Method for manufacturing non-oriented electromagnetic steel sheet and non-oriented electromagnetic steel sheet

Abstract

This method for manufacturing a non-oriented electromagnetic steel sheet comprises: a refining step for producing molten steel by means of an electric furnace; a continuous casting step; a transport step; a hot rolling step; a hot rolled sheet annealing step; a cold rolling step; and a final annealing step. The component composition of a slab used therein includes not more than 0.0050 mass% of C, 2.00-4.50 mass%, Si, not more than 2.00 mass% of Mn, not more than 2.50 mass% of Al, not more than 0.0100 mass% of Ti, not more than 0.20 mass% of P, not more than 0.0050 mass% of N, not more than 0.0050 mass% of O, and not more than 0.0030 mass% of S. When T0 (°C) represents a Ti carbonitride equilibrium deposition temperature as calculated from formula (1), and T1 (°C) represents the start temperature of hot rolling in the hot rolling step, T0 and T1 satisfy formula (2).

Description

Non-oriented electrical steel sheet manufacturing method and non-oriented electrical steel sheet

[0001] The present invention relates to a method for manufacturing a non-oriented electrical steel sheet and a non-oriented electrical steel sheet.

[0002] Non-oriented electrical steel sheets are used as materials for the motor cores of EVs (electric vehicles) and home appliances. Demand for high-grade non-oriented electrical steel sheets for EV main motors has been increasing rapidly in recent years due to growing environmental concerns. There is a strong demand for low iron loss in the high-frequency range of 400 Hz and above, rather than the commercial frequency of 50 to 60 Hz.

[0003] To reduce iron loss in the high frequency range of non-oriented electrical steel sheets, it is effective to increase the resistivity by adding alloy elements such as Si, Al, and Mn, and also to reduce impurity elements such as C, N, and Ti. ２ From the perspective of reducing emissions, methods of smelting steel in electric furnaces such as electric arc furnaces using scrap iron or reduced iron as raw materials, processes directly linking thin slab casters with hot rolling, or combinations of these, have been attracting attention in recent years.

[0004] Generally, a lower N content is advantageous for improving the properties of steel, but it has been difficult to reduce N in the electric furnace process up to now. Therefore, a denitrification technique in the electric furnace process has been studied. For example, Patent Document 1 discloses that the removal of N from steel by the addition of CaO and Al ２ O ３ This publication discloses a technique for stirring molten steel at a stirring power density ε of 60 W / t or more during a denitrification treatment in which slag containing Al is brought into contact with molten steel containing Al to remove nitrogen from the molten steel.

[0005] Furthermore, studies have been conducted on the production of non-oriented electrical steel sheets by continuous casting using a thin slab caster and directly hot rolling the slab.For example, Patent Document 2 discloses a technology in which molten steel is directly continuously cast into a thin slab, which is subsequently hot rolled into a steel strip, which may or may not be annealed, and which is subsequently cold rolled once or twice or more times with intermediate annealing in between to obtain a final thickness, followed by finish annealing.

[0006] JP 2022-189514 A JP 2002-206114 A

[0007] The denitrification method disclosed in Patent Document 1, which involves adding Al via slag, is suitable for producing high-grade non-oriented electrical steel sheets with a high Al content. However, the addition of Al reduces elements that have been oxidized in the slag, such as Ti and Ca, and returns them to the molten steel, resulting in a higher Ti content in the steel than with conventional refining methods. As a result, the method disclosed in Patent Document 1 has the problem of degrading the magnetic properties of the final product. The Ti is derived from impurities in scrap, alloy raw materials, and refractories.

[0008] Furthermore, the method disclosed in Patent Document 2 has a problem in that when impurities such as Ti are mixed in the steel after it is tapped from the electric furnace, high-frequency iron loss deteriorates.

[0009] The present invention has been made in view of the above, and ２ The present invention aims to propose a method for producing non-oriented electrical steel sheets that have good high-frequency iron loss properties and that can be produced using an electric furnace-thin slab caster process with low waste.

[0010] In order to solve the above-mentioned problems and achieve the object, the method for producing a non-oriented electrical steel sheet according to the present invention includes a refining step of producing molten steel in an electric furnace, a continuous casting step of continuously casting the molten steel to produce a slab, a transport step of directly transporting the slab to a heating device, a hot rolling step of hot rolling the slab heated by the heating device to produce a hot-rolled steel sheet, a hot-rolled sheet annealing step of hot-rolling the hot-rolled steel sheet to produce a hot-rolled annealed sheet, a cold rolling step of cold-rolling the hot-rolled annealed sheet to produce a cold-rolled steel sheet, and a finish annealing step of finish annealing the cold-rolled steel sheet. and a annealing process, wherein the slab has a chemical composition of C: 0.0050 mass% or less, Si: 2.00 to 4.50 mass%, Mn: 2.00 mass% or less, Al: 2.50 mass% or less, Ti: 0.0100 mass% or less, P: 0.20 mass% or less, N: 0.0050 mass% or less, O: 0.0050 mass% or less, and S: 0.0030 mass% or less, and when the equilibrium precipitation temperature of Ti carbonitrides calculated from the following formula (1) is T0 (°C) and the start temperature of the hot rolling in the hot rolling process is T1 (°C), T0 and T1 satisfy the following formula (2).

[0011] Furthermore, in the method for producing a non-oriented electrical steel sheet according to the present invention, in the above invention, in the hot rolling step, the heating time of the slab is 30 minutes or less, the end temperature of the hot rolling is 800°C or higher, and the coiling temperature is 500 to 700°C.

[0012] Furthermore, in the method for producing a non-oriented electrical steel sheet according to the present invention, in the above invention, the hot-rolled sheet annealing step is performed at an annealing temperature of 700 to 1200°C, the cold-rolling step is performed at a rolling reduction of 95.0% or less to cold-roll the sheet to a thickness of 0.30 mm or less, and the finish annealing step is performed at an annealing temperature of 800 to 1100°C and soaking for 2 seconds or more.

[0013] Further, in the method for producing a non-oriented electrical steel sheet according to the present invention, in the above invention, the slab contains, in addition to the above-mentioned chemical composition, one or more of Sn and Sb in total of 0.100 mass% or less, Ca: 0.010 mass% or less, Mg: 0.0050 mass% or less, Ce: 0.010 mass% or less, La: 0.010 mass% or less, Nd: 0.010 mass% or less, Y: 0.010 mass% or less, Cu: 2.0 mass% or less, Ni: 1.0 mass% or less, Cr: 1.0 mass% or less, Mo: 0.010 mass% or less, and . Contains at least one of the following elements: 1.0 mass% or less, Nb: 0.010 mass% or less, V: 0.10 mass% or less, W: 0.05 mass% or less, Ta: 0.05 mass% or less, Co: 1.0 mass% or less, B: 0.0100 mass% or less, Pb: 0.0100 mass% or less, Zn: 0.10 mass% or less, As: 0.010 mass% or less, Zr: 0.010 mass% or less, Bi: 0.010 mass% or less, Ge: 0.05 mass% or less, and Ga: 0.05 mass% or less.

