Ultra-thin high-grade non-oriented silicon steel and acid continuous rolling coordinated with twenty-roll finish cold rolling full-process production method

Abstract

This application discloses a complete production method for ultra-thin high-grade non-oriented silicon steel and its acid continuous rolling combined with 20-roll precision cold rolling. The thickness of the non-oriented silicon steel is (0.05~0.15)±0.002mm. The production method includes: heating: homogenization temperature 1000~1140℃; hot rolling: the initial rolling temperature of the first finishing rolling pass ≥950℃, the final rolling temperature of the last finishing rolling pass 850±15℃, and the hot-rolled plate thickness 1.80~2.30mm; coiling temperature 630±15℃; pickling and continuous cold rolling: pickling and multi-pass continuous cold rolling are performed using a multi-stand pickling and continuous cold rolling mill, and the hardened plate thickness is 0.2~0.35mm; normalizing the hardened plate: normalizing the hardened plate in a normalizing furnace to obtain a normalized hardened plate; normalizing temperature 850~950℃; 20-roll cold finishing; annealing: annealing temperature 900~1000℃, annealing time 40~120s.

Description

Technical Field

[0001] This application belongs to the field of steel material preparation technology, and relates to an ultra-thin high-grade non-oriented silicon steel, and a production method of ultra-thin high-grade non-oriented silicon steel, especially a whole-process production method of ultra-thin high-grade non-oriented silicon steel by acid continuous rolling combined with twenty-roll precision cold rolling. Background Technology

[0002] With the acceleration of global electrification and the booming development of the new energy industry, the requirements for high efficiency, energy saving, high speed, high power density, and lightweight of electrical equipment are increasing. In order to meet the needs of high efficiency, high speed, high power density, and lightweight, non-oriented silicon steel should have characteristics such as low loss at medium and high frequencies, high magnetic induction, and ultra-thinness.

[0003] Non-oriented silicon steel with a thickness of 0.15 mm or less is classified as ultra-thin non-oriented silicon steel and is mainly used in medium- and high-frequency applications at 400 Hz and above. As an excellent soft magnetic material, ultra-thin non-oriented silicon steel is primarily used as a core material in fields such as power electronics, military industry, new energy vehicles, and low-altitude economy.

[0004] Currently, there are three main methods for preparing ultra-thin non-oriented silicon steel.

[0005] The first method is twin-roll continuous casting. For example, Chinese patent application number 201810441471.4 describes casting molten steel into a thin strip with a thickness of 1.0~4.0 mm using a twin-roll thin strip casting machine; when the strip temperature drops to 800~1200℃, it is hot-rolled to obtain a hot-rolled thin strip; then, after three cold rolling cycles and three annealing cycles, a non-oriented silicon steel ultra-thin strip with a thickness of 0.05~0.20 mm is produced. In this method, the casting and rolling speed is much lower than that of conventional continuous casting + hot rolling, and it requires three cold rolling cycles and three annealing cycles, resulting in very low overall production efficiency and high production costs.

[0006] The second method is planar flow casting. For example, Chinese patent application number 202310981198.5 uses pure iron and high-purity silicon as raw materials, melting them and casting them into a master alloy ingot. This ingot is then placed in a heating device with a nozzle at the bottom for further melting. The melt is then sprayed through the nozzle onto a high-speed rotating copper roller, where it solidifies naturally to form a non-oriented silicon steel ultra-thin strip with a thickness of 0.03~0.16mm. This method can only produce strips 1~15mm wide, resulting in extremely low production efficiency and high production costs. Furthermore, it cannot produce wide-specification products, making it difficult to meet actual industrial needs.

[0007] The third method is the traditional continuous casting-hot rolling-normalizing-multiple cold rolling + multiple annealing method. For example, Chinese patent application No. 202410879950.X describes the process of continuous casting, hot rolling, normalizing, pickling, cold rolling, annealing, secondary cold rolling, and secondary annealing to produce ultra-thin non-oriented silicon steel with a thickness of (0.10~0.15)±0.005mm. In this method, normalizing the hot-rolled plate is a necessary step to ensure magnetic properties. However, normalizing the hot-rolled plate significantly increases the difficulty of subsequent cold rolling. Therefore, preheating is required before the second cold rolling. For example, Chinese patent application 202410879950.X requires preheating to 80~120℃, otherwise edge cracking or even strip breakage may occur during cold rolling. Preheating before cold rolling leads to a longer process and higher costs. Furthermore, in order to reduce the risk of strip breakage during cold rolling, auxiliary technologies such as low thickness of the hot-rolled plate and large reduction in the first pass of cold rolling are required. However, this will cause problems such as high production difficulty of hot rolling, high production difficulty of cold rolling, high equipment requirements, and low production efficiency. Summary of the Invention

[0008] To address the aforementioned technical problems, the purpose of this application is to provide an ultra-thin high-grade non-oriented silicon steel, and a method for producing ultra-thin high-grade non-oriented silicon steel, particularly a complete production method for ultra-thin high-grade non-oriented silicon steel using acid continuous rolling combined with 20-roll precision cold rolling.

[0009] To achieve the aforementioned objectives, one embodiment of this application provides a method for producing ultra-thin high-grade non-oriented silicon steel. The production method includes:

[0010] Heating process: The continuously cast billet is heated in a heating furnace at a soaking temperature of 1000~1140℃;

[0011] Hot rolling process: The continuously cast billet is subjected to multiple passes of rough rolling and multiple passes of finish rolling; wherein, the thickness of the intermediate billet obtained by rough rolling is 30~40mm, the starting rolling temperature of the first pass of finish rolling is ≥950℃, the final rolling temperature of the last pass of finish rolling is 850±15℃, and the thickness of the hot rolled plate obtained by finish rolling is 1.80~2.30mm.

[0012] Coiling process: The hot-rolled plate is coiled to obtain a hot-rolled coil at a temperature of 630±15℃.

[0013] Pickling and continuous cold rolling process: The hot-rolled coil is leveled and then pickled and continuously cold rolled in multiple passes using a multi-stand pickling and continuous cold rolling unit to obtain a hardened plate with a thickness of 0.2~0.35mm;

[0014] Normalizing process of rolled hard sheet: The rolled hard sheet is normalized in a normalizing furnace to obtain normalized rolled hard sheet; the normalizing temperature is 850~950℃;

[0015] Twenty-roll precision cold rolling process: A twenty-roll single-stand cold rolling mill is used to perform precision cold rolling on normalized rolled hard plates to obtain precision cold-rolled plates with a thickness of (0.05~0.15)±0.002mm;

[0016] Annealing process: The cold-rolled steel sheet is annealed in an annealing furnace at a temperature of 900~1000℃ for 40~120s, and then cooled to obtain the non-oriented silicon steel finished product.

[0017] As a further improvement to one implementation method, in the normalizing process of the rolled hard sheet: the tension in the normalizing furnace is 8~10 N / mm. 2 .

[0018] As a further improvement to one implementation method, in the annealing process: the tension inside the annealing furnace is controlled at 1~3 N / mm. 2 .

[0019] As a further improvement to one implementation method, the annealing process is as follows: the annealing temperature is T ± 10℃, and the annealing time is (30~50) s + 400h s / mm, where h is the thickness of the cold-rolled plate in mm; the unit of T is ℃, and its value is taken from the formula 820 + 200(11Si - 14Mn + 21Al) + 400h mm -1 The element symbols in the formula represent the mass percentage of the corresponding element in the continuously cast billet.

