WO2021054371A1 - 方向性電磁鋼板 - Google Patents
方向性電磁鋼板 Download PDFInfo
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- WO2021054371A1 WO2021054371A1 PCT/JP2020/035119 JP2020035119W WO2021054371A1 WO 2021054371 A1 WO2021054371 A1 WO 2021054371A1 JP 2020035119 W JP2020035119 W JP 2020035119W WO 2021054371 A1 WO2021054371 A1 WO 2021054371A1
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- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
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- H01F1/16—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of sheets
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
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Definitions
- the present invention relates to grain-oriented electrical steel sheets.
- the present application claims priority based on Japanese Patent Application No. 2019-170881 filed in Japan on September 19, 2019, the contents of which are incorporated herein by reference.
- the grain-oriented electrical steel sheet is a steel sheet in which Si is contained in an amount of about 0.5 to 7% by mass and the crystal orientation is integrated in the ⁇ 110 ⁇ ⁇ 001> orientation (Goth orientation). Electrical steel sheets are used as soft magnetic materials for iron core materials of transformers and other electrical equipment.
- the grain-oriented electrical steel sheet includes a base steel sheet, a glass coating, and a tension-applying insulating coating.
- the glass film is formed on the base steel sheet.
- the tensioning insulating coating is formed on the glass coating.
- the glass coating is an oxide mainly composed of forsterite (Mg 2 SiO 4 ), which contributes to tension application and insulating properties.
- the glass coating also has a role of enhancing the adhesion of the tension-applying insulating coating to the base steel sheet. Therefore, it is required to improve the adhesion of the glass coating to the base steel sheet.
- Patent Document 1 Japanese Patent Application Laid-Open No. 2012-214902
- Patent Document 2 Japanese Patent Application Laid-Open No. 2018-53346
- Patent Document 11 Japanese Patent Application Laid-Open No. 11 It is described in Japanese Patent Application Laid-Open No. 61356 (Patent Document 3).
- the grain-oriented electrical steel sheet disclosed in Patent Document 1 is a grain-oriented electrical steel sheet containing Si: 1.8 to 7% in mass% and having a primary film containing forsterite as a main component on the surface. It is characterized by containing one or more of Ce, La, Pr, Nd, Sc, and Y in a basis weight of 0.001 to 1000 mg / m 2 per side.
- the grain-oriented electrical steel sheet disclosed in Patent Document 2 is characterized in that the void area ratio in the cross section of the glass film formed between the insulating film and the mother steel sheet is 20% or less.
- the peak intensity of Si obtained by glow discharge emission analysis performed from the surface of the oxide film is 1/2 or more of the peak intensity of Al, and the peak of Si is from the surface of the oxide film.
- the depth to the position is within 1/10 of the depth from the surface of the oxide film to the peak position of Al.
- the present invention has been made in view of the above problems, and an object of the present invention is to provide a grain-oriented electrical steel sheet having excellent adhesion of a glass coating.
- the gist of the present invention is as follows.
- the grain-oriented electrical steel sheet according to one aspect of the present invention is Base steel plate and The glass coating arranged on the base steel plate and A tension-applying insulating coating arranged on the glass coating is provided.
- the average chemical composition of the base steel sheet and the glass coating is mass%. C: 0.010% or less, Si: 2.5-4.0%, Mn: 0.01-1.00%, N: 0.010% or less, sol. Al: 0.010% or less, insol.
- Al 0.005 to 0.030%, Mg: 0.05 to 0.20%, O: 0.05 to 0.40%, Ti: 0 to 0.020%, S: 0.010% or less, P: 0.030% or less, Sn: 0 to 0.50%, Cr: 0 to 0.50%, Cu: 0 to 0.50%, Bi: 0-0.0100%, Se: 0 to 0.020%, Sb: 0 to 0.50%, and
- the rest consists of Fe and impurities Regarding the glow emission spectroscopic spectra of Al and Si obtained by performing glow discharge emission analysis in the depth direction from the surface of the glass coating.
- the surface of the glass coating was set as the measurement start time Ts.
- the time when Al reaches the maximum emission intensity is defined as T Al p.
- the emission intensity of Al in the T Al p is defined as F (T Al p)
- the time at which Si is maximum luminous intensity is defined as T Si p
- F (T Si p) When the emission intensity of Al in the T Si p is defined as F (T Si p), Said Ts, and the T Al p, and the F (T Al p), and the T Si p, wherein the F (T Si p) but, 0.05 ⁇ F (T Si p ) / F (T Al p ) ⁇ 0.50, and 2.0 ⁇ (T Al p- Ts) / (TS i p- Ts) ⁇ 5.0 Meet.
- the thickness of the base steel sheet may be 0.17 mm or more and less than 0.22 mm.
- the average chemical composition in mass%, Cr: 0.01-0.50%, Sn: 0.01 to 0.50%, Cu: 0.01-0.50%, Bi: 0.0010-0.0100%, Se: 0.001 to 0.020%, and Sb: 0.01-0.50%, It may contain at least one element selected from the group consisting of.
- the glow emission spectroscopic spectra of Al and Fe obtained by performing glow discharge emission analysis in the depth direction from the surface of the glass coating.
- the time when Al reaches the maximum emission intensity is defined as T Al p.
- the time when the Fe emission intensity becomes 60% of the saturation value of the Fe emission intensity is defined as T Fe 60.
- T Fe 90 The time when the Fe emission intensity becomes 90% of the saturation value of the Fe emission intensity is defined as T Fe 90,
- the T Al p , the T Fe 60, and the T Fe 90 are T Fe 60 ⁇ T Al p ⁇ T Fe 90 May be satisfied.
- the present inventors have determined the chemical composition of the base steel sheet (the average chemical composition of the base steel sheet and the glass coating) in terms of mass%, C: 0.010% or less, Si: 2.5 to 4.0%, and so on.
- Mn 0.01 to 1.00%
- N 0.010% or less
- sol. Al 0.010% or less
- Al 0.005 to 0.030%
- Mg 0.05 to 0.20%
- O 0.05 to 0.40%
- S 0.010% or less
- P 0.030% or less
- Cr 0 to 0.50%
- Bi 0 to 0.0100%
- Se 0 to 0. 020%
- Sb 0 to 0.50%
- a directional electromagnetic steel plate whose balance was Fe and impurities were targeted.
- This grain-oriented electrical steel sheet was studied for the purpose of improving the adhesion of the glass coating.
- the adhesion of the glass coating on the grain-oriented electrical steel sheet is also an issue in the previous research.
- the following approach is taken.
- the present inventors have studied to improve the adhesion of the glass coating by a completely different approach from the conventional one. As a result of the examination, it was found that if spinel (MgAl 2 O 4 ) is localized in the vicinity of the interface with the base steel sheet in the glass coating, the adhesion of the glass coating is enhanced. The present inventors have found for the first time the finding that the adhesion of the glass coating is enhanced by the localization of the spinel near the interface.
- Localization of spinel to the interface in the glass coating can be identified by the following method using glow discharge emission analysis. Specifically, after removing the tension-applying insulating film, a glow discharge emission analysis is performed in the depth direction from the surface of the glass film, and a glow emission spectroscopic spectrum (of Al) showing the emission intensity of Al and the emission intensity of Si. GDS spectrum, GDS spectrum of Si) is obtained.
- T Si p the emission intensity of Al at time T Si p
- the reason why the adhesion of the glass coating is improved when the spinel is localized near the interface, that is, when the formulas (1) and (2) are satisfied, is not clear at this time.
- Fine irregularities are formed on the surface of the base steel plate.
- the spinel When spinel is present in the vicinity of the interface with the base steel plate in the glass coating, the spinel is fitted into the recess on the surface of the base steel plate. Therefore, it is considered that the spinel exerts an anchor effect and enhances the adhesion of the glass coating to the base steel sheet. It is possible that a mechanism different from this mechanism enhances the adhesion of the glass coating to the base steel sheet.
- the grain-oriented electrical steel sheet according to the present embodiment completed based on the above knowledge has the following configuration.
- the grain-oriented electrical steel sheet according to this embodiment is Base steel plate and The glass coating placed on the base steel plate and With a tension-applying insulating coating arranged on the glass coating,
- the average chemical composition of the base steel sheet and the glass coating is mass%.
- Al 0.005 to 0.030%, Mg: 0.05 to 0.20%, O: 0.05 to 0.40%, Ti: 0 to 0.020%, S: 0.010% or less, P: 0.030% or less, Sn: 0 to 0.50%, Cr: 0 to 0.50%, Cu: 0 to 0.50%, Bi: 0-0.0100%, Se: 0 to 0.020%, Sb: 0 to 0.50%, and
- the rest consists of Fe and impurities Regarding the glow emission spectroscopic spectra of Al and Si obtained by performing glow discharge emission analysis in the depth direction from the surface of the glass coating.
- the surface of the glass coating is set as the measurement start time Ts.
- the time when Al reaches the maximum emission intensity is defined as T Al p.
- the emission intensity of Al with T Al p is defined as F (T Al p)
- the time at which Si is maximum luminous intensity is defined as T Si p
- F (T Si p) The time at which Si is maximum luminous intensity
- T Si p When the emission intensity of Al with T Si p is defined as F (T Si p), And the Ts, and the T Al p, and the F (T Al p), and the T Si p, the F and (T Si p) but, 0.05 ⁇ F (T Si p ) / F (T Al p ) ⁇ 0.50, and 2.0 ⁇ (T Al p- Ts) / (TS i p- Ts) ⁇ 5.0 Meet.
- the thickness of the base steel sheet may be 0.17 mm or more and less than 0.22 mm.
- the above-mentioned grain-oriented electrical steel sheet as the above-mentioned average chemical composition, in mass%, Cr: 0.01-0.50%, Sn: 0.01 to 0.50%, Cu: 0.01-0.50%, Bi: 0.0010-0.0100%, Se: 0.001 to 0.020%, and Sb: 0.01-0.50%, It may contain at least one element selected from the group consisting of.
- the glow emission spectroscopic spectra of Al and Fe obtained by performing glow discharge emission analysis in the depth direction from the surface of the glass coating.
- the time when Al reaches the maximum emission intensity is defined as T Al p.
- the time when the Fe emission intensity becomes 60% of the saturation value of the Fe emission intensity is defined as T Fe 60.
- T Fe 90 When the time when the Fe emission intensity becomes 90% of the saturation value of the Fe emission intensity is defined as T Fe 90,
- T Al p , the T Fe 60, and the T Fe 90 are T Fe 60 ⁇ T Al p ⁇ T Fe 90 May be satisfied.
- FIG. 1 is a perspective view showing a grain-oriented electrical steel sheet according to the present embodiment.
- the grain-oriented electrical steel sheet 1 according to the present embodiment includes a base steel sheet 10, a glass coating 11, and a tension-applying insulating coating 12.
- the glass coating 11 is arranged on the base steel plate 10.
- the glass coating 11 is arranged on the surface of the base steel plate 10 in direct contact with the surface of the base steel plate 10.
- the tension applying insulating coating 12 is arranged on the glass coating 11.
- the tension-applying insulating coating 12 is arranged on the surface of the glass coating 11 in direct contact with the surface of the glass coating 11.
- the glass coating 11 and the tension-applying insulating coating 12 are formed only on one surface of the base steel plate 10. However, as shown in FIG. 2, the glass coating 11 and the tension-applying insulating coating 12 may be formed on a pair of surfaces of the base steel plate 10.
- the chemical composition of the base steel sheet 10 provided with the glass coating 11 (the average chemical composition of the base steel plate 10 and the glass coating 11) after the tension-applied insulating coating 12 is removed can be determined by a well-known component analysis method. ..
- the component analysis method is, for example, as follows.
- the tension-applying insulating film 12 is removed from the grain-oriented electrical steel sheet 1.
- the grain-oriented electrical steel sheet 1 NaOH: 30 ⁇ 50% by weight and H 2 O: containing 50 to 70 wt%, aqueous solution of sodium hydroxide 80 ⁇ 90 ° C., soaking for 7-10 minutes ..
- the steel sheet after immersion (the base steel sheet 10 provided with the glass film 11 from which the tension applying insulating film 12 has been removed) is washed with water. After washing with water, dry with a warm air blower for a little less than 1 minute.
- the tension-applying insulating film 12 is removed, and the base steel sheet 10 provided with the glass film 11 is obtained.
- a well-known component analysis method is carried out on the base steel sheet 10 provided with the glass coating 11 after the tensioning insulating coating 12 is removed. Specifically, a drill is used to generate chips from the base steel plate 10 provided with the glass coating 11, and the chips are collected. The collected chips are dissolved in acid to obtain a solution. ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrum) is carried out on the solution to carry out elemental analysis of the chemical composition.
- ICP-AES Inductively Coupled Plasma Atomic Emission Spectrum
- Si in the chemical composition of the base steel sheet 10 provided with the glass coating 11 is determined by the method (silicate quantification method) specified in JIS G1212 (1997). Specifically, when the above-mentioned chips are dissolved in an acid, silicon oxide precipitates as a precipitate. This precipitate (silicon oxide) is filtered out with a filter paper, and the mass is measured to determine the Si content.
- the C content and S content are determined by the well-known high-frequency combustion method (combustion-infrared absorption method). Specifically, the above-mentioned solution is burned by high-frequency induction heating in an oxygen stream to detect the generated carbon dioxide and sulfur dioxide, and the C content and the S content are determined.
- combustion-infrared absorption method combustion-infrared absorption method
- the N content is determined using the well-known Inactive Gas Melt-Thermal Conductivity Method.
- the O content is determined using the well-known inert gas melting-non-dispersive infrared absorption method.
- the chemical composition of the base steel sheet 10 provided with the glass coating 11 (the average chemical composition of the base steel plate 10 and the glass coating 11) can be obtained.
- the grain-oriented electrical steel sheet according to the present embodiment contains a basic element as the above average chemical composition, and if necessary, a selective element, and the balance is composed of Fe and impurities.
- % relating to an element means mass% unless otherwise specified.
- Carbon (C) is a selective element.
- C is an essential element for the slab in order to improve the magnetic flux density.
