Preparation method of electrical steel and electrical steel

Abstract

The preparation method comprises the steps that molten steel is subjected to continuous casting through a crystallizer, an electrical steel billet is prepared, the pulling speed of continuous casting is 0.9 m / min to 1.0 m / min, the molten steel sequentially passes through a plurality of fan-shaped sections in the billet pulling direction, first electromagnetic stirring is arranged on the fan-shaped sections, the current intensity of the first electromagnetic stirring is 800 A to 900 A, and the current intensity of the second electromagnetic stirring is 800 A to 900 A; the electromagnetic stirring frequency of the first electromagnetic stirring is 3.0-4.0 Hz; the molten steel comprises the following chemical components in percentage by mass: less than or equal to 0.002% of C, 2.9% < = Si < = 3.0%, 0.1% < = Mn < = 0.3%, 0.05% < = P < = 0.08%, less than or equal to 0.008% of S, 0.2% < = Als < = 0.4%, 0.03% < = Sb < = 0.05%, less than or equal to 0.003% of N, less than or equal to 0.003% of Ti and less than or equal to 0.0025% of O; and the balance of Fe and inevitable impurities. According to the preparation method, by controlling the Si element in molten steel, the continuous casting pulling speed and the first electromagnetic stirring current intensity and frequency, the surface quality of the electrical steel billet is considered on the basis of considering the performance of the electrical steel.

Description

Technical Field

[0001] This application relates to the field of iron and steel smelting technology, specifically to a method for preparing electrical steel and the electrical steel itself. Background Technology

[0002] Electrical steel is a low-carbon silicon steel with a silicon content typically between 0.5% and 3.0%, used in household appliances, power systems, communication systems, and the military industry. As a widely used magnetic material, its performance directly affects the energy efficiency and operational stability of electrical equipment. With changing market demands, higher requirements are being placed on electrical steel in terms of surface quality, thickness uniformity, low iron loss, and high magnetic induction intensity.

[0003] Therefore, it is urgent to improve the performance of electrical steel. Summary of the Invention

[0004] To address the problems existing in the prior art, this application provides a method for preparing electrical steel and electrical steel in general. During the preparation process, the secondary columnar crystals on the inner arc side of the steel billet are reduced, and the surface quality of the electrical steel billet is considered while taking into account the performance of the electrical steel, thereby reducing or eliminating corrugated defects.

[0005] In a first aspect, embodiments of this application provide a method for preparing electrical steel, comprising: The molten steel is continuously cast in a crystallizer to produce electrical steel billets. The casting speed is 0.9 to 1.0 m / min. The molten steel passes through multiple fan-shaped sections along the billet casting direction. A first electromagnetic stirrer is set in the multiple fan-shaped sections. The current intensity of the first electromagnetic stirrer is 800 to 900 A, and the electromagnetic stirring frequency of the first electromagnetic stirrer is 3.0 to 4.0 Hz. The molten steel comprises the following chemical composition by mass percentage: C≤0.002%, 2.9%≤Si≤3.0%, 0.1%≤Mn≤0.3%, 0.05%≤P≤0.08%, S≤0.008%, 0.2%≤Als≤0.4%, 0.03%≤Sb≤0.05%, N≤0.003%, Ti≤0.003%, O≤0.0025%; the balance being Fe and unavoidable impurities.

[0006] The above-mentioned Si content sets the thermodynamic boundary for the evolution of solidification structure; the pulling speed within the above-mentioned range regulates the kinetic path of the solidification process; under the favorable conditions created by the former two, the first electromagnetic stirring within the above-mentioned range is conducive to maximizing the formation of equiaxed crystals, so that solidification proceeds at a certain speed, weakening the conditions for columnar crystal growth; and can effectively reduce the thickness of the secondary columnar crystal layer.

[0007] In summary, this preparation method, by controlling the Si element in the molten steel, the casting speed, and the intensity and frequency of the first electromagnetic stirring current, can balance the performance of electrical steel with the surface quality of the electrical steel billet.

[0008] In some embodiments, the first electromagnetic stirring is a secondary cooling electromagnetic stirring located in sector 0 to sector 5 and a solidification end electromagnetic stirring located in sector 8 to sector 11. In the solidification end electromagnetic stirring, the current intensity is 800~850A and the stirring frequency is 3.0~3.5Hz.

