Non-oriented electromagnetic steel sheet, manufacturing method therefor, and

Abstract

Provided are: a novel non-oriented electromagnetic steel sheet which has excellent magnetic resistance and is not susceptible to tensile strain; a method for producing the same; and a rotating electrical machine comprising the same. A non-oriented electromagnetic steel sheet, a method for producing the same, and a rotating electrical machine comprising the same, the non-oriented electromagnetic steel sheet being characterized by having a chemical composition comprising, in mass%, 0.0100% or less of C, 2.6% to 4.5% of Si, 0.10% to 3.00% of Mn, 0.15% or less of P, 0.0040% or less of S, 0.0040% or less of N, 0.10% or more of Al, and the balance of Fe and unavoidable impurities. The present invention relates to a high-strength steel sheet which is characterized in that: 2.00% or less, 0-0.200% of one or more elements selected from among Sn and Sb, 0.001-5.000% of Cr, and a predetermined amount of arbitrary additional elements (Ni, Cu, Ca, Mg, REM, Ti, B, and O), with the remainder being Fe and impurities, and in that the difference in lower yield points before and after aging treatment when the steel sheet is subjected to aging treatment at 100 DEG C for one hour after 8% strain is imparted, A.I. Is less than 40 MPa.

Description

Technical Field

[0001] The present invention relates to a non-oriented electromagnetic steel sheet, a method for manufacturing the same, and a rotating electrical machine including the same. Background Art

[0002] In recent years, global environmental issues have drawn increasing attention, leading to a growing demand for energy conservation. In particular, there has been a strong desire for higher efficiency in electronic devices. Consequently, demand for improved magnetic properties has intensified in non-oriented electromagnetic steel sheets, which are widely used as core materials in motors and other applications. This trend has been particularly pronounced in recent years in motors for electric and hybrid vehicles, as well as compressors, where higher efficiency motors are being pursued.

[0003] Automobile drive motors and the like sometimes experience elevated temperatures during use. If magnetic aging occurs within this temperature range, the magnetic properties will naturally deteriorate over time compared to when the raw materials were first incorporated.

[0004] Furthermore, in automotive drive motors, tensile strain may occur during riveting or when the core is bent into a three-dimensional spiral shape. This can reduce the dimensional accuracy of the product, and as a result, the designed magnetic properties may not be achieved.

[0005] Patent Document 1 aims to provide a core material for a rotating machine having excellent bendability and iron loss characteristics. Specifically, it describes a material obtained by adding 0.01 to 0.1% Ti to ultra-low C steel, thereby completely fixing the C, improving aging resistance, and achieving excellent bendability.

[0006] Patent Document 2 aims to provide a non-oriented electromagnetic steel sheet with excellent strength and magnetic properties suitable as an iron core material for electric vehicle motors at a low cost. Specifically, it proposes: by punching a rotor and a stator from a non-oriented electromagnetic steel sheet with a specific composition and performing stress relief annealing only on the stator, high strength for the rotor and low iron loss for the stator can be achieved at the same time.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 4325235

[0010] Patent Document 2: Japanese Patent No. 5228379 Summary of the Invention

[0011] Technical problem to be solved by the invention

[0012] Various studies have been conducted to develop non-oriented electromagnetic steel sheets with excellent magnetic properties, workability, and strength. However, Patent Document 1 requires the addition of Ti, which can sometimes negatively affect magnetic properties. Furthermore, Patent Document 2 punches the rotor and stator from the same steel sheet and performs stress relief annealing on only the stator. However, if the rotor and stator could be obtained from different steel sheets and combined, or if the presence or absence of stress relief annealing on the rotor and stator could be appropriately selected, product design flexibility would be further increased.

[0013] The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide a novel non-oriented electrical steel sheet having excellent magnetic aging resistance and hardly susceptible to tensile strain, a method for producing the same, and a rotating electrical machine including the same.

