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

Abstract

This invention relates to non-oriented electrical steel sheets having a composition comprising the following elements by weight percentage: 0.0001% ≤ carbon ≤ 0.007%, 0.30% ≤ manganese ≤ 0.7%, 3% ≤ silicon ≤ 3.6%, 0.4% ≤ aluminum ≤ 0.8%, 0.05% ≤ tin ≤ 0.15%, phosphorus ≤ 0.15%, sulfur ≤ 0.006%, and nitrogen ≤ 0.09%, and may contain 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. 0.05%, 0.001%≤calcium≤0.01%, 0%≤copper≤1%, 0%≤nickel≤1%, 0%≤boron≤0.05%, 0%≤lead≤0.2%, 0%≤antimony≤0.2%, with the remainder consisting of iron and unavoidable impurities caused by processing. The microstructure of the steel sheet consists of ferrite and contains 80% to 100% recrystallized microstructure and 0% to 20% non-recrystallized microstructure by area fraction, wherein the average grain size of the recrystallized microstructure is 20 micrometers to 110 micrometers, 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, which is 25% to 35% when calculated according to the Bertotti method.

Description

Technical Field

[0001] This invention relates to non-oriented electrical steel sheets and methods for manufacturing the same. Specifically, this invention relates to non-oriented electrical steel sheets with low iron loss, particularly low eddy current loss, and good mechanical properties, as well as methods for manufacturing the same. Background Technology

[0002] Due to the global advancements in energy efficiency of electrical equipment, significant research and development efforts have been invested in achieving higher performance characteristics for non-oriented electrical steel sheets intended for use as core materials in motors. Particularly in recent years, there has been a high demand for small, high-power motors used in electric vehicles and other applications. These electric vehicle motors are designed to enable high-speed rotation, thereby achieving high torque with minimal losses. This necessitates lightweight and efficient non-oriented electrical steels with low losses as a key characteristic. Finding a balance between losses, permeability, polarization, thermal conductivity, tensile strength, and yield strength is crucial for non-oriented electrical steels.

[0003] The lower the iron loss in an electric motor, the higher its efficiency. Therefore, to reduce iron loss, motor manufacturers have several options, the primary one being to reduce hysteresis loss or eddy current loss to improve motor efficiency. Progress is usually achieved through a combination of both methods. This invention relates to the second option: reducing eddy current loss in the motor. There are two-path alternatives for reducing eddy current loss:

[0004] The first approach involves reducing the thickness of the steel sheet used in the motor, for example, to less than 0.35 mm or even less. Unfortunately, this solution has its limitations due to the reduction in the stacking factor (which reduces the torque achievable for a given machine height), as well as the excessive reduction in the rigidity of certain automotive components and the emergence of acoustic problems that cause discomfort to 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, those such as aluminum and manganese possess attractive mechanical and magnetic properties, while simultaneously enabling a significant reduction in eddy current losses. However, the addition of alloying elements can be limited, as their presence beyond a certain percentage will affect hysteresis losses and magnetic polarization.

[0006] Early research in the field of high-strength non-oriented electrical steel has yielded several methods for producing high-strength non-oriented electrical steel, some of which are described herein to clearly understand the present invention:

[0007] US2021 / 371948 is a non-oriented electrical steel sheet with a diameter not exceeding 4.5 × 10⁻⁶ mm. -6The non-oriented electrical steel sheet has an average magnetostriction λp-p at 400 Hz and 1.0 T, 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 micrometers to 40 micrometers. It is obtained by subjecting a billet to hot rolling, hot annealing, cold rolling, and fine annealing under appropriate cold rolling and fine annealing conditions. The billet, by mass percent, contains: 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 satisfies Si - 2Al - Mn ≥ 0. Motor cores are manufactured from such steel sheets. US2021 / 371948 fails to demonstrate the total elongation and eddy current loss. Summary of the Invention

[0008] The object of the present invention is to solve these problems by manufacturing non-oriented electrical steel sheets having a percentage of eddy current loss in total iron loss of 25% to 35%, and preferably 28% to 32%, when calculated according to the Bertotti method.

