Electrical steel and method of manufacturing the same

Abstract

The application discloses an electrical steel and a manufacturing method thereof. The manufacturing method of the electrical steel comprises the following steps: steelmaking, thin slab continuous casting and rolling, heating and rolling, pickling and cold rolling, and annealing and plating. In the steelmaking, the molten iron is pretreated, converter smelting and refining are performed to obtain refined molten steel. In the thin slab continuous casting and rolling, the refined molten steel is poured into a tundish and continuously cast to obtain a continuously cast slab, and the thickness H of the continuously cast slab is 40mm-60mm. In the heating and rolling, the continuously cast slab is sent into a heating furnace for heating, and after being discharged from the furnace, the continuously cast slab is subjected to multi-pass rolling. In the multi-pass rolling, the reduction of the first pass is 55%<=η1<=65%, the reduction of the second pass is 45%<=η2<=55%, and the reductions of the third pass and subsequent passes are controlled to be 20%-40%. After the rolling is completed, the hot-rolled steel coil is obtained through coiling. The technical scheme of the application can solve the problem that in the existing thin slab continuous casting and rolling process, the internal deformation of the continuously cast slab is insufficient, the microstructure of the hot-rolled plate is non-uniform, and the magnetic properties and iron loss of the electrical steel are affected.

Description

Technical Field

[0001] This application relates to the field of iron and steel smelting, and in particular to an electrical steel and a method for manufacturing the same. Background Technology

[0002] Electrical steel, also known as silicon steel sheet, is an indispensable soft magnetic alloy material in the power, electronics, and military industries. It is primarily used to manufacture the cores of various transformers, motors, and generators. Because electrical steel operates under alternating magnetic fields, its magnetic properties directly determine the energy conversion efficiency and energy consumption level of electrical equipment. Ideal electrical steel materials typically contain 0.5% to 4.5% silicon. The addition of silicon significantly increases the resistivity and maximum permeability of iron, thereby reducing coercivity and core losses.

[0003] Currently, the production of high-performance electrical steel typically employs thin slab continuous casting and rolling or traditional hot continuous rolling processes. A typical process includes steelmaking, continuous casting, slab heating, roughing, finishing, coiling, pickling, cold rolling, and final annealing and coating. In the hot rolling stage, to obtain a uniform microstructure and ideal texture, the slab is usually heated to a high temperature and rolled with a large reduction. However, existing manufacturing processes still have certain shortcomings. Therefore, improvements to the aforementioned processes are necessary. Summary of the Invention

[0004] In view of the above problems, this application provides an electrical steel and its manufacturing method, which can solve the problem that insufficient internal deformation penetration of the continuously cast billet in the existing thin slab continuous casting and rolling process leads to uneven microstructure of the hot-rolled plate, thereby affecting the magnetic properties and iron loss of the electrical steel.

[0005] In one aspect, this application provides a method for manufacturing electrical steel, including steelmaking, thin slab continuous casting and rolling, heating and rolling, pickling and cold rolling, and annealing and coating. Steelmaking: Molten iron is pretreated, smelted in a converter, and refined to obtain refined molten steel. Thin slab continuous casting and rolling: Refined molten steel is poured into a ladle and continuously cast to obtain a continuously cast billet with a thickness H of 40mm~60mm. Heating and rolling: The continuously cast billet is heated in a heating furnace and then rolled in multiple passes. In the multi-pass rolling, the reduction rate of the first pass is 55%≤η1≤65%, the reduction rate of the second pass is 45%≤η2≤55%, and the reduction rate of the third and subsequent passes is controlled at 20%~40%. After rolling, the billet is coiled to obtain a hot-rolled steel coil. Pickling and cold rolling: The hot-rolled steel coil is pickled and then cold-rolled to obtain a cold-rolled steel coil. Annealing and Coating: Cold-rolled steel coils are annealed, coated, and cooled to obtain electrical steel. Electrical steel comprises the following chemical composition by mass percentage: C≤0.0035%, 0.95%≤Si≤1.10%, 0.75%≤Mn≤0.90%, P≤0.040%, S≤0.0050%, 0.35%≤Al≤0.55%, with the remainder being iron and unavoidable trace elements.

[0006] In some embodiments, in the thin slab continuous casting and rolling step, the thickness H of the continuously cast slab is 55mm~60mm.

[0007] In some embodiments, during the heating and rolling steps, the reduction rate of the first rolling pass is 50%≤η1≤55%, and the reduction rate of the second rolling pass is 50%≤η2≤52%.

[0008] In some embodiments, during the converter smelting process, the carbon content at the tapping endpoint of the converter smelting is controlled to be 0.025% to 0.060%, and the converter endpoint temperature is 1655°C to 1695°C.

[0009] In some embodiments, refining includes RH refining treatment; after RH refining treatment, the sulfur (S) content of the refined molten steel is controlled to be ≤0.0015%, and the temperature of the refined molten steel is ≥1250°C.

[0010] In some embodiments, the RH refining process includes vacuum decarburization, deoxidation and alloying, and a circulating purification process. The vacuum decarburization process includes a pure vacuum circulation, with a circulation time of 4 to 8 minutes; the circulating purification process takes 6 to 10 minutes.

[0011] In some embodiments, during the continuous casting process, the superheat of the tundish is controlled at 15°C to 30°C, a high-silica insulating covering agent and a special protective slag for electrical steel are used in the tundish, and the billet casting speed is controlled at 4.5 m / min to 5.0 m / min.

[0012] In some embodiments, during the heating and rolling steps, the heating temperature of the billet is controlled to be 1100℃~1160℃, the furnace exit temperature is controlled to be 1020℃~1080℃, and the final rolling temperature is controlled to be 870℃~930℃.

[0013] In some embodiments, during the heating and rolling steps, the coiling temperature is controlled at 700°C to 740°C.

[0014] In some embodiments, during the pickling and cold rolling step, the cold rolling elongation is controlled at 2.5% to 3.0%, and the cold rolling relative reduction is controlled at 75% to 85%.

[0015] In some embodiments, during the annealing and coating steps, the annealing temperature is controlled at 900℃~930℃, the holding time is 1min~2min, and the unit operating speed is 120m / min~150m / min.

[0016] Secondly, this application also provides an electrical steel comprising the following chemical composition by mass percentage: C≤0.0035%, 0.95%≤Si≤1.10%, 0.75%≤Mn≤0.90%, P≤0.040%, S≤0.0050%, 0.35%≤Al≤0.55%, with the remainder being iron and unavoidable trace elements.

