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

Abstract

The present invention relates to a non-oriented electrical steel sheet containing, in weight percent, the following elements: 0.0001% ≤ carbon ≤ 0.005%, 0.2% ≤ manganese ≤ 0.3%, 3.1% ≤ silicon ≤ 3.6%, 0.6% ≤ aluminum ≤ 1%, phosphorus ≤ 0.15%, sulfur ≤ 0.006%, nitrogen ≤ 0.09%, and 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%. We handle non-oriented electrical steel sheets having a structure that may contain 0% ≤ tin ≤ 0.2% and 0% ≤ antimony ≤ 0.2%, wherein the remainder of the composition consists of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet is made of ferrite, and comprises, in area fraction, 80% to 100% recrystallized microstructure and 0% to 20% non-recrystallized microstructure, the average grain size of the recrystallized microstructure is 20 to 110 microns, and the percentage of eddy current loss in total iron loss measured at 1T and 400Hz according to IEC 60404-2 standard is 30% to 35% when calculated according to the Bertotti method.

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 having excellent mechanical properties and low iron loss, specifically low eddy current loss, and a method for manufacturing the same.

Background Art

[0002] Therefore, intensive research and development efforts have been devoted, and due to the worldwide increase in energy conservation of electrical appliances, higher performance characteristics are required for using non-oriented electrical steel sheets as the core material of electrical machines. In recent years, in particular, as motors used in electric vehicles (electric vehicle), etc., the demand for small and high-output motors has been increasing. Such an electric vehicle motor is designed to enable high-speed rotation, thereby obtaining high torque while having the least possible losses. This requires a light, highly efficient non-oriented electrical steel having low losses as its main characteristic. Finding a balance between loss, magnetic permeability, polarization, thermal conductivity, tensile strength, and yield strength is essential for non-oriented electrical steel.

[0003] The lower the iron loss in an electrical machine, the higher the efficiency of the electrical machine. Therefore, to reduce the amount of iron loss in an electrical machine, the manufacturers of electrical machines have several options, and their main option is to reduce either the hysteresis loss or the eddy current loss to improve the efficiency of the electrical machine. Progress is often achieved by a combination of these two approaches. The present invention relates to the second option, i.e., reducing the eddy current loss for an electrical machine. There are two options for reducing the eddy current loss.

[0004] The first approach involves reducing the thickness of the steel plates used in electrical machinery, such as having a thickness of less than 0.35 mm or thinner. Unfortunately, this solution has limitations due to the reduction in the lamination ratio, which decreases the torque achievable for a given machine height, as well as a very significant reduction in the rigidity of certain automotive parts, and the emergence of acoustic problems that cause discomfort to the occupants.

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

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

[0007] U.S. Patent Application Publication No. 2021 / 371948 describes a non-oriented electrical steel sheet, 4.5 × 10 -6This is a non-oriented electrical steel sheet having the following average magnetostriction λp-p at 400 Hz and 1.0 T, and an area ratio of recrystallized crystal grains in the cross-section of the steel sheet in the rolling direction of the sheet of 40 to 95%, and containing, by mass%, C: 0.005% or less, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, Al: 3.0% or less, P: 0.20% or less, S: 0.005% or less, N: 0.005% or less, Ti: 0.003% or less, V: 0.005% or less, and Nb: 0.005% or less, and satisfying Si-2A1-Mn≧0, and subjecting a steel slab to hot rolling, hot-rolled sheet annealing, appropriate cold rolling and finish annealing conditions to obtain an average grain size of 10 to 40 microns, and motor cores are manufactured from such a steel sheet. The specification of U.S. Patent Application Publication No. 2021 / 371948 does not demonstrate total elongation or eddy current losses at all.

[0008] European Patent Application Publication No. 4265749 discloses an isotropic electromagnetic steel sheet and a method for manufacturing the same, which appropriately add Mo, Ti, and Nb and control the time in a specific temperature range during the cooling process after final annealing to suppress the formation of fine carbonitrides. Therefore, the invention relates to an isotropic electromagnetic steel sheet having excellent magnetic properties and strength and a method for manufacturing the same.

[0009] European Patent Application Publication No. 2657357 discloses an isotropic electromagnetic steel sheet having high strength characteristics capable of withstanding high stress acting on a high-speed rotating device and low core loss magnetic properties for energy efficiency improvement, and a method for manufacturing the same.

