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

Abstract

The present invention relates to a non-oriented electrical steel sheet having a composition comprising the following elements in percentage by weight: 0.0001% < = carbon < = 0.007%, 0.09% < = manganese < = 0.15%, 2.5% < = silicon < = 3%, 0.1% < = aluminum < = 0.5%, phosphorus < = 0.15%, sulfur < = 0.006%, nitrogen < = 0.09%, and the balance being iron and unavoidable impurities. And may include one or more of the following optional elements: 0% < = niobium < = 0.1%, 0% < = titanium < = 0.1%, 0% < = vanadium < = 0.1%, 0% < = chromium < = 1%, 0% < = molybdenum < = 0.5%, 0% < = tungsten < = 0.1%, 0% < = cobalt < = 1%, 0% < = arsenic < = 0.05%, 0.001% < = calcium < = 0.01%, 0% < = copper < = 1%, 0% < = nickel < = 1%, 0% < = boron < = 0.05%, 0% < = lead < = 0.2%, 0% < = tin < = 0.2%, 0% < = antimony < = 0.2%, and the balance being Fe. A steel sheet having a microstructure composed of ferrite and including, in area fraction, 80% to 100% of a recrystallized microstructure having an average grain size of 20 [mu] m to 110 [mu] m and 0% to 20% of a non-recrystallized microstructure having an average grain size of 10 [mu] m to 100 [mu] m, the remainder being composed of iron and unavoidable impurities resulting from processing, the steel sheet having a microstructure composed of ferrite and having an average grain size of 10 [mu] m to 100 [mu] m, and a non-recrystallized microstructure having an average grain size of 10 [mu] m to 100 [ and the non-oriented electrical steel sheet has a percentage of eddy current loss in the total iron loss measured at 1 T and 400 Hz according to IEC 60404-2 standard when calculated according to the Bertotti method of 35% to 45%.

Description

Technical Field

[0001] The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, the present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same, wherein the non-oriented electrical steel sheet has low iron loss, particularly low eddy current loss, and good mechanical properties. Background Art

[0002] Due to the global push for energy-saving electrical equipment, significant research and development efforts are being directed towards achieving the higher performance characteristics required of non-oriented electrical steel sheets used as core materials for electric motors. In particular, demand has recently increased for compact, high-power motors for use in electric vehicles and other applications. These electric vehicle motors are designed to achieve high-speed rotation, thereby achieving high torque, while minimizing losses. This requires lightweight and efficient non-oriented electrical steel, with low losses as its key characteristic. For non-oriented electrical steel, achieving a balance between losses, magnetic permeability, polarization, thermal conductivity, tensile strength, and yield strength is crucial.

[0003] The lower the iron losses in a motor, the higher its efficiency. Therefore, to reduce the amount of iron losses in a motor, motor manufacturers have several options. Their primary approach is to reduce either hysteresis losses or eddy current losses to improve the efficiency of their motors. Improvements are often achieved through a combination of the two approaches. The present invention addresses the second option, namely, reducing eddy current losses in a motor. There are two alternative approaches to reducing eddy current losses.

[0004] A first approach involves reducing the thickness of the steel sheets used in the motor, for example to a thickness of less than 0.35 mm or even less. Unfortunately, this solution has its limitations due to a reduction in the stacking factor (which reduces the torque achievable for a given machine height), and also due to an excessive reduction in the rigidity of certain automotive components and the occurrence of acoustic problems that can cause discomfort to the passengers.

[0005] The second approach involves optimizing the elemental composition of the steel sheet, for example by increasing the amount of alloying elements to limit eddy current losses. Among these alloying elements, aluminum and manganese, for example, possess attractive mechanical and magnetic properties while significantly reducing eddy current losses. However, the addition of alloying elements can be limited to a certain limit, as above a certain percentage, they influence hysteresis losses and magnetic polarization.

