High-grade non-oriented silicon steel and normalizing-free short-process production method thereof

Abstract

The invention discloses high-grade non-oriented silicon steel and a normalizing-free short-process production method thereof. The production method comprises the following steps: heating, hot-rolling and coiling a continuous casting billet to obtain a hot-rolled plate with the thickness of 2.3-2.7 mm; acid pickling and cold rolling are carried out under the condition that normalizing is not carried out, and a primary cold-rolled plate with the thickness being 0.40-0.60 mm is obtained; performing intermediate annealing on the primary cold-rolled plate to obtain an intermediate annealed plate; the annealing temperature is (1195-8300 [Si]-2700 [Al] + / -10) DEG C, the heat preservation time is 300 d + 105 + / -10 s, [Si] and [Al] are the mass percent of Si and the mass percent of Al in the continuous casting billet respectively, d is the target thickness of a finished product, and the unit is mm; carrying out secondary cold rolling to obtain a secondary cold-rolled plate with the thickness of 0.15-0.30 mm; annealing a finished product, wherein the annealing temperature is 980-1000 DEG C; and cooling, coating and finishing are conducted, and a non-oriented silicon steel finished product is obtained.

Description

Technical Field

[0001] This application belongs to the field of steel material preparation technology, and relates to a high-grade non-oriented silicon steel and its production method with a short process that eliminates normalization. Background Technology

[0002] As new energy vehicle drive motors and low-altitude aircraft power systems continue to develop towards higher speeds and greater efficiency, more stringent requirements are being placed on the performance of high-grade non-oriented silicon steel, a core material for drive motors. In the future, the market demand for high-grade non-oriented silicon steel for new energy drive motors is bound to experience explosive growth.

[0003] Currently, the conventional process for producing high-grade non-oriented silicon steel is: hot rolling - normalizing - pickling - single-stand cold rolling - finished product annealing - coating. However, this conventional process faces severe challenges in actual production: normalizing treatment causes significant grain growth in the hot-rolled sheet, leading to microcracks at the strip edges during subsequent single-stand cold rolling due to uneven stress or decreased plasticity. These microcracks can rapidly propagate into strip breakage, severely restricting production efficiency and yield, and increasing production costs.

[0004] To address the issue of strip breakage during cold rolling of thin-gauge, high-grade non-oriented silicon steel, various technical solutions have been proposed in the industry. However, these solutions either fail to fundamentally solve the problem of high strip breakage rates caused by normalization, affecting production continuity and efficiency; or they sacrifice the simplicity and operability of the process flow to achieve specific properties, resulting in extremely complex production processes, high control difficulty, and lengthy procedures.

[0005] Therefore, developing a new method that is more adaptable to the thickness and shape of hot-rolled raw materials, has a simpler process flow, can achieve stable production, and produces products that meet the requirements for magnetic and mechanical properties has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, the purpose of this application is to provide a high-grade non-oriented silicon steel and a short-process production method for it that eliminates the need for normalization.

[0007] To achieve the above-mentioned objectives, one embodiment of this application provides a method for producing non-oriented silicon steel. The production method includes:

[0008] The continuously cast billet is sequentially heated, hot-rolled, and coiled to obtain a hot-rolled plate with a thickness of 2.3~2.7mm; Hot-rolled sheets are pickled and cold-rolled without normalization to obtain primary cold-rolled sheets with a thickness of 0.40~0.60mm; Intermediate annealing is performed on a cold-rolled sheet to obtain an intermediate annealed sheet; the annealing temperature is (T±10)℃, the holding time is t±10s, T=1195-8300[Si]-2700[Al], t=300d+105, where [Si] and [Al] are the mass percentages of Si and Al in the continuously cast billet, respectively, and d is the target thickness of the non-oriented silicon steel in mm. The intermediate annealed plate is subjected to a second cold rolling process to obtain a second cold-rolled plate with a thickness of 0.15~0.30mm; The secondary cold-rolled sheet is subjected to finished product annealing to obtain finished annealed sheet; the annealing temperature is 980~1000℃. The finished annealed plate is cooled, coated, and finished to obtain non-oriented silicon steel.

[0009] Preferably, during the annealing of the finished product, the holding time is not less than t-20s.

[0010] Preferably, a pickling and cold rolling process is used when pickling and cold rolling hot-rolled plates.

[0011] Preferably, a 20-roll single-stand cold rolling mill is used in the secondary cold rolling process, with 2 to 3 passes.

[0012] Preferably, no preheating is performed before pickling and cold rolling of hot-rolled plates; no preheating is performed before secondary cold rolling of intermediate annealed plates.

[0013] Preferably, when the continuously cast billet is heated, hot-rolled, and coiled in sequence, the soaking temperature is 1100±20℃, the final rolling temperature is 860±20℃, and the coiling temperature is 630±20℃.

