Non-oriented silicon steel sheet and method for processing the same

Abstract

This application provides a non-oriented silicon steel sheet and its processing method. The processing method involves heating a continuously cast billet to 1080–1180℃ and holding it at that temperature for 200–300 minutes, followed by rough rolling and seven passes of finish rolling to obtain a hot-rolled sheet. Asynchronous rolling is introduced in the sixth and seventh passes of the finish rolling. Normalization is used to obtain fine grains on the surface of the hot-rolled sheet. The normalization temperature is T1 = 15 × [6.7 – ([Si] + 0.72 × [Al]) × 100]. 2 +760×[1-|v7 up / v7 down The temperature is set at -1℃, with a heating rate of 50-80℃ / s and a holding time of 20-50s. Non-oriented silicon steel sheets are obtained through cold rolling and annealing. The annealing temperature is T2 = T1 + 120℃, and the holding time is 200-400s. By controlling the hot rolling and normalizing processes, normalized sheets with fine surface grains and large intermediate grains are obtained, which hinders the propagation of cracks during the cold rolling process, completes the rolling smoothly, and obtains non-oriented silicon steel with good magnetic properties through long-term holding annealing.

Description

Technical Field

[0001] This application relates to the field of steel processing technology, and in particular to a non-oriented silicon steel sheet and its processing method. Background Technology

[0002] Non-oriented silicon steel is an important soft magnetic metallic material, widely used in the preparation of core materials for electric motors, compressors, and power transformers. With the rapid development of high efficiency, miniaturization, and lightweight electromechanical products, the requirements for motor performance are becoming increasingly stringent. A crucial measure to improve motor performance is selecting core materials with superior magnetic properties. Therefore, non-oriented silicon steel is required to possess low iron loss and high magnetic flux density. To reduce iron loss in non-oriented silicon steel, a higher content of silicon and a certain amount of aluminum are typically added to increase its resistivity, especially in high-grade non-oriented silicon steel. However, as the content of silicon and aluminum alloying elements increases, lattice distortion increases, leading to increased brittleness and decreased toughness in non-oriented silicon steel. Cold rolling becomes prone to strip breakage, making it difficult to produce continuous sheets.

[0003] To address this issue, existing technologies involve preheating the steel plate before rolling to increase its temperature, thus achieving a more ductile rolling process. However, this increases production costs. Lowering the normalizing temperature yields fine recrystallized grains or a mixed structure with some non-recrystallized grains, preventing excessively large grains that could lead to brittle fracture during cold rolling. However, this can hinder grain growth in the finished product, resulting in poorer magnetic properties. Summary of the Invention

[0004] The purpose of this application is to provide a non-oriented silicon steel sheet and its processing method. The processing method of the non-oriented silicon steel sheet introduces asynchronous rolling into hot rolling finishing and combines it with normalization process control to obtain fine grains on the surface of the normalized steel sheet, which hinders the crack propagation during cold rolling, solves the problem of cold rolling strip breakage in non-oriented silicon steel with high silicon-aluminum alloy content in the prior art, and obtains better magnetic properties.

[0005] To achieve the aforementioned objectives, one embodiment of this application provides a method for processing non-oriented silicon steel sheets, comprising sequentially performing heating, hot rolling, normalizing, cold rolling, annealing, and coating processes on a continuously cast billet, wherein:

[0006] During the heating process, the continuous casting billet is heated to 1080–1180℃ and held for 200–300 minutes.

[0007] In the hot rolling process, the heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain the hot rolled plate. The 6th and 7th passes of finish rolling are asynchronous rolling.

[0008] In the normalizing process, the hot-rolled plate is fed into a normalizing furnace for normalizing treatment. The normalizing temperature is T1 = 15 × [6.7 - ([Si] + 0.72 × [Al]) × 100].2 +760×[1-|v7 up / v7 down -1|]℃, heating rate is 50~80℃ / s, holding time is 20~50s, where [Si] and [Al] are the mass percentages of Si and Al in the continuously cast billet, v7 up v7 is the circumferential speed of the upper work roll in the 7th pass of the finishing mill. down The circumferential speed of the lower work roll in the 7th pass of finishing mill;

[0009] In the cold rolling process, the normalized hot-rolled plate is cold-rolled to obtain a cold-rolled plate;

[0010] In the annealing process, the cold-rolled sheet is continuously annealed at a temperature of T2 = T1 + 120℃ and a holding time of 200 to 400 seconds.

[0011] As a further improvement of one embodiment of this application, in the hot rolling process, the circumferential speed ratio of the upper and lower work rolls in the 6th pass is 1:1.01 to 1:1.04, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass is the opposite of that in the 6th pass.