[0009] In some embodiments, along the billet drawing direction, before the molten steel passes through multiple fan-shaped sections, the molten steel passes through a foot roll area, where a crystallizer electromagnetic stirrer is installed. The current intensity of the crystallizer electromagnetic stirrer is 300~400A, and the stirring frequency is 4.0~6.0Hz.

[0010] In some embodiments, the continuous casting method further includes: cooling the secondary cooling zone and controlling the specific water content in the secondary cooling zone to be 0.5~0.7L / kg.

[0011] In some embodiments, cooling the secondary cooling zone includes: The cooling water pressure used in the foot roller area and the 0# to 3# sector sections at the crystallizer outlet is 6.0 to 7.5 bar, and the cooling water flow rate is 500 to 750 L / min. The cooling water pressure used in the area from sector 4 to sector 10 is 1.0 to 2.5 bar, and the cooling water flow rate is 60 to 160 L / min. The cooling water pressure used in sector sections 11 to 16 is 0.4 to 0.6 bar, and the cooling water flow rate is 20 to 40 L / min.

[0012] In some embodiments, a mist cooling method is used in at least a portion of the sector segment, in which cooling water is mixed with compressed gas and sprayed onto the surface of the billet, wherein the gas pressure is controlled to be 1.9 to 2.1 bar.

[0013] In some embodiments, in the aerosol cooling method, the inlet pressure of the gas main pipe is controlled to be 5.0 to 6.0 bar, and the total gas flow rate is controlled to be 7000 to 9000 L / min.

[0014] In some embodiments, the continuous casting includes cooling, wherein the cooling circuits are symmetrically arranged in the direction of the wide face and the narrow face of the billet; and in the positions of sector 0 to sector 4, the cooling water pressure and flow rate of the wide face of the billet in the same sector are made to be greater than the cooling water pressure and flow rate of the narrow face of the billet.

[0015] In some embodiments, the electrical steel billet comprises the following chemical composition by mass percentage: C: 0.0018%~0.0035%; Si: 2.9%~3.2%; Mn: 0.24%~0.28%; 0.05%≤P≤0.08%; Al: 0.25%~0.60%; 0.03%≤Sb≤0.05%; S≤0.004%; O≤0.0025%; N≤0.003%; Ti≤0.003%; with the balance being Fe and unavoidable impurities.

[0016] Secondly, embodiments of this application provide an electrical steel, which is prepared according to the preparation method of the first aspect of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the continuous casting process structure for electrical steel provided in Embodiment 1 of this application.

[0019] Figure 2 This is a cross-sectional schematic diagram of the electrical steel in the thickness direction of the embodiments and comparative examples of this application.

[0020] Figure 3 This is a photograph of the appearance of the electrical steel provided in Embodiment 1 of this application.

[0021] Figure 4 This is a photograph of the appearance of the electrical steel provided in Comparative Example 1 of this application.

[0022] Explanation of the symbols in the attached drawings: 1. Foot roller area; 2. 0# sector section; 3. 3# sector section; 4. 4# sector section; 5. 5# sector section; 6. 10# sector section; 7. 11# sector section; 8. 16# sector section. Detailed Implementation

[0023] The features and exemplary embodiments of various aspects of this application will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a comprehensive understanding of this application. However, it will be apparent to those skilled in the art that this application can be implemented without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of this application by illustrating examples. In the accompanying drawings and the following description, at least some well-known structures and techniques are not shown to avoid unnecessarily obscuring the application; and, for clarity, the dimensions of some structures may be exaggerated. Furthermore, the features, structures, or characteristics described below can be combined in any suitable manner in one or more embodiments.

[0024] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0025] In the entire manufacturing process of electrical steel, continuous casting is a crucial step that determines the internal microstructure of the billet. The solidification structure of the billet generally includes columnar crystals and equiaxed crystals, with columnar crystals exhibiting obvious directionality and coarse grain characteristics. An excessively high proportion of columnar crystals in the billet, especially with a thick secondary columnar crystal layer, makes it difficult to fully break down during subsequent hot rolling. This hinders effective promotion during cold rolling and annealing, and instead easily leads to a significant texture gradient along the thickness direction. This microstructure inhomogeneity manifests as a periodically undulating "corrugated" surface defect along the rolling direction after cold rolling, severely affecting the product's appearance and flatness, and also causing performance defects such as magnetic degradation.

