High magnetic induction non-oriented electrical steel sheet and method for manufacturing the same

Abstract

The present application discloses a high magnetic induction non-oriented electrical steel sheet, which contains Fe and inevitable impurities, and further contains chemical elements with mass percentage as follows: C≤0.003%, Si: 1.2-3.0%, Mn: 0.1-0.6%, P: 0.01-0.15%, Al: 0.1-0.4%, Ni: 0.05-1.0%; and satisfies Si+Al: 1.3-3.2%; and does not contain Sn and Sb. In addition, the present application further discloses a manufacturing method of the above high magnetic induction non-oriented electrical steel sheet, which comprises the following steps: (1) smelting and casting; (2) heating, rough rolling, finish rolling and coiling: wherein the thickness of the intermediate blank after rough rolling is controlled to be 20-45 mm, and the thickness of the sheet after finish rolling is 1.2-2.0 mm; and after coiling, aging treatment is carried out in the range of 550-650 ℃ during temperature drop for 1-4 h, so that the proportion of equiaxed crystal with the ratio between long and short axes between 1.0-4.0 in the microstructure of the sheet is ≥75%; (3) pickling; (4) primary cold rolling; (5) continuous annealing; (6) insulation coating.

Description

Technical Field

[0001] This invention relates to a steel plate and a method for manufacturing the same, and more particularly to a non-oriented electrical steel plate and a method for manufacturing the same. Background Technology

[0002] As is well known, non-oriented electrical steel sheets are widely used in current technologies. Improving the magnetic induction of non-oriented electrical steel sheets can effectively reduce copper losses in motors, compressors, and EI cores, thereby achieving energy saving and consumption reduction. Therefore, in order to effectively improve the magnetic induction of finished non-oriented electrical steel sheets, those skilled in the art usually improve the recrystallization microstructure of hot-rolled steel sheets by reducing the Si and Al content in the steel or by adopting normalizing intermediate annealing measures to obtain a more favorable crystal texture ratio.

[0003] However, limiting the addition of Si and Al content to steel leads to a deterioration in the mechanical properties of the finished steel sheet, which is not conducive to significantly increasing the frequency and speed of power tools. Therefore, how to more effectively prepare low-cost, high-magnetic-induction, and high-strength non-oriented electrical steel sheets is of great practical significance.

[0004] In response to this need, some researchers have already conducted extensive research and achieved certain results:

[0005] For example, Chinese patent document CN104073715A, published on October 1, 2014, entitled "A High-Magnetic-Induction Non-Oriented Electrical Steel and Its Manufacturing Method," discloses a high-magnetic-induction non-oriented electrical steel. This steel, through controlling the heating rate of the normalizing heating section and the speed of the normalizing cooling section, and employing a suitable shot blasting and pickling process, provides raw materials with excellent surface quality for subsequent processes. This technical solution can increase the magnetic induction (B) by 200-500 Gauss without adding additional alloying elements or changing the finished product annealing process. 50 This improves the actual quality of iron loss by 3-5%. Of course, in patented technologies, the magnetic properties of the product can also be further improved by optimizing the annealing process, thus enhancing the magnetic flux density.

[0006] For example, Chinese patent document CN105239005A, published on January 13, 2016, entitled "A High Permeability Non-oriented Silicon Steel and its Production Method," discloses a high permeability non-oriented silicon steel with the following composition and weight percentage content: C≤0.003%, Si: 0.1-1.8%, Al≤0.99%, Mn: 0.1-0.5%, Sn: 0.005-0.08%, Cu≤0.005%, S≤0.005%. The production steps of this non-oriented silicon steel include: steelmaking followed by vacuum treatment; heating the billet after casting; normalizing after hot rolling; cold rolling after pickling; annealing of the finished product; and coating. This technical solution, while meeting magnetic performance requirements, ensures Cu+S≤0.006% and Cu / S=0.5-1.7 by controlling S and Cu through vacuum treatment; and then obtains relatively large spherical MnS-Cu2S composite inclusions through hot rolling, normalizing and specific finished product annealing processes, thereby reducing the amount of sulfides such as MnS and Cu2S, and reducing the impact of cooling stress on magnetic domains. This results in a large number of 180℃ magnetic domains or similar magnetic domains, accounting for more than 60% of the volume, thus improving the magnetic permeability of the steel. Summary of the Invention

[0007] One of the objectives of this invention is to provide a high magnetic induction non-oriented electrical steel sheet. This high magnetic induction non-oriented electrical steel sheet is based on a novel chemical composition design and optimized manufacturing process, which can obtain excellent mechanical and electromagnetic properties. Its yield strength ratio is 0.78 to 0.9, and it has the significant characteristics of high yield strength ratio, high magnetic induction, and low iron loss.

