High magnetic induction non-oriented electrical steel sheet and manufacturing method thereof

Abstract

The present invention discloses a high magnetic induction non-oriented electrical steel sheet, which contains, in addition to Fe and inevitable impurities, the following chemical elements in mass percentages: 0.003% or less C, 1.2-3.0% Si, 0.1-0.6% Mn, 0.01-0.15% P, 0.1-0.4% Al, and 0.05-1.0% Ni, with Si+Al being 1.30-3.20%, and does not contain Sn or Sb. In addition, the present invention discloses a method for manufacturing the above-mentioned high magnetic induction non-oriented electrical steel sheet, which includes: (1) a smelting and casting step; (2) a heating, rough rolling, finish rolling, and coiling step, in which the thickness of the intermediate slab after rough rolling is 20-45 mm, and the thickness of the plate after finish rolling is 1.2-2.0 mm, and after coiling, an aging treatment is performed at a temperature in the range of 550-650°C for 1-4 hours during the cooling process; (3) a pickling step; (4) a single-stage cold rolling step; (5) a continuous annealing step; and (6) an insulating coating application step.

Description

[Technical Field]

[0001] The present invention relates to a steel sheet and a manufacturing method thereof, and more particularly to a non-oriented electrical steel sheet and a manufacturing method thereof. [Background technology]

[0002] It is well known that non-oriented electrical steel sheets are widely used in existing technologies. Improving the magnetic induction of non-oriented electrical steel sheets effectively reduces copper loss in motors, compressors, and EI cores, contributing to the goals of energy conservation and reduced consumption. Therefore, those skilled in the art generally improve the recrystallized microstructure of hot-rolled steel sheets by reducing the Si and Al content in the steel to obtain a more favorable crystal orientation ratio, or by employing a normalizing intermediate annealing treatment, thereby effectively improving the magnetic induction of the finished non-oriented electrical steel sheets.

[0003] However, the limitations on the Si and Al content in steel result in a reduction in the mechanical performance of the finished steel sheet, and do not support significant increases in frequency and rotational speed of power tools. For this reason, more efficient production of low-cost, high-inductance, high-strength non-oriented electrical steel sheet is of great practical importance.

[0004] In response to this need, current researchers have conducted a great deal of research, and as a result, certain research results have been achieved.

[0005] For example, Patent Document 1, titled "Non-oriented Electrical Steel with High Magnetic Induction and Manufacturing Method Thereof" and published on October 1, 2014, discloses a high magnetic induction non-oriented electrical steel sheet that provides raw material with excellent sheet quality for subsequent processes by adopting an appropriate system that controls the heating rate of the normalizing heating section, the speed of the normalizing cooling section, and the shot blasting and pickling processes in cooperation with each other. This technical solution uses magnetic induction B without adding alloying elements or changing the annealing process of the finished product. 50 It can improve the magnetic field strength by 200-500 gauss and improve the physical quality level of iron loss by 3-5%. Naturally, this patented technical solution also allows for optimizing the annealing process to further improve the magnetic performance of the product, resulting in a further improvement in magnetic induction.

[0006] As another example, Patent Document 2, entitled "Non-Oriented Silicon Steel with High Magnetic Permeability and Manufacturing Method Thereof," published on January 13, 2016, discloses a non-oriented silicon steel with high magnetic permeability containing the following chemical elements in mass percentages: 0.003% or less C, 0.1-1.8% Si, 0.99% or less Al, 0.1-0.5% Mn, 0.005-0.08% Sn, 0.005% or less Cu, and 0.005% or less S. The manufacturing process for this non-oriented silicon steel includes vacuum treatment after steelmaking, heating of the cast slab after slab casting, normalizing after hot rolling, cold rolling after pickling, annealing of the finished product, and application of a coating. This technical solution achieves the magnetic properties described above through vacuum treatment to ensure that Cu+S is below 0.006% and Cu / S is 0.5-1.7, followed by hot rolling and normalizing to control S and Cu, and then through a specific annealing process for the finished product, resulting in coarser, more spherical MnS-Cu2S composite inclusions, which reduces MnS, Cu2S and other sulfides while also reducing the cooling stress on the magnetic domains, resulting in more 180°C or similar magnetic domains, accounting for 60% by volume, and thereby improving the magnetic permeability of the steel. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Chinese Patent Application Publication No. 104073715A [Patent Document 2] Chinese Patent Application Publication No. 105239005A [Non-patent literature]

