermediate annealing nor hot-rolled sheet annealing is performed, the average cooling rate between 800-200 ° C after hot rolling is the upper limit average cooling calculated from material C amount and Si amount The speed is _RH or less. That is, it is important to control the average cooling rate between 800 and 200 ° C. in the heating process immediately before the final cold rolling.

  For cold rolling, a better primary recrystallized annealed plate texture can be obtained by setting the reduction ratio in the final cold rolling to 80% or more and 95% or less.

After the cold rolling, primary recrystallization annealing is preferably performed at a soaking temperature of 700 ° C. or higher and 1000 ° C. or lower. Moreover, if this primary recrystallization annealing is performed, for example in a wet hydrogen atmosphere, it can also serve as the decarburization of a steel plate.
Here, if the soaking temperature in the primary recrystallization annealing is less than 700 ° C., there is a possibility that unrecrystallized portions remain and a desired structure cannot be obtained. On the other hand, when the soaking temperature exceeds 1000 ° C., secondary recrystallization of goth-oriented grains may occur. Therefore, the soaking temperature in the primary recrystallization annealing is preferably 700 ° C. or higher and 1000 ° C. or lower.

And about the temperature increase rate of primary recrystallization annealing, as above-mentioned experiment, a more favorable magnetic characteristic can be acquired by making between 500-700 degreeC into 10 degrees C / s or more and 200 degrees C / s or less. . Preferably, the temperature is between 500 and 700 ° C. on the low temperature increase rate side of 10 ° C./s to 100 ° C./s.
The reason why the temperature range for adjusting the heating rate is 500 to 700 ° C. is that this temperature range is a temperature range in which recrystallized grains are nucleated.

  Furthermore, in the present invention, a nitriding treatment can be applied as an additional inhibitor treatment at any stage from the primary recrystallization annealing to the secondary recrystallization annealing. This nitriding treatment includes gas nitriding in which heat treatment is performed in an ammonia atmosphere after primary recrystallization annealing, salt bath nitriding in which heat treatment is performed in a salt bath, plasma nitriding, and nitride containing an annealing separator. Well-known techniques such as making the secondary recrystallization annealing atmosphere a nitriding atmosphere can be applied.

  Thereafter, if necessary, after applying an annealing separator mainly composed of MgO to the steel sheet surface, secondary recrystallization annealing is performed. In the present invention, as an additional inhibitor treatment, one or more selected from sulfides, sulfates, selenides, and selenates can be added to the annealing separator. The additive decomposes during the secondary recrystallization annealing and then sulphides and selenium in the steel, resulting in an inhibition effect. There is no restriction | limiting in particular also about the annealing conditions of secondary recrystallization annealing, What is necessary is just to perform on conventionally well-known annealing conditions. If the annealing atmosphere at this time is a hydrogen atmosphere, it can also serve as a purification annealing. Then, a desired grain-oriented electrical steel sheet is obtained through an insulating coating application process and a planarization annealing process. There are no special rules for the manufacturing conditions of the insulating coating application step and the planarization annealing step at this time, and it is sufficient to follow a conventional method.

  The grain-oriented electrical steel sheet produced by satisfying the above conditions has a very high magnetic flux density after secondary recrystallization, and also has low iron loss characteristics. Here, having a high magnetic flux density indicates that only the orientation in the vicinity of Justgoth preferentially grew in the secondary recrystallization process. Since it is known that the growth rate of secondary recrystallized grains increases near the Justgos, increasing the magnetic flux density indicates that the secondary recrystallized grain size is potentially coarsened. This is advantageous from the viewpoint of reducing hysteresis loss, but disadvantageous from the viewpoint of reducing eddy current loss.

Therefore, in order to solve such a conflicting phenomenon with respect to the final goal of iron loss reduction in the present technology, it is preferable to perform magnetic domain subdivision processing. Appropriate magnetic domain refinement treatment for this technology reduces eddy current loss that was disadvantageous due to coarsening of the secondary recrystallization grain size, and at the same time reduces hysteresis loss to obtain extremely low iron loss characteristics be able to.
As the magnetic domain refinement treatment, all known heat-resistant or non-heat-resistant magnetic domain refinement treatments can be applied, but if a method of irradiating the surface of the steel sheet after secondary recrystallization annealing with an electron beam or a laser is used, the steel sheet Since the magnetic domain refinement effect can be penetrated to the inside of the plate thickness, iron loss characteristics that are extremely lower than those of other magnetic domain refinement processes such as an etching method can be obtained.

