Grain-oriented electrical steel sheet

Abstract

In the grain-oriented electrical steel sheet, the average value ave [phi] L of the angular deviation [phi] determined at a plurality of measurement points at an interval of 1 mm in the rolling direction L is 3.5 DEG or less, the particle diameter DL determined in the rolling direction L is arranged in the order from large to small, and the particle diameter DL10 at which the particle diameter DL is 10% based on the number from the large particle diameter DL is (100-15 * ave [phi] L) mm or less. And the average value aveDC of the particle diameter DC determined along the direction C perpendicular to the rolling direction is 50 mm or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a grain-oriented magnetic steel sheet.

[0002] This application claims priority based on Japanese Patent Application No. 2023-106860 filed on June 29, 2023, and the contents thereof are hereby incorporated by reference. BACKGROUND

[0003] A grain-oriented magnetic steel sheet contains Si, the crystal orientation of the crystal grains thereof is gathered around a Goss orientation (cubic crystal {110} <001>), and the <001> orientation as an easy magnetization axis is substantially aligned in the rolling direction in a steel sheet manufacturing process. Such a grain-oriented magnetic steel sheet is very excellent as a material for a core of a transformer or the like. As one of important magnetic properties of a grain-oriented magnetic steel sheet, a magnetic flux density can be cited.

[0004] The magnetic flux density of a grain-oriented magnetic steel sheet when a prescribed magnetization force is applied has the tendency that the higher the degree of alignment of the easy magnetization axis of the crystal grains in the rolling direction of the steel sheet, that is, the higher the orientation of the crystal orientation, the larger the magnetic flux density becomes. As an index indicating the magnetic flux density, a magnetic flux density B8 is generally used. The magnetic flux density B8 is the value of the magnetic flux density of a grain-oriented magnetic steel sheet that is magnetized when a magnetization force of 800 A / m is applied in the rolling direction. That is, it can be said that the more the value of the magnetic flux density B8 of a grain-oriented magnetic steel sheet, the more easily the grain-oriented magnetic steel sheet is magnetized with a certain magnetization force, the larger the magnetic flux density becomes, and thus is suitable for a small and efficient transformer.

[0005] Hitherto, a method of controlling the growth of crystal grains in secondary recrystallization to obtain a steel sheet with a high magnetic flux density has been proposed. For example, in Patent Documents 1 and 2, a method is disclosed in which, in a finish annealing process, secondary recrystallization is performed while giving a temperature gradient to a steel sheet in a front end region of secondary recrystallization grains that are gradually eating away primary recrystallization grains.

[0006] In the case where the growth of secondary recrystallization grains is performed using a temperature gradient, secondary recrystallization grains having an orientation close to an ideal Goss orientation are generated in a portion where a secondary recrystallization start state is reached early within the steel sheet, and the secondary recrystallization grains grow preferentially due to the temperature gradient. As a result, the degree of gathering toward the Goss orientation is improved, and the magnetic flux density B8 is improved.

[0007] However, in the case where the growth of secondary recrystallization grains is performed using a temperature gradient, although the grains having an orientation close to an ideal Goss orientation grow preferentially, the secondary recrystallization grains easily grow excessively large. If the secondary recrystallization grains grow excessively large, in the front end region of the growth of the secondary recrystallization grains, the deviation from the ideal Goss orientation becomes large, and it can be possible to hinder the improvement effect of the magnetic flux density.

[0008] For example, the secondary recrystallization is performed in a state where the steel sheet is coiled. That is, the secondary recrystallization grains grow in a state where the steel sheet has a curvature. However, the secondary recrystallization grains grow while maintaining the straightness of the crystal orientation. Therefore, the larger the secondary recrystallization grains grow, the larger the deviation from the ideal Gaussian orientation becomes at the leading end region of the growth of the secondary recrystallization grains due to the curvature of the coil.

[0009] The deviation of the actual crystal orientation from the ideal Gaussian orientation can be expressed by a deviation angle α, a deviation angle β, and a deviation angle γ. The deviation angle α refers to an angle formed by the <001> direction of the crystal projected on the rolling plane and the rolling direction L when viewed from the rolling plane normal direction Z. The deviation angle β refers to an angle formed by the <001> direction of the crystal projected on the L cross section (a cross section having the rolling direction as the normal line) and the rolling direction L when viewed from the rolling right angle direction C (the sheet width direction). The deviation angle γ refers to an angle formed by the <110> direction of the crystal projected on the C cross section (a cross section having the rolling direction as the normal line) and the rolling plane normal direction Z when viewed from the rolling direction L.

[0010] It is known that the deviation angles α and β among the deviation angles α, β, and γ have an effect on the magnetic flux density. The smaller the values of the deviation angles α and β, the higher the magnetic flux density B8 becomes.

[0011] Further, it is known that the deviation angle β among the deviation angles α, β, and γ has an effect on magnetostriction. The smaller the value of the deviation angle β, the higher the magnetostriction characteristic becomes. Note that the magnetostriction refers to a phenomenon in which a magnetic body changes in shape due to the application of a magnetic field. In the case of a grain-oriented electrical steel sheet used in a transformer or the like, since the magnetostriction becomes a cause of vibration and noise, it is required to be small. For example, controlling the deviation angle β is disclosed in Patent Documents 3 to 5.

[0012] Prior Art Documents Patent Documents Patent Document 1: Japanese Patent Application Laid-Open No. 57-002839 Patent Document 2: Japanese Patent Application Laid-Open No. 61-190017 Patent Document 3: Japanese Patent Application Laid-Open No. 2001-294996 Patent Document 4: Japanese Patent Application Laid-Open No. 2005-240102 Patent Document 5: Japanese Patent Application Laid-Open No. 2015-206114 SUMMARY

[0013] PROBLEMS TO BE SOLVED BY THE INVENTION As described above, attempts have been made to increase the magnetic flux density of grain-oriented magnetic steel sheets. For example, attempts have been made to increase the degree of aggregation toward Goss orientation by performing secondary recrystallization while giving a temperature gradient to a steel sheet, thereby increasing the magnetic flux density.

[0014] However, in the case where secondary recrystallization grains are grown using a temperature gradient, the secondary recrystallization grains become excessively large, and it is not possible to avoid a large deviation from the ideal Goss orientation. Therefore, it is possible to hinder the effect of increasing the magnetic flux density. In addition, it is possible that the magnetostriction characteristics will decrease.

[0015] The present application has been made in view of the above-described problems. An object of the present application is to provide a grain-oriented magnetic steel sheet excellent in magnetic flux density and magnetostriction characteristics. Specifically, an object is to provide a grain-oriented magnetic steel sheet excellent in both the magnetic flux density and the magnetostriction characteristics even if a technique of imparting a temperature gradient to a steel sheet at the time of secondary recrystallization is applied.

[0016] Means for solving the problems That is, the gist of the present application is as follows.

[0017] A grain-oriented magnetic steel sheet according to one aspect of the present application is a grain-oriented magnetic steel sheet in which, when an angle of deviation from an ideal Goss orientation defined with a rolling face normal direction Z as an axis of rotation is defined as a, an angle of deviation from the ideal Goss orientation defined with a rolling right angle direction C as an axis of rotation is defined as β, an angle of deviation from the ideal Goss orientation defined with a rolling direction L as an axis of rotation is defined as γ, an angle of deviation of crystal orientation measured at one measurement point on a sheet surface is expressed as (a, β, γ), and an angle deviation of the one measurement point is defined as φ = (a 2 + β 2 ) 1 / 2 , an average value of angle deviations φ calculated from a plurality of measurement points spaced apart by 1 mm along the rolling direction L is defined as aveφ L , the aveφ L satisfies aveφ L ≤ 3.5°, In a grain-oriented magnetic steel sheet according to one aspect of the present application, when angles of deviation of crystal orientation measured at two measurement points adjacent to each other and spaced apart by 1 mm on the sheet surface are expressed as (a1, β1, γ1) and (a2, β2, γ2), a middle point of the two measurement points satisfying [(a2 - a1) 2 + (β2 - β1) 2 + (γ2 - γ1) 2 ] 1 / 2 ≥ 1.0° is defined as a grain boundary GB, and a particle size in the rolling direction L calculated on the basis of the grain boundary GB is defined as D L (mm). LArranged in descending order, and counting the largest particles by their number as the basis, the 10% of the particle size is defined as D in mm. L At 10 o'clock, the D L 10 satisfies D L 10≤100-15×aveφ L , The grain size in the rolling right-angle direction C, calculated based on the grain boundary GB, is defined in mm as D. C The particle size D is determined along the rolling right-angle direction C. C The average value is defined as aveD C At that time, the aveD C Satisfy aveD C ≥50.

[0018] Invention Effects According to the above-described solution of the present invention, a directional electromagnetic steel sheet with excellent magnetic flux density and magnetostrictive properties can be provided. Specifically, a directional electromagnetic steel sheet with excellent magnetic flux density and magnetostrictive properties can be provided even when a technique for imparting a temperature gradient to the steel sheet during secondary recrystallization is applied. Attached Figure Description

[0019] Figure 1 This diagram illustrates an example of using point-current heating as a localized rapid heating method, and is a schematic diagram illustrating an example of the configuration of the localized heating influence zone in a decarburized annealed steel sheet.

[0020] Figure 2 This is a schematic diagram showing the distribution of Gaussian-oriented grains in a decarburized annealed steel sheet. Detailed Implementation

[0021] A preferred embodiment of the present invention will be described in detail below. However, the present invention is not limited to the configuration disclosed in this embodiment, and various modifications can be made without departing from the spirit of the invention. Furthermore, the lower and upper limits of the numerical ranges described below are included within the range. Values ​​expressed as "more than" or "less than" are not included in the numerical range. Additionally, unless otherwise specified, the "%" in chemical composition refers to "mass %".

[0022] In this embodiment, the directional electromagnetic steel sheet (base steel sheet) defines the deviation angle from the ideal Gaussian orientation with the rolling surface normal direction Z as the rotation axis as α, the deviation angle from the ideal Gaussian orientation with the rolling right-angle direction C as the rotation axis as β, and the deviation angle from the ideal Gaussian orientation with the rolling direction L as the rotation axis as γ. The deviation angle of the crystal orientation measured at one measurement point on the sheet surface is expressed as (α, β, γ), and the angular deviation at the above-mentioned one measurement point is defined as φ = (α...).2 +β 2 ) 1 / 2 The average value of the angular deviation φ obtained from multiple measuring points spaced 1 mm apart along the rolling direction L is defined as aveφ. L At that time, the above aveφ L Satisfy aveφ L ≤3.5°.