[0008] [Non-Patent Document 1] Domestic standard GB-T 10561 2005 [Non-patent document 2] Domestic standard GB / T 228.1-2010 "Tensile Test of Metallic Materials Part 1: Room Temperature Tensile Test Method" [Non-patent document 3] Domestic standard GB / T 3655-2008 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a high magnetic induction non-oriented electrical steel sheet, which has excellent mechanical and electromagnetic performance with a yield ratio of 0.78-0.9 based on a new chemical composition design in cooperation with an optimized manufacturing process, and achieves the notable features of a high yield ratio, high magnetic induction, and low core loss. [Means for solving the problem]

[0010] To achieve the above object, the present invention provides a composition containing, in addition to Fe and inevitable impurities, the following chemical elements in mass percentage: Contains 0.003% or less of C, 1.2-3.0% of Si, 0.1-0.6% of Mn, 0.01-0.15% of P, 0.1-0.4% of Al, and 0.05-1.0% of Ni, with Si+Al being 1.30-3.20%; Provided is a non-oriented electrical steel sheet that does not contain Sn or Sb.

[0011] In another embodiment, the present invention relates to a steel sheet comprising the following chemical elements in mass percentage: less than 0.003% C, 1.2-3.0% Si, 0.1-0.6% Mn, 0.01-0.15% P, 0.1-0.4% Al, 0.05-1.0% Ni, the remaining percentages being Fe and unavoidable impurities, The present invention provides a non-oriented electrical steel sheet having a Si+Al content of 1.30-3.20%.

[0012] Next, the design principles of each chemical element for the high magnetic induction non-oriented electrical steel sheet according to the present invention will be described.

[0013] C: C strongly hinders grain growth in the finished steel sheet and tends to combine with Nb, V, Ti, etc. to form fine precipitates, which cause increased loss and magnetic aging. Therefore, in the high magnetic induction non-oriented electrical steel sheet according to the present invention, the C content is controlled to 0.003% or less by mass percentage.

[0014] Mn: Mn combines with S to form MnS, thereby reducing the deterioration of magnetic properties. When the Mn content is less than 0.1%, the desulfurization effect of Mn is poor, and when the Mn content exceeds 0.6%, the production cost of steel increases significantly. Based on this, in order to fully utilize the beneficial effects of Mn, the Mn content is controlled to 0.1-0.6% by mass in the non-oriented electrical steel sheet according to the present invention.

[0015] Si: Adding an appropriate amount of Si to steel not only improves the resistivity of the steel but also effectively reduces the iron loss of the steel. When the Si content in steel is higher than 3.0%, the magnetic induction of the steel significantly decreases, making the cold-rolled steel sheet more susceptible to breakage. When the Si content in steel is less than 1.2%, it is no longer possible to significantly reduce the iron loss of the steel. Based on this, in order to utilize the beneficial effects of Si, the Si content in the non-oriented electrical steel sheet according to the present invention is controlled to 1.2-3.0% by mass.

[0016] Al: Al is an important deoxidizing element. When the Al content is less than 0.1%, it is not possible to achieve a good deoxidizing effect, and when the Al content is more than 0.4%, continuous casting becomes difficult and the production cost of the steel increases. Based on this, in order to utilize the beneficial effects of Al, the Al content is controlled to 0.1-0.4% by mass in the non-oriented electrical steel sheet according to the present invention.

[0017] In addition, it should be noted that in the present invention, while controlling the mass percentage content of a single chemical element, it is also necessary to limit the sum of the mass percentage contents of Si and Al, i.e., the value of "Si+Al" is controlled to 1.3-3.2%.