[0008] To achieve the above objectives, this invention proposes a high-magnetic-induction non-oriented electrical steel sheet, which contains Fe and unavoidable impurities, and also contains the following chemical elements in the following mass percentages:

[0009] C ≤ 0.003%, Si: 1.2–3.0%, Mn: 0.1–0.6%, P: 0.01–0.15%, Al: 0.1–0.4%, Ni: 0.05–1.0%; and satisfying Si + Al: 1.30–3.20%;

[0010] The high magnetic induction non-oriented electrical steel sheet does not contain Sn and Sb.

[0011] Furthermore, in the high magnetic induction non-oriented electrical steel sheet described in this invention, the mass percentage content of each chemical element is as follows:

[0012] C ≤ 0.003%, Si: 1.2–3.0%, Mn: 0.1–0.6%, P: 0.01–0.15%, Al: 0.1–0.4%, Ni: 0.05–1.0%; balance Fe and unavoidable impurities.

[0013] The content of Si+Al is 1.30%–3.20%.

[0014] The design principles of each chemical element in the high magnetic induction non-oriented electrical steel sheet of this invention are as follows:

[0015] C: In the high magnetic induction non-oriented electrical steel sheet of this invention, element C strongly hinders grain growth in the finished strip. It easily combines with Nb, V, Ti, etc., to form fine precipitates, thereby increasing losses and causing magnetic aging. Based on this, in order to maximize the beneficial effects of element C, the mass percentage of element C in the high magnetic induction non-oriented electrical steel sheet of this invention is controlled to C≤0.003%.

[0016] Mn: In the high magnetic induction non-oriented electrical steel sheet described in this invention, Mn can combine with S to form MnS, which can effectively reduce the magnetic damage to the steel. When the Mn content in the steel is less than 0.1%, the S-fixing effect of Mn is poor; while when the Mn content in the steel is higher than 0.6%, the manufacturing cost of the steel will increase significantly. Based on this, in order to fully utilize the beneficial effects of Mn, the mass percentage of Mn in the high magnetic induction non-oriented electrical steel sheet described in this invention is controlled between 0.1% and 0.6%.

[0017] Si: In the high magnetic induction non-oriented electrical steel sheet of this invention, adding an appropriate amount of Si element can not only improve the resistivity of the steel, but also effectively reduce the iron loss of the steel. When the Si element content in the steel is higher than 3.0%, it will significantly reduce the magnetic induction of the steel and easily lead to cold rolling strip breakage; while when the Si element content in the steel is lower than 1.2%, it will not have the effect of significantly reducing the iron loss of the steel. Based on this, in order to give full play to the beneficial effects of Si element, the mass percentage content of Si element in the high magnetic induction non-oriented electrical steel sheet of this invention is controlled between 1.2% and 3.0%.

[0018] Al: In the high magnetic induction non-oriented electrical steel sheet described in this invention, Al is an important deoxidizing element. When the Al content in the steel is less than 0.1%, it does not achieve a good deoxidation effect; while when the Al content in the steel exceeds 0.4%, it will cause difficulties in continuous casting and increase the manufacturing cost of the steel. Based on this, in order to give full play to the beneficial effects of Al, the mass percentage of Al in the high magnetic induction non-oriented electrical steel sheet described in this invention is controlled between 0.1% and 0.4%.

[0019] Furthermore, it should be noted that while controlling the mass percentage content of a single chemical element, this invention further limits the sum of the mass percentage contents of Si and Al elements, that is, the numerical range of "Si+Al" is controlled between 1.3% and 3.2%.

[0020] This is because when the total mass percentage of Si and Al elements in steel is less than 1.3%, the strength of the steel cannot be effectively improved, nor can its iron loss be reduced. Conversely, when the total mass percentage of Si and Al elements in steel is greater than 3.2%, the magnetic induction of the steel cannot be effectively improved, requiring additional normalizing intermediate annealing to improve the recrystallization microstructure of the hot-rolled steel sheet. Therefore, the key objective of this invention is to control the total mass percentage of Si and Al elements within the range of 1.3% to 3.2%, and to obtain a non-oriented electrical steel sheet with high magnetic induction, low iron loss, and high yield strength ratio without using normalizing intermediate annealing.

