WO2024150732A1 - Plaque d'acier électromagnétique non orienté - Google Patents

Plaque d'acier électromagnétique non orienté Download PDF

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WO2024150732A1
WO2024150732A1 PCT/JP2024/000133 JP2024000133W WO2024150732A1 WO 2024150732 A1 WO2024150732 A1 WO 2024150732A1 JP 2024000133 W JP2024000133 W JP 2024000133W WO 2024150732 A1 WO2024150732 A1 WO 2024150732A1
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steel sheet
grains
rolling
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PCT/JP2024/000133
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Japanese (ja)
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夏子 杉浦
一郎 田中
鉄州 村川
俊 太田
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日本製鉄株式会社
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Priority to JP2024531670A priority Critical patent/JPWO2024150732A1/ja
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • 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
    • H01F1/14—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
    • H01F1/147—Alloys characterised by their composition
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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

Definitions

  • This disclosure relates to non-oriented electrical steel sheets.
  • Non-oriented electrical steel sheets are used, for example, in the iron cores of motors, and are required to have excellent magnetic properties in the direction parallel to the plate surface, such as low core loss and high magnetic flux density.
  • strain-induced grain growth can suppress the accumulation of the ⁇ 111 ⁇ orientation, which does not have an easy axis of magnetization in the in-plane direction of the sheet, and is therefore effectively used in non-oriented electrical steel sheets.
  • the Goss orientation has better magnetic properties in one direction than the ⁇ 111 ⁇ orientation, but the magnetic properties are hardly improved on average around the circumference. Therefore, conventional methods have the problem of not being able to obtain excellent magnetic properties on average around the circumference.
  • patent documents 11 to 13 disclose technologies for developing ⁇ 100 ⁇ crystal orientation or ⁇ 411 ⁇ crystallization in a component system in which ⁇ phase transformation occurs.
  • a fine-grained ⁇ phase structure is achieved at the time of hot rolling by using a steel composition with a low ⁇ phase transformation temperature and transforming at a low temperature, and the addition of ⁇ -stabilizing elements such as Mn, Cu, and Ni is utilized from the viewpoint of lowering the transformation temperature and delaying recovery recrystallization to promote the accumulation of strain.
  • Mn is known as a segregation element, and if the amount added is increased, it segregates in the center of the thickness of the hot-rolled sheet, causing cracks when the hot-rolled sheet is cold-rolled.
  • the present disclosure aims to provide a non-oriented electrical steel sheet with a chemical composition in which Mn is suppressed and the contents of elements such as Cu and Ni are optimized so that rolling properties are not an issue, and which has small in-plane anisotropy and excellent magnetic properties averaged all around (averaged in all directions).
  • the present inventors have investigated a technique for forming a favorable texture for non-oriented electrical steel sheets by utilizing strain-induced grain growth. In the process, they have focused on the fact that ⁇ 411 ⁇ uvw> orientation (hereinafter, ⁇ 411 ⁇ orientation) crystal grains are as resistant to strain as ⁇ 100 ⁇ uvw> orientation (hereinafter, ⁇ 100 ⁇ orientation).
  • strain-induced grain growth causes the ⁇ 411 ⁇ orientation crystal grains to encroach on the ⁇ 111 ⁇ orientation crystal grains while simultaneously suppressing the development of ⁇ 100 ⁇ orientation crystal grains, thereby producing a non-oriented electrical steel sheet with the ⁇ 411 ⁇ orientation as the main orientation.
  • the magnetic properties are improved on an average around the circumference (average of the rolling direction, width direction, direction at 45 degrees to the rolling direction, and direction at 135 degrees to the rolling direction).
  • the inventors also investigated a method for increasing the number of ⁇ 411 ⁇ oriented crystal grains relative to ⁇ 100 ⁇ oriented crystal grains at a stage before strain-induced grain growth occurs. As a result, they discovered a method in which hot rolling is performed under specific conditions for steel types with low contents of Mn, Ni, Cu, etc., and then cold rolling and annealing are performed, followed by re-cold rolling (skin pass rolling) at a lower reduction ratio, followed by final annealing.
  • a non-oriented electrical steel sheet In mass percent, C: 0.0100% or less, Si: 1.50% to 4.00%, sol. Al: 0.0001% to 1.0%, S: 0.0100% or less, N: 0.0100% or less, Mn: 0.10% or more, One or more selected from Mn, Ni, and Cu: less than 2.50% in total; Mo: 0.0% to less than 2.5% Cr: 0.0% to less than 2.5% Ti: 0.000% to 0.005%, Nb: 0.000% to 0.005%, Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, P: 0.000% to 0.400%, and one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0000% to 0.0100% in total; In mass%, the C content is [C], the Mo content is [Mo], the Cr content is [Cr], the Mn content is [Mn], the Ni content
  • the alloy has a chemical composition in which the transformation temperature Ar 3 (°C) defined by the following formula (1) is 750 to 1050°C, with the balance being Fe and impurities, where the sol. Al content is [sol. Al] and the P content is [P]: Furthermore, when observed by EBSD on a plane parallel to the steel sheet surface, the total area is S tot , the area of ⁇ 411 ⁇ oriented grains is S 411 , the area of ⁇ 100 ⁇ oriented grains is S 100 , the area of oriented grains having a Taylor factor M of more than 2.9 according to the following formula (2) is S tyl , the total area of oriented grains having the Taylor factor M of 2.9 or less is S tra , the average KAM value of the ⁇ 411 ⁇ oriented grains is K 411 , and the average KAM value of the oriented grains having the Taylor factor M of more than 2.9 is K tyl , and the following ( Formula (3) and formulas (4) to (7) are satisfied.
  • Ar 3 (°C) 1020-325 ⁇ [C]+33 ⁇ [Si]+287 ⁇ [P]+80 ⁇ [sol.
  • M (cos ⁇ cos ⁇ ) -1 ...(2)
  • ⁇ represents the angle between the stress vector and the slip direction vector of the crystal
  • ⁇ represents the angle between the stress vector and the normal vector of the slip plane of the crystal.
  • a non-oriented electrical steel sheet In mass percent, C: 0.0100% or less, Si: 1.50% to 4.00%, sol. Al: 0.0001% to 1.0%, S: 0.0100% or less, N: 0.0100% or less, Mn: 0.10% or more, One or more selected from Mn, Ni, Co, Pt, Pb, Au, and Cu: less than 2.50% in total; Mo: 0.0% to less than 2.5% Cr: 0.0% to less than 2.5% Ti: 0.000% to 0.005%, Nb: 0.000% to 0.005%, Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, P: 0.000% to 0.400%, and one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0000% to 0.0100% in total, and when the C content is [C], the Mo content is [Mo], the Cr content is [Cr], the Mn content
  • Al content is [sol. Al]
  • P content is [P]
  • the transformation temperature Ar 3 (°C) defined by the following formula (1) is 750 to 1050°C
  • the balance is Fe and impurities
  • the total area is S tot
  • the area of the ⁇ 411 ⁇ oriented grains is S 411
  • the area of the ⁇ 100 ⁇ oriented grains is S 100
  • the area of the oriented grains having a Taylor factor M of more than 2.9 according to the following formula (2) is S tyl
  • the total area of the oriented grains having the Taylor factor M of 2.9 or less is S tra
  • the average KAM value of the ⁇ 411 ⁇ oriented grains is K 411
  • the average KAM value of the oriented grains having the Taylor factor M of more than 2.9 is K tyl
  • the following formulas (3) and (4) to (7) are satisfied.
  • Ar 3 (°C) 1020-325 ⁇ [C]+33 ⁇ [Si]+287 ⁇ [P]+80 ⁇ [sol.
