High-rolling-ability production method of series high-grade non-oriented silicon steel

Abstract

The invention discloses a high-rolling-ability production method of series high-grade non-oriented silicon steel. The production method comprises the following steps in sequence: continuous casting; carrying out heating, rough rolling and finish rolling on the continuous casting billet to obtain a 2.3-3.5 mm hot rolled plate; the hot-rolled plate is not subjected to normalizing treatment and then enters a multi-rack acid continuous rolling unit to be subjected to acid pickling and continuous cold rolling, the reduction rate of first-pass cold rolling is 20-30%, the reduction amount is smaller than or equal to 0.70 mm, and a rolled hard plate with the thickness of 0.4-1.2 mm is obtained; the roll bending force of a working roll of the multi-rack acid continuous rolling unit is controlled within the range of 50 kN to 150 kN, so that controllable edge waves with the height of 1.0-3.0 mm are generated on the edge of the rolled hard board; normalizing the rolled hard board in a normalizing furnace; 2-4 passes of finish cold rolling are conducted on the steel plate through a single-stand rolling mill, the total reduction rate ranges from 40% to 65%, and a finish cold-rolled plate with the thickness ranging from 0.15 mm to 0.50 mm + / -0.003 mm is obtained; and annealing to obtain a non-oriented silicon steel finished product.

Description

Technical Field

[0001] This application belongs to the field of steel material preparation technology, and relates to a method for producing a series of high-grade non-oriented silicon steels with high rollability. Background Technology

[0002] Non-oriented silicon steel is a core functional material for manufacturing motor cores and transformer cores. Its iron loss and magnetic flux levels directly determine the energy efficiency rating of electrical products. With the acceleration of carbon neutrality in global industry and the continuous upgrading of motor energy efficiency standards, the market demand for high-grade non-oriented silicon steel is growing rapidly, while higher requirements are being placed on magnetic properties and production efficiency.

[0003] The typical production process for high-grade non-oriented silicon steel includes: hot rolling → normalizing → pickling → cold rolling → finished product annealing → coating. To obtain lower iron loss, the composition design requires the addition of higher levels of Si and Al to improve resistivity and reduce eddy current losses. However, both Si and Al are ferrite stabilizing elements, and increasing their content can lead to the following prominent problems:

[0004] (1) The hot rolling process is completed in the ferrite region, and the post-rolling structure is a deformed fibrous structure, which is difficult to undergo dynamic recrystallization, and the plasticity of the hot-rolled plate is significantly reduced; (2) In order to improve magnetic properties, the traditional process must normalize the hot-rolled plate before cold rolling to cause the fiber structure to recrystallize and the grains to coarsen; however, the normalization process further reduces the plasticity of the hot-rolled plate. (3) During the cold rolling process, the deformation in the thickness direction of the low-plasticity hot-rolled normalized plate is not coordinated - the surface layer extends more than the center layer, which causes tensile stress in the center layer to induce microcracks. The cracks extend to the edge to form edge cracks, and in severe cases, the strip breaks.

[0005] The aforementioned problems have long constrained the production efficiency and cost of high-grade non-oriented silicon steel.

[0006] Existing technologies mainly seek solutions through the following paths: First, limiting the upper limit of the total Si+Al content, sacrificing some magnetic properties in exchange for rollability, which makes it impossible to meet the requirements of higher energy efficiency levels; Second, reducing the thickness of hot-rolled plates to reduce the total deformation of cold rolling and alleviate deformation inconsistency, but this method significantly increases the hot rolling load, places stringent requirements on the capacity of hot rolling production lines, and the temperature drop accelerates after the thickness of hot-rolled plates is reduced, making it more difficult to control the plate shape; Third, preheating before cold rolling to improve plasticity, but this method requires the addition of preheating equipment and energy medium, increasing investment and operating costs, and cannot fundamentally solve the problem of strip breakage in cold rolling of high Si+Al grades; Fourth, using single-stand reciprocating cold rolling, but existing technologies generally believe that it is impossible to achieve stable plate passage on acid continuous rolling mills, resulting in long single-coil rolling time, low head and tail yield, and low production efficiency, which seriously restricts the large-scale, low-cost manufacturing of high-grade silicon steel.

[0007] In summary, the existing production methods for high-grade non-oriented silicon steel have the following inherent contradictions: it is difficult to simultaneously improve magnetic properties and ensure cold-rolling rollability; and there is a conflict between pursuing production efficiency (continuous acid and rolling production) and adapting to the characteristics of high-grade steel (low plasticity). Summary of the Invention

[0008] To address the aforementioned technical problems, the purpose of this application is to provide a method for producing a series of high-grade non-oriented silicon steels with high rollability.

[0009] To achieve the aforementioned objectives, one embodiment of this application provides a method for producing non-oriented silicon steel. The production method includes the following steps in sequence: Continuous casting process: Obtaining a continuously cast billet, wherein the chemical composition of the continuously cast billet, 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, Mo, Nb, V and Ti ≤0.1% respectively, and the remainder being Fe and unavoidable inclusions; Hot rolling process: The continuously cast billet is heated, rough rolled, and finish rolled to obtain a hot-rolled plate of 2.3~3.5mm; Pickling and continuous cold rolling process: The hot-rolled plate is not routinely treated and enters a multi-stand pickling and continuous cold rolling unit for pickling and continuous cold rolling. The reduction rate of the first cold rolling is 20~30% and the reduction amount is ≤0.70mm, to obtain a hardened plate with a thickness of 0.4~1.2mm. During continuous cold rolling, the bending force of the work rolls of the multi-stand pickling and continuous cold rolling unit is controlled within the range of 50kN to 150kN, so that the edge of the obtained hardened plate produces a controllable edge wave with a height of 1.0~3.0mm. Normalizing process of rolled hard sheet: The rolled hard sheet is normalized in a normalizing furnace; Single-stand cold rolling process: The normalized steel plate is cold rolled in 2 to 4 passes using a single-stand rolling mill, with a total reduction of 40 to 65%, to obtain a cold-rolled plate with a thickness of (0.15 to 0.50) ± 0.003 mm. Annealing process: The cold-rolled steel sheet is annealed in an annealing furnace to obtain non-oriented silicon steel finished product.

