Hot-rolled annealed sheet for non-oriented electromagnetic steel sheet, method for manufacturing same, and method for manufacturing non-oriented electromagnetic steel sheet

Abstract

Provided is such a hot-rolled annealed sheet for a non-oriented electrical steel sheet that this hot-rolled annealed sheet is capable of realizing both sheet fracture prevention during cold rolling and excellent magnetic properties after performing cold-rolled sheet annealing. This is because this hot-rolled annealed sheet is configured in a manner such that an average crystal grain size on a cross-sectional surface thereof in a rolling direction after pickling is 40 to 250 µm, and that an integrated intensity of an Fe-Al-based oxide on a steel sheet surface layer is 200 cps·deg or lower when measured by X-ray diffraction. Such configuration is either achieved by obtaining a hot-rolled annealed sheet after heating and hot rolling, under given conditions, a steel slab containing given amounts of C, Si, Mn, P, S, Al, N, O, Sn, and Sb, and then by performing shot blasting and then pickling on the sheet; or is achieved by obtaining a hot-rolled annealed sheet after heating and hot rolling, under given conditions, the above steel slab, and then by performing brush grinding and then pickling on the sheet. Further, a non-oriented electrical steel sheet can be manufactured using the above hot-rolled annealed sheet.

Description

Technical Field

[0001] The present invention relates to a hot-rolled annealed sheet that is used for manufacturing a non-oriented electrical steel sheet and is superior in fracture resistance during cold rolling; a method for manufacturing such a hot-rolled annealed sheet; and a method for manufacturing a non-oriented electrical steel sheet, using such a hot-rolled annealed sheet.Background Art

[0002] In recent years, there have been stronger needs to reduce exhaust CO 2 emissions and save energy out of a higher awareness of environmental problems; even electric apparatuses such as electric vehicles are now strongly required to exhibit a higher efficiency. For this reason, non-oriented electrical steel sheets that are widely used as iron core materials for motors installed in electric apparatuses are also now strongly required to possess improved iron loss properties. Thus, attempts have been made to improve iron loss properties by, for example, adding large amounts of specific resistance-enhancing elements such as Si and Al, or reducing sheet thickness.

[0003] However, adding large amounts of Si, Al or the like and reducing final sheet thickness lead to a higher manufacturing load during cold rolling, which implies that in addition to improving magnetic properties, it is also critical to prevent troubles such as steel sheet fracture from happening during cold rolling.

[0004] Here, in order to solve this problem, there has been proposed a technique of, for example, suppressing sheet fracture during cold rolling by controlling a hot-rolled sheet annealing temperature and thus improving toughness.

[0005] For example, Patent Literature 1 discloses a non-oriented electrical steel sheet that contains, by mass%, C: 0.0010 to 0.0050%, Si: 2.5 to 4.0%, Al: 0.2 to 2.0%, Mn: 0.05 to 2.0%, P: 0.005 to 0.15%, S: 0.0001 to 0.0030%, Ti: 0.0005 to 0.0030%, N: 0.0010 to 0.0030%, and a balance consisting of Fe and unavoidable impurities, in which the sheet thickness of its iron matrix is 0.10 to 0.35 mm, and an Al concentration in a depth direction from the surface of the iron matrix is such that a relational expression shown by the following formula (1) is satisfied. According to Patent Literature 1, when a soaking temperature exceeds 1100°C in hot-rolled sheet annealing, or when a soaking time is longer than 300 sec, the iron matrix may fracture during cold rolling performed in a later stage. 0.1 ≤ A 1 x ≤ 2 μm / A 1 x = 10 μm < 1.0

[0006] Here, in the above formula (1), x represents a depth [µm] from the surface of the iron matrix, Al (x≤2 µm) represents an average value of Al concentrations from the surface of the iron matrix to a depth of 2 µm, and Al (x=10 µm) represents an Al concentration at a position of a depth of 10 µm.Citation ListPatent Literature

[0007] Patent Literature 1: JP-A-2018-021241Summary of InventionTechnical Problem

[0008] However, the conventional technique disclosed in the above patent literature has the following problem.

[0009] As a result of conducting a series of studies, the inventors of the present invention found that the controls on the hot-rolled sheet annealing condition that are described in Patent Literature 1 alone are not necessarily able to suppress the occurrence of fracture, and that it is difficult to realize both a fracture resistance during cold rolling and favorable magnetic properties after performing cold-rolled sheet annealing.

[0010] The present invention was made in view of such problem. It is an object of the present invention to provide a hot-rolled annealed sheet that is used for manufacturing a non-oriented electrical steel sheet and is superior in fracture prevention during cold rolling after performing hot-rolled sheet annealing and magnetic properties after performing cold-rolled sheet annealing; a method for manufacturing such hot-rolled annealed sheet; and a method for manufacturing a non-oriented electrical steel sheet, using such hot-rolled annealed sheet.Solution of Problem

[0011] The hot-rolled annealed sheet of the present invention that is used to manufacture a non-oriented electrical steel sheet and is able to advantageously solve the above problem, is configured as follows. [1] A hot-rolled annealed sheet for a non-oriented electrical steel sheet having a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities, wherein an average crystal grain size on a cross-sectional surface of the steel sheet in a rolling direction is 40 to 250 µm, and an integrated intensity of an Fe-Al-based oxide on a steel sheet surface layer is 200 cps·deg or lower when measured by X-ray diffraction. [2] The hot-rolled annealed sheet for a non-oriented electrical steel sheet according to [1], wherein, in addition to the chemical composition, the hot-rolled annealed sheet further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080%, group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030%, and group D: B, totaling 0.0001 to 0.0020%. [3] The hot-rolled annealed sheet for a non-oriented electrical steel sheet according to [1] or [2], wherein in addition to the chemical composition, the hot-rolled annealed sheet further contains, by mass%, at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020%, group I: Co, totaling 0.001 to 0.100% , and group J: As, totaling 0.0005 to 0.020%. The method of the present invention for manufacturing the hot-rolled annealed sheet that is used to manufacture a non-oriented electrical steel sheet, which is able to advantageously solve the above problem, is configured as follows. [4] A method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet, including: a hot rolling step of obtaining a hot-rolled steel sheet by heating and hot-rolling a steel slab having a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities; a hot-rolled sheet annealing step of obtaining a hot-rolled annealed sheet by annealing the hot-rolled steel sheet; a shot blasting step of performing shot blasting on the hot-rolled annealed sheet; and a pickling step of pickling the hot-rolled annealed sheet that has been shot-blasted, wherein: in the hot rolling step, a heating temperature of the steel slab is set to 1150°C or lower, a finishing rolling temperature is set to 960°C or lower, and a coiling temperature is set to 700°C or lower; in the hot-rolled sheet annealing step, an annealing temperature is set to 800 to 1100°C; in the shot blasting step, shot blasting is performed on the hot-rolled annealed sheet at a projection density of 10 to 40 kg / m 2< ; in the pickling step, the shot-blasted steel sheet is pickled at a hydrochloric acid concentration of 5% or higher and a pickling temperature of 70°C or higher for a pickling time of 10 to 120 seconds. [5] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to [4], wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080% , group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030% , and group D: B, totaling 0.0001 to 0.0020%. [6] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to [4] or [5], wherein in addition to the chemical composition, the steel slab further contains, by mass, at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020%, group I: Co, totaling 0.001 to 0.100%, and group J: As, totaling 0.0005 to 0.020%. [7] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of [4] to [6], wherein before annealing the hot-rolled steel sheet, the hot-rolled steel sheet is subjected to rolling and / or stretch bending at an elongation rate of 0.1 to 10.0%. [8] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of [4] to [7], wherein after the pickling step, both the front and back surfaces of the pickled steel sheet are subjected to brush grinding. The method of the present invention for manufacturing a non-oriented electrical steel sheet, which is able to advantageously solve the above problem, is configured as follows. [9] A method for manufacturing a non-oriented electrical steel sheet, including: obtaining a cold-rolled sheet with a final sheet thickness by subjecting the hot-rolled annealed sheet manufactured by the method according to any one of [4] to [8] to cold rolling once or twice or more with intermediate annealing being performed therebetween and obtaining a cold-rolled annealed sheet by performing cold-rolled sheet annealing on the cold-rolled sheet at a soaking temperature of 700 to 1100°C. Another method of the present invention for manufacturing a hot-rolled annealed sheet that is used to manufacture a non-oriented electrical steel sheet, which is able to advantageously solve the above problem, is configured as follows.

[10] A method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet, including: a hot rolling step of obtaining a hot-rolled steel sheet by heating and hot-rolling a steel slab having a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities; a hot-rolled sheet annealing step of obtaining a hot-rolled annealed sheet by annealing the hot-rolled steel sheet; a brush grinding step of performing brush grinding on the hot-rolled annealed sheet; and a pickling step of pickling the hot-rolled annealed sheet that has been subjected to brush grinding, wherein in the hot rolling step, a heating temperature of the steel slab is set to 1150°C or lower, a finishing rolling temperature is set to 960°C or lower, and a coiling temperature is set to 700°C or lower; in the hot-rolled sheet annealing step, an annealing temperature is set to 800 to 1100°C; in the pickling step, the steel sheet that has been subjected to brush grinding is pickled at a hydrochloric acid concentration of 5% or higher and a pickling temperature of 70°C or higher for a pickling time of 10 to 120 seconds.

[11] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to

[10] , wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080%, group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030%, and group D: B, totaling 0.0001 to 0.0020%.

[12] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to

[10] or

[11] , wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020% , group I: Co, totaling 0.001 to 0.100%, and group J: As, totaling 0.0005 to 0.020%.

[13] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of

[10] to

[12] , wherein before annealing the hot-rolled steel sheet, the hot-rolled steel sheet is subjected to rolling and / or stretch bending at an elongation rate of 0.1 to 10.0%.

[14] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of

[10] to

[13] , wherein after the pickling step, the front and back surfaces of the pickled steel sheet are subjected to brush grinding. Another method of the present invention for manufacturing a non-oriented electrical steel sheet, which is able to advantageously solve the above problem, is configured as follows.

[15] A method for manufacturing a non-oriented electrical steel sheet, including: obtaining a cold-rolled sheet with a final sheet thickness by subjecting the hot-rolled annealed sheet manufactured by the method according to any one of

[10] to

[14] to cold rolling once or twice or more with intermediate annealing being performed therebetween and obtaining a cold-rolled annealed sheet by performing cold-rolled sheet annealing on the cold-rolled sheet at a soaking temperature of 700 to 1100°C. Advantageous Effects of Invention

[0012] According to the present invention, there can be efficiently manufactured a non-oriented electrical steel sheet that is capable of suppressing steel sheet fracture during cold rolling and is superior in magnetic properties.Description of Embodiments

[0013] The inventors of the present invention diligently conducted a series of studies on the cause of sheet fracture during cold rolling. As a result, they obtained the following insight: in the case of the steel sheet of the present invention that contains large amount of Si and Al, other than iron oxides, oxides of Si and Al are also generated on the surface of the steel sheet when performing hot rolling or hot-rolled sheet annealing. Particularly, an Fe-Al-based scale is finely formed in the vicinity of the interface between the iron matrix and the oxide layer. Since such Fe-Al-based scale is hardly soluble in acid, it promotes the wear of a rolling roll for cold rolling if unable to be removed completely during the pickling step, thereby causing the steel sheet to fracture easily. In order to solve this problem, the inventors studied the mechanical and chemical conditions associated with scale removal and arrived at the present invention by figuring out conditions that are suitable for stably removing scales including an Fe-Al-based scale.

[0014] Described hereunder is a hot-rolled annealed sheet of the present embodiment that is used for manufacturing a non-oriented electrical steel sheet.