- C is removed from the steel sheet in the manufacturing process of the grain-oriented electrical steel sheet. If C remains in excess of 0.010% as the above average chemical composition, C forms cementite (Fe 3 C) even if the content of other elements is within the range of this embodiment, and the direction is Deteriorates iron loss in cementite steel sheets. Therefore, the C content is 0.010% or less.
- the preferred upper limit of the C content is 0.006%, more preferably 0.003%.
- the C content is preferably as low as possible. Therefore, the C content may be 0%. However, excessive reduction of C content raises manufacturing costs. Therefore, the preferred lower limit of the C content is more than 0%, more preferably 0.001%.
- Si 2.5-4.0%
- Si is a basic element. Si increases the electrical resistance (specific resistance) of the steel material and reduces the iron loss of the grain-oriented electrical steel sheet.
- the Si content is less than 2.5%, even if the content of other elements is within the range of this embodiment, the steel undergoes phase transformation in the finish annealing step, and secondary recrystallization sufficiently proceeds. do not do. As a result, the above effect cannot be sufficiently obtained.
- the Si content exceeds 4.0%, even if the content of other elements is within the range of the present embodiment, the steel sheet becomes brittle and the plate-passability in the manufacturing process is remarkably lowered. Therefore, the Si content is 2.5-4.0%.
- the lower limit of the Si content is preferably 2.8%, more preferably 3.0%, still more preferably 3.2%.
- the preferred upper limit of the Si content is 3.7%, more preferably 3.6%, still more preferably 3.5%.
- Mn 0.01 to 1.00%
- Manganese (Mn) is a basic element. Mn increases the specific resistance of the grain-oriented electrical steel sheet and reduces iron loss. Mn further enhances hot workability and suppresses the occurrence of cracks in hot rolling. Mn further combines with S and / or Se to form fine MnS and / or fine MnSe. Fine MnS and fine MnSe serve as precipitation nuclei of fine AlN utilized as an inhibitor. Therefore, if the amount of fine MnS and fine MnSe deposited is large, a sufficient amount of fine AlN can be obtained.
- the Mn content is 0.01 to 1.00%.
- the preferred lower limit of the Mn content is 0.02%, more preferably 0.03%, still more preferably 0.05%.
- the preferred upper limit of the Mn content is 0.70%, more preferably 0.50%, still more preferably 0.30%, still more preferably 0.10%.
- N 0.010% or less Nitrogen (N) is a selective element. N combines with Al to form AlN during the manufacturing process of grain-oriented electrical steel sheets, and functions as an inhibitor. Therefore, N is an essential element for slabs, which are materials for grain-oriented electrical steel sheets. However, N is removed from the steel sheet in the manufacturing process of the grain-oriented electrical steel sheet. If the N content exceeds 0.010% as the above average chemical composition, a large number of blister (pores) are likely to be generated in the steel sheet even if the content of other elements is within the range of the present embodiment. Blister causes coating defects and reduces the insulating property of grain-oriented electrical steel sheets. Therefore, the N content is 0.010% or less.
- the preferred upper limit of the N content is 0.008%, more preferably 0.006%, still more preferably 0.004%.
- the N content may be 0%. However, it may be difficult to excessively reduce the N content. Therefore, the preferred lower limit of the N content is 0.001%, more preferably 0.002%.
- sol. Al 0.010% or less Acid-soluble aluminum (sol.Al) is a selective element. sol. Al combines with N to form AlN during the manufacturing process of grain-oriented electrical steel sheets, and functions as an inhibitor. However, sol. If the Al content exceeds 0.010%, Al-based inclusions remain in the steel sheet even if the other element content is within the range of the present embodiment. In this case, the iron loss of the grain-oriented electrical steel sheet deteriorates. Therefore, sol. The Al content is 0.010% or less. sol. The preferred upper limit of the Al content is 0.008%, more preferably 0.006%. sol. The Al content may be 0%. However, it may be difficult to excessively reduce the Al content. Therefore, the preferred lower limit of the Al content is 0.001%, more preferably 0.002%. In this embodiment, sol. Al means acid-soluble Al. Therefore, sol. The Al content is the content of acid-soluble Al.
- insol.Al Acid-insoluble aluminum
- insol.Al is a basic element. insol. Al is mainly derived from spinel (MgAl 2 O 4 ) formed in the finish annealing step described later. insol. If the Al content is less than 0.005%, even if the content of other elements is within the range of the present embodiment, the glass coating 11 does not have sufficient spinel, so that the adhesion of the glass coating 11 is low. .. On the other hand, insol. If the Al content exceeds 0.030%, spinel will be excessively produced even if the content of other elements is within the range of this embodiment.
- the spinel is excessively present not only at the interface between the glass coating 11 and the base steel plate 10 but also inside the glass coating 11. If the spinel is excessively present inside the glass coating 11, it becomes a source of cracks in the glass coating 11, and the adhesion of the glass coating 11 is lowered. Therefore, insol.
- the Al content is 0.005 to 0.030%. insol.
- the lower limit of the Al content is preferably 0.006%, more preferably 0.007%, still more preferably 0.010%. insol.
- the preferred upper limit of the Al content is 0.027%, more preferably 0.025%, still more preferably 0.020%.
- the Al content may be determined by the following method.
- sol. Al conforms to the method for quantifying acid-soluble aluminum described in JIS G1257-10-2: 2013 (Aluminum quantification method-Acid-soluble aluminum quantification method). Further, from the total aluminum content obtained according to the total aluminum quantification method described in JIS G1257-10-1: 2013 (aluminum quantification method-acid decomposition frame method), the above sol. The value obtained by subtracting the Al content is insol. Defined as Al content.
- Mg 0.05 to 0.20%
- Magnesium (Mg) is a constituent element (basic element) of the glass film. Therefore, the Mg content may be 0.05 to 0.20%.
- the preferred upper limit of the Mg content is 0.18%, more preferably 0.16%.
- the preferable lower limit of the Mg content is 0.08%, more preferably 0.10%.
- Oxygen (O) is a constituent element (basic element) of the glass film. Therefore, the O content may be 0.05 to 0.40%.
- the preferred upper limit of the O content is 0.30%, more preferably 0.25%.
- the lower limit of the O content is preferably 0.10%, more preferably 0.15%.
- Titanium (Ti) is a selective element. Ti promotes the formation of a glass film and preferably secures film adhesion. Therefore, the Ti content may be 0 to 0.020%.
- the preferred upper limit of the Ti content is 0.015%, more preferably 0.010%.
- the Ti content may be 0%, but the preferred lower limit of the Ti content is 0.001%, more preferably 0.003%, still more preferably 0.005%.
- S 0.010% or less Sulfur (S) is a selective element. S combines with Mn during the manufacturing process to form the inhibitor fine MnS. Therefore, S is an essential element for slabs. However, S is removed from the steel sheet in the manufacturing process of the grain-oriented electrical steel sheet. If the S content exceeds 0.010% as the above average chemical composition, even if the content of other elements is within the range of the present embodiment, MnS remains in the base steel sheet 10, resulting in iron loss. to degrade. Therefore, the S content is 0.010% or less.
- the preferred upper limit of the S content is 0.008%, more preferably 0.006%, still more preferably 0.004%.
- the S content may be 0%. However, it may be difficult to excessively reduce the S content. Therefore, the preferred lower limit of the S content is 0.001%, more preferably 0.002%.
- Phosphorus (P) is a selective element. P lowers the workability of the steel sheet during rolling. If the P content exceeds 0.030%, the workability of the steel sheet is significantly reduced even if the content of other elements is within the range of the present embodiment. Therefore, the P content is 0.030% or less.
- the preferred upper limit of the P content is 0.020%, more preferably 0.010%.
- the P content may be 0%. However, excessive reduction of P content can be difficult. Therefore, the preferable lower limit of the P content is 0.001%.
- P improves the texture and improves the magnetic property of the steel sheet.
- the preferable lower limit of the P content for effectively exerting this effect is 0.002%, and more preferably 0.005%.
- the grain-oriented electrical steel sheet according to this embodiment contains impurities as the above average chemical composition.
- the impurities are elements mixed from ore or scrap as a raw material, elements mixed from the manufacturing environment, etc., or completely purified by purification annealing when industrially manufacturing grain-oriented electrical steel sheets. It means an element or the like that remains in the steel without being allowed and is allowed within a range that does not adversely affect the grain-oriented electrical steel sheet according to the present embodiment.
- the grain-oriented electrical steel sheet according to the present embodiment has at least one selected from the group consisting of Cr, Sn, Cu, Bi, Se, and Sb in place of a part of Fe, which is the balance, as the above average chemical composition. It may contain an element.
- Chromium (Cr) is a selective element. That is, the Cr content may be 0%.
- Cr enhances the adhesion of the glass coating 11 to the base steel sheet 10 in the same manner as Sn and Cu. Cr further enhances the degree of integration of Goth-oriented crystal grains by secondary recrystallization. If even a small amount of Cr is contained, the above effect can be obtained to some extent. However, if the Cr content exceeds 0.50%, Cr oxide is generated even if the content of other elements is within the range of the present embodiment, and the magnetic properties of the grain-oriented electrical steel sheet 1 are deteriorated. .. Therefore, the Cr content is 0 to 0.50%.
- the preferred upper limit of the Cr content is 0.40%, more preferably 0.30%, still more preferably 0.20%, still more preferably 0.10%.
- the lower limit of the Cr content is preferably more than 0%, more preferably 0.01%, still more preferably 0.03%, still more preferably 0.05%.
- Tin (Sn) is a selective element. That is, the Sn content may be 0%.
- Sn enhances the adhesion of the glass coating 11 to the base steel sheet 10 in the same manner as Cr and Cu. If Sn is contained even in a small amount, the above effect can be obtained to some extent.
- the Sn content exceeds 0.50%, the secondary recrystallization becomes unstable during the manufacturing process of the grain-oriented electrical steel sheet 1 even if the other element content is within the range of the present embodiment. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 deteriorate. Therefore, the Sn content is 0 to 0.50%.
- the preferable lower limit of the Sn content is more than 0%, more preferably 0.01%, still more preferably 0.02%, still more preferably 0.03%.
- Cu 0 to 0.50% Copper (Cu) is a selective element. That is, the Cu content may be 0%. When Cu is contained, Cu enhances the adhesion of the glass coating 11 to the base steel sheet 10 in the same manner as Cr and Sn. If even a small amount of Cu is contained, the above effect can be obtained to some extent. However, if the Cu content exceeds 0.50%, the hot workability in the manufacturing process of the grain-oriented electrical steel sheet 1 is lowered even if the content of other elements is within the range of the present embodiment. Therefore, the Cu content is 0 to 0.50%.
- the lower limit of the Cu content is more than 0%, more preferably 0.01%, still more preferably 0.03%, still more preferably 0.05%.
- the preferable upper limit of the Cu content is 0.40%, more preferably 0.30%, still more preferably 0.20%, still more preferably 0.10%.
- Bi 0 to 0.0100%
- Bi bismuth
- the Bi content may be 0%.
- Bi functions as an inhibitor in the same manner as Se and Sb, and stabilizes secondary recrystallization during the production of grain-oriented electrical steel sheet 1.
- the magnetic characteristics of the grain-oriented electrical steel sheet 1 are enhanced. If even a small amount of Bi is contained, the above effect can be obtained to some extent.
- the Bi content exceeds 0.0100%, the adhesion of the glass coating 11 to the base steel sheet 10 is lowered even if the content of other elements is within the range of the present embodiment. Therefore, the Bi content is 0 to 0.0100%.
- the preferred lower limit of the Bi content is more than 0%, more preferably 0.0010%, still more preferably 0.0020%.
- the preferred upper limit of the Bi content is 0.0090%, more preferably 0.0070%, still more preferably 0.0050%.
- Se 0 to 0.020%
- Selenium (Se) is a selective element. That is, the Se content may be 0%.
- Se functions as an inhibitor in the same manner as Bi and Sb, and stabilizes secondary recrystallization during the production of grain-oriented electrical steel sheet 1.
- the magnetic characteristics of the grain-oriented electrical steel sheet 1 are enhanced. If even a small amount of Se is contained, the above effect can be obtained to some extent.
- the Se content exceeds 0.020%, the adhesion of the glass coating 11 to the base steel sheet 10 is lowered even if the content of other elements is within the range of the present embodiment. Therefore, the Se content is 0 to 0.020%.
- the preferred lower limit of the Se content is more than 0%, more preferably 0.001%, still more preferably 0.003%, still more preferably 0.005%.
- the preferred upper limit of the Se content is 0.015%, more preferably 0.010%, still more preferably 0.008%.
- Sb 0 to 0.50%
- Antimony (Sb) is a selective element. That is, the Sb content may be 0%.
- Sb functions as an inhibitor in the same manner as Bi and Se, and stabilizes secondary recrystallization during the production of grain-oriented electrical steel sheet 1.
- the magnetic characteristics of the grain-oriented electrical steel sheet 1 are enhanced. If even a small amount of Sb is contained, the above effect can be obtained to some extent.
- the Sb content exceeds 0.50%, the adhesion of the glass coating 11 to the base steel sheet 10 is lowered even if the content of other elements is within the range of the present embodiment. Therefore, the Sb content is 0 to 0.50%.
- the preferred lower limit of the Sb content is more than 0%, more preferably 0.01%, still more preferably 0.03%, still more preferably 0.05%.
- the preferred upper limit of the Sb content is 0.40%, more preferably 0.30%, still more preferably 0.20%, still more preferably 0.10%.
- the average chemical composition described above is Cr: 0.01 to 0.50%, Sn: 0.01 to 0.50%, Cu: 0 in mass%. At least selected from the group consisting of 0.01 to 0.50%, Bi: 0.0010 to 0.0100%, Se: 0.001 to 0.020%, and Sb: 0.01 to 0.50%. It preferably contains one element.
- the above average chemical composition contains at least one element of Cr: 0.01 to 0.50%, Sn: 0.01 to 0.50%, and Cu: 0.01 to 0.50%. May be good.