[0018] This is because when the sum of the mass percentage contents of Si and Al contained in steel is less than 1.3%, it is not possible to effectively improve the strength of the steel and reduce the iron loss of the steel, and when the sum of the mass percentage contents of Si and Al contained in steel is more than 3.2%, it is not possible to effectively improve the magnetic induction of the steel, and an additional normalizing intermediate annealing is required to improve the recrystallized microstructure of the hot-rolled steel sheet.The inventors have found that by controlling the sum of the mass percentages of Si and Al within the range of 1.3-3.2%, it is possible to obtain a non-oriented electrical steel sheet with high magnetic induction, low iron loss, and a high yield ratio without using normalizing intermediate annealing conditions.

[0019] In the non-oriented electrical steel sheet according to the present invention, 0.05-1.0% by mass of Ni is added to the steel, and preferably the Ni content is controlled to 0.1-0.5%. The effect of adding Ni to steel is that Ni is a ferromagnetic element and its properties are similar to those of Fe, so adding 0.05% or more of Ni to steel can significantly improve the magnetic induction strength of the steel. However, the market price of Ni is high, and from an economical point of view, it is necessary to keep it below 1.0%, so adding an excessive amount of Ni to steel is inappropriate.

[0020] In some preferred embodiments, the mass percentage of Ni content is preferably controlled to 0.1-0.5% to obtain a more optimal performance effect.

[0021] Additionally, P is added to the non-oriented electrical steel sheet according to the present invention, and the addition of P to steel can significantly improve the strength of the steel. When the P content in steel exceeds 0.01%, the strength of the steel begins to increase rapidly. However, when the P content in steel exceeds 0.15% by mass, the cold rolling properties of the steel significantly decrease, leading to defects such as cracking and breakage of the steel sheet. Therefore, the P content in the high magnetic induction non-oriented electrical steel sheet according to the present invention is controlled to 0.01-0.15% by mass.

[0022] In some preferred embodiments, it is preferred that the P content be controlled to 0.01-0.08% by mass percentage to obtain a more optimal performance effect.

[0023] Preferably, the unavoidable impurities in the non-oriented electrical steel sheet according to the present invention are S of 0.004% or less, N of 0.0025% or less, and O of 0.0025% or less.

[0024] In the non-oriented electrical steel sheet according to the present invention, S, N, and O are impurity elements in the non-oriented electrical steel sheet, which are impurity elements introduced into the raw materials of the steel or during the manufacturing process. If technical conditions permit, the content of impurity elements in the steel should be minimized as much as possible to obtain steel with better performance and quality.

[0025] In the present invention, if the contents of S, N, and O in the steel are too high, it will have a detrimental effect on the performance of the steel. Therefore, the mass percentages of S, N, and O in the steel must be strictly controlled, specifically, S is controlled to 0.004% or less, N is controlled to 0.0025% or less, and O is controlled to 0.0025% or less. Preferably, the non-oriented electrical steel sheet according to the present invention has a composition, in mass percentage, that satisfies at least one of the following: Ni is 0.1-0.5%; P is 0.01-0.08%.

[0026] Preferably, in the non-oriented electrical steel sheet according to the present invention, the thickness of the steel sheet is 0.2-0.5 mm.

[0027] Preferably, in the non-oriented electrical steel sheet according to the present invention, the proportion of equiaxed crystals with a ratio of major axis to minor axis of 1.0 to 4.0 is 75% or more.

[0028] Preferably, in the non-oriented electrical steel sheet according to the present invention, the steel sheet has a yield ratio of 0.78-0.9.

[0029] Preferably, in the non-oriented electrical steel sheet according to the present invention, When Si+Al is 1.30% or more and 2.20% or less, iron loss P 15 / 50 is 3.2W / kg or less, and magnetic induction B 50 is 1.725T or more, When Si+Al is greater than 2.20% and less than 3.20%, iron loss P 15 / 50 is 3.0W / kg or less, and magnetic induction B 50 is 1.695T or more.

[0030] Therefore, another object of the present invention is to provide a method for manufacturing the above-mentioned non-oriented electrical steel sheet. This manufacturing method is simple and can be realized using a convenient production operation process, and the hot-rolled steel coil manufactured by hot rolling and coiling does not require an intermediate normalizing annealing process. Based on this manufacturing method, it is possible to obtain a high magnetic induction non-oriented electrical steel sheet with excellent mechanical and electromagnetic properties.