[0015] In the beginning, explained are the chemical composition of the hot-rolled annealed sheet of this embodiment that is used to manufacture a non-oriented electrical steel sheet; and reasons why this chemical composition is limited as such. In the description below, the notation "%" means "mass%" unless otherwise noted.<Hot-rolled annealed sheet for non-oriented electrical steel sheet>

[0016] The hot-rolled annealed sheet of this embodiment that is used for manufacturing a non-oriented electrical steel sheet has a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, and one or more of Sn and Sb: 0.01 to 0.20% in total. This chemical composition further contains a balance consisting of Fe and unavoidable impurities.C: 0.0050% or less

[0017] C is an element that impairs iron loss properties after finishing annealing by forming carbides. Further, C induces sheet fracture during cold rolling by increasing the hardness of a hot-rolled annealed sheet. Thus, the C content is set to 0.0050% or less. A preferable C content is 0.0030% or less. While the lower limit of the C content is not specifically defined, it is preferred that C be contained in an amount of 0.0010% or more in terms of improving the toughness of a hot-rolled annealed sheet and preventing sheet fracture during cold rolling.Si: 2.0 to 5.0%

[0018] Si is contained in an amount of 2.0% or more since it has an effect of reducing iron loss after finishing annealing by improving the specific resistance of steel. Preferably, Si is contained in an amount of 2.7% or more. Meanwhile, the upper limit of the Si content is set to 5.0% since a Si content of greater than 5.0% causes a hot-rolled annealed sheet to harden and embrittle excessively such that fracture is more likely to occur during cold rolling. The Si content is preferably 4.5% or less.Mn: 0.2 to 2.0%

[0019] As is the case with Si, Mn is a beneficial element in terms of reducing iron loss. Further, since Mn has an effect of suppressing sheet fracture during cold rolling by improving the toughness of the iron matrix, the Mn content is set to 0.2% or more. Preferably, the Mn content is 0.35% or more. Meanwhile, Mn is to be contained in an amount of 2.0% or less, since a Mn content exceeding 2.0% increases the likelihood of fracture during cold rolling due to excessive hardening of the hot-rolled annealed sheet..P: 0.030% or less

[0020] P can be used to adjust strength as it has an effect of improving the strength of steel. Meanwhile, a P content exceeding 0.030% will cause steel to embrittle and thus incur productivity decline. Therefore, the P content is set to 0.030% or less. A preferable P content is 0.015% or less in terms of embrittlement prevention. Here, while the lower limit of the P content is not specifically defined, the lower limit thereof is preferably about 0.004% from the perspective of alleviating dephosphorization burden.S: 0.0050% or less

[0021] S embrittles a hot-rolled annealed sheet when segregated in the crystal grain boundary, making a steel sheet prone to fracture easily during cold rolling. Furthermore, S forms fine sulfides, which deteriorate iron loss properties after finishing annealing. In this regard, the upper limit of the S content is set to 0.0050%. A preferable S content is 0.0025% or less. Here, while the lower limit of the S content is not specifically defined, the lower limit thereof is preferably set to about 0.001% form the perspective of alleviating desulfurization burden.Al: 0.25 to 2.50%

[0022] As is the case with Si, Al has an effect of reducing iron loss after finishing annealing by improving the specific resistance of a steel sheet. Therefore, the Al content is set to 0.25% or more. Further, Al has an effect of improving a fracture resistance during cold rolling as a result of forming AlN and thereby reducing the average crystal grain size of a hot-rolled annealed sheet due to the pinning effect. For this reason, it is preferred that Al be contained in an amount of 0.50% or more. More preferably, Al is contained in an amount of 0.70% or more. Meanwhile, when the Al content exceeds 2.50%, a significant amount of Fe-Al-based oxides are generated in the scale produced during hot rolling and hot-rolled sheet annealing. These Fe-Al-based oxides cannot be completely removed in the pickling step, which may cause sheet fracture during cold rolling. Accordingly, the upper limit of the Al content is set to 2.50%. Preferably, Al is contained in an amount of 2.30% or less.N: 0.0050% or less

[0023] N forms nitrides, which may act as a start point for sheet fracture when performing cold rolling. Therefore, the upper limit of the N content is set to 0.0050%. Here, since fine nitrides hinder grain growth and thus impair iron loss properties after finishing annealing, a preferable N content is 0.0035% or less.O: 0.0050% or less

[0024] O forms oxides, which may act as a start point for sheet fracture when performing cold rolling. Therefore, the upper limit of the O content is 0.0050%. Further, since the oxides formed hinder the grain growth of the ferrite structure and thus impair iron loss properties after finishing annealing, a preferable O content is 0.0025% or less.Sn and Sb: one or more of Sn and Sb in a total amount of 0.01 to 0.20%

[0025] Other than the effect of improving magnetic properties by improving the texture after cold rolling and finishing annealing, Sn and Sb also have an effect of enhancing the fracture resistance during cold rolling by suppressing the generation of Fe-Al-based oxides via surface segregation. Thus, the Sn and Sb content is such that one or more of Sn and Sb are contained in an amount of 0.01% or more in total. Preferably, one or more of Sn and Sb are contained in an amount of 0.02% or more in total. Meanwhile, the upper limit of the total content of Sn and Sb is set to 0.20%, because excessive addition not only causes the effects brought about to saturate, but also deteriorates the toughness of a hot-rolled annealed sheet , making it more prone to fracture during cold rolling.

[0026] The components described above are the basic components of the hot-rolled annealed sheet of this embodiment used for manufacturing a non-oriented electrical steel sheet; in order to improve various properties, it is preferred that the hot-rolled annealed sheet of this embodiment further contain at least one group of components that is selected from the following groups A to D.Group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080%

[0027] Ca, Mg, and REM contribute to improving iron loss properties by fixing S as sulfides. Thus, it is preferred that one or more of Ca, Mg, and REM are contained in an amount of 0.0010% or more in total. More preferably, one or more of Ca, Mg, and REM are contained in an amount of 0.0020% or more in total. Meanwhile, when the Ca, Mg, and REM content exceeds 0.0080% in total, inclusions are formed excessively, leading to a decline in productivity. Thus, the upper limit of the Ca, Mg, and REM content is set to 0.0080%. A preferable total Ca, Mg, and REM content is 0.0060% or less.Group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%

[0028] Cr, Mo, Cu, and Ni contribute to improving iron loss properties by enhancing the specific resistance of steel. Thus, it is preferred that one or more of Cr, Mo, Cu, and Ni are contained in an amount of 0.01% or more in total. Meanwhile, if added excessively, a hot-rolled annealed sheet becomes hardened and more prone to fracture during cold rolling; the upper limit of the total content is preferably set to 0.40%.Group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030%

[0029] Ti, Nb, and V contribute to suppressing sheet fracture during cold rolling by improving the toughness of a hot-rolled annealed sheet through structural refinement. Therefore, the Ti, Nb, and V content is preferably set to 0.0005% or more in total. Meanwhile, if added excessively, a large amount of fine precipitates are generated so as to significantly hinder grain growth, which is why the upper limit of the total content of Ti, Nb, and V is preferably set to 0.0030%.Group D: B: 0.0001 to 0.0020%

[0030] B contributes to suppressing sheet fracture during cold rolling by improving the toughness of the sheet through segregation in the grain boundary. Thus, the B content is preferably set to 0.0001% or more. More preferably, the B content is set to 0.0003% or more. Meanwhile, the upper limit of the B content is preferably set to 0.0020%, as a B content exceeding 0.0020% results in the formation of iron borides, which diminish the toughness-improving effect.

[0031] Moreover, in order to improve various properties, it is preferred that the hot-rolled annealed sheet of this embodiment further contain at least one group of components that is selected from the following groups E to J.Group E: Zn: 0.001 to 0.010%

[0032] Zn has an effect of improving the iron loss properties of a finishing-annealed sheet by promoting grain growth when performing finishing annealing as a result of coarsening inclusions. Thus, the Zn content is preferably set to 0.001% or more. Meanwhile, a Zn content exceeding 0.010% leads to the saturation of the above effect, which is why the upper limit of the Zn content is preferably set to 0.010%.Group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%

[0033] Zr, Ta, W, and Se contribute to improving cold rollability by reducing the grain size of a hot-rolled annealed sheet through precipitate formation. Thus, it is preferred that one or more selected from Zr, Ta, W, and Se be contained in an amount of 0.001% or more in total. Meanwhile, the upper limit is preferably set to 0.010%, because a total content of greater than 0.010% may deteriorate the iron loss properties of a finishing-annealed sheet.Group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%

[0034] Ga and Ge enhance magnetic properties by improving the texture of a finishing-annealed sheet. Therefore, it is preferred that one or more selected from Ga and Ge be contained in an amount of 0.0001% or more in total. Meanwhile, the upper limit is preferably set to 0.0200%, because a content exceeding 0.0200% saturates the above effect.Group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020%

[0035] Pb and Bi contribute to improving cold rollability by reducing the grain size of a hot-rolled annealed sheet. Thus, it is preferred that one or more selected from Pb and Bi be contained in an amount of 0.00005% or more in total. Meanwhile, the upper limit is preferably set to 0.0020%, as the content exceeding 0.0020% deteriorates the iron loss properties of a finishing-annealed sheet.Group I: Co: 0.001 to 0.100%

[0036] Co contributes to improving magnetic flux density. Therefore, it is preferred that Co be contained in an amount of 0.001% or more. Meanwhile, the upper limit is preferably set to 0.100%, as the content exceeding 0.100% forms precipitates, which deteriorate the iron loss properties of a finishing-annealed sheet.Group J: As: 0.0005 to 0.020%

[0037] As contributes to improving cold rollability by reducing the grain size of a hot-rolled annealed sheet as a result of being segregated in the grain boundary. Thus, it is preferred that As be contained in an amount of 0.0005% or more. Meanwhile, the upper limit is preferably set to 0.020%, as the content exceeding0.020% rather impairs cold rollability as grain boundary fracture is facilitated.

[0038] As for the chemical composition of the hot-rolled annealed sheet of this embodiment that is used for manufacturing a non-oriented electrical steel sheet, the balance thereof other than the abovementioned elements is Fe and unavoidable impurities.<Steel structure of hot-rolled annealed sheet for non-oriented electrical steel sheet>

[0039] Next, described is a steel structure of the hot-rolled annealed sheet of this embodiment that is used for manufacturing a non-oriented electrical steel sheet. Average crystal grain size on cross-sectional surface of steel sheet in rolling direction: 40 to 250 µm

[0040] The average crystal grain size is set to 250 µm or smaller, because when the structure of a hot-rolled annealed sheet is coarse, the hot-rolled annealed sheet will embrittle whereby sheet fracture is more likely to occur during cold rolling. In terms of fracture suppression, the average crystal grain size is preferably 180 µm or smaller, more preferably 120 µm or smaller.

[0041] Meanwhile, the average crystal grain size needs to be 40 µm or larger, because if the average crystal grain size is smaller than 40 µm, there will be an increase in load during cold rolling as the hot-rolled annealed sheet hardens, and sheet fracture is more prone to occur accordingly. A preferable average crystal grain size is 60 µm or larger.Integrated intensity of Fe-Al-based oxide on steel sheet surface layer: 200 cps·deg or lower

[0042] An Fe-Al-based oxide is hard and has a poor wettability with respect to a lubricant. Thus, if such oxide remains on the steel sheet surface, the rolling roll will be damaged during cold rolling such that the friction coefficient and rolling load will increase, and rolling will become unstable accordingly, which will then lead to sheet fracture. For this reason, Fe-Al-based oxides need to be sufficiently eliminated in the pickling step; as an index, an integrated intensity of the Fe-Al-based oxide(s) on the steel sheet surface layer, which is obtained by subjecting a pickled hot-rolled annealed sheet to X-ray diffraction measurement, needs to be 200 cps·deg or lower.<Method for manufacturing hot-rolled annealed sheet for non-oriented electrical steel sheet>

[0043] Next, described is a method for manufacturing the hot-rolled annealed sheet of this embodiment that is used for manufacturing a non-oriented electrical steel sheet.

[0044] The method for manufacturing the hot-rolled annealed sheet of this embodiment that is used to manufacture a non-oriented electrical steel sheet includes a hot rolling step of obtaining a hot-rolled steel sheet by heating and hot-rolling a steel slab having the above chemical composition; a hot-rolled sheet annealing step of obtaining a hot-rolled annealed sheet by annealing the hot-rolled steel sheet; a shot blasting step of performing shot blasting on the hot-rolled annealed sheet; and a pickling step of pickling the hot-rolled annealed sheet that has been shot-blasted. In the hot rolling step, a heating temperature of the steel slab is set to 1150°C or lower, a finishing rolling temperature is set to 960°C or lower, and a coiling temperature is set to 700°C or lower. In the hot-rolled sheet annealing step, an annealing temperature is set to 800 to 1100°C; in the shot blasting step, shot blasting is performed on the hot-rolled annealed sheet at a projection density of 10 to 40 kg / m 2< . Next, in the pickling step, the shot-blasted steel sheet is pickled at a hydrochloric acid concentration of 5% or higher and a pickling temperature of 70°C or higher for a pickling time of 10 to 120 seconds. The details are shown below.[Hot rolling step]Steel slab

[0045] The chemical composition of the steel slab used to manufacture the hot-rolled annealed sheet of this embodiment that is employed for manufacturing a non-oriented electrical steel sheet is adjusted to the range(s) described above. The method for manufacturing such a steel is not particularly limited, and there may be used known refining processes such as those employing a converter, an electric furnace, and a vacuum degassing apparatus. Further, the method for manufacturing the steel slab is preferably a continuous casting process. Furthermore, as a raw material, there may be used iron scrap and direct reduced iron. Particularly, it is preferable to use iron scrap because elements useful for reducing iron loss, such as Cu and Ni, can be incorporated therefrom in an inexpensive manner.Heating temperature: 1150°C or lower

[0046] Hot rolling is a step where the steel slab having the above components is either hot-rolled immediately after its manufacturing or hot-rolled after it was cooled and then heated to a given temperature, thereby obtaining a hot-rolled sheet with a given sheet thickness. The upper limit of the heating temperature of the slab is set to 1150°C, because if the heating temperature is excessively high, AlN and MnS will remelt such that they will be finely precipitated in and beyond the hot rolling step to impair the grain growth property and iron loss. In order to improve the grain growth property and iron loss by coarsening AlN and MnS in the steel slab, the heating temperature is preferably set to 1000°C or higher. Further, a heating temperature of 1050°C or higher is more preferable in terms of realizing stable manufacturing by reducing the load in hot rolling.Finishing rolling temperature: 960°C or lower

[0047] The finishing rolling temperature in hot rolling is set to 960°C or lower, because a finishing rolling temperature exceeding 960°C will lead to a thick scale of the hot-rolled sheet and an impaired pickling property accordingly. A preferable finishing rolling temperature is 920°C or lower. Meanwhile, the lower limit of the finishing rolling temperature is preferably 750°C, because an excessively low finishing rolling temperature will lead to an increased mill load, i.e., an increased rolling load. More preferably, the finishing rolling temperature is 780°C or higher.Coiling temperature: 700°C or lower

[0048] The upper limit of the coiling temperature is set to 700°C, because a coiling temperature exceeding 700°C will lead to a larger volume of scale, particularly a thicker Fe-Al-based oxide(s), which will then result in an impaired pickling property. The coiling temperature is preferably 620°C or lower. Meanwhile, the lower limit of the coiling temperature is preferably set to 450°C, because an excessively low coiling temperature will result in large variations in temperature due to rapid cooling that takes place from completing hot rolling to performing coiling. A preferable coiling temperature is 480°C or higher in terms of reducing iron loss by coarsening precipitates during coiling.[Hot-rolled sheet annealing step]Hot-rolled sheet annealing temperature: 800 to 1100°C

[0049] Hot-rolled sheet annealing is performed to improve the magnetic properties after cold rolling and finishing annealing while improving the fracture resistance during cold rolling, by uniformizing the structure and controlling the ferrite grain size to a given range.

