High-grade non-oriented silicon steel hot-rolled plate edge quality control method and production method based on continuous casting and hot rolling collaborative control

Abstract

The application discloses a high-grade non-oriented silicon steel hot-rolled plate edge quality control method based on continuous casting and hot rolling collaborative control and a production method. The control method comprises the following steps: smelting molten steel, and the end-point molten steel contains Si: 1.5-4.5%, Mn: 0.2-1.5%, and Al≤1.5%; the obtained molten steel is made into a continuous casting billet with a thickness of 200-250 mm, the continuous casting billet has an equiaxed crystal rate≥65% and a narrow cross-section concave depth≤3 mm; the continuous casting billet is heated in a heating furnace, the entering temperature is≥350 ℃, and the soaking temperature is 1000-1150 ℃; during the heating of the continuous casting billet, when the temperature of the continuous casting billet is 350-800 ℃, the heating rate is 5-15 ℃ / min; when the temperature of the continuous casting billet is 800-1150 ℃, the heating rate is≥15 ℃ / min; and the continuous casting billet is subjected to multi-pass rough rolling and multi-pass finish rolling to prepare a hot-rolled plate.

Description

Technical Field

[0001] This application belongs to the field of steel material preparation technology, and relates to a method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate based on the coordinated control of continuous casting and hot rolling, as well as a production method of high-grade non-oriented silicon steel. Background Technology

[0002] Non-oriented silicon steel is a key soft magnetic material for manufacturing motor and transformer cores, and its iron loss and magnetic properties directly affect the power conversion efficiency. With the continuous improvement of global energy efficiency standards, the demand for high-grade (high silicon, high aluminum content) non-oriented silicon steel is increasing. High-grade non-oriented silicon steel is typically hot-rolled in the ferrite region. Its high silicon and aluminum content, while increasing resistivity and reducing iron loss, also significantly increases the material's brittleness, making it more sensitive to defects during hot working.

[0003] Edge quality of hot-rolled sheets, especially edge cracks, is a common technical challenge in the production of high-grade non-oriented silicon steel. Edge cracks not only affect the appearance and yield of hot-rolled coils, but also lead to serious problems such as strip breakage and rib formation during subsequent cold rolling, hindering smooth production and product quality improvement.

[0004] Traditional improvement measures mainly focus on local adjustments within the hot rolling process itself, such as: increasing the slab entry temperature to reduce corner defects; optimizing roll shape and load distribution to control edge waviness; adding edge heaters before finishing rolling to increase edge temperature; and increasing the opening of side guide plates to avoid mechanical scratching. These methods are effective for low- to medium-grade non-oriented silicon steel, but for high-grade products with higher brittleness and poorer deformation coordination, the improvement effect is limited and unstable, and it is difficult to fundamentally eliminate edge cracks.

[0005] Recent research reveals that the root cause of edge cracks in high-grade non-oriented silicon steel during hot rolling can be traced back to the original microstructure of the continuously cast billet and its evolution during the heating process. Therefore, the main problem with existing technologies is that the control approach for edge crack defects in high-grade non-oriented silicon steel remains limited to "post-process remediation" in the hot rolling process, failing to systematically prevent and control the root cause of the defects—abnormal growth of columnar crystals at the edges—from a holistic process perspective, especially at the continuous casting source. This results in a lack of targeted process adjustments and a bottleneck in effectiveness. Summary of the Invention

[0006] To address the aforementioned technical problems, the purpose of this application is to provide a method for edge quality control of high-grade non-oriented silicon steel hot-rolled plates based on the coordinated control of continuous casting and hot rolling, as well as a method for producing high-grade non-oriented silicon steel.

[0007] To achieve the aforementioned objectives, one embodiment of this application provides a method for edge quality control of high-grade non-oriented silicon steel hot-rolled plates. The control method includes the following steps:

[0008] Steelmaking process: Refining steel. The final chemical composition of the molten steel, by mass percentage, includes: C≤0.005%, Si:1.5~4.5%, Mn:0.2~1.5%, Al≤1.5%, S≤0.01%, P≤0.08%, N≤0.01%, O≤0.01%, Cr, Ni and Cu ≤5.0% respectively, Ti, V, Mo and Nb ≤0.1% respectively, and the remainder being Fe and unavoidable inclusions. Continuous casting process: The obtained molten steel is made into a continuous casting billet with a thickness of 200~250mm by continuous casting technology. The equiaxed crystal ratio of the continuous casting billet is ≥65% and the concave depth of the narrow section is ≤3mm. Heating process: The continuously cast billet is heated in a heating furnace with an initial temperature ≥350℃ and a soaking temperature of 1000~1150℃; during the heating of the continuously cast billet, when the temperature of the continuously cast billet is 350~800℃, the heating rate is controlled at 5~15℃ / min; when the temperature of the continuously cast billet is 800~1150℃, the heating rate is controlled at ≥15℃ / min. Hot rolling process: The continuously cast billet is subjected to multiple passes of rough rolling and multiple passes of finish rolling to prepare a hot-rolled plate.

[0009] As a further improvement to one embodiment, the chemical composition of the final molten steel, by mass percentage, includes: C ≤ 0.005%, Si: 1.5~4.5%, Mn: 0.2~1.5%, Al: 0.30~1.5%, Si+Al: 1.7~4.8%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni and Cu ≤ 5.0% respectively, Mo, Nb, V and Ti ≤ 0.1% respectively, with no Sn and Sb or any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%, and the remainder being Fe and unavoidable inclusions; Alternatively, the chemical composition of the final molten steel, by mass percentage, includes: C ≤ 0.005%, Si: 1.5~4.5%, Mn: 0.2~1.5%, Al ≤ 0.0030%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni and Cu ≤ 5.0% respectively, Mo, Nb, V and Ti ≤ 0.1% respectively, with no Sn and Sb or any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%, and the remainder being Fe and unavoidable inclusions; Alternatively, the chemical composition of the final molten steel, by mass percentage, includes: C ≤ 0.005%, Si: 3.2~3.7%, Mn: 0.3~0.8%, Al: 0.70~1.2%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni and Cu ≤ 5.0% respectively, Mo, Nb, V and Ti ≤ 0.1% respectively, with no Sn and Sb or any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%, and the remainder being Fe and unavoidable inclusions.

[0010] As a further improvement to one embodiment, the final molten steel is free of Sn and Sb, or the chemical composition of the final molten steel, by mass percentage, includes either or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%.

[0011] As a further improvement to one implementation method, in the continuous casting process, the casting speed is controlled at 0.80~1.10m / min.

[0012] As a further improvement to one implementation method, the continuous casting process: When the chemical composition of the final molten steel meets the requirement of Si+Al≥3.0% by mass percentage, the casting speed during continuous casting is 0.80~0.90m / min; When the chemical composition of the final molten steel meets the mass percentage requirement of 2.0% < Si + Al < 3.0%, the casting speed during continuous casting is 0.90~1.00 m / min; When the chemical composition of the final molten steel meets the requirement of Si+Al≤2.0% by mass percentage, the casting speed during continuous casting is 1.00~1.10m / min.

[0013] As a further improvement to one implementation method, the continuous casting process: The cooling water flow rate of the narrow face of the crystallizer is controlled at 2.5 L / (mm×min), and the cooling water flow rate of the wide face is controlled at 2.0 L / (mm×min); Electromagnetic stirring is applied in the secondary cooling section with a stirring current of 500~550 A and a stirring frequency of 10~12 Hz.

[0014] As a further improvement to one embodiment, the hot rolling process is as follows: the initial rolling temperature of the first finishing rolling pass is ≥950℃, the final rolling temperature of the last finishing rolling pass is (830~880)±15℃, the total reduction rate of finishing rolling is 90~96%, and the reduction rate of the last finishing rolling pass is 20~25%. After multiple passes of precision rolling, the product is wound at a temperature of (600~650)±15℃.

[0015] As a further improvement to one implementation method, the steelmaking process involves: sequentially desulfurizing molten iron, smelting in a converter, and refining in a vacuum to produce molten steel; wherein, Vacuum refining: During the alloying process, desulfurizing agent is added in two batches, and degassing is carried out for more than 12 minutes under a vacuum degree of less than 2 mbar. The net circulation time is ≥10 minutes. The steel temperature after vacuum refining is controlled at T=(t+50℃)±5℃, where t is the liquidus temperature corresponding to the chemical composition of the final molten steel.