[0021] To address this issue, in the high-magnetic-induction non-oriented electrical steel sheet designed in this invention, 0.05% to 1.0% by mass of Ni is first added to the steel. Preferably, the Ni content can be controlled between 0.1% and 0.5%. The purpose of adding Ni to the steel is that Ni is a ferromagnetic element with properties similar to Fe. Adding 0.05% or more of Ni to the steel can significantly improve the magnetic induction intensity of the steel. However, excessive Ni should not be added to the steel, as Ni has a high market price. From an economic perspective, it needs to be limited to 1.0% or less.

[0022] Currently, in some preferred embodiments, in order to obtain better implementation results, the mass percentage content of Ni element can be further preferably controlled between 0.1% and 0.5%.

[0023] Furthermore, in the high magnetic induction non-oriented electrical steel sheet designed in this invention, phosphorus (P) is also added. Adding P significantly increases the strength of the steel. When the P content in the steel exceeds 0.01%, the strength of the steel begins to increase rapidly. However, when the mass percentage of P in the steel exceeds 0.15%, the cold-rolling rollability of the steel is significantly reduced, leading to abnormalities such as edge cracks and strip breakage. Therefore, in the high magnetic induction non-oriented electrical steel sheet of this invention, the mass percentage of P is controlled between 0.01% and 0.15%.

[0024] Of course, in some preferred embodiments, in order to obtain better implementation results, the mass percentage content of element P can be further preferably controlled between 0.01% and 0.08%.

[0025] Furthermore, in the high magnetic induction non-oriented electrical steel sheet of the present invention, the unavoidable impurities are S≤0.004%, N≤0.0025%, and O≤0.0025%.

[0026] In the high magnetic induction non-oriented electrical steel sheet described in this invention, S, N and O elements are all impurity elements in the high magnetic induction non-oriented electrical steel sheet. They are impurity elements introduced from steel raw materials or during the production process. Under the condition that the technical conditions permit, in order to obtain steel with better performance and higher quality, the content of impurity elements in the steel should be reduced as much as possible.

[0027] In this invention, excessively high contents of S, N, and O elements in steel will adversely affect the performance of the steel. Therefore, it is necessary to strictly control the mass percentage content of S, N, and O elements in the steel, specifically: S≤0.004%, N≤0.0025%, and O≤0.0025%.

[0028] Furthermore, in the high magnetic induction non-oriented electrical steel sheet of the present invention, the mass percentage content of each chemical element satisfies at least one of the following:

[0029] Ni: 0.1-0.5%;

[0030] P: 0.01–0.08%.

[0031] Furthermore, in the high magnetic induction non-oriented electrical steel sheet described in this invention, its thickness is 0.2 to 0.5 mm.

[0032] Furthermore, in the high magnetic induction non-oriented electrical steel sheet described in this invention, its yield strength ratio is 0.78 to 0.9.

[0033] Furthermore, in the high magnetic induction non-oriented electrical steel sheet described in this invention:

[0034] When 1.30≤Si+Al≤2.20%, the iron loss P15 / 50≤3.2W / kg and the magnetic induction B50≥1.725T;

[0035] When 2.20 < Si + Al ≤ 3.20%, the iron loss P15 / 50 ≤ 3.0 W / kg and the magnetic induction B50 ≥ 1.695 T.

[0036] Accordingly, another objective of the present invention is to provide a manufacturing method for producing the above-mentioned high magnetic induction non-oriented electrical steel sheet. This manufacturing method is simple and feasible, its production operation process is convenient, and the hot-rolled steel coils prepared by hot rolling and coiling do not need to undergo normalizing intermediate annealing process. Through this manufacturing method, high magnetic induction non-oriented electrical steel sheets with excellent mechanical properties and electromagnetic properties can be obtained.