[0017] The electrical steel and its manufacturing method provided in this application, through the scientific allocation of the reduction rate in multiple rolling passes, particularly by setting the first pass reduction rate to a large deformation of 55%~65%, can generate strong deformation penetration force, effectively breaking the coarse columnar crystals in the continuously cast billet and deeply welding the porosity and microcracks in the center of the billet, significantly improving the internal density of the material. The second pass maintains a relatively high reduction rate of 45%~55%, further homogenizing the deformation in the thickness direction of the slab. Controlling the reduction rate of the third and subsequent passes at 20%~40% avoids edge cracking or poor plate shape caused by excessive cumulative deformation resistance. This "large at the beginning and small at the end, gradient reduction" reduction system ensures the uniformity of the microstructure across the entire thickness range of the hot-rolled plate. The uniform and dense microstructure of the hot-rolled plate lays a solid foundation for the nucleation and growth of favorable textures (such as the {100} texture in non-oriented silicon steel) in subsequent cold rolling and annealing processes. By combining the specific chemical composition design of this application (such as a reasonable Si, Al, Mn ratio to improve resistivity and suppress harmful texture), the final electrical steel produced can effectively reduce hysteresis loss and eddy current loss, thereby significantly reducing the iron loss of the finished product (P1.5 / 50), while obtaining a high magnetic induction intensity (B50), meeting the stringent requirements of high-efficiency and energy-saving motors for the magnetic properties of materials. This solution is tailored to the characteristics of thin slabs with a thickness of 40mm~60mm, and a matching hot rolling deformation regime is designed. This not only overcomes the problems of large rolling load fluctuations and high equipment wear caused by improper reduction distribution in traditional processes, but also fully utilizes the advantages of short continuous casting and rolling processes and fast solidification and cooling rates for thin slabs (which are beneficial for suppressing the precipitation of harmful second phases). While ensuring high product performance, it effectively improves production speed and yield, and reduces manufacturing costs.

[0018] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0019] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings, in which the same or similar reference numerals denote the same or similar features, and the drawings are not drawn to scale.

[0020] Figure 1 This is a schematic diagram of the thin slab continuous casting and rolling process according to an embodiment of this application; Figure 2 This is a schematic diagram of the pickling and cold continuous rolling process according to an embodiment of this application; Figure 3 This is a schematic diagram of a continuous annealing coating process according to an embodiment of this application; Figure 4 The image shows a metallographic photograph of the microstructure of the hot-rolled coil in Comparative Example 1. Figure 5 This is a radial metallographic photograph of the microstructure of the hot-rolled coil in Example 1. Detailed Implementation

[0021] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0022] 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. 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.

[0023] It should be understood that when describing the structure of a component, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above the other layer or region, or that it contains other layers or regions between it and the other layer or region. Furthermore, if the component is flipped over, that layer or region will be located "below" or "under" the other layer or region.

[0024] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. Furthermore, the features, structures, or characteristics described below may be combined in any suitable manner in one or more embodiments.

[0025] Currently, the industrial production of 50W800H non-oriented electrical steel mainly adopts a long-process technology involving steelmaking, continuous casting, hot rolling, pickling, cold rolling, and annealing coating. Among these, continuous casting (especially thin slab continuous casting and rolling technology) has become the mainstream choice for producing high-quality electrical steel due to its advantages such as short process, low energy consumption, fast solidification and cooling speed, and effective suppression of coarse inclusion precipitation. However, significant technical defects still exist in the existing continuous casting and subsequent hot rolling processes. Especially in the hot rolling roughing stage, the traditional multi-pass rolling reduction ratio distribution often lacks targeted optimization. If the reduction ratio distribution in the first few passes is unreasonable or the deformation penetration is insufficient, it is difficult to effectively break the coarse columnar crystals in the center of the continuously cast billet, resulting in the inability to completely weld the porosity and microcracks inside the billet. This internal structural defect will be inherited by the subsequent cold rolling and annealing processes, seriously hindering the nucleation and growth of favorable textures, ultimately leading to high iron loss and insufficient magnetic induction intensity in the finished electrical steel, making it difficult to meet market demands.

[0026] To address the aforementioned issues, embodiments of this application provide an electrical steel and its manufacturing method. By scientifically allocating the reduction rate across multiple rolling passes, particularly setting the first pass reduction rate to a large deformation of 55%–65%, a strong deformation penetration force can be generated, effectively breaking down the coarse columnar crystals in the continuously cast billet and deeply welding the porosity and microcracks in the center of the billet, significantly improving the internal density of the material. The second pass maintains a relatively high reduction rate of 45%–55%, further homogenizing the deformation in the thickness direction of the slab. Controlling the reduction rate of the third and subsequent passes at 20%–40% avoids edge cracking or poor plate shape caused by excessive cumulative deformation resistance. This gradient reduction system, with a large reduction at the beginning and a smaller reduction at the end, ensures the uniformity of the microstructure across the entire thickness range of the hot-rolled plate. The uniform and dense microstructure of the hot-rolled plate lays a solid foundation for the nucleation and growth of favorable textures (such as the {100} texture in non-oriented silicon steel) in subsequent cold rolling and annealing processes. By combining the specific chemical composition design of this application, such as a reasonable Si, Al, and Mn ratio to improve resistivity and suppress harmful texture, the final electrical steel can effectively reduce hysteresis loss and eddy current loss, thereby significantly reducing the iron loss of the finished product, while obtaining high magnetic induction intensity to meet the stringent requirements of high-efficiency energy-saving motors for the magnetic properties of materials. This solution is tailored to the characteristics of thin slabs with a thickness of 40mm~60mm, and a matching hot rolling deformation regime is designed. This not only overcomes the problems of large rolling load fluctuations and high equipment wear caused by improper reduction distribution in traditional processes, but also fully utilizes the advantages of short continuous casting and rolling processes and fast solidification and cooling rates for thin slabs (which are beneficial for suppressing the precipitation of harmful second phases). While ensuring high product performance, it effectively improves production speed and yield, and reduces manufacturing costs.

[0027] The electrical steel and its manufacturing method described in this application are described in detail below.

[0028] like Figures 1 to 3 As shown, an embodiment of this application provides a method for manufacturing electrical steel, including steelmaking, thin slab continuous casting and rolling, heating and rolling, pickling and cold rolling, and annealing and coating. Steelmaking: Molten iron is pretreated, smelted in a converter, and refined to obtain refined molten steel. Thin slab continuous casting and rolling: Refined molten steel is poured into a ladle and continuously cast to obtain a continuously cast billet with a thickness H of 40mm~60mm. Heating and rolling: The continuously cast billet is heated in a heating furnace and then rolled in multiple passes. In the multi-pass rolling, the reduction rate of the first pass is 55%≤η1≤65%, the reduction rate of the second pass is 45%≤η2≤55%, and the reduction rate of the third and subsequent passes is controlled at 20%~40%. After rolling, the billet is coiled to obtain a hot-rolled steel coil. Pickling and cold rolling: The hot-rolled steel coil is pickled and then cold-rolled to obtain a cold-rolled steel coil. Annealing and Coating: Cold-rolled steel coils are annealed, coated, and cooled to obtain electrical steel. Electrical steel comprises the following chemical composition by mass percentage: C≤0.0035%, 0.95%≤Si≤1.10%, 0.75%≤Mn≤0.90%, P≤0.040%, S≤0.0050%, 0.35%≤Al≤0.55%, with the remainder being iron and unavoidable trace elements.

