Non-oriented electrical steel sheet

Abstract

The non-oriented electrical steel sheet includes a steel sheet having a chemical composition comprising, in mass%, 0.0030% or less of C, 1.0-3.5% of Si, 0.10-2.00% of Al, 0.1-2.0% of Mn, 0.20% or less of P, 0.0030% or less of S, 0.0030% or less of N, 0.0030% or less of Ti, 0.0020% or less of B, 0-0.200% of Sn, 0-0.1000% of Sb, and a remainder of Fe and impurities, and satisfies [Sn] + 2 * [Sb] < = 0.200, where [Sn] is the Sn content and [Sb] is the Sb content in mass%, and W is the plate width of the steel sheet. WH / WL, which is the ratio of the maximum value WH to the minimum value WL of iron loss W10 / 400, is 1.10 or less in a W / 10 part, a W / 4 part, and a W / 2 part, said W / 10 part being a part at a W / 10 position of the plate width from the end in the width direction, said W / 4 part being a part at a W / 4 position, and said W / 2 part being a W / 2 position.

Description

Technical Field

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

[0002] This application claims priority based on Tokugan Application No. 2022-157340 filed in Japan on September 30, 2022, the contents of which are incorporated herein by reference. Background Art

[0003] In the field of electric motors, especially in the field of electric equipment such as compressors for air conditioners and refrigerators, small and medium-sized transformers, and electrical equipment, the demand for higher efficiency and smaller size of electric motors is increasing in line with the global movement to save the global environment, represented by power reduction, energy saving, and reduction of CO2 emissions.

[0004] In the automotive field, non-oriented electromagnetic steel sheets are used as cores for driving motors of hybrid vehicles or electric vehicles. Domestic and foreign automobile manufacturers are openly increasing production of such electric vehicles, and the demand for the non-oriented electromagnetic steel sheets used is also increasing significantly.

[0005] In this context, as well as improving the magnetic properties of non-oriented electromagnetic steel sheets used as core materials for electric motors, it is also important to make the magnetic properties of the steel sheets uniform in the width direction. The reason is that due to the deviation of the magnetic properties in the width direction, a torque called cogging torque is generated when the motor rotates, which causes uneven rotation and noise when the motor rotates. On the other hand, to avoid the generation of this cogging torque, there is a technical problem that the length of the hoop that can be used from the coil needs to be shortened.

[0006] As a method for improving the magnetic properties of non-oriented electrical steel sheets, it is known in the past to add alloy elements such as Si, reduce impurity elements such as C, S, and N, and further control the annealing temperature through the final annealing process after cold rolling to control the grain size to an appropriate level. During the final annealing, if the annealing temperature is high, residual strain that affects the magnetic properties will be generated in the cooling process after annealing. This strain will hinder the movement of the magnetic wall when the magnetic field is applied, thereby affecting the magnetic properties. The residual strain is not uniform in the width direction, so that the magnetic properties in the width direction are biased.

[0007] In the case of general-purpose varieties of non-oriented electromagnetic steel sheets, the final annealing temperature is low. Therefore, the cooling rate after the final rolling temperature is slow, and the residual strain introduced into the steel sheet is small. As a result, the deviation of the magnetic properties in the width direction is small. On the other hand, in the case of advanced varieties, in order to reduce iron loss by coarsening the crystal grain size, it is necessary to increase the final annealing temperature, and the cooling rate of the non-oriented electromagnetic steel sheet becomes faster, thereby increasing the residual strain introduced into the steel sheet and causing deviations in the width direction. As a result, the deviation of the magnetic properties in the width direction becomes larger.

[0008] To solve such a technical problem, a method for inexpensively manufacturing a non-oriented electrical steel sheet without in-plane anisotropy is disclosed in Patent Document 1. Patent Document 1 discloses obtaining a non-oriented electrical steel sheet having uniformly controlled magnetic properties at various angles from the rolling direction to the width direction of the sheet.

[0009] However, in order to achieve the above technical problem, Patent Document 1 assumes that rapid heating is performed in the final annealing, and that a γ phase transformation is induced in the reaching temperature range above the Ac3 point by rapid heating. That is, the object is limited to the components of the phase transformation system (the component system that undergoes an α→γ phase transformation by heating).

