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

Abstract

This invention discloses a method for preparing non-oriented silicon steel sheets. The method includes continuous casting, slab heating, billet preparation, intermediate billet heat treatment, hot rolling, pickling, cold rolling, annealing, and coating processes. Specifically: the continuously cast slab is heated to a soaking temperature T1 = 1100℃ - 30 × [Si] - 20 × [Al] ± 10℃; an intermediate billet is produced through multiple rolling passes; the intermediate billet undergoes high-temperature reduction heat treatment in a tunnel furnace under a reducing atmosphere, with a holding temperature of 1000–1050℃ and a holding time of 15–30 min; the hot rolling finishing process has a final rolling temperature of 880–900℃ and a coiling temperature of 700–720℃; during annealing, the heating rate is 30–50℃ / s, the soaking temperature is 980–1020℃, and the cooling rate is 10–15℃ / s. This eliminates the need for a normalizing process, achieves excellent magnetic properties, improves corrugation defects and surface defects such as oxide scale indentation and cracks, and reduces production costs.

Description

Technical Field

[0001] This invention belongs to the field of steel material preparation technology, and relates to a non-oriented silicon steel sheet and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, their drive motors are evolving towards higher speeds, higher power densities, and higher efficiency. As motor speed increases, core losses rise sharply. Drive motor cores primarily use non-oriented silicon steel.

[0003] Excellent magnetic properties are the most important performance requirement for non-oriented silicon steel. In addition to magnetic properties, non-oriented silicon steel must also have excellent surface quality.

[0004] However, in existing conventional manufacturing methods for non-oriented silicon steel, due to the high silicon content, silicon particles tend to accumulate more easily at the interface between the inner oxide scale and the matrix, resulting in a dense iron oxide layer (Fe2SiO4). This oxide layer has high viscosity and is difficult to remove completely. If it is pressed into the steel sheet during hot rolling, it will cause surface quality problems. In one known technique, the surface oxide scale of the steel billet is flame-cleaned. However, flame cleaning requires the billet to be cooled to room temperature first, and then heated again for hot rolling. This process of cooling and heating is extremely prone to causing cracks at the edges of the billet, affecting the surface quality of the non-oriented silicon steel.

[0005] Furthermore, in existing conventional methods for producing high-grade non-oriented silicon steel, the hot-rolled coil is typically subjected to normalizing treatment before cold rolling. This normalizing treatment allows the deformed ferrite fibers to recrystallize, thereby improving the magnetic properties of the finished product and eliminating surface corrugation defects. However, adding a normalizing treatment step not only complicates the production process of high-grade non-oriented silicon steel and increases production difficulty, but also increases equipment investment and significantly raises production costs. Summary of the Invention

[0006] To address at least one technical problem in the existing technology, namely poor surface quality, poor magnetic properties, and high production difficulty, the present invention aims to provide a non-oriented silicon steel sheet and its preparation method.

[0007] To achieve the above-mentioned objective, one embodiment of the present invention provides a method for preparing non-oriented silicon steel sheet. The method includes continuous casting, slab heating, billet preparation, intermediate billet heat treatment, hot rolling, pickling, cold rolling, annealing, and coating processes, wherein...

[0008] Slab heating process: After leaving the continuous casting equipment, the continuously cast slab is heated in a heating furnace, and the soaking temperature is T1 = T 10 ±10℃, furnace time 180~200min, T 10=1100℃-30×[Si]-20×[Al], where [Si] and [Al] are 100 times the mass percentages of Si and Al in the continuously cast billet;

[0009] Billeting process: After the continuously cast billet leaves the heating furnace, it is rolled in multiple passes to make an intermediate billet; the reduction rate of each rolling pass is 20-22%, and the exit temperature of the last rolling pass is T2 = 900±25℃.

[0010] Intermediate billet heat treatment process: The intermediate billet prepared in the billet-making process is put into a tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. The holding temperature is 1000-1050℃ and the holding time is 15-30min.

[0011] Hot rolling finishing process: finishing rolling temperature is 880~900℃, coiling temperature is 700~720℃;

[0012] Annealing process: heating rate is 30-50℃ / s, soaking temperature is 980-1020℃, cooling rate is 10-15℃ / s, and the protective atmosphere is 20% H2 + 80% N2.

[0013] Preferably, the chemical composition of the continuously cast billet, by mass percentage, is: C≤0.0025%, S≤0.0015%, Si:2.50~3.40%, Al:0.30~1.00%, Mn:0.20~0.80%, P:0.02~0.04%, Nb≤0.004%, V≤0.004%, Ti≤0.004%, Ni≤0.03%, Cr≤0.03%, Cu≤0.03%, N≤0.002%, with the remainder being Fe and unavoidable inclusions.