[0031] In order to achieve the above object, the present invention provides a method for manufacturing a non-oriented electrical steel sheet, which includes the following steps. (1) smelting and casting in accordance with the aforementioned composition to form a continuously cast slab; (2) subjecting the continuous casting slab to heating, rough rolling, finish rolling and coiling, in which the thickness of the intermediate slab after rough rolling is 20-45mm, and the thickness of the plate after finish rolling is 1.2-2.0mm; and after coiling, performing aging treatment at 550-650°C for 1-4 hours during the cooling process to form a hot rolled steel coil; (3) pickling the hot rolled steel coil; (4) forming a steel plate by single-stage cold rolling of the hot-rolled steel coil; (5) continuously annealing the steel sheet; (6) applying an insulating coating to the surface of the steel plate;

[0032] In the present invention, the inventors have optimized the design of the chemical composition of the steel and simultaneously defined a rational manufacturing process, which allows a continuous cast slab to be obtained after smelting and casting, and then a steel sheet with the required microstructure to be obtained through heating, rough rolling, finish rolling, and coiling in sequence. The present invention optimizes the design of the thickness of the intermediate slab after hot rolling and rough rolling, as well as the thickness of the steel sheet after hot rolling and finish rolling, provides aging treatment for the hot rolled steel coil after finish rolling and coiling, and the subsequent pickling, single-stage cold rolling, continuous annealing, and insulating coating application processes work together to effectively manufacture non-oriented electrical steel sheets with high magnetic induction and high yield ratio.

[0033] In the smelting and casting process of step (1) according to the present invention, the smelting and casting can specifically include four steps: "molten iron pretreatment," "converter smelting," "RH refining," and "continuous casting." Based on this process, it is possible to reliably obtain a qualified continuously cast slab that meets the chemical composition design of the present invention.

[0034] In the present invention, after continuous casting to obtain a slab, reheating, rough rolling, finish rolling, and coiling are carried out in sequence. The actual performance is controlled according to the chemical composition in combination with the electromagnetic and mechanical performance needs. After hot rolling and rough rolling, the thickness of the intermediate slab after rough rolling must be controlled to 20-45 mm. In this regard, by optimizing the reduction rate and cooling water distribution in the finish rolling pass, the thickness of the steel plate after hot rolling and finish rolling can be further adjusted to 1.2-2.0 mm.

[0035] It should be noted that the thinner the thickness of the steel sheet after hot rolling and finish rolling, the smaller the gradient of heat flow between the surface and core of the hot-rolled and finish-rolled steel sheet under the same temperature conditions. This allows for more complete recrystallization of the hot-rolled microstructure, which favors the formation of favorable equiaxed grains due to magnetic induction in the finished steel sheet. In this regard, under conditions of higher hot-rolling and finish-rolling reductions, the equiaxed grains in the hot-rolled structure along the rolling direction are continuously elongated, resulting in a higher long-to-short axis ratio, generally exceeding 4.0. This increases the magnetic anisotropy of the finished steel sheet and reduces its yield ratio. Therefore, after hot rolling, finish rolling, and coiling, a cooling process of 1-4 hours at 550-650°C is required. Under the effect of Ni, the growth rate of equiaxed crystals along the perpendicular rolling direction increases, and as a result, the long-to-short axis ratio of equiaxed crystals along the rolling direction is reduced, and a population ratio of 75% or more of equiaxed crystals with a ratio between 1.0 and 4.0 is achieved. In this regard, the higher the population ratio of equiaxed crystals, the better, but it is not possible to reach 100% due to the current technological limitations.

[0036] In the present invention, after the heating, rough rolling, finish rolling, and coiling in step (2), there is no need to perform the normalizing intermediate annealing process, and pickling and single-stage cold rolling can be directly performed to reach the target thickness of 0.2-0.5 mm. Subsequently, continuous annealing can be preferably performed at a temperature of 850-1000°C in a mixed atmosphere of nitrogen and hydrogen. Furthermore, an insulating coating can be applied to the steel sheet obtained after continuous annealing to obtain the finished high magnetic induction non-oriented electrical steel sheet of the present invention having a yield ratio of 0.78-0.90.