[0029] The steelmaking process involves pretreating molten iron to remove sulfur and phosphorus, followed by precise control of the steel's composition through converter smelting and refining processes, ultimately yielding refined molten steel that meets chemical composition requirements. Strict refining control effectively reduces the content of harmful impurities such as carbon, sulfur, and phosphorus in the steel, improving its purity and laying a pure matrix foundation for subsequent production of electrical steel with low iron loss and high magnetic induction.

[0030] The thin slab continuous casting and rolling process refers to pouring refined molten steel into a tundish and casting it into a thin slab with a thickness H of 40mm to 60mm using a continuous casting machine. The thin slab continuous casting process offers rapid solidification and cooling, significantly refining the initial grain size of the slab and suppressing the precipitation of large inclusions. The 40mm to 60mm thickness range balances the stability of continuous casting production with the deformation requirements of subsequent hot rolling, avoiding the risk of surface defects in excessively thin slabs.

[0031] The heating and rolling process refers to feeding the continuously cast billet into a heating furnace and heating it to a suitable temperature, followed by multiple hot rolling passes. The first pass has a reduction rate controlled at 55%–65%, the second pass at 45%–55%, and the third and subsequent passes at 20%–40%. After rolling, the billet is coiled into a hot-rolled steel coil. The large reduction in the first and second passes allows for deep deformation penetration, effectively breaking down the coarse columnar crystals in the center of the billet, welding together internal porosity and microcracks, and increasing the material density. The moderate reduction in subsequent passes avoids shape defects caused by excessive deformation resistance, ensuring the uniformity of the hot-rolled plate's microstructure along the thickness direction.

[0032] Pickling and cold rolling are processes used to remove the iron oxide scale from the surface of hot-rolled steel coils, followed by cold rolling deformation to obtain cold-rolled steel coils of the target thickness. Pickling removes the oxide layer that affects surface quality; the cold rolling process provides the necessary deformation energy, induces the formation of favorable textures, and provides the microstructure genetic basis for ultimately obtaining excellent magnetic properties.

[0033] Annealing and coating involve subjecting cold-rolled steel coils to high-temperature annealing to eliminate work hardening and develop a favorable texture, followed by coating with an insulating layer and cooling. The annealing process completes the recrystallization process, significantly reducing iron loss and increasing magnetic induction intensity; the insulating coating increases inter-sheet resistance, further reducing eddy current losses, ultimately yielding high-performance finished electrical steel.

[0034] The electrical steel manufacturing method provided in this application solves the problems of insufficient core deformation penetration and uneven microstructure in traditional processes by combining a specific thin slab thickness range (40mm~60mm) with an optimized hot rolling multi-pass reduction ratio distribution system (especially the large reduction in the first two passes). This method not only fully utilizes the advantages of short continuous casting and rolling process and rapid cooling of thin slabs, but also refines the grains and improves the texture through precise deformation control. The final electrical steel produced has extremely low iron loss and high magnetic induction intensity, significantly improving the electromagnetic properties of the material.

[0035] In some embodiments of this application, in the thin slab continuous casting and rolling step, the thickness H of the continuously cast slab is 55mm~60mm.

[0036] This numerical range falls within the thicker specification range of thin slab continuous casting technology. In terms of process implementation, this thickness is typically achieved by selecting a crystallizer of a specific thickness or controlling the liquid core reduction of the continuous casting machine. Choosing a thickness of 55mm to 60mm means that a relatively ample slab cross-section is retained during the continuous casting stage. This requires subsequent heating and rolling processes to have sufficient deformation capacity to match the deformation resistance and heat capacity changes brought about by this thickness. This embodiment aims to find the optimal balance between continuous casting stability and hot rolling deformation penetration by setting a specific thickness and combining it with the aforementioned high reduction rolling process.

[0037] Specifically, a billet thickness of 5mm to 60mm provides ample space for total reduction in subsequent hot rolling processes. Combined with the high reduction rate regime of "55% to 65% in the first pass and 45% to 55% in the second pass" described in this application, this thicker billet ensures that deformation force is effectively transferred to the center (core) of the slab. Strong shear deformation can completely break up any coarse columnar crystals that may exist in the center of this thickness of billet and effectively weld together the porosity and microcracks in the core. If the billet is too thin (e.g., <45mm), the deformation penetration in the core is often insufficient under the same rolling stroke, easily leaving casting defects. The 55mm to 60mm thickness precisely solves this problem of a "dead zone in core deformation," significantly improving the density of the material.

[0038] In thin slab continuous casting, excessively thin slabs (e.g., <50mm) often face challenges such as limited casting speed and difficulty in controlling molten steel level fluctuations in the crystallizer, easily leading to longitudinal cracks or inclusions on the slab surface. Setting the thickness to 55mm~60mm helps maintain a higher continuous casting speed and a stable heat flow distribution in the crystallizer, thereby significantly reducing the incidence of surface defects in the slab. For electrical steel, which is extremely sensitive to surface quality, this directly reduces the risk of strip breakage during subsequent pickling and cold rolling processes, improving the yield.

[0039] The 55mm~60mm thickness endows the billet with a large heat capacity, resulting in a relatively slow temperature drop rate during rough rolling after exiting the furnace. This thermal characteristic facilitates sufficient recrystallization of austenite during the rough rolling stage, thereby refining the austenite grains. Fine and uniform austenite grains are a key prerequisite for the subsequent formation of favorable textures (such as Gaussian or cubic textures), which in turn helps to improve the magnetic induction intensity of the final 50W800H product and reduce iron loss.

[0040] In some embodiments of this application, during the heating and rolling steps, the reduction rate of the first rolling pass is 50%≤η1≤55%, and the reduction rate of the second rolling pass is 50%≤η2≤52%.

[0041] The reduction rate η1 of the first rolling pass is controlled between 50% and 55%, and the reduction rate η2 of the second rolling pass is controlled between 50% and 52%. This means that in the initial stage of hot rolling, two consecutive passes involve large deformation exceeding 50%. This process setting requires the rolling mill to have high rigidity and rolling force output capacity, and also requires the continuously cast billet to have a uniform and suitable heating temperature before entering the rolling mill, so as to ensure that the material can undergo sufficient dynamic recrystallization under such large continuous deformation, avoiding excessive accumulation of work hardening.

[0042] Maintaining a high pressure reduction rate of over 50% in two consecutive passes generates extremely strong deformation penetration. The 50%–55% deformation in the first pass is sufficient to break up the coarse grains on the surface of the slab, while the subsequent 50%–52% deformation in the second pass further pushes the deformation zone towards the center of the slab. This "double impact" effect ensures that even the 55mm–60mm thick slab core undergoes sufficient plastic deformation, effectively welding together the central porosity and microcracks generated during continuous casting, significantly improving the density of the hot-rolled plate, and eliminating the damage to the final magnetic properties caused by internal defects.