[0014] Preferably, the chemical composition of the continuously cast billet, by mass percentage, includes: C≤0.003%, Si 2.8~3.5%, Mn0.2~1.0%, P≤0.050%, N≤0.010%, Al 0.3~1.5%, S≤0.0050%, Sb+Sn 0.001~0.085%, with the remainder being Fe and unavoidable impurities.

[0015] Preferably, the chemical composition of the continuously cast billet, by mass percentage, includes: C≤0.003%, Si 2.8~3.5%, Mn0.2~1.0%, P≤0.020%, N≤0.0020%, Al 0.85~1.5%, S≤0.0010%, Sb+Sn 0.001~0.085%, with the remainder being Fe and unavoidable impurities.

[0016] To achieve the above-mentioned objectives, one embodiment of this application provides a method for producing non-oriented silicon steel. The production method includes: The continuously cast billet is sequentially heated, hot-rolled, and coiled to obtain a hot-rolled plate with a thickness of 2.3~2.7mm; Hot-rolled sheets are pickled and cold-rolled without normalization to obtain primary cold-rolled sheets with a thickness of 0.40~0.60mm; A cold-rolled sheet is subjected to intermediate annealing to obtain an intermediate annealed sheet; wherein the grain size of the intermediate annealed sheet is controlled at 40~70µm. The intermediate annealed plate is subjected to a second cold rolling process to obtain a second cold-rolled plate with a thickness of 0.15~0.30mm; The secondary cold-rolled sheet is subjected to finished product annealing to obtain finished annealed sheet; the annealing temperature is 980~1000℃. The finished annealed plate is cooled, coated, and finished to obtain non-oriented silicon steel.

[0017] To achieve the aforementioned objectives, one embodiment of this application provides a non-oriented silicon steel. The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C ≤ 0.003%, Si 2.8~3.5%, Mn 0.2~1.0%, P ≤ 0.050%, N ≤ 0.010%, Al 0.3~1.5%, S ≤ 0.0050%, Sb+Sn 0.001~0.085%, with the remainder being Fe and unavoidable impurities; The thickness of the non-oriented silicon steel is 0.15~0.30mm, and the iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.60T.

[0018] Compared with existing technologies, this application adopts an innovative, non-routine, short-process technology—heating-hot rolling-coiling-pickling-cold rolling-intermediate annealing-secondary cold rolling-finished annealing-cooling-coating-finishing—which specifically solves the technical bottlenecks in the conventional production of high-grade non-oriented silicon steel for new energy applications. This technology offers the following significant advantages: On the one hand, as mentioned in the background art, for high-grade non-oriented silicon steel (especially when the total silicon and aluminum content is high), conventional processes require normalization treatment of hot-rolled plates. However, this reduces the plasticity of the strip and exacerbates strip breakage accidents during subsequent single-stand cold rolling, severely restricting production efficiency and yield. Consequently, this results in extremely stringent requirements for the thickness, crown, wedge shape, and "cat's ear" shape of the hot-rolled plate (usually requiring a thickness not exceeding 2.3 mm), increasing production difficulty. The process method of this application, however, through hot rolling... The elimination of normalizing treatment for the strip improves its plasticity when entering cold rolling and secondary cold rolling, eliminates the risk of strip breakage during cold rolling caused by coarse grains due to normalizing, and further reduces the requirements for the shape indicators of hot-rolled plates (including a significant increase in the upper limit of the thickness of hot-rolled plates, which can be relaxed to 2.7mm, and lower restrictions on defects such as convexity, wedge shape and "cat's ear"). It effectively reduces the losses caused by hot coils not meeting the normalizing furnace entry standards, and achieves a dual improvement in raw material utilization and production stability, with significant cost reduction and efficiency improvement effects. On the other hand, this application, through precise control of intermediate annealing, such as through a key control model of intermediate annealing temperature and holding time, or through control of the grain size of the intermediate annealing plate, ensures that the strip has sufficient toughness during the secondary cold rolling process, greatly reduces the risk of strip breakage, and ensures rollability, while also promoting grain growth as much as possible, laying the microstructure foundation for the excellent magnetic properties of the final annealed product, so that rolling stability and finished product magnetic properties can be synergistically optimized, thereby avoiding the inability to achieve both magnetic properties due to normalization. On the other hand, through the above-mentioned normalization-free path and precise intermediate annealing control, a more ideal recrystallization structure and texture can be obtained after the final product annealing than that of conventional normalization process. This not only meets the core requirements of new energy drive motors for high frequency, low iron loss and high magnetic induction, but also avoids the tendency of excessive grain coarsening and embrittlement caused by high temperature normalization. The mechanical properties of the product also meet the requirements of subsequent processing, achieving a dual guarantee of magnetic and mechanical properties. On the other hand, compared with the complex process of "normalization + first rolling + intermediate annealing + second rolling + finished product annealing" or even longer processes commonly found in the prior art, the process of this application is simplified and the production difficulty is greatly reduced. The upper limit requirement for the thickness of hot-rolled plates is relaxed, and the corresponding hot rolling efficiency, pickling efficiency and cold rolling efficiency can be greatly improved, making it more suitable for large-scale, high-efficiency industrial continuous production. Detailed Implementation

[0019] 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.