[0006] Early research and development in the field of high strength non-oriented electrical steel has resulted in several methods for producing high strength non-oriented electrical steel, some of which are listed herein for a clear understanding of the present invention:

[0007] US2021 / 371948 is a non-oriented electrical steel sheet having a thickness not greater than 4.5×10-6 A nonoriented electrical steel sheet having an average magnetostriction λp-p at 400 Hz and 1.0 T of 40% and an area ratio of recrystallized grains at a cross section in the rolling direction of the steel sheet of 40 to 95%, and an average grain size of 10 to 40 μm, the nonoriented electrical steel sheet being obtained by subjecting a steel slab to hot rolling, hot strip annealing, cold rolling under appropriate cold rolling and finish annealing conditions, and finish annealing, the steel slab comprising, in mass%, C: not more than 0.005%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, Al: not more than 3.0%, P: not more than 0.20%, S: not more than 0.005%, N: not more than 0.005%, Ti: not more than 0.003%, V: not more than 0.005%, and Nb: not more than 0.005%, and satisfying Si-2Al-Mn≥0, and a motor core being manufactured from such a steel sheet. US2021 / 371948 does not show total elongation and eddy current losses at all. Summary of the Invention

[0008] An object of the present invention is to solve these problems by producing a nonoriented electrical steel sheet having a percentage of eddy current loss in the total iron loss of 35% to 45%, and preferably 40% to 45%, when calculated according to the Bertotti method.

[0009] In a preferred embodiment, the following additional characteristics may also be achieved, alone or in combination:

[0010] - an ultimate tensile strength of 460 MPa or greater in both the transverse direction and the rolling direction, and preferably greater than 480 MPa in both the transverse direction and the rolling direction;

[0011] - a yield strength of 300 MPa or more in both the transverse direction and the rolling direction, and preferably 330 MPa or more in both the transverse direction and the rolling direction;

[0012] - a total elongation of 22% or more in both the transverse direction and the rolling direction, and preferably greater than or equal to 24% in both the transverse direction and the rolling direction;

[0013] - a magnetic polarization (J50) at 5000 A / m of 1.63 T to 1.66 T, and preferably a magnetic polarization (J50) at 5000 A / m of 1.64 T to 1.66 T;

[0014] - a total loss of 18 to 25 W / kg when measured at 1 T and 400 Hz, and preferably a total loss of 19 to 24 W / kg when measured at 1 T and 400 Hz, and more preferably a total loss of 19 to 22 W / kg when measured at 1 T and 400 Hz.

[0015] Preferably, such a steel may also have good suitability for rolling as well as good stampability and paintability.

[0016] Preferably, the hardness is greater than or equal to 185 HV, and preferably the hardness is greater than or equal to 195 HV.

[0017] Another object of the invention is also to make available a method for manufacturing these panels that is compatible with conventional industrial applications and at the same time robust to variations in manufacturing parameters.

[0018] The above objects and other advantages of the present invention will become more apparent through detailed description of preferred embodiments of the present invention. DETAILED DESCRIPTION

[0019] The chemical composition of non-oriented electrical steel includes the following elements in weight percentage:

[0020] Carbon is present in the steel of the present invention at 0.0001% to 0.007%. Carbon is a precipitate-forming element and is therefore detrimental to the magnetic properties of the steel of the present invention. Therefore, carbon is present in the steel of the present invention at 0.0001% to 0.007%. Because carbon promotes magnetic aging, the preferred carbon content according to the present invention is 0.002% to 0.007%, and more preferably 0.002% to 0.006%.

[0021] The steel of the present invention has a manganese content of 0.09% to 0.15%. Manganese provides solid solution strengthening and reduces iron loss by increasing specific resistivity. When manganese additions exceed 0.15%, magnetic flux density may be significantly reduced, and recrystallization of the steel during annealing will be hindered. The preferred limit of manganese presence is 0.1% to 0.14%, and more preferably 0.1% to 0.13%.

[0022] The steel of the present invention contains 2.5% to 3% silicon. Silicon contributes to strength through solid solution strengthening and is a key element for reducing eddy current losses (iron loss) by increasing the steel's resistivity. A minimum silicon content of at least 2.5% is required to achieve these effects. However, exceeding 3% silicon causes rolling difficulties and significantly reduces the steel's magnetic induction. The preferred limit for silicon is 2.6% to 3%, and more preferably 2.6% to 2.95%.

[0023] The aluminum content is 0.1% to 0.5%. Aluminum increases the resistivity of the material and can effectively reduce the iron loss of steel. When the aluminum content exceeds 0.5%, the magnetic induction of the steel is significantly reduced, which also detrimentally affects the cold rollability of the steel of the present invention. The preferred limit of aluminum is 0.1% to 0.45%, and more preferably 0.2% to 0.4%.