[0037] To achieve the above-mentioned objectives, this invention proposes a method for manufacturing a high-magnetic-induction non-oriented electrical steel sheet, comprising the following steps:

[0038] (1) Smelting and casting;

[0039] (2) Heating, rough rolling, finish rolling and coiling: The thickness of the intermediate billet after rough rolling is controlled to be 20-45 mm, and the thickness of the plate after finish rolling is 1.2-2.0 mm; after coiling, aging treatment is carried out in the range of 550-650℃ for 1-4 hours during the temperature drop process so that the proportion of equiaxed crystals with a ratio of long axis to short axis between 1.0 and 4.0 in the microstructure of the plate is ≥75%;

[0040] (3) Pickling;

[0041] (4) Cold rolling in one step;

[0042] (5) Continuous annealing;

[0043] (6) Insulating coating.

[0044] In this invention, the inventors optimized the chemical composition design of the steel and defined a reasonable manufacturing process. After obtaining a continuously cast billet through smelting and casting, the billet is then subjected to heating, rough rolling, finish rolling, and coiling in sequence to obtain a plate with the desired microstructure. This invention optimizes the design of the thickness of the hot-rolled rough-rolled intermediate billet and the thickness of the hot-rolled finish-rolled product. The hot-rolled steel coils after finish rolling and coiling undergo aging treatment. Combined with subsequent pickling, single-stage cold rolling, continuous annealing, and coating with an insulating coating, high magnetic induction and high yield strength ratio non-oriented electrical steel sheets can be effectively produced.

[0045] In the smelting and casting process of step (1) of the present invention, smelting and casting may specifically include four steps: "hot metal pretreatment", "converter smelting", "RH refining" and "continuous casting". Based on this process, it can be ensured that qualified continuously cast billets that meet the chemical composition design of the present invention are obtained.

[0046] In this invention, after continuous casting to form a billet, it undergoes reheating, rough rolling, finish rolling, and coiling in sequence. Based on actual chemical composition control results and considering electromagnetic and mechanical performance requirements, the thickness of the intermediate billet after hot rough rolling needs to be controlled to be 20–45 mm. At this point, by optimizing the reduction rate of the finish rolling passes and the distribution of cooling water, the thickness of the plate after hot finish rolling can be further adjusted to 1.2–2.0 mm.

[0047] It should be noted that the thinner the finished sheet after hot rolling, the smaller the heat flow gradient between the surface and core of the finished sheet under the same temperature conditions. This leads to more complete recrystallization of the hot-rolled microstructure, which is more conducive to the formation of equiaxed crystals that are more beneficial to the magnetic induction of the finished steel sheet. At this point, under higher hot rolling reduction rates, the equiaxed crystals in the hot-rolled microstructure are continuously elongated along the rolling direction, and the ratio of the long to short axis increases, generally exceeding 4.0. This increases the magnetic anisotropy of the finished steel sheet and decreases its yield strength ratio. Therefore, after hot rolling and coiling, an aging treatment of 1–4 hours is required within the cooling range of 550–650℃. Under the influence of Ni, the growth rate of equiaxed crystals along the perpendicular rolling direction is increased to reduce the ratio of the long to short axis of the equiaxed crystals along the rolling direction, ensuring that the proportion of equiaxed crystals between 1.0 and 4.0 is ≥75%. The higher the proportion of equiaxed crystals, the better, but current technology cannot achieve 100%.

[0048] In this invention, after completing the heating, rough rolling, finish rolling and coiling in step (2), there is no need for a normalizing intermediate annealing process. It can be directly pickled and cold rolled once to achieve a target thickness of 0.2 to 0.5 mm. Then, it can preferably be continuously annealed in a nitrogen and hydrogen mixed atmosphere at a temperature range of 850°C to 1000°C. The steel sheet obtained after continuous annealing is further coated with an insulating coating to obtain the finished high magnetic induction non-oriented electrical steel sheet of this invention. The yield strength ratio of this high magnetic induction non-oriented electrical steel sheet can reach 0.78 to 0.90.

[0049] Furthermore, in the manufacturing method described in this invention, in step (5), continuous annealing is performed in a temperature range of 850°C to 1000°C under a nitrogen and hydrogen mixed atmosphere.

[0050] Compared with the prior art, the high magnetic induction non-oriented electrical steel sheet and its manufacturing method described in this invention have the following advantages and beneficial effects:

[0051] In the high magnetic induction non-oriented electrical steel sheet described in this invention, the inventors designed a novel high magnetic induction non-oriented electrical steel sheet by designing a completely new chemical composition and combining it with an optimized manufacturing process.