[0014] In addition, in the method for producing a non-oriented electrical steel sheet according to the present invention, the sheet thickness is 0.30 mm or less and the iron loss W10 / 400 is 13.5 W / Kg or less.

[0015] In addition, in the method for producing a non-oriented electrical steel sheet according to the present invention, the sheet thickness is 0.25 mm or less and the iron loss W10 / 400 is 13.0 W / Kg or less.

[0016] Furthermore, the method for producing a non-oriented electrical steel sheet according to the present invention includes, in the above invention, a refining step of producing molten steel using an electric furnace and a vacuum decarburization apparatus having a ladle housed inside a vacuum tank.

[0017] In order to solve the above-mentioned problems and achieve the object, a non-oriented electrical steel sheet according to the present invention is produced using an electric furnace and has a chemical composition of C: 0.0050% by mass or less, Si: 2.00 to 4.50% by mass, Mn: 2.00% by mass or less, Al: 2.50% by mass or less, Ti: 0.0100% by mass or less, P: 0.20% by mass or less, N: 0.0050% by mass or less, O: 0.0050% by mass or less, and S: 0.0030% by mass or less, and the particle size of Ti precipitates present in the steel sheet is 30 to 2000 nm.

[0018] In order to solve the above-mentioned problems and achieve the object, a non-oriented electrical steel sheet according to the present invention is produced using an electric furnace and has a chemical composition of C: 0.0050% by mass or less, Si: 2.00 to 4.50% by mass, Mn: 2.00% by mass or less, Al: 2.50% by mass or less, Ti: 0.0100% by mass or less, P: 0.20% by mass or less, N: 0.0050% by mass or less, O: 0.0050% by mass or less, S: 0.0030% by mass or less, and in addition to the above-mentioned chemical composition, one or more of Sn and Sb in total of 0.100% by mass or less, Ca: 0.010% by mass or less, Mg: 0.0050% by mass or less, Ce: 0.010% by mass or less, La: 0.010% by mass or less, Nd: 0.010% by mass or less The steel sheet contains at least one of the following: Y: 0.010% by mass or less, Cu: 2.0% by mass or less, Ni: 1.0% by mass or less, Cr: 1.0% by mass or less, Mo: 0.10% by mass or less, Nb: 0.010% by mass or less, V: 0.10% by mass or less, W: 0.05% by mass or less, Ta: 0.05% by mass or less, Co: 1.0% by mass or less, B: 0.0100% by mass or less, Pb: 0.0100% by mass or less, Zn: 0.10% by mass or less, As: 0.010% by mass or less, Zr: 0.010% by mass or less, Bi: 0.010% by mass or less, Ge: 0.05% by mass or less, and Ga: 0.05% by mass or less, and the particle size of Ti precipitates present in the steel sheet is 30 to 2000 nm.

[0019] Furthermore, in the non-oriented electrical steel sheet according to the present invention, the sheet thickness is 0.30 mm or less and the iron loss W10 / 400 is 13.5 W / Kg or less.

[0020] Furthermore, in the non-oriented electrical steel sheet according to the present invention, the sheet thickness is 0.25 mm or less and the iron loss W10 / 400 is 13.0 W / Kg or less.

[0021] Furthermore, the non-oriented electrical steel sheet according to the present invention is produced using a vacuum decarburization apparatus in which a ladle is housed inside an electric furnace and a vacuum tank in the above-mentioned invention.

[0022] According to the method for producing a non-oriented electrical steel sheet of the present invention, CO ２A non-oriented electrical steel sheet with good high-frequency core loss can be manufactured using an electric furnace-thin slab caster process with low emissions. Furthermore, the non-oriented electrical steel sheet according to the present invention can improve high-frequency core loss.

[0023] Fig. 1 is a flowchart showing the flow of a method for manufacturing a non-oriented electrical steel sheet according to an embodiment. Fig. 2 is an example of the method for manufacturing a non-oriented electrical steel sheet according to an embodiment, and is a graph showing the relationship between iron loss W10 / 400 and ΔT (=hot rolling start temperature−T0). Fig. 3 is a measurement example of the particle size of Ti precipitates in a finish-annealed sheet in the method for manufacturing a non-oriented electrical steel sheet according to an embodiment, showing an example of Ti precipitates having a particle size of 30 to 2000 nm. Fig. 4 is a measurement example of the particle size of Ti precipitates in a finish-annealed sheet in the method for manufacturing a non-oriented electrical steel sheet according to an embodiment, showing an example of Ti precipitates having a particle size of less than 30 nm.

[0024] A method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention will be described with reference to the drawings. Note that the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical.

[0025] The present inventors have conducted detailed studies on the refining method of electric furnace tapped steel, steel composition, hot rolling, and process conditions after hot rolling, and have arrived at the present invention. That is, the present inventors have found that Ti, which is mixed in from the iron source, alloy raw materials, etc., precipitates finely, inhibiting recrystallization and grain growth, thereby significantly deteriorating iron loss. To solve this problem, the present inventors have discovered conditions under which Ti fine precipitation can be suppressed and a non-oriented electrical steel sheet with excellent high-frequency iron loss can be produced by controlling the hot rolling start temperature and the reduction rate in the first pass of hot rolling in accordance with the relationship between the steel composition and the hot rolling conditions, and have arrived at the present invention.

[0026] In the method for producing a non-oriented electrical steel sheet according to the embodiment, a refining step S1, a continuous casting step S2, a transporting step S3, a hot rolling step S4, a hot-rolled sheet annealing step S5, a cold rolling step S6, and a finish annealing step S7 are carried out in this order, as shown in Fig. 1. Each step will be described in detail below.

[0027] (Refining Process) In the refining process, molten steel is produced in an electric furnace. In this process, scrap and reduced iron are first melted in the electric furnace, and the resulting undeoxidized molten steel is tapped from the electric furnace into a ladle. The surface of this ladle that comes into contact with the slag is lined with magnesia-based refractories. When tapping steel from the electric furnace into a ladle, it is desirable to avoid letting slag flow into the ladle as much as possible, or to remove the slag after the slag has flowed into the ladle.

[0028] After the tapping is completed, the ladle is transferred to a vacuum degassing apparatus equipped with an exhaust system, and decarburization is performed by blowing in an inert gas for stirring into the molten steel in a reduced pressure atmosphere. The inert gas for stirring used in the decarburization treatment is preferably, for example, Ar gas that does not contain nitrogen gas.