[0014] Preferably, the preparation method does not include normalization treatment.

[0015] Preferably, the annealing process has a dew point of 10–20°C and a unit tension of 2–3 N / mm. 2 .

[0016] Preferably, the thickness of the continuously cast billet is 200-250 mm, and the thickness of the intermediate billet is 100-125 mm.

[0017] Preferably, the hot rolling finishing process yields a hot-rolled coil with a thickness of 2.00–2.30 mm or 2.20–2.80 mm.

[0018] Preferably, the method further includes,

[0019] The billet assembly process, located between the intermediate billet heat treatment process and the hot rolling and finishing process, involves applying a high-temperature resistant insulating coating to the upper and lower surfaces of the intermediate billet, then arranging N intermediate billets into a stacked billet, and welding the four sides of the stacked billet to form a composite billet.

[0020] And, the slitting process located before or after the cold rolling process: the composite hot-rolled coil or composite cold-rolled coil converted from the composite billet is divided into N single-layer hot-rolled coils or N single-layer cold-rolled coils by a slitting machine.

[0021] Preferably, the high-temperature resistant insulating coating contains MgO, and it mainly uses MgO high-temperature resistant coating.

[0022] Preferably, in the hot rolling finishing process: the composite billet is heated in a heating furnace at a temperature of 1090–1130°C for a duration of 180–200 min; after exiting the heating furnace, the composite billet is rolled to obtain a composite hot-rolled coil.

[0023] Preferably, the slitting process is performed before the pickling process;

[0024] The cold rolling process involves cold rolling a single-layer hot-rolled coil once on a single-stand cold rolling mill to produce a single-layer cold-rolled coil with a cold rolling reduction rate of 74-87% and a thickness of 0.15-0.30 mm.

[0025] Preferably, the slitting process is located between the cold rolling process and the annealing process;

[0026] The cold rolling process involves cold rolling the composite hot-rolled coil on a single-stand cold rolling mill to produce a composite cold-rolled coil with a cold rolling reduction rate of 73-86% and a thickness of 0.30-0.60 mm.

[0027] Preferably, the thickness of the single-layer cold-rolled coil is 0.15 to 0.30 mm.

[0028] Preferably, the thicknesses of the N intermediate blanks are the same or different.

[0029] Preferably, the reducing atmosphere is 90% H2 + 10% H2S.

[0030] To achieve the above-mentioned objective, one embodiment of the present invention provides a non-oriented silicon steel sheet, which is prepared by the aforementioned preparation method.

[0031] Preferably, the thickness of the non-oriented silicon steel sheet is 0.15–0.30 mm, and the iron loss P 1.5 / 50 ≤2.35W / kg, P 1.0 / 400 ≤14.5W / kg, magnetic induction intensity B 5000≥1.66T; or, the thickness of the non-oriented silicon steel sheet is 0.15~0.30mm, and the iron loss P 1.5 / 50 ≤2.20W / kg, P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.66T.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: After the billet is opened, the obtained intermediate billet is directly put into the tunnel furnace and subjected to high-temperature reduction heat treatment in a reducing atmosphere. This can improve the rolling structure after rough rolling, coarsen the grain size before finishing rolling, and reduce the hot rolling load. On the other hand, it can improve the uniformity and stability of the finishing rolling temperature, improve the structure after hot finishing rolling, reduce the normalizing heat treatment process after hot rolling, avoid the corrugated defects on the surface of high silicon steel after cold rolling, and further reduce production costs. Furthermore, the high-temperature reduction heat treatment of the intermediate billet in a reducing atmosphere can reduce the oxide scale loss of the intermediate billet in ordinary heating furnaces and improve the yield of the intermediate billet. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0034] This invention provides a method for preparing non-oriented silicon steel sheets, and the non-oriented silicon steel sheets obtained by the method. The method includes continuous casting, slab heating, billet preparation, intermediate billet heat treatment, hot rolling, pickling, cold rolling, annealing, and coating processes, thereby producing the finished non-oriented silicon steel product.

[0035] Specifically, the slab heating process: After leaving the continuous casting equipment, the continuously cast slab is heated in a heating furnace, and the soaking temperature is T1 = T 10 ±10℃, furnace time 180~200min, T 10 =1100℃

[0036] -30×[Si]-20×[Al], where [Si] and [Al] are 100 times the mass percentages of Si and Al in the continuously cast billet;

[0037] Billeting process: After the continuously cast billet leaves the heating furnace, it is rolled in multiple passes to make an intermediate billet; the reduction rate of each rolling pass is 20-22%, and the exit temperature of the last rolling pass is T2 = 900±25℃.