[0009] In the preferred embodiment, the following additional characteristics can also be achieved, either individually or in combination:

[0010] - Ultimate tensile strength of 520 MPa or greater, and preferably greater than 540 MPa.

[0011] - Yield strength of 400 MPa or greater, and preferably 425 MPa or greater.

[0012] - 9% or greater, and preferably greater than or equal to 10% total elongation.

[0013] - Magnetic polarization at 5000 A / m of 1.63 T to 1.67 T (J50), preferably magnetic polarization at 5000 A / m of 1.64 T to 1.66 T (J50), more preferably magnetic polarization at 5000 A / m of 1.64 T to 1.66 T (J50).

[0014] - Total loss of 10 W / kg to 13 W / kg when measured at 1 T and 400 Hz, preferably 10 W / kg to 12.5 W / kg when measured at 1 T and 400 Hz, and more preferably 11.5 W / kg to 12.5 W / kg when measured at 1 T and 400 Hz.

[0015] Preferably, such steel also has good suitability for rolling, as well as good stamping and coating properties.

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

[0017] Another object of the present invention is to make available a method for manufacturing these steel plates that is compatible with conventional industrial applications and robust to variations in manufacturing parameters.

[0018] The above-mentioned objects and other advantages of the present invention will become more apparent from the detailed description of the preferred embodiments of the present invention. Detailed Implementation

[0019] The chemical composition of non-oriented electrical steel, by weight percentage, contains the following elements:

[0020] Carbon is present in the steel of the present invention at a concentration of 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, the presence of carbon in the steel of the present invention is 0.0001% to 0.007%. Since carbon promotes magnetic aging, the preferred carbon content according to the present invention is 0.002% to 0.007%, and more preferably 0.003% to 0.006%.

[0021] The steel of the present invention has a manganese content of 0.30% to 0.7%. Manganese provides solid solution strengthening and reduces iron loss by increasing resistivity. When the amount of manganese added exceeds 0.7%, the magnetic flux density may decrease significantly, and recrystallization of the steel during annealing will be hindered. The preferred limit for the presence of manganese is 0.35% to 0.65%, and more preferably 0.4% to 0.6%.

[0022] The steel of the present invention has a silicon content of 3% to 3.6%. Silicon is an element that helps to improve strength through solid solution strengthening and is a key element in reducing eddy current losses in iron loss by increasing the resistivity of the steel. These effects require a minimum silicon content of at least 3%. However, when the silicon content exceeds 3.6%, rolling becomes difficult, and the magnetic induction of the steel is significantly reduced. The preferred limit for the presence of silicon is 3.1% to 3.5%, and more preferably 3.2% to 3.5%.

[0023] The aluminum content is 0.4% to 0.8%. Aluminum increases the resistivity of the material and can effectively reduce the iron loss of steel. When the aluminum content is greater than 0.8%, the magnetic induction of the steel will be significantly reduced, which is also detrimental to the cold-rolling rollability of the steel of the present invention. The preferred limit for the amount of aluminum is 0.5% to 0.7%, and more preferably 0.6% to 0.7%.

[0024] Tin is an essential element in the steel of this invention and is present in an amount of 0.05% to 0.15%. It plays a beneficial role in magnetic properties, particularly by improving polarization and magnetic induction through enhanced texture. Below 0.05%, the effect of tin is negligible; while above 0.15%, the brittleness of the steel becomes a problem, increasing the risk of breakage during cold rolling and continuous annealing. Furthermore, grain growth is also hindered, thus deteriorating the magnetic properties. The preferred limit for the presence of tin is 0.06% to 0.14%, and more preferably 0.08% to 0.11%.