[0010] European Patent Application Publication No. 4079893 discloses an isotropic electromagnetic steel sheet and a method for manufacturing the same. Specifically, the invention relates to an isotropic electromagnetic steel sheet and a method for manufacturing the same, which appropriately add As and P and improve the magnetic properties by improving the structure.

[0011] European Patent Application Publication No. 4265745 discloses an isotropic electromagnetic steel sheet in which the formation of fine carbonitrides is suppressed by appropriately adding Mo, Ti, and Nb and by bubbling in the molten steel manufacturing process.

[0012] European Patent No. 3209807 relates to a method for manufacturing an Fe-Si electromagnetic steel sheet exhibiting magnetic properties. This method depends on specific Sn addition to achieve the target magnetic property values.

[0013] Chinese Patent Application Publication No. 115198198 discloses an isotropic silicon steel for high-speed motors, the chemical composition of which, in weight %, is C ≦ 0.0020%, S ≦ 0.0010%, N ≦ 0.0030%, Si: 3.0 - 3.4%, Al: 0.80 - 1.0%, Mn: 0.2 - 0.4%, P ≦ 0.01%, Sn + Sb ≦ 0.004%, Nb ≦ 0.005%, V ≦ 0.005%, Ti ≦ 0.005%, Mo ≦ 0.005%, Cr ≦ 0.05%, Ni ≦ 0.05%, Cu ≦ 0.05%, the balance being Fe and unavoidable impurities, 0 < C + S + N ≦ 0.0050%, the thickness of the final product being 0.20 - 0.30 mm, and the grain size of the final product being 80 μm - 100 μm. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 371948 [Patent Document 2] European Patent Application Publication No. 4265749 [Patent Document 3] European Patent Application Publication No. 2657357 [Patent Document 4] European Patent Application Publication No. 4079893 [Patent Document 5] European Patent Application Publication No. 4265745 [Patent Document 6] European Patent No. 3209807 [Patent Document 7] Chinese Patent Application Publication No. 115198198 [Summary of the Invention] [Problems to be Solved by the Invention]

[0015] The object of the present invention is to solve these problems by producing a non-oriented electromagnetic steel sheet having a percentage of eddy current loss in the total iron loss of 30% - 35%, preferably 30% - 35% when calculated according to the Bertotti method. [Means for Solving the Problems]

[0016] In a preferred embodiment, it is also possible to achieve the following additional characteristics alone or in combination: · A tensile strength of 500 MPa or more, preferably more than 535 MPa, in both the transverse direction and the rolling direction of rolling · A yield strength of 380 MPa or more, preferably 410 MPa or more, in both the transverse direction and the rolling direction of rolling · A total elongation of 17% or more, preferably 18% or more, in both the transverse direction and the rolling direction of rolling · Magnetic polarization at 5000 A / m (J50) of 1.66 T - 1.70 T, preferably magnetic polarization at 5000 A / m (J50) of 1.66 T - 1.69 T, more preferably magnetic polarization at 5000 A / m (J50) of 1.665 T - 1.685 T.

[0017] · A total loss of 12 - 14 W / kg, preferably 12 - 13.5 W / kg, when measured at 1 T and 400 Hz.

[0018] Preferably, such steel can have good punching performance and coating properties and excellent compatibility with rolling.

[0019] Preferably, the hardness is 185 HV or more, preferably 195 HV or more.

[0020] Another object of the present invention is also to make available a method for manufacturing these sheets that is compatible with conventional industrial applications and at the same time robust against changes in manufacturing parameters.

[0021] The above objects and other advantages of the present invention will become more apparent by describing the preferred embodiments of the present invention in detail.

[0022] The chemical composition of the non-oriented electrical steel contains the following elements in weight percentages: The carbon present in the steel of the present invention is 0.0001% to 0.005%. Since carbon is a precipitate-forming element, it is harmful to the magnetic properties of this steel. Therefore, the presence of carbon in this steel is 0.0001% to 0.007%. Since carbon promotes magnetic aging, the preferred content of carbon according to the present invention is 0.001% to 0.004%, more preferably 0.001% to 0.003%.