  • Al]-120 ⁇ ([Mn]+[Mo]+[Cu])-46 ⁇ ([Cr]+[Ni])...(1) M (cos ⁇ cos ⁇ ) -1 ...(2) S 411 /S 100 >1.00...(3) 0.20 ⁇ S tyl /S tot ⁇ 0.85 (4) 0.05 ⁇ S 411 /S tot ⁇ 0.80 (5) S 411 /S tra ⁇ 0.50 (6) K 411 /K tyl ⁇ 0.990 (7)
  • ⁇ represents the angle between the stress vector and the slip direction vector of the crystal
  • ⁇ represents the angle between the stress vector and the normal vector of the slip plane of the crystal.
  • a non-oriented electrical steel sheet In mass percent, C: 0.0100% or less, Si: 1.50% to 4.00%, sol. Al: 0.0001% to 1.0%, S: 0.0100% or less, N: 0.0100% or less, Mn: 0.10% or more, One or more selected from Mn, Ni, and Cu: less than 2.50% in total; Mo: 0.0% to less than 2.5% Cr: 0.0% to less than 2.5% Ti: 0.000% to 0.005%, Nb: 0.000% to 0.005%, Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, P: 0.000% to 0.400%, and One or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0000% to 0.0100% in total;
  • the alloy has a chemical composition in which the transformation temperature Ar 3 (°C) defined by the following formula (1) is 750 to 1050°C, with the balance being Fe and
  • Al content is [sol. Al], and the P content is [P], in mass %, Furthermore, when observed by EBSD on a plane parallel to the steel sheet surface, the following formulas (8) to (11) are satisfied when the total area is S tot , the area of the ⁇ 411 ⁇ oriented grains is S 411 , the area of the ⁇ 100 ⁇ oriented grains is S 100 , the area of the oriented grains having a Taylor factor M of more than 2.9 according to the following formula (2) is S tyl , and the total area of the oriented grains having a Taylor factor M of 2.9 or less is S tra .
  • Ar 3 (°C) 1020-325 ⁇ [C]+33 ⁇ [Si]+287 ⁇ [P]+80 ⁇ [sol.
  • Al 0.0001% to 1.0%, S: 0.0100% or less, N: 0.0100% or less, Mn: 0.10% or more, One or more selected from Mn, Ni, Co, Pt, Pb, Au, and Cu: less than 2.50% in total; Mo: 0.0% to less than 2.5% Cr: 0.0% to less than 2.5% Ti: 0.000% to 0.005%, Nb: 0.000% to 0.005%, Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, P: 0.000% to 0.400%, and one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0000% to 0.0100% in total;
  • the alloy has a chemical composition in which the transformation temperature Ar 3 (°C) defined by the following formula (1) is 750 to 1050°C, with the balance being Fe and impurities, where the C content is [C], the Mo content is [Mo], the Cr content is [ Cr], the M
  • Al content is [sol. Al], and the P content is [P], in mass %, Furthermore, when observed by EBSD on a plane parallel to the steel sheet surface, the following formulas (8) to (11) are satisfied when the total area is S tot , the area of the ⁇ 411 ⁇ oriented grains is S 411 , the area of the ⁇ 100 ⁇ oriented grains is S 100 , the area of the oriented grains having a Taylor factor M of more than 2.9 according to the following formula (2) is S tyl , and the total area of the oriented grains having a Taylor factor M of 2.9 or less is S tra .
  • Ar 3 (°C) 1020-325 ⁇ [C]+33 ⁇ [Si]+287 ⁇ [P]+80 ⁇ [sol.
  • non-oriented electrical steel sheet having a chemical composition in which the content of elements such as Cu and Ni is optimized while suppressing the addition of Mn so that rollability is not an issue, and which has small in-plane anisotropy and excellent magnetic properties averaged all around (averaged in all directions).
  • the non-oriented electrical steel sheet according to this embodiment is manufactured by subjecting a steel material having a chemical composition described below to a hot rolling process, a cold rolling process, an intermediate annealing process, and a skin pass rolling process. Furthermore, a non-oriented electrical steel sheet according to another embodiment of the present disclosure is manufactured by subjecting a steel material having a chemical composition described below to a cold rolling process, an intermediate annealing process, a skin pass rolling process, and a final annealing process.
  • the amount of Mn added is kept low to ensure rollability, and further, the components are adjusted, and then the hot rolling conditions are optimized to form an appropriate ⁇ -processed grain structure at the hot-rolled sheet stage, so that ⁇ 411 ⁇ oriented grains develop during the subsequent cold rolling and intermediate annealing.
  • the ⁇ 411 ⁇ oriented grains By making the number of ⁇ 411 ⁇ oriented grains greater than the ⁇ 100 ⁇ oriented grains at a stage before strain-induced grain growth occurs, the ⁇ 411 ⁇ oriented grains mainly encroach on the ⁇ 111 ⁇ oriented grains due to strain-induced grain growth, while at the same time suppressing the development of the ⁇ 100 ⁇ oriented grains, thereby producing a non-oriented electrical steel sheet with the ⁇ 411 ⁇ oriented grain as the main orientation.
  • the final annealing after skin pass rolling causes the steel sheet to undergo strain induced grain growth and/or normal grain growth.
  • sufficiently suppressing the development of the ⁇ 100 ⁇ orientation while enriching the ⁇ 411 ⁇ orientation grains is effective in reducing the in-plane anisotropy of the magnetic properties and improving the circumferential average (all-directional average).
  • the steel sheet after skin-pass rolling is the original sheet for the steel sheet after strain-induced grain growth and normal grain growth.
  • the steel sheet after skin-pass rolling and the steel sheet after strain-induced grain growth and normal grain growth will all be described as non-oriented electrical steel sheet.
  • the number of ⁇ 411 ⁇ orientation grains is further increased in the subsequent skin-pass rolling and final annealing, improving the magnetic properties all around.
  • the number of ⁇ 411 ⁇ orientation grains may be increased before skin-pass rolling in a process other than that described above.
  • non-oriented electrical steel sheet includes not only coil-shaped or cut-plate steel sheet, but also steel sheet processed into a specific shape as a material for products (components) such as motor cores, and further steel sheet laminated after processing to form motor cores.
  • the chemical composition of the non-oriented electrical steel sheet according to the embodiment of the present disclosure and the steel material used in the manufacturing method thereof will be described.
  • the chemical composition of the non-oriented electrical steel sheet indicates the content when the base material excluding the coating, etc. is taken as 100%.
  • the upper limit value of a certain numerical range may be replaced by the upper limit value of another numerical range described in stages, or may be replaced by a value shown in the examples.
  • the lower limit value of a certain numerical range may be replaced by the lower limit value of another numerical range described in stages, or may be replaced by a value shown in the examples.
  • the non-oriented electrical steel sheet according to this embodiment has a chemical composition in which ferrite-austenite transformation (hereinafter, ⁇ - ⁇ transformation) can occur, In mass percent, C: 0.0100% or less, Si: 1.50% to 4.00%, sol.
  • ⁇ - ⁇ transformation ferrite-austenite transformation
  • Al 0.0001% to 1.0%, S: 0.0100% or less, N: 0.0100% or less, Mn: 0.10% or more, One or more selected from Mn, Ni, and Cu: less than 2.50% in total; Mo: 0.0% to less than 2.5% Cr: 0.0% to less than 2.5% Ti: 0.000% to 0.005% Nb: 0.000% to 0.005% Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, P: 0.000% to 0.400%, and one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: 0.0000% to 0.0100% in total, and further, the contents of C, Si, P, sol. Al, Mn, Mo, Cu, Cr, and Ni satisfy the specified conditions described later, with the balance being Fe and impurities.
  • one or more elements selected from Mn, Ni, Co, Pt, Pb, Au, and Cu are contained in a total amount of less than 2.50%.
  • impurities examples include those contained in raw materials such as ores and scraps, and those contained during the manufacturing process.