[0050] A hot-rolled sheet annealing temperature needs to be 1100°C or lower, because a hot-rolled sheet annealing temperature of higher than 1100°C will lead to an excessively coarsened structure and thus an impaired toughness, whereby sheet fracture is more likely to occur during cold rolling. A preferable hot-rolled sheet annealing temperature is 1030°C or lower. Moreover, the hot-rolled sheet annealing temperature is preferably set to 960°C or lower in terms of suppressing scale growth at the time of performing hot-rolled sheet annealing.

[0051] Meanwhile, the hot-rolled sheet annealing temperature needs to be 800°C or higher, because a hot-rolled sheet annealing temperature of lower than 800°C will result in an insufficiently grown grain size such that the magnetic properties after finishing annealing will deteriorate. A preferable hot-rolled sheet annealing temperature is 900°C or higher. While an annealing time is not specifically defined, it is preferably 10 seconds or longer in terms of securing uniformity.[Shot blasting step]Projection density for shot blasting: 10 to 40 kg / m 2<

[0052] By performing shot blasting on a hot-rolled annealed sheet that has yet to be pickled and thus introducing cracks into the scale, scale removal during pickling can be facilitated. Particularly, since an Fe-Al-based scale is hardly soluble in acids, an iron matrix portion that has been exposed by introducing cracks needs to be infiltrated with an acid so as to dissolve and remove the scale from the iron matrix side of the iron matrix interface. Thus, a projection density for shot blasting that is required for such purpose is 10 kg / m 2< or higher. Preferably, the projection density is 15 kg / m 2< or higher.

[0053] Meanwhile, the projection density is set to 40 kg / m 2< or lower, because a projection density of greater than 40 kg / m 2< will cause the neighboring region of the surface layer of the iron matrix to deform as well other than introducing cracks into the scale, thereby forming a start point for sheet fracture during cold rolling. A preferable projection density is 35 kg / m 2< or lower.

[0054] An average particle size of shot blasting particles is preferably 0.50 mm or smaller, because if the particle size of the shot blasting particles is large, the number of the particles colliding per unit area will decrease even at the same projection density, i.e., the number of the cracks introduced into the scale will decrease so that pickling property will be impaired. More preferably, the average particle size of the shot blasting particles is 0.30 mm or smaller in terms of promoting pickling property. Meanwhile, the average particle size of the shot blasting particles is preferably 0.15 mm or larger as an extremely small particle size will result in a diminished crack introduction effect. The average particle size of the shot blasting particles may, for example, be measured by the particle size analysis-laser diffraction methods that are described in JIS Z 8825:2013. Further, the Vickers hardness of the shot blasting particles is preferably 400 HV or higher, because if the shot blasting particles are soft, the shot blasting particles themselves will deform when colliding with the steel sheet, which makes it impossible to efficiently introduce cracks into the scale.[Brush grinding step (before pickling)]

[0055] Instead of performing shot blasting, cracks can be likewise introduced into the scale by carrying out brush grinding on a hot-rolled annealed sheet that has yet to be pickled, which will then facilitate scale removal during pickling.

[0056] It is preferred that a brush roll be used for brush grinding so that the surface of a steel sheet can be ground evenly. The material of the brush and grinding conditions may be appropriately selected; however, soft chemical fibers rather than metals are preferred for the bristle material of the brush in terms of conforming with the shape of a steel sheet and thus allowing for even grinding. Further, in terms of efficiently introducing cracks in the scale, it is preferred that the brush contain, for example, alumina-based, silicon carbide-based and / or diamond abrasive grains. It is also preferred that a cooling water be sprayed when performing brush grinding such that the grinding powder can be removed, and that overheating of the brush can be prevented as well.[Pickling step]Pickling: hydrochloric acid concentration 5% or higher, pickling temperature 70°C or higher, pickling time 10 to 120 seconds

[0057] The pickling step is a step of removing the scale of a hot-rolled annealed sheet that has already been subjected to the above shot blasting or brush grinding, where an Fe-Al-based scale in addition to iron oxides can be removed sufficiently so that sheet fracture during cold rolling can be suppressed. Thus, the hydrochloric acid concentration is set to 5% or higher. Preferably, the hydrochloric acid concentration is 8% or higher. While the upper limit of the hydrochloric acid concentration is not specifically defined, the hydrochloric acid concentration is preferably set to 20% or lower because overpickling may occur. In order to facilitate pickling, the temperature of a pickling solution (pickling temperature) is set to 70°C or higher. The pickling temperature is preferably 75°C or higher. It is preferred that the pickling temperature be set to 96°C or lower, because an excessively high pickling temperature will make overpickling more likely to occur and result in a higher manufacturing cost due to an increase in the amount of evaporation of the pickling solution. The pickling time is set to 10 seconds or longer for the sake of sufficient pickling. Preferably, the pickling time is 15 seconds or longer. The upper limit of the pickling time is set to 120 seconds, because a pickling time of greater than 120 seconds will lead to an increase in the amount of hydrogen generated such that hydrogen embrittlement will occur, which will then cause fracture easily during cold rolling. As described above, since pickling property varies depending on the Al content, the hot rolling finishing temperature, and the coiling temperature, a pickling accelerator and a pickling inhibitor may be appropriately added to the pickling solution as needed for adjustment purpose.

[0058] Further, in the present invention, from the perspective of completely removing an Fe-Al-based scale, it is preferred that the following step be further carried out in addition to the abovementioned scale removing step.Rolling and / or stretch bending step performed at elongation rate of 0.1 to 10.0% before hot-rolled sheet annealing step

[0059] Oxidation behavior during hot-rolled sheet annealing changes by exposing the iron matrix as the result of introducing cracks into the scale at the time when the steel sheet is still a hot-rolled sheet, particularly an Fe-Al-based scale. That is, since iron oxides that are relatively easily soluble in acid will be generated in parts where the iron matrix is exposed, the iron oxides of these parts will dissolve when performing pickling, followed by turning into a start point for iron matrix dissolution, whereby an Fe-Al-based scale can be removed as the iron matrix dissolves.

[0060] Thus, it is preferred that a hot-rolled sheet be elongated via light rolling and / or stretch bending. It is preferred that a skin pass rolling mill or a tension leveler be used to process a hot-rolled sheet that has yet to be subjected to hot-rolled sheet annealing at an elongation rate of 0.1% or larger. Preferably, the elongation rate is 0.3% or larger. The elongation rate is preferably set to 10.0% or smaller, because an elongation rate of greater than 10.0% will not only lead to the saturation of the above effect, but also result in an excessively large average crystal grain size of a hot-rolled annealed sheet due to strain-induced grain growth. An elongation rate of 6.0% or smaller is more preferable. Here, if performing rolling and / or stretch bending at an elongation rate of 0.1 to 10.0% before hot-rolled sheet annealing, it is preferred that the sheet be processed so that the integrated intensity of a pickled hot-rolled annealed sheet will be 150 cps·deg or lower.[Brush grinding step (after pickling)]

[0061] It is preferred that the Fe-Al-based scale that has partially remained at the time of performing pickling be mechanically removed by conducting brush grinding on the front and back surfaces of a pickled steel sheet. If performing brush grinding alone, a larger device is required, and there will be incurred a higher introduction cost and maintenance cost, in order to remove all scales including, for example, an Fe-based scale and an Fe-Al-based scale.

[0062] For this reason, device cost can be reduced by removing most of the scales via pickling and further removing only the partially remaining Fe-Al-based scale via brush grinding.

[0063] It is preferred that a brush roll be used to perform brush grinding in order to evenly grind the surface(s) of a steel sheet.

[0064] The material of the brush and grinding conditions may be appropriately selected; however, soft chemical fibers rather than metals are preferred for the bristle material of the brush in terms of conforming with the sheet shape of a steel sheet and thus being able to perform grinding evenly. Further, in terms of efficiently removing the Fe-Al-based scale, it is preferred that the brush contain, for example, alumina-based, silicon carbide-based and / or diamond abrasive grains. It is also preferred that a cooling water be sprayed when performing brush grinding such that the grinding powder can be removed, and that overheating of the brush can be prevented.

[0065] Here, if performing brush grinding on the front and back surfaces of a steel sheet after carrying out pickling, it is preferred that brush grinding be performed so that the integrated intensity of a hot-rolled annealed sheet that has been subjected to brush grinding will be 60 cps·deg or lower.

[0066] Next, described is a method for manufacturing a non-oriented electrical steel sheet from the hot-rolled annealed sheet that is obtained by the above manufacturing method of the present invention.[Cold rolling step]

[0067] It is preferred that the pickled hot-rolled annealed sheet be turned into a cold-rolled sheet with a final sheet thickness by being subjected to cold rolling once or twice or more with intermediate annealing being performed therebetween. From the perspective of production efficiency, while it is preferable to use a tandem rolling mill, a reversing rolling mill may also be used, and rolling may be performed by a common procedure.[Finishing annealing step]Finishing annealing temperature: 700 to 1100°C

[0068] A finishing annealing step after the above cold rolling is a step of achieving favorable magnetic properties via recrystallization and grain growth of the cold-rolled sheet. A soaking temperature in the above finishing annealing is preferably set to 700°C or higher. A soaking temperature of 800°C or higher is more preferable. Meanwhile, the soaking temperature is preferably set to 1100°C or lower, because an excessively high soaking temperature in finishing annealing may cause nitriding to occur during annealing and lead to a deteriorated iron loss due to overly coarsened crystal grains. More preferably, the soaking temperature is set to 1050°C or lower.Examples

[0069] The embodiment of the present invention is further described based on working examples. Here, the present invention shall not be limited to the manufacturing conditions and product performance that are shown in the following working examples. Desired performance is able to be achieved when the embodiment is within the scope of the present invention.(Example 1)

[0070] A steel having a chemical composition composed of the various components shown in Table 1 and a balance consisting of Fe and unavoidable impurities was manufactured by a common refining process, followed by turning this steel into a slab via a continuous casting method. Next, under the conditions shown in Tables 2-1 and 2-2, the above slab was heated in a gas furnace and then subjected to hot rolling composed of rough rolling and finishing rolling so as to be turned into a hot-rolled sheet having a sheet thickness of 1.8 mm and a sheet width of 1200 mm. Later, the hot-rolled sheet was subjected to hot-rolled sheet annealing before being pickled, thereby obtaining a hot-rolled annealed sheet. There, several hot-rolled sheets were subjected to one or both of light rolling that is performed before hot-rolled sheet annealing with a skin pass rolling mill; and brush grinding that is performed after pickling. Brush grinding was performed in such a way that there was employed a silicon carbide-based brush roll using silicon carbide-based abrasive grains, in which nylon was used as the bristle material. Listed in Tables 2-1 and 2-2 are the elongation rate (%) for light rolling before hot-rolled sheet annealing, and the torque (N·m) and rotation number (rpm) when performing grinding with the brush roll after pickling.Steel sheet structure

[0071] A sample was cut out from the hot-rolled annealed sheet obtained so that a sheet thickness cross-section in the rolling direction could be observed, followed by mounting, polishing, and then etching the sample so as to reveal the structure thereof, thus making it possible to observe the structure of the steel sheet. An average crystal grain size was calculated via image analysis from a photograph taken of the structure. Here, the average grain size was a circle-equivalent diameter.Integrated intensity of oxide

[0072] A sample of a size of sheet thickness × 25 × 30 mm was cut out from the hot-rolled annealed sheet obtained, and a remaining amount of the scale was measured via X-ray diffraction with respect to the surface of the steel sheet. The X-ray diffraction measurement was carried out with an incident angle of 1°, where an integrated intensity was calculated for a diffraction peak appearing at 2θ of about 36.4°, the diffraction peak corresponding to the (311) reflection of a Fe-Al-based oxide (hercynite, FeAl 2 O 4 ).Fracture resistance during cold rolling

[0073] A tandem cold rolling mill was used to roll the hot-rolled annealed sheet obtained by 8000 m in total with a final thickness being set to 0.25 mm and a threading speed at the outlet side of the final stand being set to 600 m / min except for the unsteady part in the vicinity of the welded portion. Specifically, examples exhibiting fracture once or more were evaluated as "Poor", examples exhibiting no fracture were evaluated as "Good", and examples exhibiting no fracture and a small load fluctuation in the first stand were evaluated as "Excellent".

[0074] Here, the notion of a small load fluctuation shall be understood as follows. That is, provided that L ave represents an average value of the #1 std rolling load at the time of performing rolling at 600 m / min by a tandem rolling mill, and that ΔL represents a difference between the maximum and minimum values of the above rolling load, a small load fluctuation refers to a condition where a ratio ΔL / L ave , which is a ratio between the average value L ave of the above rolling load and the difference ΔL between the maximum and minimum values of the above rolling load, is 10% or smaller when multiplied by 100.Iron loss W 10 / 400 of finishing-annealed sheet

[0075] The above cold-rolled sheet was subjected to finishing annealing under the conditions shown in Tables 2-1 and 2-2. The soaking temperature was set to 10 seconds. Test pieces each having a size of width 30 mm × length 280 mm were then collected from the obtained finishing-annealed sheet along a L direction (rolling direction) and a C direction (direction orthogonal to rolling direction), followed by measuring the iron loss W 10 / 400 of these test pieces in accordance with JIS C2550-1.