[0052] In this invention, the inventors optimized and controlled the thickness of the hot-rolled roughing intermediate billet and the thickness of the hot-rolled finishing finished product based on a reasonable chemical composition. They also performed an aging treatment on the hot-rolled steel coils after finishing and coiling. Furthermore, the hot-rolled steel coils do not require a normalizing intermediate annealing process, making the production operation process simple. The high magnetic induction non-oriented electrical steel sheet prepared has the characteristics of high yield strength ratio, high magnetic induction, and low iron loss.

[0053] Furthermore, the technical solution designed in this invention can significantly reduce the difficulty of controlling impurity elements and harmful inclusions in steelmaking. The steel does not require the addition of trace elements Sn and Sb, which can effectively save components and has good prospects for promotion and application value. Attached Figure Description

[0054] Figure 1 The diagram schematically illustrates the relationship between the Ni content in the high magnetic induction non-oriented electrical steel sheet described in this invention and the magnetic induction intensity of the finished steel sheet.

[0055] Figure 2 The diagram schematically illustrates the relationship between the proportion of equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 and the yield strength ratio in the microstructure of the high magnetic induction non-oriented electrical steel sheet described in this invention. Detailed Implementation

[0056] The high magnetic induction non-oriented electrical steel sheet and its manufacturing method described in this invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, this explanation and description do not constitute an improper limitation on the technical solution of this invention.

[0057] Examples 1-6 and Comparative Examples 1-2

[0058] Table 1 lists the mass percentage of each chemical element in the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-2.

[0059] Table 1. (wt%, balance Fe and unavoidable impurities other than S, O, and N)

[0060]

[0061] In this invention, the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-2 were all prepared using the following steps:

[0062] (1) Smelting and casting according to the chemical composition ratio shown in Table 1: In the steelmaking process, after the blast furnace molten iron is successively subjected to molten iron pretreatment, converter smelting, RH refining and continuous casting, a qualified continuous casting billet with a nominal thickness of 230 mm with chemical composition (calculated by mass percentage) meets the claims of this invention.

[0063] (2) Heating, rough rolling, finish rolling and coiling: The obtained continuous casting billet is fed into a heating furnace for heating and temperature rise. After heating, it is taken out of the furnace and subjected to rough rolling, finish rolling and coiling. The thickness of the intermediate billet after rough rolling is controlled to be 20-45 mm, and the thickness of the plate after finish rolling is 1.2-2.0 mm. After coiling, it is subjected to aging treatment in the range of 550-650℃ for 1-4 hours during the temperature drop process, and then naturally cooled to room temperature, so that the proportion of equiaxed crystals with a ratio of long axis to short axis between 1.0 and 4.0 in the microstructure of the plate is ≥75%.

[0064] (3) Pickling: The hot-rolled steel coils obtained by the above hot rolling are not subjected to normalizing intermediate annealing, but are directly pickled.

[0065] (4) Cold rolling: The target thickness of 0.2 to 0.5 mm is produced by cold rolling in one step.

[0066] (5) Continuous annealing: Continuous annealing is carried out in a nitrogen and hydrogen mixed atmosphere, and the continuous annealing temperature range is controlled to be 850℃~1000℃.

[0067] (6) Insulating coating: Apply an insulating coating to the surface of the steel plate after continuous annealing.

[0068] In this invention, the chemical composition and related process parameters of the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 all meet the design specifications and control requirements of this invention; however, in Comparative Examples 1-2, although the comparative steel sheets of Comparative Examples 1-2 were also prepared using the above process steps, their chemical element composition and / or related process parameters contained parameters that did not conform to the design of this invention.

[0069] It is particularly important to note that in the comparative steel plates of Comparative Examples 1-2 designed in this invention, after being rolled up, they are directly cooled to room temperature naturally and are not subjected to aging treatment.

[0070] Table 2 lists the specific process parameters and final product thickness of the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-2 in the above manufacturing process.

[0071] Table 2.

[0072]

[0073]

[0074] It should be noted that when preparing steel plates using the above process steps, after completing the aging treatment in step (2), the inventors took samples of the steel plates of Examples 1-6 and Comparative Examples 1-2 respectively, and observed and analyzed the microstructure of each example and comparative example sample.

[0075] By observing and analyzing the microstructure, the proportion of equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 in the microstructure of the steel plates of each embodiment and comparative example after aging treatment can be effectively obtained, and the relevant observation and analysis results are listed in Table 3 below.