  • C 0.0100% or less
  • the C content is set to 0.0100% or less.
  • the reduction in the C content contributes to the uniform improvement of the magnetic properties in all directions in the sheet surface.
  • the content is preferably 0.0005% or more.
  • Si 1.50% to 4.00% Silicon increases electrical resistance, reduces eddy current loss, reduces iron loss, increases the yield ratio, and improves punching workability into iron cores. If the Si content is less than 5.0%, these effects cannot be sufficiently obtained. Therefore, the Si content is set to 1.50% or more. On the other hand, if the Si content exceeds 4.00%, the magnetic flux density decreases and the hardness decreases. An excessive increase in Si content reduces punching workability and makes cold rolling difficult. Therefore, the Si content is set to 4.00% or less.
  • sol.Al 0.0001% to 1.0%
  • Sol. Al increases electrical resistance, reduces eddy current loss, and reduces iron loss.
  • Sol. Al also contributes to improving the relative magnitude of magnetic flux density B50 with respect to saturation magnetic flux density. If the sol. Al content is less than 0.0001%, these functions and effects cannot be fully obtained. Furthermore, Al also has the effect of promoting desulfurization in steelmaking. Therefore, the sol. Al content is set to 0.0001% or less. On the other hand, if the sol. Al content exceeds 1.0%, the magnetic flux density decreases, the yield ratio decreases, and punching workability decreases. shall be 1.0% or less.
  • sol. Al means acid-soluble Al that is not in the form of an oxide such as Al 2 O 3 and is soluble in acid.
  • the magnetic flux density B50 is the magnetic flux density in a magnetic field of 5000 A/m.
  • S is not an essential element and is contained, for example, as an impurity in steel. S inhibits recrystallization and grain growth during annealing by precipitating fine MnS. Therefore, the lower the S content, the lower the Such an increase in core loss and a decrease in magnetic flux density due to the inhibition of recrystallization and grain growth are remarkable when the S content exceeds 0.0100%. For this reason, the S content is set to 0.0100 Although there is no particular lower limit for the S content, it is preferable to set the S content to 0.0003% or more in consideration of the cost of desulfurization treatment during refining.
  • N 0.0100% or less
  • the Nitrogen content be 0.0010% or more.
  • the lower limit of the total content of Mn, Ni, and Cu is not particularly limited, but may be, for example, 0.10% or more, 0.50% or more, 1.00% or more, or even 2.00% or more.
  • Mn, Ni, Co, Pt, Pb, Au, and Cu are selected from Mn, Ni, Co, Pt, Pb, Au, and Cu: less than 2.50% in total.
  • Mn, Ni, and Cu, Co, Pt, Pb, and Au also increase the anisotropy of the magnetic properties, so in this embodiment, it is preferable to keep the content of these elements less than 2.50% in total. Furthermore, since these elements reduce the magnetic flux density, it is preferable to keep the content of these elements less than 2.00% in total.
  • the lower limit of the total of Mn, Ni, Co, Pt, Pb, Au, and Cu is not particularly limited, but may be, for example, 0.10% or more, 0.50% or more, or 1.00% or more, or even 2.00% or more.
  • the alloy cost of Co, Pt, Pb, and Au is high, active addition should be avoided. Furthermore, even considering the control of the Ar 3 transformation point, which is one of the features of this embodiment, it is preferable to control the Ar 3 transformation point by containing Mn, Ni, and Cu. For this reason, the total amount of Co, Pt, Pb, and Au should be less than 0.5%, more preferably 0.1% or less, and should be kept within the range of unavoidable elements, and there is no need to actively add them (it may be 0%).
  • the non-oriented electrical steel sheet and steel material according to this embodiment further satisfy the following condition as a condition under which ⁇ - ⁇ transformation can occur:
  • the C content is [C]
  • the Mo content is [Mo]
  • the Cr content is [Cr]
  • the Mn content is [Mn]
  • the Ni content is [Ni]
  • the Cu content is [Cu]
  • the Si content is [Si]
  • the sol. Al content is [sol. Al]
  • the P content is [P] in mass%
  • the transformation temperature Ar 3 (°C) defined by the following formula (1) is 750 to 1050°C.
  • Ar 3 (°C) 1020-325 ⁇ [C]+33 ⁇ [Si]+287 ⁇ [P]+80 ⁇ [sol.
  • the transformation point is not in an appropriate temperature range, so sufficient magnetic flux density cannot be obtained even if the manufacturing method described below is applied. If the Ar3 transformation point is less than 750 ° C, the hot rolling temperature is lowered, so the deformation resistance increases and the load on the rolling mill becomes too large, and the amount of added elements increases, which leads to a decrease in toughness of the hot-rolled sheet and the cold-rolled sheet, so this value is set as the lower limit.
  • Mn lowers the Ar3 transformation point, and in the component system of the non-oriented electrical steel sheet according to this embodiment, it is possible to refine the crystal grains of the hot-rolled sheet by phase transformation.
  • Mn is an element that increases the electrical resistance of steel and reduces iron loss. Therefore, Mn is contained at 0.1% or more. From this viewpoint, Mn is preferably contained at 0.5% or more. More preferably, it is contained at 1.0% or more.
  • Mn is an element that is prone to segregation, and if the content increases, not only does it cause cold work cracks due to segregation, but it also reduces the saturation magnetic flux density and prevents the increase in the magnetic flux density of the steel sheet. In addition, MnS is generated excessively, and the cold workability is reduced. Therefore, the upper limit of the Mn content is less than 2.5%. The upper limit of the Mn content is preferably 2.3 mass% or less, and more preferably 2.0 mass%.
  • Cu is an element that increases the electrical resistance of the steel sheet and reduces iron loss, similar to Mn, and reduces the Ar3 transformation point, enabling the fineness of the hot-rolled sheet grain size by phase transformation in the chemical composition of the non-oriented electrical steel sheet according to this embodiment.
  • the Cu content is high, it not only adversely affects the formation of texture in annealing after cold rolling due to an increase in recrystallization temperature, and causes embrittlement in the hot state, but also reduces the saturation magnetic flux density and prevents the increase in the magnetic flux density of the steel sheet, so caution is required.
  • Ni in an amount equal to or more than half the Cu content, embrittlement in the hot state caused by Cu can be reduced.
  • the upper limit of the Cu content is not limited, but is less than 2.5%. In addition, the upper limit of the Cu content is preferably 1.5 mass% or less, and more preferably 1.0 mass% or less.
  • the lower limit of the Cu content is not particularly limited, but may be, for example, 0.01% or more.
  • Ni (Ni: less than 2.5% in total with the above elements) Ni, like Mn, increases the electrical resistance of the steel sheet and reduces iron loss. Ni further lowers the A3 transformation point, enabling the crystal grains to be refined by phase transformation in the chemical composition of the non-oriented electrical steel sheet according to this embodiment.
  • the upper limit of the Ni content is not limited, but is less than 2.5%. In addition, the upper limit of the Ni content is preferably 1.0 mass% or less, and more preferably 0.7 mass% or less.
  • the lower limit of the Ni content is not particularly limited, but may be, for example, 0.01% or more.
  • Mo 0.0% to less than 2.58%
  • Mo is an element that lowers the Ar3 transformation point and enables the refinement of the grain size of the hot-rolled sheet by phase transformation in the chemical composition of the non-oriented electrical steel sheet according to this embodiment. Therefore, Mo may be contained as necessary, and it is preferable to contain 0.1% or more. On the other hand, since the inclusion of 2.5% or more of Mo significantly reduces the cold workability, the Mo content is set to less than 2.5%.