[0037] Preferably, in step (5) of the manufacturing method according to the present invention, continuous annealing is carried out at a temperature of 850-1000° C. in a mixed atmosphere of nitrogen and hydrogen.

[0038] Preferably, in step (5) of the manufacturing method according to the present invention, the nitrogen content in the mixed atmosphere of nitrogen and hydrogen is 50-70% and the hydrogen content is 30-50%.

[0039] The non-oriented electrical steel sheet and the manufacturing method thereof according to the present invention have the following advantages and other beneficial effects compared to the prior art.

[0040] In the non-oriented electrical steel sheet according to the present invention, the inventors have designed a novel high magnetic induction non-oriented electrical steel sheet by a new chemical composition design in combination with an optimized manufacturing process.

[0041] In this invention, the inventors optimized and controlled the thickness of the intermediate slab after hot rolling and rough rolling and the thickness of the finished product after hot rolling and finish rolling based on a rational chemical composition. They also performed aging treatment on the hot-rolled steel coil after finish rolling and coiling, controlling the proportion of equiaxed grains with a major-to-minor axis ratio of 1.0-4.0 in the steel coil to 75% or more, thereby improving the magnetic induction of the steel sheet and increasing the yield ratio. In addition, the hot-rolled steel coil does not require a normalizing intermediate annealing process, which simplifies the production and operation process. Therefore, the resulting high-magnetic-induction non-oriented electrical steel sheet is characterized by a high yield ratio, high magnetic induction, and low core loss.

[0042] In addition, the technical solution designed by the present invention can significantly reduce the difficulty of controlling harmful inclusions, including impurity elements, in steelmaking, and eliminates the need to add trace elements such as Sn and Sb to steel, thereby enabling effective cost reduction and having good prospects for popularization and application value. [Brief explanation of the drawings]

[0043] [Figure 1] FIG. 2 is a diagram schematically illustrating the relationship between the Ni content and magnetic induction strength of a finished steel sheet in a high magnetic induction non-oriented electrical steel sheet according to the present invention. [Figure 2] FIG. 1 is a diagram schematically illustrating the relationship between the yield ratio of a high magnetic induction non-oriented electrical steel sheet according to the present invention and the proportion of the number of equiaxed grains in the microstructure having a major axis / minor axis ratio of 1.0-4.0. DETAILED DESCRIPTION OF THE INVENTION

[0044] Hereinafter, the high magnetic induction non-oriented electrical steel sheet and the manufacturing method thereof of the present invention will be further described and illustrated with reference to the drawings and specific embodiments in this specification, however, these descriptions and illustrations do not constitute undue limitations on the technical solutions of the present invention.

[0045] Examples 1-6 and Comparative Examples 1-2 The mass percentages of each chemical element for the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-2 are listed in Table 1.

[0046] [Table 1]

[0047] In the present invention, the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-2 are manufactured using the following steps.

[0048] (1) Smelting and casting according to the chemical composition shown in Table 1: In the steelmaking process, the molten iron in the blast furnace was subjected to successive molten iron pretreatment, converter smelting, RH refining, and continuous casting so as to obtain a qualified continuously cast slab with a nominal thickness of 230 mm, the chemical composition of which (calculated in terms of mass percentage) meets the requirements of this invention.

[0049] (2) Heating, rough rolling, finish rolling, and coiling: the obtained continuous cast slab is sent into a heating furnace for heating, and after heating is completed, it is taken out of the furnace and undergoes rough rolling, finish rolling, and coiling, in which the thickness of the intermediate slab after rough rolling is controlled to 20-45mm, and the thickness of the plate after finish rolling is controlled to 1.2-2.0mm, and after coiling, during the cooling process, it is aged at 550-650℃ for 1-4 hours, and then the plate is naturally cooled to room temperature so that the number ratio of equiaxed crystals with a major axis-minor axis ratio of 1.0-4.0 is more than 75% in the plate microstructure.