[0076] The above measurement results are shown in Tables 2-1 and 2-2. These results indicate that by controlling the manufacturing conditions of a steel sheet to the scope of the present invention, there can be obtained such a hot-rolled annealed sheet for a non-oriented electrical steel sheet that this hot-rolled annealed sheet is capable of realizing both fracture prevention during cold rolling after performing hot-rolled sheet annealing and excellent magnetic properties after performing cold-rolled sheet annealing. [Table 1]Steel No.Chemical component (mass%)RemarksCSiMnPSAlNOSnSbOthers10.00213.40.500.0130.00210.500.00120.00110.02--Invention Example20.00183.20.300.0090.00250.250.00150.00100.02--Invention Example30.00123.00.400.0150.00310.700.00080.0013-0.03-Invention Example40.00263.41.500.0120.00120.700.00230.00150.02--Invention Example50.00103.80.500.0060.00061.400.00210.00220.020.03-Invention Example60.00463.50.400.0150.00160.900.00190.00080.01--Invention Example70.00312.80.500.0120.00181.200.00100.00250.050.05-Invention Example80.00242.80.350.0090.00232.100.00290.0012-0.01-Invention Example90.00262.60.600.0120.00072.500.00240.00120.06--Invention Example100.00253.00.200.0200.00131.200.00190.0026-0.20-Invention Example110.00383.20.500.0140.00162.610.00150.00170.02--Comparative Example120.00263.00.500.0130.00150.200.00130.00240.02--Comparative Example130.00243.40.500.0130.00220.500.00150.0013---Comparative Example140.00323.20.600.0040.00090.500.00170.00110.030.0030CaInvention Example150.00263.20.500.0130.00110.500.00170.0009-0.020.0024MgInvention Example160.00203.21.800.0150.00180.700.00160.00130.04-0.0026REMInvention Example170.00143.40.500.0080.00160.700.00110.00130.02-0.02CrInvention Example180.00183.40.500.0150.00140.700.00170.00080.02-0.01MoInvention Example190.00173.70.700.0120.00110.500.00220.0014-0.020.20CuInvention Example200.00223.40.700.0090.00130.500.00230.00080.010.010.15NiInvention Example210.00253.40.700.0070.00211.200.00240.00210.02-0.4Cu, 0.2NiInvention Example220.00113.52.000.0140.00221.500.00140.00110.020.020.0015TiInvention Example230.00263.50.800.0060.00081.400.00170.00170.02-0.0005NbInvention Example240.00243.70.500.0110.00242.000.00110.00130.02-0.003VInvention Example250.00223.50.700.0050.00211.400.00130.00140.02-0.0005BInvention Example260.00173.60.700.0080.00240.900.00200.00130.02-0.02Mo, 0.0003BInvention Example270.00533.20.500.0100.00180.400.00190.00210.02--Comparative Example280.00212.00.550.0110.00150.500.00230.00220.02--Invention Example290.00135.00.600.0040.00140.350.00230.00140.02--Invention Example300.00201.90.600.0130.00210.700.00150.00150.03--Comparative Example310.00165.10.300.0090.00160.700.00130.00190.03--Comparative Example320.00183.40.140.0080.00230.700.00090.00090.03--Comparative Example330.00223.02.140.0200.00240.850.00240.00160.03--Comparative Example340.00262.40.400.0330.00310.750.00260.00120.01--Comparative Example350.00172.80.500.0160.00460.550.00220.00140.04--Invention Example360.00133.20.350.0150.00530.800.00170.00260.02--Comparative Example370.00223.80.300.0080.00210.550.00460.00220.02--Invention Example380.00183.80.400.0080.00230.700.00540.00180.02--Comparative Example390.00163.50.400.0090.00140.650.00210.00430.02--Invention Example400.00153.50.500.0090.00150.500.00230.00590.02--Comparative Example410.00223.40.550.0110.00140.800.00260.00100.04-0.005ZnInvention Example420.00153.40.550.0120.00120.800.00230.00120.04-0.006ZrInvention Example430.00163.40.550.0120.00120.800.00220.00120.04-0.002TaInvention Example440.00203.60.400.0120.00120.500.00180.00140.04-0.006WInvention Example450.00163.60.400.0090.00080.500.00180.00160.04-0.003SeInvention Example460.00183.60.400.0080.00100.600.00150.00170.04-0.003GaInvention Example470.00163.20.600.0080.00101.200.00140.00200.04-0.015GeInvention Example480.00213.20.600.0080.00131.200.00220.00160.04-0.0006PbInvention Example490.00243.20.600.0140.00151.200.00210.00150.02-0.0010B1Invention Example500.00223.20.500.0140.00151.200.00180.00130.02-0.080CoInvention Example510.00183.50.600.0120.00120.750.00230.00220.02-0.006AsInvention Example520.00233.50.600.0100.00120.750.00210.00260.02-0.0008Pb,Invention Example530.00183.50.500.0100.00170.750.00140.00150.02-0.15Cu, 0.004AsInvention Example540.00263.50.500.0100.00150.750.00130.00170.02-0.003Zn, 0.042CoInvention Example (Example 2)

[0077] Under the conditions shown in Tables 3-1 and 3-2, the slab that has been manufactured in the working example 1 and has the chemical composition composed of the various components shown in Table 1 and the balance consisting of Fe and unavoidable impurities was heated in a gas furnace and then subjected to hot rolling composed of rough rolling and finishing rolling so as to be turned into a hot-rolled sheet having a sheet thickness of 1.8 mm and a sheet width of 1200 mm. Later, the hot-rolled sheet was subjected to hot-rolled sheet annealing before being subjected to brush grinding and pickling, thereby obtaining a hot-rolled annealed sheet. There, several hot-rolled sheets were subjected to one or both of light rolling that is performed before hot-rolled sheet annealing with a skin pass rolling mill; and brush grinding that is performed after pickling. Brush grinding was performed in such a way that there was employed a silicon carbide-based brush roll using silicon carbide-based abrasive grains, in which nylon was used as the bristle material. Listed in Tables 3-1 and 3-2 are the elongation rate (%) for light rolling before hot-rolled sheet annealing, the torque (N·m) and rotation number (rpm) when performing grinding with the brush roll before pickling, and the torque (N·m) and rotation number (rpm) when performing grinding with the brush roll after pickling.Steel sheet structure

[0078] A sample was cut out from the hot-rolled annealed sheet obtained so that a sheet thickness cross-section in the rolling direction could be observed, followed by mounting, polishing, and then etching the sample so as to reveal the structure thereof, thus making it possible to observe the structure of the steel sheet. An average crystal grain size was calculated via image analysis from a photograph taken of the structure. Here, the average grain size was a circle-equivalent diameter.Integrated intensity of oxide

[0079] A sample of a size of sheet thickness × 25 × 30 mm was cut out from the hot-rolled annealed sheet obtained, and a remaining amount of the scale was measured via X-ray diffraction with respect to the surface of the steel sheet. The X-ray diffraction measurement was carried out with an incident angle of 1°, where an integrated intensity was calculated for a diffraction peak appearing at 2θ of about 36.4°, the diffraction peak corresponding to the (311) reflection of a Fe-Al-based oxide (hercynite, FeAl 2 O 4 ).Fracture resistance during cold rolling

[0080] A tandem cold rolling mill was used to roll the hot-rolled annealed sheet obtained by 8000 m in total with a final thickness being set to 0.25 mm and a threading speed at the outlet side of the final stand being set to 600 m / min except for the unsteady part in the vicinity of the welded portion. Specifically, examples exhibiting fracture once or more were evaluated as "Poor", examples exhibiting no fracture were evaluated as "Good", and examples exhibiting no fracture and a small load fluctuation in the first stand were evaluated as "Excellent".

[0081] Here, the notion of a small load fluctuation shall be understood as follows. That is, provided that L ave represents an average value of the #1 std rolling load at the time of performing rolling at 600 m / min by a tandem rolling mill, and that ΔL represents a difference between the maximum and minimum values of the above rolling load, a small load fluctuation refers to a condition where a ratio ΔL / L ave , which is a ratio between the average value L ave of the above rolling load and the difference ΔL between the maximum and minimum values of the above rolling load, is 10% or smaller when multiplied by 100.Iron loss W 10 / 400 of finishing-annealed sheet

[0082] The above cold-rolled sheet was subjected to finishing annealing under the conditions shown in Tables 3-1 and 3-2. The soaking temperature was set to 10 s. Test pieces each having a size of width 30 mm × length 280 mm were then collected from the obtained finishing-annealed sheet along a L direction (rolling direction) and a C direction (direction orthogonal to rolling direction), followed by measuring the iron loss W 10 / 400 of these test pieces in accordance with JIS C2550-1.

[0083] The above measurement results are shown in Tables 3-1 and 3-2. These results indicate that by controlling the manufacturing conditions of a steel sheet to the scope of the present invention, there can be obtained such a hot-rolled annealed sheet for a non-oriented electrical steel sheet that this hot-rolled annealed sheet is capable of realizing both fracture prevention during cold rolling after performing hot-rolled sheet annealing and excellent magnetic properties after performing cold-rolled sheet annealing.

Examples

example 1

(Example 1)

[0070]A steel having a chemical composition composed of the various components shown in Table 1 and a balance consisting of Fe and unavoidable impurities was manufactured by a common refining process, followed by turning this steel into a slab via a continuous casting method. Next, under the conditions shown in Tables 2-1 and 2-2, the above slab was heated in a gas furnace and then subjected to hot rolling composed of rough rolling and finishing rolling so as to be turned into a hot-rolled sheet having a sheet thickness of 1.8 mm and a sheet width of 1200 mm. Later, the hot-rolled sheet was subjected to hot-rolled sheet annealing before being pickled, thereby obtaining a hot-rolled annealed sheet. There, several hot-rolled sheets were subjected to one or both of light rolling that is performed before hot-rolled sheet annealing with a skin pass rolling mill; and brush grinding that is performed after pickling. Brush grinding was performed in such a way that there was emplo...

example 2

(Example 2)

[0077]Under the conditions shown in Tables 3-1 and 3-2, the slab that has been manufactured in the working example 1 and has the chemical composition composed of the various components shown in Table 1 and the balance consisting of Fe and unavoidable impurities was heated in a gas furnace and then subjected to hot rolling composed of rough rolling and finishing rolling so as to be turned into a hot-rolled sheet having a sheet thickness of 1.8 mm and a sheet width of 1200 mm. Later, the hot-rolled sheet was subjected to hot-rolled sheet annealing before being subjected to brush grinding and pickling, thereby obtaining a hot-rolled annealed sheet. There, several hot-rolled sheets were subjected to one or both of light rolling that is performed before hot-rolled sheet annealing with a skin pass rolling mill; and brush grinding that is performed after pickling. Brush grinding was performed in such a way that there was employed a silicon carbide-based brush roll using silicon ...

Technical Field

[0001] The present invention relates to a hot-rolled annealed sheet that is used for manufacturing a non-oriented electrical steel sheet and is superior in fracture resistance during cold rolling; a method for manufacturing such a hot-rolled annealed sheet; and a method for manufacturing a non-oriented electrical steel sheet, using such a hot-rolled annealed sheet.Background Art

[0002] In recent years, there have been stronger needs to reduce exhaust CO 2 emissions and save energy out of a higher awareness of environmental problems; even electric apparatuses such as electric vehicles are now strongly required to exhibit a higher efficiency. For this reason, non-oriented electrical steel sheets that are widely used as iron core materials for motors installed in electric apparatuses are also now strongly required to possess improved iron loss properties. Thus, attempts have been made to improve iron loss properties by, for example, adding large amounts of specific resistance-enhancing elements such as Si and Al, or reducing sheet thickness.

[0003] However, adding large amounts of Si, Al or the like and reducing final sheet thickness lead to a higher manufacturing load during cold rolling, which implies that in addition to improving magnetic properties, it is also critical to prevent troubles such as steel sheet fracture from happening during cold rolling.

[0004] Here, in order to solve this problem, there has been proposed a technique of, for example, suppressing sheet fracture during cold rolling by controlling a hot-rolled sheet annealing temperature and thus improving toughness.

[0005] For example, Patent Literature 1 discloses a non-oriented electrical steel sheet that contains, by mass%, C: 0.0010 to 0.0050%, Si: 2.5 to 4.0%, Al: 0.2 to 2.0%, Mn: 0.05 to 2.0%, P: 0.005 to 0.15%, S: 0.0001 to 0.0030%, Ti: 0.0005 to 0.0030%, N: 0.0010 to 0.0030%, and a balance consisting of Fe and unavoidable impurities, in which the sheet thickness of its iron matrix is 0.10 to 0.35 mm, and an Al concentration in a depth direction from the surface of the iron matrix is such that a relational expression shown by the following formula (1) is satisfied. According to Patent Literature 1, when a soaking temperature exceeds 1100°C in hot-rolled sheet annealing, or when a soaking time is longer than 300 sec, the iron matrix may fracture during cold rolling performed in a later stage. 0.1 ≤ A 1 x ≤ 2 μm / A 1 x = 10 μm < 1.0

[0006] Here, in the above formula (1), x represents a depth [µm] from the surface of the iron matrix, Al (x≤2 µm) represents an average value of Al concentrations from the surface of the iron matrix to a depth of 2 µm, and Al (x=10 µm) represents an Al concentration at a position of a depth of 10 µm.Citation ListPatent Literature

[0007] Patent Literature 1: JP-A-2018-021241Summary of InventionTechnical Problem

[0008] However, the conventional technique disclosed in the above patent literature has the following problem.