[0038] Intermediate billet heat treatment process: The intermediate billet prepared in the billet-making process is put into a tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. The holding temperature is 1000-1050℃ and the holding time is 15-30min.

[0039] Hot rolling finishing process: finishing rolling temperature is 880~900℃, coiling temperature is 700~720℃;

[0040] Annealing process: heating rate is 30-50℃ / s, soaking temperature is 980-1020℃, cooling rate is 10-15℃ / s, and the protective atmosphere is 20% H2 + 80% N2.

[0041] Thus, compared with the prior art, the beneficial effects of the present invention are at least as follows: After the initial rolling, the resulting intermediate billet is directly fed into a tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. This improves the rolling microstructure after rough rolling, coarsens the grain size before finishing rolling, and reduces the hot rolling load. It also improves the uniformity and stability of the finishing rolling temperature, improves the microstructure after hot finishing rolling, reduces the normalizing heat treatment process after hot rolling, avoids corrugated defects on the surface of high-silicon steel after cold rolling, and further reduces production costs. Furthermore, the high-temperature reduction heat treatment of the intermediate billet in a reducing atmosphere reduces the loss of oxide scale in ordinary heating furnaces and improves the yield of the intermediate billet.

[0042] The basic inventive principle of the present invention has been described above. Next, various embodiments based on the basic inventive principle of the present invention will be described in detail.

[0043] <First Implementation Method>

[0044] This embodiment provides a method for preparing a non-oriented silicon steel sheet, and a non-oriented silicon steel sheet obtained by the method.

[0045] In this embodiment, the preparation method includes sequentially performed steps such as slab continuous casting, slab heating, rough rolling, intermediate slab heat treatment, hot rolling, pickling, cold rolling, annealing, and coating. The entire method does not require normalization treatment, thereby producing a non-oriented silicon steel product. These steps are described in detail below.

[0046] Slab continuous casting process

[0047] Molten steel is poured into a continuous casting billet using a continuous casting equipment. The thickness of the billet is 200–250 mm, preferably 220 mm.

[0048] The chemical composition of the continuously cast billet meets the requirements for non-oriented silicon steel, and can be implemented using the chemical composition of existing known non-oriented silicon steel.

[0049] In a preferred embodiment, the chemical composition of the continuously cast billet, by mass percentage, is: C ≤ 0.0025%, S ≤ 0.0015%, Si: 2.50–3.40%, Al: 0.30–1.00%, Mn: 0.20–0.80%, P: 0.02–0.04%, Nb ≤ 0.004%, V ≤ 0.004%, Ti ≤ 0.004%, Ni ≤ 0.03%, Cr ≤ 0.03%, Cu ≤ 0.03%, N ≤ 0.002%, with the remainder being Fe and unavoidable inclusions. Based on this chemical composition, high-grade non-oriented silicon steel can be produced.

[0050] [Slab heating process]

[0051] After leaving the continuous casting equipment, the continuously cast billet is heated in a heating furnace, with a soaking temperature of T1 = T 10 ±10℃, furnace time 180~200min. Among them, T 10 =1100℃ - 30 × [Si] - 20 × [Al], where [Si] and [Al] are 100 times the mass percentage of Si and Al in the continuously cast billet. For example, if the mass percentage of Si in the continuously cast billet is 2.5%, then the value of [Si] in the formula is 2.5. In this way, by adopting this soaking temperature, the surface quality of the continuously cast billet can be guaranteed and excellent microstructure can be obtained in subsequent billet processing, thereby improving the performance of the final non-oriented silicon steel product.

[0052] Preferably, the continuously cast billet is directly heated in a heating furnace after leaving the continuous casting equipment. That is, the continuously cast billet is heated while still warm.

[0053] Rough rolling process

[0054] After leaving the heating furnace, the continuously cast billet is rolled in multiple passes to produce an intermediate billet. The thickness of the intermediate billet is 100–125 mm, preferably 110 mm.

[0055] In a further optimized configuration, the reduction rate per rolling pass is 20–22%, and the exit temperature of the final rolling pass is T2 = 900 ± 25℃. More preferably, T2 = T1 - 100℃. Such temperature and reduction rate control, combined with the aforementioned control of the soaking temperature, can further improve the billet opening effect and ensure the surface quality and microstructure of the intermediate billet.