[0026] Studies have found that by adjusting continuous casting process parameters (such as casting speed and cooling intensity) to control the solidification structure, without the application of electromagnetic stirring, the columnar crystal ratio of the cast billet is usually maintained at 50%–80%, while the equiaxed crystal ratio can only reach 20%–50%. During subsequent lamination or pre-stretching processes, the material macroscopically wrinkles due to inconsistent flow behavior, ultimately inducing corrugated defects.

[0027] Further research revealed that by employing appropriate electromagnetic stirring, optimizing the secondary cooling process, and adding microalloying elements to improve the solidification structure, the proportion of equiaxed crystals can be effectively increased and the growth of columnar crystals can be stably controlled. This can improve the equiaxed crystal ratio of the billet, inhibit the formation of secondary columnar crystal layers, and reduce the thickness of secondary columnar crystal layers in electrical steel. As a result, the problem of corrugated defects on the surface of cold-rolled steel can be fundamentally solved, and the overall performance and surface quality of non-electrical steel can be improved.

[0028] To address the problems in the prior art, this application provides a method for preparing electrical steel and an electrical steel thereof.

[0029] In a first aspect, embodiments of this application provide a method for preparing electrical steel, comprising: The molten steel is continuously cast in a crystallizer to produce electrical steel billets. The casting speed is 0.9 to 1.0 m / min. The molten steel passes through multiple fan-shaped sections along the billet casting direction. A first electromagnetic stirrer is set in the multiple fan-shaped sections. The current intensity of the first electromagnetic stirrer is 800 to 900 A, and the electromagnetic stirrer frequency in the fan-shaped section is 3.0 to 4.0 Hz. The molten steel comprises the following chemical composition by mass percentage: C≤0.002%, 2.9%≤Si≤3.0%, 0.1%≤Mn≤0.3%, 0.05%≤P≤0.08%, S≤0.008%, 0.2%≤Als≤0.4%, 0.03%≤Sb≤0.05%, N≤0.003%, Ti≤0.003%, O≤0.0025%; the balance being Fe and unavoidable impurities.

[0030] Si (Si) in molten steel and its content are key elements and contents for expanding the γ-phase region and increasing the distance between the liquidus and solidus lines. When the Si content is within the above range, the solidification two-phase region is significantly widened, and the compositional supercooling at the dendrite growth front increases, which is conducive to equiaxed crystal nucleation. This silicon content provides physical space for subsequent electromagnetic stirring to break up dendrites and promote the dispersed distribution of crystal nuclei. At the same time, the thermal conductivity of high-Si steel is reduced, which naturally slows down the advancement speed of the solidification front and weakens the driving force for the directional growth of columnar crystals.

[0031] The casting speed directly determines the thickness of the solidified shell, the length of the liquid core, and the residence time in the high-temperature zone per unit time. The aforementioned Si content causes the molten steel to solidify slowly. If the casting speed is too high, it will result in an excessively thin shell and an increased risk of bulging. However, if the casting speed is too low, production efficiency will decrease and may exacerbate center segregation. Therefore, it is necessary to match the appropriate casting speed according to the Si content, taking into account both production efficiency and billet quality.

[0032] The current intensity and frequency of the first electromagnetic stirring are important means of actively intervening in the solidification structure. Forced convection is generated in the solidification two-phase region by alternating magnetic field: appropriate current intensity enhances stirring force, effectively breaks up primary dendrites, and provides a large number of free crystal nuclei; appropriate frequency ensures that the stirring penetration depth covers the entire solidification two-phase region, avoiding only surface stirring of molten steel without stirring of the internal molten steel; stirring promotes composition homogenization, inhibits solute enrichment, and further weakens the conditions for columnar crystal growth.

[0033] In summary, this preparation method, by controlling the Si element in the molten steel, the casting speed, and the intensity and frequency of the first electromagnetic stirring current, can balance the performance of electrical steel with the surface quality of the electrical steel billet.

[0034] If the frequency of the first electromagnetic stirring is too high, the stirring eddy will become shallow, and the central equiaxed crystals will not be able to form. If there is no suitable silicon content to match the appropriate stretching and provide a sufficient solidification two-phase region, even a higher first electromagnetic stirring will only disturb the already solidified region and have little effect.