[0010] As an improvement to one embodiment, the chemical composition of the continuously cast billet, by mass percentage, includes: Al: 0.30~1.5% and Si+Al: 1.7~4.8%, or Al≤0.0030%; And / or, the chemical composition of the continuously cast billet, by mass percentage, further includes any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%.

[0011] As an improvement to one implementation method, in the hot rolling process: 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℃.

[0012] As an improvement to one implementation method, 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%.

[0013] As an improvement to one implementation method, the hot rolling process: During heating, the temperature of the continuously cast billet entering the heating furnace is ≥350℃, and the soaking temperature is 1080~1150℃; 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.

[0014] As an improvement to one implementation method, the hot rolling process involves coiling after precision rolling at a temperature of (600~650)±15℃.

[0015] As an improvement to one implementation method, in the acid rolling process, the reduction rate of the final cold rolling pass is 15-25%.

[0016] As an improvement to one implementation method, the acid rolling process: The surface roughness of the work rolls on the first and second stands of the multi-stand pickling and rolling mill is 1.00±0.20μm, the chamfer depth at the strip edge corresponding to the work rolls is 30~60μm, and the chamfer insertion amount is 70~100mm; the surface roughness of the work rolls on the third to fifth stands is 0.50±0.10μm, the chamfer depth at the strip edge corresponding to the work rolls is 10~15μm, and the chamfer insertion amount is 200~300mm.

[0017] As an improvement to one implementation method, the normalizing process of the rolled sheet is as follows: the rolled sheet is normalized to allow complete recrystallization of the microstructure; the normalizing temperature is (850~1000)±10℃ and the normalizing time is 60~100s.

[0018] As an improvement to one implementation method, the normalizing process of the rolled hard plate: The chemical composition of the continuously cast billet, by mass percentage, satisfies Si+Al≥3.0%, and the normalizing temperature is (850~950)±10℃; Alternatively, the chemical composition of the continuously cast billet, by mass percentage, satisfies 2.0% < Si + Al < 3.0%, and the normalizing temperature is (900~980) ± 10℃; Alternatively, the chemical composition of the continuously cast billet, by mass percentage, satisfies Si+Al≤2.0% and the normalizing temperature is (950~1000)±10℃.

[0019] As an improvement to one implementation method, the normalizing process of the rolled plate is as follows: after normalizing, temperature-controlled cooling is performed, with a cooling rate of 10~15℃ / s when the surface temperature of the steel plate is ≥400℃, and a cooling rate of 15~20℃ / s when the surface temperature of the steel plate is <400℃.

[0020] As an improvement to one implementation method, in the normalizing process of rolled hard sheet: the tension in the normalizing furnace is 8~10 N / mm. 2 The rolled hard sheet is normalized in a weakly reducing atmosphere, which is a mixture of H2 and N2, in which the volume percentage of H2 is 15-25%.

[0021] As an improvement to one implementation method, the single-stand precision cold rolling process is as follows: precision cold rolling is performed without preheating, and the reduction rate of the first precision cold rolling is ≥30% and the reduction amount is ≤0.40mm.

[0022] As an improvement to one implementation method, the single-stand precision cold rolling process: The single-stand rolling mill 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.

[0023] As an improvement to one implementation method, the annealing process involves annealing the cold-rolled sheet in an annealing furnace to allow complete recrystallization of the microstructure. The annealing temperature is 850~1050℃ and the annealing time is 100~120s.

[0024] As an improvement to one implementation method, the annealing process involves controlling the tension within the annealing furnace at 1~3 N / mm. 2 .

[0025] As an improvement to one implementation method, the annealing process: After the annealing time is reached, temperature-controlled cooling is carried out. The cooling rate is 5~10℃ / s when the steel plate surface temperature is >700℃, 10~15℃ / s when the steel plate surface temperature is 400~700℃, and 15~20℃ / s when the steel plate surface temperature is <400℃.

[0026] As an improvement to one implementation method, 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.

[0027] As an improvement to one implementation method, the continuous casting process has the following characteristics: the thickness of the continuously cast billet is 200~250mm, the equiaxed crystal ratio is ≥65%, and the narrow cross-section concave depth is ≤3mm.

[0028] As an improvement to one implementation method, in the continuous casting process, the casting speed is controlled at 0.80~1.10m / min.