[0025] Sulfur is not an essential element, but it may be present in steel as an impurity. From the perspective of this invention, the sulfur content is preferably as low as possible, but from the perspective of manufacturing costs, a sulfur content of 0.006% or less is preferable. Furthermore, if a high level of sulfur is present in the steel, it can combine to form sulfides that are detrimental to the magnetic properties of this invention.

[0026] The phosphorus content of the steel of the present invention is 0% to 0.15%. Phosphorus reduces hot and cold ductility, especially 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%.

[0027] Nitrogen was limited to 0.09% to minimize the precipitation of aluminum nitrides, which are detrimental to the magnetic properties of steel during solidification.

[0028] Titanium is an optional element, and when added to the steel of the present invention, it is present in amounts of 0% to 0.1%. It forms titanium nitrides that occur during the solidification of the cast product. The amount of titanium is therefore limited to 0.1% to avoid the formation of titanium nitrides that are detrimental to the magnetic properties of the steel of the present invention. At titanium content below 0.001%, no effect is imparted to the steel of the present invention.

[0029] Niobium is present in the steel of the present invention at 0% to 0.1% and is suitable for forming carbonitrides to improve the strength of the steel of the present invention through precipitation hardening. Niobium will also affect the size of the microstructure components by precipitating as carbonitrides. However, due to the saturation effect, niobium contents above 0.1% are not economically interesting.

[0030] Vanadium is present in the steel of the present invention at 0% to 0.1% and effectively enhances the strength of the steel by forming carbides or carbonitrides, with an economic upper limit of 0.1%.

[0031] Chromium is an optional element in the steel of this invention, ranging from 0% to 1%. Chromium provides strength to the steel through solid solution strengthening, but when used at levels higher than 1%, it impairs the magnetic properties of the steel. In a preferred embodiment, the chromium content is at least 0.01%.

[0032] Molybdenum is an optional element comprising 0% to 0.5% of the steel of the present invention. Mo has the effect of coarsening carbides, thereby reducing iron loss. When its content exceeds 0.5%, the effect of improving iron loss saturates.

[0033] Tungsten is an optional element comprising 0% to 0.1% of the steel of the present invention. Like Mo, tungsten has the effect of coarsening carbides and reducing iron loss. However, when the amount added is less than 0.001% by weight, the above-mentioned effects cannot be sufficiently obtained, and when it exceeds 0.1% by weight, the effect of improving iron loss saturates.

[0034] Cobalt is an optional element comprising 0% to 1% of the steel of this invention. Cobalt is an element that increases the magnetic moment of Fe alloys and has the effect of increasing magnetic flux density and reducing iron loss. However, when the amount added is less than 0.01% by weight, the above-mentioned effects cannot be fully obtained, while when it exceeds 1% by weight, the raw material cost increases significantly.

[0035] Arsenic is an optional element comprising 0% to 0.05% of the steel of the present invention. As is a grain boundary segregation element and has the effect of improving texture and thus reducing iron loss. The above effect is obtained 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 significant when it is added at a rate greater than 0.05% by weight. Therefore, As is preferably added in the range of 0.001% to 0.05% by weight.

[0036] 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 higher than 1%, nickel causes a deterioration in ductility. In a preferred embodiment, the nickel content is at least 0.01%. In another embodiment, the nickel content is kept below 0.04%, and even more preferably, the nickel content is 0.01% to 0.04%.

[0037] Copper can 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 reduce the surface appearance.

[0038] Boron is an optional element in the steel of the present invention and may be present in amounts from 0% to 0.05%. When added in an amount of at least 0.0001%, boron forms boron nitrides and imparts additional strength to the steel of the present invention.

[0039] Calcium may optionally be present in the steel of the present invention, and may be 0.001% to 0.01%. Calcium contributes to the refining of steel by binding harmful sulfur contents into a globular form, thereby hindering the harmful effects of sulfur.

[0040] Other elements, such as Pb or Sb, can be added alone or in combination in the following proportions: Pb ≤ 0.2% and Sb ≤ 0.2%. These elements, up to the maximum content level shown, enable grain refinement during solidification. In a preferred embodiment, the Sn content is less than 0.04%.