[0012] As a further improvement of one embodiment of this application, in the hot rolling process, the final rolling temperature is 720-800°C, the coiling temperature is 600-660°C, the coiling holding time is 60-90 minutes, and after holding, the coil is uncoiled and air-cooled to room temperature.

[0013] As a further improvement of one embodiment of this application, the recrystallized grain size of the hot-rolled plate surface layer is 2 to 18 μm, wherein the surface layer includes an upper surface layer and a lower surface layer of the same thickness, and the sum of the thicknesses of the upper surface layer and the lower surface layer accounts for 20-35% of the thickness of the hot-rolled plate.

[0014] As a further improvement of one embodiment of this application, the average recrystallized grain size of the surface layer of the normalized hot-rolled plate is 20-45 μm, and the average recrystallized grain size of the intermediate layer is 80-110 μm.

[0015] As a further improvement of one embodiment of this application, the average recrystallized grain size of the annealed cold-rolled sheet is 120-150 μm.

[0016] As a further improvement of one embodiment of this application, the thickness of the hot-rolled plate obtained after hot rolling is 2.10 to 2.30 mm, and the thickness of the cold-rolled plate obtained after cold rolling is 0.25 to 0.35 mm.

[0017] As a further improvement of one embodiment of this application, in the normalizing process, the atmosphere inside the normalizing furnace is pure N2, and the temperature fluctuation range of the normalizing temperature is within 5°C above and below the T1 temperature.

[0018] During the annealing process, the protective atmosphere is a mixture of H2 and N2, wherein the volume percentage of H2 is 30-70%.

[0019] An embodiment of this application also provides a non-oriented silicon steel sheet, which is prepared by the aforementioned processing method. The chemical composition of the non-oriented silicon steel sheet, by mass percentage, includes: C≤0.0025%, S≤0.0015%, N≤0.002%, Si: 3.25~3.65%, Al: 0.85~1.25%, Mn: 0.27~0.47%, Sn: 0.05~0.08%, P≤0.02%, Nb+V≤0.006%, Ti≤0.002%, Cu≤0.03%, Mo≤0.006%, Ni+Cr≤0.06%, with the remainder being Fe and unavoidable impurities.

[0020] As a further improvement to one embodiment of this application, when the thickness of the non-oriented silicon steel plate is 0.25 mm, the iron loss P 1.0 / 400 ≤12W / kg, magnetic induction intensity B 5000 ≥1.64T; when the thickness of the non-oriented silicon steel sheet is 0.30mm, the iron loss P 1.0 / 400 ≤14W / kg, magnetic induction intensity B 5000 ≥1.65T; when the thickness of the non-oriented silicon steel sheet is 0.35mm, the iron loss P 1.0 / 400 ≤17W / kg, magnetic induction intensity B 5000 ≥1.68T.

[0021] As a further improvement of one embodiment of this application, when the thickness of the non-oriented silicon steel sheet is 0.25 mm, the thickness of the hot-rolled sheet is 2.10 mm; when the thickness of the non-oriented silicon steel is 0.30 mm, the thickness of the hot-rolled sheet is 2.20 mm; and when the thickness of the non-oriented silicon steel is 0.35 mm, the thickness of the hot-rolled sheet is 2.30 mm.

[0022] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0023] The processing method for non-oriented silicon steel sheets provided in this application introduces asynchronous rolling in the 6th to 7th passes of hot rolling finishing. By increasing the shear deformation of the surface layer of the hot-rolled sheet through the circumferential speed difference between the upper and lower work rolls, and combining the process control of the hot rolling and normalizing processes, fine recrystallized grains are obtained on the surface of the hot-rolled sheet. Ultimately, the size and distribution of the recrystallized grains in the normalized sheet are precisely controlled. The fine grains on the surface of the normalized sheet can hinder the crack propagation during the cold rolling process, giving the normalized sheet better machinability, reducing the risk of edge cracks and strip breakage during cold rolling, and improving rolling efficiency.

[0024] Based on the improved machinability of normalized steel plates, the silicon and aluminum content of non-oriented silicon steel can be increased, further improving the resistivity, thereby obtaining non-oriented silicon steel with lower iron loss.

[0025] The introduction of asynchronous rolling mills can produce more shear deformation structures, providing nucleation sites for Goss and Cube grains, and providing more space for grain growth, thereby enhancing the Goss and Cube texture and improving the magnetic properties of the finished product. Detailed Implementation

[0026] The present invention will be described in detail below with reference to specific embodiments, but these embodiments do not limit the present invention. Any changes in reaction conditions, reactants or raw material amounts made by those skilled in the art based on these embodiments are included within the protection scope of the present invention.