[0029] Compared with existing technologies, this application reconstructs the process of "direct pickling and rolling of hot-rolled plates without normalization - normalization of hardened plates - single-stand finishing rolling", and adopts the core method of controlling the bending roll force to generate controllable edge waves (micro-edge waves) in the pickling and rolling process. This achieves a synergistic improvement in the rollability and magnetic properties of high-grade non-oriented silicon steel. The specific beneficial effects are as follows: ① By controlling the first pass reduction rate of acid continuous rolling at 20~30% and the reduction amount ≤0.70mm, and the bending roll force at 50~150kN, a controllable edge wave of 1.0~3.0mm is generated at the edge of the rolled hard plate. This edge wave actively releases the edge tensile stress, fundamentally avoiding edge cracks and strip breakage. As a result, when producing ultra-high grade products with Si+Al≥3.0%, the strip breakage rate of acid continuous rolling is significantly reduced compared to existing technologies, thereby achieving stable and continuous production of this type of grade on a multi-stand acid continuous rolling mill. ② The normalization process of hot-rolled plates and the preheating process before cold rolling are eliminated, which shortens the entire process, shortens the production cycle, reduces energy consumption per ton of steel, reduces the amortization cost of equipment investment per ton of steel, and further enhances the energy-saving and carbon emission reduction benefits. ③ The thickness of hot-rolled plates is increased from the small thickness forced by existing technology to 2.3~3.5mm, thereby reducing the hot-rolled finishing load, increasing the hot-rolled yield, and increasing the output and efficiency during pickling continuous rolling; ④ By normalizing 0.4~1.2mm thick hard-rolled plates, the normalizing temperature window is wider than that of hot-rolled normalized plates. The optimal system can be flexibly matched for different grades, thus having better magnetic properties than hot-rolled plate normalizing technology, and avoiding the defect of low rollability caused by hot-rolled plate normalizing. ⑤ In addition, it significantly reduces the dependence of cold rolling on the plasticity of hot-rolled plates, and the upper limit of Si+Al can be relaxed to 4.8% from conventional technology, providing an engineerable process platform for developing ultra-high grade non-oriented silicon steel with higher energy efficiency.

[0030] In summary, this invention, with its core technology of controllable edge waviness in acid continuous rolling, achieves a synergistic breakthrough in the rollability, magnetic properties, and production efficiency of high-grade non-oriented silicon steel, demonstrating significant inventiveness and industrial application value. Detailed Implementation

[0031] 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.

[0032] This application provides a method for producing non-oriented silicon steel, and more particularly a method for producing multi-series high-grade non-oriented silicon steel.

[0033] The production method includes, in sequence, continuous casting, hot rolling, acid rolling, hardened plate normalizing, single-stand precision cold rolling, and annealing.

[0034] Specifically, the continuous casting process involves obtaining a continuously cast billet, the chemical composition of which, 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, Mo, Nb, V and Ti ≤ 0.1% respectively, with the remainder being Fe and unavoidable inclusions; Hot rolling process: The continuously cast billet is heated, rough rolled, and finish rolled to obtain a hot-rolled plate of 2.3~3.5mm; Pickling and continuous cold rolling process: The hot-rolled plate is not routinely treated and enters a multi-stand pickling and continuous cold rolling unit for pickling and continuous cold rolling. The reduction rate of the first cold rolling is 20~30% and the reduction amount is ≤0.70mm, to obtain a hardened plate with a thickness of 0.4~1.2mm. During continuous cold rolling, the bending force of the work rolls of the multi-stand pickling and continuous cold rolling unit is controlled within the range of 50kN to 150kN, so that the edge of the obtained hardened plate produces a controllable edge wave with a height of 1.0~3.0mm. Normalizing process of rolled hard sheet: The rolled hard sheet is normalized in a normalizing furnace; Single-stand cold rolling process: The normalized steel plate is cold rolled in 2 to 4 passes using a single-stand rolling mill, with a total reduction of 40 to 65%, to obtain a cold-rolled plate with a thickness of (0.15 to 0.50) ± 0.003 mm. Annealing process: The cold-rolled steel sheet is annealed in an annealing furnace to obtain non-oriented silicon steel finished product.

[0035] Thus, this application reconstructs the process by "direct acid rolling without normalization of hot-rolled plate - normalization of hardened plate - single-stand finishing rolling," and adopts the core method of generating controllable edge waves (micro-edge waves) by controlling the bending roll force in the acid rolling process. For example, the reduction rate of the first pass of acid rolling is controlled at 20~30%, the reduction amount is ≤0.70mm, and the bending roll force is controlled at 50~150kN, so that the edge of the hardened plate generates controllable edge waves of 1.0~3.0mm. These edge waves actively release the edge tensile stress, fundamentally avoiding edge cracks and strip breakage. As a result, when producing ultra-high grade products with Si+Al≥3.0%, the strip breakage rate of acid rolling is significantly reduced compared with the existing technology, thereby achieving stable and continuous production of this type of grade on a multi-stand acid rolling mill. Therefore, it achieves a synergistic improvement in the rollability and magnetic properties of high grade non-oriented silicon steel.

[0036] The specific implementation methods for each process are described in detail below.

[0037] Continuous casting process In this process, continuously cast billets are prepared by continuous casting.

[0038] The chemical composition of the continuously cast billet, 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, Mo, Nb, V and Ti≤0.1% respectively, and the remainder is Fe and unavoidable inclusions.

[0039] It should be noted that, understandably, the chemical composition of the continuously cast billet is consistent with that of the finished non-oriented silicon steel product. During the process of preparing the finished non-oriented silicon steel product from the continuously cast billet, the chemical composition remains unchanged. The chemical composition of the non-oriented silicon steel can be characterized by sampling and testing the continuously cast billet.

[0040] In this application, samples can be taken from the continuously cast billet or the final non-oriented silicon steel product 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 continuously cast billet or the final non-oriented silicon steel product can be tested in accordance with GB / T 223 series "Methods for Chemical Analysis of Iron and Steel and Alloys".

[0041] The following section provides a detailed explanation of the role and mechanism of each chemical element in the chemical composition.

[0042] 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%.

[0043] 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%.

[0044] 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%.

[0045] 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%, and more preferably in the range of 0.70~1.2%.

[0046] 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 particles, 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%.

[0047] 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%.

[0048] 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%.

[0049] 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%.

[0050] Cr, Ni, and 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%.

[0051] 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%.

[0052] 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%.

[0053] 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%.

[0054] 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, the Nb+V+Ti+Mo is controlled to be ≤0.009%.

[0055] Preferably, in some embodiments, the chemical composition of the non-oriented silicon steel also satisfies 1.7%≤Si+Al≤4.8%. This can further reduce production difficulty, improve smooth production operation, reduce the risk of strip breakage, and also improve magnetic and mechanical properties.