[0076] Table 3 lists the microstructure observation and analysis results of the steel plates prepared after aging treatment in Examples 1-6 and Comparative Examples 1-2.

[0077] Table 3.

[0078]

[0079] Observations revealed that in Examples 1-6 of the present invention, after the steel plate was coiled and aged during the cooling process, the proportion of equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 in the microstructure of the obtained plate was ≥75%, specifically between 75% and 96%.

[0080] Accordingly, after completing the above observation and analysis of the microstructure, in order to verify the performance of the finally prepared steel plate, the inventors took samples of the finished non-oriented electrical steel plates of Examples 1-6 and the comparative steel plates of Comparative Examples 1-2 prepared through the above steps, and conducted mechanical property and magnetic induction tests on the sample steel plates of Examples 1-6 and Comparative Examples 1-2. 50 and iron loss P 15 / 50 The test results are listed in Table 4 below.

[0081] The relevant performance testing methods are as follows:

[0082] Mechanical property test: The mechanical properties were tested based on the national standard GB / T 228.1-2010 Metallic materials, tensile testing - Part 1: Tensile testing at room temperature. The test temperature was constant at 25℃, and the specimen type was JIS 5# specimen, in order to determine the yield strength ratio of the steel plates of Examples 1-6 and Comparative Examples 1-2.

[0083] Magnetic performance testing: Based on national standard GB / T 3655-2008, the Epstein square ring method was used to test iron loss performance. The test temperature was a constant temperature of 20℃, the sample size was 30mm×300mm, the target mass was 0.5kg, and the test parameter was B. 50 The magnetic induction B of the steel plates from Examples 1-6 and Comparative Examples 1-2 was thus measured. 50 .

[0084] Iron loss performance testing: Based on the national standard GB / T 3655-2008, the Epstein square method was used to test the iron loss performance. The test temperature was a constant temperature of 20℃, the sample size was 30mm×300mm, the target mass was 0.5kg, and the test parameter was P. 15 / 50 The iron loss P of the steel plates from Examples 1-6 and Comparative Examples 1-2 was thus measured. 15 / 50 .

[0085] Table 4 lists the yield strength ratio and magnetic induction B of the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-2. 50 and iron loss P 15 / 50 The test results.

[0086] Table 4.

[0087]

[0088] As shown in Table 4 above, in this invention, the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 possess excellent mechanical and electromagnetic properties, with a yield strength ratio between 0.78 and 0.90, and a magnetic induction B... 50 Between 1.694 and 1.742 T, the iron loss P 15 / 50 Between 1.82 and 3.14 W / kg, its overall performance is significantly better than that of the comparative steel plates in Comparative Examples 1-2. Comparative Examples 1-2 did not meet the conditions specified in this technical solution, therefore their implementation effect was inferior to that of this invention.

[0089] It should be noted that in Examples 1-6 of this invention, when 1.30 ≤ Si + Al ≤ 2.20% (Examples 1 and 4), the iron loss P 15 / 50 All ≤3.2W / kg, magnetic induction B 50 All ≥1.725T;

[0090] When 2.20 < Si + Al ≤ 3.20% (Examples 2, 3, 5, and 6), the iron loss P 15 / 50 All ≤3.0W / kg, magnetic induction B 50 All are ≥1.695T.

[0091] Based on the data listed in Tables 1, 2, 3 and 4 above, the two comparative examples prepared in this invention can be further analyzed and explained.

[0092] In Comparative Example 1, the Ni content in the steel was 0.02%, lower than the lower limit requirement of 0.05% in this invention, and no aging treatment of 1–4 hours was performed within the temperature drop range of 550–650°C, followed by natural cooling to room temperature. As a result, the proportion of equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 in the microstructure of the plate was only 63%, lower than the lower limit requirement of 75% in this invention. Accordingly, the yield strength ratio of this comparative steel in Comparative Example 1 was only 0.64, which does not meet the lower limit requirement of 0.78 in this invention.