[0027] This application provides a method for processing non-oriented silicon steel sheets, including sequentially performing heating, hot rolling, normalizing, cold rolling, annealing, and coating processes on continuously cast billets, wherein:

[0028] During the heating process, the continuous casting billet is heated to 1080–1180℃ and held for 200–300 minutes.

[0029] In the hot rolling process, the heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain the hot rolled plate. The 6th and 7th passes of finish rolling are asynchronous rolling.

[0030] In the normalizing process, the hot-rolled plate is fed into a normalizing furnace for normalizing treatment. The normalizing temperature is T1 = 15 × [6.7 - ([Si] + 0.72 × [Al]) × 100]. 2 +760×[1-|v7 up / v7 down -1|]℃, heating rate is 50~80℃ / s, holding time is 20~50s, where [Si] and [Al] are the mass percentages of Si and Al in the continuously cast billet, v7 up v7 is the circumferential speed of the upper work roll in the 7th pass of the finishing mill. down The circumferential speed of the lower work roll in the 7th pass of finishing mill;

[0031] In the cold rolling process, the normalized hot-rolled plate is cold-rolled to obtain a cold-rolled plate;

[0032] In the annealing process, the cold-rolled sheet is continuously annealed at a temperature of T2 = T1 + 120℃ and a holding time of 200 to 400 seconds.

[0033] The processing method for non-oriented silicon steel sheets provided in this application avoids the deterioration of the magnetic properties of the steel sheet by solid solution treatment of inclusions such as MnS, AlN, and carbon and nitrogen compounds during continuous casting billet heating, and also does not affect the rolling force and sheet shape control during hot rolling. Asynchronous rolling is used in the penultimate 6th and 7th passes of the finishing rolling process, increasing the shear deformation of the hot-rolled sheet surface. This allows the surface layer to nucleate and grow under the drive of thermal and deformation energy, ultimately forming a layer of fine grains. Combined with a relatively fast heating rate in the normalizing process, the recovery process is kept from being too long, ensuring a sufficient number of grain nucleation points. Short holding time is used to prevent the growth of small surface grains and their engulfment by intermediate grains, obtaining the desired normalized structure, reducing crack propagation during cold rolling, and preventing cold rolling strip breakage. The annealing process causes recrystallization of the fibrous structure of the cold-rolled sheet, promoting grain nucleation and growth, and improving the steel sheet texture. By maintaining the temperature for a longer period of time, the grains can grow and become more uniform, and low-temperature continuous annealing can be achieved, resulting in higher magnetic induction while ensuring excellent iron loss.

[0034] In some embodiments, during the hot rolling process, the circumferential speed ratio of the upper and lower work rolls in the 6th pass is 1:1.01 to 1:1.04, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass is the opposite of that in the 6th pass. Controlling the circumferential speed ratio of the upper and lower work rolls to a smaller ratio avoids severe deformation of the hot-rolled sheet. Simultaneously, controlling the circumferential speed ratio of the upper and lower work rolls in the 7th pass to be opposite to that in the 6th pass counteracts the warping caused by asynchronous rolling, resulting in better control of the sheet shape.

[0035] In some embodiments, during the hot rolling process, the final rolling temperature is 720–800°C, the coiling temperature is 600–660°C, the coiling holding time is 60–90 minutes, and after holding, the coil is uncoiled and air-cooled to room temperature. By controlling the final rolling temperature, coiling temperature, and coiling time of hot rolling, the growth of fine grains on the surface of the hot-rolled plate is avoided.

[0036] In some embodiments, the recrystallized grain size of the hot-rolled plate surface layer is 2–18 μm. The surface layer comprises an upper surface layer and a lower surface layer of equal thickness, the sum of which accounts for 20–35% of the hot-rolled plate thickness. The upper surface layer extends from the upper surface of the hot-rolled plate to a certain depth in the thickness direction; the lower surface layer extends from the lower surface of the hot-rolled plate to a certain depth in the thickness direction. Both the upper and lower surface layers have the same thickness and contain fine grains with a grain size of 2–18 μm. The method for obtaining the grain size refers to GB / T 6394-2017, "Method for Determination of Average Grain Size of Metals".

[0037] In some embodiments, the average recrystallized grain size of the surface layer of the normalized hot-rolled plate is 20–45 μm, and the average recrystallized grain size of the intermediate layer is 80–110 μm. After normalization, the grain size increases from 2–18 μm to 20–45 μm during recrystallization, while the grain size of the intermediate layer is larger than that of the surface layer.

[0038] Furthermore, the average recrystallized grain size of the annealed cold-rolled sheet is 120-150 μm. Due to the long holding time during annealing, combined with the annealing temperature T2, the cold-rolled sheet has sufficient time for grain growth and homogenization, eliminating the difference in grain size between the surface and intermediate layers of the steel sheet caused by asynchronous rolling in finishing rolling. This results in higher magnetic induction while ensuring excellent iron loss.