[0029] When a ladle vacuum degasser, for example, is used as the vacuum degasser, the ladle is placed in a vacuum tank, and an inert stirring gas is blown into the molten steel from a nozzle (bottom-blowing gas blowing pipe) installed at the bottom of the ladle. In addition to the above, the inert stirring gas may be blown into the molten steel through a lance immersed in the molten steel.

[0030] After the decarburization treatment is completed, a metallic Al-containing substance is added from above the ladle to deoxidize the molten steel, and then the process moves to the denitrification / desulfurization treatment. The timing and number of times that the metallic Al-containing substance is added are not particularly limited, as long as it is added at least once between the completion of the decarburization treatment and the completion of the denitrification / desulfurization treatment. The decarburization treatment and the denitrification / desulfurization treatment can be performed in separate equipment. However, since the equipment for the denitrification / desulfurization treatment must be capable of reacting the molten steel with the slag, it is preferable to perform the treatment in the ladle vacuum degassing equipment or ladle refining equipment described above. The addition of the Al-containing substance after the completion of the decarburization treatment can be performed in either or both of the above-mentioned equipment. However, it is preferable to add some or all of the Al-containing substance at the start of the denitrification / desulfurization treatment.

[0031] When performing denitrification and desulfurization treatment, the higher the slag conversion rate, the more advantageous it is for the denitrification and desulfurization reaction. Therefore, the CaO and Al in the slag are ２ O ３If the mass ratio C / A(-) is too high or too low, the slag conversion rate will be low. In order to ensure the slag conversion rate, it is effective to adjust this C / A(-) to, for example, 0.7 to 1.7.

[0032] However, if the slag turns into slag, the refractory material in contact with the slag is easily eroded. If the amount of erosion increases, the life of the ladle is shortened and costs increase. Furthermore, in the case of magnesia-based refractories, which are commonly used as refractories for ladles, the refractory is eroded and MgO is eluted into the slag. As shown in Patent Document 1, the elution of MgO into the slag adversely affects the denitrification process.

[0033] At the same time, if the refractory contains C or Ti oxides, these will also be eluted, with some of the C remaining as an impurity in the steel, and Ti oxides being reduced by Al in the steel and becoming an impurity in the steel, which will have an adverse effect on the electromagnetic properties of the steel sheet.

[0034] As a result of extensive research, it was found that, within the range of C / A(-) of 0.7 to 1.7, the higher the C / A(-), the smaller the corrosion of the magnesia-based refractory. It was also found that, even if MgO is eluted into the slag, in order to suppress the elution to a level that does not adversely affect the denitrification treatment, it is desirable to set the lower limit of C / A(-) to 1.0.

[0035] Furthermore, since the slag formation rate decreases when the temperature is low or when MgO is present in the slag, it is desirable to lower the liquidus temperature of the slag as much as possible when the C / A(-) ratio is high. Therefore, it is desirable to set the upper limit of C / A(-) to 1.4, and by further setting the upper limit to 1.2, it becomes possible to more effectively eliminate inhibiting factors.

[0036] Thus, in the denitrification and desulfurization treatment process, at the start of the denitrification and desulfurization treatment process, CaO and Al in the slag ２ O ３ The mass ratio C / A(-) of the additives (CaO and / or Al) added during tapping is set to a range of 1.0 to 1.4. ２ O ３ The amount of additives (CaO and / or Al) added between the end of tapping and the end of decarburization treatment２ O ３ The amount of the additive (containing substance) can be controlled.

[0037] Furthermore, if the slag is pushed aside by the injection of the stirring inert gas during the formation of the slag, exposing a large area of ​​the molten steel, the molten steel may come into contact with the air in the atmosphere, which may inhibit the denitrification / desulfurization reaction. Therefore, it is desirable to set the slag thickness to 100 mm or more at the start of the denitrification / desulfurization treatment process.

[0038] There is no particular upper limit to the thickness of the slag, as long as it is thick enough to avoid CO gas generated during decarburization, swelling of the molten steel surface due to the blowing of inert gas, or overflow from the upper end of the ladle due to slag foaming. The thickness of the slag may vary depending on the amount of additives (CaO and / or Al) added during tapping, for example. ２ O ３ The amount of additives (CaO and / or Al) added between the end of tapping and the end of decarburization treatment ２ O ３ The amount of the additive (containing substance) can be controlled.

[0039] (Continuous Casting Process) In the continuous casting process, molten steel is continuously cast to produce a slab. In this process, it is preferable to continuously cast the molten steel that has been refined and its composition adjusted in the refining process into a slab with a thickness of 40 to 170 mm. If the slab thickness is thinner than 40 mm, the cooling rate of the slab increases, which may result in fine dispersion of inclusions such as oxides, resulting in a deterioration in the iron loss of the final product. Furthermore, if the slab thickness is thicker than 170 mm, the casting speed may decrease, which may result in a decrease in production efficiency. Therefore, it is preferable that the slab thickness be 40 to 170 mm.

[0040] The chemical composition of the slab is as follows: C: 0.0050% by mass or less, Si: 2.00 to 4.50% by mass, Mn: 2.00% by mass or less, Al: 2.50% by mass or less, Ti: 0.0100% by mass or less, P: 0.20% by mass or less, N: 0.0050% by mass or less, O: 0.0050% by mass or less, and S: 0.0030% by mass or less. The reason for limiting the chemical composition of the slab to the above will be explained below.

[0041] <C: 0.0050% by mass or less> C is an element that forms carbides and deteriorates the iron loss of the final product. Therefore, the C content is set to 0.0050% by mass or less. In particular, when C combines with Ti and precipitates, the influence of iron loss deterioration is large. Therefore, the C content is preferably set to 0.0035% by mass or less. There is no particular lower limit for the C content, but from the viewpoint of improving the toughness of the hot-rolled annealed sheet and preventing fracture during cold rolling, it is preferably set to 0.0010% by mass or more.

[0042] <Si: 2.00 to 4.50 mass%> Si has the effect of increasing the resistivity of steel and reducing high-frequency iron loss in the final product. Therefore, the Si content is set to 2.00 mass% or more. Furthermore, the Si content is preferably set to 2.50 mass% or more, and more preferably set to 2.70 mass% or more. Furthermore, if the Si content exceeds 4.50 mass%, the steel becomes embrittled and is prone to fracture during cold rolling. Therefore, the Si content is preferably set to 4.50 mass% or less, and more preferably set to 4.00 mass% or less.

[0043] <Mn: 2.00% by mass or less> Like Si, Mn is an element useful for reducing high-frequency iron loss. Therefore, the Mn content is preferably 0.20% by mass or more, and more preferably 0.35% by mass or more. On the other hand, if the Mn content exceeds 2.00% by mass, Mn carbides are formed, which deteriorates high-frequency iron loss. Therefore, the Mn content is preferably 2.00% by mass or less.