[0014] Technical means for solving technical problems

[0015] According to the present invention, the following solutions are provided. [1]

[0017] A non-oriented electrical steel sheet, characterized in that the chemical composition is, in mass %, as follows: C: 0.0100% or less, Si: 2.6% or more and 4.5% or less, Mn: 0.10% or more and 3.00% or less, P: 0.15% or less, S: 0.0040% or less, N: 0.0040% or less, Al: 0.10% or more and 2.00% or less, at least one selected from Sn and Sb: 0 to 0.200%, Cr: 0.001 to 5.000%, Ni: 0 ~5.000%, Cu: 0~5.000%, Ca: 0~0.020%, Mg: 0~0.0200%, and rare earth elements (REM): 0~0.020%, Ti: less than 0.0100%, B: 0%~0.0050%, O: 0%~0.0200%, and the remainder: composed of Fe and impurities, when aging treatment is performed at 100°C for 1 hour after applying 8% strain, the difference in lower yield point before and after aging treatment: AI is less than 40 MPa. [2]

[0019] The non-oriented electrical steel sheet as described in [1] is characterized in that the chemical composition further contains Mo: 0% to 0.0200%. [3]

[0021] The non-oriented electrical steel sheet according to [1] or [2] is characterized in that, in the following formula, Cev≤0.0055% is satisfied,

[0022] Cev = 12 × ([C (mass %)] / 12 + [N (mass %)] / 14 − [B (mass %)] / 11 − [Ti (mass %)] / 48 − [Cr (mass %)] / 104 − [Mo (mass %)] / 192)

[0023] In the above formula, [element symbol (mass %)] represents the content (mass %) of the element in the chemical composition, and 0 is substituted when the element is not contained. [4]

[0025] A method for manufacturing a non-oriented electromagnetic steel sheet according to any one of [1] to [3], characterized in that when the non-oriented electromagnetic steel sheet is manufactured by a process including steelmaking, hot rolling, hot rolled sheet annealing, pickling, cold rolling, final annealing, and overaging treatment, the overaging temperature of the overaging treatment is set to 50°C to 500°C, and the temperature range above 50°C is set to 10 seconds or more, and the chemical composition of the non-oriented electromagnetic steel sheet is, in terms of mass%, C: 0.0100% or less, Si: 2.6% or more and 4.5% or less, Mn: 0.10% or more and 3.00% or less, P: 0.1 5% or less, S: 0.0040% or less, N: 0.0040% or less, Al: 0.10% or more and 2.00% or less, one or more selected from Sn and Sb: 0-0.200%, Cr: 0.001-5.000%, Ni: 0-5.000%, Cu: 0-5.000%, Ca: 0-0.020%, Mg: 0-0.0200%, and rare earth elements (REM): 0-0.020%, Ti: less than 0.0100%, B: 0%-0.0050%, O: 0%-0.0200%, and the balance: Fe and impurities. [5]

[0027] The method for producing a non-oriented electrical steel sheet as described in [4] is characterized in that the chemical composition further contains Mo: 0% to 0.0200%. [6]

[0029] The method for producing a non-oriented electrical steel sheet as described in [4] or [5] is characterized in that, during the overaging treatment, in at least a part of the step of maintaining the steel sheet in a temperature range of 50°C to 500°C, the steel sheet is pressed against a roll having a diameter of less than 500 mm to perform bending. [7]

[0031] The method for producing a non-oriented electrical steel sheet according to any one of [4] to [6], is characterized in that after the overaging treatment, the steel sheet is bent by being pressed against a roll having a diameter of less than 500 mm. [8]

[0033] A method for manufacturing a non-oriented electromagnetic steel sheet as described in any one of [1] to [3], characterized in that when the non-oriented electromagnetic steel sheet is manufactured by a process including steelmaking, hot rolling, hot rolled sheet annealing, pickling, cold rolling, final annealing, and bending, in the bending process, the steel sheet is pressed against a roller having a diameter of less than 500 mm, thereby performing bending, and the chemical composition of the non-oriented electromagnetic steel sheet is, in terms of mass%, C: less than 0.0100%, Si: 2.6% or more and less than 4.5%, Mn: 0.10% or more and less than 3.00%, P: 0.15% or less, S: 0.0040% or less, N: 0.0040% or less, Al: 0.10% or more and 2.00% or less, 0-0.200% of one or more selected from Sn and Sb, 0.001-5.000% of Cr, 0-5.000% of Ni, 0-5.000% of Cu, 0-0.020% of Ca, 0-0.020% of Mg, 0-0.0200% of rare earth elements (REM), less than 0.0100% of Ti, 0-0.0050% of B, 0-0.0200% of O, and the balance consisting of Fe and impurities. [9]

[0035] The method for producing a non-oriented electrical steel sheet as described in [8] is characterized in that the chemical composition further includes Mo: 0% to 0.0200%.

[10]

[0037] A rotating electrical machine, characterized in that it comprises a stator, a rotor, and a housing for accommodating the stator and the rotor, wherein the core material of the stator or the core material of the rotor is the non-oriented electromagnetic steel sheet as described in any one of [1] to [3].