[0009] As a result of conducting a series of studies, the inventors of the present invention found that the controls on the hot-rolled sheet annealing condition that are described in Patent Literature 1 alone are not necessarily able to suppress the occurrence of fracture, and that it is difficult to realize both a fracture resistance during cold rolling and favorable magnetic properties after performing cold-rolled sheet annealing.

[0010] The present invention was made in view of such problem. It is an object of the present invention to provide a hot-rolled annealed sheet that is used for manufacturing a non-oriented electrical steel sheet and is superior in fracture prevention during cold rolling after performing hot-rolled sheet annealing and magnetic properties after performing cold-rolled sheet annealing; a method for manufacturing such hot-rolled annealed sheet; and a method for manufacturing a non-oriented electrical steel sheet, using such hot-rolled annealed sheet.Solution of Problem

[0011] The hot-rolled annealed sheet of the present invention that is used to manufacture a non-oriented electrical steel sheet and is able to advantageously solve the above problem, is configured as follows. [1] A hot-rolled annealed sheet for a non-oriented electrical steel sheet having a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities, wherein an average crystal grain size on a cross-sectional surface of the steel sheet in a rolling direction is 40 to 250 µm, and an integrated intensity of an Fe-Al-based oxide on a steel sheet surface layer is 200 cps·deg or lower when measured by X-ray diffraction. [2] The hot-rolled annealed sheet for a non-oriented electrical steel sheet according to [1], wherein, in addition to the chemical composition, the hot-rolled annealed sheet further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080%, group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030%, and group D: B, totaling 0.0001 to 0.0020%. [3] The hot-rolled annealed sheet for a non-oriented electrical steel sheet according to [1] or [2], wherein in addition to the chemical composition, the hot-rolled annealed sheet further contains, by mass%, at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020%, group I: Co, totaling 0.001 to 0.100% , and group J: As, totaling 0.0005 to 0.020%. The method of the present invention for manufacturing the hot-rolled annealed sheet that is used to manufacture a non-oriented electrical steel sheet, which is able to advantageously solve the above problem, is configured as follows. [4] A method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet, including: a hot rolling step of obtaining a hot-rolled steel sheet by heating and hot-rolling a steel slab having a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities; a hot-rolled sheet annealing step of obtaining a hot-rolled annealed sheet by annealing the hot-rolled steel sheet; a shot blasting step of performing shot blasting on the hot-rolled annealed sheet; and a pickling step of pickling the hot-rolled annealed sheet that has been shot-blasted, wherein: in the hot rolling step, a heating temperature of the steel slab is set to 1150°C or lower, a finishing rolling temperature is set to 960°C or lower, and a coiling temperature is set to 700°C or lower; in the hot-rolled sheet annealing step, an annealing temperature is set to 800 to 1100°C; in the shot blasting step, shot blasting is performed on the hot-rolled annealed sheet at a projection density of 10 to 40 kg / m 2< ; in the pickling step, the shot-blasted steel sheet is pickled at a hydrochloric acid concentration of 5% or higher and a pickling temperature of 70°C or higher for a pickling time of 10 to 120 seconds. [5] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to [4], wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080% , group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030% , and group D: B, totaling 0.0001 to 0.0020%. [6] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to [4] or [5], wherein in addition to the chemical composition, the steel slab further contains, by mass, at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020%, group I: Co, totaling 0.001 to 0.100%, and group J: As, totaling 0.0005 to 0.020%. [7] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of [4] to [6], wherein before annealing the hot-rolled steel sheet, the hot-rolled steel sheet is subjected to rolling and / or stretch bending at an elongation rate of 0.1 to 10.0%. [8] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of [4] to [7], wherein after the pickling step, both the front and back surfaces of the pickled steel sheet are subjected to brush grinding. The method of the present invention for manufacturing a non-oriented electrical steel sheet, which is able to advantageously solve the above problem, is configured as follows. [9] A method for manufacturing a non-oriented electrical steel sheet, including: obtaining a cold-rolled sheet with a final sheet thickness by subjecting the hot-rolled annealed sheet manufactured by the method according to any one of [4] to [8] to cold rolling once or twice or more with intermediate annealing being performed therebetween and obtaining a cold-rolled annealed sheet by performing cold-rolled sheet annealing on the cold-rolled sheet at a soaking temperature of 700 to 1100°C. Another method of the present invention for manufacturing a hot-rolled annealed sheet that is used to manufacture a non-oriented electrical steel sheet, which is able to advantageously solve the above problem, is configured as follows.

[10] A method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet, including: a hot rolling step of obtaining a hot-rolled steel sheet by heating and hot-rolling a steel slab having a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities; a hot-rolled sheet annealing step of obtaining a hot-rolled annealed sheet by annealing the hot-rolled steel sheet; a brush grinding step of performing brush grinding on the hot-rolled annealed sheet; and a pickling step of pickling the hot-rolled annealed sheet that has been subjected to brush grinding, wherein in the hot rolling step, a heating temperature of the steel slab is set to 1150°C or lower, a finishing rolling temperature is set to 960°C or lower, and a coiling temperature is set to 700°C or lower; in the hot-rolled sheet annealing step, an annealing temperature is set to 800 to 1100°C; in the pickling step, the steel sheet that has been subjected to brush grinding is pickled at a hydrochloric acid concentration of 5% or higher and a pickling temperature of 70°C or higher for a pickling time of 10 to 120 seconds.

[11] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to

[10] , wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080%, group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030%, and group D: B, totaling 0.0001 to 0.0020%.

[12] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to

[10] or

[11] , wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020% , group I: Co, totaling 0.001 to 0.100%, and group J: As, totaling 0.0005 to 0.020%.

[13] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of

[10] to

[12] , wherein before annealing the hot-rolled steel sheet, the hot-rolled steel sheet is subjected to rolling and / or stretch bending at an elongation rate of 0.1 to 10.0%.

[14] The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of

[10] to

[13] , wherein after the pickling step, the front and back surfaces of the pickled steel sheet are subjected to brush grinding. Another method of the present invention for manufacturing a non-oriented electrical steel sheet, which is able to advantageously solve the above problem, is configured as follows.

[15] A method for manufacturing a non-oriented electrical steel sheet, including: obtaining a cold-rolled sheet with a final sheet thickness by subjecting the hot-rolled annealed sheet manufactured by the method according to any one of

[10] to

[14] to cold rolling once or twice or more with intermediate annealing being performed therebetween and obtaining a cold-rolled annealed sheet by performing cold-rolled sheet annealing on the cold-rolled sheet at a soaking temperature of 700 to 1100°C. Advantageous Effects of Invention

[0012] According to the present invention, there can be efficiently manufactured a non-oriented electrical steel sheet that is capable of suppressing steel sheet fracture during cold rolling and is superior in magnetic properties.Description of Embodiments

[0013] The inventors of the present invention diligently conducted a series of studies on the cause of sheet fracture during cold rolling. As a result, they obtained the following insight: in the case of the steel sheet of the present invention that contains large amount of Si and Al, other than iron oxides, oxides of Si and Al are also generated on the surface of the steel sheet when performing hot rolling or hot-rolled sheet annealing. Particularly, an Fe-Al-based scale is finely formed in the vicinity of the interface between the iron matrix and the oxide layer. Since such Fe-Al-based scale is hardly soluble in acid, it promotes the wear of a rolling roll for cold rolling if unable to be removed completely during the pickling step, thereby causing the steel sheet to fracture easily. In order to solve this problem, the inventors studied the mechanical and chemical conditions associated with scale removal and arrived at the present invention by figuring out conditions that are suitable for stably removing scales including an Fe-Al-based scale.

[0014] Described hereunder is a hot-rolled annealed sheet of the present embodiment that is used for manufacturing a non-oriented electrical steel sheet.

[0015] In the beginning, explained are the chemical composition of the hot-rolled annealed sheet of this embodiment that is used to manufacture a non-oriented electrical steel sheet; and reasons why this chemical composition is limited as such. In the description below, the notation "%" means "mass%" unless otherwise noted.<Hot-rolled annealed sheet for non-oriented electrical steel sheet>

[0016] The hot-rolled annealed sheet of this embodiment that is used for manufacturing a non-oriented electrical steel sheet has a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, and one or more of Sn and Sb: 0.01 to 0.20% in total. This chemical composition further contains a balance consisting of Fe and unavoidable impurities.C: 0.0050% or less

[0017] C is an element that impairs iron loss properties after finishing annealing by forming carbides. Further, C induces sheet fracture during cold rolling by increasing the hardness of a hot-rolled annealed sheet. Thus, the C content is set to 0.0050% or less. A preferable C content is 0.0030% or less. While the lower limit of the C content is not specifically defined, it is preferred that C be contained in an amount of 0.0010% or more in terms of improving the toughness of a hot-rolled annealed sheet and preventing sheet fracture during cold rolling.Si: 2.0 to 5.0%

[0018] Si is contained in an amount of 2.0% or more since it has an effect of reducing iron loss after finishing annealing by improving the specific resistance of steel. Preferably, Si is contained in an amount of 2.7% or more. Meanwhile, the upper limit of the Si content is set to 5.0% since a Si content of greater than 5.0% causes a hot-rolled annealed sheet to harden and embrittle excessively such that fracture is more likely to occur during cold rolling. The Si content is preferably 4.5% or less.Mn: 0.2 to 2.0%

[0019] As is the case with Si, Mn is a beneficial element in terms of reducing iron loss. Further, since Mn has an effect of suppressing sheet fracture during cold rolling by improving the toughness of the iron matrix, the Mn content is set to 0.2% or more. Preferably, the Mn content is 0.35% or more. Meanwhile, Mn is to be contained in an amount of 2.0% or less, since a Mn content exceeding 2.0% increases the likelihood of fracture during cold rolling due to excessive hardening of the hot-rolled annealed sheet..P: 0.030% or less

[0020] P can be used to adjust strength as it has an effect of improving the strength of steel. Meanwhile, a P content exceeding 0.030% will cause steel to embrittle and thus incur productivity decline. Therefore, the P content is set to 0.030% or less. A preferable P content is 0.015% or less in terms of embrittlement prevention. Here, while the lower limit of the P content is not specifically defined, the lower limit thereof is preferably about 0.004% from the perspective of alleviating dephosphorization burden.S: 0.0050% or less

[0021] S embrittles a hot-rolled annealed sheet when segregated in the crystal grain boundary, making a steel sheet prone to fracture easily during cold rolling. Furthermore, S forms fine sulfides, which deteriorate iron loss properties after finishing annealing. In this regard, the upper limit of the S content is set to 0.0050%. A preferable S content is 0.0025% or less. Here, while the lower limit of the S content is not specifically defined, the lower limit thereof is preferably set to about 0.001% form the perspective of alleviating desulfurization burden.Al: 0.25 to 2.50%

[0022] As is the case with Si, Al has an effect of reducing iron loss after finishing annealing by improving the specific resistance of a steel sheet. Therefore, the Al content is set to 0.25% or more. Further, Al has an effect of improving a fracture resistance during cold rolling as a result of forming AlN and thereby reducing the average crystal grain size of a hot-rolled annealed sheet due to the pinning effect. For this reason, it is preferred that Al be contained in an amount of 0.50% or more. More preferably, Al is contained in an amount of 0.70% or more. Meanwhile, when the Al content exceeds 2.50%, a significant amount of Fe-Al-based oxides are generated in the scale produced during hot rolling and hot-rolled sheet annealing. These Fe-Al-based oxides cannot be completely removed in the pickling step, which may cause sheet fracture during cold rolling. Accordingly, the upper limit of the Al content is set to 2.50%. Preferably, Al is contained in an amount of 2.30% or less.N: 0.0050% or less

[0023] N forms nitrides, which may act as a start point for sheet fracture when performing cold rolling. Therefore, the upper limit of the N content is set to 0.0050%. Here, since fine nitrides hinder grain growth and thus impair iron loss properties after finishing annealing, a preferable N content is 0.0035% or less.O: 0.0050% or less

[0024] O forms oxides, which may act as a start point for sheet fracture when performing cold rolling. Therefore, the upper limit of the O content is 0.0050%. Further, since the oxides formed hinder the grain growth of the ferrite structure and thus impair iron loss properties after finishing annealing, a preferable O content is 0.0025% or less.Sn and Sb: one or more of Sn and Sb in a total amount of 0.01 to 0.20%

[0025] Other than the effect of improving magnetic properties by improving the texture after cold rolling and finishing annealing, Sn and Sb also have an effect of enhancing the fracture resistance during cold rolling by suppressing the generation of Fe-Al-based oxides via surface segregation. Thus, the Sn and Sb content is such that one or more of Sn and Sb are contained in an amount of 0.01% or more in total. Preferably, one or more of Sn and Sb are contained in an amount of 0.02% or more in total. Meanwhile, the upper limit of the total content of Sn and Sb is set to 0.20%, because excessive addition not only causes the effects brought about to saturate, but also deteriorates the toughness of a hot-rolled annealed sheet , making it more prone to fracture during cold rolling.