[0020] This application provides a non-oriented silicon steel and a method for producing the same, particularly a high-grade non-oriented silicon steel.

[0021] The production method includes: The continuously cast billet is sequentially heated, hot-rolled, and coiled to obtain a hot-rolled plate with a thickness of 2.3~2.7mm; Hot-rolled sheets are pickled and cold-rolled without normalization to obtain primary cold-rolled sheets with a thickness of 0.40~0.60mm; A cold-rolled sheet is subjected to intermediate annealing to obtain an intermediate annealed sheet; The intermediate annealed plate is subjected to a second cold rolling process to obtain a second cold-rolled plate with a thickness of 0.15~0.30mm; The secondary cold-rolled sheet is subjected to finished product annealing to obtain finished annealed sheet; the annealing temperature is 980~1000℃. The finished annealed plate is cooled, coated, and finished to obtain non-oriented silicon steel.

[0022] During intermediate annealing, the annealing temperature is (T±10)℃, the holding time is t±10s, T=1195-8300[Si]-2700[Al], t=300d+105, where [Si] and [Al] are the mass percentages of Si and Al in the continuously cast billet, respectively, and d is the target thickness of the non-oriented silicon steel in mm. And / or, the grain size of the intermediate annealing plate is controlled at 40~70µm during intermediate annealing.

[0023] Thus, this application, by adopting an innovative, non-routine, short-process technology—heating-hot rolling-coiling-pickling-cold rolling-intermediate annealing-secondary cold rolling-finished annealing-cooling-coating-finishing—specifically addresses the technical bottlenecks in the conventional production of high-grade non-oriented silicon steel for new energy applications, and has the following significant beneficial effects: On the one hand, as mentioned in the background art, for high-grade non-oriented silicon steel (especially when the total silicon and aluminum content is high), conventional processes require normalization treatment of hot-rolled plates. However, this reduces the plasticity of the strip and exacerbates strip breakage accidents during subsequent single-stand cold rolling, severely restricting production efficiency and yield. Consequently, this results in extremely stringent requirements for the thickness, crown, wedge shape, and "cat's ear" shape of the hot-rolled plate (usually requiring a thickness not exceeding 2.3 mm), increasing production difficulty. The process method of this application, however, through hot rolling... The elimination of normalizing treatment for the strip improves its plasticity when entering cold rolling and secondary cold rolling, eliminates the risk of strip breakage during cold rolling caused by coarse grains due to normalizing, and further reduces the requirements for the shape indicators of hot-rolled plates (including a significant increase in the upper limit of the thickness of hot-rolled plates, which can be relaxed to 2.7mm, and lower restrictions on defects such as convexity, wedge shape and "cat's ear"). It effectively reduces the losses caused by hot coils not meeting the normalizing furnace entry standards, and achieves a dual improvement in raw material utilization and production stability, with significant cost reduction and efficiency improvement effects. On the other hand, this application, through precise control of intermediate annealing, such as through a key control model of intermediate annealing temperature and holding time, or through control of the grain size of the intermediate annealing plate, ensures that the strip has sufficient toughness during the secondary cold rolling process, greatly reduces the risk of strip breakage, and ensures rollability, while also promoting grain growth as much as possible, laying the microstructure foundation for the excellent magnetic properties of the final annealed product, so that rolling stability and finished product magnetic properties can be synergistically optimized, thereby avoiding the inability to achieve both magnetic properties due to normalization. On the other hand, through the above-mentioned normalization-free path and precise intermediate annealing control, a more ideal recrystallization structure and texture can be obtained after the final product annealing than that of conventional normalization process. This not only meets the core requirements of new energy drive motors for high frequency, low iron loss and high magnetic induction, but also avoids the tendency of excessive grain coarsening and embrittlement caused by high temperature normalization. The mechanical properties of the product also meet the requirements of subsequent processing, achieving a dual guarantee of magnetic and mechanical properties. On the other hand, compared with the complex process of "normalization + first rolling + intermediate annealing + second rolling + finished product annealing" or even longer processes commonly found in the prior art, the process of this application is simplified and the production difficulty is greatly reduced. The upper limit requirement for the thickness of hot-rolled plates is relaxed, and the corresponding hot rolling efficiency, pickling efficiency and cold rolling efficiency can be greatly improved, making it more suitable for large-scale, high-efficiency industrial continuous production.

[0024] Specifically, in one embodiment, during intermediate annealing, the annealing temperature is (T±10)℃, the holding time is t±10s, T=1195-8300[Si]-2700[Al], and t=300d+105.