- Bi, Se, and Sb preferably enhance the magnetic properties of the grain-oriented electrical steel sheet 1. Therefore, the above average chemical composition contains at least one element of Bi: 0.0010 to 0.0100%, Se: 0.001 to 0.020%, and Sb: 0.01 to 0.50%. May be good.
- the glass coating 11 is formed on the base steel plate 10.
- the glass coating 11 is mainly composed of forsterite (Mg 2 SiO 4).
- forsterite Mg 2 SiO 4
- X-ray diffraction is performed on the surface from which the tensioning insulating coating 12 has been removed by the above method, and the obtained X-rays are obtained.
- the diffraction spectrum may be collated with a PDF (Power Diffraction File).
- JCPDS number: 34-189 may be used for identification of forsterite (Mg 2 SiO 4).
- JCPDS number: 34-189 may be used for identification of forsterite (Mg 2 SiO 4).
- the content of forsterite in the glass coating 11 may be 60.0% or more in mass%.
- the thickness of the glass coating 11 is not particularly limited.
- the preferable lower limit of the thickness of the glass coating 11 is 1.0 ⁇ m, and more preferably 2.0 ⁇ m.
- the preferred upper limit of the thickness of the glass coating 11 is 5.0 ⁇ m, more preferably 4.0 ⁇ m.
- the tension applying insulating coating 12 is formed on the glass coating 11.
- the tension-imparting insulating film 12 is applied to the uppermost layer of the grain-oriented electrical steel sheets 1 in order to ensure insulation between the laminated grain-oriented electrical steel sheets 1. It is formed.
- the top layer of the grain-oriented electrical steel sheet 1 may be subjected to SEM-EDS quantitative analysis to confirm the chemical composition. ..
- the quantitative analysis result of SEM-EDS shows that the Fe content is less than 80 atomic%, the P content is 5 atomic% or more, the Si content is less than 20 atomic%, and the O content is 50 atoms, excluding measurement noise. % Or more and the Mg content is 10 atomic% or less, it is determined that the directional electromagnetic steel plate 1 has the tension applying insulating film 12.
- the tension-imparting insulating coating 12 is coated with an insulating coating agent containing at least one inorganic substance such as a metal chromate salt, a metal phosphate salt, colloidal silica, polytetrafluoroethylene, a Zr compound, and a Ti compound. , Formed by baking.
- the insulating coating agent may be mainly composed of a phosphoric acid compound.
- the insulating coating agent may have a phosphoric acid compound content of 80% or more in mass%.
- the insulating coating agent for forming the tension-imparting insulating film 12 may contain one or more selected from the group consisting of colloidal silica and polytetrafluoroethylene together with the phosphoric acid compound.
- the phosphoric acid compound is, for example, sodium phosphate, aluminum phosphate, magnesium phosphate and the like.
- the thickness of the tensioning insulating coating 12 is not particularly limited.
- the preferred lower limit of the thickness of the tensioning insulating coating 12 is 0.1 ⁇ m, more preferably 0.5 ⁇ m.
- the preferred upper limit of the thickness of the tensioning insulating coating 12 is 10.0 ⁇ m, more preferably 5.0 ⁇ m.
- spinel (MgAl 2 O 4) is localized in the glass coating 11 in the vicinity of the interface with the base steel sheet 10. Specifically, after removing the tension-applying insulating film 12, glow discharge emission analysis is performed in the depth direction from the surface of the glass film 11, and a glow emission spectral spectrum showing the emission intensity of Al and the emission intensity of Si ( The GDS spectrum of Al and the GDS spectrum of Si) are obtained.
- the surface of the glass coating 11 is the measurement start time Ts
- the horizontal axis is the measurement time (unit: seconds)
- the vertical axis is the emission intensity (GDS intensity) (unit: spectrum unit).
- GDS intensity unit: spectrum unit
- FIG. 3 shows the emission spectroscopic spectrum (GDS spectrum of Al and GDS spectrum of Si). It is shown in Figure 3, the time Ts, the time T Al p, the emission intensity F (T Al p), a time T Si p, the emission intensity F a (T Si p), defined as follows.
- Measurement start time Ts In the glow emission spectroscopic spectrum, the surface of the glass coating 11 is defined as the measurement start time Ts.
- Time T Al p After removing the tension-applying insulating film 12 of the directional electromagnetic steel plate 1, glow discharge emission analysis is performed from the surface of the glass film 11 in the depth direction, and the surface of the glass film 11 is set as the measurement start time Ts, and the measurement time and Al.
- the glow emission spectroscopic spectrum of Al (GDS spectrum of Al) showing the relationship with the emission intensity of Al is obtained.
- the measurement time corresponds to the depth from the surface of the glass coating 11.
- the maximum value of the emission intensity and the time of the maximum value are specified. Defining the identified time and the time T Al p. That is, the time T Al p corresponds to the depth position (the depth position from the surface of the glass coating 11) at which the Al concentration (GDS intensity of Al) peaks.
- Emission intensity F (T Al p ) In the glow emission spectroscopic spectrum of Al (GDS spectrum of Al) described above, the maximum value of the emission intensity of Al, that is, the maximum emission intensity of Al at time T Al p is defined as F (T Al p).
- Time T Si p After removing the tension-applying insulating film 12 of the directional electromagnetic steel plate 1, glow discharge emission analysis is performed from the surface of the glass film 11 in the depth direction, and the surface of the glass film 11 is set as the measurement start time Ts, and the measurement time and Si.
- the glow emission spectroscopic spectrum of Si (GDS spectrum of Si) showing the relationship with the emission intensity of Si is obtained.
- the measurement time corresponds to the depth from the surface of the glass coating 11.
- the maximum value of the emission intensity and the time of the maximum value are specified. Defining the identified time and the time T Si p. In other words, the time T Si p is, (GDS intensity of Si) Si concentration corresponds to the depth position where the peak (depth position from the surface of the glass film 11).
- Luminous intensity F (T Si p) Glow emission spectrum of Al described above (GDS spectra of Al), the emission intensity of the corresponding Al to the time T Si p is defined as F (T Si p).
- the main component of the glass coating 11 is forsterite (Mg 2 SiO 4 ). Therefore, the GDS spectrum of Si shows a peak at the center of the glass coating 11 in the depth direction.
- the time T Si p corresponds to the center position in the depth direction of the glass film 11. That, F (T Si p) means the concentration of Al in the middle position in the depth direction of the glass film 11.
- F1 F (TS i p ) / F (T Al p).
- F1 is for typical Al concentration in the region excluding the peak position of Al concentration in the glass film 11 (F (T Si p) ), the maximum Al concentration in the glass film 11 of the (F (T Al p)) It shows the ratio and is an index showing the degree of localization of spinel in the glass coating 11.
- F2 is defined as (T Al p -Ts) / ( T Si p -Ts). As shown in FIG. 3, F2 shows the relationship between the peak position of the Al concentration and the peak position of the Si concentration (that is, the center position in the depth direction of the glass coating 11), and the spinel in the glass coating 11 It is an index showing the localized position of.
- F2 is less than 2.0, the peak position of the Al concentration is located inside the glass coating 11 of the glass coating 11 rather than near the interface with the base steel plate 10. That is, the spinel is not localized near the interface with the base steel sheet 10, but exists inside the glass coating 11.
- F1 also exceeds the upper limit of the formula (1), and as a result, the adhesion of the glass coating 11 to the base steel sheet 10 is lowered.
- F2 exceeds 5.0, the amount of the glass coating 11 produced is excessively small with respect to the amount of spinel produced. That is, the glass coating 11 is thinned. In this case, even if F1 satisfies the formula (1), the tension of the glass coating 11 required for magnetic domain subdivision is reduced. Therefore, the iron loss is reduced and the film adhesion is also reduced.
- the adhesion of the glass coating 11 to the base steel plate 10 is increased if the spinel is formed in an appropriate amount in the vicinity of the interface with the base steel plate 10 in the glass coating 11 is not clear.
- Fine irregularities are formed on the surface of the base steel plate 10.
- the spinel is present in the vicinity of the interface with the base steel plate 10 in the glass coating 11, the spinel is fitted into the recess on the surface of the base steel plate 10. Therefore, it is considered that the spinel exerts an anchor effect and enhances the adhesion of the glass coating 11 to the base steel plate 10.
- the adhesion of the glass coating 11 to the base steel sheet 10 is enhanced by a mechanism different from this mechanism.
- F1 satisfies the formula (1) and F2 satisfies the formula (2) the adhesion of the glass coating 11 to the base steel sheet 10 is enhanced, as illustrated in the examples described later.
- the above-mentioned F1 value and F2 value can be obtained by the following method.
- a sample having a rolling direction RD of 30 mm, a plate width direction TD of 40 mm, and a thickness of the grain-oriented electrical steel sheet 1 is taken from the central portion of the grain-oriented electrical steel sheet 1 in the plate width direction TD.
- the tension-applying insulating coating 12 is removed from the collected sample.
- the grain-oriented electrical steel sheet 1 NaOH: 30 ⁇ 50% by weight and H 2 O: containing 50 to 70 wt%, aqueous solution of sodium hydroxide 80 ⁇ 90 ° C., soaking for 7-10 minutes ..
- the steel sheet after immersion (the base steel sheet 10 provided with the glass film 11 from which the tension applying insulating film 12 has been removed) is washed with water. After washing with water, dry with a warm air blower for a little less than 1 minute.
- a sample is prepared in which the base steel plate 10 and the glass coating 11 are provided and the tension applying insulating coating 12 is removed.
- GDS Glow discharge emission analysis
- GDS spectrum Glow discharge emission spectrum of Al and Si
- GD-ODS high-frequency glow emission spectroscope
- an output of 30 W is applied to the depth of the glass coating 11 under an argon atmosphere (Ar pressure: 3 hPa) using the sample as a cathode.
- the GDS spectrum of Al and the GDS spectrum of Si in the direction are measured.
- the measurement area is 4 mm ⁇ , the measurement time is 100 seconds, and the measurement interval is 0.02 seconds.
- the above calculation of F1 and F2 is performed after smoothing the GDS spectrum after measurement.
- a method for smoothing the GDS spectrum for example, a simple moving average method may be used.
- Si identifies the time T Si p with the maximum emission intensity.
- Al at time T Si p obtaining the emission intensity F (T Si p).
- the measurement start time is Ts.
- F1 satisfies the formula (1)
- F2 further satisfies the formula (2). Therefore, in the glass coating 11, spinel is localized in an appropriate amount near the interface of the base steel plate 10, and the glass coating 11 has high adhesion to the base steel plate 10.
- the time when Al reaches the maximum emission intensity is defined as T Al p.
- the time when the Fe emission intensity becomes 60% of the saturation value of the Fe emission intensity is defined as T Fe 60.
- T Fe 90 When the time when the Fe emission intensity becomes 90% of the saturation value of the Fe emission intensity is defined as T Fe 90,
- the T Al p , the T Fe 60, and the T Fe 90 are T Fe 60 ⁇ T Al p ⁇ T Fe 90 ... (Equation 3) Should be satisfied.
- the spinel is localized in the vicinity of the interface between the base steel plate 10 and the glass coating 11 in the glass coating 11. It is preferable because it can be judged that it is.
- the above-mentioned "saturation value of Fe emission intensity" may be, for example, the Fe emission intensity when the measurement time of glow discharge emission analysis is 100 seconds.
- the method of manufacturing the grain-oriented electrical steel sheet 1 according to the present embodiment is not particularly limited as long as it has the above-mentioned configuration.
- the following manufacturing method is one example for manufacturing the grain-oriented electrical steel sheet 1 according to the present embodiment, and is a preferable example of the method for manufacturing the grain-oriented electrical steel sheet 1 according to the present embodiment.
- FIG. 5 is a flow chart of a method for manufacturing a grain-oriented electrical steel sheet 1 according to the present embodiment.
- a hot rolling step (S1) in which hot rolling is performed on a slab and a shrinking treatment are performed on a steel sheet (hot rolled steel sheet) after hot rolling.
- the cold-rolling step (S3) in which the steel sheet after the hot-rolled plate annealing step is cold-rolled one or more times (S30), and the cold-rolling step.
- S7 film forming step
- the prepared slab is hot-rolled to produce a hot-rolled steel sheet.
- the chemical composition of the slab is adjusted so that the average chemical composition of the base steel sheet 10 and the glass coating 11 of the grain-oriented electrical steel sheet 1 becomes the above-mentioned chemical composition.
- the Al content of the slab should be 0.01% by mass or more. If the Al content of the slab is less than 0.01% by mass, spinel is not sufficiently formed in the glass coating 11.
- the slab is manufactured by a well-known method. For example, molten steel is manufactured (melted). A slab is manufactured by a continuous casting method using molten steel.
- the prepared slab is hot-rolled using a hot-rolling machine to manufacture a steel plate (hot-rolled steel plate).
- the steel material is heated.
- the slab is placed in a well-known heating furnace or a well-known soaking furnace to heat it.
- the preferred heating temperature for the slab is 1100 to 1450 ° C.
- the preferred lower limit of the heating temperature is 1300 ° C.
- the preferred upper limit of the heating temperature is 1400 ° C.
- the heated slab is hot-rolled using a hot-rolling machine to manufacture a steel plate (hot-rolled steel plate).
- the hot rolling mill includes a rough rolling mill and a finishing rolling mill located downstream of the rough rolling mill.
- the rough rolling mill includes one or a plurality of rough rolling stands arranged in a row. Each rough rolling stand contains a plurality of rolls arranged one above the other.
- the rough rolling stand may be a reverse type. When a plurality of rough rolling stands are arranged, the rough rolling machine may be a tandem type or a reverse type.
- the finish rolling mill is equipped with a line of finish rolling stands. Each finish rolling stand contains a plurality of rolls arranged one above the other.
- the heated slab is rolled by a rough rolling mill and then further rolled by a finishing rolling mill to produce a hot-rolled steel sheet.
- the plate thickness of the hot-rolled steel sheet produced by hot rolling is not particularly limited, and a known plate thickness can be used.
- the thickness of the hot-rolled steel sheet is, for example, 2.0 to 3.0 mm.