[0023] Furthermore, in this embodiment, the directional electromagnetic steel plate (base steel plate) has crystal orientation deviation angles measured at two adjacent measurement points spaced 1 mm apart on the plate surface, expressed as (α1, β1, γ1) and (α2, β2, γ2), which satisfy [(α2-α1)]. 2 +(β2-β1) 2 +(γ2-γ1) 2 ] 1 / 2 The midpoint between two measurement points with an angle ≥1.0° is defined as the grain boundary GB. The grain size of the rolling direction L, calculated based on the above grain boundary GB, is defined as D in mm. L The particle size D obtained along the rolling direction L is... L Arranged in descending order, and counting the largest particles by their number as the basis, the 10% of the particle size is defined as D in mm. L At 10:00, the aforementioned D L 10 satisfies D L 10≤100-15×aveφ L .

[0024] Furthermore, in this embodiment, the directional electromagnetic steel sheet (base steel sheet) defines the grain size of the rolling right-angle direction C, determined based on the above-mentioned grain boundary GB, in mm as D. C The particle size D is obtained along the right-angle direction C of the rolling process. C The average value is defined as aveD C At that time, the above aveD C Satisfy aveD C ≥50.

[0025] In the directional electromagnetic steel sheet of this embodiment, even if the technique of imparting a temperature gradient to the steel sheet during secondary recrystallization is applied, both the magnetic flux density and the magnetostrictive properties can be improved when all the above conditions are met simultaneously.

[0026] Note that in the present embodiment, the angle deviation φ is defined by the misalignment angle α and the misalignment angle β. Generally, the angle deviation θ is evaluated by the three components of the misalignment angle α, the misalignment angle β, and the misalignment angle γ. However, in the present embodiment, the misalignment angle γ, which has a small influence on the magnetic flux density and the magnetostriction characteristics, is excluded, and the angle deviation φ is defined by the two components of the misalignment angle α and the misalignment angle β. If the above condition is satisfied using this angle deviation φ, the above effects can be obtained. On the other hand, the crystal grain boundary and the crystal grain size can be determined based on the three components of the misalignment angle α, the misalignment angle β, and the misalignment angle γ.

[0027] aveφ L 3.5° or less means that the angle deviation φ is small on average at each measurement point along the rolling direction L. That is, it means that the angle deviation of the rolling direction L and the easy magnetization axis direction is small. As a result, the magnetic characteristics, particularly the magnetic flux density, are preferably improved. aveφ L 3.2° or less, more preferably 3.0° or less, and more preferably 2.7° or less. On the other hand, aveφ L The smaller the value of aveφ L It is not easy to set aveφ L 0.5° or more, and 1.0° or more.

[0028] D L 10 of (100 - 15 x aveφ L ) mm or less means that the crystal grains do not grow thickly with respect to the rolling direction L. If the crystal grains do not grow thickly with respect to the rolling direction L, the increase in the above-described misalignment angles, particularly the misalignment angle β, can be suppressed. If the increase in the misalignment angle β is suppressed, the decrease in the magnetic flux density can be suppressed, and the increase in the magnetostriction can also be suppressed. When D L 10 satisfies the above condition, the magnetic flux density and the magnetostriction characteristics are preferably improved. D L 10 is more preferably (90 - 15 x aveφ L ) mm or less, and more preferably (80 - 15 x aveφ L ) mm or less. On the other hand, the smaller the value of D L 10, the more preferable it is, and thus the lower limit is not particularly limited. For example, D L 10 can be 5 mm or more, and 10 mm or more.

[0029] aveD Cindicates that the shape of the crystal grains extends in the direction C perpendicular to the rolling direction. The directionally solidified electromagnetic steel sheet of the present embodiment is premised on a technique of imparting a temperature gradient to the steel sheet at the time of secondary recrystallization. Therefore, the secondary recrystallization grains easily grow coarsely. However, in the present embodiment, the growth of the grains coarsely with respect to the rolling direction L is suppressed as described above. On the other hand, in the present embodiment, the growth of the grains coarsely with respect to the direction C perpendicular to the rolling direction is permitted. The directionally solidified electromagnetic steel sheet of the present embodiment is premised on a technique of imparting a temperature gradient to the steel sheet at the time of secondary recrystallization, and therefore the secondary recrystallization grains easily grow coarsely.aveD C becomes 50 mm or more.aveD C It is preferable that it be 80 mm or more, more preferable that it be 100 mm or more, and more preferable that it be 200 mm or more. On the other hand,aveD C The upper limit is not particularly limited. For example, the particle diameter of the grains in the direction C perpendicular to the rolling direction can also be the width of the coil (for example, 1000 mm).aveD C It can be 800 mm or less, and can be 500 mm or less.

[0030] Note that the deviation angle a, the deviation angle β, the deviation angle γ, and the like described above can be measured by setting a measurement line of measurement points including at least 500 points at 1 mm intervals on the rolling surface to measure the crystal orientation. For example, the crystal orientation can be measured by an X-ray diffraction method (Laue method). The Laue method refers to a method of irradiating an X-ray beam to a steel sheet and analyzing a transmitted or reflected diffraction spot. By analyzing the diffraction spot, the crystal orientation of the portion irradiated with the X-ray beam can be identified. If the irradiation position is changed and the analysis of the diffraction spot is performed at a plurality of portions, the crystal orientation distribution at each irradiation position can be measured. The Laue method is a method suitable for measuring the crystal orientation of a metal structure having coarse grains.

[0031] Note that the measurement points of the crystal orientation can be at least 500 points, but it is preferable to appropriately increase the measurement points depending on the size of the secondary recrystallization grains. For example, when the secondary recrystallization grains included in the measurement line become less than 10 in the case where the measurement points for measuring the crystal orientation are set to 500 points, it is preferable to increase the measurement points at 1 mm intervals so as to extend the measurement line described above in a manner that 10 or more secondary recrystallization grains are included in the measurement line. In addition, in the case where it is difficult to set 500 points of measurement points with one measurement line, a plurality of measurement lines can be set and the crystal orientation can be measured with 500 points or more of measurement points in total.

[0032] The crystal orientation is measured at 1 mm intervals on the rolling surface, and on this basis, the deviation angle a, the deviation angle β, the deviation angle γ, and the like described above are determined for each measurement point. Based on the deviation angles at each measurement point determined, the angle deviation φ,aveφL grain boundary GB, particle diameter D L D L 10 particle diameter D C aveD C Note that, regarding D L 10, the particle diameter D L of the crystal grains of 2 mm or more is arranged in descending order and the particle diameter of 10% of the number of the largest ones is obtained. Regarding aveD C , the average particle diameter is obtained based on the particle diameter D C of the crystal grains of 2 mm or more. In addition, when the irradiation area of the X-ray beam in the measurement point of the crystal orientation based on the Laue method straddles two crystal grains and it is not possible to determine which crystal grain the X-ray diffraction result originates from, 0.5 mm is added to the crystal grain diameter of each of the two crystal grains.

[0033] In addition, the grain-oriented magnetic steel sheet of the present embodiment can have only the following chemical composition.

[0034] The grain-oriented magnetic steel sheet of the present embodiment can have, as the chemical composition, Si: 2.0 to 7.0% by mass, and the remainder includes Fe and impurities.

[0035] In addition, the grain-oriented magnetic steel sheet can contain a known optional element instead of a part of Fe for the purpose of improving magnetic properties. The optional element does not necessarily have a lower limit, and the lower limit can be 0%. In addition, the optional element can have an upper limit in a range in which a decrease in magnetic flux density and a decrease in iron loss do not significantly occur. The upper limit of each optional element targeted is described below.

[0036] Specifically, the grain-oriented magnetic steel sheet (base steel sheet) of the present embodiment can have, as the chemical composition, by mass%: Si: 2.0 to 7.0%, C: 0 to 0.0050%, Mn: 0 to 1.0%, S and Se: 0 to 0.0150% in total, Al: 0 to 0.0650%, N: 0 to 0.0050%, Nb, V, Mo, Ta, and W: 0 to 0.050% in total, Cu: 0 to 0.40%, Bi: 0 to 0.010%, B: 0 to 0.080%, P: 0 to 0.50%, Ti: 0 to 0.0150%, Sn: 0 to 0.10%, Sb: 0 to 0.10%, Cr: 0 to 0.30%, Ni: 0 to 1.0%, The remainder includes Fe and impurities.

[0037] Si: 2.0 to 7.0% Si (silicon) is an essential element for the base material steel sheet. If the Si content is less than 2.0%, the eddy current loss cannot be sufficiently reduced, and thus good magnetic characteristics cannot be obtained. Therefore, the Si content of the base material steel sheet is set to 2.0% or more. The Si content is preferably 2.50% or more, and more preferably 3.0% or more. On the other hand, if the Si content exceeds 7.0%, the steel sheet is embrittled, and the through-plate property significantly deteriorates at the time of manufacture, and thus the Si content of the base material steel sheet is set to 7.0% or less. The Si content is preferably 4.50% or less, and more preferably 4.0% or less.

[0038] C: 0 to 0.0050% C (carbon) is a selection element for the base material steel sheet. C is contained in a steel billet (slab), but if C excessively remains in the base material steel sheet after annealing of a finished product, it can be difficult to obtain good iron loss characteristics. Therefore, the C content of the base material steel sheet is 0.0050% or less. The C content is preferably 0.0040% or less, and more preferably 0.0030% or less. On the other hand, the lower limit value of the C content of the base material steel sheet is not particularly limited, and can be 0%. However, it is industrially difficult to set the C content to 0%, and thus the C content can be set to more than 0%, and can be set to 0.00010% or more.

[0039] Mn: 0 to 1.0% Mn (manganese) is a selection element for the base material steel sheet. Mn is contained in a steel billet (slab), but if it is excessively contained, the steel phase changes at the time of secondary recrystallization annealing, and the secondary recrystallization does not sufficiently proceed, and thus it can be difficult to obtain good magnetic characteristics. Therefore, the Mn content of the base material steel sheet is 1.0% or less. The Mn content is preferably 0.50% or less, and more preferably 0.20% or less. On the other hand, the lower limit value of the Mn content of the base material steel sheet is not particularly limited, and can be 0%. However, Mn has an effect as an inhibitor at the time of secondary recrystallization due to the formation of MnS and MnSe, and thus the Mn content can be set to more than 0%, and can be set to 0.00010% or more.

[0040] Total of S and Se: 0 to 0.0150% S (sulfur) and Se (selenium) are optional elements for the base steel sheet. S and Se are contained in a steel billet (slab), but if S and Se are excessively left in the base steel sheet after annealing of the finished product, it is possible to cause adverse effects on magnetic properties. Therefore, the total content of S and Se in the base steel sheet is 0.0150% or less. The total content of S and Se is preferably 0.010% or less, and more preferably 0.0050% or less. On the other hand, the lower limit value of the total content of S and Se in the base steel sheet is not particularly limited, and is 0%. However, S and Se have an effect as an inhibitor at the time of secondary recrystallization because they form MnS and MnSe, and therefore the total content of S and Se can be set to more than 0%, and can be set to 0.00010% or more.