[0020] As a further improvement to one implementation method, the normalization process of the rolled hard plate is as follows: normalization time is 60~100s; after the normalization time is reached, temperature-controlled cooling is performed, with a cooling rate of 10~15℃ / s when the steel plate surface temperature is ≥400℃ and a cooling rate of 15~20℃ / s when the steel plate surface temperature is <400℃.

[0021] As a further improvement to one implementation method, the twenty-roll precision cold rolling process involves 2 to 4 passes of precision cold rolling with a total reduction rate of 40 to 80%, and the reduction rate of the first pass of precision cold rolling is ≥30%.

[0022] As a further improvement to one implementation method, in the acid rolling process: the reduction rate of the first cold rolling pass is 20~30%, and the reduction amount is ≤0.60mm; the bending force of the working rolls of each stand in the acid rolling process is controlled at 50~150kN, so that the edge of the resulting hardened plate produces a controllable edge wave with a height of 1.0~2.5mm.

[0023] As a further improvement to one implementation method, in the hot rolling process: the total reduction rate of finishing rolling is 93-95%, and the reduction rate of the final finishing rolling is 20-25%.

[0024] As a further improvement to one implementation method, there is no normalization before the acid rolling process;

[0025] Pickling and continuous rolling process: After pickling, multiple passes of continuous cold rolling are carried out directly without preheating;

[0026] Twenty-roll precision cold rolling process: No preheating is required before precision cold rolling.

[0027] As a further improvement to one implementation method, the annealing process involves: after reaching the required annealing time, 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℃.

[0028] As a further improvement to one embodiment, the twenty-roll finishing cold rolling process: the working roll diameter of the twenty-roll single-stand cold rolling mill is 45~65mm, the roughness of the working roll used for the first finishing cold rolling is 2.50±0.50μm, and the roughness of the working roll used for the last finishing cold rolling is 0.50±0.10μm.

[0029] As a further improvement to one embodiment, the acid rolling process: the multi-stand acid rolling mill used is any one of a six-roll five-stand acid rolling mill, a six-roll six-stand acid rolling mill, or an eighteen-roll six-stand acid rolling mill.

[0030] As a further improvement to one implementation method, the heating process involves holding the continuously cast billet at a homogenization temperature for 40-60 minutes.

[0031] As a further improvement to one embodiment, the thickness of the continuously cast billet is 200~250mm;

[0032] The chemical composition of the continuously cast billet, by mass percentage, includes: C≤0.005%, Si:3.2~3.7%, Mn:0.3~0.8%, Al:0.70~1.2%, S≤0.01%, P≤0.08%, N≤0.01%, O≤0.01%, Cr, Ni and Cu ≤5.0% respectively, Mo, Nb, V and Ti ≤0.1% respectively, and the remainder being Fe and unavoidable inclusions.

[0033] As a further improvement of one embodiment, the chemical composition of the continuously cast billet, by mass percentage, satisfies any one or more of the following: C≤0.0025%, S≤0.0015%, P≤0.03%, N≤0.003%, O≤0.003%, Nb≤0.004%, V≤0.004%, Ti≤0.005%, Mo≤0.004%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, Nb+V+Ti+Mo≤0.009%, and / or, Cr+Ni+Cu≤0.06%.

[0034] To achieve the aforementioned objectives, one embodiment of this application provides an ultra-thin, high-grade non-oriented silicon steel. The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C ≤ 0.005%, Si: 3.2~3.7%, Mn: 0.3~0.8%, Al: 0.70~1.2%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni, and Cu ≤ 5.0% each, Mo, Nb, V, and Ti ≤ 0.1% each, with the remainder being Fe and unavoidable inclusions.

[0035] The thickness h of the non-oriented silicon steel is (0.05~0.15)±0.002mm, and its recrystallized grain size is 500h~1000h μm / mm;

[0036] The iron loss P of the non-oriented silicon steel 1.0 / 400 ≤9.5W / kg, iron loss P 0.5 / 1000 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0037] As a further improvement to one embodiment, the thickness of the non-oriented silicon steel is 0.05±0.002mm, and the iron loss P 1.0 / 400 ≤8.0W / kg, iron loss P 0.5 / 1000 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T;

[0038] Alternatively, the thickness of the non-oriented silicon steel is 0.08±0.002mm, and the iron loss P 1.0 / 400 ≤8.5W / kg, iron loss P 0.5 / 1000 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.63T;

[0039] Alternatively, the thickness of the non-oriented silicon steel is 0.10±0.002mm, and the iron loss P 1.0 / 400 ≤9.0W / kg, iron loss P 0.5 / 1000 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.63T;

[0040] Alternatively, the thickness of the non-oriented silicon steel is 0.15±0.002mm, 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.

[0041] As a further improvement to one embodiment, the chemical composition of the non-oriented silicon steel further includes, by mass percentage, any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%.

[0042] Compared with the prior art, the beneficial effects of this application include:

[0043] On the one hand, compared with the three existing preparation methods of ultra-thin non-oriented silicon steel, this application adopts a brand-new process of heating-hot rolling-coiling-acid continuous rolling-hardening-20-roll precision cold rolling-annealing to prepare ultra-thin non-oriented silicon steel from continuous casting billets. The entire process has low production cost, high production efficiency, low production difficulty, and low equipment requirements. Moreover, the width of the obtained non-oriented silicon steel product can meet most practical needs and has excellent performance, including but not limited to low iron loss and high magnetic induction intensity.

[0044] On the other hand, compared with the traditional continuous casting-hot rolling-normalizing-multiple cold rolling + multiple annealing methods, this application eliminates the need for normalizing the hot-rolled plate. This allows the hot-rolled deformed fiber structure to be retained during cold rolling, reducing the difficulty of cold rolling and enabling rapid, efficient, and smooth production in the acid-rolling process. Furthermore, by controlling the normalizing of the hardened plate, the grain size and microstructure of the normalized hardened plate are optimized, further improving rollability and ensuring rapid and smooth 20-roll precision cold rolling. This ensures smooth plate passage throughout the process, avoiding edge cracks and strip breaks. Moreover, the reduced difficulty of cold rolling leads to a corresponding reduction in the thickness requirements of the hot-rolled plate, further lowering the production difficulty of hot rolling. In summary, this reduces the overall production difficulty and cost while improving overall production efficiency.

[0045] On the other hand, in conjunction with the foregoing, although this application does not normalize the hot-rolled plate, it does not reduce the magnetic properties. On the contrary, it can improve the magnetic properties compared with the prior art. For example, through the hot rolling process and the acid continuous rolling process, a deformed fibrous ferrite structure is formed. Then, through the normalization process of the hardened plate, the deformed fibrous ferrite undergoes complete recrystallization, achieving coarsening and homogenization of the structure. At the same time, since the thickness of the hardened plate is thin, the difficulty of subsequent precision cold rolling is significantly reduced. Therefore, for high-grade non-oriented silicon steel with the same composition, the normalization temperature of the hardened plate is higher, which is conducive to the growth of recrystallized grains. Combined with the control of subsequent annealing temperature and annealing time, the size of recrystallized grains is increased and the unfavorable texture {111} is reduced, and magnetic properties far superior to those of the prior art can be obtained under the same chemical composition. In addition, due to the reduction in production difficulty, it is not necessary to strictly control the upper limit of Si and Al content as in the prior art. That is, the Si and Al content can be increased, and the promoting effect of chemical composition on performance can be fully utilized, thus making the improvement of magnetic properties possible. Detailed Implementation

[0046] 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.

[0047] [First Implementation Method]

[0048] This embodiment provides an ultra-thin high-grade non-oriented silicon steel.