[0016] To achieve the above-mentioned application objectives, one embodiment of this application provides a method for producing high-grade non-oriented silicon steel, characterized in that the production method prepares non-oriented silicon steel finished products by passing hot-rolled plates through a continuous acid rolling process, a hardened plate normalizing process, a single-stand precision cold rolling process, and an annealing process; The hot-rolled plate is prepared by the edge quality control method for high-grade non-oriented silicon steel hot-rolled plate described in any of the preceding embodiments. The thickness of the non-oriented silicon steel finished product is (0.05~0.50)±0.005mm.

[0017] As a further improvement to one implementation method, the pickling and rolling process involves using a multi-stand pickling and rolling mill to pickle the hot-rolled plate and perform multiple passes of continuous cold rolling to obtain a hardened plate; the reduction rate of the first pass of cold rolling is 20-30%, and the reduction amount is ≤0.70mm. Normalizing process of rolled hardened sheet: The obtained rolled hardened sheet is normalized at a normalizing temperature of (850~1000)±10℃ for a normalizing time of 60~100s. Single-stand cold rolling process: 2 to 4 passes of cold rolling are performed using a single-stand cold rolling mill, with a total reduction rate of 40 to 80%. The reduction rate of the first pass of cold rolling is ≥30% and the reduction amount is ≤0.40mm. Annealing process: Annealing temperature is 850~1050℃, annealing time is 40~120s.

[0018] As a further improvement to one implementation method, the normalizing process for rolled hard sheet is as follows: normalizing is carried out in a normalizing furnace with a tension of 8~10 N / mm. 2 After normalization, temperature-controlled cooling is carried out. When the surface temperature of the steel plate is ≥400℃, the cooling rate is 10~15℃ / s, and when the surface temperature of the steel plate is <400℃, the cooling rate is 15~20℃ / s.

[0019] As a further improvement to one implementation method, the single-stand precision cold rolling process: The single-stand rolling mill used is a six-roll single-stand cold rolling mill or a twenty-roll single-stand cold rolling mill; The working roll diameter of the 20-roll single-stand cold rolling mill is 45~65mm. The roughness of the working roll used for the first pass of finishing cold rolling is 2.50±0.5μm, and the roughness of the working roll used for the last pass of finishing cold rolling is 0.50±0.10μm.

[0020] As a further improvement to one implementation method, in the annealing process: the tension inside the annealing furnace is controlled at 1~3 N / mm. 2 After the annealing time is reached, segmented cooling is used. The segmented controlled cooling includes: a cooling rate of 5~10℃ / s when the steel plate surface temperature is >700℃, a cooling rate of 10~15℃ / s when the steel plate surface temperature is 400~700℃, and a cooling rate of 15~20℃ / s when the steel plate surface temperature is <400℃.

[0021] As a further improvement to one embodiment, the thickness of the non-oriented silicon steel finished product is >0.15mm, and the corresponding thicknesses of the hot-rolled plate and the hardened plate are 2.3~3.5mm and 0.4~1.2mm, respectively. In the annealing process: the annealing temperature is T. t1 ±10℃, annealing time 100~120s; T t1 The unit is ℃, and its value is taken from the formula 900+200(11Si-14Mn+21Al). The element symbols in the formula represent the mass percentage of the corresponding element in the continuously cast billet.

[0022] As a further improvement to one embodiment, the thickness of the non-oriented silicon steel finished product is 0.05~0.15mm, and the corresponding thicknesses of the hot-rolled plate and the hardened plate are 1.8~2.3mm and 0.2~0.35mm, respectively. In the annealing process: the annealing temperature is T. t2 ±10℃, annealing time (30~50)s+400h s / mm, where h is the thickness of the cold-rolled sheet in mm; T t2 The unit is ℃, and its value is taken from the formula 820 + 200(11Si - 14Mn + 21Al) + 400h mm. -1 The element symbols in the formula represent the mass percentage of the corresponding element in the continuously cast billet.

[0023] Compared with the prior art, the beneficial effects of this application include: First, this invention breaks through the limitations of traditional approaches that only make local adjustments to the hot rolling process. It innovatively moves the control point forward to the continuous casting source. Through the systematic design of steel composition and continuous casting process (such as controlling the equiaxed crystal ratio ≥65% and the concave depth of narrow cross section ≤3mm), combined with a specific slab heating regime (controlling the furnace temperature and segmented heating rate), it fundamentally inhibits the abnormal growth of columnar crystals at the edge of the slab during subsequent heating. This synergistic control strategy directly addresses the root cause of edge cracking, resulting in stable edge quality and no edge crack defects in the produced hot-rolled plates. It fundamentally solves the key problem restricting the smooth production of high-grade products. The technical effect is clear and significant, providing new theoretical guidance and technical path for the development of production processes for high-grade and even higher-performance silicon steel. It has important industry leadership and technological progress significance. Secondly, the hot-rolled plate obtained by this invention not only eliminates edge cracks, but also has a uniform internal structure and good edge quality. When using it as raw material for subsequent multi-stand acid rolling, it can effectively avoid production accidents such as strip breakage and rib formation caused by edge defects, greatly improve the stability, operating rate and yield of the cold rolling process, and reduce the production risks and costs of the entire process. Third, the hot-rolled plates prepared using the method of this invention retain and optimize their excellent original edge quality and uniform microstructure to the greatest extent possible after undergoing a series of processes, including pickling, hardening, single-stand cold rolling, and annealing. Furthermore, by employing a novel process of pickling-hardening-single-cold rolling-annealing to prepare high-grade non-oriented silicon steel, the hot-rolled plates do not require normalizing or preheating before pickling, resulting in a series of benefits, including but not limited to: reducing the requirements for the rolled pieces during cold rolling, thereby reducing the production difficulty of hot rolling and improving the efficiency of hot rolling and pickling; reducing the requirements for the degree of coordinated deformation of the surface and thickness center of the rolled piece during cold rolling, thereby reducing the equipment requirements for multi-stand pickling mills, enabling rapid continuous cold rolling, greatly improving the production efficiency of cold rolling, and reducing the production difficulty of cold rolling; simultaneously, during pickling, the ends of two or more hot-rolled plates are sequentially welded together to achieve full-length rolling, which not only improves efficiency but also significantly increases the yield. In summary, this not only ensures smooth board production throughout the entire process but also reduces the overall production difficulty and improves overall production efficiency. The resulting high-grade non-oriented silicon steel product not only has lower iron loss and higher magnetic induction, resulting in excellent magnetic properties, but also significantly improved dimensional accuracy, meeting the stringent requirements of high-end motors and transformers for core core materials. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] One embodiment of this application provides a method for edge quality control of hot-rolled high-grade non-oriented silicon steel plates. The control method includes steelmaking, continuous casting, heating, and hot rolling processes. Each process is described in detail below.

[0026] Steelmaking process This process involves refining steel to achieve the target chemical composition. The chemical composition of the molten steel at the end of the steelmaking process is also known as the target chemical composition.

[0027] In this field, the chemical composition of the final molten steel, the chemical composition of the continuously cast billet, and the chemical composition of the non-oriented silicon steel product are basically the same. The chemical composition of the final molten steel in the steelmaking process can be sampled and tested to characterize the chemical composition of the continuously cast billet, and also to characterize the chemical composition of the non-oriented silicon steel.

[0028] Incidentally, in this application, the molten steel, continuously cast billets, or final non-oriented silicon steel products at the end of the steelmaking process can be sampled in accordance with GB / T 20066-2006 "Sampling and Sample Preparation Methods for Determination of Chemical Composition of Steel and Iron", and the chemical composition of the molten steel, continuously cast billets, or final non-oriented silicon steel products can be tested in accordance with GB / T 223 series "Methods for Chemical Analysis of Iron and Steel and Alloys".

[0029] The chemical composition of the final molten steel, by mass percentage, includes: C ≤ 0.005%, Si: 1.5~4.5%, Mn: 0.2~1.5%, Al ≤ 1.5%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni and Cu ≤ 5.0% respectively, Ti, V, Mo and Nb ≤ 0.1% respectively, and the remainder being Fe and unavoidable inclusions.

[0030] The following section provides a detailed explanation of the role and mechanism of each chemical element in the chemical composition.