[0041] The remaining portion, which is steel, consists of iron and unavoidable impurities produced during processing.

[0042] The microstructure of non-oriented electrical steel will now be described in detail, with all percentages expressed as area fractions.

[0043] The microstructure consists of ferrite. The steel of the present invention has a recrystallized microstructure region of 80% to 100% by area fraction, wherein the average grain size is 20 to 110 micrometers. The high recrystallization degree is attributed to uniform silicon enrichment, which improves the magnetic properties of the steel of the present invention. The controlled grain size ensures mechanical properties in both the transverse and rolling directions. The preferred recrystallization degree is 90% to 100%. The preferred average grain size of the present invention is 20 to 100 micrometers, more preferably 20 to 90 micrometers.

[0044] The steel of the present invention may have a non-recrystallized microstructure region of 0% to 20% by area fraction, and preferably a non-recrystallization degree of 0% to 10%, more preferably 0% to 5%.

[0045] In addition to the microstructures mentioned above, the microstructure of non-oriented electrical steel does not contain microstructure components such as martensite, bainite, pearlite, and cementite.

[0046] The steel according to the invention can be manufactured by any suitable method. However, by way of non-limiting example, the method according to the invention, which will be described in detail, is preferred.

[0047] Such a preferred method involves providing a steel semi-finished casting having the chemical composition of the steel according to the invention. The casting can be made into steel ingots, or continuously into the form of thin slabs or thin strips, i.e., for any form of casting, the thickness ranges from about 240 mm or less.

[0048] For example, castings in slab form are produced using the chemical composition according to the invention, and then the slabs are 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 become too high. Above 1250°C, the high-silicon steel becomes very soft and may exhibit some sagging, thus becoming difficult to handle. Preferably, the slab reheating temperature is 1080°C to 1200°C, more preferably 1120°C to 1190°C.

[0049] The reheated slab is then subjected to hot rolling, wherein the hot rolling finish temperature affects the final hot-rolled microstructure, and this occurs between 800°C and 950°C. When the finish rolling temperature is below 800°C, recrystallization is limited, and the microstructure is highly deformed. Above 950°C, this would mean more impurities in the solid solution, and potentially precipitation and deterioration of magnetic properties. Preferably, the finish rolling temperature is between 820°C and 920°C, more preferably between 840°C and 900°C.

[0050] The hot-rolled steel sheet obtained in this manner is then immediately cooled to the coiling temperature of the hot-rolled steel sheet at a cooling rate of at least 10°C / second, which also applies to the hot-rolled steel sheet; this occurs at 500°C to 600°C. For the steel of the present invention, coiling at temperatures below 500°C will not result in a suitable distribution and size of precipitates. Above 600°C, a thick oxide layer will appear, which will cause difficulties for subsequent processing steps such as cold rolling and / or pickling. Preferably, the cooling rate will be less than or equal to 200°C / second, and more preferably, the cooling rate will be from 12°C / second to 75°C / second. Preferably, the coiling temperature is from 510°C to 590°C, more preferably from 530°C to 580°C.

[0051] The coiled hot-rolled steel sheet is then cooled to room temperature and then subjected to optional hot-roll annealing.

[0052] The hot-rolled steel sheet can be subjected to an optional scale removal step to remove the scale formed during hot rolling prior to optional hot-roll annealing. The hot-rolled sheet is then subjected to optional hot-roll annealing at a temperature of 650°C to 1100°C, preferably for at least 10 seconds and no more than 96 hours, with the temperature preferably maintained at 700°C to 1070°C, and more preferably 720°C to 1050°C. Subsequently, the optional scale removal step of the hot-rolled steel sheet can be performed, for example, by pickling the sheet.

[0053] 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.