[0049] The thickness h of the non-oriented silicon steel is (0.05~0.15)±0.002mm. As mentioned in the background art, non-oriented silicon steel of this thickness belongs to the category of ultra-thin steel plates. As an excellent soft magnetic material, it is used in medium and high frequency operating conditions of 400Hz and above, such as core materials in fields such as power electronics, military industry, new energy vehicles and low-altitude economy.

[0050] The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C ≤ 0.005%, Si: 3.2~3.7%, Mn: 0.3~0.8%, Al: 0.70~1.2%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni, and Cu ≤ 5.0% each, Mo, Nb, V, and Ti ≤ 0.1% each, with the remainder being Fe and unavoidable inclusions. This chemical composition meets the production requirements of ultra-thin, high-grade non-oriented silicon steel and also has the advantages of low production difficulty and low production cost.

[0051] It should be noted that, unless otherwise stated, the element "content" in the chemical composition of this application means the mass percentage of the corresponding element.

[0052] The following section provides a detailed explanation of the role and mechanism of each chemical element in the chemical composition.

[0053] 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%.

[0054] 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 3.2~3.7%.

[0055] 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 0.3~0.8%.

[0056] Al is an effective additive element for improving resistivity and reducing iron loss. 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 the cold rolling process. In this application, in order to ensure magnetic properties and smooth plate passage, the Al content is controlled at 0.70~1.2%.

[0057] 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 0.003% or less. More preferably, in yet another embodiment, the S content can be further controlled to ≤0.0015%.

[0058] 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%.

[0059] Nitrogen (N) is a harmful element that must be avoided in non-oriented silicon steel. Its presence hinders grain growth by forming AlN precipitation and induces magnetic aging, fundamentally degrading the magnetic properties of the material. Therefore, in this application, the N content is controlled at ≤0.01%. Preferably, in some embodiments, the N content is further controlled to N≤0.003%.

[0060] Oxygen (O) is a harmful element that needs to be removed and avoided in non-oriented silicon steel. It can significantly negatively affect the magnetic properties and performance of the material through various pathways, such as forming harmful inclusions, causing lattice distortion, and inducing internal oxidation. Therefore, in this application, the O content is controlled at ≤0.01%. Preferably, in some embodiments, O ≤0.003%.

[0061] Cr, Ni, Cu: In non-oriented silicon steel, Cr, Ni, and Cu are all non-essential elements, and are only added when high strength is required. Therefore, in this application, Cr, Ni, and Cu are each controlled to ≤5.0%. Preferably, in some embodiments where high strength is not required, the content of any one or more of Cr≤0.03%, Ni≤0.03%, and Cu≤0.03% can be further controlled. More preferably, in some embodiments, to avoid the deteriorating effect of the superposition of Cr, Ni, and Cu on magnetic properties, the content of Cr+Ni+Cu can be further controlled to ≤0.06%.

[0062] Nb and V: As carbide and nitride forming elements, their fine precipitates can improve strength, but they can hinder the growth of finished grains during annealing. In this application, the content of Nb and V is controlled at ≤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%.

[0063] Mo: In non-oriented silicon steel, Mo is a non-essential element, and it is only added when good mechanical properties at high temperatures are desired. Furthermore, excessive Mo content can deteriorate magnetic properties. In this application, the Mo content is controlled at ≤0.1%. Preferably, in some embodiments, to avoid significantly refining the grains and deteriorating magnetic properties due to increased Mo content, the Mo content is controlled at 0.005% or less. More preferably, Mo ≤0.004%.

[0064] 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%.

[0065] More preferably, in some embodiments, in order to avoid the deterioration effect of the superposition of Nb, V, Mo and Ti on the magnetic properties, Nb+V+Ti+Mo≤0.009%.

[0066] Regarding the chemical composition, the impurities include, but are not limited to, elements such as Mg, B, Zr, W, Bi, Ca, and rare earth elements. The content of these impurity elements can be controlled within any feasible range in the art. This application does not limit the specific elements and content of the impurities.

[0067] Furthermore, in some embodiments, the non-oriented silicon steel may further contain either or both of Sn and Sb.

[0068] 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.

[0069] 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.

[0070] For example, in some embodiments, the chemical composition of the non-oriented silicon steel contains both Sn and Sb, with the Sn content controlled within the range of 0.02 to 0.07% and the Sb content controlled within the range of 0.02 to 0.07%.

[0071] In this application, the recrystallized grain size of the non-oriented silicon steel is 500h~1000h μm / mm. Wherein, h is the thickness of the non-oriented silicon steel, in mm.

[0072] That is, the grain size is 0.5 to 1.0 times the thickness h of the non-oriented silicon steel. In this way, when observed after metallographic etching on a cross section perpendicular to the rolling surface, the average number of grain layers in the thickness direction does not exceed 2 layers, for example, the number of grain layers is 1 to 2 layers, so as to ensure that the finished non-oriented silicon steel has both excellent magnetic properties and processing performance.

[0073] Furthermore, research has shown that if the grain size is too large, the number of grain boundaries decreases, reducing the pinning resistance encountered during domain wall movement, which is detrimental to domain stability and leads to a decrease in magnetic properties. Simultaneously, excessively large grain sizes increase the material's brittleness, making it prone to microcracks during processing, which increase hysteresis losses. Conversely, if the grain size is too small, the number of grain boundaries increases dramatically, leading to a sharp increase in pinning resistance during domain wall movement, resulting in increased hysteresis losses and similarly a decrease in magnetic properties. The non-oriented silicon steel of this application, with a grain size controlled between 500h and 1000h μm / mm, significantly improves magnetic properties while maintaining the steel plate's machinability.

[0074] Furthermore, the iron loss P of the non-oriented silicon steel 1.0 / 400 ≤9.5W / kg, iron loss P 0.5 / 1000 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0075] For example, in some embodiments, the thickness of the non-oriented silicon steel is 0.05±0.002mm, and the iron loss P 1.0 / 400 ≤8.0W / kg, iron loss P 0.5 / 1000 ≤12.0W / kg, magnetic induction intensity B5000 ≥1.63T.

[0076] In some embodiments, the thickness of the non-oriented silicon steel is 0.08±0.002mm, and the iron loss P 1.0 / 400 ≤8.5W / kg, iron loss P 0.5 / 1000 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0077] In some other embodiments, the thickness of the non-oriented silicon steel is 0.10 ± 0.002 mm, and the iron loss P 1.0 / 400 ≤9.0W / kg, iron loss P 0.5 / 1000 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0078] In some embodiments, the thickness of the non-oriented silicon steel is 0.15 ± 0.002 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.

[0079] 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 of non-oriented silicon steel, including iron loss and magnetic induction intensity.

[0080] In addition to magnetic properties, the non-oriented silicon steel of this application also has excellent plate shape and thickness accuracy.

[0081] Specifically, the longitudinal thickness fluctuation of the non-oriented silicon steel is ≤ ±2 μm, and the transverse thickness difference is ≤ 3 μm. In this application, the longitudinal thickness fluctuation and transverse thickness difference can be obtained by sampling and measuring the non-oriented silicon steel according to GB / T 708-2019 "Dimensions, Shapes, Weights and Permissible Deviations of Cold-Rolled Steel Sheets and Strips".

[0082] The flatness of the non-oriented silicon steel is ≤1.50mm / 1000mm. In this application, the flatness 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".

[0083] In summary, the non-oriented silicon steel of this embodiment has the advantages of being ultra-thin, having low iron loss, and high magnetic induction, and it also has the advantages of being easy to produce and having low production costs.

[0084] [Second Implementation Method]

[0085] This embodiment provides a method for producing non-oriented silicon steel. This method can be used to prepare an ultra-thin, high-grade non-oriented silicon steel, such as the non-oriented silicon steel described in the first embodiment above, but is not limited thereto.