[0023] The manganese content of the steel of the present invention is 0.2% to 0.3%. Manganese provides solid solution strengthening and reduction of iron loss by increasing the specific resistance. If the addition amount of manganese exceeds 0.3%, the magnetic flux density may decrease significantly, and the recrystallization of the steel may be inhibited during annealing. The preferred limit for the presence of manganese is 0.2% to 0.27%, more preferably 0.2% to 0.25%.

[0024] The silicon content of the steel of the present invention is 3.1% to 3.6%. Silicon is an element that contributes to increasing strength through solid solution strengthening and is a central element for reducing eddy current losses in iron loss by increasing the resistivity of steel. The above-mentioned effects require a minimum silicon content of at least 3.1%. However, if 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%, more preferably 3.2% to 3.4%.

[0025] The aluminum content is 0.6% to 1%. Aluminum can increase the electrical resistivity of the material and effectively reduce iron loss in the steel. If the aluminum content exceeds 1%, the magnetic induction of the steel is significantly reduced, which is also detrimental to the rollability of the cold-rolled steel of the present invention. The preferred limit for the presence of aluminum is 0.7% to 0.9%, more preferably 0.8% to 0.9%.

[0026] Although sulfur is not an essential element, it can be present as an impurity in steel. From the viewpoint of the present invention, the sulfur content is preferably as low as possible, but from the viewpoint of manufacturing costs, it is 0.006% or less. Furthermore, if a higher amount of sulfur is present in the steel, the sulfur will combine to form sulfides that are detrimental to the magnetic properties of the present invention.

[0027] The phosphorus content of the steel of the present invention is 0% to 0.15%, as phosphorus reduces hot and cold ductility, particularly due to its tendency to segregate at grain boundaries or to co-segregate with manganese. For these reasons, its content is limited to 0.15%, preferably 0.09% to 0.13%.

[0028] Nitrogen is limited to 0.09% to minimize the precipitation of aluminum nitrides during solidification, which are detrimental to the magnetic properties of the steel.

[0029] Titanium is an optional element, and when added to the steel of the present invention, it is present in an amount of 0% to 0.1%. Titanium forms titanium nitrides that appear during the solidification of the casting. For this reason, the amount of titanium is 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. If the titanium content is less than 0.001%, it has no effect on the steel of the present invention.

[0030] Niobium is present in the steel of the present invention at a concentration of 0% to 0.1%, and is suitable for forming carbonitrides to increase the strength of the steel of the present invention through precipitation hardening. Niobium also affects the size of microstructural components by precipitating as carbonitrides. However, niobium content exceeding 0.1% is not economically interesting due to the saturation effect.

[0031] Vanadium is present in the steel of the present invention at a concentration of 0% to 0.1%, and is effective in increasing the strength of the steel by forming carbides or carbonitrides. From an economic standpoint, the upper limit is 0.1%.

[0032] Chromium is used in the steel of the present invention. original It is simple, 0.01% The concentration is approximately 1%. Chromium strengthens steel through solid solution reinforcement, but using it in concentrations exceeding 1% impairs the steel's magnetic properties. 。

[0033] Molybdenum is an optional element that constitutes 0% to 0.5% of the steel of the present invention.

[0034] Mo has the effect of reducing iron loss by coarsening carbides. When Mo exceeds 0.5%, the effect of improving iron loss saturates.

[0035] Tungsten is an optional element that constitutes 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, if the amount added is less than 0.001% by mass, the above effect cannot be fully obtained, while if the amount added exceeds 0.1% by weight, the effect of improving iron loss saturates.

[0036] Cobalt is an optional element that constitutes 0% to 1% of the steel of the present invention. Cobalt is an element that increases the magnetic moment of Fe alloys, thereby increasing magnetic flux density and reducing iron loss. However, if the amount added is less than 0.01% by weight, the above effects cannot be fully obtained, while if the amount added exceeds 1% by weight, the raw material costs increase significantly.

[0037] Arsenic is an optional element that constitutes 0% to 0.05% of the steel of the present invention. As is a grain boundary segregation element that improves texture and thereby reduces iron loss. The above effect is obtained by adding 0.001% by weight or more. 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, it is preferable that As be added in the range of 0.001 to 0.05% by weight.