[0035] Conversely, if there is only strong stirring and the casting speed is too high, the crystal nuclei generated by stirring will be rapidly solidified and "frozen" before they can grow, and the equiaxed crystal ratio of the continuously cast billet will still be low.

[0036] In summary, the Si content sets the thermodynamic boundary for the evolution of solidification structure; the pulling speed regulates the kinetic path of the solidification process; and the first electromagnetic stirring parameter provides an active intervention method to maximize the formation of equiaxed crystals under the favorable conditions created by the former two, so that solidification can proceed at a certain speed and weaken the conditions for columnar crystal growth; and can effectively reduce the thickness of the secondary columnar crystal layer.

[0037] Therefore, the reduction in the thickness of the secondary columnar crystal layer significantly improves the uniformity and isotropy of the billet structure, making the material deformation during cold rolling more coordinated, reducing local strain concentration and periodic distribution of residual stress, fundamentally reducing the probability of corrugated defects on the surface of cold-rolled sheet, taking into account both the performance of electrical steel and the surface quality of electrical steel billet, reducing downgrading and increasing yield.

[0038] In some embodiments, the first electromagnetic stirring is a secondary cooling electromagnetic stirring located in sector 0 to sector 5 and a solidification end electromagnetic stirring located in sector 8 to sector 11. In the solidification end electromagnetic stirring, the current intensity is 800~850A and the stirring frequency is 3.0~3.5Hz.

[0039] The first electromagnetic stirrer set at this location can further and effectively break up the primary dendrites, provide a large number of free crystal nuclei, promote composition homogenization, inhibit solute enrichment, and further weaken the growth conditions of columnar crystals.

[0040] Setting the current intensity to 800~850A in the foot roller area may affect the quality of the initially formed billet shell.

[0041] If it is not set in sector segment 8 to 11, but in any position in sector segment 13 to 16, it may affect the surface quality of the cast billet.

[0042] Figure 1 This is a schematic diagram of the process structure of the continuous casting position of electrical steel provided in Embodiment 1 of this application. As can be seen from the figure, after passing through the crystallizer, the molten steel passes sequentially through foot roll area 1, sector 2 (0#), sector 3 (3#), sector 4 (4#), sector 5 (5#), etc., then flows through sector 6 (10#), sector 7 (11#), and finally through sector 8 (16#), solidifying into a casting billet.

[0043] In some embodiments, before the molten steel passes through multiple fan-shaped sections along the billet drawing direction, it passes through a foot roll area. An electromagnetic stirrer is installed in the foot roll area, and the current intensity of the electromagnetic stirrer is 300-400A, with a stirring frequency of 4.0-6.0Hz. This ensures that the molten steel initially solidifies into a billet shell, while further electromagnetic stirring promotes compositional homogenization, inhibits solute enrichment, and further weakens the conditions for columnar crystal growth.

[0044] If the current intensity or frequency of the electromagnetic stirring in the crystallizer exceeds the above range, it will affect the initial solidification of the molten steel into a billet shell, affect the formation of equiaxed crystals and the ratio of columnar crystals on the surface, and also reduce the quality of the cast billet.

[0045] In some embodiments, electromagnetic stirring rollers are provided in the fan-shaped section, with a distribution spacing of 2-6m. This facilitates stirring of the molten steel at regular intervals during the preparation process. The electromagnetic stirring promotes homogenization of the composition in the molten steel, inhibits solute enrichment, and further weakens the conditions for columnar crystal growth.

[0046] In addition, the casting speed, casting temperature, and secondary cooling water ratio also affect the temperature gradient at the solidification interface, the solidification rate, and the stability of the molten steel-billet shell interface.

[0047] In some embodiments, the continuous casting method further includes: cooling the secondary cooling zone, and controlling the specific water content of the secondary cooling zone to be 0.5~0.7L / kg, optionally 0.62~0.65L / kg, optionally 0.66~0.68L / kg.

[0048] During continuous casting, the cooling intensity affects the grain size and structure of the solidified structure of the continuously cast billet. As the cooling intensity decreases, the thickness of the billet shell decreases, which causes heat to dissipate more quickly through the shell. This allows the billet to form more nucleation sites, which in turn leads to a certain degree of reduction in the grain size and an increase in the number of grains. This refines the grain size of the solidified structure of the continuously cast billet and improves the surface quality of the billet.