  • Cr 0.0% to less than 2.5%)
  • Cr is an element that lowers the Ar3 transformation point and enables the refinement of the grain size of the hot-rolled sheet by phase transformation in the chemical composition of the non-oriented electrical steel sheet according to this embodiment, and has the effect of improving not only strength adjustment and corrosion resistance, but also high-frequency characteristics in particular. Therefore, Cr may be contained as necessary, and it is preferable to contain 0.1% or more.
  • excessive Cr content not only saturates the effect and increases the raw material cost, but also reduces the saturation magnetic flux density and prevents the magnetic flux density of the steel sheet from increasing. For this reason, the Cr content is set to less than 2.5%.
  • Ti when present in the form of a solid solution or TiN, suppresses recrystallization and contributes to refinement of the austenite grain size. Therefore, Ti may be added as necessary, and it is recommended that Ti content be 0.001% or more. On the other hand, if the Ti content exceeds 0.005%, various precipitates such as TiN, TiS, and TiC are formed, which deteriorates the core loss characteristics, so the Ti content is set to 0.005% or less.
  • Nb when present in the form of a solid solution or NbN, suppresses recrystallization and contributes to refinement of the austenite grain size. Therefore, Nb may be added as necessary, and it is recommended that Nb be added in an amount of 0.001% or more. On the other hand, if the Nb content exceeds 0.005%, various precipitates such as NbN and NbC are generated and the core loss characteristics are deteriorated, so the Nb content is set to 0.005% or less.
  • Sn and Sb improve the texture after cold rolling and recrystallization, and increase the magnetic flux density. Therefore, these elements may be added as necessary, but if they are included in excess, the steel may become Therefore, the Sn content and the Sb content are both set to 0.400% or less. P may be added to ensure the hardness of the steel sheet after recrystallization, but excessive P should not be added. Therefore, the P content is set to 0.400% or less.
  • Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd react with S in the molten steel during casting of the molten steel to form precipitates of sulfides or oxysulfides, or both.
  • Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd may be collectively referred to as "coarse precipitate forming elements”.
  • the particle size of the precipitates of the coarse precipitate forming elements is about 1 ⁇ m to 2 ⁇ m, which is much larger than the particle size (about 100 nm) of fine precipitates such as MnS, TiN, AlN, TiC, and NbC. For this reason, these fine precipitates adhere to the precipitates of the coarse precipitate forming elements, and are less likely to inhibit recrystallization and grain growth during annealing such as intermediate annealing. In order to fully obtain these effects, it is preferable that the total amount of the coarse precipitate forming elements is 0.0005% or more.
  • the total content of these elements exceeds 0.0100%, the total amount of sulfides or oxysulfides or both will be excessive, inhibiting recrystallization and grain growth during annealing such as intermediate annealing. Therefore, the total content of the elements that form coarse precipitates is set to 0.0100% or less.
  • the remainder of the chemical composition other than those described above may be Fe and impurities.
  • Impurities refer to elements that are mixed in the steel raw materials and/or the steelmaking process.
  • other elements may be contained in place of a portion of Fe to the extent that the effect of the present invention is not lost.
  • B, O, V, Bi, W, and Y may each be contained in an amount of 0.10% or less.
  • the total amount of impurities is preferably 5.00% or less, and more preferably 1.00% or less.
  • the chemical composition is determined by the following method.
  • the chemical composition may be measured by a general analysis method for steel.
  • the chemical composition may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry).
  • the chemical composition is specified by measuring a test piece taken from the steel plate with a predetermined measuring device under conditions based on a calibration curve created in advance.
  • C and S may be measured using a combustion-infrared absorption method
  • N may be measured using an inert gas fusion-thermal conductivity method.
  • O may be measured using an inert gas fusion-non-dispersive infrared absorption method. If the surface has an insulating coating, it may be mechanically removed using a minitor or the like before being subjected to analysis.
  • the thickness of the non-oriented electrical steel sheet according to this embodiment is not particularly limited.
  • the preferred thickness of the non-oriented electrical steel sheet according to this embodiment is 0.10 to 0.50 mm. Normally, as the sheet thickness becomes thinner, the iron loss becomes lower, but the magnetic flux density becomes lower. In view of this, if the sheet thickness is 0.10 mm or more, the iron loss becomes lower and the magnetic flux density becomes higher. Furthermore, if the sheet thickness is 0.50 mm or less, low iron loss can be maintained.
  • the metal structure of the non-oriented electrical steel sheet according to this embodiment will be described.
  • the non-oriented electrical steel sheet of each embodiment will be specified based on the metal structure after skin pass rolling and the metal structure after final annealing.
  • the metal structure to be identified in this embodiment is identified in a cross section parallel to the plate surface of the steel plate, and is identified by the following procedure.
  • the sample is polished to a thickness of 7/8 so that the 1/8 thickness position is exposed, and the polished surface (polished surface polished to 1/8 from the plate surface side of the steel plate) is observed by EBSD (Electron Back Scattering Diffraction) using an SEM at an acceleration voltage of 25 kV and a magnification of 1000 times.
  • the observation field is 500 ⁇ m ⁇ 500 ⁇ m for the sample after skin pass rolling and 2000 ⁇ m ⁇ 2000 ⁇ m for the sample after stress relief annealing. Observation may be performed at several locations divided into several small sections.
  • the step interval during measurement is 0.3 ⁇ m for the sample after skin pass rolling and 2.0 ⁇ m for the sample after stress relief annealing.
  • the area of each orientation can be obtained by calculating the IPF (Inverse Pole Figure) from the EBSD observation field of view.
  • the KAM value can be obtained by calculating the orientation difference between measurement points using software such as OIM Analysis.
  • OIM Analysis 7.3 is used to set the limit (tolerance) for entering the KAM value to an orientation difference of 5° or less with adjacent pixels, and the average value of the calculated orientation difference between the nearest ( 1st neighbor) measurement points is used as the KAM value. Note that the setting of "Set zero point kernel to maximum misorientations" is left as the default and checked.
  • S tot Total area (observation area)
  • S tyl Total area of oriented grains with Taylor factor M exceeding 2.9 according to the following formula (2)
  • S tra Total area of oriented grains with Taylor factor M of 2.9 or less according to the following formula (2)
  • S 411 Total area of ⁇ 411 ⁇ oriented grains
  • S 100 Total area of ⁇ 100 ⁇ oriented grains
  • K tyl Average KAM value of oriented grains with Taylor factor M exceeding 2.9 according to the following formula (2)
  • K 411 Average KAM value of ⁇ 411 ⁇ oriented grains
  • the orientation tolerance of the crystal plane orientation is 10°.
  • the orientation tolerance is also 10°.
  • crystal grains having a plane orientation within ⁇ 10° of the specific plane orientation described in this disclosure are treated as crystal grains having that specific crystal orientation.
  • the Taylor factor M above is the Taylor factor when it is assumed that crystal slip deformation occurs in the slip plane ⁇ 110 ⁇ or ⁇ 112 ⁇ and in the slip direction ⁇ 111>, and no deformation occurs in the plate width direction, but compression deformation occurs in the plate thickness direction and elongation deformation occurs in the rolling direction.
  • each oriented grain satisfies the following formula (3) and formulas (4) to (6).
  • the ⁇ 100 ⁇ orientation is one orientation that is likely to exist in non-oriented electrical steel sheets. This orientation grain competes with the ⁇ 411 ⁇ orientation grains that should be preferentially grown.
  • the abundance ratio of ⁇ 411 ⁇ orientation grains is specified to be secured among orientations that have a relatively small Taylor factor and are unlikely to accumulate strain due to processing.
  • the area ratio S 411 /S 100 is greater than 1.00. In other words, there are more ⁇ 411 ⁇ oriented grains than ⁇ 100 ⁇ oriented grains. By sufficiently suppressing the growth of ⁇ 100 ⁇ oriented grains and making the ⁇ 411 ⁇ oriented grains the main orientation, the magnetic properties are improved on an average around the circumference (average of the rolling direction, width direction, direction at 45 degrees to the rolling direction, and direction at 135 degrees to the rolling direction).