Example 1
A steel slab having the composition shown in Table 1 was heated to 1150 ° C. and then hot-rolled to a thickness of 2.3 mm. Next, after annealing at 1020 ° C for 60s, after cooling at 800-200 ° C at an average cooling rate of 30 ° C / s, cold rolling to 0.23mm thickness, and then re-priming for 10s at 820 ° C Crystal annealing was performed. The temperature rising rate between 500-700 ° C. during the primary recrystallization annealing was 20 ° C./s.
Next, after applying an annealing separator containing MgO as the main component to the steel sheet surface, secondary recrystallization annealing is performed at 1180 ° C for 50 hours, followed by application of phosphate-based insulation tension coating. The product was subjected to flattening annealing for the purpose of baking and flattening of the steel strip.
The results of examining the magnetic properties of the product plate thus obtained are also shown in Table 1. Table 1 also shows the results of examining the aging index AI of the steel sheet before the final cold rolling, that is, the hot-rolled sheet annealed sheet, and the texture of the sheet thickness center layer after the primary recrystallization annealing.

As shown in Table 1, the aging index AI of the steel sheet before the final cold rolling, that is, the hot-rolled sheet annealed sheet, is set to 70 MPa or less, and the texture of the thickness center layer of the primary recrystallized annealed sheet is expressed as a random strength ratio. By setting {554} <225> strength ≧ 12 and {554} <225> strength / {111} <110> strength ≧ 7, the magnetic flux density B ₈ ≧ 1.92T of the secondary recrystallization annealed plate is achieved. We were able to.

(Example 2)
In Table 1, No. 2 and No. 4 steel slabs were heated to 1150 ° C. and then hot-rolled to various thicknesses shown in Table 2. Next, after annealing the hot rolled sheet at 1020 ° C for 60s, after cooling at 800 ° C to 200 ° C at an average cooling rate of 10 ° C / s, cold rolling to 0.20mm thickness, and then re-priming at 820 ° C for 120s Crystal annealing was performed. The heating rate between 500 and 700 ° C. during the primary recrystallization annealing was 40 ° C./s.
Next, after applying an annealing separator containing 10 parts by mass of MgSO ₄ to 100 parts by mass of MgO and MgO on the surface of the steel sheet, secondary recrystallization annealing is performed at 1180 ° C. for 50 hours. Subsequently, the product was subjected to flattening annealing for the purpose of applying a phosphate insulating tension coating, baking and flattening the steel strip.
The results of examining the magnetic properties of the product plate thus obtained are also shown in Table 2. Table 2 also shows the results of examining the aging index AI of the hot-rolled sheet annealed sheet and the texture of the sheet thickness center layer after the primary recrystallization annealing.

As shown in Table 2, the AI value of the steel sheet before the final cold rolling, that is, the hot-rolled sheet annealed sheet, is set to 70 MPa or less, and the texture of the center thickness layer of the primary recrystallized annealed sheet is expressed as a random strength ratio {554 } <225> strength ≧ 12 and {554} <225> strength / {111} <110> strength ≧ 7 can achieve the magnetic flux density B ₈ ≧ 1.95T of the secondary recrystallization annealed plate. did it. Furthermore, as the final cold rolling reduction increases, not only the {554} <225> strength of the thickness center layer of the primary recrystallization annealed plate but also the {554} <225> strength / {111} <110> strength. The ratio increased significantly, and the magnetic flux density B ₈ of the secondary recrystallization annealed plate also increased significantly with respect to the comparative material.

(Example 3)
Steel slabs having various component compositions shown in Table 3 were heated to 1100 ° C. and then hot-rolled to a thickness of 3.0 mm. Next, after rolling to the intermediate thickness of 2.3mm by the first cold rolling, after intermediate annealing at 900 ° C for 60s, cool between 800-200 ° C at an average cooling rate: 40 ° C / s, then the second time After a final thickness of 0.23 mm by cold rolling, primary recrystallization annealing was performed at 820 ° C. for 20 s. The heating rate between 500 and 700 ° C. during the primary recrystallization annealing was set to 15 ° C./s.
Thereafter, nitriding treatment was performed in a cyanate bath at 600 ° C. for 3 minutes. Table 4 shows the nitrogen amount of the steel sheet after the nitriding treatment. Next, after applying an annealing separator containing MgO as the main component to the steel sheet surface, secondary recrystallization annealing is performed at 1200 ° C for 50 hours, followed by application of phosphate-based insulation tension coating. The product was subjected to flattening annealing for the purpose of baking and flattening of the steel strip.
Table 4 shows the results of examining the magnetic properties of the product plate thus obtained. Table 4 also shows the results of examining the aging index AI of the hot-rolled sheet annealed sheet and the texture of the sheet thickness center layer after primary recrystallization annealing.

As shown in Table 4, the AI value of the steel sheet before the final cold rolling, that is, the hot-rolled sheet annealed sheet is set to 70 MPa or less, and the texture of the center thickness layer of the primary recrystallized annealed sheet is expressed as a random strength ratio {554 } <225> strength ≧ 12 and {554} <225> strength / {111} <110> strength ≧ 7, the magnetic flux density B ₈ ≧ 1.95T of the secondary recrystallization annealed plate was achieved.