[0054] The hot-rolled steel sheet is then subjected to cold rolling with a thickness reduction rate of 50% to 95% to obtain a cold-rolled steel sheet. Preferably, the thickness reduction rate is 60% to 95%, and more preferably 75% to 95%.

[0055] Subsequently, the cold-rolled steel sheet is heat-treated, which will impart the desired mechanical properties and microstructure to the steel of this invention.

[0056] The cold-rolled steel sheet is then heated, starting from room temperature, and heated at a heating rate HR1 of at least 1°C / second to an annealing temperature T of 900°C to 1100°C, preferably 950°C to 1080°C, and more preferably 980°C to 1050°C. 均热 In a preferred embodiment, the heating rate HR1 for heating is at least 2°C / second, and more preferably at least 5°C / second.

[0057] Cold-rolled steel sheet at T 均热 Hold for 10 to 5000 seconds to ensure 80% to 100% recrystallization.

[0058] The cold-rolled steel sheet is then cooled, with the cooling process starting 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 / second to 150°C / second. In a preferred embodiment, the cooling rate CR1 is 3°C / second to 120°C / second. The preferred T1 temperature is 20°C to 200°C.

[0059] The resulting cold-rolled steel sheet has a thickness of 0.21 mm to 0.26 mm, more preferably 0.22 mm to 0.25 mm, and even more preferably 0.23 mm to 0.25 mm.

[0060] The cold-rolled steel sheet is then cooled to room temperature to obtain non-oriented electrical steel sheet.

[0061] The non-oriented electrical steel sheet of the present invention may optionally be coated with an insulating layer, an organic coating or an inorganic coating or a combination thereof to improve insulation.

[0062] Example

[0063] The tests, embodiments, graphic examples, and tables presented herein are non-limiting in nature and should be considered for illustrative purposes only, and will demonstrate advantageous features of the invention.

[0064] Table 1 summarizes the steel plates made from steels with different compositions, which were produced according to the process parameters described in Table 2. Table 3 then summarizes the evaluation results of the obtained properties.

[0065] The nitrogen content of all steels in Table 1 is less than 0.09%.

[0066] Table 2 summarizes the hot rolling and annealing process parameters for applying the mechanical and magnetic properties required to impart the steels in Table 1 to become non-oriented electrical steels to cold-rolled steel sheets. All inventive steels from I1 to I3 were cooled at a cooling rate of 15°C / s after hot rolling, and all inventive steels (i.e., I1 to I6) were subjected to hot-roll annealing at 815°C for 12 hours after coiling. Furthermore, for the inventive examples, the cold rolling reduction was 80%, and the heating rate HR1 from thereup to the annealing soaking temperature was 5°C / s. The T1 temperature for all inventive examples was 25°C, and the cooling rate CR1 was 5°C / s.

[0067] All steels produced according to the parameters in Table 2 exhibited recrystallized microstructures with recrystallization of greater than 95% and grain sizes ranging from 20 μm to 110 μm.

[0068] Table 1 :

[0069]

[0070] Table 2 :

[0071]

[0072] Table 3

[0073] The results of various mechanical tests performed according to standards are summarized. Ultimate tensile strength, total elongation, and yield strength were measured according to NF EN ISO 6892-1, and J50 magnetic properties and total iron loss at 1 T and 400 Hz were measured according to IEC 60404-2. Eddy current losses were calculated using the Bertotti method, as published by Giorgio Berttoti in his paper entitled "General Properties of Power Losses in Soft Ferromagnetic Materials" in IEEE TRANSACTIONS ON MAGNETICS, Vol. 24, No. 1, January 1988. Equation 2 determines the losses caused by (P... 经典 The classical loss denoted by is referred to as eddy current loss for the purposes of this invention.

[0074] The average grain size of recrystallized microstructures was measured using the linear intercept method according to ASTM E112 96(02) standard.