[0038] Nickel may be added in an amount of 0% to 1% as an optional element to increase the strength of the steel of the present invention and to improve its strength and elongation. However, if the content exceeds 1%, nickel will cause a decrease in ductility. In preferred embodiments, the nickel content is kept below 0.04%.

[0039] Copper is used to increase the strength and elongation of the steel of the present invention. original As 0.01% It can be added in amounts of ~1%. However, if the content exceeds 1%, copper can degrade the surface morphology. 。

[0040] Boron is an optional element for the steel of the present invention and may be present in amounts of 0% to 0.05%. Boron forms boronitrides, and when added in an amount of at least 0.0001%, it imparts further strength to the steel of the present invention.

[0041] Calcium may be optionally present in the steel of the present invention, in amounts ranging from 0.001% to 0.01%. Calcium contributes to the refining of the steel by binding harmful sulfur-containing substances in a spherical manner, thereby delaying the harmful effects of sulfur.

[0042] 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 indicated maximum content levels, these elements allow for grain refinement during solidification. In preferred embodiments, the Sn content is less than 0.04%.

[0043] The remainder of steel's composition consists of iron and unavoidable impurities resulting from processing.

[0044] Here, we will describe the microstructure of non-oriented electrical steel in detail, but all percentages are area fractions.

[0045] The microstructure is made from ferrite. The steel of the present invention has a recrystallized microstructure region with an area fraction of 80% to 100%, having crystal grains with an average grain size of 20 to 110 microns. The recrystallized structure with a high degree of recrystallization is due to homogeneous silicon enrichment, which improves the magnetic properties of the steel of the present invention. The controlled grain size ensures mechanical properties both perpendicular to and in the rolling direction. The preferred degree of recrystallization is 90% to 100%. The preferred average grain size for the present invention is 20 to 100 microns, more preferably 20 to 90 microns.

[0046] The steel of the present invention may have a non-recrystallized microstructure region of 0% to 20% in area fraction, with a preferred degree of non-recrystallization being 0% to 10%, more preferably 0% to 5%.

[0047] In addition to the microstructure described above, the microstructure of non-oriented electrical steel does not contain microstructure components such as martensite, bainite, pearlite, and cementite.

[0048] The steel according to the present invention can be manufactured by any suitable method. However, as a non-limiting example, it is preferable to use the method according to the present invention, which is detailed below.

[0049] Such a preferred method lies in providing a semi-finished casting of steel having the chemical composition of the steel according to the present invention. The casting may be in the form of an ingot, or in the form of a continuous thin slab or thin strip, i.e., a thickness in the range of less than about 240 mm for any form of the casting.

[0050] For example, a casting in the form of a slab is cast with the chemical composition according to the present invention and then reheated, with the slab reheating temperature being between 1050°C and 1250°C until the temperature is uniform throughout the slab. Below 1050°C, rolling becomes difficult and the force on the mill becomes too high. Above 1250°C, the high-silicon grade becomes very soft and may exhibit some deflection, making it difficult to handle. Preferably, the slab reheating temperature is between 1100°C and 1200°C, more preferably between 1150°C and 1200°C.

[0051] The reheated slab is subjected to hot rolling. This hot rolling finish temperature plays a role in the final hot-rolled microstructure and is performed at 750°C to 850°C. If the finish rolling temperature is below 750°C, recrystallization is limited and the microstructure is highly deformed. If it is above 850°C, it means that there will be more impurities in the solid solution, which may result in precipitation and deterioration of magnetic properties. Preferably, the finish rolling temperature is 780°C to 850°C, more preferably 800°C to 850°C.

[0052] Next, the hot-rolled steel sheet obtained in this manner is immediately cooled at a cooling rate of at least 10°C / second to the coiling temperature of the hot-rolled steel sheet, which also serves the same purpose as the hot-rolled steel sheet, and the cooling is carried out at 480°C to 560°C. 480℃Winding at temperatures below 560°C does not result in a suitable distribution and size for the steel precipitates of the present invention. Above 560°C, a thick oxide layer appears, causing difficulties in subsequent processing steps such as cold rolling and / or pickling. Preferably, the cooling rate is 200°C / sec or less, and more preferably, the cooling rate is 12°C / sec to 75°C / sec. Preferably, the winding temperature is 490°C to 550°C, and more preferably, 500°C to 550°C.