[0039] In some embodiments, the thickness of the hot-rolled sheet obtained after hot rolling is 2.10–2.30 mm, and the thickness of the cold-rolled sheet obtained after cold rolling is 0.25–0.35 mm. Furthermore, the thickness of the continuously cast billet is 210–240 mm; in the cold rolling process, the first pass reduction rate is 38–42%. The target thickness of the hot-rolled sheet is set according to the final thickness of the silicon steel sheet, reducing the rolling load pressure in the cold rolling process and facilitating the control of the cold-rolled sheet shape. Simultaneously, using an ultra-high reduction rate in the first pass of the cold rolling process results in large deformation in the thickness direction, improving the flexibility of the steel sheet and reducing the probability of edge cracks and strip breakage in subsequent cold rolling passes.

[0040] In some embodiments, during the normalizing process, the atmosphere inside the normalizing furnace is pure N2, and the normalizing temperature fluctuates within a range of 5°C above and below temperature T1; during the annealing process, the protective atmosphere is a mixture of H2 and N2, wherein the volume percentage of H2 is 30-70%.

[0041] This application also provides a non-oriented silicon steel sheet prepared by the aforementioned processing method, the chemical composition of which, by mass percentage, includes: C≤0.0025%, S≤0.0015%, N≤0.002%, Si: 3.25~3.65%, Al: 0.85~1.25%, Mn: 0.27~0.47%, Sn: 0.05~0.08%, P≤0.02%, Nb+V≤0.006%, Ti≤0.002%, Cu≤0.03%, Mo≤0.006%, Ni+Cr≤0.06%, with the remainder being Fe and unavoidable impurities.

[0042] Based on the aforementioned processing methods, the high content of Si and Al is controlled to improve the resistivity of the steel plate and reduce iron loss. A certain amount of Mn is added to improve the stamping and machinability of the silicon steel, and can further enhance its resistivity. A certain amount of Sn is added to prevent nitrogen accumulation and the formation of an internal oxide layer during annealing, thus improving the magnetic properties of the silicon steel plate. P enhances solid solution strengthening, increasing the strength of the steel plate. The content of impurity elements such as C, S, N, Nb, V, Ti, Cu, Mo, Ni, and Cr is controlled to avoid deteriorating the magnetic properties.

[0043] The functions of each chemical component have the following characteristics:

[0044] C, S, N: For non-oriented silicon steel, C, S, and N are all harmful elements. Increased C content leads to increased iron loss, decreased magnetic induction intensity, and also causes magnetic aging. S easily forms MnS with Mn; the fine MnS particles act as pinning agents, hindering grain growth during annealing and leading to increased iron loss. In addition, S also increases the brittleness of non-oriented silicon steel. N easily forms AlN and TiN inclusions with Al and Ti, which are detrimental to grain growth during annealing and the magnetic properties of the steel plate. Therefore, in this application, the C content is controlled below 0.0025%, the S content is controlled below 0.0015%, and the N content is controlled below 0.002%.

[0045] Si and Al: Si and Al are the main functional elements for improving resistivity and reducing iron loss. Therefore, in this application, the Si content is controlled at 3.25-3.65%, and the Al content is controlled at 0.85-1.25%.

[0046] Mn: If the Si and Al content is too high, the stamping properties of silicon steel sheets will deteriorate. Adding an appropriate amount of Mn can improve stamping properties and machinability. Mn can increase resistivity and suppress hot brittleness caused by S. However, if too much Mn is added, the strength and hardness of the steel sheet will increase, making rolling and winding difficult. Therefore, the Mn content in this application is controlled at 0.27-0.47%.

[0047] Sn: Sn is a grain boundary segregating element. During annealing, it can hinder the nucleation of {111} grains at the original grain boundary, creating space for the nucleation and growth of {100} and {110} grains, thereby increasing the magnetic induction intensity. In addition, Sn can prevent nitrogen accumulation and the formation of an internal oxide layer during annealing, thus improving magnetic properties. However, excessive Sn content can lead to grain boundary embrittlement in steel plates, which is detrimental to cold rolling and also increases production costs. Therefore, the Sn content in this application is controlled at 0.05% to 0.08%.

[0048] P: P has a solid solution strengthening effect in non-oriented silicon steel, which can improve the strength of the steel plate. However, P will segregate along the grain boundaries. The increase of its content will make the cold ductility worse and increase the risk of strip breakage during rolling. Therefore, the P content in this application is controlled below 0.02%.