[0044] <Al: 2.50 mass% or less> Like Si, Al has the effect of increasing the resistivity of steel and reducing high-frequency iron loss. Therefore, it is preferable to add Al in an amount of 0.20 mass% or more. Furthermore, from the viewpoint of efficiently reducing N during refining, it is more preferable to add Al in an amount of 0.50 mass% or more. On the other hand, excessive addition of Al causes embrittlement and makes the steel more susceptible to fracture during cold rolling. Therefore, the Al content is preferably 2.50 mass% or less, and more preferably 2.20 mass% or less.

[0045] <Ti: 0.0100% by mass or less> Ti is an element that forms carbides, nitrides, or carbonitrides and deteriorates high-frequency iron loss. Therefore, the Ti content needs to be 0.0100% by mass or less. In this embodiment, if the Ti content is high, the hot rolling start temperature needs to be high, which increases the production cost. Therefore, the Ti content is preferably 0.0080% by mass or less. Furthermore, in the refining process of this embodiment, Ti derived from the alloy raw materials and the like is likely to be mixed into the molten steel. Therefore, reducing the Ti content to 0.0010% by mass or less increases the refining cost. Therefore, the lower limit of the Ti content is preferably 0.0010% by mass.

[0046] <P: 0.20% by mass or less> P embrittles the steel sheet due to grain boundary segregation and reduces rollability. Therefore, the P content needs to be 0.20% by mass or less. Furthermore, the P content is preferably 0.10% by mass or less. Although there is no particular lower limit for the P content, excessive reduction of the P content results in excessively high refining costs, so the P content is preferably 0.005% by mass or more.

[0047] <N: 0.0050% by mass or less> N is an element that forms nitrides and deteriorates high-frequency iron loss. Therefore, the N content is set to 0.0050% by mass or less. In the refining process of this embodiment, when Ti is mixed into the molten steel, Ti carbonitrides are formed, which tend to cause deterioration in iron loss. Therefore, the N content is preferably set to 0.0025% by mass or less. There is no particular lower limit for the N content, but if the N content is reduced excessively, the refining cost becomes excessive, so the N content is preferably set to 0.0005% by mass or more.

[0048] <O: 0.0050% by mass or less> O is an element that forms oxides and deteriorates iron loss. Therefore, the O content is set to 0.0050% by mass or less. Furthermore, the O content is preferably set to 0.0025% by mass or less. Furthermore, reducing the O content to less than 0.0004% by mass results in excessive refining costs. Therefore, the O content is preferably set to 0.0004% by mass or more.

[0049] <S: 0.0030% by mass or less> S is a harmful element that forms fine sulfides and deteriorates iron loss. In addition, in this embodiment, S affects the precipitation behavior of Ti precipitates, and when S exceeds 0.0030% by mass, fine precipitation of Ti also deteriorates high-frequency iron loss. Therefore, the S content needs to be 0.0030% by mass or less. Furthermore, the S content is preferably 0.0010% by mass or less. Furthermore, attempting to reduce the S content to less than 0.0003% by mass results in excessively high refining costs. Therefore, the S content is preferably 0.0004% by mass or more.

[0050] <Others> In addition to the above, the slab may contain, for example, one or more of Sn and Sb in a total amount of 0.100 mass% or less. Sn and Sb are elements effective in improving the texture of the steel sheet after finish annealing and thereby enhancing the magnetic properties, so their addition is preferable. Furthermore, in order to obtain the above effect, it is preferable to add one or more of Sn and Sb in a total amount of 0.010 mass% or more. On the other hand, if Sn and Sb are added in excess, the above effect saturates. Therefore, it is sufficient to add at least one of Sn and Sb in a total amount of 0.100 mass% or less.

[0051] In addition to the above, the slab may further contain at least one of the following elements: Each element will be explained below.

[0052] <Ca: 0.010% by mass or less, Mg: 0.0050% by mass or less> Ca and Mg are preferably added because they fix S as sulfides and contribute to improving iron loss. Furthermore, to obtain the above effects, it is preferable to add 0.0005% by mass or more of Ca and Mg, respectively. On the other hand, excessive addition of Ca and Mg can lead to the formation of inclusions, which impair manufacturability. Therefore, it is preferable to set the upper limit of Ca to 0.010% by mass and the upper limit of Mg to 0.0050% by mass.

[0053] <Ce: 0.010% by mass or less, La: 0.010% by mass or less, Nd: 0.010% by mass or less, Y: 0.010% by mass or less> Ce, La, Nd, and Y are preferably added because they are elements that fix S as sulfides and contribute to improving iron loss. Furthermore, to achieve the above effects, it is preferable to add 0.0002% by mass or more of Ce, La, Nd, and Y, respectively. On the other hand, excessive addition of Ce, La, Nd, and Y can form inclusions, impairing manufacturability. Therefore, the upper limits of Ce, La, Nd, and Y are preferably set to 0.010% by mass. Furthermore, it is more preferable to set the upper limits of Ce, La, Nd, and Y, respectively, to 0.005% by mass.

[0054] <Cu: 2.0% by mass or less, Ni: 1.0% by mass or less, Cr: 1.0% by mass or less> Cu, Ni, and Cr are preferably added because they all have the effect of increasing the resistivity of the steel sheet and improving iron loss. To achieve the above effects, it is preferable to add Cu in an amount of 0.02% by mass or more, Ni in an amount of 0.01% by mass or more, and Cr in an amount of 0.02% by mass or more. On the other hand, excessive addition of Cu, Ni, or Cr can deteriorate the surface properties and iron loss. Therefore, it is preferable to set the upper limit of Cu to 2.0% by mass, the upper limit of Ni to 1.0% by mass, and the upper limit of Cr to 1.0% by mass.

[0055] <Mo: 0.10% by mass or less> Mo is preferably added because it has the effect of promoting the precipitation of Ti at high temperatures and contributing to the coarsening of Ti precipitates. Furthermore, in order to obtain the above effects, it is preferable to add 0.0010% by mass or more of Mo. On the other hand, excessive addition of Mo inhibits grain growth and deteriorates iron loss. Therefore, the upper limit of Mo is preferably set to 0.10% by mass.

[0056] <Nb: 0.010% by mass or less> Like Ti, Nb is a harmful element that forms precipitates and deteriorates iron loss, but adding (mixing) Nb up to 0.010% by mass does not impair the effects of the present invention. The upper limit of Nb is preferably 0.005% by mass, and more preferably 0.001% by mass.

[0057] <V: 0.10% by mass or less> Like Ti, V is a harmful element that forms precipitates and deteriorates iron loss, but adding up to 0.10% by mass does not impair the effects of the present invention. The upper limit of V is preferably 0.050% by mass, and more preferably 0.020% by mass.