[0075]

Claims

1. A non-oriented electrical steel sheet, said non-oriented electrical steel sheet having a composition comprising the following elements: expressed as a percentage by weight, 0.0001% ≤ Carbon ≤ 0.007% 0.30% ≤ Manganese ≤ 0.7% 3% ≤ Silicon ≤ 3.6% 0.4% ≤ Aluminum ≤ 0.8% 0.05% ≤ Tin ≤ 0.15% Phosphorus ≤ 0.15% Sulfur ≤ 0.006% Nitrogen ≤ 0.09% And it can contain 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% ≤ Antimony ≤ 0.2% The remaining component consists of iron and unavoidable impurities caused by processing. The microstructure of the steel sheet is composed of ferrite and contains 80% to 100% recrystallized microstructure and 0% to 20% non-recrystallized microstructure by area fraction. The average grain size of the recrystallized microstructure is 20 micrometers to 110 micrometers. 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, which is 25% to 35% when calculated according to the Bertotti method.

2. The non-oriented electrical steel sheet according to claim 1, wherein the composition comprises 3.1% to 3.5% silicon.

3. The non-oriented electrical steel sheet according to any one of claims 1 or 2, wherein the composition comprises 0.002% to 0.007% carbon.

4. The non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the composition comprises 0.5% to 0.7% aluminum.

5. The non-oriented electrical steel sheet according to any one of claims 1 to 4, wherein the composition comprises 0.35% to 0.65% 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 non-oriented electrical steel sheet according to any one of claims 1 to 6, wherein the amount of recrystallized microstructure is 90% to 100%.

8. The non-oriented electrical steel sheet according to any one of claims 1 to 7, wherein the ultimate tensile strength of the steel sheet is at least 520 MPa.

9. The non-oriented electrical steel sheet according to any one of claims 1 to 8, wherein the yield strength of the non-oriented electrical steel sheet in both the transverse direction and the rolling direction is 400 MPa or greater.

10. The non-oriented electrical steel sheet according to any one of claims 1 to 9, wherein the total elongation of the steel sheet is at least 9%.

11. A method for producing non-oriented electrical steel sheet according to any one of claims 1 to 10, comprising the following sequential steps: - Provides a steel composition according to any one of claims 1 to 5; - The semi-finished product is then reheated to a temperature of 1050°C to 1250°C; - The semi-finished product is rolled, wherein the hot rolling finishing temperature should be 800°C to 950°C, to obtain hot-rolled steel plate; - The hot-rolled steel plate is cooled immediately after hot rolling is completed; - The hot-rolled steel sheet is then cooled from the end of hot rolling to a coiling temperature range of 500°C to 600°C at a cooling rate of at least 10°C / second. - The hot-rolled steel sheet is then wound within a winding temperature range of 500°C to 600°C; - Optionally, the hot-rolled steel sheet is subjected to an oxide scale removal process; - Optionally, hot-rolled steel sheets are subjected to hot annealing at 650°C to 1100°C for 10 seconds to 96 hours; - Optionally, the hot-rolled steel sheet is subjected to an oxide scale removal process; - The hot-rolled steel sheet is cold-rolled at a reduction rate of 50% to 95% to obtain a cold-rolled steel sheet; - The cold-rolled steel sheet is then annealed, wherein the heating for annealing starts from room temperature and extends to an annealing temperature range of 900°C to 1100°C. 均热 The heating rate HR1 is at least 1 °C / second; - Then anneal at the annealing temperature for 10 to 5000 seconds; - The cold-rolled steel sheet is then cooled from the annealing temperature to a temperature T1 of 300°C to 20°C, wherein the cooling rate CR1 is 1°C / second to 150°C / second; - Then cool to room temperature to obtain non-oriented electrical steel sheet.

12. The method of claim 11, wherein the T used for annealing 均热 The temperature ranges from 950℃ to 1080℃.

13. The method according to claim 11 or 12, wherein the temperature T1 is from 200°C to 20°C.

14. The method according to any one of claims 11 to 13, wherein the cooling rate CR1 is from 3°C / second to 120°C / second.

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