[0043] Within the high-pressure reduction range of 50%–55%, the deformation energy stored in austenite is extremely high, sufficient to drive fully dynamic recrystallization. The large deformation amounts in two consecutive passes cause the austenite grains to undergo two intense cycles of fragmentation and reconstruction in the first and second passes, resulting in extremely fine and uniform recrystallized austenite grains. These fine austenite grains form the basis for favorable textures during subsequent phase transformations and annealing, contributing to improved magnetic flux density in the finished product.

[0044] By controlling the reduction rates of the first and second passes within similar ranges of 50%–55% and 50%–52%, respectively, the problem of excessively high rolling force peaks that could result from excessive reduction rates in a single pass (e.g., >60%) is avoided. This relatively balanced load distribution ensures sufficient total deformation while preventing excessive elastic flattening of the rolls or loss of strip shape control (such as waviness or warping) caused by excessive load in a single pass. This is crucial for ensuring the transverse thickness uniformity of hot-rolled strip, thereby providing raw materials with excellent strip shape for subsequent cold rolling.

[0045] In some embodiments of this application, in the converter smelting process, the carbon content at the tapping end of the converter smelting is controlled to be 0.025% to 0.060%, and the converter end temperature is 1655℃ to 1695℃.

[0046] Specifically, the carbon content at the tapping endpoint is strictly controlled within the low-carbon range of 0.025% to 0.060%, while the converter endpoint temperature is controlled within the high-temperature range of 1655℃ to 1695℃. This process setting requires the use of dynamic control models (such as sub-lance detection or flue gas analysis) to achieve high-precision endpoint accuracy, in order to avoid post-blowing or over-oxidation caused by carbon-temperature mismatch. This parameter range is specifically optimized for the stringent requirements of purity and inclusion control for the electrical steel (especially 50W800H) described in this application, aiming to control the oxidizability and cleanliness of the molten steel from the source.

[0047] By controlling the final carbon content between 0.025% and 0.060%, the principle of carbon-oxygen balance was utilized. Compared to smelting with extremely low carbon (<0.02%), this range effectively inhibits steel over-oxidation and significantly reduces the dissolved oxygen content ([O]) in the final steel. Low oxygen content means fewer sources of oxide inclusions (such as Al2O3, SiO2, etc.) in the steel, which is crucial for electrical steel requiring high magnetic induction and low iron loss, as it can significantly reduce the obstruction of magnetic domain movement by inclusions.

[0048] The temperature range of 1655℃ to 1695℃ ensures that the molten steel has sufficient superheat at tapping, meeting the temperature requirements of subsequent refining and continuous casting, while avoiding the need for "post-blowing" due to excessively low temperatures. Post-blowing not only significantly increases the oxygen content of the molten steel but also leads to severe erosion of the furnace lining refractory material, increasing the source of inclusions in the steel. Furthermore, avoiding post-blowing reduces the risk of nitrogen absorption by the molten steel, preventing age hardening and deterioration of magnetic properties caused by increased nitrogen content.

[0049] A suitable endpoint carbon content (0.025%–0.060%) provides favorable reaction kinetics for subsequent refining processes. At this carbon content, the stirring energy of the molten pool in the initial stage of refining is moderate, which is conducive to the rapid formation of a highly fluid reducing slag, thereby achieving efficient desulfurization and deoxidation. Simultaneously, this endpoint control reduces the alloying burden during tapping, increases the yield of alloying elements such as silicon and aluminum, and lowers production costs.

[0050] The endpoint temperature of 1655℃ to 1695℃, combined with the subsequent thin slab continuous casting process of this application, ensures good fluidity of the molten steel in the tundish and crystallizer. This effectively prevents nozzle blockage or surface cracking of the slab due to excessively low temperature, and also avoids center segregation and shrinkage cavities of the slab due to excessively high temperature, providing thermal assurance for obtaining 55mm to 60mm thick continuously cast slabs with excellent internal quality.

[0051] In some embodiments of this application, refining includes RH refining treatment; after RH refining treatment, the sulfur (S) content of the refined molten steel is controlled to be ≤0.0015%, and the temperature of the refined molten steel is ≥1250℃.

[0052] In a preferred embodiment of this application, RH (Ruhrstahl-Heraeus) vacuum refining is used as the core process, and the cleanliness and thermal state of the treated molten steel are strictly limited.

[0053] Specifically, through RH refining, the sulfur (S) content in the molten steel is deeply purified to 0.0015% or below, while the temperature of the refined molten steel exiting the station is controlled at 1250℃ or above. RH refining utilizes the principle of vacuum circulation degassing. Under extremely low vacuum conditions (typically below 133 Pa), a powerful circulation flow fully exposes the molten steel to a vacuum state, thereby efficiently removing gases (such as hydrogen and oxygen) from the steel and promoting the flotation of inclusions. This embodiment aims to provide high-quality molten steel with both high purity and good thermal conditions for subsequent thin slab continuous casting by precisely controlling the composition and temperature at the refining endpoint.

[0054] By employing the specific RH refining and endpoint control scheme described above, the sulfur content is strictly controlled below 0.0015%, which minimizes the formation of non-metallic inclusions such as sulfides (e.g., MnS) in the steel. For electrical steel, fine and dispersed inclusions severely hinder grain growth during annealing and increase resistance to magnetic domain wall movement. Deep desulfurization achieved through RH refining significantly improves the purity of the molten steel, providing a crucial guarantee for obtaining low iron loss and high magnetic induction in the final product.

[0055] Furthermore, RH vacuum treatment not only achieves deep desulfurization but also reduces the content of harmful gases such as hydrogen and oxygen in molten steel to extremely low levels (e.g., hydrogen content can be reduced to 2×10⁻⁶). -6 (See below). This effectively prevents subcutaneous bubbles or internal cracks from forming during the solidification process of the continuously cast billet, while reducing the amount of oxide inclusions, ensuring the internal density of the 55mm~60mm thick continuously cast billet, and avoiding the risk of lamellar tearing during subsequent rolling.

[0056] In addition, controlling the temperature of the refined molten steel at 1250℃ or above provides sufficient superheat in the tundish for subsequent thin slab continuous casting (the tundish superheat usually needs to be controlled between 15℃ and 35℃). Suitable high-temperature molten steel has good fluidity and filling capacity, which can effectively prevent nozzle blockage or surface cracks of the slab caused by excessive temperature drop during thin slab continuous casting, ensuring the stability of the continuous casting speed and the surface quality of the slab.