[0053] Next, after the rolled hot-rolled steel sheet has cooled to room temperature... heat It will be used for annealing rolled plates.

[0054] The hot-rolled steel sheet may be subjected to an optional descaling process to remove scale formed during hot rolling, prior to optional hot-rolled sheet annealing. The hot-rolled sheet is then subjected to an optional hot-rolled sheet annealing, which is carried out at a temperature of 650°C to 1100°C, preferably for at least 10 seconds and 96 hours or less, and the temperature is preferably maintained at 700°C to 1070°C, more preferably 720°C to 1050°C. Subsequently, the optional descaling process of the hot-rolled steel sheet may be carried out, for example, through pickling of such a sheet.

[0055] Therefore, the resulting hot-rolled steel sheet may have a thickness of any choice between 0.8 mm and 3.5 mm, preferably between 0.9 mm and 3 mm, and more preferably between 1 mm and 2.8 mm.

[0056] Next, this hot-rolled steel sheet is subjected to cold rolling to obtain a cold-rolled steel sheet having a thickness reduction of 50-95%. Preferably, a thickness reduction of 60-95%, more preferably 75-95%.

[0057] Subsequently, the cold-rolled steel sheet is heat-treated, which imparts the mechanical properties and microstructure required for the steel of the present invention.

[0058] Next, the cold-rolled steel sheet is heated, starting from room temperature, and the cold-rolled steel sheet is heated to an annealing temperature Tsoak of 980°C to 1150°C, preferably 990°C to 1100°C, more preferably 990°C to 1050°C, at a heating rate HR1 of at least 1°C / second. In a preferred embodiment, the heating rate HR1 for heating is at least 2°C / second, more preferably at least 5°C / second.

[0059] Cold-rolled steel sheets are kept in a soak for 10 to 5000 seconds to ensure 80% to 100% recrystallization.

[0060] Next, the cold-rolled steel sheet is cooled, starting from Tsoak, and 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 / sec to 150°C / sec. In a preferred embodiment, the cooling rate CR1 is 3°C / sec to 120°C / sec. A preferred T1 temperature is 20°C to 200°C.

[0061] The cold-rolled steel sheet obtained in this manner has a thickness of 0.24 mm to 0.29 mm, more preferably 0.24 mm to 0.28 mm, and even more preferably 0.24 mm to 0.27 mm.

[0062] Subsequently, the cold-rolled steel sheet is cooled to room temperature to obtain a non-oriented electrical steel sheet.

[0063] The non-oriented electrical steel sheet of the present invention may be optionally coated with an insulating layer, an organic coating, an inorganic coating, or a combination thereof, in order to improve insulation separation. [Examples]

[0064] The following tests, examples, symbolic illustrations, and tables presented herein are not limiting in nature and should be considered for illustrative purposes only, and illustrate advantageous features of the present invention.

[0065] Table 1 summarizes steel sheets made from steel with different compositions, and each steel sheet is manufactured according to the process parameters specified in Table 2. Subsequently, Table 3 summarizes the results of the evaluation of the obtained properties.

[0066] All steels in Table 1 had a nitrogen content of less than 0.09%.

[0067] Table 2 summarizes the hot rolling and annealing process parameters performed on cold-rolled steel sheets to impart the mechanical and magnetic properties necessary to become non-oriented electrical steel to the steels in Table 1. All steels of the present invention from I1 to I2 are cooled at a cooling rate of 15°C / second after hot rolling. Furthermore, in the embodiments of the present invention, the cold rolling reduction is 80%, and the subsequent heating rate HR1 to the annealing soaking temperature is 5°C / second. The T1 temperature for all embodiments of the present invention is 25°C, and the cooling rate CR1 is 5°C / second.

[0068] All steels produced according to the parameters in Table 2 exhibited a recrystallized microstructure with over 95% recrystallization and grain size of 20–110 μm.

[0069] [Table 1]

[0070] [Table 2]

[0071] Table 3 The results of various mechanical tests conducted in accordance with the standards are summarized. Ultimate tensile strength, total elongation, and yield strength were measured according to the NF EN ISO 6892-1 standard, and J50 magnetic properties and total iron loss at 1T and 400Hz were measured according to the IEC 60404-2 standard. Eddy current loss is calculated according to the Bertotti method, as described in the paper "General Properties of Power Losses in Soft Ferromagnetic Materials" by Giorgio Berttoti, published in IEEE TRANSACTIONS ON MAGNETICS, Vol. 24, No. 1, January 1988. Equation 2 is referred to as eddy current loss in this invention (P class Identify the classical loss represented by ).