[0038] Effects of the Invention

[0039] The non-oriented electrical steel sheet provided by the present invention has excellent resistance to magnetic aging and is less susceptible to tensile strain. Furthermore, the non-oriented electrical steel sheet can be obtained by the manufacturing method provided by the present invention. Furthermore, the rotating electrical machine provided by the present invention has excellent resistance to magnetic aging and is less susceptible to tensile strain during processing.

[0040] Here, excellent magnetic aging resistance typically means an iron loss degradation rate of less than 0.9. The iron loss degradation rate is the value obtained by dividing the increase in iron loss before and after aging treatment at 200°C for 24 hours by the iron loss before aging treatment.

[0041] The so-called difficulty in generating tensile strain will be described in detail later, but it is equivalent to an AI of less than 40 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram explaining the AI ​​method. DETAILED DESCRIPTION

[0043] Each constituent element of the present invention will be described in detail.

[0044] The reasons for limiting the chemical composition of steel are as follows: In the following description, unless otherwise specified, the content of each element is expressed in mass %, and the description of mass is omitted.

[0045] <C: 0.0100% or less>

[0046] C increases iron loss and causes magnetic aging. Therefore, the C content is set to 0.0100 mass % or less, preferably 0.001 to 0.004 mass %.

[0047] <Si: 2.6% or more, 4.5% or less>

[0048] Si increases the inherent resistivity of steel and also reduces iron loss. To achieve this, a Si content of 2.6% or more is required. On the other hand, if Si exceeds 4.5%, the steel becomes brittle and rollability decreases. Therefore, Si is preferably set at 2.6-4.5%. Preferably, it is 3.0-3.5% by mass.

[0049] <Mn: 0.10% or more, 3.00% or less>

[0050] Mn increases the inherent resistivity of steel and also coarsens sulfides, rendering them harmless. To achieve this effect, a Mn content of 0.10% or more is required. On the other hand, exceeding 3.00% by mass reduces magnetic flux density, increases costs, and increases the likelihood of cracking during cold rolling. Therefore, the Mn content is set between 0.10% and 3.00%. Preferably, it is between 0.1% and 0.5% by mass.

[0051] <P: 0.15% or less>

[0052] P is an element necessary to increase the hardness of the steel sheet and improve the punchability. However, if added in excess of 0.15%, the steel sheet becomes brittle, so the content is set to 0.15% or less, preferably 0.01 to 0.10%.

[0053] <S: 0.0040% or less>

[0054] S is limited to 0.0040% or less. S precipitates in the steel as sulfides, degrading grain growth and iron loss. Exceeding 0.0040% significantly degrades grain growth and iron loss, so the content is limited to 0.004% or less. While there is no specific lower limit, it is difficult to achieve 0.0005% or less using conventional manufacturing methods. Preferably, the content is between 0.0010% and 0.0030%.

[0055] <N: 0.0040% or less>

[0056] When N is contained in large amounts, it forms nitrides and degrades magnetic properties, so the upper limit should be set to 0.0040%. The lower limit is not specifically specified, but considering current steelmaking technology, 0.0001% is practically the lower limit. Preferably, it is 0.0003-0.0020%.

[0057] <Al: 0.10% or more, 2.00% or less>

[0058] Al is effective as a deoxidizing agent and can also coarsen nitrides, rendering them harmless. Also, like Si, it increases the inherent resistivity of steel and reduces iron loss. To achieve these effects, a content of 0.10% or more is necessary. However, exceeding 2.00% causes embrittlement of the steel and reduces rollability. Therefore, Al is preferably set at 0.10-2.00%. Preferably, it is 0.20-1.50%.

[0059] <Sn and Sb: 1 or 2 types, total 0% or more and 0.200% or less>

[0060] Sn and Sb are effective for improving texture and inhibiting nitridation and oxidation during annealing. Furthermore, at 0.005% or more, Sn and Sb inhibit the movement of carbon, improving aging resistance. Excessive amounts saturate these effects, further adversely affecting steel embrittlement and grain growth suppression. Therefore, the content should be kept below 0.200%. Preferably, the content is between 0.030% and 0.150%.

[0061] <Cr: 0.001% or more, 5.000% or less>

[0062] Cr has the ability to form carbides and nitrides, which fixes dissolved carbon and nitrogen, and has the effect of suppressing tensile strain. Therefore, the lower limit is set to 0.001% or above. On the other hand, Cr reduces the saturation magnetic flux density of the steel sheet. If it exceeds 5.000%, the cost of addition will increase, so it is limited to 5.000% or less. Preferably, it is 0.100-4.000%.