  • the area ratio S 411 /S 100 is preferably 2.0 or more, and more preferably 3.0 or more.
  • the upper limit of the area ratio S411 / S100 does not need to be particularly limited. There is no problem even if the number of ⁇ 100 ⁇ oriented grains is zero and the value of the area ratio S411 / S100 is infinite. However, since reducing the number of ⁇ 100 ⁇ oriented grains to zero substantially imposes a large burden on manufacturing, the area ratio S411 / S100 is preferably 20 or less , more preferably 10 or less.
  • S tyl is the amount of orientations with relatively large Taylor factors.
  • the area ratio S tyl /S tot is defined as the area ratio S tyl /S tot to the total area, and the area ratio S tyl /S tot is set to 0.20 or more.
  • the area ratio S tyl /S tot is preferably 0.30 or more, more preferably 0.50 or more.
  • the upper limit of the area ratio S tyl /S tot is related to the amount of crystal orientation grains to be developed in the strain-induced grain growth process described below, but the condition is not simply determined by the ratio of the orientation that grows preferentially and the orientation that is encroached upon.
  • the area ratio S 411 /S tot of the ⁇ 411 ⁇ orientation grains to be developed in the strain-induced grain growth is 0.05 or more, so the area ratio S tyl /S tot is inevitably 0.95 or less.
  • the amount of the area ratio S tyl /S tot is excessive, preferential growth of the ⁇ 411 ⁇ orientation grains does not occur in relation to the strain described below.
  • the area ratio S tyl /S tot is 0.85 or less.
  • the area ratio S tyl /S tot is preferably 0.75 or less, more preferably 0.70 or less.
  • ⁇ 411 ⁇ orientation grains are preferentially grown.
  • the ⁇ 411 ⁇ orientation is one of the orientations in which the Taylor factor is relatively small and strain caused by processing is unlikely to accumulate, and is an orientation that can preferentially grow in the strain-induced grain growth process.
  • the presence of ⁇ 411 ⁇ orientation grains is essential, and in the first embodiment, the area ratio S 411 /S tot of the ⁇ 411 ⁇ orientation grains is set to 0.05 or more. If the area ratio S 411 /S tot of the ⁇ 411 ⁇ orientation grains is less than 0.05, the ⁇ 411 ⁇ orientation grains will not develop sufficiently due to the subsequent strain-induced grain growth.
  • the area ratio S 411 /S tot is preferably 0.10 or more, more preferably 0.20 or more.
  • the upper limit of the area ratio S 411 /S tot is determined according to the amount of crystal orientation grains to be eroded by strain-induced grain growth.
  • the area ratio S tyl /S tot of the orientation in which the Taylor factor to be eroded by strain-induced grain growth exceeds 2.9 is 0.20 or more, so the area ratio S 411 /S tot is 0.80 or less.
  • the area ratio S 411 /S tot is preferably 0.60 or less, more preferably 0.50 or less, and even more preferably 0.40 or less.
  • orientation grains that should be preferentially grown
  • these orientation grains compete with the ⁇ 411 ⁇ orientation grains that should be preferentially grown.
  • these orientation grains do not have as many easy axis of magnetization ( ⁇ 100> direction) in the steel sheet plane as the ⁇ 411 ⁇ orientation grains, and it is difficult to randomize the orientation selectivity in the steel sheet plane.
  • the presence ratio of ⁇ 411 ⁇ orientation grains is specified to be ensured among orientations that have a sufficiently small Taylor factor and are less likely to accumulate distortion due to processing.
  • the area of the oriented grains with a Taylor factor of 2.9 or less, including the oriented grains that are considered to compete with the ⁇ 411 ⁇ oriented grains in strain-induced grain growth, is defined as S tra .
  • the area ratio S 411 /S tra is set to 0.50 or more to ensure the superiority of the growth of the ⁇ 411 ⁇ oriented grains. If the area ratio S 411 /S tra is less than 0.50, the ⁇ 411 ⁇ oriented grains do not develop sufficiently due to strain-induced grain growth.
  • the area ratio S 411 /S tra is preferably 0.80 or more, more preferably 0.90 or more.
  • the ⁇ 411 ⁇ oriented grains can be reliably grown and better magnetic properties can be obtained.
  • the following formula (7) must be satisfied as a rule regarding the distortion. K 411 /K tyl ⁇ 0.990 (7)
  • Formula (7) is the ratio of the strain (average KAM value) accumulated in ⁇ 411 ⁇ oriented grains to the strain (average KAM value) accumulated in oriented grains with a Taylor factor of more than 2.9.
  • the KAM value is the orientation difference between adjacent measurement points within the same grain, and the KAM value is high at locations with a lot of strain. From a crystallographic point of view, for example, when compressive deformation is performed in the thickness direction in a plane strain state in a plane parallel to the thickness direction and the rolling direction, that is, when a steel sheet is simply rolled, the ratio K 411 /K tyl of K 411 to K tyl is generally smaller than 1.
  • K411 / Ktyl is set to 0.990 or less. If K411 / Ktyl exceeds 0.990, the specificity of the region to be encroached is lost, making it difficult for strain-induced grain growth to occur. K411 / Ktyl is preferably 0.970 or less, more preferably 0.950 or less.
  • the grain size is not particularly limited. This is because the relationship with the grain size is not very strong in the state in which appropriate strain-induced grain growth occurs due to the subsequent final annealing. In other words, whether the desired appropriate strain-induced grain growth occurs can be determined largely by the chemical composition of the steel sheet, as well as the relationship between the abundance (area) of each crystal orientation and the relationship between the amount of strain for each orientation.
  • the practical average crystal grain size is 300 ⁇ m or less. More preferably, it is 100 ⁇ m or less, even more preferably, it is 50 ⁇ m or less, and particularly preferably, it is 30 ⁇ m or less. The finer the crystal grain size, the easier it is to recognize the development of the desired crystal orientation due to strain-induced grain growth when the crystal orientation and strain distribution are appropriately controlled.
  • the average crystal grain size is 3 ⁇ m or more, more preferably, 8 ⁇ m or more, and even more preferably, 15 ⁇ m or more.
  • Embodiment 2 In the above-mentioned embodiment 1, the characteristics of the steel sheet are specified by specifying the strain of the steel sheet by the KAM value. In contrast, in embodiment 2, the steel sheet described in embodiment 1 is annealed for a sufficiently long time and further grain-grown is specified. In such a steel sheet, strain-induced grain growth is almost completed, and as a result, the strain is almost completely released, so that the characteristics are very favorable. In other words, a steel sheet in which ⁇ 411 ⁇ orientation grains are grown by strain-induced grain growth and then normal grain growth is performed by final annealing until the strain is almost completely released becomes a steel sheet with stronger accumulation in the ⁇ 411 ⁇ orientation.
  • Formula (8) has a different numerical range compared to formula (3) related to the non-oriented electrical steel sheet after the above-mentioned skin-pass rolling.
  • the strain-induced grain growth occurring during the final annealing causes the ⁇ 411 ⁇ orientation grains to grow further and increase their area, improving the magnetic properties on the circumferential average (average of the rolling direction, width direction, 45-degree direction relative to the rolling direction, and 135-degree direction relative to the rolling direction).
  • the definitions of formulas (9) to (11) have different numerical ranges compared to formulas (4) to (6) related to the non-oriented electrical steel sheet after skin-pass rolling described above.
  • the area ratio S tyl /S tot is less than 0.55.
  • the total area S tyl may be zero.
  • the upper limit of the area ratio S tyl /S tot is determined as one of the parameters indicating the degree of progress of the growth of the ⁇ 411 ⁇ oriented grains.