Example 4
For the samples No. 3 and No. 13 shown in Tables 3 and 4, an experiment was conducted to confirm the effect of the magnetic domain fragmentation treatment shown in Table 5. In the etching, grooves with a width of 80 μm, a depth of 15 μm, and a rolling direction interval of 5 mm were formed in the direction perpendicular to the rolling on one side of the cold-rolled steel sheet. Next, primary recrystallization annealing was performed at 840 ° C. for 20 s. The rate of temperature increase between 500 and 700 ° C. during the primary recrystallization annealing was set to 160 ° C./s. Subsequently, gas nitriding treatment was performed in a gas atmosphere containing ammonia at 750 ° C. for 30 s and at 950 ° C. for 30 s. Table 5 shows the amount of nitrogen in the steel sheet after the nitriding treatment. After that, after applying an annealing separator mainly composed of MgO to the steel plate surface, secondary recrystallization annealing is performed at 1200 ° C for 50 hours, followed by phosphate insulation tension coating. The product was subjected to flattening annealing for the purpose of coating, baking and flattening the steel strip.
The electron beam was continuously irradiated in the direction perpendicular to the rolling under the conditions of acceleration voltage: 80 kV, irradiation interval: 5 mm, and beam current: 3 mA on one side of the steel sheet after the flattening annealing.
The continuous laser was continuously irradiated in the direction perpendicular to the rolling direction on one side of the steel sheet after flattening annealing under the conditions of beam diameter: 0.3 mm, output: 200 W, scanning speed: 100 m / s, and irradiation interval: 5 mm.
The results of examining the magnetic properties of the product plate thus obtained are also shown in Table 5.

  As shown in Table 5, it can be seen that better iron loss characteristics can be obtained by performing the magnetic domain refinement process.

Claims (10)

In mass%, C: 0.0005 to 0.005%, Si: 2.0 to 4.5%, Mn: 0.005 to 0.3%, S and / or Se (total): 0.05% or less, sol. Al: less than 0.010%, N: (14.00 /26.98)×[% sol.Al] or more and 0.008% or less, the remainder of which is a steel slab composed of Fe and inevitable impurities , heated to 1200 ° C or less , hot-rolled, and if necessary After hot-rolled sheet annealing, the final sheet thickness is obtained by cold rolling at least once, or two or more times with intermediate annealing, then primary recrystallization annealing is performed, followed by secondary recrystallization annealing. In producing the electrical steel sheet,
Using the solid solution C amount parameter X calculated from the following equation (1), the average cooling rate R (° C./s) between 800 and 200 ° C. after the heating step immediately before the final cold rolling is expressed as (2) A method for producing a grain-oriented electrical steel sheet, wherein the aging index AI of the steel sheet before final cold rolling is set to 70 MPa or less by making the upper limit average cooling rate _RH or less calculated from the equation.
X = [% Si] /28.09+100 [% C] /12.01 (1)
R _H = 10 / X (2)
However, in the formula (1), [% M] indicates the content of M element (mass%)   By adjusting the average temperature increase rate between 500-700 ° C. of the primary recrystallization annealing to 10 ° C./s or more and 200 ° C./s or less, the random strength of the texture of the thickness center layer of the primary recrystallization annealing plate 2. The directionality according to claim 1, wherein the ratio of {554} <225> strength to 12 is 12 or more, and the ratio of {554} <225> strength to {111} <110> strength is 7 or more. A method for producing electrical steel sheets.   The steel slab is further in mass%, Ni: 0.005-1.5%, Sn: 0.005-0.50%, Sb: 0.005-0.50%, Cu: 0.005-1.5%, Cr: 0.005-0.10%, P: 0.005-0.50 % And Mo: 1 type or 2 types or more selected from 0.005-0.50% are contained, The manufacturing method of the grain-oriented electrical steel sheet of Claim 1 or 2 characterized by the above-mentioned.   The steel slab further contains, by mass%, one or more selected from Ti: 0.001 to 0.1%, Nb: 0.001 to 0.1%, and V: 0.001 to 0.1%. The manufacturing method of the grain-oriented electrical steel sheet according to any one of Items 1 to 3.   The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 4, wherein an additional inhibitor treatment is performed at any stage from the primary recrystallization annealing to the secondary recrystallization annealing.   6. The method for producing a grain-oriented electrical steel sheet according to claim 5, wherein a nitriding treatment is performed as the additional inhibitor treatment.   As the additional inhibitor treatment, one or more selected from sulfides, sulfates, selenides and selenates are added to the annealing separator applied to the steel plate before the secondary recrystallization annealing. The manufacturing method of the grain-oriented electrical steel sheet according to claim 5.   The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 7, wherein a magnetic domain refinement process is performed at any stage after the final cold rolling.   The method for producing a grain-oriented electrical steel sheet according to claim 8, wherein the magnetic domain subdividing treatment is performed by electron beam irradiation to the steel sheet after the secondary recrystallization annealing. The method for producing a grain-oriented electrical steel sheet according to claim 8, wherein the magnetic domain refinement treatment is performed by laser irradiation of the steel sheet after the secondary recrystallization annealing.

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