[0086] Specifically, the production method includes a heating process, a hot rolling process, a coiling process, an acid continuous rolling process, a hardened plate normalizing process, a 20-roll precision cold rolling process, and an annealing process in sequence.

[0087] Heating process: The continuously cast billet is heated in a heating furnace at a homogenization temperature of 1000~1140℃. This homogenization temperature lays the foundation for subsequent processes.

[0088] Optionally, the heat spreader temperature can be any value among 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, 1110℃, 1120℃, 1130℃, and 1140℃. However, it is not limited to this and can also be other values ​​within the range of 1000~1140℃.

[0089] Hot rolling process: After the continuously cast billet exits the heating furnace, it undergoes multiple passes of rough rolling and multiple passes of finish rolling to obtain hot-rolled plates.

[0090] The thickness of the intermediate billet obtained from rough rolling is 30~40mm.

[0091] The initial rolling temperature of the first finishing rolling pass is ≥950℃, the final rolling temperature of the last finishing rolling pass is 850±15℃, and the thickness of the hot-rolled plate obtained by finishing rolling is 1.80~2.30mm.

[0092] Optionally, the final rolling temperature of the last finishing pass can be any value among 835℃, 840℃, 845℃, 850℃, 855℃, 860℃, and 865℃. However, it is not limited to these values ​​and can also be other values ​​within the range of 835~865℃.

[0093] Coiling process: The hot-rolled plate is coiled to obtain a hot-rolled coil at a temperature of 630±15℃.

[0094] Optionally, the winding temperature can be any value among 615℃, 620℃, 625℃, 630℃, 635℃, 640℃, and 645℃. However, it is not limited to this and can also be other values ​​within the range of 615~645℃.

[0095] Thus, by combining the comprehensive control of various temperatures during finishing rolling and the coiling temperature, it is possible to ensure that the internal structure of the hot-rolled coil is a uniform hot-rolled deformed fiber structure, while also ensuring the edge quality of the hot-rolled coil, thereby improving the rollability of subsequent cold rolling.

[0096] Pickling and continuous rolling process: The hot-rolled coil is leveled and then pickled and continuously cold rolled in multiple passes using a multi-stand pickling and continuous rolling mill to obtain a hardened plate with a thickness of 0.2~0.35mm.

[0097] In this way, the hot-rolled plate is not normalized before pickling and multi-pass continuous cold rolling, and the hot-rolled deformed fiber structure is still retained at the beginning of cold rolling, thus ensuring the cold-rollability of the steel plate, reducing the difficulty of cold rolling, and allowing for smooth continuous cold rolling without the need for preheating as in existing technologies. At the same time, the use of multi-stand pickling and rolling mills for multi-pass continuous 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.

[0098] Normalizing process of rolled hard plate: The rolled hard plate is normalized in a normalizing furnace to obtain normalized rolled hard plate; the normalizing temperature is 850~950℃.

[0099] Optionally, the normalizing temperature can be any value among 850℃, 860℃, 870℃, 880℃, 890℃, and 900℃. However, it is not limited to this and can also be other values ​​within the range of 850~900℃.

[0100] Thus, through the normalization process of hardened plates, the deformed fibrous ferrite formed during hot rolling to continuous cold rolling undergoes complete recrystallization, achieving coarsening and homogenization of the microstructure. This creates conditions for controlling the grains and texture in the subsequent annealing process, thereby ensuring the final acquisition of excellent magnetic properties. Furthermore, it also creates conditions for the smooth production of subsequent 20-roll precision cold rolling.

[0101] Furthermore, the microstructure of hardened rolled steel is a deformed fibrous structure, which is thin and has a bright surface. Therefore, the normalization process of hardened rolled steel is less difficult, and pickling is not required after normalization. In addition, due to the thinness of hardened rolled steel, the difficulty of subsequent precision cold rolling is significantly reduced. Therefore, for high-grade non-oriented silicon steel with the same composition, the normalization temperature of hardened rolled steel can be higher than that of hot-rolled steel in common technologies. This increases the size of recrystallized grains after normalization, thus laying the foundation for improving magnetic properties.

[0102] Twenty-roll precision cold rolling process: A twenty-roll single-stand cold rolling mill is used to perform precision cold rolling on normalized hardened plates to obtain precision cold-rolled plates with a thickness of (0.05~0.15)±0.002mm.

[0103] As mentioned earlier, due to the thinness of the rolled plate and the fact that the microstructure of the rolled piece is normalized recrystallized, the deformation resistance is small and the surface is bright, the difficulty of precision cold rolling is significantly reduced, and it can be quickly and stably precision cold rolled to the target thickness of the finished product.

[0104] In addition, the cold rolling mill used in the finishing cold rolling mill is a 20-roll single-stand cold rolling mill. Compared with the commonly used multi-stand acid continuous rolling mill, the diameter of the work rolls is greatly reduced, and the contact area between the rolls and the workpiece is greatly reduced, thereby greatly reducing the rolling force. This 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 difference, that is, reduces plate difference and improves the uniformity of the plate.

[0105] Annealing process: The cold-rolled steel sheet is annealed in an annealing furnace at a temperature of 900~1000℃ for 40~120s, and then cooled to obtain the non-oriented silicon steel finished product.

[0106] Thus, based on the foundation laid by the preceding processes, the grains can grow smoothly and achieve complete recrystallization by controlling the temperature and duration of the annealing process, thereby optimizing the grains and structure. For example, the recrystallized grain size increases and unfavorable textures {111} decrease after annealing. Consequently, the magnetic properties of the finished product can be greatly improved without the need for normalization of the hot-rolled plate, resulting in lower iron loss and higher magnetic induction intensity compared to existing products with the same composition.

[0107] In summary, the production method of this application adopts a novel technical route of heating-hot rolling-coiling-acid continuous rolling-hardening-20-roll precision cold rolling-annealing, which prepares the continuously cast billet into ultra-thin non-oriented silicon steel. The entire process has low production cost, high production efficiency, low production difficulty, and low equipment requirements. Moreover, the width of the obtained non-oriented silicon steel product can meet most practical needs, and it has excellent properties, including but not limited to low iron loss and high magnetic induction intensity.

[0108] In detail, from the perspective of production difficulty: First, comprehensive control of various temperatures during finishing rolling and coiling can ensure the internal structure and edge quality of the hot-rolled coil, thereby improving the rollability of subsequent cold rolling and reducing the difficulty of cold rolling and the risk of strip breakage; Second, by not normalizing the hot-rolled plate before pickling and multi-pass continuous cold rolling, the hot-rolled deformed fiber structure is still retained at the beginning of cold rolling, resulting in excellent rollability and thus reducing the difficulty of continuous cold rolling; Third, the steel plate has high plasticity during continuous cold rolling, making cold rolling less difficult, and correspondingly, the requirements for the rolled piece are... The requirements for reducing the difficulty of hot rolling are as follows: First, the thickness of the hot-rolled plate can be relatively thicker, which reduces the difficulty of hot rolling. Second, the high plasticity of the steel plate during continuous cold rolling reduces the requirements for the degree of coordinated deformation of the surface and thickness center of the rolled piece, thereby reducing the restriction on the first pass reduction rate and enabling small reduction in the first pass. This reduces the requirements for equipment. For example, a common technology requires the use of a single-stand cold rolling mill for multi-pass reciprocating cold rolling, while this application can use a multi-stand acid continuous rolling mill for rapid continuous cold rolling, which reduces the production difficulty.