[0049] Meanwhile, if the water content in the secondary cooling zone is within the above range, excessive cooling can prevent columnar crystals from continuing to extend rapidly along a single orientation in the secondary cooling zone, thereby effectively reducing the thickness of the secondary columnar crystal layer.

[0050] In some embodiments, the cooling water pressure and flow rate of each cooling zone are independently controlled so that the cooling intensity decreases along the pulling direction.

[0051] In some embodiments, cooling the secondary cooling zone includes: using a cooling water pressure of 6.0 to 7.5 bar and a cooling water flow rate of 500 to 750 L / min in the foot roller area and the 0# to 3# sector sections at the crystallizer outlet; The cooling water pressure used in the area from sector 4 to sector 10 is 1.0 to 2.5 bar, and the cooling water flow rate is 60 to 160 L / min. The cooling water pressure used in sector sections 11 to 16 is 0.4 to 0.6 bar, and the cooling water flow rate is 20 to 40 L / min.

[0052] Therefore, using different cooling water pressures and flow rates for each section helps to ensure uniform cooling while also balancing the stress on the arc surface of the fan-shaped section and the surface of the billet shell, which is beneficial to further improving the surface quality of the cast billet.

[0053] In some embodiments, air mist cooling is employed in at least a portion of the sector segment, where cooling water is mixed with compressed gas and sprayed onto the surface of the billet, wherein the gas pressure is controlled at 1.9–2.1 bar. This approach achieves both effective cooling and reduced stress on the billet shell surface, as well as balanced force application, which is beneficial for further improving the surface quality of the billet.

[0054] In some embodiments, in the aerosol cooling method, the inlet pressure of the main gas pipe is controlled at 5.0–6.0 bar, and the total gas flow rate is controlled at 7000–9000 L / min. This helps to balance the water and air in the secondary cooling zone.

[0055] In order to control the inlet pressure of the main gas pipe and the total gas flow rate, each gas mist cooling zone controls the gas flow rate by adjusting the opening of the corresponding valve. The valve opening of the cooling zone is 20% to 65%.

[0056] In some embodiments, the continuous casting includes cooling, wherein the cooling circuits are symmetrically arranged in the direction of the wide and narrow faces of the billet; in the 0# to 4# sector segments, the cooling water pressure and flow rate of the wide face of the billet in the same sector segment are respectively greater than those of the narrow face of the billet. This facilitates a balanced cooling rate between the wide and narrow faces of the billet, resulting in uniform cooling and shrinkage of the billet, which is beneficial for improving the shape and cooling quality of the billet.

[0057] In some embodiments, the pouring temperature in continuous casting is 15640~1595℃, and the continuous casting time is 30~50min. This can improve production efficiency and suppress coarse microstructure.

[0058] In some embodiments, the electrical steel billet comprises the following chemical composition by mass percentage: C: 0.0018%~0.0035%; Si: 2.9%~3.2%; Mn: 0.24%~0.28%; 0.05%≤P≤0.08%; Al: 0.25%~0.60%; 0.03%≤Sb≤0.05%; S≤0.004%; O≤0.0025%; N≤0.003%; Ti≤0.003%; with the balance being Fe and unavoidable impurities.

[0059] In some embodiments, the preparation method of electrical steel involves blast furnace molten iron, KR desulfurization station, BOF converter, and RH vacuum degassing.

[0060] In some embodiments, before continuously casting the molten steel using a crystallizer, the method for preparing electrical steel further includes: smelting molten iron using a blast furnace, KR desulfurization, BOF converter, and RH vacuum degassing.

[0061] In addition, during continuous casting, the superheat of the molten steel can be controlled at 10-25℃, the liquid level fluctuation range of the molten steel in the crystallizer is ±10mm, and the stopper rod position is 30-55mm.

[0062] In some embodiments, after continuously casting molten steel using a crystallizer, the method for preparing electrical steel further includes: The electrical steel billet undergoes hot rolling, including billet heating, descaling, rough rolling, finish rolling, coiling, and stacking cooling. This is followed by cold rolling, including uncoiling, welding, pickling, rolling, coiling, annealing, recoiling, and packaging into finished electrical steel products.