[0041] Al: 0 to 0.0650% Al (aluminum) is an optional element for the base steel sheet. Al is contained in a steel billet (slab), but if Al is excessively left in the base steel sheet after annealing of the finished product, it is possible to cause adverse effects on magnetic properties. Therefore, the Al content in the base steel sheet is 0.0650% or less. The Al content is preferably 0.040% or less, and more preferably 0.035% or less. On the other hand, the lower limit value of the Al content in the base steel sheet is not particularly limited, and is 0%. However, Al has an effect as an inhibitor at the time of secondary recrystallization because it forms AlN, and therefore the Al content can be set to more than 0%, and can be set to 0.00010% or more. Note that the above Al content is acid-soluble Al (sol. Al).

[0042] N: 0 to 0.0050% N (nitrogen) is an optional element for the base steel sheet. N is contained in a steel billet (slab), but if N is excessively left in the base steel sheet after annealing of the finished product, it is possible to cause adverse effects on magnetic properties. Therefore, the N content in the base steel sheet is 0.0050% or less. The N content is preferably 0.0040% or less, and more preferably 0.0030% or less. On the other hand, the lower limit value of the N content in the base steel sheet is not particularly limited, and is 0%. However, N has an effect as an inhibitor at the time of secondary recrystallization because it forms AlN, and therefore the N content can be set to more than 0%, and can be set to 0.00010% or more.

[0043] Nb, V, Mo, Ta, and W: 0 to 0.050% Nb, V, Mo, Ta, and W in the base steel sheet, it is possible to cause adverse effects on magnetic properties. Therefore, the total content of Nb, V, Mo, Ta, and W in the base steel sheet is 0.050% or less. The Nb group elements are preferably 0.030% or less, preferably 0.020% or less, and more preferably 0.010% or less. On the other hand, the total content of Nb, V, Mo, Ta, and W in the base steel sheet is not particularly limited, and can be 0%. However, Nb, V, Mo, Ta, or W has an effect as an inhibitor at the time of secondary recrystallization by forming carbides, nitrides, and carbonitrides, and therefore the total content of Nb, V, Mo, Ta, and W can be set to more than 0%, and can be set to 0.003% or more.

[0044] Cu: 0 to 0.40% Cu is a selection element for the base steel sheet. If the Cu content exceeds 0.40%, it is possible that the steel sheet becomes brittle in hot rolling. Therefore, the Cu content in the base steel sheet is 0.40% or less. The Cu content is preferably 0.30% or less, and more preferably 0.10% or less. On the other hand, the lower limit value of the Cu content is not particularly limited, and can be 0%. However, Cu has an effect of improving the degree of aggregation of the Goss orientation and improving magnetic properties, and therefore the Cu content can be set to more than 0%, and can be set to 0.010% or more.

[0045] Bi: 0 to 0.010% Bi is a selection element for the base steel sheet. If the Bi content exceeds 0.010%, it is possible that the adhesion of the coating film is reduced. In addition, if Bi is excessively left over due to insufficient purification at the time of finish annealing, it is possible to cause adverse effects on magnetic properties. Therefore, the Bi content in the base steel sheet is 0.010% or less. The Bi content is preferably 0.0050% or less, more preferably 0.0020% or less, and more preferably 0.0010% or less. On the other hand, the lower limit value of the Bi content is not particularly limited, and can be 0%. However, Bi has an effect of increasing the magnetic flux density, and therefore the Bi content can be set to more than 0%, and can be set to 0.00050% or more.

[0046] B: 0 to 0.080% B (boron) is a selective element for the base material steel sheet. If the B content exceeds 0.080%, it is possible that the unevenness (standard deviation) of the magnetic flux density becomes large. Therefore, the B content can be 0.080% or less. The Bi content is preferably 0.070% or less, and more preferably 0.060% or less. On the other hand, the lower limit value of the B content is not particularly limited, and can be 0%. However, B has an effect as an inhibitor at the time of secondary recrystallization because it forms nitride, and therefore the B content can be set to more than 0%, and can be set to 0.00050% or more.

[0047] P: 0 to 0.50% P (phosphorus) is a selective element for the base material steel sheet. If the P content exceeds 0.50%, it is possible that the workability of the steel sheet significantly decreases. Therefore, the P content of the base material steel sheet can be 0.50% or less. The P content is preferably 0.30% or less, and more preferably 0.10% or less. On the other hand, the lower limit value of the P content is not particularly limited, and can be 0%. However, P has an effect of improving texture and improving the magnetic properties of the steel sheet, and therefore the P content can be set to more than 0%, and can be set to 0.0020% or more.

[0048] Ti: 0 to 0.0150% Ti (titanium) is a selective element for the base material steel sheet. If the Ti content exceeds 0.0150%, it is possible that the magnetic properties decrease. Therefore, the Ti content of the base material steel sheet can be 0.0150% or less. The Ti content is preferably 0.0130% or less, and more preferably 0.010% or less. On the other hand, the lower limit value of the Ti content is not particularly limited, and can be 0%. However, Ti has an effect as an inhibitor at the time of secondary recrystallization because it forms carbide, nitride, and carbonitride, and therefore the Ti content can be set to more than 0%, and can be set to 0.0020% or more.

[0049] Sn: 0 to 0.10% Sn (tin) is a selective element for the base material steel sheet. If the Sn content exceeds 0.10%, the secondary recrystallization becomes unstable, and it is possible to adversely affect the magnetic properties. Therefore, the Sn content of the base material steel sheet can be 0.10% or less. The Sn content is preferably 0.090% or less, and more preferably 0.080% or less. On the other hand, the lower limit value of the Sn content is not particularly limited, and can be 0%. However, Sn has an effect of improving the degree of aggregation of the Goss orientation and improving the magnetic properties, and therefore the Sn content can be set to more than 0%, and can be set to 0.0050% or more.

[0050] Sb: 0 to 0.10% Sb (antimony) is a selective element for the base steel sheet. If the Sb content exceeds 0.10%, there is a possibility of causing adverse effects on the magnetic properties. Therefore, the Sb content of the base steel sheet can be 0.10% or less. The Sb content is preferably 0.090% or less, and more preferably 0.080% or less. On the other hand, the lower limit value of the Sb content is not particularly limited, and can be 0%. However, Sb has an effect of stabilizing the secondary recrystallization by functioning as an inhibitor, and therefore the Sb content can be set to more than 0%, and can be set to 0.010% or more.

[0051] Cr: 0 to 0.30% Cr (chromium) is a selective element for the base steel sheet. If the Cr content exceeds 0.30%, there is a possibility of forming Cr oxides, causing adverse effects on the magnetic properties. Therefore, the Cr content of the base steel sheet can be 0.30% or less. The Cr content is preferably 0.20% or less, and more preferably 0.10% or less. On the other hand, the lower limit value of the Cr content is not particularly limited, and can be 0%. However, Cr has an effect of improving the degree of aggregation of the Goss orientation and improving the magnetic properties, and therefore the Cr content can be set to more than 0%, and can be set to 0.010% or more.

[0052] Ni: 0 to 1.0% Ni (nickel) is a selective element for the base steel sheet. If the Ni content exceeds 1.0%, there is a possibility of the secondary recrystallization becoming unstable. Therefore, the Ni content of the base steel sheet can be 1.0% or less. The Ni content is preferably 0.20% or less, and more preferably 0.10% or less. On the other hand, the lower limit value of the Ni content is not particularly limited, and can be 0%. However, Ni has an effect of improving the electrical resistance and reducing the iron loss, and therefore the Ni content can be set to more than 0%, and can be set to 0.010% or more.

[0053] The base steel sheet of the oriented electromagnetic steel sheet of the present embodiment can contain impurities. Note that the "impurities" refer to substances mixed from ores, waste materials, or manufacturing environments, etc. as raw materials when steel is manufactured industrially.

[0054] The chemical composition of the above-described base steel sheet can be measured by a general analysis method. For example, it can be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Note that the acid-soluble Al can be measured using a filtrate obtained by heating and decomposing a sample with an acid and by ICP-AES. In addition, the C and S can be measured using a combustion-infrared absorption method, the N can be measured using an inert gas fusion-thermal conductivity method, and the O can be measured using an inert gas fusion-non-dispersive infrared absorption method.

[0055] Note that the above-described chemical composition is that of the base steel sheet. In the case where the grain-oriented magnetic steel sheet to be measured has an insulating coating film or the like on the surface, the coating film or the like is removed by the following method before measuring the chemical composition.

[0056] For example, as a method for removing the insulating coating film, it is only necessary to immerse the grain-oriented magnetic steel sheet having the coating film in a high-temperature alkali solution. Specifically, by immersing in a sodium hydroxide aqueous solution of NaOH: 30 to 50 mass% + H2O: 50 to 70 mass% at 80 to 90°C for 5 to 10 minutes, followed by water washing and drying, the insulating coating film can be removed from the grain-oriented magnetic steel sheet. Note that the immersion time in the above-described sodium hydroxide aqueous solution can be changed depending on the thickness of the insulating coating film.

[0057] In addition, as a method for removing the forsterite coating film (glass coating film), it is only necessary to immerse the grain-oriented magnetic steel sheet from which the insulating coating film has been removed by the above-described method in a high-temperature hydrochloric acid. Specifically, the concentration of hydrochloric acid that is preferable for dissolving the forsterite coating film to be dissolved is investigated in advance, and by immersing in the hydrochloric acid (for example, 30 to 40 mass% hydrochloric acid) of the concentration at 80 to 90°C for 1 to 5 minutes, followed by water washing and drying, the forsterite coating film can be removed. Generally, in the same manner as using an alkali solution in the removal of the insulating coating film and using hydrochloric acid in the removal of the forsterite coating film, the respective coating films are removed using separate treatment solutions.

[0058] Hereinafter, the process until the grain-oriented magnetic steel sheet of the present embodiment is obtained is described.

[0059] The frequency of the practical Goss-oriented grains having a small angle deviation θ and a small angle deviation φ from the {110} <001> orientation which is an ideal Goss orientation increases as the heating rate of the primary annealing (decarburization annealing) is accelerated. On the other hand, the grains (referred to as the coincidence-oriented grains) of the {778} <447> (≈{111} <112>) orientation, the {411} <148> orientation, and the like which have a Σ9 coincidence site lattice orientation relationship with the Goss orientation are easily eaten away by the Goss-oriented grains. If the heating rate of the primary annealing is accelerated, the frequency of the coincidence-oriented grains decreases. Therefore, in the primary annealing, it is difficult to increase the ratio of the practical Goss-oriented grains while also increasing the ratio of the coincidence-oriented grains.

[0060] In the present embodiment, it was first found that by forming a local heating region by locally and rapidly heating a cold-rolled steel sheet, controlling the annealing conditions of the primary annealing (decarburization annealing), and controlling the annealing conditions of the secondary annealing (product annealing), a grain-oriented electromagnetic steel sheet having excellent quality can be obtained.