[0063] <Ni: 0% or more, 5.000% or less>

[0064] Ni is an effective element for increasing the strength of steel sheets without excessively brittle them. However, because it is expensive, it is added based on the required strength. When added, the upper limit is 5.000% for cost considerations. Preferably, it is 1.000-4.000%.

[0065] <Cu: 0% or more, 5.000% or less>

[0066] Cu increases the hardness of the steel sheet. If the content exceeds 5.000%, the cost of addition becomes a problem, so it is limited to 5.0% or less. Preferably, it is 0.100 to 4.000%.

[0067] <Ca: 0% or more, 0.020% or less>

[0068] Ca is intentionally added to improve grain growth, but because it is expensive, it is added based on the required strength. If added, the upper limit is set to 0.020% or less for cost considerations. Preferably, it is 0.008% or less.

[0069] <Mg: 0% or more, 0.0200% or less>

[0070] Mg is intentionally added to improve grain growth, but because it is expensive, it is added based on the required strength. When added, the upper limit is set to 0.0200% or less for cost considerations. Preferably, it is 0.0080% or less.

[0071] <Rare earth elements (REM): 0% or more, 0.020% or less>

[0072] Rare earth elements are added to improve grain growth by suppressing impurity precipitation, but because they are expensive, their addition is limited to the required strength. When added, the upper limit is set at 0.020% for cost considerations. Preferably, the content is between 0.001% and 0.008%.

[0073] <Ti: less than 0.0100%>

[0074] Ti has the ability to form carbides and nitrides, which fixes dissolved C and dissolved N, and has the effect of suppressing tensile strain. However, Ti forms fine nitrides or carbides, significantly worsening grain growth during stress relief annealing and degrading magnetic properties. Therefore, the content is set to less than 0.0100%. Preferably, it is 0.0030% or less. 0% Ti can be used, but sometimes it is unavoidable to mix in, so it can be 0.0020% or less.

[0075] <B: 0% or more, 0.0050% or less>

[0076] When Al is added, it may precipitate as fine AlN, leading to deterioration of magnetic properties, so B is added simultaneously. If the content exceeds 0.0050%, there is a risk of deterioration of magnetic properties due to excess B, so the upper limit is set to 0.0050%. Preferably, it is 0.0030-0.0040%.

[0077] <O: 0% or more, 0.0200% or less>

[0078] O forms precipitates, hindering grain growth during annealing and degrading magnetic properties, so the content is set to 0.0200% or less. Preferably, it is set to 0.0030% or less. O can be 0%, but sometimes it is unavoidable to mix in, so it can be set to 0.0020% or less.

[0079] <Mo: 0% or more, 0.0200% or less>

[0080] Mo has the ability to form carbides and nitrides, fixes dissolved C and dissolved N, and has the effect of suppressing tensile strain. Therefore, the Mo content can be either 0% or greater, or 0.0030% or greater. However, Mo forms precipitates, hindering grain growth during annealing and degrading magnetic properties, so the content is limited to 0.0200% or less.

[0081] In addition to the above elements, the chemical composition of the non-oriented electrical steel sheet of the present embodiment may contain 0.10% or less each of Nb, V, Zr, Ce, Bi, and W within a range that does not affect various properties of the non-oriented electrical steel sheet.

[0082] <Remainder: Fe and impurities>

[0083] The remainder is Fe and impurities. Impurities refer to elements that are introduced from raw materials such as ore and scrap, or from the manufacturing environment, during industrial production of slabs or steel. Furthermore, the addition of Fe with known elements in anticipation of known effects is not excluded, provided that the effects of the present invention are not lost.

[0084] <Cev>

[0085] Tensile strain originates from solid solution C and solid solution N. Cev, defined by the following formula, is an indicator related to solid solution C and solid solution N. When it is too large, it is believed that tensile strain is likely to occur. Therefore, Cev is preferably ≤ 0.0055%. Cev can also be set to 0.0054% or less, preferably to 0.0025 or less, more preferably to 0.0015 or less, and even more preferably to 0.0000 or less. The lower limit of Cev is not limited, but can be set to -0.5861 or more.

[0086] Cev = 12 × ([C (mass %)] / 12 + [N (mass %)] / 14 − [B (mass %)] / 11 − [Ti (mass %)] / 48 − [Cr (mass %)] / 104 − [Mo (mass %)] / 192)

[0087] In the above formula, [Element Symbol (mass %)] represents the content (mass %) of the element in the chemical composition of the non-oriented electrical steel sheet. For example, [C (mass %)] represents the content (mass %) of C in the chemical composition of the non-oriented electrical steel sheet. If the chemical composition of the non-oriented electrical steel sheet does not contain the element, 0 is substituted.