[0010] In addition, Patent Document 2 discloses a method for manufacturing an electromagnetic steel sheet having uniform magnetic properties in the width direction of a steel coil, characterized in that, when manufacturing the electromagnetic steel sheet through a series of steps consisting of a hot rough rolling process for performing rough rolling on a steel billet for hot rough rolling of the electromagnetic steel sheet, winding the obtained thin steel sheet into a steel coil, followed by a hot rolling process for final rolling while unwinding, a cold rolling process for performing one or more cold rolling with intermediate annealing to obtain a final plate thickness, and a magnetic treatment process for performing a primary recrystallization annealing or a primary recrystallization annealing and a secondary recrystallization annealing to allow the product to exhibit final magnetic properties, in the rough rolling stage of the above-mentioned hot rolling process, the plate thickness in the width direction of the thin steel sheet is controlled so that the plate thickness at the end portions in the width direction and the plate thickness at the center portion in the width direction satisfy a prescribed relationship, and then the thin steel sheet is coiled.

[0011] However, in Patent Document 2, the thin steel sheet after hot rough rolling needs to be coiled, which has a problem of increasing the number of steps. In addition, the control of the magnetic property deviation in the sheet width direction is also insufficient.

[0012] Prior art literature

[0013] Patent Literature

[0014] Patent Document 1: Japanese Patent Application Laid-Open No. 07-054052

[0015] Patent Document 2: Japanese Patent Application Laid-Open No. 09-316536 Summary of the invention

[0016] Technical problem to be solved by the invention

[0017] Conventionally, in non-oriented electrical steel sheets with a non-transformation chemical composition (one that does not undergo α→γ transformation by heating), the variation in magnetic properties in the sheet width direction has not been adequately controlled. Therefore, a technology that can make magnetic properties uniform without increasing the number of steps is sought.

[0018] In view of the above needs, the present invention aims to provide a non-oriented electrical steel sheet having good magnetic properties and small deviation in magnetic properties in the width direction, in which Si content is 1.0% to 3.5% and the soaking temperature in the final annealing is as high as 850°C or more (i.e., low iron loss is required).

[0019] Technical means for solving technical problems

[0020] In order to solve the above technical problems, the inventors of the present invention have conducted in-depth research on the influence of chemical composition or manufacturing conditions on the deviation of magnetic properties in the width direction. As a result, the following findings were obtained: by controlling the cooling rate to control the distribution of precipitates in the width direction, and by controlling the length between the hearth rolls in the soaking zone, the tension applied to the steel sheet, and the cooling rate after the final annealing process in the final annealing process, the deviation of magnetic properties in the width direction of the steel sheet can be reduced.

[0021] The present invention has been achieved based on the above findings, and its gist is as follows.

[0022] [1] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises a steel sheet, wherein the chemical composition of the steel sheet is, by mass%, C: 0.0030% or less, Si: 1.0-3.5%, Al: 0.10-2.00%, Mn: 0.1-2.0%, P: 0.20% or less, S: 0.0030% or less, N: 0.0030% or less, Ti: 0.0030% or less, B: 0.0020% or less, Sn: 0-0.200%, Sb: 0-0.10 00%, and the remainder: Fe and impurities, when the Sn content in mass % is [Sn] and the Sb content is [Sb], the following formula (1) is satisfied, when the plate width of the steel plate is W, the portion at the W / 10 position of the plate width, i.e., the W / 10 portion, the portion at the W / 4 position, i.e., the W / 4 portion, and the portion at the W / 2 position, i.e., the W / 2 portion, from the end in the width direction, and the ratio of the maximum value WH to the minimum value WL of the iron loss W10 / 400, i.e., WH / WL, is 1.10 or less

[0023] [Sn]+2×[Sb]≦0.200(1).

[0024] [2] In the non-oriented electrical steel sheet described in [1], the [Sn] and the [Sb] may satisfy the following formula (2):

[0025] 0.020≦[Sn]+2×[Sb]≦0.200(2).

[0026] [3] In the non-oriented electrical steel sheet according to [1] or [2], an insulating film may be formed on a surface of the steel sheet.

[0027] Effects of the Invention

[0028] According to the above aspects of the present invention, it is possible to manufacture a non-oriented electrical steel sheet having a phase-change system or a non-phase-change system chemical composition, excellent magnetic properties, and small variation in magnetic properties in the width direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram showing the relationship between the parameter PT in the soaking zone of the final annealing furnace and the deviation of the magnetic properties in the width direction. DETAILED DESCRIPTION

[0030] A non-oriented electromagnetic steel sheet according to an embodiment of the present invention (hereinafter sometimes referred to as "the electromagnetic steel sheet according to the present embodiment") is described. The electromagnetic steel sheet according to the present embodiment includes a steel sheet. The electromagnetic steel sheet according to the present embodiment may be composed of only a steel sheet, or may have an insulating coating on the surface (one side or both sides) of the steel sheet.