[0026] The components described above are the basic components of the hot-rolled annealed sheet of this embodiment used for manufacturing a non-oriented electrical steel sheet; in order to improve various properties, it is preferred that the hot-rolled annealed sheet of this embodiment further contain at least one group of components that is selected from the following groups A to D.Group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080%

[0027] Ca, Mg, and REM contribute to improving iron loss properties by fixing S as sulfides. Thus, it is preferred that one or more of Ca, Mg, and REM are contained in an amount of 0.0010% or more in total. More preferably, one or more of Ca, Mg, and REM are contained in an amount of 0.0020% or more in total. Meanwhile, when the Ca, Mg, and REM content exceeds 0.0080% in total, inclusions are formed excessively, leading to a decline in productivity. Thus, the upper limit of the Ca, Mg, and REM content is set to 0.0080%. A preferable total Ca, Mg, and REM content is 0.0060% or less.Group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%

[0028] Cr, Mo, Cu, and Ni contribute to improving iron loss properties by enhancing the specific resistance of steel. Thus, it is preferred that one or more of Cr, Mo, Cu, and Ni are contained in an amount of 0.01% or more in total. Meanwhile, if added excessively, a hot-rolled annealed sheet becomes hardened and more prone to fracture during cold rolling; the upper limit of the total content is preferably set to 0.40%.Group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030%

[0029] Ti, Nb, and V contribute to suppressing sheet fracture during cold rolling by improving the toughness of a hot-rolled annealed sheet through structural refinement. Therefore, the Ti, Nb, and V content is preferably set to 0.0005% or more in total. Meanwhile, if added excessively, a large amount of fine precipitates are generated so as to significantly hinder grain growth, which is why the upper limit of the total content of Ti, Nb, and V is preferably set to 0.0030%.Group D: B: 0.0001 to 0.0020%

[0030] B contributes to suppressing sheet fracture during cold rolling by improving the toughness of the sheet through segregation in the grain boundary. Thus, the B content is preferably set to 0.0001% or more. More preferably, the B content is set to 0.0003% or more. Meanwhile, the upper limit of the B content is preferably set to 0.0020%, as a B content exceeding 0.0020% results in the formation of iron borides, which diminish the toughness-improving effect.

[0031] Moreover, in order to improve various properties, it is preferred that the hot-rolled annealed sheet of this embodiment further contain at least one group of components that is selected from the following groups E to J.Group E: Zn: 0.001 to 0.010%

[0032] Zn has an effect of improving the iron loss properties of a finishing-annealed sheet by promoting grain growth when performing finishing annealing as a result of coarsening inclusions. Thus, the Zn content is preferably set to 0.001% or more. Meanwhile, a Zn content exceeding 0.010% leads to the saturation of the above effect, which is why the upper limit of the Zn content is preferably set to 0.010%.Group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%

[0033] Zr, Ta, W, and Se contribute to improving cold rollability by reducing the grain size of a hot-rolled annealed sheet through precipitate formation. Thus, it is preferred that one or more selected from Zr, Ta, W, and Se be contained in an amount of 0.001% or more in total. Meanwhile, the upper limit is preferably set to 0.010%, because a total content of greater than 0.010% may deteriorate the iron loss properties of a finishing-annealed sheet.Group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%

[0034] Ga and Ge enhance magnetic properties by improving the texture of a finishing-annealed sheet. Therefore, it is preferred that one or more selected from Ga and Ge be contained in an amount of 0.0001% or more in total. Meanwhile, the upper limit is preferably set to 0.0200%, because a content exceeding 0.0200% saturates the above effect.Group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020%

[0035] Pb and Bi contribute to improving cold rollability by reducing the grain size of a hot-rolled annealed sheet. Thus, it is preferred that one or more selected from Pb and Bi be contained in an amount of 0.00005% or more in total. Meanwhile, the upper limit is preferably set to 0.0020%, as the content exceeding 0.0020% deteriorates the iron loss properties of a finishing-annealed sheet.Group I: Co: 0.001 to 0.100%

[0036] Co contributes to improving magnetic flux density. Therefore, it is preferred that Co be contained in an amount of 0.001% or more. Meanwhile, the upper limit is preferably set to 0.100%, as the content exceeding 0.100% forms precipitates, which deteriorate the iron loss properties of a finishing-annealed sheet.Group J: As: 0.0005 to 0.020%

[0037] As contributes to improving cold rollability by reducing the grain size of a hot-rolled annealed sheet as a result of being segregated in the grain boundary. Thus, it is preferred that As be contained in an amount of 0.0005% or more. Meanwhile, the upper limit is preferably set to 0.020%, as the content exceeding0.020% rather impairs cold rollability as grain boundary fracture is facilitated.

[0038] As for the chemical composition of the hot-rolled annealed sheet of this embodiment that is used for manufacturing a non-oriented electrical steel sheet, the balance thereof other than the abovementioned elements is Fe and unavoidable impurities.<Steel structure of hot-rolled annealed sheet for non-oriented electrical steel sheet>

[0039] Next, described is a steel structure of the hot-rolled annealed sheet of this embodiment that is used for manufacturing a non-oriented electrical steel sheet. Average crystal grain size on cross-sectional surface of steel sheet in rolling direction: 40 to 250 µm

[0040] The average crystal grain size is set to 250 µm or smaller, because when the structure of a hot-rolled annealed sheet is coarse, the hot-rolled annealed sheet will embrittle whereby sheet fracture is more likely to occur during cold rolling. In terms of fracture suppression, the average crystal grain size is preferably 180 µm or smaller, more preferably 120 µm or smaller.

[0041] Meanwhile, the average crystal grain size needs to be 40 µm or larger, because if the average crystal grain size is smaller than 40 µm, there will be an increase in load during cold rolling as the hot-rolled annealed sheet hardens, and sheet fracture is more prone to occur accordingly. A preferable average crystal grain size is 60 µm or larger.Integrated intensity of Fe-Al-based oxide on steel sheet surface layer: 200 cps·deg or lower

[0042] An Fe-Al-based oxide is hard and has a poor wettability with respect to a lubricant. Thus, if such oxide remains on the steel sheet surface, the rolling roll will be damaged during cold rolling such that the friction coefficient and rolling load will increase, and rolling will become unstable accordingly, which will then lead to sheet fracture. For this reason, Fe-Al-based oxides need to be sufficiently eliminated in the pickling step; as an index, an integrated intensity of the Fe-Al-based oxide(s) on the steel sheet surface layer, which is obtained by subjecting a pickled hot-rolled annealed sheet to X-ray diffraction measurement, needs to be 200 cps·deg or lower.<Method for manufacturing hot-rolled annealed sheet for non-oriented electrical steel sheet>

[0043] Next, described is a method for manufacturing the hot-rolled annealed sheet of this embodiment that is used for manufacturing a non-oriented electrical steel sheet.

[0044] The method for manufacturing the hot-rolled annealed sheet of this embodiment that is used to manufacture a non-oriented electrical steel sheet includes a hot rolling step of obtaining a hot-rolled steel sheet by heating and hot-rolling a steel slab having the above chemical composition; a hot-rolled sheet annealing step of obtaining a hot-rolled annealed sheet by annealing the hot-rolled steel sheet; a shot blasting step of performing shot blasting on the hot-rolled annealed sheet; and a pickling step of pickling the hot-rolled annealed sheet that has been shot-blasted. In the hot rolling step, a heating temperature of the steel slab is set to 1150°C or lower, a finishing rolling temperature is set to 960°C or lower, and a coiling temperature is set to 700°C or lower. In the hot-rolled sheet annealing step, an annealing temperature is set to 800 to 1100°C; in the shot blasting step, shot blasting is performed on the hot-rolled annealed sheet at a projection density of 10 to 40 kg / m 2< . Next, in the pickling step, the shot-blasted steel sheet is pickled at a hydrochloric acid concentration of 5% or higher and a pickling temperature of 70°C or higher for a pickling time of 10 to 120 seconds. The details are shown below.[Hot rolling step]Steel slab

[0045] The chemical composition of the steel slab used to manufacture the hot-rolled annealed sheet of this embodiment that is employed for manufacturing a non-oriented electrical steel sheet is adjusted to the range(s) described above. The method for manufacturing such a steel is not particularly limited, and there may be used known refining processes such as those employing a converter, an electric furnace, and a vacuum degassing apparatus. Further, the method for manufacturing the steel slab is preferably a continuous casting process. Furthermore, as a raw material, there may be used iron scrap and direct reduced iron. Particularly, it is preferable to use iron scrap because elements useful for reducing iron loss, such as Cu and Ni, can be incorporated therefrom in an inexpensive manner.Heating temperature: 1150°C or lower

[0046] Hot rolling is a step where the steel slab having the above components is either hot-rolled immediately after its manufacturing or hot-rolled after it was cooled and then heated to a given temperature, thereby obtaining a hot-rolled sheet with a given sheet thickness. The upper limit of the heating temperature of the slab is set to 1150°C, because if the heating temperature is excessively high, AlN and MnS will remelt such that they will be finely precipitated in and beyond the hot rolling step to impair the grain growth property and iron loss. In order to improve the grain growth property and iron loss by coarsening AlN and MnS in the steel slab, the heating temperature is preferably set to 1000°C or higher. Further, a heating temperature of 1050°C or higher is more preferable in terms of realizing stable manufacturing by reducing the load in hot rolling.Finishing rolling temperature: 960°C or lower

[0047] The finishing rolling temperature in hot rolling is set to 960°C or lower, because a finishing rolling temperature exceeding 960°C will lead to a thick scale of the hot-rolled sheet and an impaired pickling property accordingly. A preferable finishing rolling temperature is 920°C or lower. Meanwhile, the lower limit of the finishing rolling temperature is preferably 750°C, because an excessively low finishing rolling temperature will lead to an increased mill load, i.e., an increased rolling load. More preferably, the finishing rolling temperature is 780°C or higher.Coiling temperature: 700°C or lower

[0048] The upper limit of the coiling temperature is set to 700°C, because a coiling temperature exceeding 700°C will lead to a larger volume of scale, particularly a thicker Fe-Al-based oxide(s), which will then result in an impaired pickling property. The coiling temperature is preferably 620°C or lower. Meanwhile, the lower limit of the coiling temperature is preferably set to 450°C, because an excessively low coiling temperature will result in large variations in temperature due to rapid cooling that takes place from completing hot rolling to performing coiling. A preferable coiling temperature is 480°C or higher in terms of reducing iron loss by coarsening precipitates during coiling.[Hot-rolled sheet annealing step]Hot-rolled sheet annealing temperature: 800 to 1100°C

[0049] Hot-rolled sheet annealing is performed to improve the magnetic properties after cold rolling and finishing annealing while improving the fracture resistance during cold rolling, by uniformizing the structure and controlling the ferrite grain size to a given range.

[0050] A hot-rolled sheet annealing temperature needs to be 1100°C or lower, because a hot-rolled sheet annealing temperature of higher than 1100°C will lead to an excessively coarsened structure and thus an impaired toughness, whereby sheet fracture is more likely to occur during cold rolling. A preferable hot-rolled sheet annealing temperature is 1030°C or lower. Moreover, the hot-rolled sheet annealing temperature is preferably set to 960°C or lower in terms of suppressing scale growth at the time of performing hot-rolled sheet annealing.

[0051] Meanwhile, the hot-rolled sheet annealing temperature needs to be 800°C or higher, because a hot-rolled sheet annealing temperature of lower than 800°C will result in an insufficiently grown grain size such that the magnetic properties after finishing annealing will deteriorate. A preferable hot-rolled sheet annealing temperature is 900°C or higher. While an annealing time is not specifically defined, it is preferably 10 seconds or longer in terms of securing uniformity.[Shot blasting step]Projection density for shot blasting: 10 to 40 kg / m 2<

[0052] By performing shot blasting on a hot-rolled annealed sheet that has yet to be pickled and thus introducing cracks into the scale, scale removal during pickling can be facilitated. Particularly, since an Fe-Al-based scale is hardly soluble in acids, an iron matrix portion that has been exposed by introducing cracks needs to be infiltrated with an acid so as to dissolve and remove the scale from the iron matrix side of the iron matrix interface. Thus, a projection density for shot blasting that is required for such purpose is 10 kg / m 2< or higher. Preferably, the projection density is 15 kg / m 2< or higher.

[0053] Meanwhile, the projection density is set to 40 kg / m 2< or lower, because a projection density of greater than 40 kg / m 2< will cause the neighboring region of the surface layer of the iron matrix to deform as well other than introducing cracks into the scale, thereby forming a start point for sheet fracture during cold rolling. A preferable projection density is 35 kg / m 2< or lower.

[0054] An average particle size of shot blasting particles is preferably 0.50 mm or smaller, because if the particle size of the shot blasting particles is large, the number of the particles colliding per unit area will decrease even at the same projection density, i.e., the number of the cracks introduced into the scale will decrease so that pickling property will be impaired. More preferably, the average particle size of the shot blasting particles is 0.30 mm or smaller in terms of promoting pickling property. Meanwhile, the average particle size of the shot blasting particles is preferably 0.15 mm or larger as an extremely small particle size will result in a diminished crack introduction effect. The average particle size of the shot blasting particles may, for example, be measured by the particle size analysis-laser diffraction methods that are described in JIS Z 8825:2013. Further, the Vickers hardness of the shot blasting particles is preferably 400 HV or higher, because if the shot blasting particles are soft, the shot blasting particles themselves will deform when colliding with the steel sheet, which makes it impossible to efficiently introduce cracks into the scale.[Brush grinding step (before pickling)]

[0055] Instead of performing shot blasting, cracks can be likewise introduced into the scale by carrying out brush grinding on a hot-rolled annealed sheet that has yet to be pickled, which will then facilitate scale removal during pickling.