  • the area ratio S tyl /S tot being 0.55 or more indicates that the oriented grains having a Taylor factor of more than 2.9 that should be eaten at the stage of strain-induced grain growth are not eaten sufficiently. In this case, the magnetic properties are not sufficiently improved.
  • the area ratio S tyl /S tot is preferably 0.40 or less, more preferably 0.30 or less. Since the area ratio S tyl /S tot is preferably small, the lower limit is not specified and may be 0.00.
  • the area ratio S411 / Stot is set to be more than 0.30. If the area ratio S411 / Stot is 0.30 or less, the magnetic properties are not sufficiently improved.
  • the area ratio S411 / Stot is preferably 0.40 or more, more preferably 0.50 or more.
  • the situation where the area ratio S411 / Stot is 1.00 means that all the crystal structure is oriented in the ⁇ 411 ⁇ direction and no other oriented grains exist, and the second embodiment is also intended for this situation.
  • the relationship between the ⁇ 411 ⁇ oriented grains and the ⁇ 411 ⁇ oriented grains, which are considered to have competed with the ⁇ 411 ⁇ oriented grains in the strain-induced grain growth, is also important.
  • the area ratio S 411 /S tra is sufficiently large, the superiority of the ⁇ 411 ⁇ oriented grains is ensured even in the situation of normal grain growth after the strain-induced grain growth, and the magnetic properties are good.
  • the area ratio S 411 /S tra is set to 0.60 or more.
  • the area ratio S 411 /S tra is preferably 0.70 or more, more preferably 0.80 or more.
  • there is no need to set a particular upper limit for the area ratio S 411 /S tra and all grains having a Taylor factor of 2.9 or less may be grains having the ⁇ 411 ⁇ orientation.
  • the practical average crystal grain size of the ⁇ 411 ⁇ orientation grains which are relatively coarse grains in the second embodiment, is preferably 500 ⁇ m or less. More preferably, the average crystal grain size of the ⁇ 411 ⁇ orientation grains is 400 ⁇ m or less, even more preferably 300 ⁇ m or less, and particularly preferably 200 ⁇ m or less.
  • the lower limit of the average crystal grain size of the ⁇ 411 ⁇ orientation grains is preferably 40 ⁇ m or more, more preferably 60 ⁇ m or more, and even more preferably 80 ⁇ m or more, assuming that sufficient preferential growth of the ⁇ 411 ⁇ orientation is ensured.
  • the non-oriented electrical steel sheet of embodiment 2 has the best magnetic properties in the 45° direction among the three directions that form angles of 0°, 45°, and 90° with the rolling direction.
  • the magnetic properties in the 45° direction are the average value of the magnetic properties in the two directions that form angles of +45° and -45° with the rolling direction.
  • the magnetic flux density B50 in the direction at 45° to the rolling direction is preferably not less than 1.75 T. Note that in the non-oriented electrical steel sheet according to embodiment 2, the magnetic flux density in the direction at 45° to the rolling direction is high, the in-plane anisotropy is small, and a high magnetic flux density can be obtained even in the circumferential average (all-direction average).
  • the magnetic flux density B50 value in the rolling direction is B50L
  • the magnetic flux density B50 value in the 45° direction to the rolling direction is B50D
  • the magnetic flux density B50 value in the 90° direction to the rolling direction is B50C .
  • the magnetic flux density can be measured by cutting a 55 mm square sample at 45°, 0°, etc., relative to the rolling direction and using a single sheet magnetic measuring device.
  • Magnetic measurements may be performed using the methods described in JIS C 2550-1 (2011) and JIS C 2550-3 (2019), or the methods described in JIS C 2556 (2015).
  • the electromagnetic circuit may be measured using a 55 mm square test piece conforming to JIS C 2556 (2015), or a device capable of measuring even smaller test pieces.
  • the non-oriented electrical steel sheet according to the present embodiment is obtained by a production method including a hot rolling step, a cold rolling step, an intermediate annealing step, a skin pass rolling step, and a final annealing step. Preferred conditions for each step will now be described.
  • the Ar3 temperature is the transformation temperature Ar3 (°C) defined by the above formula (1).
  • Hot rolling process In the hot rolling process, hot rolling is performed on the steel material satisfying the above-mentioned chemical composition to produce a hot rolled steel sheet.
  • the hot rolling process includes a heating process and a rolling process.
  • the steel material is, for example, a slab produced by normal continuous casting, and steel material of the above-mentioned composition is produced by a well-known method.
  • molten steel is produced in a converter or electric furnace.
  • the produced molten steel is subjected to secondary refining in a degassing facility or the like to produce molten steel having the above-mentioned chemical composition (the chemical composition does not change substantially in subsequent processes).
  • the molten steel is cast into a slab by a continuous casting method or an ingot casting method.
  • the cast slab may be rolled into blooms.
  • the steel material having the above-mentioned chemical composition it is preferable to heat the steel material having the above-mentioned chemical composition to 1000 to 1200°C.
  • the steel material is placed in a heating furnace or a soaking furnace and heated in the furnace.
  • the holding time at the above-mentioned heating temperature in the heating furnace or soaking furnace is not particularly limited, but is, for example, 30 to 200 hours.
  • Hot rolling In the rolling process, multiple passes of rolling are performed on the steel material heated in the heating process to produce hot-rolled steel plate.
  • “pass” means that the steel plate passes through one rolling stand having a pair of work rolls and is reduced.
  • Hot rolling may be performed, for example, by tandem rolling using a tandem rolling mill including multiple rolling stands arranged in a row (each rolling stand having a pair of work rolls) to perform multiple passes, or by reverse rolling using a pair of work rolls to perform multiple passes. From the viewpoint of productivity, it is preferable to perform multiple rolling passes using a tandem rolling mill.
  • the steel material is, for example, a slab manufactured by normal continuous casting.
  • the slab is heated to the Ar 3 temperature or higher, which is a temperature range in which the steel structure becomes a ⁇ phase.
  • Hot rolling is started in a temperature range in which the steel structure becomes a ⁇ phase (hereinafter, this temperature range may be described as the ⁇ range), and is performed in the ⁇ range except for a necessary number of passes including the final pass of the finish rolling, and is completed by performing a necessary number of passes including the final pass in a temperature range in which the ⁇ phase exists in the steel structure (hereinafter, this temperature range may be described as the ⁇ range).
  • the front to middle stages of rough rolling and finish rolling are performed in the ⁇ range, and the rear stage of finish rolling is performed in the ⁇ range.
  • the reduction ratio in the temperature range from the Ar 3 temperature or higher to Ar 3 +20°C or lower immediately before the final rolling in the ⁇ range is 10% or more.
  • the rolling reduction in the temperature range of the finish rolling temperature FT or higher and lower than the Ar 3 temperature is set to 15% or more in total, taking into consideration the case where rolling is performed in multiple passes.
  • the finish rolling temperature FT refers to the surface temperature of the hot-rolled steel sheet immediately after finish rolling.
  • the lower limit of the finish rolling temperature FT is not particularly limited, but is set to, for example, Ar3 temperature -100°C or more.
  • Rolling in a temperature range above Ar3 + 20°C just before the final rolling in the ⁇ region has almost no effect on the grain size of the deformed ⁇ grains before the phase transformation, and coarse deformed ⁇ grains are formed after the transformation, which is unrelated to the accumulation in the ⁇ 411 ⁇ crystal orientation in the final product. If the rolling reduction ratio in the temperature range from Ar3 temperature to Ar3 + 20°C just before the final rolling in the ⁇ region is less than 10%, the accumulation of strain in the processed ⁇ grains before the phase transformation is insufficient, coarse processed ⁇ grains are formed, and accumulation in the ⁇ 411 ⁇ crystal orientation in the final product becomes difficult.