[0025] Where [Si] and [Al] are the mass percentages of Si and Al in the continuously cast billet, respectively. For example, if the mass percentage of Si in the continuously cast billet is 3.2%, the corresponding value of [Si] is 3.2%.

[0026] d represents the target thickness of the non-oriented silicon steel finished product, in mm. That is, intermediate annealing is controlled according to the target thickness of the non-oriented silicon steel to be produced.

[0027] Increasing the Si and Al content in non-oriented silicon steel promotes grain growth, increasing the risk of strip breakage in conventional processes. Within the process framework of this application—heating-hot rolling-coiling-pickling-cold rolling-intermediate annealing-secondary cold rolling-finished annealing-cooling-coating-finishing—the high silicon and high aluminum content of high-grade non-oriented silicon steel during intermediate annealing can further promote grain growth, easily leading to an increased risk of strip breakage, which in turn can result in poor magnetic properties in the final product. However, in this application, by precisely controlling the annealing temperature according to the Si and Al content and the holding time according to the target thickness of the finished product during intermediate annealing, precise control of the grain size of the intermediate annealed plate can be achieved. This not only avoids an increased risk of strip breakage but also ensures the magnetic properties of the final product, achieving a balance between rollability and magnetic performance.

[0028] From another perspective, by controlling the grain size of the intermediate annealing plate to 40~70µm during intermediate annealing, research has found that this not only avoids an increased risk of strip breakage but also ensures the magnetic properties of the final product, achieving a balance between rollability and magnetic properties.

[0029] More preferably, during intermediate annealing, the grain size of the intermediate annealing plate is controlled to be 50~70µm.

[0030] Specifically, the grain size of the intermediate annealing plate is controlled to be any value among 50µm, 51µm, 52µm, 53µm, 54µm, 55µm, 56µm, 57µm, 58µm, 59µm, 60µm, 61µm, 62µm, 63µm, 64µm, 65µm, 67µm, 68µm, 69µm, and 70µm.

[0031] Furthermore, in this application, the continuously cast billet can be prepared using any process in the art, such as steelmaking or continuous casting technology, and this application does not impose any restrictions.

[0032] The thickness of the continuously cast billet can be, for example, 200 mm or more, preferably 200-320 mm. For example, 220 mm.

[0033] Furthermore, preferably, the chemical composition of the continuously cast billet, by mass percentage, includes: C≤0.003%, Si 2.8~3.5%, Mn 0.2~1.0%, P≤0.050%, N≤0.010%, Al 0.3~1.5%, S≤0.0050%, Sb+Sn 0.001~0.085%, with the remainder being Fe and unavoidable impurities.

[0034] The basic functions and requirements of each element in this chemical composition are as follows.

[0035] C, S, and N: Harmful elements that generally hinder grain growth and magnetic domain movement by forming fine precipitates or segregating at grain boundaries, affecting the microstructure of materials and having a strong impact on mechanical and magnetic properties. In one embodiment, C ≤ 0.0030%, N ≤ 0.010%, and S ≤ 0.0050%; preferably, N ≤ 0.0020% and S ≤ 0.0010%.

[0036] Si: Silicon, after being dissolved in α-iron, increases resistivity and helps separate harmful impurities such as carbon. It also combines with oxygen to form stable SiO2, preventing lattice distortion in iron and promoting grain growth. Therefore, adding silicon can improve magnetic permeability, reduce coercivity, and decrease iron loss. However, increasing the silicon content makes the material harder and more brittle, especially when the silicon content exceeds 3.5%, resulting in poor thermal conductivity, decreased toughness, and band breakage. In this invention, the Si content is controlled at 2.8~3.5%.

[0037] Al: Its specific function is similar to that of Si, which can reduce iron loss, but has a smaller impact on the deterioration of magnetic induction. Al readily combines with N to form dispersed AlN precipitates, which remain in the solid solution, thereby increasing resistivity and promoting grain growth, thus improving the magnetic properties of silicon steel. However, adding too much Al will increase the difficulty of steelmaking. Therefore, the Al content in this invention is controlled at 0.3~1.5%, and more preferably at 0.85~1.5%.

[0038] Mn: A beneficial element in steel. In a low content range, it has a significant strengthening effect on steel, improving its strength, hardness, and wear resistance, while also improving its low-temperature toughness. However, it easily forms MnS compounds with S during solidification, which pin the grain boundaries and are not conducive to grain growth. Therefore, the Mn content in this invention is controlled at 0.20~1.0%. Sn and Sb: Sn and Sb segregate at grain boundaries, selectively inhibiting the growth of unfavorable {111} textured grains while enhancing favorable {100} and {110} textures, increasing magnetic induction intensity, reducing domain flipping resistance, and lowering hysteresis loss. As the Sn content increases, the iron loss value decreases, but exceeding 0.1% leads to increased brittleness and an increased risk of cold-rolled strip breakage. This invention controls the content within the range of 0.085%. Sb can effectively reduce iron loss through texture optimization and surface passivation. The high-frequency iron loss of high-grade non-oriented silicon steel for new energy applications is significantly reduced, but it must be strictly controlled below 0.05% to prevent excessive addition from leading to grain refinement and increased iron loss. Sn has a low cost and is generally added in combination with Sb to solve cost and high-frequency magnetic performance issues. In this invention, the weight of Sb+Sn is controlled between 0.001% and 0.085%.