- the hot-rolled plate annealing step (S2) is an arbitrary step and does not have to be carried out.
- the hot-rolled steel sheet produced in the hot-rolling step (S1) is annealed to obtain a hot-rolled annealed steel sheet.
- the heating method of the hot-rolled steel sheet is not particularly limited, and a well-known heating method may be adopted.
- the annealing temperature is, for example, 900 to 1200 ° C.
- the holding time at the annealing temperature is, for example, 10 to 300 seconds.
- the hot-rolled steel sheet may be pickled after the hot-rolled sheet annealing step (S2) and before the cold rolling step (S3). ..
- Cold rolling process (S3) In the cold rolling step (S3), the manufactured steel sheet (hot-rolled steel sheet or hot-rolled annealed steel sheet) is cold-rolled one or more times (S30). Cold rolling (S30) is carried out using a cold rolling machine.
- the cold rolling mill is, for example, a tandem rolling mill having a plurality of cold rolling stands arranged in a row, and each cold rolling stand includes a plurality of cold rolling rolls.
- the cold rolling mill may be one reverse type cold rolling stand.
- the cold rolling may be carried out only once (S30) or may be carried out a plurality of times (S30).
- the cold rolling may be carried out using the above-mentioned cold rolling machine, and then an intermediate annealing treatment for the purpose of softening the steel sheet may be carried out.
- the next cold rolling is carried out. That is, an intermediate annealing treatment may be performed during the cold rolling.
- the conditions of the intermediate annealing treatment to be carried out between the cold rolling and the next cold rolling are sufficient as known conditions.
- the annealing temperature in the intermediate annealing treatment is, for example, 950 to 1200 ° C., and the holding time at the annealing temperature is 30 to 1800 seconds. After reducing the strain introduced into the steel sheet (softening the steel sheet) by the cold rolling in the previous stage by the intermediate annealing treatment, the cold rolling in the next stage is carried out.
- the cold rolling is performed a plurality of times and the intermediate annealing treatment is performed between the cold rollings, the magnetic flux density of the manufactured grain-oriented electrical steel sheet 1 may be low. Therefore, the number of cold rollings and the presence or absence of intermediate annealing treatment are determined according to the characteristics and manufacturing cost required for the grain-oriented electrical steel sheet 1 to be finally manufactured.
- the preferred cumulative cold rolling rate for one or more cold rollings is 80-95%.
- the cumulative cold spread rate (%) is defined as follows.
- Cold rolling ratio (%) [(Thickness of steel sheet before the start of the first cold rolling-Thickness of the cold rolled steel sheet after the last cold rolling) / Thickness of the steel sheet before the start of the first cold rolling] ⁇ 100
- the cold rolling ratio is the cold rolling ratio in the cold rolling only once. If the cumulative reduction rate is 80% or more, a large number of recrystallized nuclei (Goth nuclei) having a Goth orientation ( ⁇ 110 ⁇ ⁇ 001> orientation) can be obtained. Further, when the cumulative reduction rate is 95% or less, the secondary recrystallization is likely to be stabilized in the finish annealing step (S6) described later.
- the steel sheet produced by the cold rolling process is wound into a coil.
- the thickness of the cold-rolled steel sheet is usually the thickness of the final product, the directional electromagnetic steel sheet 1 (the thickness of the glass coating 11 and the tension-applying insulating coating 12). It is different from the product plate thickness including).
- an aging process may be carried out in order to further improve the magnetic characteristics.
- the aging process is an arbitrary process.
- the aging (annealing) treatment is carried out during the plurality of cold rolling (S30). Specifically, after cold rolling (S30), aging treatment is carried out. Then, after the aging treatment, the next cold rolling (S30) is carried out.
- Well-known conditions are sufficient for the aging treatment. For example, in the aging treatment, the steel sheet after cold rolling (S30) is heat-treated at a temperature of 100 to 500 ° C. for 60 seconds or longer. In this case, a good secondary recrystallization structure in which the Goth orientation is accumulated can be finally obtained.
- decarburization annealing step (S4) In the decarburization annealing step (S4), the steel sheet (cold-rolled steel sheet) after the cold rolling step (S3) is subjected to decarburization annealing to develop primary recrystallization.
- the decarburization annealing step (S4) includes a temperature raising step (S41), a decarburization step (S42), and a cooling step (S43).
- the temperature raising step (S41) the steel sheet is heated to the decarburization annealing temperature Ta.
- decarburization step (S42) decarburization annealing is performed on the steel sheet heated to the decarburization annealing temperature Ta to develop primary recrystallization.
- the cooling step (S43) the steel sheet after the decarburization step (S42) is cooled by a well-known method. The details of each step will be described below.
- the temperature raising step first, the steel sheet after the cold rolling step (S3) is charged into the heat treatment furnace.
- the heat treatment furnace for decarburization annealing for example, the temperature of the cold-rolled steel sheet is raised while being controlled to the decarburization annealing temperature by high-frequency induction heating or energization heating.
- the atmosphere during the temperature raising step is a dry nitrogen atmosphere or a dry nitrogen-hydrogen mixed atmosphere in which the oxygen potential (PH2O / PH2) is 0.1 or less. When the oxygen potential in the temperature raising step exceeds 0.1, Fe-based oxides are likely to nucleate.
- the Fe oxide nucleated in the temperature raising step grows and develops during decarburization annealing.
- the presence of these during finish annealing inhibits the development of forsterite (Mg 2 SiO 4).
- Fe oxide has the effect of suppressing the solid-phase reaction between SiO 2 and MgO.
- Mg 2 SiO 4 is thinned, and spinel is less likely to be localized in the vicinity of the interface with the base steel sheet 10 in the glass coating 11.
- spinel (MgAl 2 O 4 ) is present in Mg 2 SiO 4.
- the rate of temperature rise may be 2000 ° C./sec or less, and the ultimate temperature may be 700 to 1000.
- the reached temperature is different from the decarburization annealing temperature Ta in the decarburization step.
- decarburization step (S42) In the decarburization step (S42) in the decarburization annealing step (S4), the steel sheet after the temperature raising step (S41) is held at the decarburization annealing temperature Ta to carry out decarburization annealing. As a result, primary recrystallization is developed on the steel sheet.
- the atmosphere during the decarburization step is a well-known atmosphere, for example, a wet nitrogen-hydrogen mixed atmosphere containing hydrogen and nitrogen.
- Decarburization annealing temperature Ta 800-950 ° C
- the decarburization annealing temperature Ta corresponds to the furnace temperature of the heat treatment furnace for performing decarburization annealing, and corresponds to the temperature of the steel sheet during decarburization annealing. If the decarburization annealing temperature Ta is less than 800 ° C., the crystal grains of the steel sheet after the development of primary recrystallization are too small. In this case, secondary recrystallization is not sufficiently expressed in the finish annealing step (S6). On the other hand, if the decarburization annealing temperature Ta exceeds 950 ° C., the crystal grains of the steel sheet after the development of primary recrystallization are too large.
- the holding time at the decarburization annealing temperature Ta in the decarburization step (S42) is not particularly limited.
- the holding time at the decarburization annealing temperature Ta is, for example, 15 to 150 seconds.
- the steel sheet after the decarburization step (S42) is cooled to room temperature by a well-known method.
- the cooling method may be free cooling or water cooling.
- the steel sheet after the decarburization step is allowed to cool.
- the decarburization annealing treatment is carried out on the steel sheet.
- the annealing separator coating step (S5) is carried out on the steel sheet (decarburized annealing steel sheet) after the decarburization annealing step (S4).
- the annealing separator is applied to the surface of the steel sheet.
- an aqueous slurry containing an annealing separator is applied to the surface of the steel sheet.
- the aqueous slurry is prepared by adding water to an annealing separator and stirring the slurry.
- the annealing separator contains magnesium oxide (MgO).
- MgO is the main component of the annealing separator.
- the "main component” means that the MgO content in the annealing separator is 80.0% or more in mass%.
- the annealing separator may contain a well-known additive in addition to MgO.
- the annealing separator may contain a Ti compound.
- the annealing separator of the aqueous slurry is applied on the surface of the steel sheet.
- a steel plate coated with an annealing separator on the surface is wound into a coil.
- a finish annealing step (S6) is performed.
- An annealing separating agent for an aqueous slurry may be applied onto the surface of the steel sheet to form the steel sheet into a coil, and then a baking process may be performed before the finish annealing step (S6) is performed.
- the coiled steel sheet is placed in a furnace kept at 400 to 1000 ° C. and held (baking treatment).
- the annealing separator applied on the steel sheet dries.
- the holding time is, for example, 10 to 90 seconds.
- the finish annealing step may be performed on the coiled steel sheet coated with the annealing separator without performing the annealing treatment.
- a finish annealing step (S6) is carried out on the steel sheet after the annealing separator coating step (S5) to develop secondary recrystallization.
- a two-step annealing step (low temperature annealing step (S61) and high temperature annealing step (S62)) is further carried out to form a glass coating 11 mainly composed of forsterite, and the glass coating 11 is contained.
- spinels are localized in an appropriate amount near the interface of the base steel sheet 10.
- the two-step annealing step (low temperature annealing step (S61) and high temperature annealing step (S62)) is carried out using a heat treatment furnace.
- the low temperature annealing step (S61) and the high temperature annealing step (S62) will be described.
- the low temperature annealing step (S61) is a step for forming the glass coating 11.
- the coiled steel sheet is inserted into the heat treatment furnace to raise the temperature of the steel sheet to the low-temperature annealing temperature T1.
- the holding time is t1 at the low temperature annealing temperature T1.
- the atmosphere in the furnace in the low temperature annealing step (S61) may be a mixed atmosphere of hydrogen and nitrogen.
- the low-temperature annealing temperature T1 (° C.) and the holding time t1 in the low-temperature annealing step (S61) are as follows.
- Low temperature annealing temperature T1 910-1000 ° C Retention time at 910 to 1000 ° C. t1: 50 to 120 hours
- [About low temperature annealing temperature T1] 910 to 1000 ° C. is a temperature range generated by forsterite (Mg 2 SiO 4 ), which is the main component of the glass coating 11.
- the holding time t1 at the low temperature annealing temperature T1 is 50 to 120 hours.
- the holding time t1 in the temperature range of 910 to 1000 ° C. is set to 50 to 120 hours, the temperature during the holding time t1 may be constant, or the temperature may be raised or lowered.
- the high-temperature annealing step (S62) is a step for generating spinel in the glass coating 11 generated in the low-temperature annealing step (S61) and localizing the spinel in the vicinity of the interface of the base steel sheet 10. Specifically, after the low-temperature annealing step (S61) is completed, the temperature of the steel sheet is further raised to the high-temperature annealing temperature T2. The rate of temperature rise is not particularly limited. After that, the holding time is t2 at the high temperature annealing temperature T2 shown below.
- the high temperature annealing step may be carried out in the same heat treatment furnace as the low temperature annealing step, or may be carried out in a different heat treatment furnace.
- the atmosphere in the furnace in the high temperature annealing step may be a nitrogen atmosphere.
- the high-temperature annealing temperature T2 (° C.) and the holding time t2 (hours) at T2 are as follows. High temperature annealing temperature T2: 1100-1300 ° C Holding time at high temperature annealing temperature T2 t2: 20-80 hours
- [About high temperature annealing temperature T2] 1100 to 1300 ° C. is a spinel formation temperature range.
- the glass coating 11 is sufficiently formed by the low temperature annealing step. Therefore, if the temperature is maintained in the temperature range of 1100 to 1300 ° C. in the high-temperature annealing step, Al contained in the base steel sheet 10 moves to the vicinity of the interface between the glass coating 11 and the base steel sheet 10 and reacts with forsterite. To form a spinel.
- spinel is formed in the vicinity of the interface with the base steel sheet 10 in the glass coating 11, and the spinel is localized in the vicinity of the interface.
- the high temperature annealing temperature T2 is 1100-1300 ° C.
- the holding time t2 at 1100 to 1300 ° C. is 20 to 80 hours.
- the glass coating 11 has sufficient spinel near the interface with the base steel sheet 10. Spinel is localized near the interface. Therefore, F1 satisfies the equation (1) and F2 satisfies the equation (2).
- the high temperature annealing temperature T2 may be kept constant and the holding time t2 may be held, or the holding time t2 may be held while annealing in the range of 1100 to 1300 ° C. If the holding time t2 in the temperature range of 1100 to 1300 ° C. is set to 20 to 80 hours, the temperature during the holding time t2 may be constant, or the temperature may be raised or lowered.
- the purification annealing step may be carried out after the high temperature annealing step (S62) and before the insulating film forming step (S7). If a purification annealing process is carried out, the magnetism will be further improved.
- the annealing temperature is 1000 to 1300 ° C. and the holding time is 10 hours or more in a hydrogen atmosphere.
- an insulating film forming step (S7) is further carried out after the finish annealing step (S6).
- an insulating coating forming step (S7) an insulating coating agent mainly composed of colloidal silica and phosphate is applied to the surface (on the glass coating 11) of the directional electromagnetic steel plate 1 after cooling in the finish annealing step (S6). After that, baking is carried out. As a result, the tension-applying insulating film 12 is formed on the glass film.
- the tension-applying insulating film 12 formed on the surface of the steel sheet is not particularly limited as long as it is used as the tension-applying insulating film of the grain-oriented electrical steel sheet 1, and a known tension-applying insulating film can be used. It can be used.
- a tension-imparting insulating film include a composite insulating film mainly composed of an inorganic substance and further containing an organic substance.
- the composite insulating coating is mainly composed of at least one of an inorganic substance such as a metal chromate salt, a metal phosphate salt or colloidal silica, a Zr compound, and a Ti compound, and fine organic resin particles are dispersed. It is an insulating film.
- a metal phosphate, Zr, Ti coupling agent, or a tension-applying insulating film using these carbonates or ammonium salts is preferable.
- flattening annealing for shape correction may be performed. By flattening and annealing the steel sheet, iron loss can be further reduced.
- F1 satisfies the formula (1)
- F2 satisfies the formula (2)
- the spinel in the glass coating 11 near the interface with the base steel sheet 10. Can be localized. As a result, the adhesion of the glass coating 11 to the base steel sheet 10 is improved.