[0058] <W: 0.05% by mass or less> Like Ti, W is a harmful element that forms precipitates and deteriorates iron loss, but addition of up to 0.05% by mass does not impair the effects of the present invention. The upper limit of W is preferably set to 0.02% by mass.

[0059] Ta: 0.05% by mass or less Similar to Ti, Ta is a harmful element that forms precipitates and deteriorates iron loss, but addition of up to 0.05% by mass does not impair the effects of the present invention. The upper limit of Ta is preferably 0.02% by mass.

[0060] <Co: 1.0% by mass or less> Co has the effect of improving magnetic flux density, so it is preferable to add 0.001% by mass or more. On the other hand, if Co is added in excess, precipitates are formed and iron loss is deteriorated. Therefore, the upper limit of Co is preferably set to 1.0% by mass.

[0061] <B: 0.0100% by mass or less> B is a harmful element that segregates at grain boundaries, inhibits grain growth, and deteriorates iron loss, but addition of up to 0.0100% by mass does not impair the effects of the present invention. The upper limit of B is preferably 0.0030% by mass, and more preferably 0.0010% by mass.

[0062] <Pb: 0.0100% by mass or less> Pb is a harmful element that forms fine precipitates and deteriorates iron loss, but addition of up to 0.0100% by mass does not impair the effects of the present invention. The upper limit of Pb is preferably 0.0040% by mass, and more preferably 0.0010% by mass.

[0063] <Zn: 0.10 mass% or less> Zn is preferably added because it has the effect of suppressing nitriding during finish annealing. Furthermore, in order to obtain the above effect, Zn is preferably added in an amount of 0.002 mass% or more. On the other hand, if the amount of Zn added exceeds 0.10 mass%, sulfides are formed, which deteriorates iron loss. Therefore, the upper limit of Zn is set to 0.10 mass%. Furthermore, the upper limit of Zn is preferably set to 0.010 mass%.

[0064] <As: 0.010% by mass or less> As is an element that causes embrittlement due to grain boundary segregation and reduces rollability, but addition of up to 0.010% by mass does not impair the effects of the present invention. The upper limit of As is preferably set to 0.005% by mass.

[0065] <Zr: 0.010% by mass or less> Zr is a harmful element that forms precipitates and deteriorates core loss, but addition of up to 0.010% by mass does not impair the effects of the present invention.

[0066] <Bi: 0.010% by mass or less> Bi is a harmful element that forms fine precipitates and deteriorates iron loss, but addition of up to 0.010% by mass does not impair the effects of the present invention. The upper limit of Bi is preferably 0.005% by mass, and more preferably 0.002% by mass.

[0067] <Ge: 0.05% by mass or less, Ga: 0.05% by mass or less> Ge and Ga have the effect of improving texture and magnetic properties, so it is preferable to add 0.0005% by mass or more. On the other hand, if Ge and Ga are added in excess, not only will the effect saturate but costs will also increase. Therefore, it is preferable to set the upper limit of Ge and Ga to 0.05% by mass.

[0068] (Transportation Step) In the transportation step, the slab is directly transported to the heating device.

[0069] In the hot rolling process, the slab heated by the heating device is hot-rolled to produce a hot-rolled steel sheet. In this process, the start temperature of hot rolling in the hot rolling process (hereinafter referred to as "hot rolling start temperature") is controlled according to the contents of C, Al, and Ti of the slab.

[0070] That is, when the equilibrium precipitation temperature of Ti carbonitride calculated from the following formula (1) is T0 (°C) and the hot rolling start temperature is T1 (°C), T0 and T1 are set to satisfy the following formula (2).

[0071]

[0072] The above formula (1) was determined by calculating the equilibrium precipitation temperature of Ti carbonitride for various steel components targeted in this embodiment using thermodynamic calculation software (Thermo-calc ver. 2020b, database: TCFE10), and then performing multiple regression analysis on ln([C]), ln([Al]), ln([Ti]), and the equilibrium precipitation temperature T0. In the above formula (1), ln is the natural logarithm.

[0073] Although the details of the mechanism by which a non-oriented electrical steel sheet with good high-frequency iron loss can be obtained under these hot rolling conditions are unknown, the inventors believe that starting hot rolling in a temperature range where the degree of supercooling for the precipitation of Ti carbonitrides is small and introducing dislocations into the steel sheet suppresses the fine precipitation of Ti carbonitrides, resulting in sufficient recrystallization and grain growth, which improves iron loss.

[0074] Specifically, the inventors have found that a good core loss can be obtained under the condition that ΔT, which is the difference between the equilibrium precipitation temperature T0 of Ti carbonitrides and the rolling start temperature T1, is −70° C. or higher (see FIG. 2 described later). In other words, it is sufficient that the rolling start temperature T1 and the equilibrium precipitation temperature T0 satisfy the relationship of the above formula (2).

[0075] In addition to controlling the hot rolling conditions as described above, it is also important to reduce the S content to 0.0030% by mass or less. This is not just the effect of reducing sulfides such as MnS, which has been known in the past. MnS also precipitates during the hot rolling process, just like Ti precipitates. However, when the S content is high (for example, exceeding 0.0030% by mass), MnS precipitates using dislocations introduced under rolling in the first pass of hot rolling as nucleation sites, reducing the number of precipitation sites for Ti precipitates and preventing Ti from precipitating in the high-temperature range. As a result, the inventors believe that Ti precipitates precipitate finely in the steel sheet in the low-temperature range of hot rolling, deteriorating iron loss.

[0076] As described above, by starting hot rolling in a temperature range where the supercooling of Ti carbonitrides is small and introducing dislocations into the steel sheet, fine precipitation of Ti carbonitrides is suppressed and iron loss can be improved. Therefore, the hot rolling start temperature is set to T0-70 (°C) or higher. Furthermore, from the viewpoint of promoting precipitation at high temperatures, the rolling reduction rate in the first pass is preferably set to 20% or higher, and more preferably set to 50% or higher.

[0077] The heating method of the heating device may be a common method such as a gas furnace, an electric heating furnace, or an induction furnace. The slab heating temperature is an important factor for controlling the hot rolling start temperature, which will be described later. For example, if the heating temperature is less than 1000°C, a sufficient hot rolling start temperature cannot be ensured, resulting in deterioration of iron loss. Therefore, the heating temperature is preferably 1000°C or higher, and more preferably 1050°C or higher. On the other hand, if the heating temperature is 1200°C or higher, the generation of scale increases, which can cause surface defects. Therefore, the slab heating temperature is preferably 1000 to 1200°C.

[0078] The heating time of the slab may be any time that the temperature of the slab becomes uniform in the width direction and thickness direction. From the viewpoint of manufacturing efficiency, the heating time of the slab is preferably 30 minutes or less. Furthermore, from the viewpoint of stably and uniformly maintaining the temperature of the slab, the heating time of the slab is preferably 3 minutes or more.