[0056] Furthermore, in some embodiments, the non-oriented silicon steel may further contain either or both of Sn and Sb.

[0057] For example, in some embodiments, the chemical composition of the non-oriented silicon steel contains Sn, and the Sn content is controlled within the range of 0.01 to 0.15%, that is, 0.01 to 0.15% Sn replaces the original iron element to further improve the magnetic properties.

[0058] For example, in some embodiments, the chemical composition of the non-oriented silicon steel contains Sb, and 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 the magnetic properties.

[0059] For example, in some embodiments, the chemical composition of the non-oriented silicon steel contains both Sn and Sb, with the Sn content controlled in the range of 0.01 to 0.15% and the Sb content controlled in the range of 0.01 to 0.15%, or even the sum of Sn and Sb in the range of 0.01 to 0.15%.

[0060] Preferably, the thickness of the continuously cast billet is 200~250mm, the equiaxed crystal ratio is ≥65%, and the narrow cross-section concave depth is ≤3mm. This avoids the internal stress generated by the structure and shape of the continuously cast billet, thereby reducing the occurrence of cracks and strip breakage during subsequent rolling processes (including hot rolling, pickling rolling, and cold finishing rolling), and further ensuring smooth plate production throughout the entire process.

[0061] 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.

[0062] 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.

[0063] In one embodiment, the casting speed during continuous casting is controlled at 0.80~1.10m / min, thereby achieving an equiaxed crystal ratio of ≥65% and a narrow cross-section concave depth of ≤3mm for the continuously cast billet.

[0064] For example, in some embodiments, if the chemical composition of the non-oriented silicon steel, by mass percentage, satisfies Si+Al≥3.0%, then the casting speed during continuous casting is controlled at 0.80~0.90 m / min; in other embodiments, if the chemical composition of the non-oriented silicon steel, by mass percentage, satisfies 2.0%<Si+Al<3.0%, then the casting speed during continuous casting is controlled at 0.90~1.00 m / min; in still other embodiments, if the chemical composition of the non-oriented silicon steel, by mass percentage, satisfies Si+Al≤2.0%, then the casting speed during continuous casting is controlled at 1.00~1.10 m / min.

[0065] More preferably, in the continuous casting process: a continuously cast billet is prepared on the continuous casting machine. After leaving the continuous casting machine, the billet is placed in a heating pit for heat preservation at a temperature of 400~900℃ for ≥30 minutes. Thus, by heat preservation, the billet is kept at a temperature of 400~900℃ for at least 30 minutes, which optimizes the internal structure and surface quality of the billet and prevents cold cracking.

[0066] Furthermore, the molten steel required for the preparation of the continuously cast billet can be smelted and obtained by any feasible method in the art. For example: first, the molten iron is desulfurized, and the temperature of the desulfurized molten iron is ≥1320℃; scrap steel is added to the desulfurized molten iron and smelted in a converter, with the scrap steel accounting for 30~40% of the total mass of the scrap steel and molten iron. The scrap steel includes silicon steel scrap for motor cores or motor core scrap. The final temperature of the molten steel at the end of the converter smelting is 1670±15℃; then, the molten steel is transferred to a vacuum furnace for vacuum refining. During the refining process, alloying, desulfurization, and net recycling are carried out, and the produced molten steel is used for subsequent continuous casting processes.

[0067] Hot rolling process In this process, the continuously cast billet is heated, rough rolled, and finish rolled to obtain a hot-rolled plate with a thickness of 2.3~3.5mm.

[0068] In one embodiment, during heating, the temperature of the continuously cast billet entering the heating furnace is ≥350°C.

[0069] The heat spreader temperature is 1080~1150℃. Such a heat spreader temperature can lay the foundation for subsequent processes.

[0070] Optionally, the heat spreader temperature can be any value among 1080℃, 1090℃, 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, and 1150℃, or other values ​​within the range of 1080~1150℃.

[0071] Preferably, 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 avoids abnormal growth of columnar crystals inside the billet, thereby preventing subsequent edge cracks or band breakage caused by columnar crystals and increasing the probability of successful production.

[0072] In some embodiments, for example, when the chemical composition of the continuously cast billet satisfies Si+Al≥3.0% by mass percentage, and when the temperature of the continuously cast billet is 350~800°C, the heating rate can be further controlled at 5~10°C / min. When Si+Al<3.0%, and when the temperature of the continuously cast billet is 350~800°C, the heating rate is 10~15°C / min. Thus, by precisely controlling the heating rate, abnormal growth of columnar crystals inside the continuously cast billet can be largely avoided, further increasing the probability of successful production.

[0073] In some embodiments, the steel plate is kept at a uniform heating temperature for 40 to 60 minutes during this process.

[0074] This hot rolling process includes multiple passes of roughing and multiple passes of finishing. For example, the number of passes in roughing can be five to nine, such as six passes; the number of passes in finishing can be five to nine, such as seven passes. But it is not limited to these.

[0075] 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℃.

[0076] The control of the rolling temperature, in conjunction with the subsequent winding temperature control, can ensure that the internal structure of the obtained hot-rolled plate is a uniform hot-rolled deformed fiber structure, while also ensuring the edge quality of the hot-rolled plate.

[0077] 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℃.

[0078] In some embodiments, preferably, during the hot rolling process: 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 of the finishing mill stand.

[0079] Furthermore, preferably, the total reduction rate of finishing rolling is 90-96%, and the reduction rate of the final finishing rolling pass is 20-25%. For example, the thickness of the intermediate billet obtained from rough rolling is 38-50 mm, and the thickness of the hot-rolled plate is 2.3-3.5 mm.