[0049] Nb, V, Ti, Cu, Mo, Ni, Cr: For non-oriented silicon steel, Nb, V, Ti, Cu, Mo, Ni, and Cr are all impurity elements. Although they can improve strength, they deteriorate magnetic properties. Nb, V, and Ti can form carbon and nitrogen compounds with C and N, which undergo solid solution treatment during hot rolling. These compounds then disperse and precipitate during subsequent rolling and coiling, hindering grain growth and leading to poorer magnetic properties. Increased Cu content easily causes hot brittleness. Therefore, the content of these elements should be minimized, controlled at Nb+V ≤ 0.006%, Ti ≤ 0.002%, Cu ≤ 0.03%, Mo ≤ 0.006%, and Ni+Cr ≤ 0.06%.

[0050] Furthermore, when the thickness of the non-oriented silicon steel sheet is 0.25 mm, the iron loss P 1.0 / 400 ≤12W / kg, magnetic induction intensity B 5000 ≥1.64T; When the thickness of the non-oriented silicon steel sheet is 0.30mm, the iron loss P 1.0 / 400 ≤14W / kg, magnetic induction intensity B 5000 ≥1.65T; When the thickness of the non-oriented silicon steel sheet is 0.35mm, the iron loss P 1.0 / 400 ≤17W / kg, magnetic induction intensity B 5000 ≥1.68T.

[0051] Furthermore, when the thickness of the non-oriented silicon steel sheet is 0.25 mm, the thickness of the hot-rolled sheet is 2.10 mm; when the thickness of the non-oriented silicon steel is 0.30 mm, the thickness of the hot-rolled sheet is 2.20 mm; and when the thickness of the non-oriented silicon steel is 0.35 mm, the thickness of the hot-rolled sheet is 2.30 mm.

[0052] The technical solution of this application will be further described below with reference to some specific embodiments.

[0053] Example 1

[0054] The chemical composition of a non-oriented silicon steel sheet provided in Example 1, by mass percentage, includes: C: 0.0015%, S: 0.0013%, N: 0.0018%, Si: 3.34%, Al: 1.21%, Mn: 0.31%, Sn: 0.06%, P: 0.018%, Nb: 0.0032%, V: 0.0024%, Ti: 0.0017%, Cu: 0.027%, Mo: 0.005%, Ni: 0.027%, Cr: 0.025%, with the remainder being Fe and unavoidable impurities.

[0055] The processing method of the non-oriented silicon steel sheet includes the following steps:

[0056] Heating process: The continuously cast billet is placed in a heating furnace for heating at a temperature of 1089℃ and a holding time of 288min;

[0057] Hot rolling process: The heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain a hot-rolled plate with a thickness of 2.3mm. The circumferential speed ratio of the upper and lower work rolls in the 6th pass of finish rolling is 1:1.01, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass of finish rolling is 1.01:1. The final rolling temperature is controlled at 744℃, the coiling temperature is 610℃, the coiling holding time is 65min, and after holding, the coil is uncoiled and air-cooled to room temperature.

[0058] Normalizing process: The hot-rolled plate is fed into the normalizing furnace for normalizing treatment. The atmosphere in the normalizing furnace is pure N2, the normalizing temperature is 845℃, the heating rate is 52℃ / s, and the holding time is 23s.

[0059] Cold rolling process: The normalized hot-rolled plate is cold rolled, and the first pass reduction rate of cold rolling is controlled at 38.2%.

[0060] Annealing process: The cold-rolled sheet is annealed under a protective atmosphere of H2 and N2 mixed atmosphere, wherein the volume percentage of H2 is 30-70%, the annealing temperature is 965℃, and the holding time is 217s.

[0061] Coating process: An insulating layer is applied to the surface of the annealed cold-rolled sheet to produce a non-oriented silicon steel sheet with a thickness of 0.35 mm.

[0062] Example 2

[0063] The chemical composition of a non-oriented silicon steel sheet provided in Example 2, by mass percentage, includes: C: 0.0015%, S: 0.0013%, N: 0.0018%, Si: 3.34%, Al: 1.21%, Mn: 0.31%, Sn: 0.06%, P: 0.018%, Nb: 0.0032%, V: 0.0024%, Ti: 0.0017%, Cu: 0.027%, Mo: 0.005%, Ni: 0.027%, Cr: 0.025%, with the remainder being Fe and unavoidable impurities.

[0064] The processing method of the non-oriented silicon steel sheet includes the following steps:

[0065] Heating process: The continuously cast billet is placed in a heating furnace for heating at a temperature of 1127℃ and a holding time of 273 minutes;

[0066] Hot rolling process: The heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain a hot-rolled plate with a thickness of 2.2 mm. The circumferential speed ratio of the upper and lower work rolls in the 6th pass of finish rolling is 1:1.02, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass of finish rolling is 1.02:1. The final rolling temperature is controlled at 782℃, the coiling temperature is 653℃, the coiling holding time is 73 min, and after holding, the coil is uncoiled and air-cooled to room temperature.