[0088] <AI less than 40MPa>

[0089] The non-oriented electrical steel sheet of the present embodiment has an AI of less than 40 MPa.

[0090] Here, AI is the abbreviation of Aging Index, sometimes also called aging index. Regarding AI, a tensile specimen of JIS 13 No. B is processed from a steel plate and given an 8% strain, and then aged at 100°C for 1 hour. The AI ​​is calculated based on the difference between the stress in the 8% strain before the aging treatment and the lower yield point after the aging treatment. For the strain, the elongation from that point is expressed as a percentage based on the distance between the original mark points. The test speed at this time is set to 7.2 mm / min. (equivalent to a distance of 60 mm between the original mark points and a strain rate of 0.002 / s) in the stroke control. Figure 1 This is a diagram that schematically illustrates the method of calculating AI. First, a tensile test is performed on the sample, and 8% strain is applied at room temperature (23°C). In addition, the stress when 8% strain is applied is recorded (that is, the stress at 8% strain before aging treatment). Then, the sample after the tensile test is aged at 100°C for 1 hour, and after cooling to room temperature (23°C), the tensile test is performed again to break the sample. Based on the stress-strain curve in the tensile test, the lower yield point after aging treatment is obtained, and the difference from the stress at 8% strain before aging treatment is obtained. At this time, when a clear yield phenomenon and work hardening are observed in the stress-strain curve, the minimum value of the stress after the yield phenomenon and before work hardening is set as the lower yield point. In the case of Figure 1In that case, when work hardening is not clear, the position with the lowest stress between the yield phenomenon and the elongation 2% lower than the elongation at fracture is taken as the lower yield point. Other items related to the measurement are in accordance with JIS Z2241 (2011). When the AI ​​is 40MPa or more, tensile strain will occur during iron core processing, and dimensional accuracy will deteriorate. In addition, magnetic aging will occur, and magnetic properties will deteriorate over time. Generally speaking, the smaller the AI, the better the tensile strain suppression effect and aging resistance. Therefore, with regard to AI, it is preferably 35MPa or less, and more preferably 30MPa or less.

[0091] <Manufacturing Conditions>

[0092] Next, the reasons for limiting the manufacturing conditions in this invention and preferred manufacturing conditions are described. Generally, the manufacturing method of non-oriented electrical steel sheet includes the following steps: steelmaking, slab casting, slab reheating, hot rolling, hot-rolled sheet annealing, pickling, cold rolling, final annealing (finish annealing), overaging and / or bending, and insulation coating. Each step can be performed in the order listed, or the order of the steps can be adjusted as appropriate.

[0093] (Steelmaking)

[0094] The above composition is adjusted by conventional steelmaking methods such as converter steelmaking and degassing.

[0095] (Slab Casting)

[0096] The slab casting for obtaining the steel having the above chemical composition is conventional continuous casting. In order to facilitate the heating of the slab, it is possible to apply the cogging method to the continuous casting of the slab, but this should be avoided as much as possible because it will increase the cost.

[0097] In the production of the slab, a known continuous casting method is used. The initial thickness is not particularly limited, but a slab having a thickness in the range of approximately 150 mm to 300 mm, preferably 200 mm to 250 mm, is produced.

[0098] (Slab reheating)

[0099] The slab reheating temperature before hot rolling is extremely important in the production of non-oriented electrical steel sheets. This is because it is related to the solid solution and precipitation of impurity elements. To prevent the fine precipitation of compounds containing impurity elements, the slab reheating temperature is preferably 1250°C or lower. Of course, if the absolute value of the content of major harmful elements such as S and N can be reduced, the slab heating temperature can be increased, but this is not practical for industrial production.

[0100] (Hot Rolling)

[0101] The hot rolling conditions for non-oriented electrical steel sheets are generally low-temperature extraction and high-temperature rolling. However, by performing intermediate annealing, the coiling temperature does not need to be extremely high. On the contrary, high-temperature rolling is not preferred from the perspective of descaling. Specifically, the conditions for the final hot rolling process are 900°C to 1000°C, the exit temperature 830°C to 900°C, and the coiling temperature 600°C to 700°C.

[0102] (Hot rolled sheet annealing)

[0103] Although hot-rolled sheets can be annealed, even if this annealing is applied, the magnetic properties in the rolling direction will be improved. However, the improvement will not be significant and will result in a significant cost increase. Therefore, the need for application can be determined based on the desired properties.