[0056] It is preferred that a brush roll be used for brush grinding so that the surface of a steel sheet can be ground evenly. The material of the brush and grinding conditions may be appropriately selected; however, soft chemical fibers rather than metals are preferred for the bristle material of the brush in terms of conforming with the shape of a steel sheet and thus allowing for even grinding. Further, in terms of efficiently introducing cracks in the scale, it is preferred that the brush contain, for example, alumina-based, silicon carbide-based and / or diamond abrasive grains. It is also preferred that a cooling water be sprayed when performing brush grinding such that the grinding powder can be removed, and that overheating of the brush can be prevented as well.[Pickling step]Pickling: hydrochloric acid concentration 5% or higher, pickling temperature 70°C or higher, pickling time 10 to 120 seconds

[0057] The pickling step is a step of removing the scale of a hot-rolled annealed sheet that has already been subjected to the above shot blasting or brush grinding, where an Fe-Al-based scale in addition to iron oxides can be removed sufficiently so that sheet fracture during cold rolling can be suppressed. Thus, the hydrochloric acid concentration is set to 5% or higher. Preferably, the hydrochloric acid concentration is 8% or higher. While the upper limit of the hydrochloric acid concentration is not specifically defined, the hydrochloric acid concentration is preferably set to 20% or lower because overpickling may occur. In order to facilitate pickling, the temperature of a pickling solution (pickling temperature) is set to 70°C or higher. The pickling temperature is preferably 75°C or higher. It is preferred that the pickling temperature be set to 96°C or lower, because an excessively high pickling temperature will make overpickling more likely to occur and result in a higher manufacturing cost due to an increase in the amount of evaporation of the pickling solution. The pickling time is set to 10 seconds or longer for the sake of sufficient pickling. Preferably, the pickling time is 15 seconds or longer. The upper limit of the pickling time is set to 120 seconds, because a pickling time of greater than 120 seconds will lead to an increase in the amount of hydrogen generated such that hydrogen embrittlement will occur, which will then cause fracture easily during cold rolling. As described above, since pickling property varies depending on the Al content, the hot rolling finishing temperature, and the coiling temperature, a pickling accelerator and a pickling inhibitor may be appropriately added to the pickling solution as needed for adjustment purpose.

[0058] Further, in the present invention, from the perspective of completely removing an Fe-Al-based scale, it is preferred that the following step be further carried out in addition to the abovementioned scale removing step.Rolling and / or stretch bending step performed at elongation rate of 0.1 to 10.0% before hot-rolled sheet annealing step

[0059] Oxidation behavior during hot-rolled sheet annealing changes by exposing the iron matrix as the result of introducing cracks into the scale at the time when the steel sheet is still a hot-rolled sheet, particularly an Fe-Al-based scale. That is, since iron oxides that are relatively easily soluble in acid will be generated in parts where the iron matrix is exposed, the iron oxides of these parts will dissolve when performing pickling, followed by turning into a start point for iron matrix dissolution, whereby an Fe-Al-based scale can be removed as the iron matrix dissolves.

[0060] Thus, it is preferred that a hot-rolled sheet be elongated via light rolling and / or stretch bending. It is preferred that a skin pass rolling mill or a tension leveler be used to process a hot-rolled sheet that has yet to be subjected to hot-rolled sheet annealing at an elongation rate of 0.1% or larger. Preferably, the elongation rate is 0.3% or larger. The elongation rate is preferably set to 10.0% or smaller, because an elongation rate of greater than 10.0% will not only lead to the saturation of the above effect, but also result in an excessively large average crystal grain size of a hot-rolled annealed sheet due to strain-induced grain growth. An elongation rate of 6.0% or smaller is more preferable. Here, if performing rolling and / or stretch bending at an elongation rate of 0.1 to 10.0% before hot-rolled sheet annealing, it is preferred that the sheet be processed so that the integrated intensity of a pickled hot-rolled annealed sheet will be 150 cps·deg or lower.[Brush grinding step (after pickling)]

[0061] It is preferred that the Fe-Al-based scale that has partially remained at the time of performing pickling be mechanically removed by conducting brush grinding on the front and back surfaces of a pickled steel sheet. If performing brush grinding alone, a larger device is required, and there will be incurred a higher introduction cost and maintenance cost, in order to remove all scales including, for example, an Fe-based scale and an Fe-Al-based scale.

[0062] For this reason, device cost can be reduced by removing most of the scales via pickling and further removing only the partially remaining Fe-Al-based scale via brush grinding.

[0063] It is preferred that a brush roll be used to perform brush grinding in order to evenly grind the surface(s) of a steel sheet.

[0064] The material of the brush and grinding conditions may be appropriately selected; however, soft chemical fibers rather than metals are preferred for the bristle material of the brush in terms of conforming with the sheet shape of a steel sheet and thus being able to perform grinding evenly. Further, in terms of efficiently removing the Fe-Al-based scale, it is preferred that the brush contain, for example, alumina-based, silicon carbide-based and / or diamond abrasive grains. It is also preferred that a cooling water be sprayed when performing brush grinding such that the grinding powder can be removed, and that overheating of the brush can be prevented.

[0065] Here, if performing brush grinding on the front and back surfaces of a steel sheet after carrying out pickling, it is preferred that brush grinding be performed so that the integrated intensity of a hot-rolled annealed sheet that has been subjected to brush grinding will be 60 cps·deg or lower.

[0066] Next, described is a method for manufacturing a non-oriented electrical steel sheet from the hot-rolled annealed sheet that is obtained by the above manufacturing method of the present invention.[Cold rolling step]

[0067] It is preferred that the pickled hot-rolled annealed sheet be turned into a cold-rolled sheet with a final sheet thickness by being subjected to cold rolling once or twice or more with intermediate annealing being performed therebetween. From the perspective of production efficiency, while it is preferable to use a tandem rolling mill, a reversing rolling mill may also be used, and rolling may be performed by a common procedure.[Finishing annealing step]Finishing annealing temperature: 700 to 1100°C

[0068] A finishing annealing step after the above cold rolling is a step of achieving favorable magnetic properties via recrystallization and grain growth of the cold-rolled sheet. A soaking temperature in the above finishing annealing is preferably set to 700°C or higher. A soaking temperature of 800°C or higher is more preferable. Meanwhile, the soaking temperature is preferably set to 1100°C or lower, because an excessively high soaking temperature in finishing annealing may cause nitriding to occur during annealing and lead to a deteriorated iron loss due to overly coarsened crystal grains. More preferably, the soaking temperature is set to 1050°C or lower.Examples

[0069] The embodiment of the present invention is further described based on working examples. Here, the present invention shall not be limited to the manufacturing conditions and product performance that are shown in the following working examples. Desired performance is able to be achieved when the embodiment is within the scope of the present invention.(Example 1)

[0070] A steel having a chemical composition composed of the various components shown in Table 1 and a balance consisting of Fe and unavoidable impurities was manufactured by a common refining process, followed by turning this steel into a slab via a continuous casting method. Next, under the conditions shown in Tables 2-1 and 2-2, the above slab was heated in a gas furnace and then subjected to hot rolling composed of rough rolling and finishing rolling so as to be turned into a hot-rolled sheet having a sheet thickness of 1.8 mm and a sheet width of 1200 mm. Later, the hot-rolled sheet was subjected to hot-rolled sheet annealing before being pickled, thereby obtaining a hot-rolled annealed sheet. There, several hot-rolled sheets were subjected to one or both of light rolling that is performed before hot-rolled sheet annealing with a skin pass rolling mill; and brush grinding that is performed after pickling. Brush grinding was performed in such a way that there was employed a silicon carbide-based brush roll using silicon carbide-based abrasive grains, in which nylon was used as the bristle material. Listed in Tables 2-1 and 2-2 are the elongation rate (%) for light rolling before hot-rolled sheet annealing, and the torque (N·m) and rotation number (rpm) when performing grinding with the brush roll after pickling.Steel sheet structure

[0071] A sample was cut out from the hot-rolled annealed sheet obtained so that a sheet thickness cross-section in the rolling direction could be observed, followed by mounting, polishing, and then etching the sample so as to reveal the structure thereof, thus making it possible to observe the structure of the steel sheet. An average crystal grain size was calculated via image analysis from a photograph taken of the structure. Here, the average grain size was a circle-equivalent diameter.Integrated intensity of oxide

[0072] A sample of a size of sheet thickness × 25 × 30 mm was cut out from the hot-rolled annealed sheet obtained, and a remaining amount of the scale was measured via X-ray diffraction with respect to the surface of the steel sheet. The X-ray diffraction measurement was carried out with an incident angle of 1°, where an integrated intensity was calculated for a diffraction peak appearing at 2θ of about 36.4°, the diffraction peak corresponding to the (311) reflection of a Fe-Al-based oxide (hercynite, FeAl 2 O 4 ).Fracture resistance during cold rolling

[0073] A tandem cold rolling mill was used to roll the hot-rolled annealed sheet obtained by 8000 m in total with a final thickness being set to 0.25 mm and a threading speed at the outlet side of the final stand being set to 600 m / min except for the unsteady part in the vicinity of the welded portion. Specifically, examples exhibiting fracture once or more were evaluated as "Poor", examples exhibiting no fracture were evaluated as "Good", and examples exhibiting no fracture and a small load fluctuation in the first stand were evaluated as "Excellent".

[0074] Here, the notion of a small load fluctuation shall be understood as follows. That is, provided that L ave represents an average value of the #1 std rolling load at the time of performing rolling at 600 m / min by a tandem rolling mill, and that ΔL represents a difference between the maximum and minimum values of the above rolling load, a small load fluctuation refers to a condition where a ratio ΔL / L ave , which is a ratio between the average value L ave of the above rolling load and the difference ΔL between the maximum and minimum values of the above rolling load, is 10% or smaller when multiplied by 100.Iron loss W 10 / 400 of finishing-annealed sheet

[0075] The above cold-rolled sheet was subjected to finishing annealing under the conditions shown in Tables 2-1 and 2-2. The soaking temperature was set to 10 seconds. Test pieces each having a size of width 30 mm × length 280 mm were then collected from the obtained finishing-annealed sheet along a L direction (rolling direction) and a C direction (direction orthogonal to rolling direction), followed by measuring the iron loss W 10 / 400 of these test pieces in accordance with JIS C2550-1.

[0076] The above measurement results are shown in Tables 2-1 and 2-2. These results indicate that by controlling the manufacturing conditions of a steel sheet to the scope of the present invention, there can be obtained such a hot-rolled annealed sheet for a non-oriented electrical steel sheet that this hot-rolled annealed sheet is capable of realizing both fracture prevention during cold rolling after performing hot-rolled sheet annealing and excellent magnetic properties after performing cold-rolled sheet annealing. [Table 1]Steel No.Chemical component (mass%)RemarksCSiMnPSAlNOSnSbOthers10.00213.40.500.0130.00210.500.00120.00110.02--Invention Example20.00183.20.300.0090.00250.250.00150.00100.02--Invention Example30.00123.00.400.0150.00310.700.00080.0013-0.03-Invention Example40.00263.41.500.0120.00120.700.00230.00150.02--Invention Example50.00103.80.500.0060.00061.400.00210.00220.020.03-Invention Example60.00463.50.400.0150.00160.900.00190.00080.01--Invention Example70.00312.80.500.0120.00181.200.00100.00250.050.05-Invention Example80.00242.80.350.0090.00232.100.00290.0012-0.01-Invention Example90.00262.60.600.0120.00072.500.00240.00120.06--Invention Example100.00253.00.200.0200.00131.200.00190.0026-0.20-Invention Example110.00383.20.500.0140.00162.610.00150.00170.02--Comparative Example120.00263.00.500.0130.00150.200.00130.00240.02--Comparative Example130.00243.40.500.0130.00220.500.00150.0013---Comparative Example140.00323.20.600.0040.00090.500.00170.00110.030.0030CaInvention Example150.00263.20.500.0130.00110.500.00170.0009-0.020.0024MgInvention Example160.00203.21.800.0150.00180.700.00160.00130.04-0.0026REMInvention Example170.00143.40.500.0080.00160.700.00110.00130.02-0.02CrInvention Example180.00183.40.500.0150.00140.700.00170.00080.02-0.01MoInvention Example190.00173.70.700.0120.00110.500.00220.0014-0.020.20CuInvention Example200.00223.40.700.0090.00130.500.00230.00080.010.010.15NiInvention Example210.00253.40.700.0070.00211.200.00240.00210.02-0.4Cu, 0.2NiInvention Example220.00113.52.000.0140.00221.500.00140.00110.020.020.0015TiInvention Example230.00263.50.800.0060.00081.400.00170.00170.02-0.0005NbInvention Example240.00243.70.500.0110.00242.000.00110.00130.02-0.003VInvention Example250.00223.50.700.0050.00211.400.00130.00140.02-0.0005BInvention Example260.00173.60.700.0080.00240.900.00200.00130.02-0.02Mo, 0.0003BInvention Example270.00533.20.500.0100.00180.400.00190.00210.02--Comparative Example280.00212.00.550.0110.00150.500.00230.00220.02--Invention Example290.00135.00.600.0040.00140.350.00230.00140.02--Invention Example300.00201.90.600.0130.00210.700.00150.00150.03--Comparative Example310.00165.10.300.0090.00160.700.00130.00190.03--Comparative Example320.00183.40.140.0080.00230.700.00090.00090.03--Comparative Example330.00223.02.140.0200.00240.850.00240.00160.03--Comparative Example340.00262.40.400.0330.00310.750.00260.00120.01--Comparative Example350.00172.80.500.0160.00460.550.00220.00140.04--Invention Example360.00133.20.350.0150.00530.800.00170.00260.02--Comparative Example370.00223.80.300.0080.00210.550.00460.00220.02--Invention Example380.00183.80.400.0080.00230.700.00540.00180.02--Comparative Example390.00163.50.400.0090.00140.650.00210.00430.02--Invention Example400.00153.50.500.0090.00150.500.00230.00590.02--Comparative Example410.00223.40.550.0110.00140.800.00260.00100.04-0.005ZnInvention Example420.00153.40.550.0120.00120.800.00230.00120.04-0.006ZrInvention Example430.00163.40.550.0120.00120.800.00220.00120.04-0.002TaInvention Example440.00203.60.400.0120.00120.500.00180.00140.04-0.006WInvention Example450.00163.60.400.0090.00080.500.00180.00160.04-0.003SeInvention Example460.00183.60.400.0080.00100.600.00150.00170.04-0.003GaInvention Example470.00163.20.600.0080.00101.200.00140.00200.04-0.015GeInvention Example480.00213.20.600.0080.00131.200.00220.00160.04-0.0006PbInvention Example490.00243.20.600.0140.00151.200.00210.00150.02-0.0010B1Invention Example500.00223.20.500.0140.00151.200.00180.00130.02-0.080CoInvention Example510.00183.50.600.0120.00120.750.00230.00220.02-0.006AsInvention Example520.00233.50.600.0100.00120.750.00210.00260.02-0.0008Pb,Invention Example530.00183.50.500.0100.00170.750.00140.00150.02-0.15Cu, 0.004AsInvention Example540.00263.50.500.0100.00150.750.00130.00170.02-0.003Zn, 0.042CoInvention Example (Example 2)