[0031] C: In non-oriented silicon steel, carbon (C) is a harmful element. Increased C content results in finer grains, higher iron loss, and lower magnetic induction in the finished product. High C content can also cause magnetic aging problems; therefore, lower C content is better. In this application, the C content of the non-oriented silicon steel is controlled at C ≤ 0.005%. Preferably, in some embodiments, C ≤ 0.0030%. More preferably, in some embodiments, C ≤ 0.0025%.

[0032] Si is an effective additive element for improving resistivity and reducing iron loss. As the Si content increases, the strength of the steel plate increases, the resistance to cold rolling deformation increases, the brittleness increases, and the strip is more prone to breakage during the cold rolling process. In this application, the Si content of the non-oriented silicon steel is controlled at 1.5~4.5%.

[0033] Mn: Adding an appropriate amount of Mn can suppress the hot brittleness caused by S and reduce iron loss to a certain extent; however, if the Mn content is too high, it will lead to an increase in production costs. In this application, the Mn content is controlled at 0.2~1.5%.

[0034] Al (Al) is an effective additive element for improving resistivity and reducing iron loss. However, as the Al content increases, the strength of the steel plate increases, the resistance to cold rolling deformation increases, the brittleness increases, and the strip is more prone to breakage during cold rolling. In this application, to ensure magnetic properties and smooth plate passage, the Al content is controlled at ≤1.5%. Studies have found that, based on the Al ≤1.5% composition design, when 0.003% < Al < 0.30%, AlN precipitates are more likely to form in the steel, thus affecting grain growth during normalization and annealing of hardened plates. In view of this research result, in some embodiments of this application, Al is preferably controlled at ≤0.0030%, for example, aluminum alloy may not be added in the steelmaking process. In other embodiments, the Al content is preferably controlled in the range of 0.30~1.5%.

[0035] S: In non-oriented silicon steel, sulfur (S) is a harmful element. Increased S content leads to higher iron loss and lower magnetic induction. When S reacts with Mn to form fine MnS, it strongly hinders grain growth during annealing. At any Mn content, iron loss increases with increasing S content. In this application, to ensure magnetic properties, S is controlled to be ≤0.01%. Preferably, in one embodiment, the S content is controlled to be 0.0030% or less. More preferably, in yet another embodiment, the S content can be further controlled to ≤0.0015%.

[0036] P: While it has little effect on magnetism, increasing the P content can effectively improve the strength of the steel plate and enhance its punching performance. However, for the high-grade non-oriented silicon steel of this application, due to the high Si and Mn content, the steel plate itself already has high strength, so there is no need to specifically add P. At the same time, it is not necessary to control P too strictly, to avoid increased steelmaking difficulty due to P removal and to avoid affecting desulfurization production. In this application, the P content is controlled at P≤0.08%. Preferably, in some embodiments, P≤0.03%.

[0037] Nitrogen (N): In non-oriented silicon steel, nitrogen readily forms fine AlN precipitates with Al, inhibiting grain growth and thus requiring strict control. In this application, the nitrogen content is controlled at ≤0.01%. Preferably, in some embodiments, the nitrogen content is further controlled to ≤0.003%.

[0038] O: In non-oriented silicon steel, O readily forms oxide inclusions such as Al2O3 and SiO2 with elements like Al and Si, hindering grain growth during annealing and thus requiring strict control. In this application, the O content is controlled at ≤0.01%. Preferably, in some embodiments, O ≤0.0030%.

[0039] Cr, Ni, Cu: In non-oriented silicon steel, Cr, Ni, and Cu are all non-essential elements, and are only added when high strength is required. Therefore, in this application, Cr, Ni, and Cu are each controlled to ≤5.0%. Preferably, in some embodiments where high strength is not required, the content of any one or more of Cr≤0.03%, Ni≤0.03%, and Cu≤0.03% can be further controlled. More preferably, in some embodiments, to avoid the deteriorating effect of the superposition of Cr, Ni, and Cu on magnetic properties, the content of Cr+Ni+Cu can be further controlled to ≤0.06%.

[0040] Nb and V: As carbide and nitride forming elements, their fine precipitates can hinder the growth of finished grains during annealing. Although this increases strength, it affects magnetic properties. In this application, the content of Nb and V is controlled to be ≤0.1%. Preferably, in some embodiments where high strength is not pursued, the chemical composition of the non-oriented silicon steel also satisfies either or both of Nb≤0.004% and V≤0.004%.

[0041] Mo: In non-oriented silicon steel, Mo is a non-essential element, only needed when its mechanical properties at high temperatures are simultaneously desired. However, excessive Mo content can deteriorate magnetic properties. In this application, the Mo content is controlled at ≤0.1%. Preferably, in some embodiments, to avoid significant grain refinement and deterioration of magnetic properties due to increased Mo content, the Mo content is controlled at 0.005% or less. More preferably, Mo ≤0.004%.

[0042] Ti: As a carbide and nitride forming element in steel, its fine precipitates can hinder the growth of finished grains during annealing. Therefore, in this application, the Ti content in the non-oriented silicon steel is ≤0.1%. Preferably, in some embodiments, Ti is ≤0.005%. More preferably, Ti is ≤0.0015%.

[0043] More preferably, in some embodiments, in order to avoid the deterioration effect of the superposition of Nb, V, Mo and Ti on the magnetic properties, Nb+V+Ti+Mo≤0.009%.

[0044] Furthermore, in some embodiments, Sn and Sb are not intentionally added during the steelmaking process, meaning the final molten steel contains no Sn and Sb (or contains very small amounts, approximately zero). In other embodiments, the final molten steel may further contain either or both of Sn and Sb, for example: the Sn content is controlled within the range of 0.01~0.15%, that is, 0.01~0.15% Sn replaces the original iron element to further improve magnetic properties; or, the Sb content is controlled within the range of 0.01~0.15%, that is, 0.01~0.15% Sb replaces the original iron element to further improve magnetic properties; or, it contains both Sn and Sb, and the total Sn+Sb content is controlled within the range of 0.01~0.15%.

[0045] Within the design framework of the above chemical composition, in some embodiments, for example, when the thickness of the non-oriented silicon steel product is >0.15mm, the chemical composition, by mass percentage, can satisfy: Si: 1.5~4.5%, Mn: 0.2~1.5%, Al: 0.30~1.5%, Si+Al: 1.7~4.8%; or it can satisfy: Si: 1.5~4.5%, Mn: 0.2~1.5%, Al≤0.0030%.

[0046] Furthermore, within the design framework of the above chemical composition, in some embodiments, for example, when the thickness of the non-oriented silicon steel product is ≤0.15mm, the chemical composition by mass percentage can meet the following: Si: 3.2~3.7%, Mn: 0.3~0.8%, Al: 0.70~1.2%.

[0047] Next, preferably, the steelmaking process includes sequential stages such as hot metal desulfurization, converter smelting, and vacuum refining.

[0048] In the vacuum refining stage: during the alloying process, the desulfurizing agent is added in two batches, and the degassing is carried out for more than 12 minutes under a vacuum degree of less than 2 mbar, with a net circulation time of ≥10 minutes, and then the final molten steel that meets the above chemical composition is obtained; the vacuum refining tapping temperature is controlled at T=(t+50℃)±5℃, where t is the liquidus temperature corresponding to the chemical composition of the final molten steel.

[0049] The phrase "adding desulfurizing agent in two batches during the alloying process" could be, for example, adding the first batch of desulfurizing agent at a ratio of 3 kg per ton of molten steel at the 3rd minute of the alloying process, and adding the second batch of desulfurizing agent at a ratio of 5 kg per ton of molten steel at the 8th minute of the alloying process.

[0050] In one embodiment, the hot metal desulfurization stage includes: deep desulfurizing the blast furnace hot metal to obtain hot metal with the following chemical composition by mass percentage: C ≥ 3.5%, S ≤ 0.0010%, Si: 0.20~0.80%, Al ≤ 0.0030%, Mn ≤ 0.50%, P ≤ 0.15%, Nb ≤ 0.003%, V ≤ 0.03%, Ti ≤ 0.10%, Cr ≤ 0.02%, Ni ≤ 0.02%, Cu ≤ 0.02%, and the temperature of the hot metal after desulfurization is ≥ 1320℃.

[0051] The converter steelmaking stage includes: using desulfurized molten iron and scrap steel for converter smelting; the final converter concentration is C: 0.020~0.050%, S≤0.0015%, P≤0.015%; the final converter slag basicity is controlled at 3.5~4.5, and MgO is controlled at 8.0~10.0%; the final converter steel temperature is 1670±15℃.