[0104] (Pickling)

[0105] Hot-rolled or hot-rolled annealed steel can optionally undergo descaling treatment prior to cold rolling or final annealing to remove the oxide layer, also known as scale, formed on the steel sheet. Pickling is the most common descaling method, chemically cleaning the steel sheet surface using aqueous solutions of one or more inorganic acids. While it does not prevent descaling, pickling may not be necessary if the annealing atmosphere is favorable and the surface scale is minimal.

[0106] (Cold Rolled)

[0107] Cold rolling is performed once, or divided into two or more passes with annealing. Single cold rolling means performing one or more cold rolling passes without annealing. In all cold rolling processes, the final reduction ratio is preferably set to 70 to 95%.

[0108] When cold rolling and sandwich annealing are performed in two steps, the annealing is preferably performed at 750 to 1200° C. for 30 seconds to 10 minutes.

[0109] When cold rolling with intermediate annealing is performed two or more times, the magnetic properties tend to be uniform. The number of cold rolling times is appropriately selected according to the desired magnetic properties and production costs.

[0110] The final product thickness is determined at this stage. Generally, the product thickness can be set to less than 0.35mm. Taking into account the capacity and operability of each production facility, a practical minimum thickness of 0.20mm may be adopted. Furthermore, once the final product thickness is determined, the thickness of the hot-rolled steel strip is automatically determined based on the cold rolling ratio.

[0111] Final annealing (Final Annealing: Finish Annealing) Final annealing is significantly affected by time and temperature. To shorten annealing time, the higher the temperature, the better. However, the current continuous annealing furnace equipment specifications stipulate that the maximum temperature is 1075°C. When the lower temperature is less than 950°C, a slightly longer soaking period is required.

[0112] Furthermore, in order to improve the texture, a patent document (Japanese Patent Publication No. 06-051889) proposes setting the heating rate to 750 to 1150° C. to 133° C. / second or higher. This does not hinder the application of this technology.

[0113] If the holding time of the final annealing is less than 20 seconds, grain growth is insufficient, and even if it exceeds 90 seconds, grain growth does not occur beyond that. Therefore, the holding time is set to be within the range of 20 to 90 seconds.

[0114] (Aging treatment)

[0115] After the final annealing or during the cooling of the final annealing, an overaging treatment is performed, whereby the solid solution C in the steel plate is combined with Fe atoms to form cementite, the fixation of the solid solution C will progress, and the effect of suppressing magnetic aging and tensile strain will be improved. The overaging temperature of the overaging treatment is set to be above 50°C and below 500°C. When it is less than 50°C, the effect may not be fully obtained, and when it exceeds 500°C, the fixation of the solid solution C may not be maintained. Regarding the upper limit of the overaging temperature, it is preferably set to be below 300°C. It is also possible to set the lower limit to be above 100°C, preferably to be above 200°C. In addition, the overaging time is set to be above 10 seconds. When it is less than 10 seconds, the effect of the overaging treatment may not be fully obtained. The upper limit of the overaging time is not particularly limited, but its effect will be saturated, so it is preferably set to be below 60 minutes.

[0116] (Bending Process)

[0117] After the final annealing, a bending process is performed, whereby the solid solution C or solid solution N in the steel sheet will invade the dislocation of the Fe atomic arrangement, and the fixation of the solid solution C or solid solution N will progress, thereby improving the effect of suppressing magnetic aging and tensile strain. The bending process is performed by winding the steel sheet on a roller with a diameter of less than 500 mm. That is, the bending process is performed by pressing the steel sheet on a roller with a diameter of less than 500 mm. When the roller is 500 mm or more in diameter, the steel sheet cannot be fully bent, and sometimes the effect is not fully obtained. The lower limit of the roller diameter is not specifically limited, but the smaller the diameter, the greater the bending will become, and there will be risks such as fracture of the steel sheet, so it can also be set to 300 mm or more. In addition, it is also possible to set the bending angle of the steel sheet to be greater than 5 degrees and less than 20 degrees based on the tangent direction (horizontal direction of the plate surface of the steel sheet in a flat state) at the tangent point of the roller cross-section circle and the steel sheet as a reference (0 degrees). When it is less than 5 degrees, the steel sheet cannot be fully bent, and sometimes the effect is not fully obtained. If the bending angle is too large, there is a risk of breaking the steel plate, so it can be set to 20 degrees or less. The upper limit of the bending angle can also be set to 15 degrees or less. The lower limit can be set to 8 degrees or more, and can also be set to 10 degrees or more.