[0077] Under the conditions shown in Tables 3-1 and 3-2, the slab that has been manufactured in the working example 1 and has the chemical composition composed of the various components shown in Table 1 and the balance consisting of Fe and unavoidable impurities was heated in a gas furnace and then subjected to hot rolling composed of rough rolling and finishing rolling so as to be turned into a hot-rolled sheet having a sheet thickness of 1.8 mm and a sheet width of 1200 mm. Later, the hot-rolled sheet was subjected to hot-rolled sheet annealing before being subjected to brush grinding and pickling, thereby obtaining a hot-rolled annealed sheet. There, several hot-rolled sheets were subjected to one or both of light rolling that is performed before hot-rolled sheet annealing with a skin pass rolling mill; and brush grinding that is performed after pickling. Brush grinding was performed in such a way that there was employed a silicon carbide-based brush roll using silicon carbide-based abrasive grains, in which nylon was used as the bristle material. Listed in Tables 3-1 and 3-2 are the elongation rate (%) for light rolling before hot-rolled sheet annealing, the torque (N·m) and rotation number (rpm) when performing grinding with the brush roll before pickling, and the torque (N·m) and rotation number (rpm) when performing grinding with the brush roll after pickling.Steel sheet structure

[0078] A sample was cut out from the hot-rolled annealed sheet obtained so that a sheet thickness cross-section in the rolling direction could be observed, followed by mounting, polishing, and then etching the sample so as to reveal the structure thereof, thus making it possible to observe the structure of the steel sheet. An average crystal grain size was calculated via image analysis from a photograph taken of the structure. Here, the average grain size was a circle-equivalent diameter.Integrated intensity of oxide

[0079] A sample of a size of sheet thickness × 25 × 30 mm was cut out from the hot-rolled annealed sheet obtained, and a remaining amount of the scale was measured via X-ray diffraction with respect to the surface of the steel sheet. The X-ray diffraction measurement was carried out with an incident angle of 1°, where an integrated intensity was calculated for a diffraction peak appearing at 2θ of about 36.4°, the diffraction peak corresponding to the (311) reflection of a Fe-Al-based oxide (hercynite, FeAl 2 O 4 ).Fracture resistance during cold rolling

[0080] A tandem cold rolling mill was used to roll the hot-rolled annealed sheet obtained by 8000 m in total with a final thickness being set to 0.25 mm and a threading speed at the outlet side of the final stand being set to 600 m / min except for the unsteady part in the vicinity of the welded portion. Specifically, examples exhibiting fracture once or more were evaluated as "Poor", examples exhibiting no fracture were evaluated as "Good", and examples exhibiting no fracture and a small load fluctuation in the first stand were evaluated as "Excellent".

[0081] Here, the notion of a small load fluctuation shall be understood as follows. That is, provided that L ave represents an average value of the #1 std rolling load at the time of performing rolling at 600 m / min by a tandem rolling mill, and that ΔL represents a difference between the maximum and minimum values of the above rolling load, a small load fluctuation refers to a condition where a ratio ΔL / L ave , which is a ratio between the average value L ave of the above rolling load and the difference ΔL between the maximum and minimum values of the above rolling load, is 10% or smaller when multiplied by 100.Iron loss W 10 / 400 of finishing-annealed sheet

[0082] The above cold-rolled sheet was subjected to finishing annealing under the conditions shown in Tables 3-1 and 3-2. The soaking temperature was set to 10 s. Test pieces each having a size of width 30 mm × length 280 mm were then collected from the obtained finishing-annealed sheet along a L direction (rolling direction) and a C direction (direction orthogonal to rolling direction), followed by measuring the iron loss W 10 / 400 of these test pieces in accordance with JIS C2550-1.

[0083] The above measurement results are shown in Tables 3-1 and 3-2. These results indicate that by controlling the manufacturing conditions of a steel sheet to the scope of the present invention, there can be obtained such a hot-rolled annealed sheet for a non-oriented electrical steel sheet that this hot-rolled annealed sheet is capable of realizing both fracture prevention during cold rolling after performing hot-rolled sheet annealing and excellent magnetic properties after performing cold-rolled sheet annealing.

Examples

example 1

(Example 1)

[0070]A steel having a chemical composition composed of the various components shown in Table 1 and a balance consisting of Fe and unavoidable impurities was manufactured by a common refining process, followed by turning this steel into a slab via a continuous casting method. Next, under the conditions shown in Tables 2-1 and 2-2, the above slab was heated in a gas furnace and then subjected to hot rolling composed of rough rolling and finishing rolling so as to be turned into a hot-rolled sheet having a sheet thickness of 1.8 mm and a sheet width of 1200 mm. Later, the hot-rolled sheet was subjected to hot-rolled sheet annealing before being pickled, thereby obtaining a hot-rolled annealed sheet. There, several hot-rolled sheets were subjected to one or both of light rolling that is performed before hot-rolled sheet annealing with a skin pass rolling mill; and brush grinding that is performed after pickling. Brush grinding was performed in such a way that there was emplo...

example 2

(Example 2)

[0077]Under the conditions shown in Tables 3-1 and 3-2, the slab that has been manufactured in the working example 1 and has the chemical composition composed of the various components shown in Table 1 and the balance consisting of Fe and unavoidable impurities was heated in a gas furnace and then subjected to hot rolling composed of rough rolling and finishing rolling so as to be turned into a hot-rolled sheet having a sheet thickness of 1.8 mm and a sheet width of 1200 mm. Later, the hot-rolled sheet was subjected to hot-rolled sheet annealing before being subjected to brush grinding and pickling, thereby obtaining a hot-rolled annealed sheet. There, several hot-rolled sheets were subjected to one or both of light rolling that is performed before hot-rolled sheet annealing with a skin pass rolling mill; and brush grinding that is performed after pickling. Brush grinding was performed in such a way that there was employed a silicon carbide-based brush roll using silicon ...

Claims

1. A hot-rolled annealed sheet for a non-oriented electrical steel sheet, having a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities, wherein an average crystal grain size on a cross-sectional surface of the steel sheet in a rolling direction is 40 to 250 µm, and an integrated intensity of an Fe-Al-based oxide on a steel sheet surface layer is 200 cps·deg or lower when measured by X-ray diffraction.

2. The hot-rolled annealed sheet for a non-oriented electrical steel sheet according to claim 1, wherein in addition to the chemical composition, the hot-rolled annealed sheet further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080%, group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030%, and group D: B, totaling 0.0001 to 0.0020%.

3. The hot-rolled annealed sheet for a non-oriented electrical steel sheet according to claim 1 or 2, wherein in addition to the chemical composition, the hot-rolled annealed sheet further contains, by mass%, at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020%, group I: Co, totaling 0.001 to 0.100% , and group J: As, totaling 0.0005 to 0.020%.

4. A method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet, comprising: a hot rolling step of obtaining a hot-rolled steel sheet by heating and hot-rolling a steel slab having a chemical composition that contains, by mass%, C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities; a hot-rolled sheet annealing step of obtaining a hot-rolled annealed sheet by annealing the hot-rolled steel sheet; a shot blasting step of performing shot blasting on the hot-rolled annealed sheet; and a pickling step of pickling the hot-rolled annealed sheet that has been shot-blasted, wherein: in the hot rolling step, a heating temperature of the steel slab is set to 1150°C or lower, a finishing rolling temperature is set to 960°C or lower, and a coiling temperature is set to 700°C or lower; in the hot-rolled sheet annealing step, an annealing temperature is set to 800 to 1100°C; in the shot blasting step, shot blasting is performed on the hot-rolled annealed sheet at a projection density of 10 to 40 kg / m2; in the pickling step, the shot-blasted steel sheet is pickled at a hydrochloric acid concentration of 5% or higher and a pickling temperature of 70°C or higher for a pickling time of 10 to 120 seconds.

5. The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to claim 4, wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080% , group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030% , and group D: B, totaling 0.0001 to 0.0020%.

6. The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to claim 4 or 5, wherein in addition to the chemical composition, the steel slab further contains at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020%, group I: Co, totaling 0.001 to 0.100%, and group J: As, totaling 0.0005 to 0.020%.

7. The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of claims 4 to 6, wherein before annealing the hot-rolled steel sheet, the hot-rolled steel sheet is subjected to rolling and / or stretch bending at an elongation rate of 0.1 to 10.0%.

8. The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of claims 4 to 7, wherein after the pickling step, both the front and back surfaces of the pickled steel sheet is subjected to brush grinding.

9. A method for manufacturing a non-oriented electrical steel sheet, comprising: obtaining a cold-rolled sheet with a final sheet thickness by subjecting the hot-rolled annealed sheet manufactured by the method according to any one of claims 4 to 8 to cold rolling once or twice or more with intermediate annealing being performed therebetween and obtaining a cold-rolled annealed sheet by performing annealing on the cold-rolled sheet at a soaking temperature of 700 to 1100°C.

10. A method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet, comprising: a hot rolling step of obtaining a hot-rolled steel sheet by heating and hot-rolling a steel slab having a chemical composition that contains C: 0.0050% or less, Si: 2.0 to 5.0%, Mn: 0.2 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Al: 0.25 to 2.50%, N: 0.0050% or less, O: 0.0050% or less, one or more of Sn and Sb: 0.01 to 0.20% in total, and a balance consisting of Fe and unavoidable impurities; a hot-rolled sheet annealing step of obtaining a hot-rolled annealed sheet by annealing the hot-rolled steel sheet; a brush grinding step of performing brush grinding on the hot-rolled annealed sheet; and a pickling step of pickling the hot-rolled annealed sheet that has been subjected to brush grinding, wherein in the hot rolling step, a heating temperature of the steel slab is set to 1150°C or lower, a finishing rolling temperature is set to 960°C or lower, and a coiling temperature is set to 700°C or lower; in the hot-rolled sheet annealing step, an annealing temperature is set to 800 to 1100°C; in the pickling step, the steel sheet that has been subjected to brush grinding is pickled at a hydrochloric acid concentration of 5% or higher and a pickling temperature of 70°C or higher for a pickling time of 10 to 120 seconds.

11. The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to claim 10, wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups A to D: group A: one or more selected from Ca, Mg, and REM, totaling 0.0010 to 0.0080%, group B: one or more selected from Cr, Mo, Cu, and Ni, totaling 0.01 to 0.60%, group C: one or more selected from Ti, Nb, and V, totaling 0.0005 to 0.0030%, and group D: B, totaling 0.0001 to 0.0020%.

12. The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to claim 10 or 11, wherein in addition to the chemical composition, the steel slab further contains, by mass%, at least one group of components that is selected from the following groups E to J: group E: Zn, totaling 0.001 to 0.010%, group F: one or more selected from Zr, Ta, W, and Se, totaling 0.001 to 0.010%, group G: one or more selected from Ga and Ge, totaling 0.0001 to 0.0200%, group H: one or more selected from Pb and Bi, totaling 0.00005 to 0.0020% , group I: Co, totaling 0.001 to 0.100% , and group J: As, totaling 0.0005 to 0.020%.

13. The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of claims 10 to 12, wherein before annealing the hot-rolled steel sheet, the hot-rolled steel sheet is subjected to rolling and / or stretch bending at an elongation rate of 0.1 to 10.0%.

14. The method for manufacturing a hot-rolled annealed sheet for a non-oriented electrical steel sheet according to any one of claims 10 to 13, wherein after the pickling step, both the front and back surfaces of the pickled steel sheet are subjected to brush grinding.

15. A method for manufacturing a non-oriented electrical steel sheet, comprising: obtaining a cold-rolled sheet with a final sheet thickness by subjecting the hot-rolled annealed sheet manufactured by the method according to any one of claims 10 to 14 to cold rolling once or twice or more with intermediate annealing being performed therebetween and obtaining a cold-rolled annealed sheet by annealing the cold-rolled sheet at a soaking temperature of 700 to 1100°C.

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