[0061] The local heating region formed before the primary annealing is locally arranged with respect to the surface of the steel sheet. The crystal structure of the local heating region is made of one or both of recrystallized structure and recovered structure at the time when the local and rapid heating ends. The crystal structure of the non-rapidly heated portion other than the local heating region in the surface of the steel sheet is made of cold-worked structure in the cold-rolled state.

[0062] The above-described local and rapid heating is preferably at a rate of 500°C / sec or more, more preferably 2000°C / sec or more, and further more preferably 10000°C / sec or more. In this way, it was found that if the primary annealing is performed on the steel sheet after forming the local heating region on the surface of the steel sheet before the primary annealing, a large number of grains having a practical Goss orientation can be formed in the region affected by the local and rapid heating (local heating-affected region). In addition, it was also found that the ratio of the Goss-oriented grains having a smaller angle deviation θ and a smaller angle deviation φ from the ideal Goss orientation increases, and the grain size of the Goss-oriented grains after the primary annealing increases.

[0063] The frequency of the coarse Goss-oriented grains contained in the local heating-affected region increases compared to the frequency obtained by the rapid heating of the entire steel sheet. It is believed that this characteristic is due to the fact that the peripheral portion of the local heating region is a worked structure in which a large amount of strain remains. Specifically, it is believed that in the case where the local and rapid heating is performed, the practical Goss-oriented grains generated in the local heating region preferentially eat away the unrecrystallized region in the peripheral portion in which a large amount of strain remains to become large in diameter at the time of the primary annealing, but in the case where the entire steel sheet is heated, the generation and growth of recrystallized grains occur uniformly within the steel sheet, and thus the above-described large diameter does not occur.

[0064] On the basis of the fact that the local heating affected region having the above-described characteristics is spread over the surface of the steel sheet by the primary annealing, further secondary annealing is performed. In the secondary annealing, the secondary recrystallization is performed while giving a temperature gradient to the steel sheet. At this time, the Goss-oriented grains formed in the local heating affected region are preferentially grown at the time of the secondary annealing. In the local heating affected region, a large number of Goss-oriented grains, among which there are Goss-oriented grains having a large crystal grain diameter after the primary annealing and particularly small angle deviation θ and angle deviation φ, which are close to ideal Goss orientation, are formed, and such Goss-oriented grains are particularly preferentially grown in the secondary recrystallization.

[0065] Note that the Goss-oriented grains that become the nuclei of the secondary recrystallization are supplied to the local heating affected region, and thus it is not necessary to form Goss-oriented grains in the matrix portion other than the local heating affected region, that is, the local heating non-affected region, by the primary annealing. Therefore, as the heat treatment conditions of the primary annealing, it is also possible to adopt a primary annealing condition in which slow heating conditions in which the heating rate is set to be low are set, and in the local heating non-affected region, a large number of heavy point lattice-oriented grains having {111} <112> orientation and {411} <148> orientation, which are easily eaten away, are formed. For example, by setting the heating rate of the primary annealing to 300°C / sec or less, it is possible to form a large number of Goss-oriented grains that are close to ideal Goss orientation and have a large crystal grain diameter in the local heating affected region, and on the other hand, it is possible to hardly form Goss-oriented grains in the local heating non-affected region, and instead, it is possible to form a large number of heavy point lattice-oriented grains.

[0066] As described above, in the local heating affected region of the steel sheet (decarburized annealed steel sheet) after the local rapid heating and the end of the primary annealing, a large number of Goss-oriented grains that are close to ideal Goss orientation and have a large grain diameter are present. On the other hand, in the matrix portion (local heating non-affected region), the Goss-oriented grains that are large in diameter are hardly present, and it is also possible to make a large number of heavy point lattice-oriented grains that are easily eaten away present.

[0067] If such a steel sheet (decarburized annealed steel sheet) is subjected to secondary annealing, the Goss-oriented grains that are close to ideal Goss orientation and have a large grain diameter, which are present in the local heating affected region, start to be preferentially grown, and grow toward the local heating non-affected region.

[0068] Further, in the present embodiment, in the secondary annealing, in the front region of the secondary recrystallized grains that are gradually eating away the primary recrystallized grains, the secondary recrystallization is performed while giving a temperature gradient to the steel sheet. In the case where the secondary recrystallized grains are grown using the temperature gradient, the secondary recrystallized grains having an orientation close to the ideal Gaussian orientation, which are grown preferentially due to the temperature gradient, are generated in the portion where the secondary recrystallization starts early within the steel sheet. As a result, the degree of the aggregation to the Gaussian orientation is preferably increased. The direction in which the above-described temperature gradient is given is set to the rolling right angle direction C.

[0069] In the past, in the case where the secondary recrystallized grains are grown using the temperature gradient, the secondary recrystallized grains excessively grow large, and the deterioration of the deviation angle β due to the coil set cannot be avoided. Specifically, for example, in the case where the temperature gradient in the secondary annealing is applied in the rolling perpendicular direction C, the secondary recrystallized Gaussian orientation grains easily grow toward the low temperature side of the steel sheet (the rolling perpendicular direction C), and at this time, the secondary recrystallized grains also grow in the rolling direction L. Therefore, the crystal grain size D L in the rolling direction also becomes large. That is, in the past technology, the more the magnetic flux density is intended to be increased, the larger the crystal grain size D L in the rolling direction becomes, and as a result, the increase of the deviation angle β due to the coil set cannot be avoided. However, in the present embodiment, by the above-described local rapid heating, the frequency of the existence of the secondary recrystallized grains having an orientation close to the ideal Gaussian orientation is increased, and therefore, the increase of the crystal grain size D L in the rolling direction is suppressed, and the deterioration of the deviation angle β due to the coil set is suppressed. In this way, in the present embodiment, by suppressing the deterioration of the deviation angle β, a steel sheet having more excellent magnetic flux density and magnetostrictive characteristics than in the past can be obtained. Further, in the present embodiment, the secondary recrystallized grains having an orientation close to the ideal Gaussian orientation are preferentially generated, and therefore, the deterioration of the deviation angle α is also suppressed. Thus, a steel sheet having more excellent magnetic flux density than in the past can be obtained.

[0070] Hereinafter, the research contents by the inventors of the present application will be specifically described.

[0071] As one example of the above-described local rapid heating, a case where point passage heating based on resistance heating is used will be described. With regard to the point passage heating, a point electrode is press-contacted against both surfaces of a steel sheet, and the electrode holding portion of the steel sheet is subjected to point passage heating by causing a current to flow between the point electrodes. A steel having the composition shown in Table 1 was used, and a cold-rolled steel sheet having a thickness of 0.22 mm was produced by hot rolling and cold rolling. The steel sheet was subjected to point passage heating. The point passage heating was performed using a copper electrode having a diameter of 3 mm, under conditions where the passage current was 5.0 kA or less, the passage time was 20 to 80 milliseconds, the electrode pressing force was 50 to 150 kgf, and the electrode holding time after passage was 0.2 seconds, in a range where the steel sheet surface was not melted. With regard to the surface of the cold-rolled steel sheet, point passage heating was performed at a pitch of 20 mm in the rolling direction at a position 10 mm from the end portion in the direction perpendicular to the rolling direction, to form a local heating region. The cold-rolled steel sheet was subjected to decarburization annealing (primary annealing). In the decarburization annealing, the cold-rolled steel sheet was heated at a rate of 20°C / sec, and held at 830°C for 90 seconds.

[0072] Figure 1 One example of the arrangement of the local heating affected region in the decarburization annealed steel sheet produced under the above-described conditions is shown in FIG. 1. Figure 1 A decarburization annealed steel sheet 1, a local heating affected region 2, a rolling direction 21, and a width direction (direction perpendicular to the rolling direction) 22 are schematically shown in FIG. 1.

[0073] [Table 1] With regard to the surface of the decarburization annealed steel sheet (steel sheet after local rapid heating and primary annealing), in order to prepare an observation surface for EBSD (Electron Back Scattering Diffraction pattern) observation, a smooth surface was produced by mechanical polishing, electrolytic polishing was performed in order to remove the processing strain of the surface, and the IQ (Image Quality) value and crystal orientation were measured by EBSD at a step of 0.5 μm for a region including the local heating region. Figure 2 A schematic view showing the distribution of the Goss-oriented grains in the decarburization annealed steel sheet produced under the above-described conditions is shown in FIG. 2.

[0074] The passage electrode for the point passage heating is in a circular shape, and the diameter thereof is preferably 0.5 mmφ to 10 mmφ, and more preferably 1 mmφ to 5 mmφ, in terms of the equivalent circle diameter. Note that a circular passage electrode was used in the above-described example, but as long as the heating rate of the cold-rolled steel sheet is locally increased, Goss-oriented grains are formed in the region and the grains grow, and the electrode shape can be other shapes, such as an elliptical shape or a linear shape.

[0075] exist Figure 2 In the middle, based on the angle deviation φ=(α 2 +β 2 ) 1 / 2 The definition uses "○" to represent grains with an angular deviation φ of less than 10° from the ideal Gaussian orientation (Gaussian orientation grain 14). Furthermore, among the grains with an angular deviation φ of less than 10°, "◎" is used to represent grains with large crystal sizes (coarse Gaussian orientation grain 15). It should be noted that coarse Gaussian orientation grain 15 refers to Gaussian orientation grains with a grain size more than three times that of the average crystal grain size.

[0076] like Figure 2 As shown, the decarburized annealed steel sheet 1 manufactured under the above conditions contains Gaussian-oriented grains 14 and coarse Gaussian-oriented grains 15. In particular, the region containing the coarse Gaussian-oriented grains 15 corresponds to the locally heated region 2. It should be noted that in... Figure 2 The diagram schematically illustrates the boundary 4 of the locally heated region and the boundary 5 of the locally heated affected region, but it is not easy to identify these boundaries through microstructural observation. However, the region containing coarse Gaussian-oriented grains 15 can be considered as the locally heated affected region 2.

[0077] The aforementioned decarburized annealed steel sheet is further nitrided, coated with an annealing separating agent with MgO as the main component, and then subjected to secondary annealing. The secondary annealing conditions are: hydrogen-nitrogen atmosphere, heating rate: 15℃ / hr (℃ / hour), holding time: 1200℃-20hr (hours). Furthermore, during the secondary annealing heating, a temperature gradient of 5℃ / cm is applied along the rolling perpendicular direction at the boundary between the primary and secondary recrystallization regions in the steel sheet.

[0078] The obtained steel sheet was macroscopically etched to expose the grain boundaries. Observations were made on the areas corresponding to the locally heated regions in the macroscopically etched steel sheet. The results showed that multiple secondary recrystallized grains grew from these areas, and that the secondary recrystallized grains expanded from the center of these areas. Furthermore, in the areas corresponding to the locally heated regions, some areas showed traces of the localized heating region, while others did not. Depending on the localized heating conditions, although there were slight changes in the macroscopic structure of the secondary recrystallization, the aggregation degree towards the Gaussian orientation was improved compared to the case without localized heating.