[0057] Meanwhile, the strong circulating stirring effect during the RH refining process ensures that the chemical composition and temperature of the molten steel are highly uniform throughout the furnace. This uniformity is transferred to the continuous casting process, which can reduce center segregation and shrinkage defects in the slab. Combined with the thin slab continuous casting and rolling process of this application, it helps to obtain a high-quality electrical steel matrix with uniform microstructure and consistent properties.

[0058] In some embodiments of this application, the RH refining process includes vacuum decarburization, deoxidation and alloying, and a circulating purification process. The vacuum decarburization process includes a pure vacuum cycle, with a cycle time of 4 to 8 minutes; the circulating purification process takes 6 to 10 minutes.

[0059] Specifically, the RH refining process encompasses three core steps: vacuum decarburization, deoxidation and alloying, and circulating purification. The vacuum decarburization step employs a pure vacuum circulation mode without forced oxygen blowing, with the pure vacuum circulation time strictly controlled between 4 and 8 minutes. The subsequent circulating purification step is controlled between 6 and 10 minutes. This process design fully utilizes the metallurgical characteristics of RH vacuum circulation, achieving efficient decarburization and deep purification of the molten steel within a specific time window through the carbon-oxygen reaction under vacuum and the large circulation flow rate of the molten steel.

[0060] By employing the specific time control scheme described above, the pure vacuum circulation time is controlled within 4 to 8 minutes, which fully utilizes the dissolved oxygen inherent in the molten steel to undergo a vacuum carbon deoxidation reaction with carbon (C + O → CO↑). For the low-carbon electrical steel required in this application (final carbon content 0.025% to 0.060%), this time window is sufficient to accurately reduce the carbon content to the target range (e.g., below 0.003%), while avoiding over-oxidation of the molten steel caused by excessively long decarburization time or forced oxygen blowing. This not only reduces the alloy consumption for subsequent deoxidation but also reduces the formation of oxide inclusions at the source.

[0061] The 6-10 minute circulating purification process provides ample time for tiny non-metallic inclusions and dissolved gases (especially hydrogen) in the molten steel to float and escape. Driven by the powerful circulating flow rate of RH, the molten steel is continuously drawn into the vacuum chamber and broken into droplets, greatly increasing the reaction surface area. This process can significantly reduce the hydrogen content in the steel (down to 2 × 10⁻⁶). -6 (The following), and promotes the aggregation and growth of fine inclusions, which float to the slag layer, greatly improving the cleanliness of the molten steel and avoiding subcutaneous bubbles or internal cracks in the continuously cast billet.

[0062] By controlling the total time for decarburization and purification within a reasonable range (approximately 10 to 18 minutes), the metallurgical reaction was ensured to proceed fully while avoiding excessive temperature drop in the molten steel due to an excessively long refining cycle. Suitable temperature and sufficient circulation time ensured highly uniform chemical composition and temperature throughout the furnace of molten steel, providing high-quality molten steel with stable thermal properties and uniform composition for subsequent thin slab continuous casting, effectively reducing center segregation in the cast slab.

[0063] Through precise coordination of the aforementioned timing and processes, the content of carbon, sulfur, oxygen, hydrogen, and non-metallic inclusions in the molten steel is reduced to extremely low levels. The high-purity steel matrix promotes sufficient grain growth and favorable texture development during subsequent annealing processes, thereby significantly reducing iron loss in electrical steel and increasing magnetic induction intensity.

[0064] In some embodiments of this application, during the continuous casting process, the superheat of the tundish is controlled at 15°C to 30°C, a high-silica insulating covering agent and a special protective slag for electrical steel are used in the tundish, and the billet casting speed is controlled at 4.5 m / min to 5.0 m / min.

[0065] The process involves strictly controlling the superheat of the molten steel in the tundish within the ideal range of 15℃ to 30℃, and using a high-silica insulating covering agent and a special protective slag for electrical steel. Simultaneously, to match the efficient production rhythm of thin slab continuous casting and rolling, the casting speed is significantly increased and stably controlled within a high-speed range of 4.5m / min to 5.0m / min. This combined process design aims to maximize production efficiency while ensuring slab quality through precise temperature control and high-efficiency continuous casting speed.

[0066] By employing the specific continuous casting process parameters described above, controlling the superheat of the tundish within the range of 15℃ to 30℃ effectively balances the relationship between casting speed and billet solidification quality. Appropriate superheat avoids both excessively high temperatures leading to coarse columnar grains and severe central segregation in the billet, and excessively low temperatures causing nozzle blockage. This temperature window provides excellent steel fluidity for high-speed continuous casting at speeds of 4.5 m / min to 5.0 m / min, ensuring a uniform solidification structure within the billet even under high-speed casting conditions.

[0067] Furthermore, the high casting speed of 4.5m / min to 5.0m / min fully leverages the core advantages of the thin slab continuous casting and rolling process: "short process, fast pace." Compared to traditional continuous casting or low-speed processes, this high-speed casting significantly increases output per unit time and greatly shortens the production cycle, thereby effectively reducing the manufacturing cost of electrical steel.

[0068] Using a high-silica insulating covering agent can effectively reduce heat loss from molten steel in the tundish and stabilize the casting temperature. The special protective slag for electrical steel is specifically designed for the physicochemical properties of the electrical steel (containing higher Si and Al content) in this application. It can maintain a uniform and well-lubricated liquid slag layer (typically above 10 mm) in the crystallizer even at high casting speeds (4.5 m / min to 5.0 m / min). This greatly reduces the risk of sticking and leakage caused by excessive casting speed and effectively improves the surface quality of the billet, reducing surface cracks and inclusions.

[0069] In conjunction with the aforementioned high-speed casting process, the production line typically employs forced cooling in the secondary cooling zone (e.g., the secondary cooling water volume is controlled at 2.5L / kg to 2.8L / kg). This forced cooling mode accelerates the solidification rate of the billet, effectively preventing steel leakage accidents at high casting speeds of 4.5m / min to 5.0m / min. It also helps refine the solidification structure of the billet, providing high-quality continuously cast billets for subsequent hot rolling processes. In some embodiments of this application, during the heating and rolling steps, the heating temperature of the billet is controlled to be 1100℃~1160℃, the furnace exit temperature is 1020℃~1080℃, and the final rolling temperature is 870℃~930℃.

[0070] Specifically, the heating temperature of the continuously cast billet after entering the heating furnace is strictly controlled at 1100℃~1160℃, the temperature when it exits the furnace and is ready to enter the rolling mill is controlled at 1020℃~1080℃, and after multiple rolling passes, the final rolling temperature is precisely controlled at 870℃~930℃. This series of temperature parameters fully considers the phase transformation law and recrystallization characteristics of the electrical steel (containing higher Si and Al content) in this application, aiming to optimize the evolution process of the austenite structure through precise control of the hot rolling temperature window.