[0050] (3) Pickling: After the above hot rolling and coiling, the hot-rolled steel coil was directly pickled without undergoing normalizing intermediate annealing.

[0051] (4) Single-stage cold rolling: The target thickness after single-stage cold rolling is 0.2-0.5 mm.

[0052] (5) Continuous annealing: Continuous annealing was carried out in a mixed atmosphere of nitrogen and hydrogen, and the continuous annealing temperature was controlled at 850-1000°C.

[0053] (6) Application of insulating coating: An insulating coating was applied to the surface of the steel sheet after continuous annealing.

[0054] In the present invention, the chemical compositions and related process parameters of the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 all meet the control requirements of the design specifications of the present invention, while the comparative steel sheets of Comparative Examples 1-2 are also manufactured using the above process steps, but in Comparative Examples 1-2, the composition of chemical elements and / or related process parameters do not follow the design of the present invention.

[0055] It should be noted that the comparative steel sheet of Comparative Example 1-2 designed according to the present invention was naturally cooled to room temperature immediately after coiling without undergoing aging treatment.

[0056] Table 2 lists the specific process parameters for the above manufacturing process and the final thicknesses of the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-2.

[0057] [Table 2]

[0058] It should be noted that when manufacturing steel sheets using the above process steps, specimens of each of the steel sheets of Examples 1-6 and Comparative Examples 1-2 were taken by the inventors after completion of the aging treatment in step (2), and the microstructures of the specimens of each of the examples and comparative examples were then observed and analyzed.

[0059] Through microstructural observation and analysis, it is possible to effectively obtain the number ratio of equiaxed grains with a long axis / short axis ratio between 1.0 and 4.0 in the microstructure of the steel sheets after aging treatment for each of these examples and comparative examples, and the relevant observation and analysis results are listed in Table 3 below. The observation, analysis tests, and statistical methods were performed in accordance with Non-Patent Document 1.

[0060] Table 3 lists the results of microstructural observation and analysis of the steel sheets of Examples 1-6 and Comparative Examples 1-2 produced after aging treatment.

[0061] [Table 3]

[0062] In Examples 1-6 according to the present invention, after the aging treatment of the coil steel sheet is completed during the temperature decreasing process, it is observed that the number ratio of equiaxed crystals with a major axis / minor axis ratio between 1.0 and 4.0 in the microstructure of the obtained steel sheet is all 75% or more, specifically 75-96%.

[0063] Therefore, after completing the above microstructural observation and analysis, the inventors took specimens of the finished non-oriented electrical steel sheets of Examples 1-6 and the comparative steel sheets of Comparative Examples 1-2 manufactured by the above steps in order to confirm the performance of the finally manufactured steel sheets, and measured the mechanical properties, magnetic induction B of the specimen steel sheets of Examples 1-6 and Comparative Examples 1-2. 50 , and iron loss P 15 / 50 Each of the following was tested. The relevant test results are listed in Table 4 below.

[0064] The relevant performance test methods are described below.

[0065] Mechanical performance test: In order to measure the yield ratio of the steel plate specimens of Examples 1-6 and Comparative Examples 1-2, the test temperature was set to a constant temperature of 25°C and the specimen type was JIS 5# specimen, based on Non-Patent Document 2 for mechanical performance test.

[0066] Magnetic induction performance test: Magnetic induction B of steel plate samples of Examples 1-6 and Comparative Examples 1-2 50 Based on Non-Patent Document 3, the temperature was set to 20°C, the sample size was set to 30mm x 300mm, the target mass was set to 0.5kg, and the test parameters were set to B 50 Iron loss performance tests were conducted using the Epstein method with a square frame as the core.

[0067] Iron loss performance test: Iron loss P of steel plate specimens of Examples 1-6 and Comparative Examples 1-2 15 / 50 Based on Non-Patent Document 3, the temperature was set to 20°C, the sample size was set to 30 mm x 300 mm, the target mass was set to 0.5 kg, and the test parameters were set to P 15 / 50 Iron loss performance tests were conducted using the Epstein method with a square frame as the core.