[0031] In addition, the electromagnetic steel sheet of the present embodiment has a chemical composition, in mass%, of C: 0.0030% or less, Si: 1.0 to 3.5%, Al: 0.10 to 2.00%, Mn: 0.1 to 2.0%, P: 0.20% or less, S: 0.0030% or less, N: 0.0030% or less, Ti: 0.0030% or less, B: 0.0020% or less, Sn: 0 to 0.200%, Sb: 0 to 0.1000%, and the remainder: F e and impurity composition, when the Sn content in mass % is set to [Sn] and the Sb content is set to [Sb], [Sn]+2×[Sb]≦0.200 is satisfied, and when the plate width of the steel plate is set to W, at the ends in the width direction, the part at the W / 10 position of the plate width, i.e. the W / 10 part, the part at the W / 4 position, i.e. the W / 4 part, and the part at the W / 2 position, i.e. the W / 2 part, WH / WL, which represents the ratio of the maximum value WH to the minimum value WL of the iron loss W10 / 400, is less than 1.10.

[0032] Next, the electromagnetic steel sheet and the manufacturing method according to the present embodiment will be described.

[0033] <Steel Plate>

[0034] The steel plate (also referred to as a base steel plate) included in the non-oriented electrical steel plate will be described.

[0035] [Chemical composition]

[0036] The reasons for limiting the chemical composition of the steel sheet of the electromagnetic steel sheet of the present embodiment (when the non-oriented electromagnetic steel sheet is composed only of the steel sheet, it can also be considered as the chemical composition of the non-oriented electromagnetic steel sheet) are explained. The "%" of the content of each element constituting the chemical composition means "mass %" unless otherwise specified.

[0037] C: 0.0030% or less

[0038] C is the cause of magnetic aging and is an element that increases iron loss. In addition, C is an element that has a large influence on the deviation of magnetic properties. Therefore, the C content is set to 0.0030% or less. The C content is preferably 0.0025% or less, and more preferably 0.0020% or less.

[0039] The lower the C content, the better, and it may be 0%. However, excessive reduction of the C content leads to increased costs, so the C content may be made 0.0005% or more.

[0040] Si: 1.0~3.5%

[0041] Si is an element that increases the resistance of the steel sheet, reduces eddy current loss, and reduces iron loss. In addition, it is also an element that has a great influence on the deviation of magnetic properties. When the Si content is less than 1.0%, the resistance of the steel sheet will not increase and the iron loss will not decrease. Therefore, the Si content is set to 1.0% or more. The Si content is preferably 1.8% or more, and more preferably 2.0% or more.

[0042] On the other hand, when the Si content exceeds 3.5%, the magnetic flux density and punching workability are significantly reduced, and the manufacturing cost increases. Therefore, the Si content is set to 3.5% or less. The Si content is preferably 3.3% or less, and more preferably 3.2% or less.

[0043] Al: 0.10~2.00%

[0044] Al is an element that is inevitably mixed from ore or refractory, contributes to deoxidation, and, like Si, has the effects of increasing resistance, reducing eddy current loss, and reducing iron loss.

[0045] When the Al content is less than 0.10%, fine AlN is formed, which adversely affects the iron loss, so the Al content is 0.10% or more, preferably 0.20% or more, and more preferably 0.50% or more.

[0046] On the other hand, when the Al content exceeds 2.00%, the saturation magnetic flux density decreases, and the magnetic flux density decreases, so the Al content is set to 2.00% or less. The Al content is preferably 1.50% or less, and more preferably 1.20% or less.

[0047] Mn: 0.1~2.0%

[0048] Mn is an element having the functions of increasing the electrical resistance, reducing the eddy current loss, and suppressing the precipitation of fine sulfides such as MnS which are harmful to the growth of crystal grains.

[0049] If the Mn content is less than 0.1%, the effect cannot be fully obtained. Therefore, the Mn content is set to 0.1% or more. The Mn content is preferably 0.2% or more, and more preferably 0.4% or more.

[0050] On the other hand, when the Mn content exceeds 2.0%, the growth of grains during annealing decreases and the iron loss increases. Therefore, the Mn content is set to 2.0% or less. The Mn content is preferably 1.5% or less, more preferably 1.2% or less.