[0071] By employing the specific temperature control scheme described above, the billet heating temperature is controlled between 1100℃ and 1160℃, effectively preventing excessive dissolution of precipitates such as AlN and MnS in the steel due to excessively high heating temperatures (e.g., exceeding 1250℃). If these precipitates re-precipitate as fine particles during subsequent rolling and cooling, they will severely deteriorate the iron loss of electrical steel. This temperature range ensures good plasticity in the billet while maximally suppressing the solid solution and re-precipitation of harmful precipitates, laying a microstructural foundation for achieving low iron loss in the finished product.

[0072] The furnace exit temperature is controlled between 1020℃ and 1080℃, providing an ideal initial thermal state for subsequent high-reduction rolling. This temperature range ensures that the billet has sufficient plasticity to withstand the high-reduction rolling described in this application, while avoiding excessively low rolling force and insufficient deformation penetration due to excessively high temperature, or excessive mill load due to excessively low temperature. This effectively guarantees the thickness accuracy and shape quality of the hot-rolled strip in both the transverse and longitudinal directions.

[0073] Precisely controlling the final rolling temperature within the range of 870℃ to 930℃ ensures that the rolling process occurs within the ideal temperature range of the austenite recrystallization region or close to the two-phase region. Completing the final deformation within this temperature window promotes sufficient dynamic or static recrystallization of austenite, resulting in fine and uniform austenite grains. These fine and uniform austenite grains are more conducive to inducing the nucleation and growth of favorable textures (such as Gaussian or cubic textures) during subsequent cooling and annealing, thereby significantly improving the magnetic induction intensity of the electrical steel.

[0074] Furthermore, the final rolling temperature of 870℃ to 930℃ effectively avoids the low-temperature range that easily leads to abnormal grain coarsening or the formation of banded structures. If the final rolling temperature is too low (e.g., below 850℃), deformation bands or mixed-grain structures are easily formed in the hot-rolled plate. These defects will be inherited by the cold rolling and annealing processes, seriously hindering the development of favorable textures. Precise control of the final rolling temperature ensures the uniformity of the microstructure of the hot-rolled plate, significantly improving the stability and consistency of the magnetic properties of the final electrical steel product.

[0075] In some embodiments of this application, the coiling temperature is controlled at 700°C to 740°C during the heating and rolling steps.

[0076] Specifically, after multiple rolling passes (with the final rolling temperature controlled between 870℃ and 930℃), the hot-rolled strip undergoes laminar flow cooling and is finally coiled at a high temperature of 700℃ to 740℃. This temperature setting is typical of a "high-temperature coiling" process, far exceeding the 550℃ to 650℃ coiling temperature commonly used in traditional electrical steel production. This process requires the production line to have precise temperature control capabilities to ensure that the steel coil undergoes a specific microstructure evolution after coiling.

[0077] A high-temperature coiling process of 700℃~740℃ is adopted, which is higher than the recrystallization critical temperature of non-oriented electrical steel. After being coiled at this temperature, the steel coil can undergo static recrystallization using its own residual heat, achieving a "self-annealing" effect. This process can effectively eliminate the deformation structure during hot rolling, achieve equiaxed microstructure, and thus completely eliminate the surface "corrugated defects" caused by fibrous structure inheritance that are common in thin slab continuous casting and rolling processes, significantly improving the surface quality of hot-rolled plates and final products.

[0078] High-temperature coiling provides ample thermodynamic conditions for second-phase precipitates such as AlN and MnS in the steel, promoting their full aggregation and coarsening during coiling and subsequent slow cooling. Compared to fine, dispersed precipitates, the coarse precipitates significantly reduce their hindering effect on grain growth during subsequent annealing. This is beneficial for obtaining a coarse, uniform, and advantageous grain structure in the final annealing process, thereby significantly reducing the iron loss of electrical steel and improving its magnetic properties.

[0079] Although high-temperature coiling was employed, the upper limit of the temperature was controlled at 740℃, effectively preventing the formation of excessively thick iron oxide scale on the surface of the hot-rolled plate due to excessively high coiling temperatures (such as exceeding 760℃ or higher). Excessively thick oxide scale greatly increases the difficulty of subsequent pickling processes, easily leading to incomplete pickling or over-pickling. The 700℃~740℃ range ensures both the evolution of microstructure and properties and good pickling processability.

[0080] If the coiling temperature is too low (e.g., below 600℃~650℃), the hot-rolled sheet will form a large number of refined grains and deformation bands. This is not only detrimental to grain growth during subsequent annealing, but also leads to higher iron loss in the finished product. Precise control of 700℃~740℃ avoids the grain refinement problem caused by low-temperature coiling, and also prevents the oxidation risks caused by excessively high temperatures. This provides an ideal genetic basis for the hot-rolled microstructure of 50W800H electrical steel with high magnetic induction and low iron loss.

[0081] In some embodiments of this application, during the pickling and cold rolling steps, the cold rolling elongation is controlled to be 2.5% to 3.0%, and the cold rolling relative reduction is controlled to be 75% to 85%.

[0082] Specifically, during the pickling stage, the elongation of the tension leveler is strictly controlled within a high elongation range of 2.5% to 3.0%; in the subsequent cold rolling stage, the relative total reduction rate is controlled within a large reduction range of 75% to 85%. This combined process design aims to lay a solid organizational foundation for obtaining excellent magnetic properties in the subsequent annealing process through enhanced mechanical descaling and deep cold rolling deformation energy storage.

[0083] By employing the specific elongation and reduction control scheme described above, the elongation of cold-rolled strip is controlled within the range of 2.5% to 3.0%, which is considered a relatively high elongation range. Due to the significant difference in plastic elongation between the iron oxide scale and the steel matrix, repeated bending and stretching with high elongation can cause numerous cracks and extreme porosity in the iron oxide scale on the strip surface, even leading to its direct detachment from the matrix. This not only significantly accelerates the subsequent chemical reaction of the iron oxide scale with the acid solution, completely eliminating under-pickled defects, but also effectively removes particulate inclusions from the strip surface, providing an extremely clean sheet surface for cold rolling and preventing roll scratches and surface streaks on the finished product.

[0084] By controlling the relative reduction rate of cold rolling within a large reduction range of 75% to 85%, extremely high distortion energy can be stored within the steel strip. In the subsequent continuous annealing process, this high distortion energy is the core driving force for recrystallization, which can greatly promote {111} <112> This allows for the nucleation and growth of favorable recrystallization textures while suppressing the formation of unfavorable textures. The significant enhancement of favorable textures directly increases the magnetic induction intensity of electrical steel.

[0085] A high reduction rate of 75%–85%, combined with the aforementioned high-temperature coiling process, enables the production of uniform and coarse recrystallized grains during annealing. These coarse and uniform grains effectively reduce the number of grain boundaries, thereby significantly reducing the resistance to domain wall movement (hysteresis loss) and eddy current loss. This is crucial for achieving the core performance indicator of low iron loss in the electrical steel (e.g., 50W800H) of this application.