[0039] Of course, within the process framework of this application, the chemical composition of the continuously cast billet is not limited to the above-mentioned composition, and other chemical compositions suitable for the production methods of this application may also be used.

[0040] Furthermore, in one embodiment, when the continuously cast billet is sequentially heated, hot-rolled, and coiled, the soaking temperature is 1100±20℃, the final rolling temperature is 860±20℃, and the coiling temperature is 630±20℃. Thus, by comprehensively controlling the various temperatures of the finishing rolling and the coiling temperature, it can be ensured that the internal structure of the hot-rolled coil obtained in the coiling process is a uniform hot-rolled deformed fibrous structure, while also guaranteeing the edge quality of the hot-rolled coil.

[0041] Specifically, the heat spread temperature is any one of the following values: 1080℃, 1082℃, 1084℃, 1085℃, 1086℃, 1087℃, 1088℃, 1089℃, 1090℃, 1092℃, 1093℃, 1094℃, 1095℃, 1098℃, 1100℃, 1101℃, 1103℃, 1104℃, 1105℃, 1108℃, 1110℃, 1112℃, 1115℃, 1117℃, 1118℃, and 1120℃.

[0042] The final rolling temperature of hot rolling is any one of the following values: 840℃, 841℃, 842℃, 843℃, 845℃, 847℃, 848℃, 850℃, 852℃, 854℃, 855℃, 858℃, 860℃, 861℃, 862℃, 865℃, 867℃, 868℃, 870℃, 872℃, 875℃, 878℃, and 880℃.

[0043] The winding temperature is any value among 610℃, 611℃, 612℃, 613℃, 615℃, 617℃, 618℃, 620℃, 622℃, 624℃, 625℃, 628℃, 630℃, 631℃, 632℃, 635℃, 637℃, 638℃, 640℃, 642℃, 645℃, 648℃, and 650℃.

[0044] Furthermore, a continuous pickling and cold rolling process is adopted when pickling and cold rolling hot-rolled plates. That is, a multi-stand continuous pickling and cold rolling unit is used for pickling and multiple passes. In this way, two or more hot-rolled plates are welded together end to end in sequence to achieve full-length rolling of the coil, which not only improves efficiency but also greatly increases the yield.

[0045] In addition, a 20-roll single-stand cold rolling mill is used in the secondary cold rolling process, with 2 to 3 passes. The work rolls of the 20-roll single-stand cold rolling mill have lower elastic deformation during the finishing cold rolling process (for example, only a few to tens of μm), which is more conducive to reducing the longitudinal variation of the steel plate thickness.

[0046] Preferably, no preheating is performed before pickling and cold rolling of the hot-rolled sheet; no preheating is performed before secondary cold rolling of the intermediate-annealed sheet. It is evident that the novel process of this application for preparing high-grade non-oriented silicon steel is less complex than conventional technologies, eliminating the need for preheating before cold rolling and before secondary cold rolling, thus improving production efficiency and reducing energy consumption.

[0047] Furthermore, during the annealing of the finished product, the holding time should not be less than t-20s. Here, t is calculated according to the aforementioned formula t=300d+105. This promotes sufficient grain growth during the annealing process, thereby further improving the microstructure and magnetic properties of the final product.

[0048] Preferably, the holding time during annealing of the finished product can be controlled within t ± 10 s. This not only improves the microstructure and magnetic properties of the final product but also ensures production efficiency and stability.

[0049] In addition, after the annealing process of the finished product in this application, cooling, coating, finishing and other processes can be carried out. These are all feasible technologies that can be implemented in this application, and are not the inventive points of this application, so they will not be introduced further.

[0050] Next, one embodiment of this application also provides a non-oriented silicon steel, which can be prepared by the aforementioned production method.

[0051] Understandably, the chemical composition of the non-oriented silicon steel can be the same as that of the aforementioned continuously cast billet, for example, by mass percentage including: C≤0.003%, Si 2.8~3.5%, Mn 0.2~1.0%, P≤0.050%, N≤0.010%, Al0.3~1.5%, S≤0.0050%, Sb+Sn in the range of 0.001~0.085%, with the remainder being Fe and unavoidable impurities.

[0052] Furthermore, the thickness of non-oriented silicon steel is 0.15~0.30mm, and the iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.60T.

[0053] More specifically, in one embodiment, the thickness of the non-oriented silicon steel is 0.15 mm, and the iron loss P 1.0 / 400 ≤10.00W / kg, magnetic induction intensity B 5000 ≥1.60T.