[0051] P: 0.20% or less

[0052] When the content of P exceeds 0.20%, the toughness of the steel plate decreases and the steel plate is prone to fracture. Therefore, the P content is set to 0.20% or less. The P content is preferably 0.15% or less, and more preferably 0.12% or less. The lower limit of the P content is not particularly limited (it can also be 0%), and if the manufacturing cost is taken into consideration, 0.001% is the actual lower limit.

[0053] S: 0.0030% or less

[0054] S is an element that forms fine sulfides such as MnS, which hinders recrystallization and grain growth during final annealing. When the S content is higher than 0.0030%, recrystallization and grain growth during final annealing are significantly hindered, and the magnetic properties are reduced. Therefore, the S content is set to 0.0030% or less. The S content is preferably 0.0020% or less, and more preferably 0.0015% or less. The lower limit of the S content is not particularly limited (it can also be 0%), but if industrial purification technology is considered, 0.0001% is the lower limit, and if manufacturing costs are considered, 0.0003% is the actual lower limit.

[0055] N: 0.0030% or less

[0056] N is an element that forms precipitates and increases iron loss. When the N content exceeds 0.0030%, the iron loss increases significantly. Therefore, the N content is set to 0.0030% or less. The N content is preferably 0.0020% or less, and more preferably 0.0015% or less. The lower limit of the N content is not particularly limited (it can also be 0%), but if the manufacturing cost is taken into consideration, 0.0005% is the actual lower limit.

[0057] Ti: 0.0030% or less

[0058] Ti is an element that forms precipitates and increases iron loss. When the Ti content is higher than 0.0030%, the iron loss increases significantly, so the Ti content is set to 0.0030% or less. The Ti content is preferably 0.0020% or less, and more preferably 0.0015% or less. The lower limit of the Ti content is not particularly limited (it can also be 0%), but if the manufacturing cost is taken into consideration, 0.0005% is the actual lower limit.

[0059] B: 0.0020% or less

[0060] B is an element that forms precipitates and increases iron loss. When the B content is higher than 0.0020%, the iron loss increases significantly. Therefore, the B content is set to 0.0020% or less. The B content is preferably 0.0010% or less, more preferably 0.0005% or less. The lower limit of the B content is not particularly limited (it can also be 0%), but if industrial purification technology is taken into consideration, 0.0001% is the actual lower limit.

[0061] Sn: 0~0.200%

[0062] Sb: 0~0.1000%

[0063] Sn and Sb are elements that suppress surface nitridation and contribute to reducing iron loss. Therefore, the electromagnetic steel sheet of the present embodiment may further contain one or both of Sn and Sb in the chemical composition of the steel sheet.

[0064] Sn and Sb are elements having similar effects, but the degree of their influence is different. Therefore, when the Sn content in mass % is denoted as [Sn] and the Sb content is denoted as [Sb], the range of [Sn]+2×[Sb] is controlled.

[0065] Specifically, in order to obtain the effect of improving the magnetic properties, [Sn]+2×[Sb] is preferably set to 0.020 or more, and more preferably 0.050 or more.

[0066] On the other hand, when [Sn] + 2 × [Sb] exceeds 0.200, the toughness of the steel sheet deteriorates. Therefore, [Sn] + 2 × [Sb] is set to 0.200 or less, preferably 0.100 or less.

[0067] The contents of Sn and Sb are within the range satisfying [Sn]+2×[Sb]≦0.200, with the Sn content being 0 to 0.200% and the Sb content being 0 to 0.1000%.

[0068] The rest: Fe and impurities

[0069] In the electromagnetic steel sheet of the present embodiment, the remainder other than the above elements may be Fe and impurities. Impurities are elements mixed into the steel raw material and / or during the steelmaking process, and are elements permitted within a range that does not hinder the properties of the electromagnetic steel sheet of the present embodiment.

[0070] On the other hand, other elements may be further contained in place of a part of Fe. For example, Cu or Ni may be contained as long as each does not exceed 0.1%. Other elements may be contained in a range of not more than 0.05%.

[0071] The chemical composition of the steel plate can be determined by general analytical methods for steel. For example, the chemical composition can be determined using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, the chemical composition is determined by measuring a test piece extracted from the steel plate in a specified measuring device under conditions based on a pre-made calibration line. C and S are measured using the combustion-infrared absorption method, and N is measured using the inert gas melting-heat conduction method.

[0072] When there is an insulating film on the surface, it may be removed mechanically using a Minitor grinder or the like before analysis.