[0079] Furthermore, if the end temperature of hot rolling is less than 800°C, Ti precipitates finely in the latter stage of hot rolling when the steel sheet temperature drops, which causes deterioration of iron loss. Therefore, the end temperature of hot rolling is preferably 800°C or higher. Furthermore, the end temperature of hot rolling is more preferably 830°C or higher. On the other hand, if the end temperature of hot rolling is too high, the scale becomes thick and the pickling properties deteriorate. Therefore, the end temperature of hot rolling is preferably 950°C or lower.

[0080] Furthermore, in order to coarsen Ti precipitates precipitated during hot rolling and improve iron loss, the coiling temperature is preferably set to 500°C or higher. On the other hand, if the coiling temperature exceeds 700°C, the scale becomes thick and pickling properties deteriorate. Therefore, the coiling temperature is preferably set to 700°C or lower.

[0081] (Hot-rolled sheet annealing step) In the hot-rolled sheet annealing step, the hot-rolled steel sheet is subjected to hot-rolled sheet annealing to form a hot-rolled annealed sheet.

[0082] The annealing temperature of the hot-rolled sheet is preferably 700°C or higher to promote recrystallization and grain growth of the hot-rolled sheet structure. On the other hand, if the annealing temperature of the hot-rolled sheet exceeds 1200°C, the structure becomes too coarse, resulting in a decrease in toughness and causing fracture during cold rolling. Therefore, the annealing temperature of the hot-rolled sheet is preferably 1200°C or lower.

[0083] In particular, when annealing a hot-rolled steel sheet in a continuous annealing furnace, some fine precipitates can be dissolved by setting the annealing temperature to 900°C or higher and the annealing time to 10 seconds or longer. This allows the steel sheet structure to recrystallize and undergo grain growth, improving the iron loss of the final product. Therefore, it is more preferable to set the annealing temperature to 900°C or higher and the annealing time to 10 seconds or longer. Furthermore, it is more preferable to set the annealing temperature to 950°C or higher. On the other hand, if the annealing temperature exceeds 1100°C, coarse precipitates such as Ti may be redissolved and precipitate finely during cooling or finish annealing, resulting in a decrease in iron loss. Therefore, it is preferable to set the annealing temperature to 1100°C or lower.

[0084] For the same reason, the annealing time is preferably 60 seconds or less. When hot-rolled sheet annealing is performed in a continuous annealing furnace, it is preferable to perform pickling after annealing the hot-rolled steel sheet. The pickling conditions may be a general method, and it is more preferable to appropriately combine, for example, skin-pass rolling, tension leveling, shot blasting, brush grinding, etc.

[0085] Furthermore, when annealing a hot-rolled steel sheet in a box annealing furnace, the heating rate and cooling rate are slow, resulting in a relatively low temperature and long time, and therefore the conditions are different from those for annealing a hot-rolled steel sheet in a continuous annealing furnace. In this case, by setting the annealing temperature to 800°C or higher and the annealing time to 1800 seconds or longer, fine precipitates are coarsened, the steel sheet structure undergoes recrystallization and grain growth, and the iron loss of the final product is improved. On the other hand, if the annealing temperature exceeds 900°C, the structure of the steel sheet becomes excessively coarsened, which may cause fracture during cold rolling. Therefore, it is preferable to set the annealing temperature to 900°C or lower.

[0086] For the same reason, the annealing time is preferably 6 hours or less. When annealing a hot-rolled steel sheet in a box annealing furnace, it is preferable to pickle the hot-rolled steel sheet before annealing. The pickling may be performed under general conditions, and it is more preferable to appropriately combine, for example, skin-pass rolling, tension leveling, shot blasting, brush grinding, etc.

[0087] (Cold Rolling Step) In the cold rolling step, the hot-rolled annealed sheet is cold-rolled to form a cold-rolled steel sheet. In this step, the hot-rolled annealed steel sheet is cold-rolled to form a cold-rolled steel sheet having a final thickness (product thickness).

[0088] If the reduction rate in cold rolling exceeds 95.0%, the texture changes and the magnetic properties deteriorate, so the reduction rate is preferably 95.0%, and more preferably 90.0% or less.

[0089] Conditions other than the reduction ratio in cold rolling do not need to be particularly limited as long as the final plate thickness can be achieved, and for example, a tandem rolling mill, a reverse rolling mill, etc. may be used. In addition, the final plate thickness in cold rolling is preferably 0.30 mm or less from the viewpoint of reducing iron loss.

[0090] (Finish annealing step) In the finish annealing step, the cold-rolled steel sheet is subjected to finish annealing according to the desired magnetic properties or mechanical properties.

[0091] From the viewpoint of achieving low iron loss, the annealing temperature is preferably 800°C or higher, and more preferably 970°C or higher. On the other hand, if the annealing temperature exceeds 1100°C, the grain size becomes excessively coarse, resulting in deterioration of high-frequency iron loss. Therefore, the annealing temperature is preferably 1100°C or lower. Furthermore, the annealing time is sufficient as long as the steel sheet is sufficiently soaked, and is preferably 2 seconds or longer. Furthermore, in order to prevent the grain size from becoming excessively coarse, the annealing time is preferably 120 seconds or shorter.

[0092] Furthermore, in this embodiment, it is important to suppress fine precipitation of Ti. By suppressing fine precipitation of Ti, recrystallization and grain growth are promoted in the hot-rolled sheet annealing and finish annealing processes, and good iron loss can be obtained. Therefore, it is preferable that the particle diameter of Ti precipitates present in the steel sheet after finish annealing is 30 nm or more. On the other hand, if the Ti precipitates become too coarse, they may cause surface defects or fracture during cold rolling. Therefore, it is preferable that the particle diameter of Ti precipitates is 2000 nm or less.

[0093] The particle size of Ti precipitates can be determined by, for example, performing TEM or SEM analysis with a component analysis function, measuring the square root of the major axis diameter and minor axis diameter of 10 or more precipitates that have been confirmed to contain Ti, and calculating the average value. For example, Figure 3 is a measurement example of the particle size of Ti precipitates in a finish-annealed steel sheet, showing an example of Ti precipitates having a particle size of 30 to 2000 nm. Also, Figure 4 is a measurement example of the particle size of Ti precipitates in a finish-annealed steel sheet, showing an example of Ti precipitates having a particle size of less than 30 nm.

[0094] The non-oriented electrical steel sheet according to the embodiment manufactured through the above steps is manufactured using an electric furnace and has a chemical composition of C: 0.0050% by mass or less, Si: 2.00 to 4.50% by mass, Mn: 2.00% by mass or less, Al: 2.50% by mass or less, Ti: 0.0100% by mass or less, P: 0.20% by mass or less, N: 0.0050% by mass or less, O: 0.0050% by mass or less, and S: 0.0030% by mass or less. The particle size of Ti precipitates present in the steel sheet is 30 to 2000 nm.