  • the rolling reduction ratio in the temperature range from Ar3 temperature to Ar3 + 20°C is preferably 15% or more, more preferably 20% or more.
  • the lower limit temperature for rolling in the ⁇ region is not particularly limited, but since a lower rolling temperature increases the load on the rolling mill, it is preferable to set the lower limit temperature to 600° C. or higher.
  • the rolling temperature may fluctuate above or below the specified judgment temperature ( Ar3 temperature, or Ar3 + 20°C) during the rolling pass due to the competition between the temperature drop caused by roll contact and cooling lubricant and the temperature rise caused by processing. In this embodiment, such a situation is handled as follows.
  • the temperature on the entry side is TPI (°C)
  • the thickness on the entry side is TCI (mm)
  • the temperature on the exit side is TPO (°C)
  • the thickness on the exit side is TCO (mm)
  • the above assumption also assumes that the exit temperature of the rolling pass is higher than the entry temperature.
  • the exit temperature of the rolling pass is higher than the entry temperature.
  • the temperature fluctuations on either side of the Ar 3 temperature may occur over multiple passes.
  • the rolling conditions in the ⁇ region are the "final rolling process in the ⁇ region".
  • the rolling conditions in the ⁇ region are the “rolling process in the ⁇ region immediately before the above-mentioned "final rolling process in the ⁇ region".
  • the rolling temperature after starting hot rolling in the ⁇ region changes as follows: ⁇ region (start of hot rolling) ⁇ ⁇ region 1 ⁇ ⁇ region 1 ⁇ ⁇ region 2 ⁇ ⁇ region 2 ⁇ ⁇ region 3 (end of hot rolling), if the ⁇ region 3 and the ⁇ region 2 meet the conditions of this embodiment, it is possible to obtain the disclosed steel sheet.
  • the rolling temperature in each pass can be measured, for example, by a thermometer installed at the entry or exit of the rolling stand that performs the reduction of the target pass. It is not necessary to install thermometers at the entry and exit of all rolling stands whose temperature range falls within the range disclosed herein, and the rolling temperature at intermediate rolling stands may be calculated from the actual temperatures of thermometers appropriately installed before and after them. Rather, in current hot rolling, control using such calculated temperatures is usually performed.
  • the finish rolling temperature FT is preferably set to be lower than the Ar3 temperature.
  • the hot-rolled steel sheet is coiled without annealing the hot-rolled sheet.
  • the temperature during coiling is preferably more than 450°C and less than 650°C.
  • Cold rolling process In the cold rolling process, the hot rolled steel sheet after the cooling process is cold rolled to obtain a cold rolled steel sheet. Specifically, after hot rolling, the hot rolled steel sheet is pickled and then cold rolled. In the cold rolling, the reduction is preferably 80% to 92%. Note that the higher the reduction, the easier it is for crystal grains having the ⁇ 411 ⁇ crystal orientation to grow due to subsequent bulging, but the sheet shape deteriorates and operation becomes more difficult.
  • the rolling shape ratio is 5.0 or less.
  • intermediate annealing is performed on the cold-rolled steel sheet.
  • the temperature of intermediate annealing is controlled to less than 900°C.
  • the temperature of intermediate annealing is preferably 800°C or less, more preferably 750°C or less. If the temperature of intermediate annealing is 900°C or more, excessive grain growth of crystal grains will occur, and even if skin-pass rolling and final annealing are performed as described below, accumulation in the ⁇ 411 ⁇ crystal orientation will be difficult to proceed.
  • the temperature of intermediate annealing is preferably 600°C or more, more preferably 700°C or more.
  • the temperatures described here are based on continuous annealing, and the intermediate annealing time is preferably in the range of 5 to 120 seconds.
  • the annealing temperature range and annealing time range are suitable conditions for allowing the ⁇ 411 ⁇ crystal grains, which have already formed in no small amount by the cold rolling step, to grow appropriately by bulging, and for creating a state in which strain-induced grain growth is likely to occur by the skin-pass rolling and final annealing described below.
  • the crystal grains having the ⁇ 411 ⁇ crystal orientation are less likely to accumulate strain due to skin pass rolling, while the crystal grains belonging to the orientation group having the ⁇ 111 ⁇ plane orientation called ⁇ -fiber, such as ⁇ 111 ⁇ 112> and ⁇ 111 ⁇ 110>, tend to accumulate strain, and the crystal grains having the ⁇ 411 ⁇ crystal orientation with less strain in the subsequent annealing use the difference in strain as a driving force to eat away at these ⁇ -fiber orientation grains.
  • This encroachment phenomenon that occurs with the difference in strain as a driving force is called strain induced grain boundary migration (hereinafter, SIBM). It is preferable that the reduction ratio of the skin pass rolling is 5% to less than 25%.
  • the reduction rate is less than 5%, the amount of strain is too small, so that the subsequent annealing does not cause strain-induced grain boundary migration (hereinafter, SIBM), and the crystal grains having the ⁇ 411 ⁇ crystal orientation do not become large.
  • SIBM strain-induced grain boundary migration
  • the reduction rate is 25% or more, the amount of strain becomes too large, and recrystallization nucleation (hereinafter, nucleation) occurs, in which new crystal grains are born from crystal grains having the ⁇ -fiber orientation. In this nucleation, most of the grains born are crystal grains having the ⁇ -fiber orientation, so the magnetic properties become poor. From the viewpoint of increasing the average magnetic flux density in the sheet surface and reducing the anisotropy, it is more preferable to set the reduction rate of the skin pass rolling to 5% to 15%.
  • non-oriented electrical steel sheet is to have the above-mentioned strain distribution
  • the reduction rate RR1 (%) in cold rolling is defined as follows.
  • Reduction rate RR1 (%) (1 - thickness after the final pass of cold rolling / thickness before the first pass of cold rolling) x 100
  • the reduction ratio RR2 (%) in skin pass rolling is defined as follows.
  • Reduction rate RR2 (%) (1 - thickness after the final pass of skin pass rolling / thickness before the first pass of skin pass rolling) x 100
  • the steel sheet after the skin pass rolling is subjected to final annealing.
  • This final annealing generates SIBM driven by the strain difference for each crystal orientation due to skin pass rolling, and crystal grains having the ⁇ 411 ⁇ crystal orientation targeted by the present disclosure grow preferentially, increasing the ⁇ 411 ⁇ crystal orientation concentration of the steel sheet.
  • This annealing condition can be appropriately set by a person skilled in the art while confirming the occurrence of SIBM, and is not particularly limited, but examples include annealing at 700 to 950 ° C for 1 to 100 seconds in the case of continuous annealing and annealing at 650 to 850 ° C for 0.5 to 2 hours in the case of batch annealing.
  • the non-oriented electrical steel sheet according to this embodiment can be manufactured as described above.
  • this manufacturing method is only one example of a method for manufacturing the non-oriented electrical steel sheet according to this embodiment, and is not intended to limit the manufacturing method.
  • the non-oriented electrical steel sheet according to this embodiment can be manufactured.
  • the final annealing process can be performed after skin pass rolling, for example, at a steel sheet manufacturer in the form of a steel sheet coil or as a cut sheet.
  • the steel sheet can be shipped without undergoing the final annealing process, and the motor manufacturer can process the steel sheet into a predetermined shape as a motor core, laminate the steel sheet, and then perform final annealing in the core shape.
  • this process can also be performed as "strain relief annealing" that is generally performed on motor cores at motor manufacturers.
  • the final annealing may be performed by both the steel sheet manufacturer and the motor manufacturer as two or more final annealings.
  • a steel sheet with a large amount of remaining strain or a relatively small grain size has high strength, and is particularly suitable for use as a non-oriented electrical steel sheet for a rotor core to suppress deformation due to centrifugal force accompanying the rotation of the core.