[0073] <Ratio of the maximum value WH and the minimum value WL of the iron loss W10 / 400, i.e. WH / WL (magnetic property variation): 1.10 or less>

[0074] The electromagnetic steel sheet of the present embodiment has a small variation in magnetic properties in the width direction of the steel sheet. Specifically, the non-oriented electromagnetic steel sheet has a steel sheet width of W, and when W10 / 400 (a measured value of iron loss at 400 Hz at a magnetic flux density of 1.0 T) is measured by the SST method (Single Sheet Tester method) specified in JIS C 2556:2015 at a portion at a position W / 10 of the width, a portion at a position W / 4, and a portion at a position W / 2, W / 400 (a measured value of iron loss at 400 Hz at a magnetic flux density of 1.0 T) at a distance from the end portion in the width direction, and the ratio WH / WL (variation in magnetic properties) of the maximum value WH and the minimum value WL is obtained, WH / WL is 1.10 or less.

[0075] When WH / WL is higher than 1.10, the cogging torque, i.e., the rotational unevenness, increases when the non-oriented electromagnetic steel sheets are laminated to form a motor, and the noise during the rotation increases, which is not preferable. Therefore, by controlling the magnetic characteristic deviation WH / WL to be less than 1.10, the cogging torque, i.e., the rotational unevenness, can be reduced, and the noise during the rotation can also be reduced (for example, to less than 40db).

[0076] The suppression of magnetic property variation in the width direction is considered to be achieved by controlling the distribution of inclusions or the strain state of micro-regions, but it is not easy to evaluate them accurately. Therefore, the electromagnetic steel sheet of the present embodiment is characterized by the WH / WL designation.

[0077] In addition, in this embodiment, the value of other iron loss such as W15 / 50 is not specified, but the ratio of the maximum value WH to the minimum value WL of W10 / 400 is specified. W10 / 400 is a characteristic required in the equipment assumed to be used, but it is difficult to control compared with other iron loss values ​​such as W15 / 50 because it is easily affected by residual strain, and the imbalance is likely to become larger. Therefore, for example, even if the ratio of the maximum value to the minimum value of W15 / 50 is less than 1.10, WH / WL is not necessarily less than 1.10.

[0078] In the W / 10 section, W10 / 400 is measured by the SST method (single plate test method) specified in JIS C 2556:2015, which means that a 55 mm square sample is used to include the W / 10 section in the sample, and the W10 / 400 is measured by the SST method using the sample. The same applies to the measurement of the W / 4 section and the W / 2 section.

[0079] Furthermore, in the electromagnetic steel sheet of the present embodiment, even in the case of a lower magnetic field, it is preferable that the variation in magnetic properties in the width direction is small.

[0080] For example, in the W / 10 part, W / 4 part, and W / 2 part, when W5 / 400 is measured by the SST method specified in JIS C 2556:2015 and the ratio of the maximum value WH2 to the minimum value WL2, i.e. WH2 / WL2 (deviation of magnetic properties), is obtained, it is preferred that WH2 / WL2 is less than 1.10.

[0081] WH2 / WL2 can be measured in the same manner as WH / WL.

[0082] The wider the width of the steel sheet (sheet width), the greater the deviation of the magnetic properties in the width direction tends to be. However, in the electromagnetic steel sheet of the present embodiment, at least when the width is 1000 mm or less, the deviation of the magnetic properties can be reduced as described above. By performing stricter control, the deviation of the magnetic properties can be reduced when the width is 1300 mm or less.

[0083] <Insulation coating>

[0084] The electromagnetic steel sheet of the present embodiment may have an insulating film formed on the surface of the steel sheet.

[0085] The insulating film may be any known film, and for example, a film composed of Al 2 O 3 is exemplified.

[0086] <Method for producing non-oriented electrical steel sheet>

[0087] The method for producing the electromagnetic steel sheet of the present embodiment is not particularly limited, but includes the following steps, and a method in which each step is performed under preferred conditions is preferred.

[0088] (I) a hot rolling process of heating a steel slab and hot rolling it to obtain a hot-rolled plate;

[0089] (II) a hot rolled sheet annealing step for annealing the hot rolled sheet (steel coil);

[0090] (III) a cold rolling step of pickling and cold rolling the hot rolled sheet after the hot rolled sheet annealing step to obtain a cold rolled sheet;

[0091] (IV) A final annealing step of final annealing the cold-rolled sheet.

[0092] In addition, the following steps may be further included.

[0093] (V) An insulating film forming step of forming an insulating film on the steel sheet (non-oriented electrical steel sheet) after the final annealing step.

[0094] Preferred conditions for each step are described below, and known conditions can be applied to conditions not described.

[0095] [Hot rolling process]

[0096] In the hot rolling process, the steel slab is heated and hot rolled to obtain a hot rolled sheet, which is then wound into a coil.