[0080] On the one hand, in the technical solution of this application, normalization is not performed before the acid rolling process. As a result, the plasticity of the steel plate before cold rolling is greatly improved compared with common technologies. This can reduce the requirements of cold rolling on the rolled piece. For example, a thicker hot-rolled plate can be used as the rolled piece in cold rolling. In this way, the production difficulty of hot rolling is reduced, which is conducive to improving the production stability and production efficiency of hot rolling.

[0081] On the other hand, controlling the total reduction rate of finishing rolling and the reduction rate of the last finishing rolling can improve the shape of hot-rolled plates, which in turn can improve the stability and production rate of subsequent cold rolling.

[0082] In one embodiment, after the hot-rolled plate exits the finishing mill stand, it can be cooled by controlled temperature using air cooling or water cooling, such as laminar flow cooling, before proceeding to the subsequent coiling process. Specific cooling techniques can be implemented in any feasible manner in the art, and this application does not limit them.

[0083] Furthermore, after precision rolling, winding can be performed at a temperature of (600~650)±15℃.

[0084] Thus, by combining the comprehensive control of various temperatures during finishing and coiling, it is possible to ensure that the internal structure of the hot-rolled coil obtained in the coiling process is a uniform hot-rolled deformed fiber structure, while also ensuring the edge quality of the hot-rolled coil.

[0085] 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℃.

[0086] [Acid-rolling process] In this process, a multi-stand pickling and cold rolling mill is used to obtain a hardened plate.

[0087] 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, while meeting high environmental protection requirements.

[0088] Furthermore, through the preceding hot rolling and acid continuous rolling processes, deformed fibrous ferrite structures are formed in the steel plate, which are thin and have a bright surface. This creates conditions for subsequent control of grain size and texture, as well as for the realization of subsequent single-stand precision cold rolling, making it possible for the low-difficulty production technology of this application to successfully produce plates.

[0089] In an embodiment where coiling is performed in a hot rolling process, the pickling and continuous cold rolling process can first involve leveling, followed by pickling and multiple passes of continuous cold rolling.

[0090] After leveling, hot-rolled steel sheets can achieve a flatness of ≤10mm over a length of 1000mm. In this application, the steel plate can be sampled and tested in accordance with GB / T 709-2019 "Dimensions, shape, weight and permissible deviations of hot-rolled steel plates and strips" to obtain the range of unevenness.

[0091] Preferably, in this acid-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, leading to significant difficulties in both hot and cold rolling. However, the present application achieves a small reduction in the first cold rolling pass, thereby reducing the equipment requirements for multi-stand acid-rolling mills and the thickness requirements for hot-rolled plates, greatly reducing production difficulty and improving production efficiency.

[0092] More specifically, in the technical solution of this application, normalizing is not performed before the pickling and rolling process. This significantly improves the plasticity of the steel sheet before cold rolling compared to common techniques, and greatly reduces surface oxide scale, thereby increasing the pickling efficiency in the subsequent pickling and rolling process. Furthermore, due to the increased plasticity, the requirements for coordinated deformation of the workpiece surface and thickness center during cold rolling are reduced, thus lessening the limitation on the first pass reduction rate. This allows for a smaller reduction in the first pass, thereby reducing the equipment requirements for multi-stand pickling and rolling mills, such as common… The technology requires the use of a first-pass large reduction technique to produce high-grade non-oriented silicon steel. For example, common technologies require the use of a single-stand cold rolling mill for multi-pass reciprocating cold rolling. However, this application can use a multi-stand pickling and continuous rolling mill for rapid continuous cold rolling, which greatly improves production efficiency and reduces production difficulty. At the same time, the use of a multi-stand pickling and continuous rolling mill for pickling and multi-pass cold rolling, i.e., pickling and continuous rolling technology, allows two or more hot-rolled plates to be welded together end to end in sequence to achieve full-length rolling of the coil. This not only improves efficiency but also significantly increases the yield.

[0093] In this 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.

[0094] In addition, during the pickling and rolling process, the number of cold rolling passes can be four to seven. For example, five passes.

[0095] In some embodiments, the thickness of the rolled plate in this process can be 0.4~1.2mm.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] In some embodiments, the multi-stand pickling mill used is a six-roll, five-stand pickling mill.

[0101] The working roll diameter of the six-roll, five-stand acid rolling mill is 300~500mm, preferably 300~450mm, and the roughness of the working rolls of the first stand and the second stand is 1.00±0.20μm.

[0102] More preferably, in some embodiments, the first and second stands of the multi-stand pickling and rolling mill use large chamfering work rolls, with a chamfering depth of 30~60μm and a chamfering insertion amount of 70~100mm corresponding to the strip edge position.

[0103] In some embodiments, the roughness of the work rolls on the third to fifth stands of the multi-stand pickling and rolling mill is 0.50 ± 0.10 μm.

[0104] The third to fifth stands of the multi-stand acid continuous rolling mill use small chamfered work rolls, with a chamfer depth of 10~15μm and a chamfer insertion amount of 200~300mm corresponding to the edge of the strip.

[0105] In addition, in the acid rolling process: after the hot-rolled plate is leveled after being coiled, it is preferable to straighten the hot-rolled plate first to improve the shape of the rolled piece, thereby improving the stability and production rate of cold rolling.

[0106] Understandably, in common technologies, due to poor plasticity, rolled products cannot be straightened before cold rolling. However, in the technology of this application, since the hot-rolled plate is cold-rolled without normalization, it has excellent plasticity. Under these circumstances, straightening the hot-rolled plate before cold rolling greatly improves production efficiency and stability. Of course, the hot-rolled plate of this application can also be directly fed into a multi-stand pickling and rolling mill without straightening, which can also produce smoothly and quickly.

[0107] 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.

[0108] [Routing process for hardened sheet metal] In this process, the rolled hard plate is normalized in a normalizing furnace.