[0068] Table 4 shows the yield ratio and magnetic induction B of the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 and Comparative Examples 1-2. 50 , and iron loss P 15 / 50 The test results are listed.

[0069] [Table 4]

[0070] As shown in Table 4 above, in the present invention, the high magnetic induction non-oriented electrical steel sheets of Examples 1-6 have a yield ratio in the range of 0.78-0.90, a magnetic induction B 50 is in the range of 1.694-1.742T, iron loss P 15 / 50 The electrical conductivity of the steel sheet is in the range of 1.82-3.14 W / kg, and the steel sheet has excellent mechanical and electromagnetic properties, and its comprehensive properties are significantly superior to those of the steel sheet of Comparative Example 1-2. Furthermore, Comparative Example 1-2 does not satisfy the conditions limited by the present invention, and therefore is inferior to the practical effect of the present invention.

[0071] In Examples 1 to 6 designed according to the present invention, when Si+Al is 1.30% or more and 2.20% or less (Example 1 and Example 4), the iron loss P 15 / 50are all 3.2W / kg or less, and magnetic induction B 50 are all 1.725T or more, and Si+Al is greater than 2.20% and 3.20% or less (Examples 2, 3, 5, and 6), the iron loss P 15 / 50 are all 3.0W / kg or less, and magnetic induction B 50 It should be noted that all of the values are 1.695T or greater.

[0072] Combining the data listed in Tables 1, 2, 3 and 4 above allows for further analysis and description of two comparative examples produced in accordance with the present invention.

[0073] In Comparative Example 1, the Ni content in the steel was 0.02%, which is below the 0.05% lower limit of the design requirement of the present invention, and the steel sheet was not aged for 1-4 hours at 550-650°C during the temperature reduction process before being naturally cooled to room temperature. Therefore, the proportion of equiaxed grains with a long axis / short axis ratio of 1.0-4.0 in the microstructure of the steel sheet was only 63%, which is below the 75% lower limit of the design requirement of the present invention. Therefore, the yield ratio of the final comparative steel of Comparative Example 1 was only 0.64, which does not meet the 0.78 lower limit required by the design of the present invention.

[0074] In Comparative Example 2, the P content of the steel was 0.008%, below the lower limit of 0.01% specified in the design requirement of the present invention, the Al content was 0.44%, above the upper limit of 0.4%, and the steel sheet was not aged for 1-4 hours at 550-650°C during the temperature reduction process before being naturally cooled to room temperature. As a result, the proportion of equiaxed grains with a major axis / minor axis ratio of 1.0-4.0 in the steel sheet microstructure was only 73%, below the lower limit of 75% specified in the design requirement of the present invention. Therefore, the yield ratio of the final comparative steel of Comparative Example 2 was only 0.75, which does not meet the lower limit of 0.78 specified in the design requirement of the present invention.

[0075] FIG. 1 is a diagram schematically showing the relationship between the Ni content and magnetic induction strength of a finished steel sheet in a high magnetic induction non-oriented electrical steel sheet according to the present invention.

[0076] As shown in Figure 1, in the case of 3%-Si silicon steel, the magnetic induction strength increases sharply with increasing Ni content in the steel, and can reach 1.71 T or more at a Ni content of 0.05%. After that, the magnetic induction strength continues to increase more slowly with further increases in Ni content in the steel, but remains at 1.72-1.73 T.

[0077] FIG. 2 is a diagram schematically illustrating the relationship between the yield ratio of a high magnetic induction non-oriented electrical steel sheet according to the present invention and the proportion of the number of equiaxed grains in the microstructure having a major axis / minor axis ratio between 1.0 and 4.0.

[0078] As shown in Figure 2, the ratio of the size of the equiaxed crystals (the ratio of the number of equiaxed crystals) with a long-to-short axis ratio between 1.0 and 4.0 in the microstructure is positively correlated with the yield ratio.

[0079] In the high magnetic induction non-oriented electrical steel sheet designed according to the present invention, the yield ratio of the steel increases with an increase in the proportion of suitable equiaxed grains with a long-to-short axis ratio of 1.0-4.0 in the microstructure. When the proportion of suitable equiaxed grains reaches 75%, the yield ratio of the steel becomes greater than 0.78, and fluctuates within the range of 0.78-0.90 depending on the chemical composition and manufacturing process of the steel.