[0079] Furthermore, the crystal orientation of the obtained steel sheet was determined using the Laue method described above. The aveφ of the obtained steel sheet... L For angles below 3.5°, D L 10 is (100-15×aveφ)L ) mm or less, and aveD C is 50 mm or more. As a result, the obtained steel sheet is excellent in both the magnetic flux density and the magnetostriction, although a temperature gradient is imparted to the steel sheet at the time of secondary recrystallization.

[0080] As described above, with respect to the obtained grain-oriented electromagnetic steel sheet, it is confirmed that the crystal orientation of the secondary recrystallized grains is extremely close to the ideal Goss orientation, and it is confirmed that the average angular deviation φ at each measurement point along the rolling direction L is small, the grains do not coarsely grow with respect to the rolling direction L, and the shape of the grains has a flat tendency of extending along the transverse direction C and being flattened in the rolling direction L.

[0081] If the above-described research results are considered, it is considered that the formation of coarse Goss orientation grains having a size advantage and close to the ideal Goss orientation in the decarburization annealed steel sheet is a reason why the secondary recrystallization orientation becomes good. Further, the preferential arrangement of the local heating regions before the primary annealing, the preferential control of the annealing conditions at the time of the primary annealing, and the preferential control of the annealing conditions at the time of the secondary annealing are considered to be reasons why both the magnetic flux density and the magnetostriction are improved.

[0082] For example, in the case where the above-described decarburization annealed steel sheet is used, at the time of secondary recrystallization, coarse Goss orientation grains (Goss orientation grains having a large crystal grain size) close to the ideal Goss orientation among a large number of Goss orientation grains in the local heating affected region preferentially grow. Therefore, even if the secondary recrystallized grains are not made to grow large, a steel sheet in which the secondary recrystallized grains close to the ideal Goss orientation account for a large proportion of the steel sheet can be produced. For example, in the case where the local heating affected regions are dispersed on the surface of the steel sheet, by appropriately arranging the local heating affected regions at the surface of the steel sheet, the size, shape, and arrangement of the grains after the secondary annealing can be controlled. For example, if the growth of the grains is stopped by collision between a Goss orientation grain growing from one local heating affected region and other Goss orientation grains growing from adjacent local heating affected regions, a steel sheet in which the grain size (particularly, the crystal grain size D L ) in the rolling direction of the Goss orientation grains at the end of the secondary annealing is small can be produced. In particular, as described above, at the initial stage of the secondary annealing, the Goss orientation grains preferentially growing from the local heating affected regions have a crystal orientation close to the ideal Goss orientation, and thus a good magnetic flux density can be obtained even if the secondary recrystallized grain size is small. Further, since the grains are inhibited from coarsely growing with respect to the rolling direction L, deterioration of the deviation angle β due to coiling bending deformation can be inhibited, and a good magnetostriction characteristic can be obtained.

[0083] That is, the above-described grain-oriented electromagnetic steel sheet can be produced while the secondary recrystallized grain size (particularly, the crystal grain size D L) is increased, and the degree of aggregation toward the easy axis is increased, so strain introduction, magnetic domain width refinement based on groove formation, or the like can not be needed or can be reduced. Specifically, the magnetic domain refinement effect can be preferably obtained by the grain boundaries that are increased along with the refinement of the secondary recrystallized grain diameter, so the magnetic domains can be refined even without using the conventional magnetic domain control technique. Therefore, since strain can not be introduced into the steel sheet or can be reduced like the conventional magnetic domain control technique, an increase in magnetostriction can be prevented. In addition, since grooves do not need to be formed in the steel sheet or the groove depth can be reduced like the conventional magnetic domain control technique, a decrease in magnetic flux density B8 can be prevented. In addition, the above-described grain-oriented electromagnetic steel sheet can be used for applications that require strain relief annealing at 800°C or higher.

[0084] Note that the grain-oriented electromagnetic steel sheet of the present embodiment preferably has the magnetic domain refinement effect due to the grain boundaries that are increased along with the refinement of the secondary recrystallized grain diameter (particularly, the crystal grain diameter D L

[0085] Next, a preferred manufacturing method of the grain-oriented electromagnetic steel sheet of the present embodiment will be described.

[0086] Note that the method of manufacturing the grain-oriented electromagnetic steel sheet of the present embodiment is not limited to the following method. The following manufacturing method is one example for manufacturing the grain-oriented electromagnetic steel sheet of the present embodiment.

[0087] In addition, the procedures and the quantitative conditions in each procedure shown below are one example adopted in order to show the implementability of the present embodiment, and the present embodiment is not limited to these procedures and quantitative values. The manufacturing method of the grain-oriented electromagnetic steel sheet of the present embodiment can adopt various conditions as long as the gist of the present embodiment is not deviated from and the object of the present embodiment is achieved.

[0088] The manufacturing method of the grain-oriented electromagnetic steel sheet of the present embodiment can apply the conventional known manufacturing method of the grain-oriented electromagnetic steel sheet as a basic procedure. For example, as the conventional manufacturing method of the grain-oriented electromagnetic steel sheet, a manufacturing method of forming an inhibitor such as MnS, AlN, or the like by high-temperature slab heating, a manufacturing method of forming an AlN inhibitor by low-temperature slab heating and nitriding treatment, or the like can be exemplified. The manufacturing method of the grain-oriented electromagnetic steel sheet of the present embodiment is not limited to a specific manufacturing method. Hereinafter, a method of applying nitriding treatment as a low-temperature slab heating process will be described.

[0089] (Casting Step) ​A slab is prepared in a casting step. An example of a method of manufacturing the slab is described below. A molten steel is manufactured. The molten steel is used to manufacture the slab. The slab can also be manufactured by a continuous casting method. A steel ingot can also be manufactured using the molten steel, and the steel ingot can be manufactured into the slab by blooming. The thickness of the slab is not particularly limited. The thickness of the slab is, for example, 150 to 350 mm. The thickness of the slab is preferably 220 to 280 mm. As the slab, a so-called thin slab having a thickness of 10 to 70 mm can also be used. In the case of using the thin slab, in the hot rolling step, the rough rolling before the finish rolling can be omitted.

[0090] For example, the slab described above contains, as a chemical composition, only the following elements.

[0091] C: 0.085% or less, Carbon (C) is an element effective for controlling the primary recrystallized structure in the manufacturing step, but if the content in the final product is excessive, it adversely affects the magnetic properties. Therefore, the C content is 0.085% or less. The preferable upper limit of the C content is 0.075%. C is purified to 0.005% or less in the decarburization annealing step and the finished product annealing step. In the case of containing C, the lower limit of the C content can also exceed 0% and can be 0.001% if the productivity in industrial production is taken into consideration.

[0092] Si: 2.0 to 7.0% Silicon (Si) increases the electrical resistance of the grain-oriented magnetic steel sheet and reduces the iron loss. If the Si content is less than 2.0%, the γ phase transformation occurs at the finished product annealing, and the crystal orientation of the grain-oriented magnetic steel sheet is impaired. On the other hand, if the Si content exceeds 7.0%, the cold workability is reduced, and cracking is likely to occur at the cold rolling. The preferable lower limit of the Si content is 2.5%, and further preferably 3.0%. The preferable upper limit of the Si content is 4.5%, and further preferably 4.0%.

[0093] Mn: 0.05 to 1.00% Manganese (Mn) generates MnS or MnSe in combination with S or Se and functions as an inhibitor. In the case of containing Mn, the secondary recrystallization is stabilized in the range of 0.05 to 1.00% of the Mn content. Note that a part of the function of the inhibitor can be assumed by the nitride of the Nb group element. In this case, the strength control of the MnS or MnSe as a general inhibitor is weak. Therefore, the preferable upper limit of the Mn content is 0.50%, and further preferably 0.20%.

[0094] At least one of S and Se: 0.003 to 0.035% in total Sulfur (S) and selenium (Se) combine with Mn to form MnS or MnSe, which functions as an inhibitor. In the case of containing at least one of S and Se, if the content of S and Se in total is 0.003 to 0.035%, secondary recrystallization is stabilized. Note that a portion of the function of the inhibitor can be assumed by the nitride of the Nb group element. In this case, the strength control of MnS or MnSe as a general inhibitor is weak. Therefore, the preferable upper limit of the total of the contents of S and Se is 0.025%, and further preferably 0.010%. If S and Se remain after the finish annealing, a compound is formed, which deteriorates the iron loss. Therefore, it is preferable to reduce S and Se as much as possible by purification in the finish annealing.

[0095] Here, the total content of S and Se means the total content of at least one of S and Se.

[0096] Al: 0.010 to 0.065% Aluminum (Al) combines with N to precipitate as (Al, Si)N, which functions as an inhibitor. In the case of containing Al, if the content of Al is in the range of 0.010 to 0.065%, AlN as an inhibitor formed by nitriding described later expands the secondary recrystallization temperature region, and particularly stabilizes the secondary recrystallization in the high temperature region. Therefore, the content of Al is 0.010 to 0.065%. The preferable lower limit of the content of Al is 0.020%, and further preferably 0.025%. From the viewpoint of the stability of the secondary recrystallization, the preferable upper limit of the content of Al is 0.040%, and further preferably 0.035%.

[0097] N: 0.012% or less Nitrogen (N) functions as an inhibitor in combination with Al. N is not regulated in the lower limit because it can be contained by nitriding in the middle of the manufacturing process. For example, the lower limit of the content of N can exceed 0%, and can be 0.001%. On the other hand, in the case of containing N, if the content of N exceeds 0.012%, it becomes easy to generate a blister as one kind of defects in the steel sheet. The preferable upper limit of the content of N is 0.010%, and further preferably 0.009%. N is purified in the finish annealing process, and becomes 0.005% or less after the finish annealing process.

[0098] The remaining portion of the above-described chemical composition contains Fe and impurities. Note that "impurities" means elements mixed from ore, waste, or manufacturing environment, etc. as raw materials when steel is manufactured industrially. The upper limit of the total content of impurities is, for example, 5% or less.

[0099] The chemical composition described above can contain, instead of part of Fe, a known optional element in order to solve the problems in the production, to enhance the function of the inhibitor due to the formation of the compound, and to affect the magnetic properties.

[0100] Nb group element: 0.050% or less The total content of the Nb group elements (one or more of Nb, V, Mo, Ta, and W) can be 0.050% or less. In the case where the Nb group elements are used as part of the inhibitor, if the total content of the Nb group elements is 0.030% or less, the secondary recrystallization is started at an appropriate timing, and thus is preferable. In addition, the orientation of the secondary recrystallized grains becomes very preferable, and finally the structure preferred for the magnetic properties can be controlled. In particular, the effects of Nb and Ta are strongly preferable. The total content of the Nb group elements does not necessarily have a lower limit, and the lower limit can be 0%. The lower limit is preferably 0.003%.