[0097] The chemical composition of the steel slab to be used may be determined according to the chemical composition of the steel sheet to be finally obtained as the non-oriented electrical steel sheet.

[0098] The heating temperature of the steel billet is preferably set to 1050-1250°C. When it is less than 1050°C, the coiling temperature cannot be ensured to be above a certain temperature, resulting in the deterioration of the magnetic properties of the product. On the other hand, when the heating temperature exceeds 1250°C, there is a situation where the precipitate is excessively dissolved, and fine precipitation occurs during hot rolling, resulting in the deterioration of the iron loss of the product. More preferably, the heating temperature of the steel billet is 1100-1200°C.

[0099] In addition, the temperature of the final stand of the hot rolling (finishing rolling temperature) is preferably in the range of 800 to 1000°C. This is because it is difficult to set the coiling temperature of the steel coil to the range described below when it is outside this range. The finishing rolling temperature is more preferably 820 to 950°C, and even more preferably 900 to 1000°C.

[0100] If the hot-rolled sheet is too thick, the magnetic properties of the product sheet deteriorate, and if it is too thin, the required temperature cannot be ensured, so it is preferably 1.6 to 2.8 mm, more preferably 1.8 to 2.5 mm.

[0101] The coiling temperature during hot rolling is preferably in the range of 650 to 900°C. When the coiling temperature is set to less than 650°C, the final rolling temperature is lowered and the rolling load may increase, and when the coiling temperature is higher than 900°C, the surface of the coil may be oxidized and the appearance may deteriorate. The more preferred range of the coiling temperature is 680 to 850°C, and the more preferred range is 700 to 800°C.

[0102] [Hot rolled sheet annealing process]

[0103] In the hot-rolled plate annealing process, the hot-rolled plate that has been hot-rolled is annealed (hot-rolled plate annealing). The soaking temperature is preferably 850 to 1000°C. When the soaking temperature is less than 850°C, the magnetic properties may sometimes deteriorate. On the other hand, when the soaking temperature is higher than 1000°C, the toughness may decrease. The more preferred range of the soaking temperature is 900°C to 950°C. In addition, the soaking time is preferably set to 10 to 180 seconds. Considering the magnetic properties and productivity, the soaking time is more preferably set to 15 to 120 seconds. Annealing can be carried out in the form of a steel coil, but it can also be annealed after unwinding as needed.

[0104] [Cold rolling process]

[0105] After the hot rolled sheet annealing step, the hot rolled sheet is uncoiled from the coil, pickled under known conditions, and then cold rolled. The cold rolling may be a single cold rolling (a series of cold rolling without intermediate annealing) or two or more cold rollings with intermediate annealing.

[0106] The thickness of the cold-rolled sheet after the cold-rolling process (same as the base steel sheet of the final product) is preferably 0.20 to 0.50 mm from the viewpoint of magnetic properties. In consideration of productivity, the thickness of the cold-rolled sheet is more preferably in the range of 0.25 to 0.50 mm.

[0107] The total rolling reduction in the final cold rolling step is preferably 75 to 90% from the viewpoint of magnetic properties, and more preferably 80 to 88% in consideration of magnetic properties and productivity.

[0108] [Final annealing process]

[0109] In the final annealing step, the cold-rolled steel sheet (cold-rolled sheet) is subjected to final annealing.

[0110] The heating conditions in the final annealing step are not particularly limited. The soaking temperature during the final annealing is preferably 950 to 1100°C, and more preferably 1000 to 1100°C from the perspective of magnetic properties. Regarding the annealing time, the soaking time is preferably 10 to 180 seconds. Considering magnetic properties and productivity, the soaking time is more preferably 15 to 60 seconds.

[0111] In addition, in the final annealing process, annealing is performed in a continuous annealing furnace, and the plate width of the cold-rolled plate for final annealing is set to W (mm), the plate thickness is set to t (mm), the length between the hearth rolls of the soaking zone in the continuous annealing furnace (the distance between the centers of adjacent hearth rolls) is set to L (m), the tension applied to the steel plate during annealing is set to T (MPa), and the average cooling rate from the end of soaking to 650°C is set to Vc (°C / second). The final annealing is performed in a manner such that PT=W×t×L×T / Vc>100.

[0112] By setting PT to be higher than 100, the magnetic property deviation in the width direction can be reduced (1.10 or less). The upper limit of PT is not limited, and may be, for example, 1000 or less. PT may be 200 or more, or 400 or more.