[0024] Sulfur is not an essential element, but may be contained in steel as an impurity. From the perspective of the present invention, the sulfur content is preferably as low as possible. However, from the perspective of manufacturing costs, the sulfur content is 0.006% or less. In addition, if sulfur is present in a high concentration in steel, it will combine to form sulfides that are detrimental to the magnetic properties of the present invention.

[0025] The phosphorus content of the steel of the present invention is 0% to 0.15%. Phosphorus reduces hot and cold ductility, particularly due to its tendency to segregate at grain boundaries or co-segregate with manganese. For these reasons, its content is limited to 0.15%, and preferably less than 0.09%.

[0026] Nitrogen is limited to 0.09% to minimize precipitation of aluminum nitrides during solidification which are detrimental to the magnetic properties of the steel.

[0027] Titanium is an optional element and, when added to the steel of the present invention, is present in an amount of 0% to 0.1%. It forms titanium nitrides that appear during solidification of the cast product. Therefore, the amount of titanium is limited to 0.1% to avoid the formation of titanium nitrides, which are detrimental to the magnetic properties of the steel of the present invention. Titanium contents below 0.001% have no effect on the steel of the present invention.

[0028] Niobium is present in the steel according to the present invention in amounts of 0% to 0.1% and is suitable for forming carbonitrides to increase the strength of the steel according to the present invention through precipitation hardening. Niobium also influences the size of microstructural components through its precipitation as carbonitrides. However, niobium contents above 0.1% are not economically attractive due to saturation effects.

[0029] Vanadium is present in the steel of the present invention at 0% to 0.1% and effectively improves the strength of the steel by forming carbides or carbonitrides, and the upper limit is 0.1% from an economical viewpoint.

[0030] Chromium is an optional element of the steel of the present invention, present in an amount of 0% to 1%. Chromium provides strength to the steel through solid solution strengthening, but when used above 1%, it impairs the magnetic properties of the steel.

[0031] Molybdenum is an optional element constituting 0% to 0.5% of the steel of the present invention. Mo has the effect of coarsening carbides and thus reducing iron loss. When it exceeds 0.5%, the effect of improving iron loss is saturated.

[0032] Tungsten is an optional element comprising 0% to 0.1% of the steel of the present invention. Like Mo, tungsten has the effects of coarsening carbides and reducing iron loss. However, when added in an amount less than 0.001% by mass, these effects are not fully achieved, while when added in an amount exceeding 0.1% by mass, the iron loss improvement effect saturates.

[0033] Cobalt is an optional element comprising 0% to 1% of the steel of the present invention. Cobalt increases the magnetic moment of Fe alloys and has the effects of increasing magnetic flux density and reducing iron loss. However, when the addition amount is less than 0.01% by weight, these effects are not fully achieved, while when it exceeds 1% by weight, the raw material cost increases significantly.

[0034] Arsenic is an optional element constituting 0% to 0.05% of the steel of the present invention. As is a grain boundary segregation element and has the effect of improving the structure and thereby reducing iron loss. These effects are achieved by adding not less than 0.001% by weight. However, As is an element that causes grain boundary embrittlement, and this adverse effect becomes particularly pronounced when added in amounts exceeding 0.05% by weight. Therefore, As is preferably added in the range of 0.001% to 0.05% by weight.

[0035] Nickel can be added as an optional element in an amount of 0% to 1% to increase the strength of the steel of the present invention and improve its strength and elongation. However, when its content is above 1%, nickel causes ductility to deteriorate. In a preferred embodiment, the nickel content is kept below 0.04%.

[0036] Copper may be added as an optional element in an amount of 0% to 1% to improve the strength and elongation of the steel of the present invention. However, when its content is higher than 1%, it may deteriorate the surface appearance.

[0037] Boron is an optional element of the steel of the present invention and may be present in the range of 0% to 0.05%. Boron forms boron nitrides when added in amounts of at least 0.0001% and imparts additional strength to the steel of the present invention.

[0038] Calcium may optionally be present in the steel of the present invention and may be present in an amount of 0.001% to 0.01%. Calcium aids in the refining of the steel by binding harmful sulphur contents into globular form, thereby hindering the deleterious effects of sulphur.