[0101] The total content of the Nb group elements is more preferably 0.004 to 0.020%. It is further preferably 0.005 to 0.010%.

[0102] Here, the total content of the Nb group elements means the total content of at least one of Nb, V, Mo, Ta, and W.

[0103] In addition, the slab described above can contain, as an optional element, at least one of the following elements in mass%: Cu: 0.40% or less, Bi: 0.010% or less, B: 0.080% or less, P: 0.50% or less, Ti: 0.015% or less, Sn: 0.10% or less, Sb: 0.10% or less, Cr: 0.30% or less, Ni: 1.00% or less.

[0104] These optional elements can be contained according to known purposes, and thus the lower limit of the content of the optional elements does not necessarily have to be set, and the lower limit can be 0%.

[0105] The chemical composition of the slab described above can be measured by the analysis method described above, as with the chemical composition of the grain-oriented magnetic steel sheet as a final product.

[0106] (Hot rolling process) The hot rolling step is a step of performing hot rolling of a slab heated to a prescribed temperature (for example, 1100 to 1400°C) to obtain a hot-rolled steel sheet. In the hot rolling step, after, for example, rough rolling of a silicon steel raw material (slab) heated by the heating step, finish rolling is performed to produce a hot-rolled steel sheet of a prescribed thickness, for example, 1.8 to 3.5 mm. After the finish rolling is completed, the hot-rolled steel sheet is coiled at a prescribed temperature.

[0107] When the process including the nitriding step at or after the decarburization annealing, the strength of MnS as the inhibitor is not so required, and therefore, if the productivity is considered, the slab heating temperature can be set to 1100 to 1280°C.

[0108] (Hot-rolled sheet annealing step) The hot-rolled sheet annealing step is a step of annealing the hot-rolled steel sheet obtained in the hot rolling step at prescribed temperature conditions (for example, 750 to 1200°C for 30 seconds to 10 minutes) to obtain an annealed steel sheet. The hot-rolled sheet annealing is generally performed by annealing the hot-rolled steel sheet after the hot rolling step to control the recrystallization rate, residual strain, crystal grain diameter, and the like of the steel sheet structure, and is also performed in order to optimally adjust the precipitate form in the steel. For example, in the high-temperature slab heating process, it is a step of finally controlling the form of precipitates such as AlN, and the conditions are adjusted in such a manner that the precipitates are uniformly and finely precipitated. As the hot-rolled sheet annealing, for example, in order to appropriately precipitate AlN and the like after heating the steel sheet to 1050 to 1150°C, slow cooling to an intermediate temperature (850 to 950°C) can be performed for 50 to 150 seconds, and then water cooling can be performed.

[0109] (Cold rolling step) The cold rolling step is a step of obtaining, for example, a cold-rolled steel sheet having a thickness of 0.10 to 0.50 mm by cold rolling the annealed steel sheet obtained in the hot-rolled sheet annealing step once or a plurality of times (2 or more times) via annealing (intermediate annealing) (for example, 80 to 95% in total cold rolling rate). In order to improve the magnetic properties, for example, the interpass temperature of cold rolling can be set to about 100 to 300°C.

[0110] (Local rapid heating step) In the present embodiment, the cold-rolled steel sheet after the cold-rolling step is subjected to local rapid heating for forming a local heating region. As the rapid heating method, there is no particular limitation as long as the steel sheet can be locally heated. For example, the following methods can be employed: a method in which a point electrode is brought into contact with the front and back surfaces of the steel sheet to pass an electric current through the steel sheet to heat it, a method in which a laser or an electron beam or the like is irradiated onto the surface of the steel sheet to heat it, a method in which local heating is performed by induction heating, a method in which a contact heat sheet is used to heat it, and the like. As the size of each local heating region, a dot-shaped region having a diameter of about 10 μm to 10 mm or a linear region having a width of about 10 μm to 10 mm can be set. In addition, the electrode for the passage of the electric current can be set as a circular electrode as described above, or can be set as a linear electrode.

[0111] Note that, regarding the size of the local heating region, the minimum diameter and the minimum width depend on the shape of the point electrode, the technology for reducing the condensing diameter of the laser or the electron beam. It is possible in principle to further reduce the size of the local heating region, but if the current situation is taken into consideration in which the nucleus of the recrystallized grain is about 1 μm in size, it can be considered that an effect is obtained if the size of the local heating region is 1 μm or more. In industry, it is sufficient that the minimum diameter and the minimum width described above are set to 10 μm or more. In addition, regarding the size of the local heating region, if the maximum diameter and the maximum width exceed 10 mm, the area ratio of the high-Goss orientation grains, for which the angle deviation Θ and the angle deviation φ outside the local heating region are relatively large, becomes more. In this case, it becomes difficult to obtain the effect of the local rapid heating.

[0112] In the local rapid heating, the heating rate at the center portion observed from the local heating region in the sheet thickness direction and at the 1 / 5 portion of the sheet thickness of the steel sheet is 500°C / sec or more. If the heating rate in the above-described region is 500°C / sec or more, it is possible to control the structure of the local heating region preferably to a recovered structure or a recrystallized structure. The above-described heating rate is preferably 2000°C / sec or more, and further preferably 10000°C / sec or more. On the other hand, the upper limit of the above-described heating rate is not particularly limited, and for example, it can be set to 1000000°C / sec.

[0113] In addition, the heating rate described above is preferably controlled in combination with and inseparably from the heating rate at the time of decarburization annealing described later. For example, in the present embodiment, the local heating after decarburization annealing is directed to the presence of coarse Goss-oriented grains in the local heating-influenced region, but in the case where the heating rate at the time of decarburization annealing is faster than the heating rate at the time of local rapid heating, it is difficult to achieve the above-described object. Therefore, although depending on the magnitude of the value of the heating rate, the heating rate at the time of local rapid heating is preferably set to be equal to or higher than the heating rate at the time of decarburization annealing. If the person skilled in the art understands the object of causing the local heating-influenced region after decarburization annealing to have coarse Goss-oriented grains, the heating rate at the time of local rapid heating and the heating rate at the time of decarburization annealing can be preferably controlled.

[0114] Note that the 1 / 5 portion of the sheet thickness of the steel sheet described above refers to a depth corresponding to 1 / 5 of the sheet thickness of the steel sheet from the surface of the steel sheet toward the sheet thickness direction.

[0115] In addition, in the local rapid heating, the maximum attained temperature becomes 700°C or higher at the center portion observed from the sheet thickness direction and the 1 / 5 portion of the sheet thickness of the steel sheet. If the maximum attained temperature is 700°C or higher in the above-described region, the structure of the local heating-influenced region can be preferably controlled to be a recovery structure or a recrystallized structure. The maximum attained temperature described above is preferably 800°C or higher, and further preferably 900°C or higher. On the other hand, the maximum attained temperature described above is preferably below the melting point of the steel sheet, for example, 1400°C or lower.

[0116] In addition, in the local rapid heating, the holding time from the attainment of the maximum temperature to the cooling to 700°C is 0.1 seconds or longer at the center portion observed from the sheet thickness direction and the 1 / 5 portion of the sheet thickness of the steel sheet. If the holding time described above is 0.1 seconds or longer in the above-described region, the structure of the local heating-influenced region can be preferably controlled to be a recovery structure or a recrystallized structure. The holding time described above is preferably 0.2 seconds or longer, further preferably 0.3 seconds or longer, and further preferably 0.4 seconds or longer. On the other hand, the upper limit of the holding time described above is not particularly limited, and for example, can be 10 seconds or shorter. This holding time from the attainment of the maximum temperature to the cooling to 700°C has a substantial influence on the formation of coarse Goss-oriented grains close to ideal Goss orientation.

[0117] In the local rapid heating, it is important to control not only the heating rate and the maximum attained temperature described above but also the holding time described above. In this holding time, a subgrain structure and a recrystallization nucleus that are advantageous for the formation of coarse Goss-oriented grains in the local heating-influenced region can be formed. By controlling the subgrain structure of the local heating-influenced region with the holding time, the structure control can be preferably performed in the subsequent process.

[0118] As described above, the method of local rapid heating is not particularly limited. For example, local rapid heating can be performed by spot electric current heating, laser irradiation, electron beam irradiation. Regardless of the method of local rapid heating, as long as the control is performed in a manner that satisfies the heating rate, the maximum temperature reached, and the holding time described above, the conditions of the method of local rapid heating can be combined by those skilled in the art to control the heating rate, the maximum temperature reached, and the holding time as targets.

[0119] For example, as long as those skilled in the art, the heating rate and the maximum temperature reached at the center portion observed from the local heating region in the plate thickness direction and at the 1 / 5 portion of the plate thickness of the steel sheet can be controlled by performing heat conduction analysis using the finite element method. Furthermore, as long as those skilled in the art, the holding time described above can be controlled by adjusting the heat dissipation conditions after the maximum temperature reached. For example, in the case of spot electric current heating, as long as the holding time of the electrode after the electric current is controlled, or the shape of the spot electrode is changed to a shape suitable for heat dissipation, the holding time of the electrode after the electric current is controlled, or the shape of the spot electrode is changed to a shape suitable for heat dissipation. In addition, in the case of laser irradiation or electron beam irradiation, as long as the irradiation speed is adjusted, or the shape of the irradiation region is changed to an ellipse or the like so that the irradiation energy is gradient from the center portion to the outer edge portion of the irradiation region, the irradiation speed is adjusted, or the shape of the irradiation region is changed to an ellipse or the like so that the irradiation energy is gradient from the center portion to the outer edge portion of the irradiation region.

[0120] Note that, in general, with respect to heating using laser irradiation, only the vicinity of the surface of the irradiated steel sheet is preferentially heated, and the inside of the steel sheet is difficult to heat. In addition, heating using laser irradiation is non-contact heating, and thus the heat dissipation after heating is fast, and it is difficult to maintain the temperature. Therefore, when laser irradiation heating is performed as local rapid heating, in order to cause the cold worked structure of the laser irradiation region to recover or recrystallize, it is necessary to control the conditions to heat not only the surface of the steel sheet but also the inside of the steel sheet, and to slow the cooling rate to make the subgrain structure of the laser irradiation region relatively coarse. The laser irradiation conditions for performing local rapid heating are completely different from the laser irradiation conditions for performing magnetic domain refinement. For example, even if the laser irradiation conditions for performing magnetic domain refinement (typically 0.5 to 50 mJ / mm 2 ) are applied to the present embodiment, the structure of the local heating region will not be optimally controlled, and coarse Goss-oriented grains close to ideal Goss orientation will not be formed in the steel sheet after the decarburization annealing process. In addition, the same applies to electron beam irradiation. Even if the electron beam irradiation conditions for performing magnetic domain refinement are applied to the present embodiment, the structure of the local heating region will not be optimally controlled, and coarse Goss-oriented grains close to ideal Goss orientation will not be formed in the steel sheet after the decarburization annealing process.