[0109] From the perspective of production efficiency: First, as mentioned above, because the thickness of hot-rolled plates can be relatively greater, the production efficiency of hot rolling is improved; Second, the increased thickness of hot-rolled plates further improves the pickling efficiency in the subsequent pickling continuous rolling process; Third, no preheating is required before continuous cold rolling and fine cold rolling, greatly improving production efficiency; Fourth, this application uses a multi-stand pickling continuous rolling mill for rapid continuous cold rolling, welding the ends of two or more hot-rolled plates together sequentially and achieving full-length rolling of the coil, resulting in high production efficiency.

[0110] From the perspective of magnetic properties: First, by normalizing the rolled hard plate at a higher temperature, and then combining it with subsequent annealing, the performance-enhancing effect of the chemical composition can be fully utilized, thereby achieving superior magnetic properties under the same chemical composition; Second, the temperature and duration control of the annealing process can facilitate grain growth and reduce unfavorable textures {111}, greatly improving the magnetic properties of the finished product.

[0111] From the perspective of production costs: First, due to the reduced difficulty of cold rolling, the normalizing and annealing temperatures of hardened plates can be fully utilized to improve magnetic properties. Correspondingly, the upper limits of Si and Al content can be appropriately increased, reducing or even eliminating the need for more expensive alloying elements. The control of impurity elements can be appropriately relaxed, reducing raw material costs. Second, because there is no need for normalizing hot-rolled plates, preheating before cold rolling, and preheating before fine cold rolling, energy consumption is greatly saved, reducing energy costs. Third, the high plasticity of steel plates during continuous cold rolling reduces the requirements for cold rolling equipment, thus lowering equipment costs.

[0112] In addition to the advantages mentioned above, this application also has advantages such as excellent plate shape, high thickness accuracy, energy saving and environmental protection.

[0113] Next, optionally, in the annealing process, the annealing temperature can be any value among 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, and 1000℃. However, it is not limited to this and can also be other values ​​within the range of 900~1000℃.

[0114] Alternatively, the annealing time can be any value among 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, and 120s. However, it is not limited to these values ​​and can also be other values ​​within the range of 40 to 120s.

[0115] Preferably, in some embodiments, the annealing process involves: annealing temperature controlled at T ± 10℃, annealing time (30~50) s + 400h s / mm, where h is the thickness of the cold-rolled sheet in mm; and T is in ℃, calculated using the formula 820 + 200(11Si - 14Mn + 21Al) + 400h mm. -1h is the thickness of the cold-rolled steel sheet in mm, and the element symbols in the formula represent the mass percentage of the corresponding element in the continuously cast billet.

[0116] This can further promote complete recrystallization, optimize the recrystallized grain size, and greatly improve the magnetic properties of the steel plate.

[0117] Furthermore, 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.

[0118] In some embodiments, the annealing process involves: after reaching the required annealing time, 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℃.

[0119] In this way, by controlling the cooling, 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 and ensures the dimensional accuracy and shape quality of the finished steel plate. For example, the grain size is 500h~1000h μm / mm.

[0120] Next, preferably, the normalizing process of the rolled hard sheet is carried out for 60-100 seconds. In this way, by controlling the normalizing temperature and the normalizing time, the deformed fiber ferrite undergoes complete recrystallization, achieving coarsening and homogenization of the microstructure. For example, the recrystallized grain size after normalizing is 30-50 μm, which creates conditions for obtaining excellent magnetic properties and reducing the difficulty of subsequent production.

[0121] In this application, the normalized rolled hard plate can be sampled and tested according to GB / T4335-2013 "Method for Determination of Ferrite Grain Size of Cold-Rolled Thin Plate of Low Carbon Steel" to obtain the recrystallized grain size of the normalized rolled hard plate.

[0122] Furthermore, preferably, in the normalizing process of rolled hard sheet: the tension in the normalizing furnace is 8~10 N / mm. 2 Thus, by adopting a high-tension mode, the precipitation and growth of MnS and AlN can be promoted, which is also beneficial to improving the plate shape quality.

[0123] Preferably, in the normalizing process of the rolled hardened sheet: after normalizing, temperature-controlled cooling is performed, with a cooling rate of 10~15℃ / s when the steel sheet surface temperature is ≥400℃, and a cooling rate of 15~20℃ / s when the steel sheet surface temperature is <400℃. In this way, through the phased control of the cooling rate, combined with the high-tension mode, the grain and texture in the microstructure can be optimized, and the sheet shape quality can be further improved.

[0124] In addition, during the normalizing process of rolled sheet, normalizing is carried out in a weakly reducing atmosphere. Similarly, during the annealing process, continuous annealing is carried out in a weakly reducing atmosphere.

[0125] 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.

[0126] Next, preferably, a 20-roll precision cold rolling process is performed: 2 to 4 passes of precision cold rolling are conducted to obtain a precision cold-rolled sheet of the desired thickness. It is evident that the 20-roll 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.

[0127] Understandably, the thickness of the resulting cold-rolled sheet is approximately equal to the thickness of the finished non-oriented silicon steel product.

[0128] The concepts of "equivalent" and "equal" used in this application do not refer to absolute equality in a mathematical sense. Given factors such as production errors, measurement errors, and environmental interference in actual operation, "equivalent" and "equal" mean "substantially equal," that is, allowing for a reasonable range of error known to those skilled in the art, such as fluctuations within 5%.

[0129] In some embodiments, the total reduction rate in the 20-roll precision cold rolling process can be 40-80%. In this way, by controlling the total reduction rate, dual control can be achieved over the number of nucleation sites and the energy stored in the deformation, thereby ensuring the grain size and microstructure in the subsequent annealing process (e.g., increased recrystallized grain size and reduced unfavorable textures {111} after annealing), and thus improving the magnetic properties of the final product.

[0130] Specifically, research has found that in the 20-roll precision cold rolling process, if the total reduction ratio is too high, it will lead to more nucleation sites in the subsequent annealing process, making grain growth difficult; while if the total reduction ratio is too low, the deformation storage energy will be small, affecting grain growth. Controlling the total reduction ratio between 40% and 80% can achieve dual control over the number of nucleation sites and deformation storage energy, thereby ensuring the grain and microstructure in the subsequent annealing process, and 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.

[0131] More preferably, in the twenty-roll precision cold rolling process: the reduction rate of the first precision cold rolling is ≥30%.

[0132] The working rolls of the 20-roll single-stand cold rolling mill have a diameter of 45~65mm. The roughness of the working rolls used for the first pass of finishing cold rolling is controlled at 2.50±0.50μm, and the roughness of the working rolls used for the last pass of finishing cold rolling is controlled at 0.50±0.10μm.

[0133] Next, preferably, in the hot rolling process: the total reduction rate of finishing rolling is 93~95%, and the reduction rate of the final finishing rolling is 20~25%. Thus, controlling the total reduction rate of finishing rolling and the reduction rate of the final finishing rolling can improve the shape of the hot-rolled plate. For example, after subsequent leveling, the unevenness of the hot-rolled coil can reach ≤10mm within a length of 1000mm, thereby improving the stability and production rate of subsequent cold rolling.

[0134] The unevenness here can be determined by sampling and testing the steel plate according to GB / T 709-2019 "Dimensions, Shape, Weight and Permissible Deviations of Hot-Rolled Steel Plates and Strips" to obtain the range of unevenness.

[0135] In some embodiments, the hot rolling process may involve five to nine passes in roughing, such as six passes; and five to nine passes in finishing, such as seven passes. However, it is not limited to these.

[0136] High-pressure water descaling can be performed after the continuously cast billet exits the heating furnace and before rough rolling. Whether or not descaling is performed and the specific operation can be determined based on the surface oxide scale of the continuously cast billet, and this application does not impose any restrictions.