[0118] Furthermore, flattening and bending cause a different pattern of disorder in the arrangement of Fe atoms in the steel, leading to different dislocation introduction patterns. Therefore, achieving the same effects as bending is difficult. Furthermore, bending is cost-effective. Furthermore, bending only requires a single pass to achieve the aforementioned effects.

[0119] Furthermore, flattening is performed by winding the steel sheet onto a roller. Its purpose is to straighten the rolled steel sheet, eliminating any warping or bending, and flattening the rolled steel sheet. Furthermore, the roller diameter is generally small, typically less than 100 mm. Therefore, flattening differs from the bending process of this embodiment.

[0120] Alternatively, overaging treatment and bending treatment may be used together. Alternatively, overaging treatment and bending may be performed simultaneously, or bending may be performed after overaging treatment. By using these treatments together, the effects of suppressing magnetic aging and tensile strain can be synergistically enhanced.

[0121] (Insulation coating)

[0122] Since electromagnetic steel sheets are stacked, an insulating coating can be applied to the surface to ensure interlayer resistance. Conventionally, coatings containing Cr have been used, but recently, Cr-free coatings have also been developed. Any type of coating is acceptable.

[0123] Example

[0124] Continuous casting of molten steel was carried out to prepare 250 mm thick slabs for obtaining steel having the chemical composition shown in Table 1 below. Then, the slabs were hot rolled to form hot-rolled plates. The slab reheating temperature at this time was 1200°C, the final temperature in the final rolling was 850°C, the coiling temperature during coiling was 650°C, and the final plate thickness was 2.0 mm. Then, the hot-rolled plates were annealed at 900 degrees for 1 minute as hot-rolled plates, the scale was removed by pickling, and the plates were cold rolled to a thickness of 0.25 mm. Then, final annealing was carried out at 800°C for 30 seconds. Then, the overaging treatment described in Table 1 was carried out. In addition, for some samples, they were coiled as bending processes. The steel sheet was passed through a roller and bent at a bending angle of 10 degrees (with the tangent direction of the roller cross-section circle being 0 degrees). That is, the steel sheet was bent by pressing it against the roller. If overaging treatment was performed, the bending process was performed during or after the overaging treatment. If overaging treatment was not performed, the bending process was performed after the final annealing. In addition, it was confirmed that the steel sheet (No. 127) manufactured under the same conditions as No. 101, except that the overaging treatment was performed during the cooling of the final annealing, had the same magnetic properties and AI as No. 101.

[0125] Next, the magnetic characteristics of the iron loss W10 / 400 (maximum magnetic flux density 1.0T, frequency 400Hz iron loss), and the magnetic flux density B50 (magnetic flux density when the magnetizing force is 5000A / m) were measured. A 55mm square sample piece was extracted from the measurement sample, and the average value of the characteristics in the rolling direction and the width direction was calculated. The magnetic measurement was performed using a device that can measure a 55mm square test piece or a smaller test piece that complies with the electromagnetic circuit described in JIS C 2556 (2015). The measurement results are shown in Table 1. For the sample after the magnetic measurement, an aging treatment for magnetic measurement was performed at 200°C for 24 hours, and the iron loss W10 / 400 was measured. The value obtained by dividing the increase in its iron loss by the iron loss W10 / 400 before aging treatment is the iron loss deterioration rate after aging treatment, and is shown in Table 1. In addition, AI was also measured, and its results are shown in Table 1.

[0126] [Table 1]

[0127]

[0128] Steels Nos. 101 to 122, and 127 have good compositions and AI. Steel No. 123 has not undergone either aging or bending, resulting in a high AI. Steel Nos. 124 and 126 have no Cr additions, resulting in high AI. Steel No. 125 has a Ti content exceeding the upper limit, resulting in high iron loss. Furthermore, comparative examples with high AI tend to have a higher iron loss degradation rate after aging.

[0129] As an evaluation of tensile strain, the yield elongation (described in JIS Z 2241) in the pre-aging stretch (8% strain) of the AI ​​test is investigated. When yield elongation occurs, tensile strain as a visual surface defect occurs. In the example where AI is less than 40 MPa, all yield elongations are not produced, but in the example where AI is more than 40 MPa, yield elongation is produced. Therefore, tensile strain can be suppressed by reducing AI (less than 40 MPa). In addition, the "---" in the "yield elongation" column of the table indicates that no yield elongation is produced.