[0109] On the one hand, 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 the hardened plate, especially through the normalizing temperature and high tension mode, promotes the precipitation and growth of MnS and AlN precipitates, so that the deformed fibrous ferrite undergoes complete recrystallization, achieving coarsening and homogenization of the structure. This creates conditions for the control of grains and texture in the subsequent annealing process, thereby ensuring the final acquisition of excellent magnetic properties. It also creates conditions for the realization of subsequent single-stand precision cold rolling, making it possible for the low-difficulty production technology of this application to successfully produce plates.

[0110] 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, for example, the size of recrystallized grains can be 30~100μm, which promotes grain growth in subsequent annealing processes and further improves the magnetic properties of the finished product, such as reducing iron loss.

[0111] The normalizing temperature is (850~1000) ±10℃, and the normalizing time is 60~100s. In this way, by controlling the normalizing temperature and the normalizing time, the deformed fiber ferrite can be completely recrystallized, achieving coarsening and homogenization of the microstructure, which creates conditions for obtaining excellent magnetic properties and reducing the difficulty of subsequent production.

[0112] In some embodiments, if the chemical composition of the non-oriented silicon steel satisfies Si+Al≥3.0% by mass percentage, the normalizing temperature is further controlled at (850~950)±10℃, and the recrystallized grain size after normalizing is 30~60μm.

[0113] In some embodiments, if the chemical composition of the non-oriented silicon steel satisfies 2.0% < Si + Al < 3.0% by mass percentage, the normalizing temperature is further controlled at (900~980) ± 10℃, and the recrystallized grain size after normalizing is 50~80μm.

[0114] In other embodiments, if the chemical composition of the non-oriented silicon steel satisfies Si+Al≤2.0% by mass percentage, the normalizing temperature is further controlled at (950~1000)±10℃, and the recrystallized grain size after normalizing is 70~100μm.

[0115] In this application, the normalized steel plate can be sampled and tested in accordance with GB / T4335-2013 "Method for Determination of Ferrite Grain Size of Cold-Rolled Low-Carbon Steel Sheet" to obtain the recrystallized grain size of the normalized steel plate.

[0116] Preferably, in the normalizing process of rolled hard sheet: the tension in the normalizing furnace is 8~10 N / mm. 2 .

[0117] Preferably, the rolled hardened sheet is normalized in a weakly reducing atmosphere to avoid surface oxidation caused by normalization. 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.

[0118] Furthermore, in this process, after normalizing, temperature-controlled cooling is performed. When the steel plate surface temperature is ≥400℃, the cooling rate is 10~15℃ / s, and when the steel plate surface temperature is <400℃, the cooling rate is 15~20℃ / s. In this way, through the phased control of the cooling rate, combined with the high-tension mode, the grains and texture in the microstructure can be optimized, and the plate shape quality can be further improved.

[0119] Single-stand precision cold rolling process In this 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.

[0120] Building upon the foundation laid by the normalizing process of hardened steel plates, the single-stand precision cold rolling process enables this application to roll continuously cast billets to the required thickness at an extremely high production rate. This is because, prior to precision cold rolling, the rolled piece is already very thin, and its microstructure is a normalized recrystallized structure with low deformation resistance and a bright surface, thus reducing the difficulty of precision cold rolling. Furthermore, prior to the single-stand precision cold rolling process, i.e., before precision cold rolling, there is no need to preheat the normalized steel plate, ensuring efficient and stable precision cold rolling.

[0121] 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.

[0122] It is understandable that the thickness of the cold-rolled steel sheet is approximately equal to the thickness of the finished non-oriented silicon steel. In this application, the thickness of the finished non-oriented silicon steel is based on the thickness of the steel substrate in the finished product, without considering the thickness of the coating on the surface of the finished product.

[0123] In this application, the thickness of the cold-rolled steel sheet is (0.15~0.50)±0.003mm, that is, the thickness of the cold-rolled steel sheet fluctuates by ±3μm based on the 0.15~0.50mm specification.

[0124] Preferably, this process involves multiple passes of precision cold rolling, specifically 2 to 4 passes, to obtain a precision cold-rolled sheet of the desired thickness. 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.

[0125] Preferably, in the single-stand precision cold rolling process, the total reduction rate is 40-65%.

[0126] 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.

[0127] Furthermore, preferably, in the single-stand precision cold rolling process: the reduction rate of the first precision cold rolling is ≥30%.

[0128] Furthermore, in the single-stand precision cold rolling process: the reduction of the first precision cold rolling pass is ≤0.40mm.

[0129] Preferably, in the single-stand finishing cold rolling process: the work rolls of the single-stand cold rolling mill are flat rolls, and the intermediate rolls have a single-sided taper of 0.20~0.30%. In the single-stand finishing cold rolling process: the intermediate rolls are driven to move axially during finishing cold rolling. In this way, by chamfering the edges of the intermediate rolls and moving the intermediate rolls, tight edge rolling is achieved, thereby reducing edge drop and improving the control level of the same-plate difference of the final non-oriented silicon steel product, that is, small difference within the same plate.

[0130] Furthermore, optionally, the single-stand rolling mill used may specifically be a six-roll single-stand cold rolling mill or a twenty-roll single-stand cold rolling mill.

[0131] A 20-roll single-stand cold rolling mill is preferred, as its work roll diameter is significantly smaller than that of a 6-roll single-stand cold rolling mill. Consequently, the elastic deformation of the work rolls in the 20-roll single-stand cold rolling mill is lower (e.g., only a few to tens of μm) during the finishing cold rolling process, which is more conducive to reducing the longitudinal fluctuation of the steel plate thickness.

[0132] In particular, when the chemical composition of the non-oriented silicon steel meets the requirement of Si+Al≥3.0% by mass percentage and the target thickness of the cold-rolled plate is ≤0.30mm, a 20-roll single-stand cold rolling mill is preferred. This can obtain better steel plate quality and ensure smoother production.