[0095] The non-oriented electrical steel sheet according to the embodiment preferably has a sheet thickness of 0.30 mm or less and an iron loss W10 / 400 of 13.5 W / Kg or less, and more preferably has a sheet thickness of 0.25 mm or less and an iron loss W10 / 400 of 13.0 W / Kg or less.

[0096] Example 1 A method for manufacturing a non-oriented electrical steel sheet according to the present invention will be described below as Example 1. In this example, a non-oriented electrical steel sheet was manufactured under predetermined conditions.

[0097] First, deoxidized molten steel was produced using iron scrap and / or direct reduced iron as the iron source and tapped from an electric furnace into a ladle. ２ O ３ (Al ２ O ３ :99% by mass), CaO・Al ２ O ３ (CaO: 55% by mass, Al ２ O ３ The ladle was filled with magnesia chrome bricks (MgO: 60 mass%, Cr: 45 mass%) to an inner diameter of 2.9 m. ２ O ３ :25% by mass, TiO ２ : 0.1% by mass) was used as the liner.

[0098] After tapping, vacuum decarburization was carried out in a ladle vacuum degassing system, which stores the ladle in a vacuum tank. CaO was added 4 minutes after the start of the vacuum decarburization process. The amount of CaO added was determined based on the amount of Al generated when deoxidizing the molten steel and slag with Al. ２ O ３ The amount was estimated and 1.2 times that amount was added.

[0099] After the decarburization treatment, metallic Al and various alloy raw materials for adjusting the composition were added in amounts appropriate for deoxidation and composition adjustment, and the mixture was stirred. The ladle was then transported to a tundish for continuous casting, and molten steel was poured into the tundish for casting. When approximately half of the molten steel in the ladle was poured into the tundish, a sample of the molten steel in the tundish was taken and subjected to composition analysis.

[0100] Table 1 shows the chemical composition of the slab in this example. The balance is Fe and unavoidable impurities. The cast slab was directly transported to a tunnel furnace, heated, and then hot-rolled to form a hot-rolled steel sheet, which was then annealed, cold-rolled, and finish-annealed to form a product sheet. Pickling was performed after the hot-rolled sheet annealing if the annealing time was 60 seconds or less, and before the hot-rolled sheet annealing if the annealing time was more than 60 seconds.

[0101]

[0102] From the product sheet obtained as described above, test pieces with a width of 30 mm and a length of 280 mm were taken in the rolling direction and in the direction perpendicular to the rolling direction, and the iron loss W10 / 400 was measured in accordance with "JIS C2550-1." Table 2 shows the manufacturing conditions after the hot rolling process and the iron loss value measured for each test piece.

[0103]

[0104] As shown in Table 2, in Examples 1 to 10 in which the slab composition and manufacturing conditions conform to the present invention, the iron loss W10 / 400 is a good value of 13.0 W / kg or less. On the other hand, in Comparative Examples 1 and 2 in which the slab composition and manufacturing conditions do not conform to the present invention, the iron loss W10 / 400 exceeds 13.0 W / kg.

[0105] Example 2 A method for manufacturing a non-oriented electrical steel sheet according to the present invention will be described below with reference to Example 2. In this example, a non-oriented electrical steel sheet was manufactured under predetermined conditions.

[0106] First, deoxidized molten steel was produced using iron scrap and / or direct reduced iron as the iron source and tapped from an electric furnace into a ladle. ２ O ３ (Al ２ O ３ :99% by mass), CaO・Al ２ O ３ (CaO: 55% by mass, Al ２ O ３ The ladle was filled with magnesia chrome bricks (MgO: 60 mass%, Cr: 45 mass%) to an inner diameter of 2.9 m. ２ O３ :25% by mass, TiO ２ : 0.1% by mass) was used as the liner.

[0107] After tapping, vacuum decarburization was carried out in a ladle vacuum degassing system, which stores the ladle in a vacuum tank. CaO was added 4 minutes after the start of the vacuum decarburization process. The amount of CaO added was determined based on the amount of Al generated when deoxidizing the molten steel and slag with Al. ２ O ３ The amount was estimated and 1.2 times that amount was added.

[0108] After the decarburization treatment, metallic Al and various alloy raw materials for adjusting the composition were added in amounts appropriate for deoxidation and composition adjustment, and the mixture was stirred. The ladle was then transported to a tundish for continuous casting, and molten steel was poured into the tundish for casting. When approximately half of the molten steel in the ladle was poured into the tundish, a sample of the molten steel in the tundish was taken and subjected to composition analysis.

[0109] Tables 3-1 and 3-2 show the chemical compositions of the slabs of this example. The balance is Fe and unavoidable impurities. The cast slabs were directly transported to a tunnel furnace, heated, and subsequently hot-rolled to form hot-rolled steel sheets, which were then annealed, cold-rolled, and finish-annealed to form product sheets. Pickling was performed after hot-rolled sheet annealing when the annealing time was 60 seconds or less, and before hot-rolled sheet annealing when the annealing time exceeded 60 seconds.

[0110]

[0111] Test pieces measuring 30 mm in width and 280 mm in length were taken from the product sheets obtained as described above in the rolling direction and the direction perpendicular to the rolling direction, and the iron loss W10 / 400 was measured in accordance with "JIS C2550-1." Tables 4-1, 4-2, and 4-3 show the manufacturing conditions after the hot rolling process and the iron loss values ​​measured for each test piece.

[0112]

[0113] As shown in Tables 4-1, 4-2, and 4-3, in Examples 13 to 48, in which the slab composition and manufacturing conditions conform to the present invention, the iron loss W10 / 400 is a favorable value of 13.0 W / kg or less. On the other hand, in Comparative Examples 3, 4, 6, 8, and 10 to 12, in which the slab composition and manufacturing conditions do not conform to the present invention, the iron loss W10 / 400 exceeds 13.0 W / kg. Note that steel sheets Nos. 20, 25, and 30 were fractured during the cold rolling process, and therefore were not subjected to finish annealing, and the iron loss W10 / 400 was not measured; therefore, they are designated as Comparative Examples 5, 7, and 9.

[0114] As described above, according to the method for producing a non-oriented electrical steel sheet of the present invention, CO ２ A non-oriented electrical steel sheet with good high-frequency core loss can be manufactured using an electric furnace-thin slab caster process with low emissions. Furthermore, the non-oriented electrical steel sheet according to the present invention can improve high-frequency core loss.

[0115] The method for producing a non-oriented electrical steel sheet according to the present invention has been specifically described above using the detailed description and examples for carrying out the invention, but the scope of the present invention is not limited to these descriptions and should be broadly interpreted based on the claims. It goes without saying that various changes and modifications based on these descriptions are also included in the scope of the present invention.