[0052] In the steelmaking process, in addition to hot metal desulfurization, converter smelting, and vacuum refining, other smelting stages may also be included, which can be implemented according to any feasible steelmaking technology in the field to produce the final steel of this application.

[0053] Continuous casting process In this continuous casting process, the molten steel is made into a continuous casting billet with a thickness of 200~250mm using continuous casting technology. The equiaxed crystal ratio of the continuous casting billet is ≥65%, and the narrow cross-section concave depth is ≤3mm.

[0054] This approach directly and significantly improves the inherent quality of the continuously cast billet by reducing the original proportion of columnar crystals prone to abnormal growth (≥65% equiaxed crystal ratio) and mitigating edge stress concentration (≤3mm concave depth). It avoids internal stresses generated by the billet's microstructure and shape, creating stable conditions for subsequent heating processes from both microstructure and stress perspectives. This effectively suppresses abnormal growth of columnar crystals at the billet edge during heating, fundamentally solving the key problem of edge cracking caused by inconsistent grain size deformation during hot rolling. This lays a decisive foundation for obtaining high-quality, defect-free hot-rolled plates. Furthermore, it reduces the occurrence of cracks leading to strip breakage during subsequent rolling processes (including hot rolling, pickling continuous rolling, and precision cold rolling), further ensuring smooth plate production throughout the entire process.

[0055] The aforementioned narrow-section concave depth refers to the maximum depth of the narrow face (i.e., the thickness side) of the continuously cast billet that is concave inward.

[0056] In this application, GB / T 24178-2009 "Method for Low Magnification Evaluation of Solidification Structure of Continuous Casting Billet" can be used to sample the continuous casting billet and test the equiaxed crystal ratio and narrow section concave depth of the continuous casting billet.

[0057] Preferably, the casting speed during continuous casting is controlled at 0.80~1.10m / min, which can achieve an equiaxed crystal ratio of ≥65% and a narrow cross-section concave depth of ≤3mm for the continuously cast billet.

[0058] In some embodiments, the casting speed during continuous casting can be precisely controlled based on the chemical composition of the final molten steel. For example, when the chemical composition of the final molten steel, by mass percentage, satisfies Si+Al≥3.0%, the casting speed during continuous casting is 0.80~0.90 m / min; when the chemical composition of the final molten steel, by mass percentage, satisfies 2.0%<Si+Al<3.0%, the casting speed during continuous casting is 0.90~1.00 m / min; when the chemical composition of the final molten steel, by mass percentage, satisfies Si+Al≤2.0%, the casting speed during continuous casting is 1.00~1.10 m / min.

[0059] Preferably, in this continuous casting process, the cooling water flow rate of the narrow face of the crystallizer is controlled at 2.5 L / (mm×min), and the cooling water flow rate of the wide face is controlled at 2.0 L / (mm×min).

[0060] Furthermore, electromagnetic stirring is applied in the second cooling section, with a stirring current of 500~550 A and a stirring frequency of 10~12 Hz.

[0061] In addition, the transfer time between tapping steel and casting in the steelmaking process is controlled to be 10-15 minutes.

[0062] Furthermore, in the continuous casting process, the tundish temperature T = (t + 10℃) ± 5℃, and the superheat is 5~15℃. Where t is the liquidus temperature corresponding to the chemical composition of the final molten steel.

[0063] The inlet water temperature of the crystallizer is preferably controlled at 30-35℃.

[0064] Optionally, after the continuously cast billet comes off the production line, it is placed in a heat-insulating pit with heating function for heat preservation to ensure that the continuously cast billet is maintained at a temperature of 400~900℃ for 2~24 hours.

[0065] Heating process In this heating process, the continuously cast billet is heated in a heating furnace.

[0066] The continuous casting billet temperature entering the furnace is ≥350℃. In some embodiments, the continuous casting billet temperature entering the furnace is preferably controlled at ≥450℃.

[0067] The heat spreader temperature is 1000~1150℃. Such a heat spreader temperature can lay the foundation for subsequent processes.

[0068] Preferably, for non-oriented silicon steel products with a thickness > 0.15 mm and ≤ 0.50 mm, the heat soaking temperature can be 1080~1150℃; for non-oriented silicon steel products with a thickness of 0.05~0.15 mm, the heat soaking temperature can be 1000~1140℃.

[0069] Furthermore, during the heating of the continuously cast billet, when the billet temperature is between 350 and 800°C, the heating rate is controlled at 5 to 15°C / min; when the billet temperature is between 800 and 1150°C, the heating rate is controlled at ≥15°C / min. This prevents abnormal growth of columnar crystals inside the billet, thus avoiding subsequent edge cracks or band breakage caused by columnar crystals and increasing the probability of successful production.

[0070] When the chemical composition of the continuously cast billet, by mass percentage, satisfies Si+Al≥3.0%, and the heating rate is controlled at 5~10℃ / min when the billet temperature is between 350~800℃ during the heating process; conversely, when the chemical composition of the continuously cast billet, by mass percentage, satisfies Si+Al<3.0%, and the heating rate is controlled at 10~15℃ / min when the billet temperature is between 350~800℃ during the heating process, precise control of the heating rate can greatly prevent abnormal growth of columnar crystals inside the continuously cast billet, thus significantly increasing the probability of successful production.

[0071] In some embodiments, during the heating process: the steel plate is kept at a uniform heating temperature for 40-60 minutes.

[0072] Hot rolling process In this process, after the continuously cast billet exits the heating furnace, it undergoes multiple rough rolling passes to prepare an intermediate billet, and then undergoes multiple finish rolling passes to prepare a hot-rolled plate.

[0073] In some embodiments, the roughing rolling process may involve five to nine passes, such as six passes; the finishing rolling process may involve five to nine passes, such as seven passes. However, it is not limited to these.

[0074] The initial rolling temperature of the first finishing rolling pass is ≥950℃, and the final rolling temperature of the last finishing rolling pass is (830~880)±15℃.

[0075] In some embodiments, the final rolling temperature of the last finishing pass can be specifically controlled at any value among 815℃, 820℃, 825℃, 830℃, 835℃, 840℃, 845℃, 850℃, 855℃, 860℃, 865℃, 870℃, 875℃, 880℃, 885℃, 890℃, and 895℃, or other values ​​within the range of 815℃ to 895℃.

[0076] Furthermore, in the hot rolling process: the total reduction rate of finishing rolling is 90~96%, and the reduction rate of the final finishing rolling is 20~25%. For example, the thickness of the intermediate billet is 30~50mm, and the thickness of the hot-rolled plate is 1.8~3.5mm.

[0077] More specifically, for example, for non-oriented silicon steel finished products with a thickness of 0.15 mm or more but not more than 0.50 mm, the corresponding total reduction rate of finishing rolling is 90-96%, and the thickness of intermediate billet and hot-rolled plate is 38-50 mm and 2.3-3.5 mm, respectively; for another example, for non-oriented silicon steel finished products with a thickness of 0.05-0.15 mm, the corresponding total reduction rate of finishing rolling is 93-95%, and the thickness of intermediate billet and hot-rolled plate is 30-40 mm and 1.8-2.3 mm, respectively.

[0078] Thus, controlling the total reduction rate of finishing rolling and the reduction rate of the final finishing rolling can improve the shape of hot-rolled plates. For example, after subsequent leveling, the flatness of hot-rolled coils can reach ≤10mm within a length range of 1000mm, which can further improve the stability and production rate of subsequent cold rolling.

[0079] In this application, the unevenness can be determined by sampling and testing the steel plate in accordance with GB / T 709-2019 "Dimensions, Shapes, Weights and Permissible Deviations of Hot-Rolled Steel Plates and Strips" to obtain the range of unevenness.

[0080] Preferably, during finishing rolling, the work rolls of the finishing mill stand are asynchronously shifted, and the total axial movement range within the rolling cycle is not less than 100 mm. That is, the total range of forward and reverse axial movement of the work rolls is ≥100 mm. This can reduce the wear difference of the work rolls in the finishing mill stand.

[0081] In addition, after the hot-rolled plate exits the finishing mill stand, it can be cooled by controlled temperature through air cooling or water cooling, such as laminar flow cooling, before being coiled. Specific cooling technologies can be implemented in any feasible manner in the art, and this application does not limit them.