[0039] Other elements such as Sn, Pb or Sb can be added individually or in combination in the following proportions: Sn≦0.2%, Pb≦0.2% and Sb≦0.2%. Up to the maximum content levels shown, these elements allow grain refinement during solidification. In a preferred embodiment, the Sn content is less than 0.04%.

[0040] The remainder of the steel's composition consists of iron and unavoidable impurities resulting from processing.

[0041] The microstructure consists of ferrite. The steel of the present invention has a recrystallized microstructure area of ​​80% to 100% by area fraction, with the average grain size of the grains ranging from 20 to 110 microns. This recrystallized structure with a high degree of recrystallization is due to uniform silicon enrichment, which improves the magnetic properties of the steel of the present invention. The controlled grain size ensures excellent mechanical properties in both the transverse and rolling directions. The preferred degree of recrystallization is 90% to 100%. The preferred average grain size of the present invention is 20 to 100 microns, and more preferably 20 to 90 microns.

[0042] The steel of the present invention may have a non-recrystallized microstructural region of 0% to 20% by area fraction, and a preferred non-recrystallization degree is 0% to 10%, and more preferably 0% to 5%.

[0043] The microstructure of the non-oriented electrical steel does not contain microstructure components such as martensite, bainite, pearlite and cementite in addition to the above-mentioned microstructures.

[0044] The steel according to the invention can be manufactured by any suitable method. However, as a non-limiting example, it is preferred to use the method according to the invention which will be described in detail.

[0045] Such a preferred method comprises providing a semi-finished casting of steel having the chemical composition of the steel according to the invention. The casting may be made into an ingot or continuously into the form of a thin slab or thin strip, i.e., for any form of casting, the thickness range is about 240 mm or less.

[0046] For example, a casting in slab form is cast using the chemical composition according to the present invention and then reheated to a temperature of 1050°C to 1250°C until the temperature is uniform throughout the slab. Below 1050°C, rolling becomes difficult and the forces on the rolling mill will be too high. Above 1250°C, high-silicon steel grades become very soft and may exhibit some sagging, making them difficult to handle. Preferably, the slab reheat temperature is 1100°C to 1200°C, and more preferably 1100°C to 1150°C.

[0047] The reheated slab is then subjected to hot rolling, where the finishing hot rolling temperature influences the final hot-rolled microstructure and occurs at 800°C to 950°C. When the finishing temperature is below 800°C, recrystallization is limited and the microstructure is highly deformed. Temperatures above 950°C result in greater impurities in the solid solution, potentially leading to precipitation and deterioration of magnetic properties. Preferably, the finishing temperature is 850°C to 900°C, and more preferably 860°C to 890°C.

[0048] The hot-rolled steel sheet obtained in this manner is then immediately cooled to the coiling temperature of the hot-rolled steel sheet, which also applies to the hot-rolled steel sheet; this occurs at 600°C to 750°C. For the steel of the present invention, coiling at temperatures below 600°C will not result in the appropriate distribution and size of the precipitates. Above 750°C, a thick oxide layer will form, which will make subsequent processing steps such as cold rolling and / or pickling difficult. Preferably, the cooling rate will be less than or equal to 200°C / second, and more preferably, the cooling rate will be between 12°C / second and 75°C / second. Preferably, the coiling temperature is between 620°C and 700°C, and more preferably between 620°C and 680°C.

[0049] The coiled hot rolled steel sheet is then cooled to room temperature and then subjected to optional hot strip annealing.

[0050] The hot rolled steel sheet may be subjected to an optional descaling step to remove the scale formed during hot rolling prior to the optional hot strip annealing. The hot rolled sheet is then subjected to an optional hot strip annealing, such hot strip annealing being conducted at a temperature of 650°C to 1100°C, preferably for at least 10 seconds and not more than 96 hours, with the temperature preferably being maintained at 700°C to 1070°C, and more preferably at 720°C to 1050°C. Thereafter, the optional descaling step of the hot rolled steel sheet may be performed, for example, by pickling the sheet.

[0051] Therefore, the obtained hot-rolled steel sheet may optionally have a thickness of 0.8 mm to 3.5 mm, and preferably 0.9 mm to 3 mm, and more preferably 1 mm to 2.8 mm.

[0052] The hot rolled steel sheet is then subjected to cold rolling at a thickness reduction ratio of 50% to 95% to obtain a cold rolled steel sheet. Preferably, the thickness reduction ratio is 60% to 95%, and more preferably 75% to 95%.