[0137] In addition, after the hot-rolled plate exits the finishing mill stand, it can be cooled by controlled temperature through air cooling or water cooling, such as laminar flow cooling, before being coiled. Specific cooling technologies can be implemented in any feasible manner in the art, and this application does not limit them.

[0138] Next, preferably, in the acid-rolling process: the reduction rate of the first cold rolling pass is 20-30%, and the reduction amount is ≤0.60mm; the bending force of the work rolls of each stand in the acid-rolling process is controlled at 50-150kN, so that the edge of the resulting hardened plate produces a controllable edge waviness with a height of 1.0-2.5mm. Typically, existing ultra-thin high-grade non-oriented silicon steel requires a large reduction in the first cold rolling pass, 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 requirements for cold rolling equipment and the thickness requirements for hot-rolled plates, greatly reducing production difficulty and improving production efficiency.

[0139] Preferably, in the acid continuous rolling process, a micro-edge wavy rolling mode can be adopted to avoid the edge of the rolled piece being in a tensile state, thereby avoiding tension concentration at the edge and causing strip breakage. This can further ensure the smooth progress of multi-pass continuous cold rolling in a multi-stand acid continuous rolling mill.

[0140] 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 50 kN to 150 kN, so that the edge of the resulting hardened plate produces a controllable edge wavy with a height of 1.0 to 2.5 mm.

[0141] 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.

[0142] In some embodiments, the working roll diameter of the multi-stand pickling and rolling mill is 300-500 mm.

[0143] Furthermore, in the pickling and rolling process: after the hot-rolled coil is leveled, it is preferable to first straighten it to improve the shape of the rolled piece, thereby improving the stability and production rate of cold rolling. Understandably, in common technologies, due to poor plasticity, the rolled piece cannot be straightened before cold rolling. However, in the technology of this application, since the hot-rolled plate is cold-rolled without normalization, its plasticity is excellent. 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, allowing for smooth and rapid production.

[0144] Furthermore, in some embodiments, the specific pickling process in the continuous acid rolling process can be implemented using any feasible technique in the art, and this application does not limit it. For example, HCl can be used for pickling, wherein the acid concentration is 120~160g / L and the acid solution contains Fe 2+ Concentration ≤130g / L; acid temperature 75~85℃; add silicon steel pickling accelerator to the acid solution, the silicon steel pickling accelerator accounts for 0.05~0.10% of the weight of the acid solution.

[0145] In addition, in the acid rolling process, the number of cold rolling passes can be four to seven. For example, five passes.

[0146] Preferably, in the pickling and rolling process: after pickling, the product is first rinsed with desalinated water and dried, and then after edge trimming, it is directly subjected to continuous cold rolling without preheating.

[0147] Similarly, in twenty-roll precision cold rolling: the edges of the normalized rolled hard plate are first trimmed, and then precision cold rolling is carried out directly without preheating.

[0148] Thus, trimming the edges can further improve the smooth production of continuous cold rolling and precision cold rolling. Of course, this application is not limited to this, and trimming may not be necessary.

[0149] Next, in the heating process, the steel plate is kept at a uniform heating temperature for 40-60 minutes.

[0150] In some embodiments, the heating process involves controlling the temperature of the continuously cast billet entering the heating furnace to be ≥450°C.

[0151] Furthermore, during the heating process, the thickness of the continuously cast billet is 200~250mm.

[0152] Continuously cast billets can be prepared through steelmaking and continuous casting processes. The steelmaking process may specifically include techniques such as hot metal desulfurization, converter smelting, and vacuum refining. This application does not limit the scope of the process, and those skilled in the art can perform steelmaking and continuous casting in any feasible manner.

[0153] For example, blast furnace molten iron at a temperature ≥1500℃ can be desulfurized using KR (Kill-Rake) until the sulfur content in the molten iron is ≤0.0010%. Then, the molten iron and special scrap steel for silicon steel (such as silicon steel scrap for motor cores or motor core waste) are added to a converter for converter smelting, where the weight of the scrap steel accounts for 30~40% of the total weight of the molten steel. The final C content at the converter end is 0.020~0.050%, S≤0.0015%, and P≤0.015%. Finally, after vacuum refining, during which alloying is carried out, molten steel with the target chemical composition that meets the requirements of non-oriented silicon steel products is obtained. The steel is then tapped and continuously cast to obtain continuously cast billets.

[0154] It is understandable that the chemical composition of the molten steel at the end of steelmaking, the chemical composition of the continuously cast billet, and the chemical composition of the finished non-oriented silicon steel are consistent. During the process of preparing the finished non-oriented silicon steel from the continuously cast billet, the chemical composition remains unchanged. The chemical composition of non-oriented silicon steel can be characterized by sampling and testing the continuously cast billet.

[0155] Incidentally, in this application, the molten steel, continuously cast billets, or final non-oriented silicon steel products at the end of the steelmaking process can be sampled in accordance with GB / T 20066-2006 "Sampling and Sample Preparation Methods for Determination of Chemical Composition of Steel and Iron", and the chemical composition of the molten steel, continuously cast billets, or final non-oriented silicon steel products can be tested in accordance with GB / T 223 series "Methods for Chemical Analysis of Iron and Steel and Alloys".

[0156] In some embodiments, when the non-oriented silicon steel of the first embodiment described above is prepared using the production method of this embodiment, the chemical composition of the continuously cast billet, by mass percentage, includes: C≤0.005%, Si:3.2~3.7%, Mn:0.3~0.8%, Al:0.70~1.2%, S≤0.01%, P≤0.08%, N≤0.01%, O≤0.01%, Cr, Ni and Cu ≤5.0% respectively, Mo, Nb, V and Ti ≤0.1% respectively, and the remainder is Fe and unavoidable inclusions.

[0157] Of course, preferably, the chemical composition of the continuously cast billet, by mass percentage, may also satisfy any one or more of the following: C≤0.0025%, S≤0.0015%, P≤0.03%, N≤0.003%, O≤0.003%, Nb≤0.004%, V≤0.004%, Ti≤0.005%, Mo≤0.004%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, Nb+V+Ti+Mo≤0.009%, and / or, Cr+Ni+Cu≤0.06%.

[0158] More preferably, in this application, the equiaxed crystal ratio of the continuously cast billet is ≥65%, and the narrow cross-section concave depth is ≤3.0mm. 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, cold rolling, and precision cold rolling), and further ensuring smooth plate passing throughout the entire process.

[0159] 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.

[0160] In this application, GB / T 24178-2009 "Method for Low Magnification Evaluation of Solidification Structure of Continuously Cast Steel Billets" can be used to sample continuously cast billets and test the equiaxed crystal ratio and narrow section concave depth of the continuously cast billets.

[0161] In addition, after the annealing process of this application, coating, finishing and other processes can be performed. These are all feasible techniques of this application and are not the inventive point of this application, so they will not be introduced further.

[0162] In summary, the beneficial effects of this application include:

[0163] On the one hand, compared with the three existing preparation methods of ultra-thin non-oriented silicon steel, this application adopts a brand-new process of heating-hot rolling-coiling-acid continuous rolling-hardening-20-roll precision cold rolling-annealing to prepare ultra-thin non-oriented silicon steel from continuous casting billets. The entire process has low production cost, high production efficiency, low production difficulty, and low equipment requirements. Moreover, the width of the obtained non-oriented silicon steel product can meet most practical needs and has excellent performance, including but not limited to low iron loss and high magnetic induction intensity.