[0133] In some embodiments, the work roll diameter of the 20-roll single-stand cold rolling mill is 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.

[0134] Annealing process In this process, the cold-rolled steel sheet is annealed in an annealing furnace at a temperature of 850~1050℃ for 100~120s, and then cooled to obtain the finished non-oriented silicon steel product.

[0135] As mentioned earlier, the thickness of this non-oriented silicon steel product is equivalent to that of a precision cold-rolled sheet, which is (0.15~0.50)±0.003mm. For example, thicknesses of 0.15mm, 0.20mm, 0.25mm, 0.27mm, 0.30mm, 0.35mm, and 0.50mm cover the application needs of ultra-thin, extra-thin, and thin non-oriented silicon steel products.

[0136] 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.

[0137] Preferably, the annealing temperature is controlled at 950~1050℃, which can further promote complete recrystallization, and the recrystallized grain size is 75~150μm, more preferably 120~150μm.

[0138] 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.

[0139] More specifically, the annealing temperature can be precisely controlled to 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.

[0140] Furthermore, continuous annealing is performed in an annealing furnace under a weakly reducing atmosphere, thereby reducing surface oxidation caused by annealing. Here, the weakly reducing atmosphere can be a mixture of H2 and N2, with H2 comprising 15-25% of the volume. Of course, this application is not limited to this.

[0141] 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.

[0142] Furthermore, in some embodiments, during the annealing process: after the annealing time is reached, temperature-controlled cooling is performed, with 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℃.

[0143] 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.

[0144] In summary, this application employs a novel process to prepare high-grade non-oriented silicon steel: heating-hot rolling-coiling-acid continuous rolling-hardening-slab cold rolling-annealing. Compared to existing technologies for high-grade non-oriented silicon steel, this process eliminates the need for normalizing the hot-rolled plate and preheating before cold rolling, reducing the overall production difficulty and improving efficiency. Furthermore, it lowers the strict upper limit on Si content (or the total Si and Al content), allowing for full utilization of the performance-enhancing effects of chemical composition. This enables the production of superior non-oriented silicon steel products with higher and more stable production rates, lower production difficulty, and more energy-efficient and environmentally friendly technology, including better magnetic properties, thickness accuracy, plate shape, and uniformity within the same plate.

[0145] Furthermore, the production method described in this application ensures that the finished product possesses excellent magnetic properties.

[0146] In some embodiments, the thickness of the non-oriented silicon steel is 0.50 ± 0.003 mm, and its iron loss P 1.5 / 50 ≤3.6W / kg, magnetic induction intensity B 5000 ≥1.65T.

[0147] In some embodiments, the thickness of the non-oriented silicon steel is 0.35±0.003mm, and its iron loss P 1.5 / 50 ≤3.0W / kg and / or iron loss P 1.0 / 400≤18.5W / kg, magnetic induction intensity B 5000 ≥1.65T.

[0148] 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.

[0149] In some embodiments, the thickness of the non-oriented silicon steel is 0.15 ± 0.003 mm, and the 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.

[0150] 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.

[0151] Regarding thickness accuracy, the longitudinal thickness fluctuation of the non-oriented silicon steel is ≤±3μm, and the transverse thickness difference is ≤5μm. 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".

[0152] 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.

[0153] 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.

[0154] These embodiments all employ the technology of this application to produce non-oriented silicon steel. Specifically, using continuously cast billets with the chemical composition shown in Table 1 as raw materials, non-oriented silicon steel products are prepared through a process route of hot rolling-acid continuous rolling-hardening-slab normalizing-single-stand precision cold rolling-annealing.

[0155] Table 1 shows the main elements and some impurity elements of each continuous casting billet. It can be understood that other impurity elements not shown also meet the content ranges described in this application.

[0156] [Table 1]

[0157] The thickness, equiaxed crystal ratio, and narrow-section concave depth of each continuously cast billet are shown in Table 2. The equiaxed crystal ratio and narrow-section concave depth were obtained by sampling and testing the continuously cast billets according to GB / T 24178-2009 "Method for Low-Magnification Evaluation of Solidification Structure of Continuously Cast Billets".

[0158] [Table 2]

[0159] Using the continuously cast billets shown in Tables 1 and 2 as the base material, non-oriented silicon steel products are prepared through a process route of hot rolling-acid continuous rolling-hardening-slab cold rolling-single-stand precision cold rolling-annealing. During the production process, normalizing and preheating are not required before acid continuous rolling, nor is preheating required before single-stand precision cold rolling.

[0160] Some of the key parameters in the production process are shown in Tables 3 to 6. It is understood that the parameters shown here represent only a portion, not all, of the key parameters, and the values ​​are merely examples and do not necessarily represent the essential choices for this application; conversely, parameters not shown in the tables do not necessarily mean they are not key parameters. This can be understood in conjunction with the preceding explanation.

[0161] [Table 3]

[0162] [Table 4]

[0163] [Table 5]

[0164] [Table 6]

[0165] Next, samples of the non-oriented silicon steel 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 finished non-oriented silicon steel was measured using GB / T 708-2019 "Dimensions, shape, weight and permissible deviations of cold-rolled steel sheets and strips".