[0121] Note that even if simply increasing the input power of laser irradiation or electron beam irradiation, it is difficult to form a coarse grain with a nearly ideal Goss orientation. For example, in the case of rapid heating by laser irradiation or electron beam irradiation, in order to secure a temperature region in which the grains in the region after the rapid heating are used for grain growth, it is preferable to set the beam shape to be elliptical or adjust the scanning speed or the like.

[0122] In the past, in an electromagnetic steel sheet, laser irradiation or electron beam irradiation was performed in order to control the magnetic domain of a steel sheet after secondary recrystallization to reduce the iron loss. In these laser irradiation or electron beam irradiation conditions, the heating from the surface of the steel sheet is about 20 μm, and thus the heat dissipation after heating is fast. Therefore, in the past conditions, it is difficult to secure the above-mentioned holding time from after reaching the maximum temperature to cooling to 700°C. That is, in the past laser irradiation or electron beam irradiation conditions, it is possible to make the irradiated portion function as a growth barrier of secondary recrystallized grains, but it is difficult to form a coarse grain with a Goss orientation close to an ideal Goss orientation as in the present embodiment. In order to form a coarse grain with a Goss orientation close to an ideal Goss orientation by laser irradiation or electron beam irradiation, it is necessary to study the conditions of laser irradiation or electron beam irradiation as described above.

[0123] In addition, the local heating affected regions on the surface of the steel sheet can be appropriately arranged according to the purpose. In the manufacturing method of the present embodiment of the direction electromagnetic steel sheet, it is only necessary to control the shape of the secondary recrystallized grains in such a manner that the secondary recrystallized grains have a flattened tendency extending in the rolling right-angle direction C and being flattened in the rolling direction L. For example, the larger the interval of the local heating affected regions in the rolling direction L, the more likely the secondary recrystallized grain diameter becomes coarse in the rolling direction L. Similarly, the larger the interval of the local heating affected regions in the rolling right-angle direction C, the more likely the secondary recrystallized grain diameter becomes coarse in the rolling right-angle direction C. The arrangement of the rolling direction L and the rolling right-angle direction C of these local heating affected regions affects each other. For example, if the interval in the rolling direction L is large, even if the interval in the rolling right-angle direction C is small, the secondary recrystallized grain diameter can become coarse in the rolling right-angle direction C. In addition, the chemical composition of the steel and the temperature gradient during the heating process of the finish annealing described later also affect the grain growth of the secondary recrystallized grains. Therefore, it is only necessary to control these conditions in combination to control the above-mentioned flattened shape. As long as those skilled in the art, by appropriately adjusting the arrangement of the local heating affected regions and other conditions, it is possible to control the secondary recrystallized grains to the above-mentioned flattened shape.

[0124] (Decarburization annealing step) In the decarburization annealing process, the cold-rolled steel sheet after the local rapid heating process is subjected to decarburization annealing (primary annealing). By this decarburization annealing, the presence frequency of the Goss-oriented grains formed in the local heating-influenced region is increased, the grain size of the Goss-oriented grains is increased, and coarse Goss-oriented grains having an orientation close to the ideal Goss orientation can be preferably formed. As the decarburization annealing conditions, the heating rate is set to 10 to 10,000°C / sec, the annealing temperature is set to 700 to 900°C, and the annealing time is set to 10 to 600 seconds. In addition, by subjecting the cold-rolled steel sheet to decarburization annealing, C contained in the cold-rolled steel sheet is removed. In order to remove "C" contained in the cold-rolled steel sheet, the decarburization annealing is preferably performed in a wet atmosphere.

[0125] In addition, it is effective to reduce the primary recrystallized grain size by controlling the conditions of the hot rolling and the hot-rolled sheet annealing, or by lowering the decarburization annealing temperature as necessary. The primary recrystallized grain size is not particularly limited, but is preferably 8 to 30 μm.

[0126] In addition, in the present embodiment, coarse Goss-oriented grains having an orientation close to the ideal Goss orientation are formed in large quantities in the local heating-influenced region. Therefore, it is not necessary to newly form Goss-oriented grains in the decarburization annealing. The heating rate of the decarburization annealing can be 10,000°C / sec or less as described above, but it is preferable to set the heating rate of the decarburization annealing to be low, and to form {111} <112> -oriented grains and {411} <148> -oriented grains which are easily eroded by the matrix portion (local heating-non-influenced region). For example, the heating rate of the decarburization annealing is preferably 300°C / sec or less, further preferably 200°C / sec or less, and further preferably 100°C / sec or less.

[0127] In addition, the decarburization oxidation amount and the state of the surface oxidation layer affect the formation of the glass film. Therefore, in the decarburization annealing, the oxidation degree (PH2O / PH2) in the annealing atmosphere (furnace atmosphere) can be set to 0.01 to 0.15. Note that the oxidation degree PH2O / PH2 can be defined by the ratio of the water vapor partial pressure PH2O to the hydrogen partial pressure PH2 in the atmosphere.

[0128] (Nitriding treatment) The nitriding treatment is a treatment effective in the low-temperature slab heating process in which the slab heating temperature is 1280°C or lower, and is an important process for adjusting the strength of the inhibitors in the secondary recrystallization. The nitriding treatment increases the nitrogen content of the steel sheet by about 40 to 200 ppm during the period from the start of the decarburization treatment to the start of the secondary recrystallization in the finish annealing. As the nitriding treatment, for example, there can be mentioned a treatment in which annealing is performed in an atmosphere containing a gas having a nitriding ability such as ammonia, a treatment in which a decarburized annealed steel sheet to which an annealing separator containing a powder having a nitriding ability such as MnN is applied is subjected to finish annealing, and the like. The nitriding amount after the nitriding treatment is preferably set to 130 to 350 ppm, and further preferably set to 150 to 250 ppm.

[0129] (Annealing separator application process) The annealing separator application process is a process in which an annealing separator is applied to the decarburized annealed steel sheet. As the annealing separator, for example, an annealing separator in which MgO is the main component, an annealing separator in which Al2O3 is the main component can be used. The decarburized annealed steel sheet to which the annealing separator is applied is subjected to finish annealing in the next finish annealing process in a state in which it is coiled into a coil shape.

[0130] (Finish annealing process) The finish annealing process is a process in which finish annealing (secondary annealing) is performed on the decarburized annealed steel sheet to which the annealing separator is applied to generate secondary recrystallization. This process causes the {100} <001> oriented grains to grow preferentially by causing the secondary recrystallization to proceed in a state in which the growth of the primary recrystallized grains is inhibited by the inhibitors, thereby causing the magnetic flux density to be increased dramatically.

[0131] In the finish annealing, the decarburized annealed steel sheet to which the annealing separator is applied and dried is held in a temperature range of 1000°C to 1300°C for 10 to 60 hours. The atmosphere at the time of the finish annealing is set to, for example, a nitrogen atmosphere or a mixed atmosphere of nitrogen and hydrogen.

[0132] Further, in the present embodiment, in the heating process of the finish annealing, as long as the temperature gradient exceeding 0.5°C / cm, preferably a temperature gradient of 1.0°C / cm or more is given to the boundary between the primary recrystallized region and the secondary recrystallized region in the steel sheet while generating the secondary recrystallization. For example, as long as the temperature gradient described above is given to the steel sheet in the secondary recrystallized grain growth in the temperature range of 800°C or more in the heating process of the finish annealing. The direction in which the temperature gradient described above is given is set to the rolling right angle direction C. Further, the temperature gradient described above is appropriately changed depending on the chemical composition of the steel. For example, if the chemical composition in which the secondary recrystallized grains easily grow preferentially, the temperature gradient exceeding 0.5°C / cm is enough (preferably 1.0°C / cm or more), on the other hand, if the chemical composition in which the secondary recrystallized grains hardly grow preferentially, the temperature gradient exceeding 1.0°C / cm is preferable.

[0133] The method of giving the temperature gradient is not particularly limited, and a publicly known method can be applied. For example, using an annealing furnace of a box type, when a steel sheet in a coil shape is set in the furnace and heated, the position, arrangement of the heating device, temperature distribution in the annealing furnace can be controlled in a manner that a sufficient temperature difference is generated from the upper portion toward the lower portion of the coil or from the outside toward the inside. Alternatively, a temperature distribution can be formed in the coil to be annealed by arranging an induction heating, high frequency heating, electric current heating device or the like and actively heating only a part of the coil.

[0134] If the temperature gradient is given to the steel sheet in the heating process of the finish annealing, the secondary recrystallized grains having a sharp orientation are generated in the portion of the coil reaching the secondary recrystallization initiation state early, and the secondary recrystallized grains grow preferentially due to the temperature gradient. For example, the secondary recrystallized grains can grow in the entire coil.

[0135] (Inert film forming step) On the steel sheet after the finish annealing, a coating solution containing phosphoric acid or a phosphate, chromic anhydride or a chromate, and colloidal silica is applied and baked (for example, at 350°C to 1150°C for 5 to 300 seconds) to form an inert film.

[0136] By the above procedure, the oriented electromagnetic steel sheet of the present embodiment can be manufactured. With respect to the oriented electromagnetic steel sheet of the present embodiment manufactured by complexly and inseparably controlling each condition of each procedure, the deviation of the crystal orientation of the secondary recrystallized grains from the ideal Goss orientation is extremely small, the average of the angle deviation φ at each measurement point in the rolling direction L is small, the grains do not grow coarsely with respect to the rolling direction L, and the shape of the grains has a flat tendency of extending in the rolling right angle direction C and being flattened in the rolling direction L. Therefore, both the magnetic flux density and the magnetostriction are excellent, although the temperature gradient is given to the steel sheet at the time of the secondary recrystallization.

[0137] [Example 1] Next, the effects of the present application are specifically explained in detail by examples. The conditions in the examples are one condition example adopted in order to confirm the workability and effects of the present application, and the present application is not limited to this one condition example. The present application can adopt various conditions as long as the gist of the present application is not deviated from and the object of the present application is achieved.

[0138] A decarburization annealed steel sheet having the chemical compositions shown in Table 2 was manufactured using a slab having a chemical composition adjusted as a raw material. Note that these chemical compositions were measured based on the above-described method. In Table 2, "-" indicates that control and manufacture considering the content, and measurement of the content were not performed.

[0139] In manufacturing the above-described decarburization annealed steel sheet, the slab was heated to 1150°C to be subjected to hot rolling to manufacture a hot rolled steel sheet having a sheet thickness of 2.6 mm. The hot rolled steel sheet was heated to 1100°C, and then after hot rolled sheet annealing at 900°C was performed, pickling was performed to remove the oxide scale generated on the surface. One cold rolling or multiple cold rollings with intermediate annealing was performed on these steel sheets to manufacture a cold rolled steel sheet having a final sheet thickness of 0.22 mm.