- the Al content of the slab used in the hot rolling step (S1) is set to 0.01% by mass or more, and decarburization annealing is performed.
- the oxygen potential ( PH2O / PH2 ) is set to 0.1 or less, and in the low temperature annealing step (S61) and the high temperature annealing step (S62) of the finish annealing step (S6). It is important to control the annealing conditions.
- the grain-oriented electrical steel sheet 1 according to the present embodiment may be subjected to a nitriding treatment step after the decarburization annealing step (S4) and before the annealing separator coating step (S5).
- the nitriding treatment is performed on the steel sheet after the decarburization annealing step (S4) to manufacture the nitriding treated steel sheet. It suffices to carry out the nitriding process under well-known conditions.
- Preferred nitriding conditions are, for example:
- Nitriding temperature 700-850 ° C Atmosphere in a nitriding furnace (nitriding atmosphere): An atmosphere containing a gas having a nitriding ability such as hydrogen, nitrogen and ammonia.
- the nitriding treatment temperature is 700 ° C. or higher, or the nitriding treatment temperature is less than 850 ° C., nitrogen easily penetrates into the steel sheet during the nitriding treatment. In this case, the amount of nitrogen inside the steel sheet becomes sufficient in the nitriding process. Therefore, a sufficient amount of fine AlN just before the secondary recrystallization can be obtained. As a result, secondary recrystallization is sufficiently expressed in the finish annealing step (S6).
- the holding time at the nitriding treatment temperature in the nitriding treatment step is not particularly limited, but is, for example, 10 to 60 seconds.
- the grain-oriented electrical steel sheet 1 according to the present embodiment may be subjected to a magnetic domain subdivision treatment step after the finish annealing step (S6) or the insulating film forming step (S7).
- the surface of the grain-oriented electrical steel sheet 1 is irradiated with a laser beam having a magnetic domain subdivision effect, or a groove is formed on the surface.
- the grain-oriented electrical steel sheet 1 having further excellent magnetic characteristics can be manufactured.
- the conditions in the examples are one condition example adopted for confirming the feasibility and effect of the present invention.
- the present invention is not limited to this one-condition example.
- the present invention can adopt various conditions as long as the gist of the present invention is not deviated and the object of the present invention is achieved.
- a hot rolling process was performed on the above slab. Specifically, after heating the slab to 1350 ° C., the slab was hot-rolled to produce a hot-rolled steel sheet having a plate thickness of 2.3 mm.
- the hot-rolled steel sheet after the hot-rolling step was subjected to a hot-rolled sheet annealing step at an annealing temperature of 900 to 1200 ° C. and a holding time of 10 to 300 seconds. Then, a cold rolling step was carried out to produce a cold-rolled steel sheet (base steel sheet) having a plate thickness of 0.19 to 0.23 mm.
- a decarburization annealing process was carried out on the cold-rolled steel sheet.
- the decarburization annealing temperature Ta was set to 800 to 950 ° C., and the decarburization annealing temperature Ta was maintained for 100 seconds.
- a finish annealing step was carried out by applying an annealing separator containing magnesium oxide (MgO) as a main component and a Ti compound as necessary on the surface of the steel sheet.
- MgO magnesium oxide
- the surface of the grain-oriented electrical steel sheet (on the glass film) after cooling in the finish annealing step was coated with an insulating coating agent mainly composed of colloidal silica and a metal phosphate, and then baked. Through the above steps, grain-oriented electrical steel sheets with each test number were manufactured.
- Tables 1 to 6 Detailed manufacturing conditions and manufacturing results are shown in Tables 1 to 6.
- the "-" shown in the table indicates that the chemical composition is not controlled and manufactured in consideration of the content, and the content is not measured, and the manufacturing conditions and evaluation results are controlled. Or indicate that the evaluation has not been performed.
- the temperature was raised by controlling the cold-rolled steel sheet in the temperature raising step of the decarburization annealing step.
- the heat treatment furnace for the decarburization step (S42) is used without carrying out the heating step (S41) of the decarburization annealing step (without controlling the heating conditions of the cold-rolled steel sheet).
- a cold-rolled steel sheet was put in and heated to the decarburization annealing temperature Ta.
- the Al content of the slab was 0.01% by mass or more.
- the Al content of the slab was less than 0.01% by mass.
- the tension-applied insulating coating was removed from the grain-oriented electrical steel sheet by the method described above. Specifically, the grain-oriented electrical steel sheet, NaOH: 30 ⁇ 50% by weight and H 2 O: containing 50 to 70 wt%, aqueous solution of sodium hydroxide 80 ⁇ 90 ° C., and immersed for 7-10 minutes.
- the steel sheet after immersion (a base steel sheet having a glass film from which the tension-applied insulating film had been removed) was washed with water. After washing with water, it was dried with a warm air blower for a little less than 1 minute.
- the tension-applying insulating film was removed, and a base steel sheet having a glass film was obtained.
- a well-known component analysis method was carried out on the base steel sheet provided with the glass coating after the tension-applied insulating coating was removed. Specifically, a drill was used to generate chips from a base steel sheet having a glass coating, and the chips were collected. The collected chips were dissolved in acid to obtain a solution. ICP-AES was performed on the solution to perform elemental analysis of the chemical composition.
- Si in the chemical composition of the base steel sheet provided with the glass film was determined by the method (silicate quantification method) specified in JIS G1212 (1997). Specifically, when the above-mentioned chips are dissolved in an acid, silicon oxide precipitates as a precipitate. This precipitate (silicon oxide) was filtered out with a filter paper, and the mass was measured to determine the Si content.
- the C content and S content were determined by a well-known high-frequency combustion method (combustion-infrared absorption method). Specifically, the above-mentioned solution was burned by high-frequency induction heating in an oxygen stream, and the generated carbon dioxide and sulfur dioxide were detected to determine the C content and the S content.
- combustion-infrared absorption method combustion-infrared absorption method
- the N content was determined using the well-known Inactive Gas Melt-Thermal Conductivity Method.
- the O content was determined using the well-known inert gas melting-non-dispersive infrared absorption method.
- Tables 1 to 3 show the chemical composition of the base steel sheet having the glass coating (the average chemical composition of the base steel plate and the glass coating) obtained by the above analysis method.
- Glow discharge emission analysis was performed in the depth direction from the surface of the glass coating of the sample, and the GDS spectra of Al, Si, and Fe were measured. Specifically, using a high-frequency glow emission spectroscope (GD-ODS, manufactured by Rigaku, GDA750), an output of 30 W is applied to the glass under an argon atmosphere (Ar pressure: 3 hPa) using the sample as a cathode. The GDS spectrum of Al in the depth direction of the coating film, the GDS spectrum of Si, and the GDS spectrum of Fe were measured. The measurement area was 4 mm ⁇ , the measurement time was 100 seconds, and the measurement interval was 0.02 seconds.
- GD-ODS high-frequency glow emission spectroscope
- the obtained GDS spectrum was smoothed by the simple moving average method.
- the time T Al p and F (T Al p ) were determined using the obtained GDS spectrum of Al.
- determine the time T Si p using GDS spectra of Al, was obtained emission intensity F of Al at time T Si p (T Si p) .
- the measurement start time was Ts.
- the resulting time Ts, the time T Al p, the emission intensity F (T Al p), a time T Si p, and, with the emission intensity F (T Si p) was determined F1 and F2.
- the obtained F1 value and F2 value are shown in Tables 4 to 6.
- the time T Fe 60 and the time T Fe 90 were also determined using the obtained GDS spectrum of Fe.
- iron loss W 17/50 (W / kg) was measured when the frequency was 50 Hz and the maximum magnetic flux density was 1.7 T in accordance with JIS C2556 (2011). The measurement results are shown in Tables 4 to 6. When the iron loss W 17/50 was less than 0.85 W / kg, it was judged to be acceptable.
- the adhesion of the glass film was evaluated as follows according to the obtained residual rate of the glass film. VeryGood (excellent): 90% or more residual coating area ratio Good (slightly excellent): 85% or more and less than 90% residual coating area Fair (effective): 80% or more and less than 85% residual coating area NoGood ( No effect): The coating residual area ratio is less than 80%.
- the evaluation results are shown in Tables 4 to 6. When the residual ratio of the glass film was Very Good, Good, and Fair, it was judged to be acceptable.
- test numbers 18 to 25 and 39 to 50 have a lower F1 than test numbers 1 to 17, 26 to 38, and are within the range of 0.05 to 0.30. there were.
- the evaluations of the glass film adhesion evaluation tests of test numbers 18 to 25 and 39 to 50 were all G or VG, which were better than the evaluation results (F) of test numbers 1 to 17, 26 to 38. It was.
- the F1 of the test numbers 22 to 25 and 44 to 50 is in the range of 0.05 to 0.12
- the F1 of the test numbers 18 to 21 and 39 to 43. was in the range of 0.13 to 0.30.
- the evaluations of the glass film adhesion evaluation tests of test numbers 22 to 25 and 44 to 50 were all VG, which were better than the evaluation results (G) of test numbers 18 to 21, 39 to 43.
- test number 53 the high-temperature annealing temperature T2 was too low in the high-temperature annealing step of the finish annealing step. Therefore, although F2 satisfies the equation (2), F1 exceeds the upper limit of the equation (1). As a result, the adhesion of the glass film to the base steel sheet was No Good, and the adhesion of the glass film to the base steel sheet was low.
- test number 54 the high-temperature annealing temperature T2 was too high in the high-temperature annealing step of the finish annealing step. Therefore, F1 is less than the lower limit of the equation (1). As a result, the iron loss W 17/50 was 0.85 or more, and the magnetic characteristics were low.
- test number 58 the low temperature annealing temperature T1 in the low temperature annealing step was too low. Therefore, F1 exceeded the upper limit of the equation (1), and F2 became less than the lower limit of the equation (2). As a result, the magnetic flux density B8 was less than 1.90 T, the iron loss W 17/50 was 0.85 or more, and the magnetic characteristics were low.
- test number 60 the heating step of the decarburization annealing step was not carried out (the heating conditions of the cold-rolled steel sheet were not controlled). As a result, the iron loss W 17/50 was 0.85 or more, and the magnetic characteristics were low.
- the oxygen potential ( PH2O / PH2 ) was more than 0.1 in the temperature raising step of the decarburization annealing step.
- the magnetic flux density B8 was less than 1.90 T
- the iron loss W 17/50 was 0.85 or more
- the magnetic characteristics were low.
- the oxygen potential ( PH2O / PH2 ) was more than 0.1 in the temperature raising step of the decarburization annealing step.
- the magnetic flux density B8 was less than 1.90 T
- the iron loss W 17/50 was 0.85 or more
- the magnetic characteristics were low.
- the oxygen potential ( PH2O / PH2 ) in the temperature raising step of the decarburization annealing step is more than 0.1
- the low temperature annealing temperature T1 in the low temperature annealing step is too low
- the holding in the high temperature annealing step was too short.
- the Al content of the slab was less than 0.01% by mass
- the Al content was less than 0.005% by mass.
- the magnetic flux density B8 was less than 1.90 T
- the iron loss W 17/50 was 0.85 or more
- the magnetic characteristics were low.
- the oxygen potential ( PH2O / PH2 ) in the temperature raising step of the decarburization annealing step was more than 0.1, the low temperature annealing temperature T1 in the low temperature annealing step was too low, and the holding in the high temperature annealing step. Time t2 was too short.
- the Al content of the slab was less than 0.01% by mass, the average chemical composition of the base steel sheet and the glass coating of the grain-oriented electrical steel sheet was determined to be insol. The Al content was less than 0.005% by mass.
- the magnetic flux density B8 was less than 1.90 T, the iron loss W 17/50 was 0.85 or more, and the magnetic characteristics were low.
- test number 65 the oxygen potential ( PH2O / PH2 ) was more than 0.1 in the temperature raising step of the decarburization annealing step. As a result, the iron loss W 17/50 was 0.85 or more, and the magnetic characteristics were low.
- the low temperature annealing temperature T1 in the low temperature annealing step was too low.
- the magnetic flux density B8 was less than 1.90 T
- the iron loss W 17/50 was 0.85 or more
- the magnetic characteristics were low.