[0082] The winding temperature is (600~650)±15℃. In this way, on the one hand, by combining the comprehensive control of various temperatures in the finishing rolling process and the winding temperature, it can be ensured that the internal structure of the hot-rolled coil obtained in the winding process is a uniform hot-rolled deformed fiber structure, and on the other hand, the edge quality of the hot-rolled coil can also be guaranteed.

[0083] The winding temperature can be controlled at any value among 585℃, 590℃, 595℃, 600℃, 605℃, 610℃, 615℃, 620℃, 625℃, 630℃, 635℃, 640℃, 645℃, 650℃, 655℃, 660℃, and 665℃, or other values ​​within the range of 585℃ to 665℃.

[0084] In summary, this invention breaks through the limitations of traditional approaches that only make local adjustments to the hot rolling process. It innovatively moves the control point forward to the continuous casting source. Through the systematic design of steel composition and continuous casting process (such as controlling the equiaxed crystal ratio ≥65% and the concave depth of narrow cross-section ≤3mm), combined with a specific slab heating regime (controlling the furnace temperature and segmented heating rate), it fundamentally inhibits the abnormal growth of columnar crystals at the edge of the slab during subsequent heating. This synergistic control strategy directly addresses the root cause of edge cracking, resulting in hot-rolled plates with stable edge quality and no edge crack defects. It fundamentally solves the key problem restricting the smooth production of high-grade products. The technical effect is clear and significant, providing new theoretical guidance and technical path for the development of production processes for high-grade and even higher-performance silicon steel, and has important industry leadership and technological progress significance.

[0085] In addition, the hot-rolled plate obtained by this invention not only eliminates edge cracks, but also has a uniform internal structure and good edge quality. When using it as raw material for subsequent multi-stand acid rolling, it can effectively avoid production accidents such as strip breakage and rib formation caused by edge defects, greatly improve the stability, operating rate and yield of the cold rolling process, and reduce the production risks and costs of the entire process.

[0086] Next, an embodiment of this application also provides a method for producing high-grade non-oriented silicon steel. The production method includes the control method described above, that is, it prepares hot-rolled plates through steelmaking, continuous casting, heating and hot rolling processes. Furthermore, the production method also includes an acid continuous rolling process, a hardened plate normalizing process, a single-stand precision cold rolling process and an annealing process to prepare the hot-rolled plates into finished non-oriented silicon steel products.

[0087] The following sections describe the acid rolling process, the normalizing process for hardened plates, the single-stand precision cold rolling process, and the annealing process.

[0088] [Acid-rolling process] In the pickling and rolling process: the hot-rolled plate after being coiled is leveled, and then pickled and cold-rolled in multiple passes using a multi-stand pickling and rolling mill to obtain a hardened plate.

[0089] As can be seen, in the production method of this application, there is no need to normalize the hot-rolled plate before pickling and multi-pass cold rolling. The hot-rolled deformed fiber structure is still retained at the beginning of cold rolling, thereby ensuring the cold-rollability of the steel plate and reducing the difficulty of cold rolling. There is no need to preheat before cold rolling as in the prior art. At the same time, the use of a multi-stand pickling and rolling mill for multi-pass cold rolling results in high production efficiency and low production cost, and has the advantages of saving energy and resources, meeting the high requirements of environmental protection.

[0090] Furthermore, in the pickling and rolling process: the reduction rate of the first cold rolling pass is 20-30%, and the reduction amount is ≤0.70mm. Common technologies require a large reduction in the first pass to produce high-grade non-oriented silicon steel, which makes hot rolling and cold rolling difficult. However, the present application can achieve a small reduction in the first cold rolling pass, thereby reducing the equipment requirements for multi-stand pickling and rolling mills and reducing the thickness requirements for hot-rolled plates, greatly reducing production difficulty and improving production efficiency.

[0091] Furthermore, in the pickling and rolling process, the reduction rate of the final cold rolling pass is 15-25%. This not only reduces production difficulty but also facilitates control over the accuracy of sheet shape and thickness.

[0092] Preferably, in the acid continuous rolling process, a micro-edge wavy rolling mode can be adopted to avoid the edge of the rolled piece being in a tensile state, thereby avoiding tension concentration at the edge and causing strip breakage. This can further ensure the smooth progress of multi-pass continuous cold rolling in a multi-stand acid continuous rolling mill.

[0093] The aforementioned micro-edge wavy rolling mode can be, for example, during multi-pass cold rolling, controlling the bending force of the work rolls of a multi-stand acid continuous rolling mill within the range of 50kN to 150kN, so that the edge of the resulting hardened plate produces a controllable edge wavy with a height of 1.0~3.0mm.

[0094] The height of controllable edge waviness refers to the height of the edge waviness that is artificially formed and allowed to exist during the cold rolling process. In this application, the height of controllable edge waviness is: the vertical distance from the apex of the edge crest to the plane of the platform when the rolled hard plate is freely laid flat on a horizontal platform under no tension, and this distance is actively controlled within the range of 1.0 mm to 3.0 mm.

[0095] Furthermore, the multi-stand pickling and rolling mill used is any one of a six-roll five-stand pickling and rolling mill, a six-roll six-stand pickling and rolling mill, or an eighteen-roll six-stand pickling and rolling mill.

[0096] In addition, during the pickling and rolling process, the number of cold rolling passes can be four to seven. For example, five passes.

[0097] Furthermore, in some embodiments, the specific pickling process in the pickling continuous rolling process can be implemented using any feasible technology in the art, and this application does not limit it.

[0098] In addition, the thickness of the rolled hard plate can be 0.2~1.2mm. For example, for non-oriented silicon steel products with a thickness of 0.05~0.15mm, the corresponding thickness of the rolled hard plate is 0.2~0.35mm; while for non-oriented silicon steel products with a thickness of more than 0.15mm, the corresponding thickness of the rolled hard plate is 0.4~1.2mm.

[0099] [Routing process for hardened sheet metal] In the normalizing process of the rolled hard plate: the obtained rolled hard plate is normalized at a temperature of (850~1000)±10℃.

[0100] Thus, through the preceding hot rolling and acid continuous rolling processes, deformed fibrous ferrite structure is formed in the steel plate. On this basis, the normalizing process of hardened plate allows the deformed fibrous ferrite to undergo complete recrystallization, achieving coarsening and homogenization of the structure. This creates conditions for controlling the grains and texture in the subsequent annealing process, thereby ensuring excellent magnetic properties and creating conditions for the subsequent single-stand precision cold rolling. This makes it possible to successfully produce plates using the low-difficulty production technology of this application.

[0101] Furthermore, the microstructure of hardened rolled steel is a deformed fibrous structure, which is thin and has a bright surface. Therefore, the normalization process of hardened rolled steel is less difficult, and pickling is not required after normalization. In addition, due to the thinness of hardened rolled steel, the difficulty of subsequent precision cold rolling is significantly reduced. Therefore, for high-grade non-oriented silicon steel of the same composition, the normalization temperature of hardened rolled steel can be higher than that of hot-rolled steel in common technologies. This can relatively increase the size of recrystallized grains after normalization, promote grain growth in subsequent annealing processes, and further improve the magnetic properties of the finished product, such as reducing iron loss.

[0102] Next, preferably, in the normalizing process of the rolled hard sheet, the normalizing time is 60~100s. In this way, by controlling the normalizing temperature and the normalizing time, the deformed fiber ferrite undergoes complete recrystallization, achieving coarsening and homogenization of the microstructure. For example, the recrystallized grain size after normalizing is 30~100μm, creating conditions for obtaining excellent magnetic properties and reducing the difficulty of subsequent production.

[0103] Furthermore, in the normalizing process of the rolled sheet: the rolled sheet is normalized in a weakly reducing atmosphere, thereby avoiding surface oxidation caused by normalizing. The weakly reducing atmosphere can be a mixture of H2 and N2, in which the volume percentage of H2 is 15-25%. Of course, this application is not limited to this.

[0104] Furthermore, preferably, in the normalizing process of the rolled hard sheet: normalizing is carried out in a normalizing furnace, and the tension inside the normalizing furnace is 8~10 N / mm. 2 Thus, by adopting a high-tension mode, the precipitation and growth of MnS and AlN can be promoted, which is also beneficial to improving the plate shape quality.

[0105] In the normalizing process of rolled steel plates: after normalizing, temperature-controlled cooling is performed. When the surface temperature of the steel plate is ≥400℃, the cooling rate is 10~15℃ / s, and when the surface temperature of the steel plate is <400℃, the cooling rate is 15~20℃ / s. In this way, by controlling the cooling rate in stages, combined with the high-tension mode, the grain and texture in the microstructure can be optimized, and the plate shape quality can be further improved.