[0140] The above-described cold rolled steel sheet was subjected to local rapid heating under the conditions shown in Tables 3 to 7. Note that in spot welding, a copper electrode having a diameter of 1 mm was used as the contact portion with the steel sheet, and on this basis, the electrode shape other than the contact portion with the steel sheet, electrode pressing force, current, current time, electrode holding time after current, and the like were complexly changed to control the heating rate, maximum temperature reached, and holding time from when the maximum temperature was reached to when the temperature was cooled to 700°C (holding time at 700°C or higher) respectively. In laser heating, a fiber laser was used, and the condensing spot diameter in the rolling direction of the laser (i.e., the diameter including 86% of the laser output power) was set to 30 μm (except for Test Nos. 71 and 72), and on this basis, the laser irradiation energy density, laser scanning speed, shape of the laser irradiation region, and the like were complexly changed to control the heating rate, maximum temperature reached, and holding time at 700°C or higher respectively. As long as those skilled in the art, each condition of the local rapid heating method can be combined to control the heating rate, maximum temperature reached, and holding time at 700°C or higher as targets.

[0141] Note that, in the case of Test No. 69, by making the laser beam elongated in the scanning direction, the holding time from reaching the maximum temperature to cooling to 700°C was controlled to 0.2 seconds at the time of local rapid heating, and a coarse high-Goss orientation grain having an orientation close to an ideal Goss orientation was formed in the local heating region. In the case of Test No. 70, a general laser irradiation condition for performing magnetic domain refinement was applied. In the case of Test No. 71, the condensing spot diameter was set to 0.5 mm, the laser irradiation energy density was set to 2.0 J / mm 2 , and control was performed in a manner that the crystal grain boundary of the laser beam irradiation portion eventually becomes a secondary recrystallized grain. In the case of Test No. 72, the condensing spot diameter was set to 0.5 mm, the laser irradiation energy density was set to 30.0 J / mm 2 , and control was performed in a manner that the crystal grain boundary of the laser beam irradiation portion eventually becomes a secondary recrystallized grain.

[0142] In the table, the heating method of the local rapid heating is "no treatment" indicating that no local rapid heating is performed. The "line or dot" of the local heating condition indicates the shape of the local heating region on the surface of the cold-rolled steel sheet, and the "rolling direction interval" and "width direction interval" of the local heating condition indicate the interval in the rolling direction and the direction perpendicular to the rolling direction on the surface of the cold-rolled steel sheet at which the local heating region is arranged. The local heating regions are arranged at equal intervals in the rolling direction and the direction perpendicular to the rolling direction. Note that, when the local heating region is arranged on the surface of the cold-rolled steel sheet, it is arranged in a manner that avoids the distribution of the local heating region from becoming uneven.

[0143] In addition, in the table, the width direction interval of the local heating condition of the local rapid heating is "end 10" indicating that the local heating region is formed only at a position 10 mm from the end of the steel sheet in the direction perpendicular to the rolling direction.

[0144] The cold-rolled steel sheet after the local rapid heating was subjected to decarburization annealing under the conditions shown in Tables 3 to 7. Note that, in the decarburization annealing, the degree of oxidation (PH2O / PH2) in the annealing atmosphere (furnace atmosphere) was set to 0.13.

[0145] The manufactured decarburization annealed steel sheet was subjected to nitriding treatment at 750°C in a nitrogen-hydrogen-ammonia atmosphere, and the nitrogen content of the steel sheet was set to 220 ppm. Further, an annealing separator having MgO as a main component was applied, and finish annealing was performed.

[0146] In the heating process of the finish annealing, the steel sheet was heated to 1000°C at 15°C / hr in a mixed atmosphere of hydrogen and nitrogen, and then heated to 1200°C at the heating rate shown in Tables 3 to 7. In addition, in the heating process of the finish annealing, a temperature gradient shown in Tables 3 to 7 was given to the boundary between the primary recrystallized region and the secondary recrystallized region of the steel sheet in the C direction perpendicular to the rolling direction in the temperature range of 800°C or higher. Note that in Tables 3 to 7, "<1.0" in the temperature gradient in the heating process of the finish annealing indicates that the temperature gradient in the heating process was not substantially controlled. After the heating process of the finish annealing, the steel sheet was held at 1200°C for 20 hr in a hydrogen atmosphere.

[0147] On the steel sheet after the finish annealing, an insulating coating film was formed by applying a coating solution of an insulating coating film containing colloidal silica and a phosphate as main components, with chromic anhydride added as necessary, and baking.

[0148] For the manufactured grain-oriented magnetic steel sheet, the chemical composition of the base steel sheet, the average value aveφ of the angle deviation φ, the number-based 10% particle size D10, and the average value aveD of the particle size D were measured based on the above-described methods. L L L C C The results are shown in Tables 7 to 13. In Table 13, "-" indicates that the control and the manufacturing considering the content were not performed, and the measurement of the content was not performed. In addition, for the manufactured grain-oriented magnetic steel sheet, various characteristics were evaluated. The evaluation results are shown in Tables 7 to 12.

[0149] The magnetic characteristics of the grain-oriented magnetic steel sheet were measured based on the single sheet tester (SST) method prescribed in JIS C 2556:2015.

[0150] From the obtained grain-oriented magnetic steel sheet, 20 single sheet samples of 100 mm x 500 mm in size were prepared, and single sheet magnetic measurement was performed. As the magnetic characteristics, the magnetic flux density B8 (T) in the rolling direction of the steel sheet when excited at 800 A / m was measured. A case where the magnetic flux density B8 was 1.945 T or more was judged to be acceptable. In addition, as a reference, the iron loss W 17 / 50 (W / kg) defined by the electric power loss per unit weight (1 kg) of the steel sheet was measured under conditions of an alternating current frequency: 50 Hz, and an excitation magnetic flux density: 1.7 T.

[0151] ​​​​Further, as the magnetic characteristics, magnetostriction λp-p@1.7T (difference between minimum and maximum values of magnetostriction at 1.7T) generated in the steel sheet under conditions of an alternating current frequency of 50 Hz and an excitation magnetic flux density of 1.7T was measured. Specifically, the maximum length L max and the minimum length L min of the test piece (steel sheet) under the above excitation conditions, and the length L0 of the test piece at a magnetic flux density of 0T were used to calculate λp-p@1.7T = (L max -L min ) ÷ L0.

[0152] Based on the above magnetic characteristic values, the magnetostriction speed level at 1.7T was calculated. With respect to the magnetostriction speed level Lva (unit: dB), the waveform obtained with a sampling frequency of 6.4 kHz for a magnetostriction waveform of 2 cycles or more was subjected to Fourier transform, and the magnetostriction amount λ (fi) (0 Hz to 3.2 kHz) at each frequency obtained was used to derive the following Equation 1. With respect to the magnetostriction speed level Lva, the 200 Hz component was investigated.

[0153] Lva = 20 x log 10 [{ρc x {∑ (2 1 / 2 π x fi x λ (fi) x α (fi)) 2} 1 / 2} / P0] (Equation 1) where, ρ: density of air (kg / m 3 ) c: sound velocity (m / sec) P0: minimum pressure (Pa) of sound of 1 kHz that can be heard by a human, fi: frequency (Hz) λ (fi): magnetostriction amount at each frequency after Fourier transform α (fi): A characteristic at frequency fi π: circular constant Note that, in the calculation of Lva@1.7T, the following values were substituted.

[0154] ρ = 1.185 (kg / m 3 ) c = 346.3 (m / sec) P0 = 2 x 10 -5 (Pa) When the magnetic flux density B8 is 1.945T or more and the magnetostriction speed level Lva@1.7T is 41 dB or less, it is determined that both the magnetic flux density and the magnetostriction characteristics are good.

[0155] The inventive grain-oriented magnetic steel sheets of Nos. 1 to 98 are preferably controlled in aveφ L , D L 10 and aveD C . These inventive grain-oriented magnetic steel sheets have excellent magnetic flux density and magnetostrictive properties. In addition, the iron loss is also excellent.

[0156] On the other hand, the grain-oriented magnetic steel sheets of Nos. 1 to 98 as comparative examples are not preferably controlled in aveφ L , D L 10 or aveD C . These comparative examples as grain-oriented magnetic steel sheets do not have preferable magnetic flux density or magnetostrictive properties.

[0157] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] [Table 9] [Table 10] [Table 11] [Table 12] [Table 13] Industrial Applicability According to the above-described aspect of the present application, it becomes possible to provide a grain-oriented magnetic steel sheet which has excellent both magnetic flux density and magnetostrictive properties even if a technique of imparting a temperature gradient to the steel sheet at the time of secondary recrystallization is applied, and thus has high industrial applicability.

[0158] Explanation of Symbols 1 decarburized annealed steel sheet 2 locally heated affected region 3 Partial heating non-affected area (base portion) 4 Partial heating area boundary 5 Partial heating affected area boundary 14 High aspect ratio grain 15 Large high aspect ratio grain 21 Rolling direction 22 Width direction (rolling right angle direction)

Claims

1. A directional electromagnetic steel plate, characterized in that, Let α be the deviation angle from the ideal Gaussian orientation with the rolling surface normal direction Z as the rotation axis, β be the deviation angle from the ideal Gaussian orientation with the rolling right-angle direction C as the rotation axis, and γ be the deviation angle from the ideal Gaussian orientation with the rolling direction L as the rotation axis. Let (α, β, γ) be the deviation angle of the crystal orientation measured at one measurement point on the plate surface. Let φ be the angular deviation at that one measurement point. 2 +β 2 ) 1 / 2 The average value of the angular deviation φ obtained from multiple measuring points spaced 1 mm apart along the rolling direction L is defined as aveφ. L At that time, the aveφ L Satisfy aveφ L ≤3.5° The deviation angles of the crystal orientation measured at two adjacent measurement points with a spacing of 1 mm on the plate are denoted as (α1, β1, γ1) and (α2, β2, γ2), which satisfy [(α2-α1)]. 2 +(β2-β1) 2 +(γ2-γ1) 2 ] 1 / 2 The midpoint between two measurement points with an angle ≥1.0° is defined as the grain boundary GB. The grain size in the rolling direction L, calculated based on the grain boundary GB, is defined as D in mm. L The particle size D is obtained along the rolling direction L. L Arranged in descending order, and counting the largest particles by their number as the basis, the 10% of the particle size is defined as D in mm. L At 10 o'clock, the D L 10 satisfies D L 10≤100-15×aveφ L , The grain size in the rolling right-angle direction C, calculated based on the grain boundary GB, is defined in mm as D. C The particle size D is determined along the rolling right-angle direction C. C The average value is defined as aveD C At that time, the aveD C Satisfy aveD C ≥50.

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