[0086] High cold rolling reduction (75%–85%) not only optimizes magnetic properties but also significantly improves the material's plastic strain ratio (r-value). This results in finished electrical steel products possessing excellent electromagnetic properties as well as good cold forming performance, enabling them to meet the processing requirements of complex stamped parts.

[0087] In some embodiments of this application, during the annealing and coating steps, the annealing temperature is controlled to be 900℃~930℃, the holding time is 1min~2min, and the unit operating speed is 120m / min~150m / min.

[0088] Specifically, the annealing temperature of the cold-rolled steel coil is strictly controlled within the high-temperature range of 900℃ to 930℃, and the holding time at this temperature is controlled within 1 min to 2 min. Simultaneously, the operating speed of the entire unit is matched and controlled within 120 m / min to 150 m / min. This combined process setting fully considers the recrystallization kinetics and grain growth law of the high-silicon aluminum electrical steel in this application, aiming to obtain optimal finished product microstructure and magnetic properties while ensuring production efficiency through a precise high-temperature, short-time annealing regime.

[0089] By employing the specific annealing process parameters described above and controlling the annealing temperature between 900℃ and 930℃, sufficient thermal activation energy can be provided to the steel strip, allowing the distortion energy stored during cold rolling to be released rapidly and driving complete recrystallization of the matrix. Combined with a holding time of 1 to 2 minutes, this ensures sufficient recrystallization while also promoting appropriate grain growth. Large and uniform grains effectively reduce the number of grain boundaries, significantly reducing the resistance to domain wall movement (hysteresis loss) and eddy current losses, thereby substantially reducing the iron loss of electrical steel.

[0090] The high temperature range of 900℃ to 930℃ is very favorable for {111} <112> The favorable recrystallization texture is nucleated and preferentially grown. During the 1-2 minute holding period, these favorable textures can fully develop and suppress the interference of unfavorable textures. The resulting strong favorable texture directly endows the electrical steel with extremely high magnetic induction intensity, meeting the core requirements of high-efficiency motors for the magnetic properties of materials.

[0091] By controlling the unit's operating speed at 120m / min to 150m / min, a perfect process match is achieved with the annealing temperature of 900℃ to 930℃ and the holding time of 1min to 2min. This high-speed operating parameter fully leverages the advantages of the continuous annealing production line—its "fast pace and high efficiency"—ensuring that the strip steel achieves the ideal thermal history in the furnace while significantly increasing the output per unit time and effectively reducing manufacturing costs.

[0092] For the electrical steel containing high levels of Si and Al in this application, 900℃ to 930℃ is an optimized temperature window. If the annealing temperature is too high (e.g., exceeding 1000℃) or the holding time is too long, it can easily lead to excessive grain coarsening or even abnormal grain growth, which will deteriorate the magnetic and mechanical properties of the material. If the temperature is too low or the time is too short, it will lead to incomplete recrystallization, and the residual cold-rolled structure will seriously impair the magnetic induction. The precise control of this embodiment effectively avoids the above risks and ensures the stability of the finished product's performance.

[0093] Embodiments of this application also provide an electrical steel comprising the following chemical composition by mass percentage: C≤0.0035%, 0.95%≤Si≤1.10%, 0.75%≤Mn≤0.90%, P≤0.040%, S≤0.0050%, 0.35%≤Al≤0.55%, with the remainder being iron and unavoidable trace elements.

[0094] Carbon (C) is the main harmful element in electrical steel that causes magnetic aging and increases hysteresis loss. Strictly controlling the carbon content to below 0.0035% can minimize the pinning effect of solid-solution carbon atoms on the movement of magnetic domain walls, thereby significantly reducing iron loss and ensuring the stability of the magnetic properties of electrical steel during long-term use.

[0095] Silicon (Si) and aluminum (Al) are the core alloying elements for improving the resistivity of electrical steel. This application controls Si at 0.95%–1.10% and Al at 0.35%–0.55%, and their synergistic effect significantly increases the resistivity of the steel matrix. This increase in resistivity directly reduces eddy current losses under alternating magnetic fields. Simultaneously, this silicon content range (approximately 1%) ensures low iron loss while effectively avoiding the increased material brittleness and rolling difficulties caused by excessively high silicon content (e.g., exceeding 3%), thus considering the feasibility of industrial production.

[0096] The addition of manganese (Mn) is controlled within a relatively high range of 0.75% to 0.90%. Manganese can combine with sulfur in steel to form MnS, eliminating the harmful effects of sulfur and improving the hot workability of the steel. Furthermore, an appropriate amount of manganese promotes moderate grain growth during annealing. Coarse and uniform grains reduce the number of grain boundaries, lower hysteresis loss, and simultaneously help improve the magnetic induction intensity (magnetism) of the material.

[0097] Strictly controlling sulfur (S) content below 0.0050% can significantly reduce the formation of fine non-metallic inclusions such as MnS, avoiding their hindrance to grain growth during annealing and interference with magnetic domain movement. Simultaneously, controlling phosphorus (P) content below 0.040% avoids phosphorus-induced brittleness while appropriately utilizing its solid solution strengthening effect and preventing it from deteriorating magnetic properties.

[0098] In summary, this chemical composition system, through the synergistic effect of its elements, achieves a good match between low iron loss and high magnetic induction while ensuring good cold and hot working performance, making it suitable for the manufacture of motor cores with high energy efficiency requirements. Specific Implementation

[0099] Comparative Example 1 This comparative example uses a conventional thin slab continuous casting and rolling process, and the specific steps are as follows: Steelmaking and continuous casting: Molten steel from heat number 24102831 was used. The tundish superheat was 28℃, the casting speed was 4.3m / min, and the billet thickness was 70mm.

[0100] Hot continuous rolling: The billet is heated to approximately 1150℃, the final rolling temperature is controlled at 920~923℃, and the coiling temperature is 720℃. Key difference: The reduction rates of finishing mills F1 and F2 are 48% and 45%, respectively.

[0101] Pickling and cold rolling: stretching elongation 2.8%, cold rolling reduction 80%.

[0102] Continuous annealing coating: annealing temperature 920℃, holding time 1.5 minutes, speed approximately 135m / min.

[0103] The following table shows the test results for the product in Comparative Example 1.

[0104] Table 1 Furthermore, please refer to the following: Figure 4 The image shows a metallographic photograph of the microstructure of a hot-rolled coil, Comparative Example 1. Figure 4 It can be seen that the hot-rolled plate of Comparative Example 1 has poor microstructure uniformity, with obvious banded structure and uneven grain size. This banded structure is usually caused by the inheritance of unbroken columnar crystals in the center of the billet, which leads to increased magnetic anisotropy and increased iron loss.