  • a steel sheet with sufficient strain release and coarse grain size is particularly suitable for use as a non-oriented electrical steel sheet for a stator core to suppress iron loss.
  • the steel member made of the non-oriented electromagnetic steel sheet according to this embodiment is applied to, for example, the iron core (motor core) of a rotating electric machine.
  • the iron core used in the rotating electric machine is produced by cutting out individual flat thin plates from the non-oriented electromagnetic steel sheet according to this embodiment and appropriately stacking these flat thin plates.
  • This iron core uses non-oriented electromagnetic steel sheet with excellent magnetic properties, so iron loss is kept low, resulting in a rotating electric machine with excellent torque.
  • the steel member made of the non-oriented electromagnetic steel sheet according to this embodiment can also be applied to products other than the iron core of a rotating electric machine, such as the iron core of a linear motor or a stationary machine (reactor or transformer).
  • non-oriented electrical steel sheet according to the embodiment of the present disclosure will be specifically described with reference to an example.
  • the example shown below is merely one example of the non-oriented electrical steel sheet according to the embodiment of the present disclosure, and the non-oriented electrical steel sheet according to the present disclosure is not limited to the example below.
  • the molten steel was cast to produce an ingot with the composition shown in Table 1 below. Note that "Co, etc.” in Table 1 indicates the respective contents of Co, Pt, Pb, and Au.
  • the produced ingot was then hot rolled under the conditions shown in Table 1 to obtain a hot-rolled sheet. Next, it was cold rolled under the conditions shown in Table 1 to obtain a cold-rolled sheet.
  • the cold-rolled sheet was subjected to intermediate annealing in a non-oxidizing atmosphere at the temperature shown in Table 2 for 30 seconds, and then subjected to a second cold rolling (skin pass rolling) at the reduction ratio shown in Table 2.
  • the cut out test piece was processed to reduce its thickness to 7/8, and the processed surface (the polished surface where the steel plate was polished to 1/8 from the plate side) was observed with EBSD (step interval: 0.3 ⁇ m) as described above. From the EBSD observation, the area and average KAM value of the oriented grains of the types shown in Table 3 were determined.
  • the steel sheet was subjected to final annealing at 800° C. for 2 hours. From the steel sheet after final annealing, a 55 mm square sample was taken as a measurement sample. At this time, a sample in which one side of the sample piece was parallel to the rolling direction and a sample inclined at 45 degrees to the rolling direction were taken. The sample taking was performed using a shearing machine. Next, in order to investigate the texture, a part of the steel sheet was cut out, the cut out test piece was processed to reduce the thickness to 7/8, and the processed surface (the polished surface obtained by polishing the steel sheet from the sheet surface side to 1/8) was observed by EBSD (step interval: 2.0 ⁇ m) in the above-mentioned manner.
  • EBSD step interval: 2.0 ⁇ m
  • the areas and average KAM values of the orientation grains of the types shown in Table 3 were obtained by EBSD observation. Then, the magnetic flux density B50L in the rolling direction, the magnetic flux density B50D in the 45° direction relative to the rolling direction, and the magnetic flux density B50C in the 90° direction relative to the rolling direction were measured in accordance with JIS C2556 (2015). The measurement results are shown in Table 3.
  • the "average value” shown in Table 3 is the average value of the magnetic flux density B50 all around (the average value of the magnetic flux density B50 in the rolling direction, the 90° direction relative to the rolling direction, and the 45° (135°) direction relative to the rolling direction).
  • the rollability was evaluated as follows: In a 1 m long region centered on a position 10 m in the longitudinal direction from the outermost longitudinal tip of the cold-rolled sheet coil (top part), a position 1/2 the total length of the coil in the longitudinal direction from the outermost longitudinal tip of the coil (middle part), and a position 10 m in the longitudinal direction from the innermost longitudinal tip of the coil (bottom part), if cracks having a length of 1 cm or more were present in a total of two or more places on both end faces in the sheet width direction of the coil, the evaluation was given as "N", and otherwise as "Y".
  • test piece was processed to reduce its thickness to half, and the processed surface was observed by EBSD in the manner described above to determine the area and average KAM value of the oriented grains of the types shown in Table 4. The results are shown in Table 4 together with the magnetic properties and rolling properties.
  • This disclosure makes it possible to provide non-oriented electrical steel sheets that have small in-plane anisotropy and excellent magnetic properties on average around the circumference (average in all directions), making them extremely useful in industry.

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Abstract

L'invention concerne une plaque d'acier électromagnétique non orienté qui présente une composition chimique prédéfinie, et dans laquelle, lors d'une observation par diffraction des électrons rétrodiffusés au moyen d'un plan parallèle à la surface de la plaque d'acier, la superficie totale (Ｓtot), la superficie (Ｓ411) de grains d'orientation ｛４１１｝, la superficie (Ｓ100) de grains d'orientation ｛１００｝, la superficie (Ｓtyl) de grains d'orientation tels que le facteur de Taylor (M) conformément à la formule (2) dépasse 2,9, la superficie totale (Ｓtra) de grains d'orientation tels que le facteur de Taylor (M) est inférieur ou égal à 2,9, la valeur KAM moyenne (Ｋ411) des grains d'orientation ｛４１１｝, et la valeur KAM moyenne (Ｋtyl) de grains d'orientation tels que le facteur de Taylor (M) dépasse 2,9, satisfont les formules (3) à (7).　Ｍ＝（cosφ×cosλ）-1　（２）　Ｓ411／Ｓ100＞１,００　（３）　０,２０≦Ｓtyl／Ｓtot≦０,８５　（４）　０,０５≦Ｓ411／Ｓtot≦０,８０　（５）　Ｓ411／Ｓtra≧０,５０　（６）　Ｋ411／Ｋtyl≦０,９９０　（７）
PCT/JP2024/000133 2023-01-10 2024-01-09 Plaque d'acier électromagnétique non orienté WO2024150732A1 (fr)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020153387A1 (fr) * 2019-01-24 2020-07-30 Ｊｆｅスチール株式会社 Tôle d'acier électromagnétique à grains non orientés et son procédé de production
JP2020139198A (ja) * 2019-02-28 2020-09-03 日本製鉄株式会社 無方向性電磁鋼板
JP2021134383A (ja) * 2020-02-26 2021-09-13 日本製鉄株式会社 無方向性電磁鋼板
WO2022196805A1 (fr) * 2021-03-19 2022-09-22 日本製鉄株式会社 Tôle d'acier électromagnétique non directionnelle et procédé pour la fabrication de celle-ci
WO2022211007A1 (fr) * 2021-04-02 2022-10-06 日本製鉄株式会社 Tôle d'acier électrique non orientée
KR20230094459A (ko) * 2021-12-21 2023-06-28 주식회사 포스코 무방향성 전기강판 및 그 제조방법

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020153387A1 (fr) * 2019-01-24 2020-07-30 Ｊｆｅスチール株式会社 Tôle d'acier électromagnétique à grains non orientés et son procédé de production
JP2020139198A (ja) * 2019-02-28 2020-09-03 日本製鉄株式会社 無方向性電磁鋼板
JP2021134383A (ja) * 2020-02-26 2021-09-13 日本製鉄株式会社 無方向性電磁鋼板
WO2022196805A1 (fr) * 2021-03-19 2022-09-22 日本製鉄株式会社 Tôle d'acier électromagnétique non directionnelle et procédé pour la fabrication de celle-ci
WO2022211007A1 (fr) * 2021-04-02 2022-10-06 日本製鉄株式会社 Tôle d'acier électrique non orientée
KR20230094459A (ko) * 2021-12-21 2023-06-28 주식회사 포스코 무방향성 전기강판 및 그 제조방법

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