Claims

1. A steelmaking process comprising: a refining process for producing molten steel in an electric furnace; a continuous casting process for continuously casting the molten steel to produce slabs; a transport process for directly transporting the slabs to a heating device; a hot rolling process for hot rolling the slabs heated by the heating device to produce hot-rolled steel sheets; a hot-rolled sheet annealing process for hot-rolled steel sheets to produce hot-rolled annealed steel sheets; a cold rolling process for cold-rolling the hot-rolled annealed steel sheets to produce cold-rolled steel sheets; and a finish annealing process for finish annealing the cold-rolled steel sheets. a chemical composition of the slab comprising C: 0.0050% by mass or less, Si: 2.00 to 4.50% by mass, Mn: 2.00% by mass or less, Al: 2.50% by mass or less, Ti: 0.0100% by mass or less, P: 0.20% by mass or less, N: 0.0050% by mass or less, O: 0.0050% by mass or less, and S: 0.0030% by mass or less; and wherein, when the equilibrium precipitation temperature of Ti carbonitrides calculated from the following formula (1) is T0 (°C) and the starting temperature of the hot rolling in the hot rolling step is T1 (°C), T0 and T1 satisfy the following formula (2):

2. The method for producing a non-oriented electrical steel sheet according to claim 1, wherein in the hot rolling step, the heating time of the slab is 30 minutes or less, the end temperature of the hot rolling is 800°C or higher, and the coiling temperature is 500 to 700°C.

3. The method for producing a non-oriented electrical steel sheet according to claim 1, wherein in the hot-rolled sheet annealing step, the annealing temperature is 700 to 1200°C; in the cold-rolling step, the sheet is cold-rolled to a thickness of 0.30 mm or less with a reduction of 95.0% or less; and in the finish annealing step, the annealing temperature is 800 to 1100°C and the sheet is soaked for 2 seconds or more.

4. The method for producing a non-oriented electrical steel sheet according to claim 2, wherein in the hot-rolled sheet annealing step, the annealing temperature is 700 to 1200°C; in the cold-rolling step, the sheet is cold-rolled to a thickness of 0.30 mm or less with a reduction of 95.0% or less; and in the finish annealing step, the annealing temperature is 800 to 1100°C and the sheet is soaked for 2 seconds or more.

5. In addition to the above chemical composition, the slab contains one or more of Sn and Sb in total of 0.100 mass% or less, Ca: 0.010 mass% or less, Mg: 0.0050 mass% or less, Ce: 0.010 mass% or less, La: 0.010 mass% or less, Nd: 0.010 mass% or less, Y: 0.010 mass% or less, Cu: 2.0 mass% or less, Ni: 1.0 mass% or less, Cr: 1.0 mass% or less, Mo: 0.10 mass% or less, Nb: 0.010 mass% or less, V:

0.

2. The method for producing a non-oriented electrical steel sheet according to claim 1, wherein the steel sheet contains at least one of: 1.0 mass% or less of Si: 0.0100 mass% or less, W: 0.05 mass% or less, Ta: 0.05 mass% or less, Co: 1.0 mass% or less, B: 0.0100 mass% or less, Pb: 0.0100 mass% or less, Zn: 0.10 mass% or less, As: 0.010 mass% or less, Zr: 0.010 mass% or less, Bi: 0.010 mass% or less, Ge: 0.05 mass% or less, and Ga: 0.05 mass% or less.

6. A method for producing a non-oriented electrical steel sheet according to claim 1 or claim 5, wherein the sheet thickness is 0.30 mm or less and the iron loss W10 / 400 is 13.5 W / Kg or less.

7. A method for producing a non-oriented electrical steel sheet according to claim 1 or claim 5, wherein the sheet thickness is 0.25 mm or less and the iron loss W10 / 400 is 13.0 W / Kg or less.

8. A method for producing a non-oriented electrical steel sheet according to claim 1 or claim 5, which includes a refining step of producing molten steel using an electric furnace and a vacuum decarburization apparatus in which a ladle is housed inside a vacuum tank.

9. A non-oriented electrical steel sheet manufactured using an electric furnace, having a chemical composition of C: 0.0050% by mass or less, Si: 2.00 to 4.50% by mass, Mn: 2.00% by mass or less, Al: 2.50% by mass or less, Ti: 0.0100% by mass or less, P: 0.20% by mass or less, N: 0.0050% by mass or less, O: 0.0050% by mass or less, S: 0.0030% by mass or less, and the particle size of the Ti precipitates present in the steel sheet is 30 to 2000 nm.

10. A non-oriented electrical steel sheet according to claim 9, having a thickness of 0.30 mm or less and an iron loss W10 / 400 of 13.5 W / Kg or less.

11. The non-oriented electrical steel sheet according to claim 9, having a thickness of 0.25 mm or less and an iron loss W10 / 400 of 13.0 W / Kg or less.

12. Produced using an electric furnace, the composition of the alloy is C: 0.0050% by mass or less, Si: 2.00 to 4.50% by mass, Mn: 2.00% by mass or less, Al: 2.50% by mass or less, Ti: 0.0100% by mass or less, P: 0.20% by mass or less, N: 0.0050% by mass or less, O: 0.0050% by mass or less, and S: 0.0030% by mass or less; In addition to the above-mentioned composition, the alloy contains at least one of Sn and Sb in total at 0.100% by mass or less, Ca: 0.010% by mass or less, Mg: 0.0050% by mass or less, Ce: 0.010% by mass or less, La: 0.010% by mass or less, Nd: 0.010% by mass or less, Y: 0.010% by mass or less, Cu: 2.0% by mass or less, Ni: 1.0% by mass or less, Cr: 1.0% by mass or less, Mo: 0.10% by mass or less, Nb: 0.010% by mass or less %, V: 0.10 mass% or less, W: 0.05 mass% or less, Ta: 0.05 mass% or less, Co: 1.0 mass% or less, B: 0.0100 mass% or less, Pb: 0.0100 mass% or less, Zn: 0.10 mass% or less, As: 0.010 mass% or less, Zr: 0.010 mass% or less, Bi: 0.010 mass% or less, Ge: 0.05 mass% or less, and Ga: 0.05 mass% or less, and the particle size of Ti precipitates present in the steel sheet is 30 to 2000 nm.

13. A non-oriented electrical steel sheet according to claim 12, having a thickness of 0.30 mm or less and an iron loss W10 / 400 of 13.5 W / kg or less.

14. The non-oriented electrical steel sheet according to claim 12, having a thickness of 0.25 mm or less and an iron loss W10 / 400 of 13.0 W / kg or less.

15. The non-oriented electrical steel sheet according to claim 9 or 12, which is produced using a vacuum decarburization apparatus in which a ladle is housed inside an electric furnace and a vacuum tank.

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