[0054] In another embodiment, the thickness of the non-oriented silicon steel is 0.20 mm, and the iron loss P 1.0 / 400 ≤11.50W / kg, magnetic induction intensity B 5000 ≥1.60T.

[0055] In another embodiment, the thickness of the non-oriented silicon steel is 0.25 mm, and the iron loss P 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.62T.

[0056] In another embodiment, the thickness of the non-oriented silicon steel is 0.30 mm, and the iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0057] It is evident that the non-oriented silicon steel of this application possesses excellent magnetic properties, meeting the industry and market requirements for the magnetic properties of high-grade non-oriented silicon steel.

[0058] In addition, in terms of mechanical properties, the yield strength of non-oriented silicon steel is ≥400MPa and the tensile strength is ≥500MPa.

[0059] Furthermore, the average grain size of the non-oriented silicon steel is 90±10µm.

[0060] In this application, it is understood that the dimensions, thicknesses, and other numerical values ​​mentioned should be interpreted in accordance with the common understanding of those skilled in the art. Given the prevalent production tolerances, measurement errors, and environmental factors in the materials processing field, those skilled in the art will understand that the stated numerical ranges (e.g., thickness 0.15~0.30 mm) substantially cover situations near those values ​​that conform to reasonable tolerances within industry standards or conventional manufacturing precision. In particular, for the thickness of cold-rolled sheets of non-oriented silicon steel, micron-level dimensional fluctuations are recognized and unavoidable.

[0061] In addition, in this application, the 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 Sheets" to obtain the grain size.

[0062] Sampling and sample preparation methods for the determination of chemical composition of steel and iron can be used to sample continuously cast billets or finished non-oriented silicon steel products, and the chemical composition of continuously cast billets or finished non-oriented silicon steel products can be tested according to GB / T 223 series "Methods for Chemical Analysis of Iron and Steel and Alloys".

[0063] 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.

[0064] The detailed description listed above is merely a specific description of the feasible implementation of this application. The specific implementation of this application will be described below through several specific embodiments and comparative examples to demonstrate the advantages and effects of this application.

[0065] For the first time, continuous casting billets from several heat numbers are provided in Table 1. The key elements in the chemical composition of the continuous casting billets are shown in Table 1, with the remainder being iron and unavoidable impurities. Furthermore, P, S, and N satisfy P ≤ 0.050%, N ≤ 0.010%, and S ≤ 0.0050%. In addition, " / " in the table indicates that the corresponding element was not intentionally added, and the corresponding element is 0 or exists as an impurity element and is close to 0.

[0066] [Table 1]

[0067] Next, using the continuously cast billets in Table 1 as the base material, non-oriented silicon steel products are prepared, wherein: Examples 1-7 all use the production method (i.e., heating-hot rolling-coiling-pickling-cold rolling-intermediate annealing-secondary cold rolling-finished annealing-cooling-coating-finishing process route) and process parameters provided in this application to prepare non-oriented silicon steel finished products; Comparative Examples 4-9, 11 and 12 adopted the process route of heating-hot rolling-coiling-pickling-cold rolling-intermediate annealing-secondary cold rolling-finished annealing-cooling-coating-finishing of this application, but at least one of the key parameters—intermediate annealing temperature and holding time—exceeded the design range of this application, and prepared non-oriented silicon steel finished products; some process parameters of Examples 1-7 and Comparative Examples 4-9 are shown in Table 2; Comparative Examples 1-3 and 10 adopted the conventional process route of heating-hot rolling-coiling-normalizing-pickling-cold rolling-finished annealing-cooling-coating-finishing to prepare non-oriented silicon steel products. Some process parameters of Comparative Examples 1-3 and 10 are shown in Table 3.

[0068] [Table 2]

[0069] [Table 3]

[0070] The production processes of Examples 1-3, Examples 5-7, Comparative Examples 1-9, and Comparative Examples 11-12 were statistically analyzed for strip breakage, as shown in Table 4. The "Number of Coils" column in the table represents the number of steel coils repeatedly implemented in each example / comparative example, and the "Number of Strip Breakages" represents the total number of strip breakages during the total number of coils implemented. Furthermore, samples of the non-oriented silicon steel products prepared in Examples 1-3, Examples 5-7, Comparative Examples 1-9, and Comparative Examples 11-12 were taken and their magnetic and mechanical properties were tested. The average values ​​of the results are shown in Table 4.