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Abstract
Description
本願は、2019年9月19日に、日本に出願された特願2019-170881号に基づき優先権を主張し、その内容をここに援用する。
(1)本発明の一態様にかかる方向性電磁鋼板は、
母材鋼板と、
前記母材鋼板上に配されたグラス被膜と、
前記グラス被膜上に配された張力付与絶縁被膜と、を備え、
前記母材鋼板及び前記グラス被膜の平均化学組成が、質量%で、
C:0.010%以下、
Si:2.5~4.0%、
Mn:0.01~1.00%、
N:0.010%以下、
sol.Al:0.010%以下、
insol.Al:0.005~0.030%、
Mg:0.05~0.20%、
O:0.05~0.40%、
Ti:0~0.020%、
S:0.010%以下、
P:0.030%以下、
Sn:0~0.50%、
Cr:0~0.50%、
Cu:0~0.50%、
Bi:0~0.0100%、
Se:0~0.020%、
Sb:0~0.50%、及び、
残部がFe及び不純物からなり、
前記グラス被膜の表面から深さ方向にグロー放電発光分析を実施して求めたAl及びSiのグロー発光分光スペクトルに関して、
前記グラス被膜の表面を測定開始時刻Tsとし、
Alが最大発光強度となる時刻をTAl pと定義し、
前記TAl pでのAlの発光強度をF(TAl p)と定義し、
Siが最大発光強度となる時刻をTSi pと定義し、
前記TSi pでのAlの発光強度をF(TSi p)と定義したとき、
前記Tsと、前記TAl pと、前記F(TAl p)と、前記TSi pと、前記F(TSi p)とが、
0.05≦F(TSi p)/F(TAl p)≦0.50、及び、
2.0≦(TAl p-Ts)/(TSi p-Ts)≦5.0
を満たす。
(2)上記(1)に記載の方向性電磁鋼板では、前記母材鋼板の板厚が、0.17mm以上0.22mm未満であってもよい。
(3)上記(1)または(2)に記載の方向性電磁鋼板では、
前記平均化学組成として、質量%で、
Cr:0.01~0.50%、
Sn:0.01~0.50%、
Cu:0.01~0.50%、
Bi:0.0010~0.0100%、
Se:0.001~0.020%、及び、
Sb:0.01~0.50%、
からなる群から選択される少なくとも1元素を含有してもよい。
(4)上記(1)~(3)の何れか1つに記載の方向性電磁鋼板では、
前記グラス被膜の表面から深さ方向にグロー放電発光分析を実施して求めたAl及びFeのグロー発光分光スペクトルに関して、
Alが最大発光強度となる時刻をTAl pと定義し、
Fe発光強度がFe発光強度の飽和値に対して60%となる時刻をTFe 60と定義し、
Fe発光強度がFe発光強度の飽和値に対して90%となる時刻をTFe 90と定義したとき、
前記TAl pと、前記TFe 60と、前記TFe 90とが、
TFe 60≦TAl p≦TFe 90
を満たしてもよい。
(A)焼鈍分離剤を調整することにより、グラス被膜の密着性を高める。
(B)仕上げ焼鈍前の母材鋼板の表層に形成されるSiO2の形態を制御することにより、グラス被膜の密着性を高める。具体的には、脱炭焼鈍工程を工夫することによりSiO2の形態を制御して、グラス被膜の密着性を高める。
0.05≦F(TSi p)/F(TAl p)≦0.50 ・・・(式1)
2.0≦(TAl p-Ts)/(TSi p-Ts)≦5.0 ・・・(式2)
母材鋼板と、
母材鋼板上に配されたグラス被膜と、
グラス被膜上に配された張力付与絶縁被膜と、を備え、
母材鋼板及びグラス被膜の平均化学組成が、質量%で、
C:0.010%以下、
Si:2.5~4.0%、
Mn:0.01~1.00%、
N:0.010%以下、
sol.Al:0.010%以下、
insol.Al:0.005~0.030%、
Mg:0.05~0.20%、
O:0.05~0.40%、
Ti:0~0.020%、
S:0.010%以下、
P:0.030%以下、
Sn:0~0.50%、
Cr:0~0.50%、
Cu:0~0.50%、
Bi:0~0.0100%、
Se:0~0.020%、
Sb:0~0.50%、及び、
残部がFe及び不純物からなり、
上記グラス被膜の表面から深さ方向にグロー放電発光分析を実施して求めたAl及びSiのグロー発光分光スペクトルに関して、
グラス被膜の表面を測定開始時刻Tsとし、
Alが最大発光強度となる時刻をTAl pと定義し、
TAl pでのAlの発光強度をF(TAl p)と定義し、
Siが最大発光強度となる時刻をTSi pと定義し、
TSi pでのAlの発光強度をF(TSi p)と定義したとき、
上記Tsと、上記TAl pと、上記F(TAl p)と、上記TSi pと、上記F(TSi p)とが、
0.05≦F(TSi p)/F(TAl p)≦0.50、及び、
2.0≦(TAl p-Ts)/(TSi p-Ts)≦5.0
を満たす。
Cr:0.01~0.50%、
Sn:0.01~0.50%、
Cu:0.01~0.50%、
Bi:0.0010~0.0100%、
Se:0.001~0.020%、及び、
Sb:0.01~0.50%、
からなる群から選択される少なくとも1元素を含有してもよい。
上記グラス被膜の表面から深さ方向にグロー放電発光分析を実施して求めたAl及びFeのグロー発光分光スペクトルに関して、
Alが最大発光強度となる時刻をTAl pと定義し、
Fe発光強度がFe発光強度の飽和値に対して60%となる時刻をTFe 60と定義し、
Fe発光強度がFe発光強度の飽和値に対して90%となる時刻をTFe 90と定義したとき、
上記TAl pと、上記TFe 60と、上記TFe 90とが、
TFe 60≦TAl p≦TFe 90
を満たしてもよい。
図1は、本実施形態に係る方向性電磁鋼板を示す斜視図である。図1に示すように、本実施形態に係る方向性電磁鋼板1は、母材鋼板10と、グラス被膜11と、張力付与絶縁被膜12とを備える。グラス被膜11は、母材鋼板10上に配されている。図1では、グラス被膜11は、母材鋼板10の表面に直接接触して、母材鋼板10の表面上に配されている。張力付与絶縁被膜12は、グラス被膜11上に配されている。図1では、張力付与絶縁被膜12は、グラス被膜11の表面に直接接触して、グラス被膜11の表面上に配されている。
張力付与絶縁被膜12を除去した後の、グラス被膜11を備えた母材鋼板10の化学組成(母材鋼板10及びグラス被膜11の平均化学組成)は、周知の成分分析法により求めることができる。成分分析法は、例えば、次のとおりである。
炭素(C)は、選択元素である。Cは、磁束密度を改善するため、スラブに必須の元素である。しかしながら、Cは方向性電磁鋼板の製造工程にて鋼板から抜けていく。上記の平均化学組成としてCが0.010%を超えて残存すれば、他の元素含有量が本実施形態の範囲内であっても、Cはセメンタイト(Fe3C)を形成して、方向性電磁鋼板の鉄損を劣化する。したがって、C含有量は0.010%以下である。C含有量の好ましい上限は0.006%であり、さらに好ましくは0.003%である。C含有量はなるべく低い方が好ましい。したがって、C含有量は0%であってもよい。しかしながら、C含有量の過度の低減は、製造コストを引き上げる。したがって、C含有量の好ましい下限は、0%超であり、さらに好ましくは0.001%である。
シリコン(Si)は、基本元素である。Siは、鋼材の電気抵抗(比抵抗)を高めて方向性電磁鋼板の鉄損を低減する。Si含有量が2.5%未満であれば、他の元素含有量が本実施形態の範囲内であっても、仕上げ焼鈍工程にて鋼が相変態して、二次再結晶が十分に進行しない。その結果、上記効果が十分に得られない。一方、Si含有量が4.0%を超えれば、他の元素含有量が本実施形態の範囲内であっても、鋼板が脆化して、製造工程における通板性が顕著に低下する。したがって、Si含有量は2.5~4.0%である。Si含有量の好ましい下限は2.8%であり、さらに好ましくは3.0%であり、さらに好ましくは3.2%である。Si含有量の好ましい上限は3.7%であり、さらに好ましくは3.6%であり、さらに好ましくは3.5%である。
マンガン(Mn)は、基本元素である。Mnは、方向性電磁鋼板の比抵抗を高めて鉄損を低減する。Mnはさらに、熱間加工性を高めて、熱間圧延における割れの発生を抑制する。Mnはさらに、S及び/又はSeと結合して微細なMnS及び/又は微細MnSeを形成する。微細MnS及び微細MnSeは、インヒビターとして活用される微細AlNの析出核となる。そのため、微細MnS及び微細MnSeの析出量が多ければ、十分な量の微細AlNが得られる。Mn含有量が0.01%未満であれば、他の元素含有量が本実施形態の範囲内であっても、十分な量の微細MnS及び微細MnSeが析出しない。一方、Mn含有量が1.00%を超えれば、他の元素含有量が本実施形態の範囲内であっても、方向性電磁鋼板の磁束密度が低下し、鉄損も劣化する。したがって、Mn含有量は0.01~1.00%である。Mn含有量の好ましい下限は0.02%であり、さらに好ましくは0.03%であり、さらに好ましくは0.05%である。Mn含有量の好ましい上限は0.70%であり、さらに好ましくは0.50%であり、さらに好ましくは0.30%であり、さらに好ましくは0.10%である。
窒素(N)は、選択元素である。Nは、方向性電磁鋼板の製造工程中に、Alと結合してAlNを形成し、インヒビターとして機能する。したがって、Nは、方向性電磁鋼板の素材であるスラブには必須の元素である。しかしながら、Nは、方向性電磁鋼板の製造工程にて、鋼板から抜けていく。上記の平均化学組成としてN含有量が0.010%を超えれば、他の元素含有量が本実施形態の範囲内であっても、鋼板にブリスタ(空孔)が多数生成しやすくなる。ブリスタは、被膜欠陥の原因となり、方向性電磁鋼板の絶縁性を低下する。したがって、N含有量は0.010%以下である。N含有量の好ましい上限は0.008%であり、さらに好ましくは0.006%であり、さらに好ましくは0.004%である。N含有量は0%であってもよい。しかしながら、N含有量の過剰な低減は困難な場合がある。したがって、N含有量の好ましい下限は0.001%であり、さらに好ましくは0.002%である。
酸可溶性アルミニウム(sol.Al)は、選択元素である。sol.Alは、方向性電磁鋼板の製造工程中に、Nと結合してAlNを形成し、インヒビターとして機能する。しかしながら、sol.Al含有量が0.010%を超えれば、他の元素含有量が本実施形態の範囲内であっても、Al系介在物が鋼板中に残存する。この場合、方向性電磁鋼板の鉄損が劣化する。したがって、sol.Al含有量は0.010%以下である。sol.Al含有量の好ましい上限は0.008%であり、さらに好ましくは0.006%である。sol.Al含有量は0%であってもよい。しかしながら、Al含有量の過剰な低減は困難な場合もある。したがって、Al含有量の好ましい下限は0.001%であり、さらに好ましくは0.002%である。なお、本実施形態では、sol.Alは酸可溶Alを意味する。したがって、sol.Al含有量は、酸可溶Alの含有量である。
酸不可溶性アルミニウム(insol.Al)は、基本元素である。insol.Alは、主として、後述の仕上げ焼鈍工程にて形成されるスピネル(MgAl2O4)に由来する。insol.Al含有量が0.005%未満であれば、他の元素含有量が本実施形態の範囲内であっても、グラス被膜11に十分なスピネルが存在しないため、グラス被膜11の密着性が低い。一方、insol.Al含有量が0.030%を超えれば、他の元素含有量が本実施形態の範囲内であっても、スピネルが過剰に生成してしまう。この場合、スピネルはグラス被膜11と母材鋼板10との界面だけでなく、グラス被膜11内部にも過剰に存在してしまう。グラス被膜11の内部にスピネルが過剰に存在すれば、グラス被膜11のひび割れ(クラック)の発生源となり、グラス被膜11の密着性が低下する。したがって、insol.Al含有量は0.005~0.030%である。insol.Al含有量の好ましい下限は0.006%であり、さらに好ましくは0.007%であり、さらに好ましくは0.010%である。insol.Al含有量の好ましい上限は0.027%であり、さらに好ましくは0.025%であり、さらに好ましくは0.020%である。
マグネシウム(Mg)は、グラス被膜の構成元素(基本元素)である。そのため、Mg含有量は、0.05~0.20%であればよい。Mg含有量の好ましい上限は0.18%であり、さらに好ましくは0.16%である。Mg含有量の好ましい下限は0.08%であり、さらに好ましくは0.10%である。
酸素(O)は、グラス被膜の構成元素(基本元素)である。そのため、O含有量は、0.05~0.40%であればよい。O含有量の好ましい上限は0.30%であり、さらに好ましくは0.25%である。O含有量の好ましい下限は0.10%であり、さらに好ましくは0.15%である。
チタン(Ti)は、選択元素である。Tiは、グラス被膜の生成を促進させ、被膜密着性を好ましく確保する。そのため、Ti含有量は、0~0.020%であればよい。Ti含有量の好ましい上限は0.015%であり、さらに好ましくは0.010%である。Ti含有量は0%であってもよいが、Ti含有量の好ましい下限は0.001%であり、さらに好ましくは0.003%であり、さらに好ましくは0.005%である。
硫黄(S)は、選択元素である。Sは、製造工程中に、Mnと結合して、インヒビターである微細MnSを形成する。そのため、Sはスラブに必須の元素である。しかしながら、Sは方向性電磁鋼板の製造工程にて鋼板から抜けていく。上記の平均化学組成としてS含有量が0.010%を超えれば、他の元素含有量が本実施形態の範囲内であっても、母材鋼板10中にMnSが残存するため、鉄損が劣化する。したがって、S含有量は0.010%以下である。S含有量の好ましい上限は0.008%であり、さらに好ましくは0.006%であり、さらに好ましくは0.004%である。S含有量は0%であってもよい。しかしながら、S含有量の過剰な低減は困難な場合がある。したがって、S含有量の好ましい下限は0.001%であり、さらに好ましくは0.002%である。