[0053] The cold rolled steel sheet is then subjected to a heat treatment which imparts the desired mechanical properties and microstructure to the steel of the present invention.

[0054] The cold rolled steel sheet is then heated, wherein the heating starts from room temperature and is heated to an annealing temperature T of 860°C to 990°C, preferably 870°C to 980°C, and more preferably 900°C to 940°C at a heating rate HR1 of at least 1°C / second. 均热 In a preferred embodiment, the heating rate HR1 used for heating is at least 2° C. / second, and more preferably at least 5° C. / second.

[0055] Cold rolled steel sheet in T 均热 The holding time is from 10 seconds to 5000 seconds to ensure 80% to 100% recrystallization.

[0056] The cold rolled steel sheet is then cooled, wherein the cooling is carried out from T 均热 Initially, the cold-rolled steel sheet is cooled to a temperature T1 in the range of 20°C to 300°C at a cooling rate CR1 of 1°C / s to 150°C / s. In a preferred embodiment, the cooling rate CR1 is 3°C / s to 120°C / s. The preferred T1 temperature is 20°C to 200°C.

[0057] The cold-rolled steel sheet thus obtained has a thickness of 0.3 mm to 0.38 mm, and more preferably 0.31 mm to 0.36 mm, and even more preferably 0.32 mm to 0.36 mm.

[0058] Then, the cold rolled steel sheet is cooled to room temperature to obtain a non-oriented electrical steel sheet.

[0059] The nonoriented electrical steel sheet of the present invention may be optionally coated with an insulating organic coating or an inorganic coating or a combination thereof to improve insulation properties.

[0060] Example

[0061] The following tests, examples, graphic illustrations and tables presented herein are non-limiting in nature and must be considered for purposes of illustration only and will demonstrate the advantageous features of the present invention.

[0062] Steel plates made of steel having different compositions are summarized in Table 1, wherein the steel plates were respectively produced according to the process parameters as described in Table 2. Table 3 summarizes the evaluation results of the obtained properties.

[0063] All steels in Table 1 have nitrogen contents below 0.09%.

[0064] Table 2 summarizes the hot rolling and annealing process parameters applied to the cold-rolled steel sheets to impart the mechanical and magnetic properties required for the steels in Table 1 to become non-oriented electrical steel. All of the inventive steels, I1 through I4, were cooled at a cooling rate of 15°C / second after hot rolling. After coiling, all inventive examples (i.e., I1 through I4) were subjected to a hot strip annealing at 800°C for 12 hours. Furthermore, for the inventive examples, the cold rolling reduction was 80%, and the subsequent heating rate HR1 to the annealing soaking temperature was 5°C / second. The T1 temperature for all inventive examples was 25°C, with a cooling rate CR1 of 5°C / second.

[0065] All steels produced according to the parameters of Table 2 showed a recrystallized microstructure with greater than 95% recrystallization and with a grain size ranging from 20 μm to 110 μm.

[0066]

[0067] Table 3

[0068] The results of several mechanical tests performed according to the standards are summarized. The ultimate tensile strength, total elongation and yield strength were measured according to the NF EN ISO 6892-1 standard, and the J50 magnetic properties and the total iron loss at 1 T and 400 Hz were measured according to the IEC 60404-2 standard. The eddy current losses were calculated according to the Bertotti method published by Giorgio Berttoti in the paper entitled "General Properties of Power Losses in Soft Ferromagnetic Materials" published in IEEE TRANSACTIONS ON MAGNETICS, Vol. 24, No. 1, January 1988. Equation 2 determines the value given by (P 经典 ) are classical losses represented by , which for the purposes of this invention are called eddy current losses.

[0069] The average grain size of the recrystallized microstructure was measured using the linear intercept method according to ASTM E112 96(02).