[0071] [Table 4]

[0072] Analysis based on Tables 1-4: First, Example 1 and Comparative Example 1 used the same continuous casting billet from the same furnace, Example 2 and Comparative Example 2 used the same continuous casting billet from the same furnace, and Example 3 and Comparative Example 3 used the same continuous casting billet from the same furnace. The difference is that Examples 1 to 3 used the technology of this application, while Comparative Examples 1 to 3 used the conventional production process of high-grade non-oriented silicon steel. After comparison, it can be seen that compared with Comparative Examples 1 to 3, Examples 1 to 3 not only have excellent magnetic and mechanical properties, but also have a significantly reduced number of strip breakages. Second, Examples 5 and Comparative Examples 4 and 7 used the same continuously cast billet from the same furnace, Examples 6 and Comparative Examples 5 and 8 used the same continuously cast billet from the same furnace, and Examples 7 and Comparative Examples 6 and 9 used the same continuously cast billet from the same furnace. The difference is that Examples 5 to 7 used the technology of this application, while Comparative Examples 4 to 6 used a higher intermediate annealing temperature, and Comparative Examples 7 to 9 used a longer intermediate annealing holding time. It can be seen from the comparison that under the process route of heating-hot rolling-coiling-pickling-cold rolling-intermediate annealing-secondary cold rolling-finished annealing-cooling-coating-finishing of this application, a longer intermediate annealing temperature or holding time will lead to a higher risk of strip breakage, but the probability of strip breakage is lower than that of conventional technologies (such as Comparative Examples 1 to 3). Third, Example 1 and Comparative Examples 11 and 12 use the same continuously cast billet from the same furnace. The difference is that Comparative Examples 11 and 12 use lower intermediate annealing temperatures and holding times, respectively. It can be seen from the comparison that under the process route of heating-hot rolling-coiling-pickling-cold rolling-intermediate annealing-secondary cold rolling-finished annealing-cooling-coating-finishing in this application, insufficient intermediate annealing temperature or holding time will result in low magnetic properties. Fourth, the grain size of the intermediate annealing plates in Examples 1-3 and 5-7 is 40-70 μm, while the grain size of the intermediate annealing plates in Comparative Examples 4-9 exceeds 70 μm, and the grain size of the intermediate annealing plates in Comparative Examples 11-12 is less than 40 μm.

[0073] Furthermore, in Example 4 and Comparative Example 10, a comparative experiment was conducted on the correlation between the shape of the hot-rolled plate and the strip breakage. Specifically, as shown in Table 5, in Example 4 and Comparative Example 10, based on the number of steel coils, the corresponding "type" of hot-rolled plate shape of these steel coils met the "range", and the "average value" and "total number of strip breaks" of this "type" of these steel coils were statistically analyzed.

[0074] Taking "convexity" as an example to illustrate the specific statistical method: In Example 4, 20 hot-rolled steel coils with a "convexity" between 50 and 60 µm were statistically analyzed, and the average "convexity" of these 20 steel coils was 58.43 µm, and the total number of strip breaks in these 20 steel coils during production was 2; correspondingly, in Comparative Example 10, 20 hot-rolled steel coils with a "convexity" between 50 and 60 µm were statistically analyzed, and the average "convexity" of these 20 steel coils was 57.94 µm, and the total number of strip breaks in these 20 steel coils during production was 10.

[0075] In Table 5, the statistical methods for other plate shapes, such as "wedge", "cat's ear", and "thickness", are similar to those for "convexity" above. This is easy for those skilled in the art to understand and will not be explained further.

[0076] [Table 5]

[0077] Furthermore, in this application, the "convexity" of a hot-rolled sheet refers to the difference between the average thickness at the center of the cross-section of the hot-rolled sheet and the average thickness at a specific distance from the two sides (this distance is usually selected according to product specifications, such as 25mm or 40mm, to exclude interference from the thinned areas at the edges). Generally, it is desirable for the "convexity" of the hot-rolled sheet to be as small as possible during production.

[0078] The "wedge shape" of a hot-rolled sheet is a manifestation of the asymmetry in the transverse thickness difference of the sheet. It represents the difference in thickness between corresponding positions on the transmission side and the operating side of the hot-rolled sheet's cross-section (usually at the same distance from both edges). Generally, it is desirable for the "wedge shape" of the hot-rolled sheet to be as small as possible during production.

[0079] The "cat's ear" effect in hot-rolled steel refers to a localized, asymmetrical, and rapid increase in thickness that occurs at the edges of the strip during the hot-rolling process. It is named for its cross-sectional profile, which resembles a cat's ear. Generally, it is desirable for the "cat's ear" effect in hot-rolled steel to be as small as possible during production.

[0080] Based on the above explanations of the concepts of "convexity", "wedge", and "cat's ear", those skilled in the art can clearly understand the statistical method used in Table 5 for Example 4 and Comparative Example 10; of course, even without these explanations, if Example 4 and Comparative Example 10 are statistically analyzed using the same standard, a comparison of the probability of tape breakage can be obtained.