[0067] Normalizing process: The hot-rolled plate is fed into the normalizing furnace for normalizing treatment. The atmosphere inside the normalizing furnace is pure N2, the normalizing temperature is 838℃, the heating rate is 78℃ / s, and the holding time is 40s.

[0068] Cold rolling process: The normalized hot-rolled plate is cold rolled, and the first pass reduction rate of cold rolling is controlled at 39.5%.

[0069] Annealing process: The cold-rolled sheet is annealed under a protective atmosphere of H2 and N2 mixed atmosphere, wherein the volume percentage of H2 is 30-70%, the annealing temperature is 958℃, and the holding time is 307s.

[0070] Coating process: An insulating layer is applied to the surface of the annealed cold-rolled sheet to produce a non-oriented silicon steel sheet with a thickness of 0.30 mm.

[0071] Example 3

[0072] The chemical composition of a non-oriented silicon steel sheet provided in Example 3, by mass percentage, includes: C: 0.0015%, S: 0.0013%, N: 0.0018%, Si: 3.34%, Al: 1.21%, Mn: 0.31%, Sn: 0.06%, P: 0.018%, Nb: 0.0032%, V: 0.0024%, Ti: 0.0017%, Cu: 0.027%, Mo: 0.005%, Ni: 0.027%, Cr: 0.025%, with the remainder being Fe and unavoidable impurities.

[0073] The processing method of the non-oriented silicon steel sheet includes the following steps:

[0074] Heating process: The continuously cast billet is placed in a heating furnace for heating at a temperature of 1157℃ and a holding time of 232 minutes;

[0075] Hot rolling process: The heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain a hot-rolled plate with a thickness of 2.1 mm. The circumferential speed ratio of the upper and lower work rolls in the 6th pass of finish rolling is 1:1.04, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass of finish rolling is 1.04:1. The final rolling temperature is controlled at 750℃, the coiling temperature is 643℃, the coiling holding time is 78 min, and after holding, the coil is uncoiled and air-cooled to room temperature.

[0076] Normalizing process: The hot-rolled plate is fed into the normalizing furnace for normalizing treatment. The atmosphere inside the normalizing furnace is pure N2, the normalizing temperature is 823℃, the heating rate is 68℃ / s, and the holding time is 47s.

[0077] Cold rolling process: The normalized hot-rolled plate is cold rolled, and the first pass reduction rate of cold rolling is controlled at 41.8%.

[0078] Annealing process: The cold-rolled sheet is annealed under a protective atmosphere of H2 and N2 mixed atmosphere, wherein the volume percentage of H2 is 30-70%, the annealing temperature is 943℃, and the holding time is 377s.

[0079] Coating process: An insulating layer is applied to the surface of the annealed cold-rolled sheet to produce a non-oriented silicon steel sheet with a thickness of 0.25 mm.

[0080] Example 4

[0081] The chemical composition of a non-oriented silicon steel sheet provided in Example 4, by mass percentage, includes: C: 0.0020%, S: 0.0011%, N: 0.0011%, Si: 3.61%, Al: 0.89%, Mn: 0.44%, Sn: 0.08%, P: 0.016%, Nb: 0.0021%, V: 0.0027%, Ti: 0.0015%, Cu: 0.025%, Mo: 0.004%, Ni: 0.025%, Cr: 0.029%, with the remainder being Fe and unavoidable impurities.

[0082] The processing method of the non-oriented silicon steel sheet includes the following steps:

[0083] Heating process: The continuously cast billet is placed in a heating furnace for heating at a temperature of 1173℃ and a holding time of 265 minutes;

[0084] Hot rolling process: The heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain a hot-rolled plate with a thickness of 2.3mm. The circumferential speed ratio of the upper and lower work rolls in the 6th pass of finish rolling is 1:1.02, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass of finish rolling is 1.02:1. The final rolling temperature is controlled at 723℃, the coiling temperature is 631℃, the coiling holding time is 86min, and after holding, the coil is uncoiled and air-cooled to room temperature.

[0085] Normalizing process: The hot-rolled plate is fed into the normalizing furnace for normalizing treatment. The atmosphere in the normalizing furnace is pure N2, the normalizing temperature is 835℃, the heating rate is 70℃ / s, and the holding time is 28s.

[0086] Cold rolling process: The normalized hot-rolled plate is cold rolled, and the first pass reduction rate of cold rolling is controlled at 40.7%.