[0056] Furthermore, in this billet-making process, it is preferable to use three rolling passes to produce intermediate billets.

[0057] Intermediate billet heat treatment process

[0058] The intermediate billet obtained from the roughing process is fed into a tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. The holding temperature is 1000–1050℃, and the holding time is 15–30 minutes. Thus, after roughing, the intermediate billet is directly fed into the tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. This improves the rolling microstructure after roughing, coarsens the grain size before finishing, and reduces the hot rolling load. Furthermore, it enhances the uniformity and stability of the finishing rolling temperature, improves the microstructure after hot finishing, reduces the need for normalizing heat treatment after hot rolling, avoids corrugated defects on the surface of high-silicon steel after cold rolling, and further reduces production costs. Additionally, the high-temperature reduction heat treatment in a reducing atmosphere reduces oxide scale loss in ordinary heating furnaces, increasing the yield of the intermediate billet.

[0059] Hot rolling finishing process

[0060] The intermediate billet obtained after heat treatment is precision rolled and coiled to obtain hot-rolled coil.

[0061] The final rolling temperature of hot-rolled finishing is 880–900℃, the coiling temperature is 700–720℃, and the thickness of hot-rolled coil is 2.00–2.30 mm.

[0062] This can further improve the microstructure, surface quality, and shape of non-oriented silicon steel products, thereby improving their performance, especially their magnetic properties.

[0063] Pickling process

[0064] The hot-rolled coils obtained from the hot-rolling finishing process are directly shot-blasted and pickled to remove the surface oxide scale.

[0065] Cold rolling process

[0066] After pickling, the hot-rolled coil is cold-rolled on a single-stand cold rolling mill to produce cold-rolled coil.

[0067] Among them, a 20-roll single-stand cold rolling mill is preferred for single-stand cold rolling mill.

[0068] Preferably, a single cold rolling process is used, with a cold rolling reduction rate of 87-90% and a thickness of 0.20-0.30 mm for the cold-rolled coil.

[0069] Annealing process

[0070] Cold-rolled coils are annealed in a continuous annealing furnace to obtain annealed strip steel.

[0071] During the annealing process, the heating rate is 30–50℃ / s, the soaking temperature is 980–1020℃, the cooling rate is 10–15℃ / s, the protective atmosphere is 20% H2 + 80% N2, the dew point is 10–20℃, and the unit tension is 2–3 N / mm.2 .

[0072] Coating process

[0073] An insulating coating with a thickness of 0.5 to 0.8 μm is applied to each surface of the annealed strip steel, thus obtaining the finished non-oriented silicon steel product.

[0074] Understandably, the actual thickness of the resulting non-oriented silicon steel product is the sum of the thickness of the corresponding cold-rolled coil and the thicknesses of the upper and lower surface insulating coatings of the corresponding annealed strip. For example, for a cold-rolled coil with a thickness of 0.15 mm, the thickness of both the upper and lower surface insulating coatings of the corresponding annealed strip is 0.5 μm, then the thickness of the corresponding non-oriented silicon steel product is 0.30 mm + 0.5 μm + 0.5 μm = 0.3010 mm. However, in this application, the coating thickness is very small relative to the thickness of the cold-rolled coil, and the thickness of the non-oriented silicon steel product is basically the same as the thickness of the cold-rolled coil. Therefore, the thickness of the cold-rolled coil is taken as the thickness of the non-oriented silicon steel product.

[0075] The preparation method described in this embodiment has been described in detail above. Next, this embodiment also provides a non-oriented silicon steel sheet, which is prepared by the above preparation method.

[0076] The thickness of the non-oriented silicon steel sheet is 0.2–0.3 mm, and the iron loss P 1.5 / 50 ≤2.35W / kg, P 1.0 / 400 ≤14.5W / kg, magnetic induction intensity B 5000 ≥1.66T.

[0077] Regarding the chemical composition, the non-oriented silicon steel sheet, by mass percentage, contains: C ≤ 0.0025%, S ≤ 0.0015%, Si: 2.50–3.40%, Al: 0.30–1.00%, Mn: 0.20–0.80%, P: 0.02–0.04%, Nb ≤ 0.004%, V ≤ 0.004%, Ti ≤ 0.004%, Ni ≤ 0.03%, Cr ≤ 0.03%, Cu ≤ 0.03%, N ≤ 0.002%, with the remainder being Fe and unavoidable inclusions. Based on this chemical composition, the non-oriented silicon steel sheet is a high-grade non-oriented silicon steel with excellent magnetic properties.