[0093] In Comparative Example 2, the P content in the steel was 0.008%, lower than the lower limit requirement of 0.01% of this invention; the Al content in the steel was 0.44%, higher than the upper limit requirement of 0.4% of this invention; and no aging treatment of 1–4 hours was performed within the temperature range of 550–650°C during the cooling process, followed by natural cooling to room temperature. As a result, the proportion of equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 in the microstructure of the plate was only 73%, which is lower than the lower limit requirement of 75% of this invention. Accordingly, the yield strength ratio of this comparative steel in Comparative Example 2 was only 0.75, which does not meet the lower limit requirement of 0.78 of this invention.

[0094] Figure 1 The diagram schematically illustrates the relationship between the Ni content in the high magnetic induction non-oriented electrical steel sheet described in this invention and the magnetic induction intensity of the finished steel sheet.

[0095] like Figure 1 As shown, for silicon steel with 3% Si, the magnetic induction intensity increases rapidly with the increase of Ni content, and can reach 1.71T or above when the Ni content reaches 0.05%. Then, with the continued increase of Ni content, the magnetic induction intensity continues to increase slowly and remains at 1.72-1.73T.

[0096] Figure 2 The diagram schematically illustrates the relationship between the proportion of equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 and the yield strength ratio in the microstructure of the high magnetic induction non-oriented electrical steel sheet described in this invention.

[0097] like Figure 2 As shown, the proportion of equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 in the microstructure (the proportion of equiaxed crystals) is positively correlated with the yield strength ratio.

[0098] In the high-magnetic-induction non-oriented electrical steel sheet designed in this invention, as the proportion of qualified equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 in the microstructure increases, the yield strength ratio of the steel increases accordingly. When the proportion of qualified equiaxed crystals reaches 75%, the yield strength ratio of the steel will be greater than 0.78, and will fluctuate within the range of 0.78-0.90 depending on the chemical composition and production process of the steel.

[0099] It should be noted that the scope of protection of the prior art in this invention is not limited to the embodiments given in this application. All prior art that does not contradict the solution of this invention, including but not limited to prior patent documents, prior publications, prior public uses, etc., can be included in the scope of protection of this invention.

[0100] Furthermore, the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0101] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A high-magnetic-induction non-oriented electrical steel sheet, characterized in that, Its mass percentage content of each chemical element is as follows: C ≤ 0.003%, Si: 1.2–3.0%, Mn: 0.1–0.6%, P: 0.01–0.15%, Al: 0.1–0.4%, Ni: 0.05–1.0%; the balance being Fe and unavoidable impurities; and satisfying Si + Al: 1.30–3.20%. The yield strength ratio of the high magnetic induction non-oriented electrical steel sheet is 0.78 to 0.

9.

2. The high magnetic induction non-oriented electrical steel sheet as described in claim 1, characterized in that, Among the unavoidable impurities, S≤0.004%, N≤0.0025%, and O≤0.0025%.

3. The high magnetic induction non-oriented electrical steel sheet as described in claim 1, characterized in that, Its mass percentage content of each chemical element satisfies at least one of the following conditions: Ni: 0.1–0.5%; P：0.01～0.08%。 4. The high magnetic induction non-oriented electrical steel sheet as described in claim 1, characterized in that, Its thickness is 0.2 to 0.5 mm.

5. The high magnetic induction non-oriented electrical steel sheet as described in claim 1, characterized in that: When 1.30 ≤ Si + Al ≤ 2.20%, the iron loss P 15 / 50 ≤3.2W / kg, magnetic induction B 50 ≥1.725T; When 2.20 < Si + Al ≤ 3.20%, the iron loss P 15 / 50 ≤3.0W / kg, magnetic induction B 50 ≥1.695T.

6. A method for manufacturing a high-magnetic-induction non-oriented electrical steel sheet as described in any one of claims 1-5, characterized in that, Including the following steps: Smelting and casting; Heating, rough rolling, finish rolling, and coiling: The thickness of the intermediate billet after rough rolling is controlled to be 20–45 mm, and the thickness of the plate after finish rolling is 1.2–2.0 mm; after coiling, an aging treatment is performed at 550–650℃ for 1–4 hours during the temperature drop process to ensure that the proportion of equiaxed crystals with a major-to-minor axis ratio between 1.0 and 4.0 in the microstructure of the plate is ≥75%. Pickling; One-time cold rolling; Continuous annealing; Insulating coating.

7. The manufacturing method as described in claim 6, characterized in that, In the continuous annealing step, continuous annealing is carried out in a nitrogen and hydrogen mixed atmosphere within a temperature range of 850℃ to 1000℃.

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