[0106] Single-stand precision cold rolling process In the single-stand precision cold rolling process: a single-stand rolling mill is used to perform precision cold rolling on the normalized steel plate to obtain a precision cold-rolled plate with a thickness of (0.05~0.50)±0.005mm.

[0107] As mentioned earlier, based on the normalizing process of hardened plates, the single-stand precision cold rolling process allows the entire application to roll the continuously cast billet to the required thickness (i.e., the thickness of the non-oriented silicon steel finished product) at an extremely high production rate. The reason for this is that before precision cold rolling, the thickness of the rolled piece is already very thin, and the microstructure of the rolled piece is a normalized recrystallized structure with low deformation resistance and a bright surface, thus making precision cold rolling less difficult.

[0108] In addition, the raw material for the single-stand cold rolling process is normalized hardened plate, which has a significantly reduced strength compared to the unnormalized hardened plate. At the same time, the cold rolling process uses a single-stand mill, which greatly reduces the diameter of the work rolls and the contact area between the rolls and the workpiece compared to a multi-stand continuous acid rolling mill. This significantly reduces the rolling force, which not only ensures high-efficiency and smooth plate passage, but also improves the thickness control accuracy of the non-oriented silicon steel finished product and improves the control level of plate variation, that is, reduces plate variation and improves the uniformity of the plate.

[0109] Next, in the single-stand precision cold rolling process: multiple passes of precision cold rolling, such as 2 to 4 passes, are performed to obtain a precision cold-rolled sheet of the desired thickness. The thickness of the resulting precision cold-rolled sheet is approximately equivalent to the thickness of the finished non-oriented silicon steel product. It is evident that the single-stand precision cold rolling process involves fewer passes, significantly improving production efficiency and reducing production difficulty, while also ensuring the accuracy of the finished product's thickness.

[0110] Preferably, in the single-stand precision cold rolling process, the total reduction rate is 40-80%.

[0111] Research has shown that in single-stand precision cold rolling, if the total reduction rate is too high, it will lead to more nucleation sites in the subsequent annealing process, making grain growth difficult; while if the total reduction rate is too low, the deformation storage energy will be small, affecting grain growth. Controlling the total reduction rate between 40% and 80% can achieve dual control over the number of nucleation sites and deformation storage energy, thereby ensuring the grain size and microstructure in the subsequent annealing process (e.g., increased recrystallized grain size and reduced unfavorable textures after annealing), thus ensuring the magnetic properties of the final product, which has lower iron loss and higher magnetic induction intensity compared to existing products with the same composition.

[0112] Furthermore, preferably, in the single-stand precision cold rolling process: the reduction rate of the first precision cold rolling is ≥30%.

[0113] Furthermore, in the single-stand precision cold rolling process: the reduction of the first precision cold rolling pass is ≤0.40mm.

[0114] Preferably, in the single-stand precision cold rolling process: the rolling force of each pass is ≤6000kN, and the rolling force is adjusted according to the real-time monitored steel plate thickness to ensure that the steel plate thickness fluctuation is ≤±3μm. Thus, by controlling the range of rolling force and adjusting the rolling force in a closed-loop thickness control manner, precise control of the thickness of the precision cold-rolled plate is achieved, avoiding drastic fluctuations in the longitudinal direction of the steel plate thickness.

[0115] Further, optionally, the single-stand rolling mill may specifically be a six-roll single-stand cold rolling mill or a twenty-roll single-stand cold rolling mill.

[0116] The preferred mill is a 20-roll single-stand cold rolling mill with a work roll diameter of 45~65mm. The roughness of the work roll used for the first pass of finishing cold rolling is 2.50±0.5μm, and the roughness of the work roll used for the last pass of finishing cold rolling is 0.50±0.10μm.

[0117] Furthermore, in the production method of this application, before the single-stand precision cold rolling process, that is, before precision cold rolling, there is no need to preheat the normalized steel plate, so that precision cold rolling can be carried out efficiently and stably.

[0118] Annealing process In the annealing process: the cold-rolled steel sheet is annealed in an annealing furnace at a temperature of 850~1050℃ for 40~120s. After that, segmented controlled cooling is used to obtain the non-oriented silicon steel finished product.

[0119] Thus, through the annealing process, grains can grow smoothly and achieve complete recrystallization, greatly improving the magnetic properties of the finished product without the need for normalization before the acid rolling process.

[0120] Next, in the annealing process: continuous annealing is carried out in an annealing furnace under a weakly reducing atmosphere to reduce surface oxidation caused by annealing. Here, the weakly reducing atmosphere can be a mixture of H2 and N2, in which the volume percentage of H2 is 15-25%. Of course, this application is not limited to this.

[0121] Preferably, in some embodiments, during the annealing process, the tension inside the annealing furnace is controlled at 1~3 N / mm. 2 Therefore, by using a micro-tension mode in the annealing furnace, the precipitation of dissolved MnS and AlN can be avoided, thus preventing the formation of fine precipitates and further improving the magnetic properties of the finished product.

[0122] Furthermore, the segmented controlled cooling includes: a cooling rate of 5~10℃ / s when the steel plate surface temperature is >700℃, a cooling rate of 10~15℃ / s when the steel plate surface temperature is 400~700℃, and a cooling rate of 15~20℃ / s when the steel plate surface temperature is <400℃.

[0123] In this way, by controlling the cooling process, the microstructure and grain size of the steel plate can be further optimized. This not only ensures the magnetic properties of the steel plate but also avoids internal stress, thus guaranteeing the dimensional accuracy and shape quality of the finished steel plate.

[0124] Preferably, in some embodiments, for non-oriented silicon steel products with a thickness of 0.15~0.50mm, but not 0.15mm, the annealing temperature can be precisely controlled in conjunction with the chemical composition. For example, the annealing temperature is T. t1 ±10℃, T t1 The unit is ℃, and its value is taken from the formula 900+200(11Si-14Mn+21Al). The element symbols in the formula represent the mass percentage of the corresponding element in the continuously cast billet. For example, Si is substituted into the mass percentage of Si in the continuously cast billet. In this way, the microstructure can be further optimized and the magnetic properties of the finished steel plate can be improved.

[0125] Preferably, in some embodiments, for example for extremely thin non-oriented silicon steel products with a thickness of 0.05~0.15mm, the annealing process involves controlling the annealing temperature at T. t2 ±10℃, annealing time (30~50)s+400h s / mm, where h is the thickness of the cold-rolled sheet in mm; T t2 The unit is ℃, and its value is taken from the formula 820 + 200(11Si - 14Mn + 21Al) + 400h mm. -1 In the formula, the element symbols represent the mass percentage of the corresponding element in the continuously cast billet, and h is the thickness of the cold-rolled steel sheet in mm. This ensures that for extremely thin products, the non-oriented silicon steel product possesses both excellent magnetic properties and machinability. For example, the recrystallized grain size is 500h~1000h μm / mm, h is the thickness of the cold-rolled steel sheet in mm, and the average number of grain layers in the thickness direction of the steel sheet does not exceed 2 layers, for example, 1~2 grain layers.

[0126] In this application, the annealed steel sheet can be sampled and tested in accordance with GB / T4335-2013 "Determination of Ferrite Grain Size of Cold-Rolled Low-Carbon Steel Sheet" to obtain the recrystallized grain size of the annealed steel sheet.

[0127] Of course, after the annealing process of this application, coating, finishing and other processes can also be carried out. These are all feasible technologies of this application and are not the inventive points of this application, so they will not be introduced further.

[0128] In this application, the thickness of the non-oriented silicon steel product prepared by the production method is (0.05~0.50)±0.005mm, for example, thicknesses of 0.05mm, 0.10mm, 0.15mm, 0.20mm, 0.25mm, 0.27mm, 0.30mm, 0.35mm, 0.50mm, etc.

[0129] In some embodiments, the longitudinal thickness fluctuation of the finished non-oriented silicon steel product is ≤ ±3 μm and / or the transverse thickness difference is ≤ 5 μm. In this application, the longitudinal thickness fluctuation and transverse thickness difference can be obtained by sampling and measuring the non-oriented silicon steel according to GB / T 708-2019 "Dimensions, Shapes, Weights and Permissible Deviations of Cold-Rolled Steel Sheets and Strips".