[0063] Secondly, embodiments of this application provide an electrical steel, which is prepared according to the preparation method of the first aspect of this application.

[0064] Example The following specific embodiments illustrate this application. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0065] Example 1 Methods for preparing electrical steel include: The molten steel is continuously cast in a crystallizer to produce an electrical steel billet. The molten steel has the following chemical composition by mass percentage: C≤0.002%, 2.9%≤Si≤3.0%, 0.1%≤Mn≤0.3%, 0.05%≤P≤0.08%, S≤0.008%, 0.2%≤Als≤0.4%, 0.03%≤Sb≤0.05%, N≤0.003%, Ti≤0.003%, O≤0.0025%; the balance is Fe and unavoidable impurities. The continuous casting speed is 0.9~1.0m / min. Along the billet casting direction, the molten steel passes sequentially through the foot roll area and multiple fan-shaped sections. A first electromagnetic stirrer is set in the multiple fan-shaped sections. The current intensity of the first electromagnetic stirrer is 800~900A, and the electromagnetic stirring frequency of the first electromagnetic stirrer is 3.0~4.0Hz. The first electromagnetic stirrer is a secondary cooling electromagnetic stirrer located in sector 0 to sector 5, and a solidification end electromagnetic stirrer located in sector 8 to sector 11. A crystallizer electromagnetic stirrer is provided in the foot roller area, and the current intensity of the crystallizer electromagnetic stirrer is 300~400A, and the stirring frequency is 4.0~6.0Hz.

[0066] Cooling the secondary cooling zone includes: The cooling water pressure used in the foot roller area and the 0# to 3# sector sections at the crystallizer outlet is 6.0 to 7.5 bar, and the cooling water flow rate is 500 to 750 L / min. The cooling water pressure used in the area from sector 4 to sector 10 is 1.0 to 2.5 bar, and the cooling water flow rate is 60 to 160 L / min. The cooling water pressure used in sector sections 11 to 16 is 0.4 to 0.6 bar, and the cooling water flow rate is 20 to 40 L / min.

[0067] In the sector segment, an aerosol cooling method is used, where cooling water is mixed with compressed gas and sprayed onto the surface of the billet. The gas pressure is controlled at 1.9–2.1 bar. In this aerosol cooling method, the inlet pressure of the main gas pipe is controlled at 5.0–6.0 bar, and the total gas flow rate is controlled at 7000–9000 L / min. A symmetrically arranged cooling circuit is used along the wide and narrow sides of the billet. From sector segment #0 to sector segment #4, the cooling water pressure and flow rate on the wide side of the billet in the same sector segment are respectively greater than those on the narrow side.

[0068] The electrical steel billet comprises the following chemical composition by mass percentage: C: 0.0018%~0.0035%; Si: 2.9%~3.2%; Mn: 0.24%~0.28%; 0.05%≤P≤0.08%; Al: 0.25%~0.60%; 0.03%≤Sb≤0.05%; S≤0.004%; O≤0.0025%; N≤0.003%; Ti≤0.003%; with the balance being Fe and unavoidable impurities.

[0069] The chemical composition of the molten steel in Examples 1-3 is shown in Table 1, wherein N ≤ 0.003%, Ti ≤ 0.003%, and the balance is Fe and unavoidable impurities. The stretching, electromagnetic stirring, and secondary cooling control in the continuous casting process are shown in Table 2.

[0070] The chemical composition of the molten steel in Comparative Examples 1 and 2 is shown in Table 1, with N ≤ 0.003%, Ti ≤ 0.003%, and the balance being Fe and unavoidable impurities. The stretching, electromagnetic stirring, and secondary cooling control in the continuous casting process were consistent with those in Example 1.

[0071] Table 1

[0072] Examples 4-9 The difference from Example 1 lies in the process of continuous casting, as shown in Tables 2 and 3.

[0073] Comparative Examples 3-7 The difference from Example 1 lies in the process of continuous casting, as shown in Tables 2 and 3.

[0074] Table 2

[0075] Table 3

[0076] Test section The samples in the examples and comparative examples were subjected to performance testing.

[0077] 1) Metallographic structure inspection and sampling: Select a cross-section that represents the typical quality condition of the billet in the furnace, casting, or section and cut a sample using flame cutting. The sample size is 90-120 mm in length, and the width and thickness are the corresponding continuous casting billet specifications.