燐(P)は、選択元素である。Pは、圧延時における鋼板の加工性を低下する。P含有量が0.030%を超えれば、他の元素含有量が本実施形態の範囲内であっても、鋼板の加工性が顕著に低下する。したがって、P含有量は0.030%以下である。P含有量の好ましい上限は0.020%であり、さらに好ましくは0.010%である。P含有量は0%であってもよい。しかしながら、P含有量の過剰な低減は困難な場合がある。したがって、P含有量の好ましい下限は0.001%である。なお、Pは集合組織を改善し、鋼板の磁気特性を改善する。この効果を有効に発揮するためのP含有量の好ましい下限は0.002%であり、さらに好ましくは0.005%である。
クロム(Cr)は、選択元素である。つまり、Cr含有量は0%であってもよい。Crが含有される場合、CrはSn及びCuと同様に、グラス被膜11の母材鋼板10への密着性を高める。Crはさらに、二次再結晶にて、ゴス方位結晶粒の集積度を高める。Crが少しでも含有されれば、上記効果がある程度得られる。しかしながら、Cr含有量が0.50%を超えれば、他の元素含有量が本実施形態の範囲内であっても、Cr酸化物が生成して、方向性電磁鋼板1の磁気特性を低下する。したがって、Cr含有量は0~0.50%である。Cr含有量の好ましい上限は0.40%であり、さらに好ましくは0.30%であり、さらに好ましくは0.20%であり、さらに好ましくは0.10%である。Cr含有量の好ましい下限は0%超であり、さらに好ましくは0.01%であり、さらに好ましくは0.03%であり、さらに好ましくは0.05%である。
スズ(Sn)は、選択元素である。つまり、Sn含有量は0%であってもよい。Snが含有される場合、SnはCr及びCuと同様に、グラス被膜11の母材鋼板10への密着性を高める。Snが少しでも含有されれば、上記効果がある程度得られる。しかしながら、Sn含有量が0.50%を超えれば、他の元素含有量が本実施形態の範囲内であっても、方向性電磁鋼板1の製造工程中に、二次再結晶が不安定となり、その結果、方向性電磁鋼板1の磁気特性が劣化する。したがって、Sn含有量は0~0.50%である。Sn含有量の好ましい下限は0%超であり、さらに好ましくは0.01%であり、さらに好ましくは0.02%であり、さらに好ましくは0.03%である。
銅(Cu)は、選択元素である。つまり、Cu含有量は0%であってもよい。Cuが含有される場合、CuはCr及びSnと同様に、グラス被膜11の母材鋼板10への密着性を高める。Cuが少しでも含有されれば、上記効果がある程度得られる。しかしながら、Cu含有量が0.50%を超えれば、他の元素含有量が本実施形態の範囲内であっても、方向性電磁鋼板1の製造工程中における熱間加工性が低下する。したがって、Cu含有量は0~0.50%である。Cu含有量の好ましい下限は0%超であり、さらに好ましくは0.01%であり、さらに好ましくは0.03%であり、さらに好ましくは0.05%である。Cu含有量の好ましい上限は0.40%であり、さらに好ましくは0.30%であり、さらに好ましくは0.20%であり、さらに好ましくは0.10%である。
Bi(ビスマス)は、選択元素である。つまり、Bi含有量は0%であってもよい。Biが含有される場合、BiはSe及びSbと同様にインヒビターとして機能して、方向性電磁鋼板1の製造時に二次再結晶を安定化する。その結果、方向性電磁鋼板1の磁気特性が高まる。Biが少しでも含有されれば、上記効果がある程度得られる。しかしながら、Bi含有量が0.0100%を超えれば、他の元素含有量が本実施形態の範囲内であっても、グラス被膜11の母材鋼板10に対する密着性が低下する。そのため、Biの含有量は、0~0.0100%である。Bi含有量の好ましい下限は0%超であり、さらに好ましくは0.0010%であり、さらに好ましくは0.0020%である。Bi含有量の好ましい上限は0.0090%であり、さらに好ましくは0.0070%であり、さらに好ましくは0.0050%である。
セレン(Se)は、選択元素である。つまり、Se含有量は0%であってもよい。Seが含有される場合、SeはBi及びSbと同様にインヒビターとして機能して、方向性電磁鋼板1の製造時に二次再結晶を安定化する。その結果、方向性電磁鋼板1の磁気特性が高まる。Seが少しでも含有されれば、上記効果がある程度得られる。しかしながら、Se含有量が0.020%を超えれば、他の元素含有量が本実施形態の範囲内であっても、グラス被膜11の母材鋼板10に対する密着性が低下する。したがって、Se含有量は0~0.020%である。Se含有量の好ましい下限は0%超であり、さらに好ましくは0.001%であり、さらに好ましくは0.003%であり、さらに好ましくは0.005%である。Se含有量の好ましい上限は0.015%であり、さらに好ましくは0.010%であり、さらに好ましくは0.008%である。
アンチモン(Sb)は、選択元素である。つまり、Sb含有量は0%であってもよい。Sbが含有される場合、SbはBi及びSeと同様にインヒビターとして機能して、方向性電磁鋼板1の製造時に二次再結晶を安定化する。その結果、方向性電磁鋼板1の磁気特性が高まる。Sbが少しでも含有されれば、上記効果がある程度得られる。しかしながら、Sb含有量が0.50%を超えれば、他の元素含有量が本実施形態の範囲内であっても、グラス被膜11の母材鋼板10に対する密着性が低下する。したがって、Sb含有量は0~0.50%である。Sb含有量の好ましい下限は0%超であり、さらに好ましくは0.01%であり、さらに好ましくは0.03%であり、さらに好ましくは0.05%である。Sb含有量の好ましい上限は0.40%であり、さらに好ましくは0.30%であり、さらに好ましくは0.20%であり、さらに好ましくは0.10%である。
グラス被膜11は、母材鋼板10上に形成されている。グラス被膜11は、フォルステライト(Mg2SiO4)を主体とする。本実施形態に係る方向性電磁鋼板では、グラス被膜11の存在を確認するために、上記の方法にて張力付与絶縁被膜12を除去した表面に対してX線回折を行い、得られたX線回折スペクトルをPDF(Powder Diffraction File)と照合すればよい。例えば、フォルステライト(Mg2SiO4)の同定には、JCPDS番号:34-189を用いればよい。本実施形態では、上記X線回折スペクトルの主な構成がフォルステライトである場合に、方向性電磁鋼板1がグラス被膜11を有すると判断する。
張力付与絶縁被膜12は、グラス被膜11上に形成されている。張力付与絶縁被膜12は、複数の方向性電磁鋼板1を積層して使用する場合に、互いに積層された方向性電磁鋼板1同士の絶縁を担保するために、方向性電磁鋼板1の最上層に形成される。
本実施形態に係る方向性電磁鋼板1では、グラス被膜11内で母材鋼板10との界面近傍にスピネル(MgAl2O4)が局在化している。具体的には、張力付与絶縁被膜12を除去した後、グラス被膜11の表面から深さ方向にグロー放電発光分析を実施して、Alの発光強度及びSiの発光強度を示すグロー発光分光スペクトル(AlのGDSスペクトル、SiのGDSスペクトル)を求める。グラス被膜の表面を測定開始時刻Tsとし、AlのGDSスペクトルにてAlが最大発光強度となる時刻をTAl pと定義し、時刻TAl pでのAlの発光強度(つまり、Alの最大発光強度)をF(TAl p)と定義し、SiのGDSスペクトルにてSiが最大発光強度となる時刻をTSi pと定義し、時刻TSi pでのAlの発光強度(つまり、Siの最大発光強度の深さ位置でのAlの発光強度)をF(TSi p)と定義する。このとき、Tsと、TAl pと、F(TAl p)と、TSi pと、F(TSi p)とが、式(1)及び式(2)を満たす。
0.05≦F(TSi p)/F(TAl p)≦0.50 ・・・(式1)
2.0≦(TAl p-Ts)/(TSi p-Ts)≦5.0 ・・・(式2)
本実施形態に係る方向性電磁鋼板1では、スピネル(MgAl2O4)がグラス被膜11内でグラス被膜11の厚さ方向に分布し、スピネルの分布がグラス被膜11内の母材鋼板10との界面近傍でピークを示す。すなわち、AlのGDSスペクトルは、グラス被膜11内で母材鋼板10との界面近傍にピークを有する。本実施形態に係る方向性電磁鋼板1では、グラス被膜11と母材鋼板10との界面近傍でAlのGDSスペクトルのピークがシャープであるほど、スピネルがグラス被膜11と母材鋼板10との界面に局在していることになる。
グロー発光分光スペクトルでは、グラス被膜11の表面を測定開始時刻Tsと定義する。
方向性電磁鋼板1の張力付与絶縁被膜12を除去した後、グラス被膜11の表面から深さ方向にグロー放電発光分析を実施し、グラス被膜11の表面を測定開始時刻Tsとして、測定時刻とAlの発光強度との関係を示すAlのグロー発光分光スペクトル(AlのGDSスペクトル)を求める。ここで、測定時刻は、グラス被膜11の表面からの深さに対応する。得られたAlのGDSスペクトルに対して、発光強度の最大値と、その最大値の時刻とを特定する。特定された時刻を時刻TAl pと定義する。つまり、時刻TAl pは、Al濃度(AlのGDS強度)がピークとなる深さ位置(グラス被膜11の表面からの深さ位置)に相当する。
上記したAlのグロー発光分光スペクトル(AlのGDSスペクトル)で、Alの発光強度の最大値、すなわち、時刻TAl pにおけるAlの最大発光強度を、F(TAl p)と定義する。
方向性電磁鋼板1の張力付与絶縁被膜12を除去した後、グラス被膜11の表面から深さ方向にグロー放電発光分析を実施し、グラス被膜11の表面を測定開始時刻Tsとして、測定時刻とSiの発光強度との関係を示すSiのグロー発光分光スペクトル(SiのGDSスペクトル)を求める。上述のとおり、測定時刻は、グラス被膜11の表面からの深さに対応する。得られたSiのGDSスペクトルに対して、発光強度の最大値と、その最大値の時刻とを特定する。特定された時刻を時刻TSi pと定義する。つまり、時刻TSi pは、Si濃度(SiのGDS強度)がピークとなる深さ位置(グラス被膜11の表面からの深さ位置)に相当する。
上記したAlのグロー発光分光スペクトル(AlのGDSスペクトル)で、時刻TSi pに対応するAlの発光強度をF(TSi p)と定義する。
F2=(TAl p-Ts)/(TSi p-Ts)と定義する。図3に示すとおり、F2は、Al濃度のピーク位置と、Si濃度のピーク位置(つまり、グラス被膜11の深さ方向の中心位置)との関係を示しており、グラス被膜11中でのスピネルの局在位置を示す指標である。
上述のF1値及びF2値は次の方法で求めることができる。始めに、方向性電磁鋼板1の板幅方向TDの中央部分から、圧延方向RDが30mm、板幅方向TDが40mm、厚さが方向性電磁鋼板1の板厚、のサンプルを採取する。採取されたサンプルから、張力付与絶縁被膜12を除去する。具体的には、方向性電磁鋼板1を、NaOH:30~50質量%及びH2O:50~70質量%を含有し、80~90℃の水酸化ナトリウム水溶液に、7~10分間浸漬する。浸漬後の鋼板(張力付与絶縁被膜12が除去された、グラス被膜11を備える母材鋼板10)を水洗する。水洗後、温風のブロアーで1分間弱、乾燥させる。以上の処理により、図4に示すとおり、母材鋼板10とグラス被膜11とを備え、張力付与絶縁被膜12が除去されたサンプルを準備する。
Alが最大発光強度となる時刻をTAl pと定義し、
Fe発光強度がFe発光強度の飽和値に対して60%となる時刻をTFe 60と定義し、
Fe発光強度がFe発光強度の飽和値に対して90%となる時刻をTFe 90と定義したとき、
上記TAl pと、上記TFe 60と、上記TFe 90とが、
TFe 60≦TAl p≦TFe 90 ・・・(式3)
を満たせばよい。
以下、本実施形態に係る方向性電磁鋼板1の製造方法の一例を説明する。なお、本実施形態に係る方向性電磁鋼板1は、上述の構成を有すれば、製造方法は特に限定されない。下記の製造方法は、本実施形態に係る方向性電磁鋼板1を製造するための一つの例であり、本実施形態に係る方向性電磁鋼板1の製造方法の好適な例である。
図5は、本実施形態に係る方向性電磁鋼板1の製造方法のフロー図である。図5に示すように、本製造方法は、スラブに対して熱間圧延を実施する熱間圧延工程(S1)と、熱間圧延後の鋼板(熱延鋼板)に対して焼鈍処理を実施する熱延板焼鈍工程(S2)と、熱延板焼鈍工程後の鋼板に対して1又は2回以上の冷間圧延(S30)を実施する冷間圧延工程(S3)と、冷間圧延工程後の鋼板(冷延鋼板)に対して脱炭焼鈍を実施する脱炭焼鈍工程(S4)と、脱炭焼鈍工程後の鋼板の表面に焼鈍分離剤を塗布する焼鈍分離剤塗布工程(S5)と、焼鈍分離剤が塗布された鋼板に対して仕上げ焼鈍を実施して、グラス被膜を形成する仕上げ焼鈍工程(S6)と、仕上げ焼鈍工程後の鋼板に対して、張力付与絶縁被膜を形成する絶縁被膜形成工程(S7)とを含む。以下、各工程S1~S7について説明する。
熱間圧延工程(S1)では、準備されたスラブに対して熱間圧延を実施して熱延鋼板を製造する。スラブの化学組成は、方向性電磁鋼板1の母材鋼板10及びグラス被膜11の平均化学組成が上述の化学組成となるように調整される。ただ、スラブのAl含有量は0.01質量%以上にする。スラブのAl含有量が0.01質量%未満では、グラス被膜11にスピネルが十分に生成しない。また、スラブは周知の方法で製造する。たとえば、溶鋼を製造(溶製)する。溶鋼を用いて、連続鋳造法により、スラブを製造する。
熱延板焼鈍工程(S2)は任意の工程であり、実施しなくてもよい。実施する場合、熱延板焼鈍工程(S2)では、熱間圧延工程(S1)にて製造された熱延鋼板に対して焼鈍処理を実施して、熱延焼鈍鋼板とする。熱延板焼鈍工程を実施することにより、鋼板組織に再結晶が生じ、磁気特性が高まる。