[0105] Example 1 This embodiment adopts the thin slab continuous casting and rolling (CSP) process route, and the specific steps are as follows: Steelmaking and continuous casting: Molten steel from heat number 25107308 was used and continuously cast after RH vacuum treatment. The superheating temperature of the tundish was controlled at 25℃, the casting speed was 4.8m / min, and the billet thickness was 60mm.

[0106] Hot continuous rolling: The billet is heated to 1140℃, and the furnace exit temperature is 1048~1053℃. Heavy reduction rolling is performed on the finishing mill, with a reduction rate of 55% on the F1 stand and 52% on the F2 stand. The final rolling temperature is controlled at 900~902℃, and the coiling temperature is controlled at 720℃.

[0107] Pickling and cold rolling: Iron oxide scale is removed by tension leveling with an elongation of 2.8%, and the total cold rolling reduction is controlled at 80%.

[0108] Continuous annealing coating: recrystallization annealing is performed by holding at 930℃ for 1.5 minutes, with the unit operating speed at approximately 140 m / min, followed by a semi-organic coating treatment.

[0109] The following table shows the test results for the product of Example 1.

[0110] Table 2 Please refer to the above. Figure 5 The image shows a radial metallographic photograph of the microstructure of the hot-rolled coil from Example 1. Figure 5 As can be seen, the hot-rolled plate of Example 1 has a uniform and fine microstructure, with no obvious banded structure and a grain size of 10.5. This indicates that the "high reduction rate + high temperature coiling" process of this application effectively breaks down the columnar crystals of the billet, promotes recrystallization, and lays a good microstructure foundation for obtaining excellent magnetic properties in the future.

[0111] By comparing Example 1 and Comparative Example 1, it can be seen that: Example 1: Electromagnetic performance is significantly improved. Iron loss: The comparative example averaged 3.95 W / kg, while the example reduced it to 3.86 W / kg. The example reduced iron loss by increasing the front frame reduction ratio (55% / 52%), which completely broke up the columnar crystals and eliminated the banded structure.

[0112] Magnetic induction: The average value of the examples was 1.718 T, which was better than the 1.707 T of the comparative examples.

[0113] Surface quality improvement: Due to insufficient reduction rate (48% / 45%), the columnar crystals were not completely broken, resulting in banded structure in the hot-rolled plate, which was inherited to the surface of the finished product and formed "corrugated stripes".

[0114] The example obtained a uniform hot-rolled microstructure by using a large reduction rate and optimizing the composition (appropriately increasing Mn), and the finished product surface was free of corrugated stripe defects.

[0115] Controlling the reduction rates of F1 and F2 at 50%~55% (Example) is necessary compared to a range lower than this (Comparative Example). Simultaneously, it demonstrates the feasibility of ensuring tissue uniformity while maintaining a high drawing speed (4.8 m / min) through specific components (Mn 0.88%) and high-temperature winding (720°C).

[0116] The embodiments described above are not exhaustive, nor do they limit the application to the specific embodiments described herein. Clearly, many modifications and variations can be made based on the above description. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to effectively utilize this application and its modifications. This application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for manufacturing electrical steel, characterized in that, include: Steelmaking: The process of pretreating molten iron, smelting it in a converter, and refining it to obtain refined steel. Thin slab continuous casting and rolling: The refined molten steel is poured into a ladle and continuously cast to obtain a continuously cast slab, the thickness H of which is 40mm~60mm; Heating and rolling: The continuously cast billet is fed into a heating furnace for heating, and after exiting the furnace, it undergoes multiple rolling passes; wherein, in the multiple rolling passes, the reduction rate of the first rolling pass is 55%≤η1≤65%, the reduction rate of the second rolling pass is 45%≤η2≤55%, and the reduction rate of the third and subsequent rolling passes is controlled at 20%~40%; after rolling, it is coiled to obtain hot-rolled steel coils; Pickling and cold rolling: The hot-rolled steel coil is pickled and then cold-rolled to obtain a cold-rolled steel coil; Annealing and coating: The cold-rolled steel coil is annealed, coated and cooled to obtain the electrical steel; The electrical steel comprises the following chemical composition by mass percentage: C≤0.0035%, 0.95%≤Si≤1.10%, 0.75%≤Mn≤0.90%, P≤0.040%, S≤0.0050%, 0.35%≤Al≤0.55%, with the remainder being iron and unavoidable trace elements.

2. The manufacturing method according to claim 1, characterized in that, In the thin slab continuous casting and rolling step, the thickness H of the continuously cast slab is 55mm~60mm.

3. The manufacturing method according to claim 1, characterized in that, In the heating and rolling steps, the reduction rate of the first rolling pass is 50%≤η1≤55%, and the reduction rate of the second rolling pass is 50%≤η2≤52%.

4. The manufacturing method according to claim 1, characterized in that, In the converter smelting process, the carbon content at the final tapping point of the converter smelting is controlled to be 0.025% to 0.060%, and the final converter temperature is 1655℃ to 1695℃.

5. The manufacturing method according to claim 1, characterized in that, The refining process includes RH refining treatment; after the RH refining treatment, the sulfur (S) content of the refined molten steel is controlled to be ≤0.0015%, and the temperature of the refined molten steel is ≥1250℃.

6. The manufacturing method according to claim 5, characterized in that, The RH refining process includes vacuum decarburization, deoxidation and alloying, and circulating purification processes. The vacuum decarbonization process includes a pure vacuum cycle, and the pure vacuum cycle time is 4 min to 8 min; the cycle purification process time is 6 min to 10 min.

7. The manufacturing method according to any one of claims 1-6, characterized in that, In the continuous casting process, the superheat of the tundish is controlled between 15°C and 30°C. The tundish uses a high-silica heat-insulating covering agent and a special protective slag for electrical steel. The billet casting speed is controlled between 4.5 m / min and 5.0 m / min.

8. The manufacturing method according to any one of claims 1-6, characterized in that, In the heating and rolling steps, the heating temperature of the billet is controlled at 1100℃~1160℃, the furnace exit temperature is controlled at 1020℃~1080℃, and the final rolling temperature is controlled at 870℃~930℃.

9. The manufacturing method according to any one of claims 1-8, characterized in that, In the heating and rolling steps, the coiling temperature is controlled at 700℃~740℃.

10. The manufacturing method according to any one of claims 1-6, characterized in that, In the pickling and cold rolling step, the cold rolling elongation is controlled at 2.5% to 3.0%, and the cold rolling relative reduction is controlled at 75% to 85%.

11. The manufacturing method according to any one of claims 1-10, characterized in that, In the annealing and coating steps, the annealing temperature is controlled at 900℃~930℃, the holding time is 1min~2min, and the unit operating speed is 120m / min~150m / min.

12. An electrical steel, characterized in that, It includes the following chemical components by mass percentage: C≤0.0035%, 0.95%≤Si≤1.10%, 0.75%≤Mn≤0.90%, P≤0.040%, S≤0.0050%, 0.35%≤Al≤0.55%, with the remainder being iron and unavoidable trace elements.

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