[0078] Grinding: Using a planer, milling machine, or grinding wheel, remove the heat-affected zone and oxide layer generated by flame cutting. Obtain a scratch-free, smooth, and clean mirror or matte finish.

[0079] Corrosion: A solution of 200g ferric chloride (FeCl3), 300mL hydrochloric acid (HCl), and 1000mL water (H2O) was used for corrosion at a time of 8–12 min. The test results are shown in Table 4. The low-magnification solidification microstructure was rated according to GB / T 1979 "Rating Chart of Low-Magnification Microstructure Defects in Structural Steel".

[0080] like Figure 2 As shown, a 30mm thickness is removed from the surface of a 230mm thick electrical steel, i.e., a 30mm thickness is removed from the surface of the electrical steel of thickness A. This 30mm thickness typically consists of columnar grains, resulting in electrical steel of thickness a. Electrical steel of thickness a typically consists mainly of equiaxed grains. When the columnar grains exceed a certain range, it affects the surface quality of the electrical steel. The equiaxed grain ratio can be calculated for the obtained electrical steel of thickness a.

[0081] It is understandable that A - 60mm = a, and the range of A can be 200~400mm.

[0082] The equiaxed crystal ratio in electrical steel of thickness α = (1 - volume fraction of columnar crystals) / 1.

[0083] 2) Surface morphology: Observe the surface condition of the electrical steel obtained in each embodiment and comparative example, and check for defects such as corrugated stripes. Through comparison... Figure 3 and Figure 4 It can be seen that the electrical steel obtained in this embodiment has significantly improved surface defects, eliminating the presence or absence of obvious corrugated defects. This can also be verified using a surface quality testing instrument.

[0084] 3) Original pass rate of electrical steel billets: Measured by a surface quality inspector. Within the statistical period, the percentage of billets that directly meet quality standards and are delivered to the next process (such as steel rolling) without any scrapping, re-judgment, or rework, out of the total weight of all continuously cast billets produced in that period. The calculation formula is: .

[0085] Table 4

[0086] Combining the data in Table 4 and Figures 1-3 As can be seen, the columnar crystal content in the metallographic structure of the electrical steel in this embodiment is significantly reduced; the metallographic image shows no obvious columnar crystals. When the equiaxed crystal ratio in electrical steel of thickness 'a' is ≥70%, the columnar crystal content is low, resulting in no corrugated defects on the surface of the electrical steel. However, when the equiaxed crystal ratio in electrical steel of thickness 'a' is ≥70%, the columnar crystal content is relatively high, leading to corrugated defects on the surface of the electrical steel.

[0087] Figure 3 This is a photograph of the appearance of the electrical steel provided in Embodiment 1 of this application. Figure 4 This is a photograph of the appearance of the electrical steel provided in Comparative Example 1 of this application. Compared to Figure 3 and Figure 4 The billet of electrical steel provided in this embodiment has no obvious columnar crystals, so that the surface of electrical steel is free of corrugated defects.

[0088] 3) Performance Testing The electrical steel samples from the examples and comparative examples were subjected to performance testing. Mechanical property testing of the electrical steel: According to GB / T228.1-2021 "Metallic materials – Tensile testing – Part 1: Tests at room temperature", an electronic universal testing machine was used to process the non-oriented electrical steel into standard tensile specimens. The tensile speed was controlled between 0.00025 / s and 0.0025 / s. Force and displacement data were recorded during the tensile process, and the tensile strength and yield strength were calculated.

[0089] Iron loss and magnetic property testing of electrical steel: Following GB / T 3655-2019 "Method for Measurement of Magnetic Properties of Electrical Steel Sheets (Strips)," the power loss per unit weight of non-oriented electrical steel is measured using an Epstein square ring apparatus or a single-piece tester under a magnetic field strength of 1.5T and a frequency of 50Hz. This power loss is defined as the iron loss. The magnetic induction intensity of the non-oriented electrical steel at a magnetic field strength of 1.5T is measured and recorded as B50.

[0090] The results are shown in Table 5.

[0091] Table 5

[0092] Based on the data in Table 5, compared with the comparative example, the electrical steel obtained in this application embodiment has better mechanical properties.