冷間圧延工程(S3)では、製造された鋼板(熱延鋼板または熱延焼鈍鋼板)に対して、1又は複数回の冷間圧延(S30)を実施する。冷間圧延(S30)は、冷間圧延機を用いて実施する。冷間圧延機は、たとえば、一列に配列された複数の冷間圧延スタンドを備えるタンデム式の圧延機であって、各冷間圧延スタンドは、複数の冷間圧延ロールを含む。冷間圧延機は、1台のリバース式の冷間圧延スタンドであってもよい。
冷延率(%)=[(最初の冷間圧延開始前の鋼板の板厚-最後の冷間圧延後の冷延鋼板の板厚)/最初の冷間圧延開始前の鋼板の板厚]×100
脱炭焼鈍工程(S4)では、冷間圧延工程(S3)後の鋼板(冷延鋼板)に対して、脱炭焼鈍を実施して一次再結晶を発現させる。
昇温工程では、初めに、冷間圧延工程(S3)後の鋼板を熱処理炉に装入する。本実施形態における脱炭焼鈍用の熱処理炉では、たとえば、高周波誘導加熱や通電加熱により、冷延鋼板を脱炭焼鈍温度まで制御しながら昇温する。なお、昇温工程中の雰囲気は、酸素ポテンシャル(PH2O/PH2)が0.1以下の乾燥窒素雰囲気または乾燥窒素水素混合雰囲気である。昇温工程での酸素ポテンシャルが0.1超であると、Fe系酸化物が核生成しやすい。昇温工程で核生成したFe酸化物は脱炭焼鈍中に成長・発達する。これらが仕上げ焼鈍中に存在すると、フォルステライト(Mg2SiO4)の発達を阻害する。原因は不明だが、Fe酸化物はSiO2とMgOの固相反応を抑制する作用がある。その結果、Mg2SiO4は薄膜化し、グラス被膜11内でスピネルが母材鋼板10との界面近傍に局在化しにくくなる。具体的にはMg2SiO4中にスピネル(MgAl2O4)が存在するようになる。
脱炭焼鈍工程(S4)における脱炭工程(S42)では、昇温工程(S41)後の鋼板を脱炭焼鈍温度Taで保持して、脱炭焼鈍を実施する。これにより、鋼板に一次再結晶を発現させる。脱炭工程中の雰囲気は、周知の雰囲気で足り、たとえば、水素及び窒素を含有する湿潤窒素水素混合雰囲気である。脱炭焼鈍を実施することにより、鋼板中の炭素が鋼板から除去され、一次再結晶が発現する。脱炭工程での製造条件は次のとおりである。
脱炭焼鈍温度Taは、上述のとおり、脱炭焼鈍を実施する熱処理炉の炉温に相当し、脱炭焼鈍中の鋼板の温度に相当する。脱炭焼鈍温度Taが800℃未満であれば、一次再結晶発現後の鋼板の結晶粒が小さすぎる。この場合、仕上げ焼鈍工程(S6)にて、二次再結晶が十分に発現しない。一方、脱炭焼鈍温度Taが950℃を超えれば、一次再結晶発現後の鋼板の結晶粒が大きすぎる。この場合も、仕上げ焼鈍工程(S6)にて、二次再結晶が十分に発現しない。脱炭焼鈍温度Taが800~950℃であれば、一次再結晶発現後の鋼板の結晶粒が適切なサイズとなり、仕上げ焼鈍工程(S6)にて、二次再結晶が十分に発現する。
冷却工程(S43)では、脱炭工程(S42)後の鋼板を周知の方法で常温まで冷却する。冷却方法は放冷であってもよいし、水冷であってもよい。好ましくは、脱炭工程後の鋼板を放冷する。以上の工程により脱炭焼鈍工程(S4)では、鋼板に対して脱炭焼鈍処理を実施する。
脱炭焼鈍工程(S4)後の鋼板(脱炭焼鈍鋼板)に対して、焼鈍分離剤塗布工程(S5)を実施する。焼鈍分離剤塗布工程(S5)では、鋼板表面に焼鈍分離剤を塗布する。具体的には、鋼板表面に焼鈍分離剤を含有する水性スラリーを塗布する。水性スラリーは、焼鈍分離剤に水を加えて攪拌して作製する。焼鈍分離剤は、酸化マグネシウム(MgO)を含有する。好ましくは、MgOは焼鈍分離剤の主成分である。ここで、「主成分」とは、焼鈍分離剤中のMgO含有量が、質量%で80.0%以上であることを意味する。焼鈍分離剤は、MgO以外に、周知の添加剤を含有してもよい。例えば、焼鈍分離剤は、Ti化合物を含有してもよい。
焼鈍分離剤塗布工程(S5)後の鋼板に対して、仕上げ焼鈍工程(S6)を実施して、二次再結晶を発現させる。仕上げ焼鈍工程ではさらに、二段階の焼鈍工程(低温焼鈍工程(S61)及び高温焼鈍工程(S62))を実施して、フォルステライトを主体とするグラス被膜11を形成し、かつ、グラス被膜11中にて、母材鋼板10の界面近傍にスピネルを適切な量で局在化させる。二段階の焼鈍工程(低温焼鈍工程(S61)及び高温焼鈍工程(S62))は、熱処理炉を用いて実施する。以下、低温焼鈍工程(S61)及び高温焼鈍工程(S62)について説明する。
低温焼鈍工程(S61)は、グラス被膜11を生成するための工程である。低温焼鈍工程(S61)では、始めに、コイル状の鋼板を熱処理炉に挿入して、鋼板を低温焼鈍温度T1まで昇温する。低温焼鈍温度T1で、保持時間t1保持する。なお、低温焼鈍工程(S61)における炉内雰囲気は、水素及び窒素の混合雰囲気であればよい。
低温焼鈍温度T1:910~1000℃
910~1000℃での保持時間t1:50~120時間
910~1000℃は、グラス被膜11の主成分であるフォルステライト(Mg2SiO4)が生成する温度域である。
低温焼鈍温度T1が適切である場合、つまり、低温焼鈍温度T1が910~1000℃である場合、低温焼鈍温度T1での保持時間t1が50時間未満であれば、フォルステライトの生成が不十分となり、グラス被膜11が薄膜化してしまう。そのため、F1は式(1)を満たすものの、F2が式(2)の上限を超えてしまう。その結果、絶縁性が低下してしまう。
高温焼鈍工程(S62)は、低温焼鈍工程(S61)で生成したグラス被膜11中にスピネルを生成して、母材鋼板10の界面近傍にスピネルを局在化させるための工程である。具体的には、低温焼鈍工程(S61)が終了した後、鋼板をさらに高温焼鈍温度T2まで昇温する。昇温速度は特に限定されない。その後、次に示す高温焼鈍温度T2で、保持時間t2保持する。なお、高温焼鈍工程は、低温焼鈍工程と同じ熱処理炉で実施してもよいし、異なる熱処理炉で実施してもよい。高温焼鈍工程における炉内雰囲気は、窒素雰囲気であればよい。
高温焼鈍温度T2:1100~1300℃
高温焼鈍温度T2での保持時間t2:20~80時間
1100~1300℃は、スピネルの生成温度域である。低温焼鈍工程によって、グラス被膜11が十分に形成されている。そのため、高温焼鈍工程にて、1100~1300℃の温度域で保持すれば、母材鋼板10に含まれるAlがグラス被膜11と母材鋼板10との界面近傍に移動して、フォルステライトと反応してスピネルを形成する。これにより、高温焼鈍工程中、グラス被膜11のうち、母材鋼板10との界面近傍に、スピネルが形成され、界面近傍にスピネルが局在化する。
1100~1300℃での保持時間t2が20時間未満であれば、スピネルが十分に生成しない。この場合、F2は式(2)を満たすものの、F1が式(1)の上限を超える。
本実施形態に係る方向性電磁鋼板1の製造方法ではさらに、仕上げ焼鈍工程(S6)後に、絶縁被膜形成工程(S7)を実施する。絶縁被膜形成工程(S7)では、仕上げ焼鈍工程(S6)の冷却後の方向性電磁鋼板1の表面(グラス被膜11上)に、コロイド状シリカ及びリン酸塩を主体とする絶縁コーティング剤を塗布した後、焼付けを実施する。これにより、グラス被膜上に、張力付与絶縁被膜12が形成される。
なお、本実施形態に係る方向性電磁鋼板1は、脱炭焼鈍工程(S4)後、焼鈍分離剤塗布工程(S5)前に、窒化処理工程を実施してもよい。窒化処理工程では、脱炭焼鈍工程(S4)後の鋼板に対して、窒化処理を実施して、窒化処理鋼板を製造する。窒化処理工程は周知の条件で実施すれば足りる。好ましい窒化処理条件はたとえば、次のとおりである。
窒化処理炉内の雰囲気(窒化処理雰囲気):水素、窒素及びアンモニア等の窒化能を有するガスを含有する雰囲気。
本実施形態に係る方向性電磁鋼板1はさらに、必要に応じて、仕上げ焼鈍工程(S6)又は絶縁被膜形成工程(S7)後に、磁区細分化処理工程を実施してもよい。磁区細分化処理工程では、方向性電磁鋼板1の表面に、磁区細分化効果のあるレーザ光を照射したり、表面に溝を形成したりする。この場合、さらに磁気特性に優れる方向性電磁鋼板1が製造できる。
基本的な化学組成として、質量%で、C:0.03~0.10%、Si:3.0~3.5%、sol.Al:0.2~0.3%、Mn:0.02~0.90%、N:0.005~0.03%、S:0.005~0.03%、P:0.005~0.03%を含有し、残部がFe及び不純物を有するスラブを製造した。
各試験番号の方向性電磁鋼板のうち、張力付与絶縁被膜を除去した後の、グラス被膜を備えた母材鋼板の化学組成(母材鋼板及びグラス被膜の平均化学組成)を次の方法により分析した。
各試験番号の方向性電磁鋼板の板幅方向TDの中央部分から、圧延方向RDに30mm、板幅方向TDの40mm、厚さが方向性電磁鋼板の板厚、のサンプルを採取した。採取されたサンプルから、張力付与絶縁被膜を除去した。具体的には、方向性電磁鋼板を、NaOH:30~50質量%及びH2O:50~70質量%を含有し、80~90℃の水酸化ナトリウム水溶液に、7~10分間浸漬した。浸漬後の方向性電磁鋼板を水洗し、その後、温風のブロアーで1分間弱、乾燥させた。以上の方法により、母材鋼板とグラス被膜とを備え、張力付与絶縁被膜が除去されたサンプルを作成した。
各試験番号の方向性電磁鋼板の板幅中央位置を含む、幅60mm×長さ300mmのサンプルを採取した。サンプルの長さは、圧延方向に平行であった。採取されたサンプルを用いて、JIS C2556(2011)に準拠して、単板磁気特性試験(SST試験)により、磁束密度B8(T)を求めた。具体的には、サンプルに800A/mの磁場を付与して、磁束密度(T)を求めた。測定結果を表4~表6に示す。なお、磁束密度B8が、1.90T以上である場合を合格と判断した。
各試験番号の方向性電磁鋼板の板幅中央位置から、圧延方向に80mm×板幅方向に30mmのサンプルを採取した。採取したサンプルを、直径20mmの円筒に巻き付けて180°曲げた。その後、曲げたサンプルを元の平坦な状態に戻した。平坦な状態に戻した後、剥離せずに残っているグラス被膜の総面積を求めた。求めたグラス被膜の総面積を用いて、以下の式により、グラス被膜残存率(面積%)を求めた。
グラス被膜残存率(面積%)=剥離せずに残ったグラス被膜の総面積/サンプルの総面積(80mm×30mm)×100
VeryGood(優れる):被膜残存面積率が90%以上
Good(やや優れる):被膜残存面積率が85%以上90%未満
Fair(効果がある):被膜残存面積率が80%以上85%未満
NoGood(効果がない):被膜残存面積率が80%未満
評価結果を表4~表6に示す。なお、グラス被膜残存率が、VeryGood、Good、及びFairである場合を合格と判断した。
表1~表6に示すように、試験番号1~50は、平均化学組成が適切であり、製造条件も適切であった。その結果、磁気特性及びグラス被膜密着性に優れた。また、表には示さないが、試験番号1~50では、GDSスペクトルが、TFe 60≦TAl p≦TFe 90を満たしていた(TSi p≦TAl p≦TFe 90となっていた)。
10 母材鋼板
11 グラス被膜
12 張力付与絶縁被膜
Claims (4)
- 母材鋼板と、
前記母材鋼板上に配されたグラス被膜と、
前記グラス被膜上に配された張力付与絶縁被膜と、を備え、
前記母材鋼板及び前記グラス被膜の平均化学組成が、質量%で、
C:0.010%以下、
Si:2.5~4.0%、
Mn:0.01~1.00%、
N:0.010%以下、
sol.Al:0.010%以下、
insol.Al:0.005~0.030%、
Mg:0.05~0.20%、
O:0.05~0.40%、
Ti:0~0.020%、
S:0.010%以下、
P:0.030%以下、
Sn:0~0.50%、
Cr:0~0.50%、
Cu:0~0.50%、
Bi:0~0.0100%、
Se:0~0.020%、
Sb:0~0.50%、及び、
残部がFe及び不純物からなり、
前記グラス被膜の表面から深さ方向にグロー放電発光分析を実施して求めたAl及びSiのグロー発光分光スペクトルに関して、
前記グラス被膜の表面を測定開始時刻Tsとし、
Alが最大発光強度となる時刻をTAl pと定義し、
前記TAl pでのAlの発光強度をF(TAl p)と定義し、
Siが最大発光強度となる時刻をTSi pと定義し、
前記TSi pでのAlの発光強度をF(TSi p)と定義したとき、
前記Tsと、前記TAl pと、前記F(TAl p)と、前記TSi pと、前記F(TSi p)とが、
0.05≦F(TSi p)/F(TAl p)≦0.50、及び、
2.0≦(TAl p-Ts)/(TSi p-Ts)≦5.0
を満たす、方向性電磁鋼板。 - 前記母材鋼板の板厚が、0.17mm以上0.22mm未満である、請求項1に記載の方向性電磁鋼板。
- 前記平均化学組成として、質量%で、
Cr:0.01~0.50%、
Sn:0.01~0.50%、
Cu:0.01~0.50%、
Bi:0.0010~0.0100%、
Se:0.001~0.020%、及び、
Sb:0.01~0.50%、
からなる群から選択される少なくとも1元素を含有する、請求項1又は請求項2に記載の方向性電磁鋼板。 - 前記グラス被膜の表面から深さ方向にグロー放電発光分析を実施して求めたAl及びFeのグロー発光分光スペクトルに関して、
Alが最大発光強度となる時刻をTAl pと定義し、
Fe発光強度がFe発光強度の飽和値に対して60%となる時刻をTFe 60と定義し、
Fe発光強度がFe発光強度の飽和値に対して90%となる時刻をTFe 90と定義したとき、
前記TAl pと、前記TFe 60と、前記TFe 90とが、
TFe 60≦TAl p≦TFe 90
を満たす、請求項1~3の何れか一項に記載の方向性電磁鋼板。
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JP7352108B2 (ja) | 2023-09-28 |
CN114402087B (zh) | 2023-03-28 |
US11948711B2 (en) | 2024-04-02 |
KR20220054376A (ko) | 2022-05-02 |
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