[0113] The reason why PT is set to be higher than 100 will be described based on an experimental example conducted by the inventors of the present invention.

[0114] (Experimental Example 1)

[0115] A steel billet containing, by mass%, C: 0.001%, Si: 3.0%, Al: 0.50%, Mn: 0.2%, P: 0.010%, S: 0.0100%, N: 0.0010%, Ti: 0.0010%, and B: 0.0010% was heated to 1160°C and then hot-rolled at a finishing temperature of 850°C to produce a hot-rolled sheet having a sheet thickness of 2.0 mm. The hot-rolled sheet was coiled at 650°C (coiling temperature) into a steel coil.

[0116] The coil was unwound, heated to 1000°C, held at that temperature for 60 seconds, and thereafter coiled and air-cooled.

[0117] The steel coil was unwound, pickled, and then cold-rolled to produce a cold-rolled sheet having a sheet width of 1000 mm and a sheet thickness of 0.50 mm.

[0118] The cold-rolled sheet was heated to 1000° C. (soaking temperature) and maintained (soaking) for 30 seconds to perform final annealing.

[0119] During the final annealing, the length L between the bottom rolls in the soaking zone is changed to 2.0-5.0 m, and the tension T applied to the steel sheet is changed to 2-6 N / mm. 2 , change the average cooling rate Vc from the end of soaking to 650°C to 4~10°C / second.

[0120] From the steel plate after the final annealing, 55 mm square specimens were cut from each of the W / 10 part, W / 4 part, and W / 2 part, and W10 / 400 (the measured value of the iron loss at 400 Hz under a magnetic flux density of 1.0 T) was measured using the SST method (single plate test method) of JIS C 2556:2015, and the ratio of the maximum value WH to the minimum value WL was set as the magnetic property deviation.

[0121] As a result, as shown in FIG. 2 , by setting PT to be higher than 100, WH / WL can be controlled to be 1.10 or less.

[0122] Therefore, in the method for producing an electromagnetic steel sheet according to the present embodiment, the final annealing is performed so that the PT is higher than 100.

[0123] The reason why it is preferred to increase the distance between the hearth rollers is presumed to be that if the distance between the hearth rollers is lengthened, the catenary of the steel plate in the width direction becomes larger, and a large strain is applied uniformly in the width direction. The residual strain caused by cooling is smaller than the strain entering through the catenary, so even if the residual strain caused by cooling enters unevenly in the width direction, it is considered that its influence is small.

[0124] In addition, the reason for preferably increasing the tension is that by increasing the tension, a large strain is uniformly applied in the width direction. Generally, when the tension is increased, the catenary is slightly reduced, but the iron loss degradation caused by the extension of the steel plate itself has a large impact. The residual strain caused by cooling is smaller than the strain introduced by increasing the tension, so even if the residual strain caused by cooling enters unevenly in the width direction, it is considered that its impact is small.

[0125] On the other hand, the reason why the average cooling rate to 650° C. after soaking in the final annealing is preferably smaller is presumed to be that when the average rate becomes larger, the influence of residual strain due to cooling cannot be ignored, and the variation of magnetic properties in the width direction becomes larger.

[0126] Even if the recrystallization rate is controlled by, for example, hot-rolled sheet annealing before the final annealing step to reduce the variation in recrystallization rate due to the position of the steel sheet, if the subsequent steps are not adequately controlled, the magnetic properties will become uneven. Therefore, the cold rolling conditions or the final annealing are very important.

[0127] In order to achieve a predetermined magnetic property variation even when the plate width is wider, the soaking temperature in the final annealing step is preferably increased, and is preferably set to 1000° C. or higher, for example.

[0128] In order to reduce the variation in low-field iron loss, PT is preferably set to 600 or more, more preferably set to 700 or more.

[0129] [Insulation film forming step]

[0130] When the electromagnetic steel sheet of the present embodiment is made into a non-oriented electromagnetic steel sheet having an insulating film on the surface of the steel sheet (base steel sheet), in addition to the above-mentioned steps, an insulating film forming step of forming an insulating film on the surface of the steel sheet after the final annealing step can be provided, similarly to the conventional manufacturing step of the non-oriented electromagnetic steel sheet. The conditions of the insulating film forming step can be the same as those of the conventional insulating film forming step of the non-oriented electromagnetic steel sheet.

[0131] Example

[0132] After casting a steel billet with adjusted chemical composition, it is heated and hot-rolled under any of the conditions in Table 2 to produce a hot-rolled sheet, which is then coiled.