[0081] Specifically, as shown in Table 5, when the hot-rolled plates have essentially the same shape issues and large plate thickness: Example 4, produced according to the process route and parameters of this application, still has a low number of strip breakages, while in contrast, Comparative Example 10, which uses a conventional process, sees a surge in strip breakages. This proves that even when the hot-rolled plate's crown, wedge shape, and other indicators fluctuate significantly (such as the high strip breakage risk area shown in Comparative Example 10), the process of this application (Example 4) can still maintain a low strip breakage rate, ensuring smooth production. It is evident that, compared to the prior art, the production method of this application can significantly reduce the requirements for the hot-rolled plate's shape. From the perspective of low strip breakage risk and smooth production, it has a high tolerance for abnormal hot-rolled plate shape. For example, it can tolerate larger hot-rolled plate crown, more severe hot-rolled plate wedge shape abnormalities and cat-ear abnormalities, and allows for larger hot-rolled plate thicknesses (without strictly limiting the thickness of the hot-rolled plate), greatly reducing production difficulty.

Claims

1. A method for producing non-oriented silicon steel, characterized in that, The production method includes: The continuously cast billet is sequentially heated, hot-rolled, and coiled to obtain a hot-rolled plate with a thickness of 2.3~2.7mm; Hot-rolled sheets are pickled and cold-rolled without normalization to obtain primary cold-rolled sheets with a thickness of 0.40~0.60mm; Intermediate annealing is performed on a cold-rolled sheet to obtain an intermediate annealed sheet; the annealing temperature is (T±10)℃, the holding time is t±10s, T=1195-8300[Si]-2700[Al], t=300d+105, where [Si] and [Al] are the mass percentages of Si and Al in the continuously cast billet, respectively, and d is the target thickness of the non-oriented silicon steel in mm. The intermediate annealed plate is subjected to a second cold rolling process to obtain a second cold-rolled plate with a thickness of 0.15~0.30mm; The secondary cold-rolled sheet is subjected to finished product annealing to obtain finished annealed sheet; the annealing temperature is 980~1000℃. The finished annealed plate is cooled, coated, and finished to obtain non-oriented silicon steel.

2. The method for producing non-oriented silicon steel according to claim 1, characterized in that, When annealing the finished product, the holding time should not be less than t-20s.

3. The method for producing non-oriented silicon steel according to claim 1, characterized in that, When hot-rolled plates are pickled and cold-rolled, a continuous pickling and rolling process is used.

4. The method for producing non-oriented silicon steel according to claim 1, characterized in that, The secondary cold rolling process uses a 20-roll single-stand cold rolling mill, with 2 to 3 passes.

5. The method for producing non-oriented silicon steel according to claim 1, characterized in that, No preheating is performed before pickling and cold rolling of hot-rolled plates; no preheating is performed before secondary cold rolling of intermediate annealed plates.

6. The method for producing non-oriented silicon steel according to claim 1, characterized in that, When continuously cast billets are heated, hot rolled, and coiled in sequence, the soaking temperature is 1100±20℃, the final rolling temperature is 860±20℃, and the coiling temperature is 630±20℃.

7. 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: C≤0.003%, Si 2.8~3.5%, Mn 0.2~1.0%, P≤0.050%, N≤0.010%, Al 0.3~1.5%, S≤0.0050%, Sb+Sn 0.001~0.085%, with the remainder being Fe and unavoidable impurities.

8. The method for producing non-oriented silicon steel according to claim 7, characterized in that, The chemical composition of the continuously cast billet, by mass percentage, includes: C≤0.003%, Si 2.8~3.5%, Mn 0.2~1.0%, P≤0.020%, N≤0.0020%, Al 0.85~1.5%, S≤0.0010%, Sb+Sn 0.001~0.085%, with the remainder being Fe and unavoidable impurities.

9. A method for producing non-oriented silicon steel, characterized in that, The production method includes: The continuously cast billet is sequentially heated, hot-rolled, and coiled to obtain a hot-rolled plate with a thickness of 2.3~2.7mm; Hot-rolled sheets are pickled and cold-rolled without normalization to obtain primary cold-rolled sheets with a thickness of 0.40~0.60mm; A cold-rolled sheet is subjected to intermediate annealing to obtain an intermediate annealed sheet; wherein the grain size of the intermediate annealed sheet is controlled at 40~70µm. The intermediate annealed plate is subjected to a second cold rolling process to obtain a second cold-rolled plate with a thickness of 0.15~0.30mm; The secondary cold-rolled sheet is subjected to finished product annealing to obtain finished annealed sheet; the annealing temperature is 980~1000℃. The finished annealed plate is cooled, coated, and finished to obtain non-oriented silicon steel.

10. A non-oriented silicon steel, characterized in that, The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C≤0.003%, Si 2.8~3.5%, Mn 0.2~1.0%, P≤0.050%, N≤0.010%, Al 0.3~1.5%, S≤0.0050%, Sb+Sn 0.001~0.085%, with the remainder being Fe and unavoidable impurities; The thickness of the non-oriented silicon steel is 0.15~0.30mm, and the iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.60T.

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