[0164] On the other hand, compared with the traditional continuous casting-hot rolling-normalizing-multiple cold rolling + multiple annealing methods, this application eliminates the need for normalizing the hot-rolled plate. This allows the hot-rolled deformed fiber structure to be retained during cold rolling, reducing the difficulty of cold rolling and enabling rapid, efficient, and smooth production in the acid-rolling process. Furthermore, by controlling the normalizing of the hardened plate, the grain size and microstructure of the normalized hardened plate are optimized, further improving rollability and ensuring rapid and smooth 20-roll precision cold rolling. This ensures smooth plate passage throughout the process, avoiding edge cracks and strip breaks. Moreover, the reduced difficulty of cold rolling leads to a corresponding reduction in the thickness requirements of the hot-rolled plate, further lowering the production difficulty of hot rolling. In summary, this reduces the overall production difficulty and cost while improving overall production efficiency.

[0165] On the other hand, in conjunction with the foregoing, although this application does not normalize the hot-rolled plate, it does not reduce the magnetic properties. On the contrary, it can improve the magnetic properties compared with the prior art. For example, through the hot rolling process and the acid continuous rolling process, a deformed fibrous ferrite structure is formed. Then, through the normalization process of the hardened plate, the deformed fibrous ferrite undergoes complete recrystallization, achieving coarsening and homogenization of the structure. At the same time, since the thickness of the hardened plate is thin, the difficulty of subsequent precision cold rolling is significantly reduced. Therefore, for high-grade non-oriented silicon steel with the same composition, the normalization temperature of the hardened plate is higher, which is conducive to the growth of recrystallized grains. Combined with the control of subsequent annealing temperature and annealing time, the size of recrystallized grains is increased and the unfavorable texture {111} is reduced, and magnetic properties far superior to those of the prior art can be obtained under the same chemical composition. In addition, due to the reduction in production difficulty, it is not necessary to strictly control the upper limit of Si and Al content as in the prior art. That is, the Si and Al content can be increased, and the promoting effect of chemical composition on performance can be fully utilized, thus making the improvement of magnetic properties possible.

[0166] 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.

[0167] 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 is prepared through a process route of heating-hot rolling-coiling-acid continuous rolling-hardening-twenty-roll precision cold rolling-annealing.

[0168] Table 1 shows the main elements and some impurity elements of each continuous casting billet. It is understood that other impurity elements not shown also meet the content ranges described in this application.

[0169] [Table 1]

[0170]

[0171] 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 Steel Billets".

[0172] [Table 2]

[0173]

[0174] 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 heating-hot rolling-coiling-acid continuous rolling-hardening-20-roll precision cold rolling-annealing. In the production process, normalizing and preheating are not required before acid continuous rolling, nor is preheating required before 20-roll precision cold rolling.

[0175] The key parameters for the heating process, hot rolling process, pickling and rolling process, normalizing process for hardened plates, and 20-roll cold finishing process in the production process are shown in Tables 3 to 5. 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. These can be understood in conjunction with the preceding descriptions.

[0176] [Table 3]

[0177]

[0178] [Table 4]

[0179]

[0180] [Table 5]

[0181]

[0182] In the production process, after the 20-roll precision cold rolling process is completed, the hard-rolled coils obtained in Examples 1-1, 1-2, 1-3, and 1-4 are divided into two coils: the hard-rolled coil of Example 1-1 is divided into two coils, denoted as Example 1-1-1 and 1-1-2; the hard-rolled coil of Example 1-2 is divided into two coils, denoted as Example 1-2-1 and 1-2-2; the hard-rolled coil of Example 1-3 is divided into two coils, denoted as Example 1-3-1 and 1-3-2; the hard-rolled coil of Example 1-4 is divided into two coils, denoted as Example 1-4-1 and 1-4-2; the effect of the annealing process on the properties of the obtained non-oriented silicon steel is illustrated.

[0183] Table 6 shows some key parameters of the annealing process in all embodiments. 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 of this application; conversely, parameters not shown in the table do not necessarily mean they are not key parameters. These can be understood in conjunction with the preceding description.

[0184] [Table 6]

[0185]

[0186] 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.

[0187] [Table 7]

[0188]

[0189] 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 "Determination of ferrite grain size in cold-rolled low-carbon steel sheets"; and the flatness of non-oriented silicon steel finished products was measured using GB / T 708-2019 "Dimensions, shape, weight and permissible deviations of cold-rolled steel sheets and strips".

[0190] As can be seen, this application adopts a novel process of heating-hot rolling-coiling-acid continuous rolling-hardening-20-roll precision cold rolling-annealing to prepare ultra-thin non-oriented silicon steel with a thickness h of (0.05~0.15)±0.002mm from the continuous casting billet. The resulting non-oriented silicon steel has a grain size controlled at 500h~1000h μm / mm and also has excellent magnetic properties and processing performance.

[0191] The iron loss P of the non-oriented silicon steel obtained in all embodiments 1.0 / 400 ≤9.5W / kg, iron loss P 0.5 / 1000 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0192] In Examples 1-1-1, 1-1-2, 2-1, and 3-1, the thickness of the non-oriented silicon steel obtained was 0.05 ± 0.002 mm, and the iron loss P was... 1.0 / 400 ≤8.0W / kg, iron loss P 0.5 / 1000 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0193] Examples 1-2-1, 1-2-2, 2-2, and 3-2, wherein the thickness of the non-oriented silicon steel is 0.08±0.002mm, and the iron loss P 1.0 / 400 ≤8.5W / kg, iron loss P 0.5 / 1000 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0194] Examples 1-3-1, 1-3-2, 2-3, 3-3, 4-1, 4-2, 4-3, and 4-4 yielded non-oriented silicon steel with a thickness of 0.10 ± 0.002 mm and an iron loss P. 1.0 / 400 ≤9.0W / kg, iron loss P 0.5 / 1000 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0195] Examples 1-4-1, 1-4-2, 2-4, and 3-4 yielded non-oriented silicon steel with a thickness of 0.15 ± 0.002 mm and an 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.

[0196] In particular, in Example 1-1-2, all processes before the annealing step are the same as in Example 1-1-1, but the annealing temperature is higher and the annealing time is longer. The resulting non-oriented silicon steel has larger grains and lower iron loss, but the elongation is significantly reduced.

[0197] In particular, in Example 1-2-2, all processes before the annealing step are the same as in Example 1-2-1, but the annealing temperature is higher and the annealing time is longer. The resulting non-oriented silicon steel has larger grains and lower iron loss, but the elongation is significantly reduced.

[0198] Specifically, in Example 1-3-2, compared to Example 1-3-1, all processes before the annealing step are the same, but the annealing temperature is lower and the annealing time is shorter. This results in smaller grains and higher iron loss in the obtained non-oriented silicon steel. 1.0 / 400 Reaching 8.8 W / kg, P 0.5 / 1000 It reached 13.6 W / kg.

[0199] Specifically, in Example 1-4-2, compared to Example 1-4-1, all processes before the annealing step are the same, but the annealing temperature is lower and the annealing time is shorter. This results in smaller grains and higher iron loss in the obtained non-oriented silicon steel. 1.0 / 400 Reaching 9.3 W / kg, P 0.5 / 1000 It reaches 14.5 W / kg.

[0200] Specifically, Example 4-1, compared to Example 1-3-1, added 0.038% Sn to the chemical composition, while maintaining essentially the same process parameters throughout the entire process. The resulting non-oriented silicon steel exhibited higher magnetic induction intensity. 5000 It reaches 1.655T, and the rest of the performance is basically the same.