[0133] The hot-rolled sheets were annealed under any of the conditions in Table 2 and cooled to room temperature.

[0134] Thereafter, the steel sheet was pickled and cold-rolled to obtain a steel sheet (cold-rolled sheet) having a thickness of 0.25 to 0.50 mm.

[0135] The steel sheets (cold-rolled sheets) were subjected to final annealing under any of the conditions shown in Table 2 to obtain non-oriented electrical steel sheets. An insulating film was formed on the surface of some of the non-oriented electrical steel sheets.

[0136] When the chemical composition of the steel sheet included in the obtained non-oriented electrical steel sheet was measured, it was found that the chemical components shown in Table 1 were contained, and the remainder was Fe and impurities.

[0137] For non-oriented electrical steel sheets (C1-C20, c1-c20) having any of the chemical compositions shown in Table 1 and manufactured by any of the manufacturing methods shown in Table 2, W10 / 400 (measured value of iron loss at 400 Hz at a magnetic flux density of 1.0 T) at each position of W / 10 section, W / 4 section, and W / 2 section was measured by the SST method (single plate test method) of JIS C 2556:2015. At this time, a sample was used for each of W / 10 section, W / 4 section, and W / 2 section at a certain rolling direction position, and the value thereof was used as the iron loss value at each position. In addition, the ratio of the maximum value WH to the minimum value WL among the iron loss values ​​at each position, that is, WH / WL (deviation of magnetic properties), was calculated.

[0138] In addition, for some examples, as the magnetic characteristic deviation of the iron loss in a lower magnetic field, the ratio WH2 / WL2 of the maximum value WH2 and the minimum value WL2 of W5 / 400 was obtained.

[0139] The above measurement was performed three times at positions where one strip turn was left in the rolling direction, and the values ​​at the positions where WH / WL and WH2 / WL2 were the maximum were shown in the table.

[0140] When the iron loss at each position is 25.0 W / kg or less and WH / WL is 1.10 or less, it is judged that the magnetic properties are good and the variation in the width direction of the magnetic properties is small.

[0141] [Table 1]

[0142]

[0143] [Table 2]

[0144]

[0145] [Table 3]

[0146]

[0147] As shown in Tables 1 to 3, in steel sheets having a predetermined chemical composition and subjected to final annealing under the condition that the parameter PT of the final annealing condition is higher than 100, the magnetic properties are good and the deviation in the width direction is small. In addition, when the PT is higher, the deviation in the width direction of the iron loss is also small in a low magnetic field. In addition, when the soaking temperature of the final annealing is high, the deviation in the width direction of the iron loss is small even when the width is wide.

[0148] On the other hand, in the comparative examples where the chemical composition is outside the range of the present invention and / or outside the preferred range of the production method, the variation in the width direction of the magnetic properties (iron loss) is large.

[0149] Industrial Applicability

[0150] According to the present invention, a non-oriented electrical steel sheet having excellent magnetic properties and small variation in magnetic properties in the width direction can be manufactured.

[0151] Such non-oriented electrical steel sheets can suppress cogging torque, that is, rotational unevenness, when stacked to form an electric motor, and therefore have high industrial applicability.

Claims

1. A non-oriented electromagnetic steel sheet, characterized in that: Including steel plate, The chemical composition of the steel plate is expressed in mass %, C: 0.0030% or less, Si: 1.0-3.5%, Al：0.10～2.00％、 Mn: 0.1-2.0%, P: 0.20% or less, S: 0.0030% or less, N: 0.0030% or less, Ti: 0.0030% or less, B: 0.0020% or less, Sn: 0~0.200%, Sb: 0 to 0.1000%, and The rest: Fe and impurities. When the Sn content in mass % is [Sn] and the Sb content is [Sb], the following formula (1) is satisfied: [Sn]+2×[Sb]≦0.200(1) When the plate width of the steel plate is set to W, at the ends in the width direction, the portion at the W / 10 position of the plate width, i.e. the W / 10 portion, the portion at the W / 4 position, i.e. the W / 4 portion, and the portion at the W / 2 position, i.e. the W / 2 portion, the ratio of the maximum value WH to the minimum value WL of the iron loss W10 / 400, i.e. WH / WL, is less than 1.

10.

2. The non-oriented electrical steel sheet according to claim 1, characterized in that: The [Sn] and the [Sb] satisfy the following formula (2), 0.020≦[Sn]+2×[Sb]≦0.200(2).

3. The non-oriented electrical steel sheet according to claim 1 or 2, characterized in that: An insulating film is formed on the surface of the steel plate.

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