[0093] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing electrical steel, characterized in that, include: The molten steel is continuously cast in a crystallizer to produce an electrical steel billet. The casting speed is 0.9 to 1.0 m / min. The molten steel passes through multiple fan-shaped sections in sequence along the billet casting direction. A first electromagnetic stirrer is set in the multiple fan-shaped sections. The current intensity of the first electromagnetic stirrer is 800 to 900 A, and the electromagnetic stirring frequency of the first electromagnetic stirrer is 3.0 to 4.0 Hz. The molten steel comprises the following chemical composition by mass percentage: C≤0.002%, 2.9%≤Si≤3.0%, 0.1%≤Mn≤0.3%, 0.05%≤P≤0.08%, S≤0.008%, 0.2%≤Als≤0.4%, 0.03%≤Sb≤0.05%, N≤0.003%, Ti≤0.003%, O≤0.0025%; the balance being Fe and unavoidable impurities.

2. The method for preparing electrical steel according to claim 1, characterized in that, The first electromagnetic stirring is the secondary cooling electromagnetic stirring located in sector 0 to sector 5 and the solidification end electromagnetic stirring located in sector 8 to sector 11. In the solidification end electromagnetic stirring, the current intensity is 800~850A and the stirring frequency is 3.0~3.5Hz.

3. The method for preparing electrical steel according to claim 2, characterized in that, Along the billet drawing direction, before the molten steel passes through multiple fan-shaped sections, the molten steel passes through the foot roll area, where a crystallizer electromagnetic stirrer is installed. The current intensity of the crystallizer electromagnetic stirrer is 300~400A, and the stirring frequency is 4.0~6.0Hz.

4. The method for preparing electrical steel according to claim 1, characterized in that, In the continuous casting process, the method further includes: cooling the secondary cooling zone and controlling the water content in the secondary cooling zone to be 0.5~0.7L / kg.

5. The method for preparing electrical steel according to claim 4, characterized in that, The cooling of the secondary cooling zone includes: The cooling water pressure used in the foot roller area and the 0# to 3# sector sections at the crystallizer outlet is 6.0 to 7.5 bar, and the cooling water flow rate is 500 to 750 L / min. The cooling water pressure used in the area from sector 4 to sector 10 is 1.0 to 2.5 bar, and the cooling water flow rate is 60 to 160 L / min. The cooling water pressure used in sector sections 11 to 16 is 0.4 to 0.6 bar, and the cooling water flow rate is 20 to 40 L / min.

6. The method for preparing electrical steel according to claim 1, characterized in that, In at least some of the sector sections, an air mist cooling method is used, in which cooling water is mixed with compressed gas and sprayed onto the surface of the billet, wherein the gas pressure is controlled at 1.9 to 2.1 bar.

7. The method for preparing electrical steel according to claim 6, characterized in that, In the aforementioned aerosol cooling method, the inlet pressure of the main gas pipe is controlled at 5.0–6.0 bar, and the total gas flow rate is controlled at 7000–9000 L / min.

8. The method for preparing electrical steel according to claim 1, characterized in that, The continuous casting includes cooling, and the cooling circuits are symmetrically arranged in the direction of the wide side and the narrow side of the billet; in the positions from the 0# sector segment to the 4# sector segment, the cooling water pressure and flow rate of the wide side of the billet in the same sector segment are respectively greater than the cooling water pressure and flow rate of the narrow side of the billet.

9. The method for preparing electrical steel according to claim 1, characterized in that, The electrical steel billet comprises the following chemical composition by mass percentage: C: 0.0018%~0.0035%; Si: 2.9%~3.2%; Mn: 0.24%~0.28%; 0.05%≤P≤0.08%; Al: 0.25%~0.60%; 0.03%≤Sb≤0.05%; S≤0.004%; O≤0.0025%; N≤0.003%; Ti≤0.003%; with the balance being Fe and unavoidable impurities.

10. An electrical steel, characterized in that, The electrical steel is prepared by the method described in any one of claims 1 to 9, and the electrical steel has the following properties: iron loss P1.0 / 400 is 11~14W / kg, magnetic induction B5000≥1.695T, yield strength RP0.2 is 420~480MPa, tensile strength Rm is 530~600MPa, and elongation A50 is 16%~22%.

Images