[0201] Specifically, Example 4-2, compared to Example 1-3-1, added 0.056% Sb to the chemical composition, while maintaining essentially the same process parameters throughout the entire process. The resulting non-oriented silicon steel exhibited higher magnetic induction intensity and B. 5000 It reaches 1.653T, and the rest of the performance is basically the same.

[0202] Specifically, Example 4-3 added 1.05% Cr to the chemical composition compared to Example 1-3-1, while the rest of the process parameters were basically the same. The resulting non-oriented silicon steel had higher strength, with a yield strength of 536 MPa and a tensile strength of 621 MPa, while the other properties were basically the same.

[0203] Specifically, Example 4-4 added 0.58% Cu to the chemical composition compared to Example 1-3-1, while the rest of the process parameters were basically the same. The resulting non-oriented silicon steel had higher strength, with a yield strength of 522 MPa and a tensile strength of 608 MPa. The other properties were basically the same.

Claims

1. A method for producing ultra-thin high-grade non-oriented silicon steel, characterized in that, The production method includes, Heating process: The continuously cast billet is heated in a heating furnace at a soaking temperature of 1000~1140℃; Hot rolling process: The continuously cast billet is subjected to multiple passes of rough rolling and multiple passes of finish rolling; wherein, the thickness of the intermediate billet obtained by rough rolling is 30~40mm, the starting rolling temperature of the first pass of finish rolling is ≥950℃, the final rolling temperature of the last pass of finish rolling is 850±15℃, and the thickness of the hot rolled plate obtained by finish rolling is 1.80~2.30mm. Coiling process: The hot-rolled sheet is coiled to obtain a hot-rolled coil at a temperature of 630±15℃. Pickling and continuous rolling process: The hot-rolled coil is leveled and then pickled and continuously cold-rolled in multiple passes using a multi-stand pickling and continuous rolling mill to obtain a hardened plate with a thickness of 0.2~0.35mm; there is no normalization before the pickling and continuous rolling process; Normalizing process of rolled hardened sheet: The rolled hardened sheet is normalized in a normalizing furnace to obtain normalized rolled hardened sheet; the normalizing temperature is 850~950℃, the normalizing time is 60~100s, and the tension in the normalizing furnace is 8~10N / mm. 2 After reaching the normalization time, temperature-controlled cooling is carried out. 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. Twenty-roll precision cold rolling process: A twenty-roll single-stand cold rolling mill is used to perform precision cold rolling on normalized hardened plates to obtain precision cold-rolled plates with a thickness h of (0.05~0.15)±0.002mm; Annealing process: The precision cold-rolled sheet is annealed in an annealing furnace at a temperature of T ± 10℃, where T is in ℃ and is determined by the formula 820 + 200(11Si - 14Mn + 21Al) + 400h mm. -1 The element symbols in the formula represent the mass percentage of the corresponding element in the continuously cast billet. The annealing time is 40~120s, followed by cooling to obtain the non-oriented silicon steel finished product.

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

3. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Annealing process: Annealing time (30~50)s+400h s / mm; h is the thickness of the cold-rolled plate in mm.

4. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Twenty-roll precision cold rolling process: 2 to 4 passes of precision cold rolling are performed, with a total reduction rate of 40 to 80%, and the reduction rate of the first pass of precision cold rolling is ≥30%.

5. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Sour rolling process: The reduction rate of the first cold rolling pass is 20~30%, and the reduction amount is ≤0.60mm; the bending force of the work rolls of each stand in the acid rolling process is controlled at 50~150kN, so that the edge of the resulting hardened plate produces a controllable edge wave with a height of 1.0~2.5mm.

6. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Hot rolling process: The total reduction rate of finishing rolling is 93~95%, and the reduction rate of the last finishing rolling is 20~25%.

7. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Pickling and continuous rolling process: After pickling, multiple passes of continuous cold rolling are carried out directly without preheating; Twenty-roll precision cold rolling process: No preheating is required before precision cold rolling.

8. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Annealing process: After the annealing time is reached, temperature-controlled cooling is carried out. When the steel plate surface temperature is >700℃, the cooling rate is 5~10℃ / s, when the steel plate surface temperature is 400~700℃, the cooling rate is 10~15℃ / s, and when the steel plate surface temperature is <400℃, the cooling rate is 15~20℃ / s.

9. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Twenty-roll finishing cold rolling process: The working roll diameter of the twenty-roll single-stand cold rolling mill is 45~65mm. The roughness of the working roll used for the first finishing cold rolling is 2.50±0.50μm, and the roughness of the working roll used for the last finishing cold rolling is 0.50±0.10μm.

10. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Sour rolling process: The multi-stand sour rolling mill used is any one of the following: a six-roll five-stand sour rolling mill, a six-roll six-stand sour rolling mill, or an eighteen-roll six-stand sour rolling mill.

11. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, Heating process: The continuously cast billet is held at a homogenization temperature for 40-60 minutes.

12. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 1, characterized in that, The thickness of the continuously cast billet is 200~250mm; The chemical composition of the continuously cast billet, by mass percentage, includes: C≤0.005%, Si:3.2~3.7%, Mn:0.3~0.8%, Al:0.70~1.2%, S≤0.01%, P≤0.08%, N≤0.01%, O≤0.01%, Cr, Ni and Cu ≤5.0% respectively, Mo, Nb, V and Ti ≤0.1% respectively, and the remainder being Fe and unavoidable inclusions.

13. The method for producing ultra-thin high-grade non-oriented silicon steel according to claim 12, characterized in that, The chemical composition of the continuously cast billet, by mass percentage, satisfies one or more of the following: C≤0.0025%, S≤0.0015%, P≤0.03%, N≤0.003%, O≤0.003%, Nb≤0.004%, V≤0.004%, Ti≤0.005%, Mo≤0.004%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, Nb+V+Ti+Mo≤0.009%, Cr+Ni+Cu≤0.06%.

14. An ultra-thin high-grade non-oriented silicon steel, characterized in that, The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C ≤ 0.005%, Si: 3.2~3.7%, Mn: 0.3~0.8%, Al: 0.70~1.2%, S ≤ 0.01%, P ≤ 0.08%, N ≤ 0.01%, O ≤ 0.01%, Cr, Ni and Cu ≤ 5.0% respectively, Mo, Nb, V and Ti ≤ 0.1% respectively, with the remainder being Fe and unavoidable inclusions; it is prepared by the production method of ultra-thin high-grade non-oriented silicon steel according to any one of claims 1 to 13; The recrystallized grain size of the non-oriented silicon steel is 500h~1000h μm / mm; The iron loss P of the non-oriented silicon steel 1.0 / 400 ≤9.5W / kg, iron loss P 0.5 / 1000 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

15. The ultra-thin high-grade non-oriented silicon steel according to claim 14, characterized in that, The thickness of the non-oriented silicon steel is 0.05±0.002mm, and the iron loss P 1.0 / 400 ≤8.0W / kg, iron loss P 0.5 / 1000 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T; Alternatively, the thickness of the non-oriented silicon steel is 0.08±0.002mm, and the iron loss P 1.0 / 400 ≤8.5W / kg, iron loss P 0.5 / 1000 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.63T; Alternatively, the thickness of the non-oriented silicon steel is 0.10±0.002mm, and the iron loss P 1.0 / 400 ≤9.0W / kg, iron loss P 0.5 / 1000 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.63T; Alternatively, the thickness of the non-oriented silicon steel is 0.15±0.002mm, 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.

16. The ultra-thin high-grade non-oriented silicon steel according to claim 14, characterized in that, The chemical composition of the non-oriented silicon steel, by mass percentage, further includes any one or both of Sn: 0.01~0.15% and Sb: 0.01~0.15%.

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