[0130] In addition, the non-oriented silicon steel product also has excellent magnetic properties.

[0131] For example, in some embodiments, the thickness of the non-oriented silicon steel is 0.50 mm, and its iron loss P 1.5 / 50 ≤3.6W / kg, magnetic induction intensity B 5000 ≥1.65T.

[0132] In some embodiments, the thickness of the non-oriented silicon steel is 0.35 mm, and its iron loss P 1.5 / 50 ≤3.0 W / kg and / or P 1.0 / 400 ≤18.5W / kg, magnetic induction intensity B 5000 ≥1.65T.

[0133] In some embodiments, the thickness of the non-oriented silicon steel is 0.20~0.30mm, and its iron loss P 1.0 / 400 ≤14.5W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0134] In some embodiments, the thickness of the non-oriented silicon steel is 0.05~0.15mm, and its iron loss P 1.0 / 400 ≤9.5W / kg, iron loss P 0.5 / 1000 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0135] In this application, GB / T 3655-2022 "Method for measuring the magnetic properties of electrical steel strips (sheets) using Epstein squares" can be used to sample and test the magnetic properties (including iron loss and magnetic induction intensity) of non-oriented silicon steel.

[0136] The production method described in this application, through the innovative process reengineering of "hot-rolled plate acid rolling → hardened plate normalizing → single-stand precision cold rolling," combined with specific process parameter control, enables the present invention to simultaneously achieve the dual objectives of "stable and smooth cold rolling process" and "excellent magnetic properties of finished product," which are difficult to achieve in traditional processes, when producing high-grade non-oriented silicon steel. Furthermore: On the one hand, by eliminating the normalizing process before cold rolling of hot-rolled plates and directly performing pickling and continuous rolling on hot-rolled plates, the problem of rapid deterioration of plate plasticity caused by high-temperature normalizing in traditional processes is effectively avoided. This allows for a mild rolling mode with a moderate reduction rate (20~30%) and a limited reduction amount (≤0.70mm) to be used in the first pass of pickling and continuous rolling, replacing the "high reduction rate" rolling that was forced to be used in the traditional process to overcome low plasticity. This significantly reduces the risk of strip breakage and edge cracking, laying the foundation for the stable and efficient operation of subsequent processes. On the other hand, because the raw material has good plasticity before cold rolling, the traditional processes of "pickled normalized plate" and "preheating before cold rolling" are not required, which shortens the process flow and reduces energy consumption and equipment investment. Moreover, due to the improved rollability of pickling and rolling, thicker hot-rolled plates can be used as raw materials, which reduces the rolling difficulty and load of the hot rolling process, which is conducive to improving the hot rolling yield, output and thickness control level, thereby bringing about an overall improvement in production efficiency. On the other hand, by controlling the temperature and segmented cooling during the annealing process, the finished product is ensured to have a fully recrystallized optimized structure and ideal magnetic properties (high magnetic induction and low iron loss), while avoiding the problem of poor plate shape caused by uneven internal stress during the cooling process.

[0137] From another perspective, compared to existing technologies for high-grade non-oriented silicon steel, there is no need to normalize the hot-rolled plate or preheat it before cold rolling, which reduces the difficulty of the entire production process, improves production efficiency, and at the same time reduces the strict upper limit of Si content (or the total content of Si and Al), which can give full play to the performance-enhancing effect of chemical composition. It can obtain better non-oriented silicon steel products with higher and more stable production rates, lower production difficulty, and more energy-saving and environmentally friendly technology, including better magnetic properties, thickness accuracy, plate shape and uniformity of the same plate.

[0138] The detailed description listed above is merely a specific description of the feasible implementation of this application. The following are several specific embodiments to illustrate the specific implementation of this application, so as to demonstrate the advantages and effects of this application.

[0139] First, these embodiments all use the technology of this application to prepare hot-rolled plates, specifically including steelmaking process, continuous casting process, heating process and hot rolling process. The chemical composition of the final steel / continuous casting billet is shown in Table 1, and some important parameters in each process are shown in Table 2 and Table 3.

[0140] [Table 1]

[0141] [Table 2]

[0142] [Table 3]

[0143] Using the prepared hot-rolled sheet, without normalizing the hot-rolled sheet or preheating before cold rolling, non-oriented silicon steel products are produced through a process route of pickling continuous rolling - hardening normalizing - single-stand precision cold rolling - annealing. Some important parameters in the production process are shown in Tables 4 to 6. It is understood that the parameters shown here represent only a portion, not all, of the important parameters, and the values ​​are merely examples and do not represent the necessary choices for this application; conversely, parameters not shown in the tables do not necessarily mean they are not important parameters. These can be understood in conjunction with the preceding descriptions.

[0144] [Table 4]

[0145] [Table 5]

[0146] [Table 6]

[0147] Next, samples of the non-oriented silicon steel products obtained from each embodiment were taken and tested, including performance testing and microstructure testing. The results are shown in Table 7. Specifically, tensile strength, yield strength, and elongation were tested using GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Room temperature test method"; iron loss and magnetic induction intensity were tested using GB / T 3655-2022 "Method for measuring the magnetic properties of electrical steel sheets (strips) using Epstein squares"; grain size was measured using GB / T 4335-2013 "Method for determining the ferrite grain size of cold-rolled low-carbon steel sheets"; and the flatness of the non-oriented silicon steel products was measured using GB / T 708-2019 "Dimensions, shape, weight and permissible deviations of cold-rolled steel sheets and strips".

[0148] [Table 7]

[0149] Compared with existing technologies, the edge quality control method of hot-rolled steel plates in this application breaks through the limitations of traditional approaches that only make local adjustments to the hot rolling process. It innovatively moves the control point forward to the continuous casting source. Through the systematic design of steel composition and continuous casting process (such as controlling the equiaxed crystal ratio ≥65% and the concave depth of narrow cross section ≤3mm), combined with a specific slab heating regime (controlling the furnace temperature and segmented heating rate), it fundamentally inhibits the abnormal growth of columnar crystals at the edge of the slab during subsequent heating. This synergistic control strategy directly addresses the root cause of edge cracking, resulting in stable edge quality and no edge crack defects in the produced hot-rolled steel plates. It fundamentally solves the key problem restricting the smooth production of high-grade products. The technical effect is clear and significant, providing new theoretical guidance and technical path for the development of production processes for high-grade and even higher-performance silicon steel, and has important industry leadership and technological progress significance.

[0150] Furthermore, the production method of the non-oriented silicon steel product of this application uses the aforementioned hot-rolled plate and prepares high-grade non-oriented silicon steel through a novel process of pickling continuous rolling-hardening-single-single-precision cold rolling-annealing. Before pickling continuous rolling, there is no need to normalize or preheat the hot-rolled plate, resulting in a series of benefits, including but not limited to: reducing the requirements for the rolled piece during cold rolling, thereby reducing the production difficulty of hot rolling and improving the efficiency of hot rolling and pickling; reducing the requirements for the degree of coordinated deformation of the surface and thickness center of the rolled piece during cold rolling, thereby reducing the equipment requirements for multi-stand pickling continuous rolling units, enabling rapid continuous cold rolling, greatly improving the production efficiency of cold rolling and reducing the production difficulty of cold rolling; simultaneously, during pickling continuous rolling, two or more hot-rolled plates are sequentially welded together end to end to achieve full-length rolling, which not only improves efficiency but also significantly increases the yield.

[0151] In summary, this not only ensures smooth board production throughout the entire process but also reduces the overall production difficulty and improves overall production efficiency. The resulting high-grade non-oriented silicon steel product not only has lower iron loss and higher magnetic induction, resulting in excellent magnetic properties, but also significantly improved dimensional accuracy, meeting the stringent requirements of high-end motors and transformers for core core materials.

Claims

1. A method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate, characterized in that, The control method includes the following steps. Steelmaking process: Refining steel. The final chemical composition of the molten steel, by mass percentage, includes: C≤0.005%, Si:1.5~4.5%, Mn:0.2~1.5%, Al≤1.5%, S≤0.01%, P≤0.08%, N≤0.01%, O≤0.01%, Cr, Ni and Cu ≤5.0% respectively, Ti, V, Mo and Nb ≤0.1% respectively, and the remainder being Fe and unavoidable inclusions. Continuous casting process: The obtained molten steel is made into a continuous casting billet with a thickness of 200~250mm by continuous casting technology. The equiaxed crystal ratio of the continuous casting billet is ≥65% and the concave depth of the narrow section is ≤3mm. Heating process: The continuously cast billet is heated in a heating furnace with an initial temperature ≥350℃ and a soaking temperature of 1000~1150℃; during the heating of the continuously cast billet, when the temperature of the continuously cast billet is 350~800℃, the heating rate is controlled at 5~15℃ / min; when the temperature of the continuously cast billet is 800~1150℃, the heating rate is controlled at ≥15℃ / min. Hot rolling process: The continuously cast billet is subjected to multiple passes of rough rolling and multiple passes of finish rolling to prepare a hot-rolled plate.