[0166] [Table 7]

Claims

1. A method for producing non-oriented silicon steel, characterized in that, The production method includes sequential steps. Continuous casting process: Obtaining a continuously cast billet, wherein the chemical composition of the continuously cast billet, 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, Mo, Nb, V and Ti ≤0.1% respectively, and the remainder being Fe and unavoidable inclusions; Hot rolling process: The continuously cast billet is heated, rough rolled, and finish rolled to obtain a hot-rolled plate of 2.3~3.5mm; Pickling and continuous cold rolling process: The hot-rolled plate is not routinely treated and enters a multi-stand pickling and continuous cold rolling unit for pickling and continuous cold rolling. The reduction rate of the first cold rolling is 20~30% and the reduction amount is ≤0.70mm, to obtain a hardened plate with a thickness of 0.4~1.2mm. During continuous cold rolling, the bending force of the work rolls of the multi-stand pickling and continuous cold rolling unit is controlled within the range of 50kN to 150kN, so that the edge of the obtained hardened plate produces a controllable edge wave with a height of 1.0~3.0mm. Normalizing process of rolled hard sheet: The rolled hard sheet is normalized in a normalizing furnace; Single-stand cold rolling process: The normalized steel plate is cold rolled in 2 to 4 passes using a single-stand rolling mill, with a total reduction of 40 to 65%, to obtain a cold-rolled plate with a thickness of (0.15 to 0.50) ± 0.003 mm. Annealing process: The cold-rolled steel sheet is annealed in an annealing furnace to obtain non-oriented silicon steel finished product.

2. The method for producing non-oriented silicon steel according to claim 1, characterized in that, The chemical composition of the continuously cast billet, by mass percentage, includes: Al: 0.30~1.5% and Si+Al: 1.7~4.8%, or Al≤0.0030%; And / or, the chemical composition of the continuously cast billet, by mass percentage, further includes any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%.

3. The method for producing non-oriented silicon steel according to claim 1, characterized in that, In the hot rolling process: 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℃.

4. The method for producing non-oriented silicon steel according to claim 3, characterized in that, In the hot rolling process: the total reduction rate of finishing rolling is 90~96%, and the reduction rate of the last finishing rolling is 20~25%.

5. The method for producing non-oriented silicon steel according to claim 3, characterized in that, Hot rolling process: During heating, the temperature of the continuously cast billet entering the heating furnace is ≥350℃, and the soaking temperature is 1080~1150℃; 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.

6. The method for producing non-oriented silicon steel according to claim 3, characterized in that, Hot rolling process: After precision rolling, the coiling is carried out at a temperature of (600~650)±15℃.

7. The method for producing non-oriented silicon steel according to claim 1, characterized in that, Sour and continuous rolling process: The reduction rate of the final cold rolling pass is 15-25%.

8. The method for producing non-oriented silicon steel according to claim 1, characterized in that, Sourcing and rolling process: The surface roughness of the work rolls on the first and second stands of the multi-stand pickling and rolling mill is 1.00±0.20μm, the chamfer depth at the strip edge corresponding to the work rolls is 30~60μm, and the chamfer insertion amount is 70~100mm; the surface roughness of the work rolls on the third to fifth stands is 0.50±0.10μm, the chamfer depth at the strip edge corresponding to the work rolls is 10~15μm, and the chamfer insertion amount is 200~300mm.

9. The method for producing non-oriented silicon steel according to claim 1, characterized in that, Normalizing process of rolled hard sheet: The rolled hard sheet is normalized to allow the microstructure to recrystallize completely; the normalizing temperature is (850~1000)±10℃ and the normalizing time is 60~100s.

10. The method for producing non-oriented silicon steel according to claim 9, characterized in that, Normalizing process of rolled hard sheet: The chemical composition of the continuously cast billet, by mass percentage, satisfies Si+Al≥3.0%, and the normalizing temperature is (850~950)±10℃; Alternatively, the chemical composition of the continuously cast billet, by mass percentage, satisfies 2.0% < Si + Al < 3.0%, and the normalizing temperature is (900~980) ± 10℃; Alternatively, the chemical composition of the continuously cast billet, by mass percentage, satisfies Si+Al≤2.0% and the normalizing temperature is (950~1000)±10℃.

11. The method for producing non-oriented silicon steel according to claim 9, characterized in that, Normalizing process of rolled hard plate: After normalizing, 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 non-oriented silicon steel according to claim 1, characterized in that, Normalizing process of rolled hard sheet: tension in the normalizing furnace is 8~10 N / mm 2 The rolled hard sheet is normalized in a weakly reducing atmosphere, which is a mixture of H2 and N2, in which the volume percentage of H2 is 15-25%.

13. The method for producing non-oriented silicon steel according to claim 1, characterized in that, Single-stand cold rolling process: Cold rolling is performed without preheating. The reduction rate of the first cold rolling pass is ≥30% and the reduction amount is ≤0.40mm.

14. The method for producing non-oriented silicon steel according to claim 1, characterized in that, Single-stand precision cold rolling process: The single-stand rolling mill 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.

15. The method for producing non-oriented silicon steel according to claim 1, characterized in that, Annealing process: The cold-rolled steel sheet is annealed in an annealing furnace to allow the structure to recrystallize completely. The annealing temperature is 850~1050℃ and the annealing time is 100~120s.

16. The method for producing non-oriented silicon steel according to claim 15, characterized in that, Annealing process: The tension inside the annealing furnace is controlled at 1~3 N / mm. 2 .

17. The method for producing non-oriented silicon steel according to claim 15, characterized in that, Annealing process: After the annealing time is reached, temperature-controlled cooling is carried out. The cooling rate is 5~10℃ / s when the steel plate surface temperature is >700℃, 10~15℃ / s when the steel plate surface temperature is 400~700℃, and 15~20℃ / s when the steel plate surface temperature is <400℃.

18. The method for producing non-oriented silicon steel according to claim 15, characterized in that, 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.

19. The method for producing non-oriented silicon steel according to claim 1, characterized in that, Continuous casting process: The thickness of the continuously cast billet is 200~250mm, the equiaxed crystal ratio is ≥65%, and the concave depth of the narrow section is ≤3mm.

20. The method for producing non-oriented silicon steel according to claim 1, characterized in that, Continuous casting process: casting speed is controlled at 0.80~1.10m / min.

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