[0087] Annealing process: The cold-rolled sheet is annealed under a protective atmosphere of H2 and N2 mixed atmosphere, wherein the volume percentage of H2 is 30-70%, the annealing temperature is 955℃, and the holding time is 389s;

[0088] Coating process: An insulating layer is applied to the surface of the annealed cold-rolled sheet to produce a non-oriented silicon steel sheet with a thickness of 0.35 mm.

[0089] Example 5

[0090] The chemical composition of a non-oriented silicon steel sheet provided in Example 5, by mass percentage, includes: C: 0.0020%, S: 0.0011%, N: 0.0011%, Si: 3.61%, Al: 0.89%, Mn: 0.44%, Sn: 0.08%, P: 0.016%, Nb: 0.0021%, V: 0.0027%, Ti: 0.0015%, Cu: 0.025%, Mo: 0.004%, Ni: 0.025%, Cr: 0.029%, with the remainder being Fe and unavoidable impurities.

[0091] The processing method of the non-oriented silicon steel sheet includes the following steps:

[0092] Heating process: The continuously cast billet is placed in a heating furnace for heating at a temperature of 1094℃ and a holding time of 210min;

[0093] Hot rolling process: The heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain a hot-rolled plate with a thickness of 2.2 mm. The circumferential speed ratio of the upper and lower work rolls in the 6th pass of finish rolling is 1:1.03, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass of finish rolling is 1.03:1. The final rolling temperature is controlled at 766℃, the coiling temperature is 624℃, the coiling holding time is 81 min, and after holding, the coil is uncoiled and air-cooled to room temperature.

[0094] Normalizing process: The hot-rolled plate is fed into the normalizing furnace for normalizing treatment. The atmosphere inside the normalizing furnace is pure N2, the normalizing temperature is 827℃, the heating rate is 51℃ / s, and the holding time is 33s.

[0095] Cold rolling process: The normalized hot-rolled plate is cold rolled, and the first pass reduction rate of cold rolling is controlled at 38.9%.

[0096] Annealing process: The cold-rolled sheet is annealed under a protective atmosphere of H2 and N2 mixed atmosphere, wherein the volume percentage of H2 is 30-70%, the annealing temperature is 947℃, and the holding time is 268s.

[0097] Coating process: An insulating layer is applied to the surface of the annealed cold-rolled sheet to produce a non-oriented silicon steel sheet with a thickness of 0.30 mm.

[0098] Example 6

[0099] The chemical composition of a non-oriented silicon steel sheet provided in Example 6, by mass percentage, includes: C: 0.0020%, S: 0.0011%, N: 0.0011%, Si: 3.61%, Al: 0.89%, Mn: 0.44%, Sn: 0.08%, P: 0.016%, Nb: 0.0021%, V: 0.0027%, Ti: 0.0015%, Cu: 0.025%, Mo: 0.004%, Ni: 0.025%, Cr: 0.029%, with the remainder being Fe and unavoidable impurities.

[0100] The processing method of the non-oriented silicon steel sheet includes the following steps:

[0101] Heating process: The continuously cast billet is placed in a heating furnace for heating at a temperature of 1144℃ and a holding time of 225 minutes;

[0102] Hot rolling process: The heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain a hot-rolled plate with a thickness of 2.1 mm. The circumferential speed ratio of the upper and lower work rolls in the 6th pass of finish rolling is 1:1.01, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass of finish rolling is 1.01:1. The final rolling temperature is controlled at 794℃, the coiling temperature is 656℃, the coiling holding time is 68 min, and after holding, the coil is uncoiled and air-cooled to room temperature.

[0103] Normalizing process: The hot-rolled plate is fed into the normalizing furnace for normalizing treatment. The atmosphere inside the normalizing furnace is pure N2, the normalizing temperature is 842℃, the heating rate is 63℃ / s, and the holding time is 37s.

[0104] Cold rolling process: The normalized hot-rolled plate is cold rolled, and the first pass reduction rate of cold rolling is controlled at 40.3%.

[0105] Annealing process: The cold-rolled sheet is annealed under a protective atmosphere of H2 and N2 mixed atmosphere, wherein the volume percentage of H2 is 30-70%, the annealing temperature is 962℃, and the holding time is 256s;

[0106] Coating process: An insulating layer is applied to the surface of the annealed cold-rolled sheet to produce a non-oriented silicon steel sheet with a thickness of 0.25 mm.

[0107] Table 1

[0108]

[0109] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0110] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this application.