[0070]

Claims

1. A non-oriented electrical steel sheet having a composition comprising the following elements: expressed in weight percentage, 0.0001%≤Carbon≤0.007% 0.09%≤Manganese≤0.15% 2.5%≤Silicon≤3% 0.1%≤Aluminum≤0.5% Phosphorus ≤ 0.15% Sulfur ≤ 0.006% Nitrogen ≤ 0.09% and can include one or more of the following optional elements: 0%≤Niobium≤0.1% 0%≤Titanium≤0.1% 0%≤Vanadium≤0.1% 0%≤Cr≤1% 0%≤Molybdenum≤0.5% 0%≤Tungsten≤0.1% 0%≤Cobalt≤1% 0%≤Arsenic≤0.05% 0.001%≤Calcium≤0.01% 0%≤Copper≤1% 0%≤Nickel≤1% 0%≤boron≤0.05% 0%≤Lead≤0.2% 0%≤Tin≤0.2% 0%≤Antimony≤0.2% The remainder of the composition is composed of iron and inevitable impurities caused by processing, the microstructure of the steel sheet is composed of ferrite and contains, by area fraction, 80% to 100% of a recrystallized microstructure and 0% to 20% of a non-recrystallized microstructure, wherein the average grain size of the recrystallized microstructure is 20 to 110 μm, and the non-oriented electrical steel sheet has a percentage of eddy current loss in the total iron loss measured at 1 T and 400 Hz in accordance with IEC 60404-2 standard of 35 to 45% when calculated according to the Bertotti method. 2 . The non-oriented electrical steel sheet according to claim 1 , wherein the composition comprises 2.6% to 3% of silicon. 3 . The non-oriented electrical steel sheet according to claim 1 , wherein the composition comprises 0.002% to 0.007% of carbon. 4 . The non-oriented electrical steel sheet according to claim 1 , wherein the composition comprises 0.1% to 0.45% of aluminum. 5 . The non-oriented electrical steel sheet according to claim 1 , wherein the composition comprises 0.1% to 0.14% of manganese.

6. The non-oriented electrical steel sheet according to any one of claims 1 to 5, wherein the amount of non-recrystallized microstructure is 0% to 10%.

7. The nonoriented electrical steel sheet according to any one of claims 1 to 6, wherein the amount of recrystallized microstructure is 90% to 100%.

8. The nonoriented electrical steel sheet according to any one of claims 1 to 7, wherein the steel sheet has an ultimate tensile strength of at least 460 MPa in both the transverse direction and the rolling direction. 9 . The nonoriented electrical steel sheet according to claim 1 , having a yield strength of 300 MPa or more in both a transverse direction and a rolling direction.

10. The nonoriented electrical steel sheet according to any one of claims 1 to 9, wherein the steel sheet has a total elongation of at least 22% in both the transverse direction and the rolling direction.

11. A method for producing a non-oriented electrical steel sheet according to any one of claims 1 to 10, comprising the following steps in sequence: - providing a steel composition according to any one of claims 1 to 5; - reheating the semi-finished product to a temperature of 1050° C. to 1250° C.; - rolling the semi-finished product to obtain hot-rolled steel sheets, wherein the hot rolling finishing temperature should be 800° C. to 950° C.; - cooling the hot rolled sheet immediately after hot rolling; - then cooling the hot rolled steel sheet from the end of hot rolling to a coiling temperature in the range of 600° C. to 750° C. at a cooling rate of at least 10° C. / s; - thereafter coiling the hot rolled steel sheet at the coiling temperature range of 600° C. to 750° C.; - optionally subjecting the hot rolled steel sheet to a descaling process; - optionally subjecting the hot rolled steel sheet to hot strip annealing at 650°C to 1100°C for a period of 10 seconds to 96 hours; - optionally subjecting the hot rolled steel sheet to a descaling process; - cold rolling the hot-rolled steel sheet at a reduction ratio of 50% to 95% to obtain a cold-rolled steel sheet; - thereafter annealing the cold rolled steel sheet at a heating rate HR1 of at least 1°C / s, wherein the heating for annealing is started from room temperature to an annealing temperature range T of 860°C to 990°C 均热 ; - then annealing at the annealing temperature for a period of 10 seconds to 5000 seconds; - then cooling the cold rolled steel sheet at a cooling rate CR1 of 1°C / s to 150°C / s, the cooling starting from the annealing temperature to a temperature T1 of 300°C to 20°C; -Then cooled to room temperature to obtain a non-oriented electrical steel sheet.

12. The method according to claim 11, wherein the T used for annealing is 均热 The temperature is 870℃ to 980℃.

13. The method according to claim 11 or 12, wherein the temperature T1 is 200°C to 20°C. 14 . The method according to claim 11 , wherein the cooling rate CR1 is 3° C. / sec to 120° C. / sec.

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