Claims

1. A non-oriented electromagnetic steel sheet, characterized in that: Chemical composition by mass %: C: 0.0100% or less, Si: 2.6% or more and 4.5% or less, Mn: 0.10% or more and 3.00% or less, P: 0.15% or less, S: 0.0040% or less, N: 0.0040% or less, Al: 0.10% or more and 2.00% or less, one or more selected from Sn and Sb: 0 to 0.200%, Cr: 0.001 to 5.000%, Ni: 0 to 5.000% , Cu: 0-5.000%, Ca: 0-0.020%, Mg: 0-0.0200%, and rare earth elements REM: 0-0.020%, Ti: less than 0.0100%, B: 0%-0.0050%, O: 0%-0.0200%, and the remainder: composed of Fe and impurities, when aged at 100°C for 1 hour after applying 8% strain, the difference in lower yield point before and after aging treatment: AI is less than 40 MPa.

2. The non-oriented electrical steel sheet according to claim 1, wherein The chemical composition further includes Mo: 0% to 0.0200%.

3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein: In the following formula, Cev≤0.0055%, Cev = 12 × ([C (mass %)] / 12 + [N (mass %)] / 14 − [B (mass %)] / 11 − [Ti (mass %)] / 48 − [Cr (mass %)] / 104 − [Mo (mass %)] / 192) In the above formula, [element symbol (mass %)] represents the content (mass %) of the element in the chemical composition, and 0 is substituted when the element is not contained.

4. A method for producing a non-oriented electrical steel sheet according to any one of claims 1 to 3, characterized in that: When a non-oriented electrical steel sheet is manufactured by a process including steelmaking, hot rolling, hot rolled sheet annealing, pickling, cold rolling, final annealing, and overaging treatment, the overaging temperature of the overaging treatment is set to 50° C. to 500° C., the temperature range of 50° C. or higher is set to 10 seconds or longer, and the chemical composition of the non-oriented electrical steel sheet is, in mass %, C: not more than 0.0100%, Si: not less than 2.6% and not more than 4.5%, Mn: not less than 0.10% and not more than 3.00%, P: not more than 0.15%, S: not more than 0.0040%, N: 0.00 40% or less, Al: 0.10% or more and 2.00% or less, one or more selected from Sn and Sb: 0-0.200%, Cr: 0.001-5.000%, Ni: 0-5.000%, Cu: 0-5.000%, Ca: 0-0.020%, Mg: 0-0.0200%, and rare earth elements REM: 0-0.020%, Ti: less than 0.0100%, B: 0%-0.0050%, O: 0%-0.0200%, and the remainder: Fe and impurities.

5. The method for producing a non-oriented electrical steel sheet according to claim 4, wherein: The chemical composition further includes Mo: 0% to 0.0200%.

6. The method for producing a non-oriented electrical steel sheet according to claim 4 or 5, wherein: During the overaging treatment, in at least a portion of the step of maintaining the steel sheet at a temperature in the range of 50° C. to 500° C., the steel sheet is bent by being pressed against a roll having a diameter of less than 500 mm.

7. The method for producing a non-oriented electrical steel sheet according to any one of claims 4 to 6, wherein: After the overaging treatment, the steel sheet was bent by being pressed against a roll having a diameter of less than 500 mm.

8. A method for producing a non-oriented electrical steel sheet according to any one of claims 1 to 3, characterized in that: When a non-oriented electrical steel sheet is manufactured by a process including steelmaking, hot rolling, annealing of a hot-rolled sheet, pickling, cold rolling, final annealing, and bending, wherein in the bending, the steel sheet is bent by being pressed against a roll having a diameter of less than 500 mm, and the chemical composition of the non-oriented electrical steel sheet is, in terms of mass %, C: 0.0100% or less, Si: 2.6% or more and 4.5% or less, Mn: 0.10% or more and 3.00% or less, P: 0.15% or less, S: 0.0040% or less, and N: 0.0040% or less. , Al: more than 0.10% and less than 2.00%, one or more selected from Sn and Sb: 0-0.200%, Cr: 0.001-5.000%, Ni: 0-5.000%, Cu: 0-5.000%, Ca: 0-0.020%, Mg: 0-0.0200%, and rare earth elements REM: 0-0.020%, Ti: less than 0.0100%, B: 0%-0.0050%, O: 0%-0.0200%, and the remainder: composed of Fe and impurities.

9. The method for producing a non-oriented electrical steel sheet according to claim 8, wherein: The chemical composition further includes Mo: 0% to 0.0200%.

10. A rotating electrical machine, characterized in that: A stator, a rotor, and a case for accommodating the stator and the rotor are provided, wherein the core material of the stator or the core material of the rotor is the non-oriented electromagnetic steel sheet according to any one of claims 1 to 3.

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