Claims

1. A method for processing non-oriented silicon steel sheets, characterized in that, This includes sequentially heating, hot rolling, normalizing, cold rolling, annealing, and coating processes for the continuously cast billet, wherein: During the heating process, the continuous casting billet is heated to 1080–1180℃ and held for 200–300 minutes. In the hot rolling process, the heated continuous casting billet is fed into the rolling mill for rough rolling and 7 passes of finish rolling to obtain the hot rolled plate. The 6th and 7th passes of finish rolling are asynchronous rolling. In the normalizing process, the hot-rolled plate is fed into a normalizing furnace for normalizing treatment. The normalizing temperature is T1 = 15 × [6.7 - ([Si] + 0.72 × [Al]) × 100]. 2 +760×[1-|v7 up / v7 down -1|]℃, heating rate is 50~80℃ / s, holding time is 20~50s, where [Si] and [Al] are the mass percentages of Si and Al in the continuously cast billet, v7 up v7 is the circumferential speed of the upper work roll in the 7th pass of the finishing mill. down The circumferential speed of the lower work roll in the 7th pass of finishing mill; In the cold rolling process, the normalized hot-rolled plate is cold-rolled to obtain a cold-rolled plate; In the annealing process, the cold-rolled sheet is continuously annealed at a temperature of T2 = T1 + 120℃ and a holding time of 200 to 400 seconds.

2. The processing method for non-oriented silicon steel sheet according to claim 1, characterized in that, In the hot rolling process, the circumferential speed ratio of the upper and lower work rolls in the 6th pass is 1:1.01 to 1:1.04, and the circumferential speed ratio of the upper and lower work rolls in the 7th pass is the opposite of that in the 6th pass.

3. The processing method for non-oriented silicon steel sheet according to claim 1, characterized in that, In the hot rolling process, the final rolling temperature is 720-800℃, the coiling temperature is 600-660℃, the coiling holding time is 60-90 minutes, and after holding, the coil is uncoiled and air-cooled to room temperature.

4. The processing method for non-oriented silicon steel sheet according to claim 3, characterized in that, The recrystallized grain size of the hot-rolled plate surface layer is 2-18 μm. The surface layer includes an upper surface layer and a lower surface layer of the same thickness, and the sum of the thicknesses of the upper and lower surface layers accounts for 20-35% of the thickness of the hot-rolled plate.

5. The processing method for non-oriented silicon steel sheet according to claim 4, characterized in that, The average recrystallized grain size of the surface layer of the normalized hot-rolled plate is 20–45 μm, and the average recrystallized grain size of the intermediate layer is 80–110 μm.

6. The processing method of non-oriented silicon steel sheet according to claim 5, characterized in that, The average recrystallized grain size of the annealed cold-rolled sheet is 120–150 μm.

7. As described in claim 1, characterized in that, The thickness of the hot-rolled plate obtained after hot rolling is 2.10 to 2.30 mm, and the thickness of the cold-rolled plate obtained after cold rolling is 0.25 to 0.35 mm.

8. The processing method of non-oriented silicon steel sheet according to claim 1, characterized in that, In the normalizing process, the atmosphere inside the normalizing furnace is pure N2, and the normalizing temperature fluctuates within a range of 5°C above and below temperature T1. During the annealing process, the protective atmosphere is a mixture of H2 and N2, wherein the volume percentage of H2 is 30-70%.

9. A non-oriented silicon steel sheet, characterized in that, The non-oriented silicon steel sheet prepared by the processing method described in claim 1 has the following chemical composition by mass percentage: C≤0.0025%, S≤0.0015%, N≤0.002%, Si: 3.25~3.65%, Al: 0.85~1.25%, Mn: 0.27~0.47%, Sn: 0.05~0.08%, P≤0.02%, Nb+V≤0.006%, Ti≤0.002%, Cu≤0.03%, Mo≤0.006%, Ni+Cr≤0.06%, with the remainder being Fe and unavoidable impurities.

10. The non-oriented silicon steel sheet according to claim 9, characterized in that, When the thickness of the non-oriented silicon steel sheet is 0.25 mm, the iron loss P 1.0 / 400 ≤12W / kg, magnetic induction intensity B 5000 ≥1.64T; when the thickness of the non-oriented silicon steel sheet is 0.30mm, the iron loss P 1.0 / 400 ≤14W / kg, magnetic induction intensity B 5000 ≥1.65T; when the thickness of the non-oriented silicon steel sheet is 0.35mm, the iron loss P 1.0 / 400 ≤17W / kg, magnetic induction intensity B 5000 ≥1.68T.

11. The non-oriented silicon steel sheet according to claim 10, characterized in that, When the thickness of the non-oriented silicon steel sheet is 0.25 mm, the thickness of the hot-rolled sheet is 2.10 mm; when the thickness of the non-oriented silicon steel is 0.30 mm, the thickness of the hot-rolled sheet is 2.20 mm; when the thickness of the non-oriented silicon steel is 0.35 mm, the thickness of the hot-rolled sheet is 2.30 mm.

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