[0072] The average grain size of the recrystallized microstructure is measured by the linear intercept method according to ASTM E112 96(02) standard.

[0073] [Table 3]

Claims

1. Non-oriented electrical steel sheet, in which the following elements are expressed as weight percent: 0.0001% ≤ Carbon ≤ 0.005% 0.2% ≤ Manganese ≤ 0.3% 3.1% ≤ Silicon ≤ 3.6% 0.6% ≤ Aluminum ≤ 1% Phosphorus ≤ 0.15% Sulfur ≤ 0.006% Nitrogen ≤ 0.09% It includes and 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% A non-oriented electrical steel sheet having a composition that may contain, the remainder of which consists of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet being made of ferrite and comprising, in area fraction, 80% to 100% recrystallized microstructure and 0% to 20% non-recrystallized microstructure, the average grain size of the recrystallized microstructure being 20 to 110 microns, and having a percentage of eddy current loss in total iron loss measured at 1 T and 400 Hz according to IEC 60404-2 standard of 30% to 35% when calculated according to the Bertotti method.

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

3. A non-oriented electrical steel sheet according to any one of claims 1 or 2, wherein the composition contains 0.001% to 0.004% carbon.

4. A non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the composition contains 0.7% to 0.9% aluminum.

5. A non-oriented electrical steel sheet according to any one of claims 1 to 4, wherein the composition contains 0.2% to 0.27% manganese.

6. A 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. A 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 steel sheet has an ultimate tensile strength of at least 500 MPa in both the direction perpendicular to rolling and the rolling direction.

9. A non-oriented electrical steel sheet according to any one of claims 1 to 8, having a yield strength of 380 MPa or more in both the direction perpendicular to rolling and the rolling direction.

10. The non-oriented electrical steel sheet according to any one of claims 1 to 9, wherein the steel sheet has a total elongation of at least 17% in both the direction perpendicular to rolling and the rolling direction.

11. A method for manufacturing a non-oriented electrical steel sheet according to any one of claims 1 to 10, The following are the sequential steps: - A step of providing a steel composition according to any one of claims 1 to 5; - A step of reheating the semi-finished product to a temperature of 1050°C to 1250°C; - A process of rolling the aforementioned semi-finished product, wherein the hot rolling finishing temperature is 750°C to 850°C, to obtain a hot-rolled steel sheet; - A process of cooling the hot-rolled sheet immediately after the hot-rolling process is completed. Next, the hot-rolled steel sheet is cooled from the hot-rolling finish to a coiling temperature range of 480°C to 560°C at a cooling rate of at least 10°C / second. - Subsequently, the hot-rolled steel sheet is wound up within the winding temperature range of 480°C to 560°C. - A step of optionally performing a scale removal process on the hot-rolled steel sheet; - A process of optionally performing hot-rolled steel sheet annealing at a temperature of 650°C to 1100°C for a period of 10 seconds to 96 hours; - A step of optionally performing a scale removal process on the hot-rolled steel sheet; - A step of obtaining a cold-rolled steel sheet by cold-rolling the hot-rolled steel sheet with a reduction ratio of 50 to 95%; - Subsequently, a step of annealing the cold-rolled steel sheet, wherein heating for annealing starts from room temperature and reaches an annealing temperature range Tsoak of 980°C to 1150°C at a heating rate HR1 of at least 1°C / second; Next, the process involves annealing at an annealing temperature for 10 to 5000 seconds; Next, a step of cooling the cold-rolled steel sheet, starting from the annealing temperature and reaching a temperature T1 of 300°C to 20°C at a cooling rate CR1 of 1°C / sec to 150°C / sec; Next, the process involves cooling to room temperature to obtain a non-oriented electrical steel sheet. Methods that include...

12. The method according to claim 11, wherein the Tsoak temperature for annealing is 990°C to 1090°C.

13. The method according to any one of claims 11 or 12, wherein the temperature T1 is 200°C to 20°C.

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

Images