2. The method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate according to claim 1, characterized in that, The final chemical composition of the molten steel, by mass percentage, includes: C≤0.005%, Si:1.5~4.5%, Mn:0.2~1.5%, Al:0.30~1.5%, Si+Al:1.7~4.8%, S≤0.01%, P≤0.08%, N≤0.01%, O≤0.01%, Cr, Ni and Cu ≤5.0% respectively, Mo, Nb, V and Ti ≤0.1% respectively, with no Sn and Sb or any one or both of Sn:0.01~0.15% and Sb:0.01~0.15%, and the remainder being Fe and unavoidable inclusions; Alternatively, the chemical composition of the final molten steel, by mass percentage, includes: C ≤ 0.005%, Si: 1.5~4.5%, Mn: 0.2~1.5%, Al ≤ 0.0030%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni and Cu ≤ 5.0% respectively, Mo, Nb, V and Ti ≤ 0.1% respectively, with no Sn and Sb or any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%, and the remainder being Fe and unavoidable inclusions; Alternatively, the chemical composition of the final molten steel, by mass percentage, includes: C ≤ 0.005%, Si: 3.2~3.7%, Mn: 0.3~0.8%, Al: 0.70~1.2%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni and Cu ≤ 5.0% respectively, Mo, Nb, V and Ti ≤ 0.1% respectively, with no Sn and Sb or any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%, and the remainder being Fe and unavoidable inclusions.

3. The method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate according to claim 1, characterized in that, The final molten steel contains no Sn or Sb, or the chemical composition of the final molten steel, by mass percentage, includes either or both of Sn: 0.01 to 0.15% and Sb: 0.01 to 0.15%.

4. The method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate according to claim 1, characterized in that, Continuous casting process: The casting speed during continuous casting is controlled at 0.80~1.10m / min.

5. The method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate according to claim 2, characterized in that, Continuous casting process: When the chemical composition of the final molten steel meets the requirement of Si+Al≥3.0% by mass percentage, the casting speed during continuous casting is 0.80~0.90m / min; When the chemical composition of the final molten steel meets the mass percentage requirement of 2.0% < Si + Al < 3.0%, the casting speed during continuous casting is 0.90~1.00 m / min; When the chemical composition of the final molten steel meets the requirement of Si+Al≤2.0% by mass percentage, the casting speed during continuous casting is 1.00~1.10m / min.

6. The method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate according to claim 1, characterized in that, Continuous casting process: The cooling water flow rate of the narrow face of the crystallizer is controlled at 2.5 L / (mm×min), and the cooling water flow rate of the wide face is controlled at 2.0 L / (mm×min); Electromagnetic stirring is applied in the secondary cooling section with a stirring current of 500~550 A and a stirring frequency of 10~12 Hz.

7. The method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate according to claim 1, characterized in that, Hot rolling process: The initial rolling temperature of the first finishing rolling pass is ≥950℃, the final rolling temperature of the last finishing rolling pass is (830~880)±15℃, the total reduction rate of finishing rolling is 90~96%, and the reduction rate of the last finishing rolling pass is 20~25%; After multiple passes of precision rolling, the product is wound at a temperature of (600~650)±15℃.

8. The method for edge quality control of high-grade non-oriented silicon steel hot-rolled plate according to claim 1, characterized in that, Steelmaking process: Steel is produced through a sequence of hot metal desulfurization, converter smelting, and vacuum refining; among which, Vacuum refining: During the alloying process, desulfurizing agent is added in two batches, and degassing is carried out for more than 12 minutes under a vacuum degree of less than 2 mbar. The net circulation time is ≥10 minutes. The steel temperature after vacuum refining is controlled at T=(t+50℃)±5℃, where t is the liquidus temperature corresponding to the chemical composition of the final molten steel.

9. A method for producing high-grade non-oriented silicon steel, characterized in that, The production method prepares non-oriented silicon steel products from hot-rolled plates through acid continuous rolling, hardened plate normalizing, single-stand precision cold rolling, and annealing processes. The hot-rolled plate is prepared by the edge quality control method for high-grade non-oriented silicon steel hot-rolled plate according to any one of claims 1 to 8; The thickness of the non-oriented silicon steel finished product is (0.05~0.50)±0.005mm.

10. The method for producing high-grade non-oriented silicon steel according to claim 9, characterized in that, Pickling and continuous cold rolling process: Hot-rolled plates are pickled and subjected to multiple passes of continuous cold rolling using a multi-stand pickling and continuous cold rolling mill to obtain hardened plates; the reduction rate of the first pass of cold rolling is 20~30%, and the reduction amount is ≤0.70mm; Normalizing process of rolled hard plate: The obtained rolled hard plate is normalized at a normalizing temperature of (850~1000)±10℃ for a normalizing time of 60~100s. Single-stand cold rolling process: 2 to 4 passes of cold rolling are performed using a single-stand cold rolling mill, with a total reduction rate of 40 to 80%. The reduction rate of the first pass of cold rolling is ≥30%, and the reduction amount is ≤0.40mm. Annealing process: Annealing temperature is 850~1050℃, annealing time is 40~120s.

11. The method for producing high-grade non-oriented silicon steel according to claim 9, characterized in that, Normalizing process for rolled hard sheet: Normalizing is carried out in a normalizing furnace with a tension of 8~10 N / mm. 2 After normalization, temperature-controlled cooling is carried out. When the surface temperature of the steel plate is ≥400℃, the cooling rate is 10~15℃ / s, and when the surface temperature of the steel plate is <400℃, the cooling rate is 15~20℃ / s.

12. The method for producing high-grade non-oriented silicon steel according to claim 9, characterized in that, Single-stand precision cold rolling process: The single-stand rolling mill used is a six-roll single-stand cold rolling mill or a twenty-roll single-stand cold rolling mill; The working roll diameter of the 20-roll single-stand cold rolling mill is 45~65mm. The roughness of the working roll used for the first pass of finishing cold rolling is 2.50±0.5μm, and the roughness of the working roll used for the last pass of finishing cold rolling is 0.50±0.10μm.

13. The method for producing high-grade non-oriented silicon steel according to claim 9, characterized in that, Annealing process: The tension inside the annealing furnace is controlled at 1~3 N / mm. 2 After the annealing time is reached, segmented cooling is used. The segmented controlled cooling includes: a cooling rate of 5~10℃ / s when the steel plate surface temperature is >700℃, a cooling rate of 10~15℃ / s when the steel plate surface temperature is 400~700℃, and a cooling rate of 15~20℃ / s when the steel plate surface temperature is <400℃.

14. The method for producing high-grade non-oriented silicon steel according to claim 10, characterized in that, The thickness of the non-oriented silicon steel finished product is >0.15mm, and the corresponding thicknesses of hot-rolled plate and hard-rolled plate are 2.3~3.5mm and 0.4~1.2mm, respectively. In the annealing process: the annealing temperature is T. t1 ±10℃, annealing time 100~120s; T t1 The unit is ℃, and its value is taken from the formula 900+200(11Si-14Mn+21Al). The element symbols in the formula represent the mass percentage of the corresponding element in the continuously cast billet.

15. The method for producing high-grade non-oriented silicon steel according to claim 10, characterized in that, The thickness of the non-oriented silicon steel finished product is 0.05~0.15mm, and the corresponding thicknesses of hot-rolled plate and hard-rolled plate are 1.8~2.3mm and 0.2~0.35mm, respectively. In the annealing process: the annealing temperature is T. t2 ±10℃, annealing time (30~50)s+400h s / mm, where h is the thickness of the cold-rolled sheet in mm; T t2 The unit is ℃, and its value is taken from the formula 820 + 200(11Si - 14Mn + 21Al) + 400h mm. -1 The element symbols in the formula represent the mass percentage of the corresponding element in the continuously cast billet.

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