[0080] It should be noted that the part of the prior art within the protection scope of the present invention is not limited to the examples given herein. All prior art that is not inconsistent with the solution of the present invention, including but not limited to prior patent documents, prior publications, prior applications, etc., can all be included in the protection scope of the present invention.

[0081] In addition, the combinations of technical features in this disclosure are not limited to the combinations described in the claims or the combinations described in the specific examples, and all technical features described herein can be freely combined in any manner as long as they are not inconsistent with each other.

[0082] It should also be noted that the above-mentioned examples are merely specific examples of the present invention. It is clear that the present invention should not be excessively limited to such specific examples. Any changes or modifications that can be directly or easily deduced from the present disclosure by those skilled in the art are intended to fall within the protection scope of the present invention.

Claims

1. A non-oriented electrical steel sheet, which in addition to Fe and inevitable impurities contains the following chemical elements in mass percentages: 0.003% or less C, 1.2-3.0% Si, 0.1-0.6% Mn, 0.01-0.15% P, 0.1-0.4% Al, and 0.05-1.0% Ni; The content of Si+Al is 1.30-3.20%, and A non-oriented electrical steel sheet that does not contain Sn or Sb.

2. The steel sheet contains the following chemical elements in mass percentage: 0.003% or less C, 1.2-3.0% Si, 0.1-0.6% Mn, 0.01-0.15% P, 0.1-0.4% Al, 0.05-1.0% Ni, the remaining percentages being Fe and unavoidable impurities, and Si+Al is 1.30-3.20%; The non-oriented electrical steel sheet according to claim 1.

3. Among the inevitable impurities, S is 0.004% or less, N is 0.0025% or less, and O is 0.0025% or less. The non-oriented electrical steel sheet according to claim 1 or 2.

4. The steel sheet contains the following chemical elements in mass percentage: 0.1-0.5% Ni; 0.01-0.08% P, The non-oriented electrical steel sheet according to claim 1 or 2, comprising at least one of the following:

5. In the steel sheet, the number ratio of equiaxed crystals having a major axis / minor axis ratio of 1.0 to 4.0 is 75% or more. The non-oriented electrical steel sheet according to claim 1 or 2.

6. The steel plate has a thickness of 0.2-0.5 mm. The non-oriented electrical steel sheet according to claim 1 or 2.

7. The steel plate has a yield ratio of 0.78-0.

9. The non-oriented electrical steel sheet according to claim 1 or 2.

8. When Si+Al is 1.30% or more and 2.20% or less, iron loss P １５／５０ is 3.2 W / kg or less, and magnetic induction B ５０ is 1.725T or more, When Si+Al is greater than 2.20% and less than or equal to 3.20%, iron loss P １５／５０ is 3.0 W / kg or less, and magnetic induction B ５０ is 1.695T or more, The non-oriented electrical steel sheet according to claim 1 or 2.

9. A method for producing a non-oriented electrical steel sheet according to any one of claims 1 to 8, (1) smelting and casting according to any one of the compositions of claims 1 to 4 to form a continuously cast slab; (2) subjecting the continuous cast slab to heating, rough rolling, finish rolling and coiling, in which the thickness of the intermediate slab after rough rolling is 20-45mm, and the thickness of the plate after finish rolling is 1.2-2.0mm, and after coiling, performing aging treatment in the range of 550-650°C for 1-4 hours during the cooling process to form a hot rolled steel coil; (3) pickling the hot-rolled steel coil; (4) forming a steel plate by single-stage cold rolling of the hot-rolled steel coil; (5) continuously annealing the steel sheet; (6) applying an insulating coating to the surface of the steel plate; A manufacturing method comprising the steps of:

10. The continuous annealing in step (5) is carried out at a temperature of 850-1000°C in a mixed atmosphere of nitrogen and hydrogen; The method of claim 9.

11. The method does not include a normalizing intermediate annealing step for the hot rolled steel coil produced in step (2) before step (3). The method according to claim 9 or 10.

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