[0078] It is understood that the chemical composition of the non-oriented silicon steel sheet is the same as that of the continuous casting billet prepared by the aforementioned preparation method.

[0079] Compared with the prior art, the beneficial effects of this embodiment are at least as follows: After the billet is opened, the obtained intermediate billet is directly put into the tunnel furnace and subjected to high-temperature reduction heat treatment in a reducing atmosphere. This can improve the rolling structure after rough rolling, coarsen the grain size before finishing rolling, and reduce the hot rolling load. On the other hand, it can improve the uniformity and stability of the finishing rolling temperature, improve the structure after hot finishing rolling, reduce the normalizing heat treatment process after hot rolling, avoid the corrugated defects on the surface of high silicon steel after cold rolling, and further reduce production costs. Furthermore, the high-temperature reduction heat treatment of the intermediate billet in a reducing atmosphere can reduce the oxide scale loss of the intermediate billet in ordinary heating furnaces and improve the yield of the intermediate billet.

[0080] The preparation method of the non-oriented silicon steel sheet provided in this embodiment, as well as the provided non-oriented silicon steel sheet, have been described in detail above. Three specific embodiments based on this embodiment are provided below. Specifically, the implementation process of these embodiments is as follows:

[0081] (1) Molten steel is cast into a continuous casting billet with a thickness of 220mm through a continuous casting equipment;

[0082] (2) After leaving the continuous casting equipment, the continuously cast billet is heated in a heating furnace. The soaking temperature and the time in the furnace are shown in Table 1.

[0083] (3) After the continuous casting billet leaves the heating furnace, it is rolled in multiple passes to produce an intermediate billet with a thickness of 110 mm. The reduction rate of each rolling pass is 20-22%, and the exit temperature of the last rolling pass is shown in Table 1.

[0084] (4) The intermediate billet is put into the tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. The holding temperature and holding time are shown in Table 1.

[0085] [Table 1]

[0086]

[0087] (5) The intermediate billet processed in the tunnel furnace is hot rolled and coiled to obtain hot rolled coil. The thickness H1, final rolling temperature and coiling temperature of the hot rolled plate are shown in Table 2.

[0088] (6) The hot-rolled coil obtained from the hot-rolled finishing process is directly shot-blasted and pickled to remove the surface oxide scale; the hot-rolled coil after pickling is cold-rolled on a single-stand cold rolling mill to produce cold-rolled coils. The thickness H2 of the cold-rolled coils is shown in Table 2.

[0089] (7) The cold-rolled coil is annealed in a continuous annealing furnace to obtain annealed strip steel. During the annealing process, the heating rate and the homogenization temperature are shown in Table 2. The cooling rate is 10℃ / s. The protective atmosphere is 20% H2 + 80% N2 with a dew point of 15℃. The unit tension is shown in Table 2.

[0090] [Table 2]

[0091]

[0092] (8) Coat each surface of the annealed strip with an insulating coating of 0.8 μm thickness. Thus, the non-oriented silicon steel product is obtained.

[0093] The chemical composition of one of the non-oriented silicon steel products obtained in each embodiment is shown in Table 3. Apart from the elements shown in Table 3, the remaining chemical components are Fe and unavoidable inclusions. Furthermore, the thickness, iron loss and magnetic induction intensity of the non-oriented silicon steel product are shown in Table 4.

[0094] [Table 3]

[0095]

[0096] [Table 4]

[0097] Serial Number Thickness, mm <![CDATA[Iron loss P 1.5 / 50 , W / kg]]> <![CDATA[Iron loss P 1.0 / 400 , W / kg,]]> <![CDATA[Magnetic induction intensity B 5000 , T]]> 1 0.30 2.34 14.31 1.662 2 0.25 2.01 11.83 1.667 3 0.20 2.28 10.57 1.673

[0098] <Second Implementation Method>

[0099] This embodiment provides a method for preparing a non-oriented silicon steel sheet, and a non-oriented silicon steel sheet obtained by the method.

[0100] In this embodiment, the preparation method includes sequentially performing the following processes: slab continuous casting, slab heating, rough rolling, intermediate slab heat treatment, intermediate slab assembly, hot rolling, pickling, cold rolling, coiling, annealing, and coating, thereby preparing a non-oriented silicon steel finished product.

[0101] Slab continuous casting process

[0102] Molten steel is poured into a continuous casting billet using a continuous casting equipment. The thickness of the billet is 200–250 mm, preferably 220 mm.

[0103] The chemical composition of the continuously cast billet meets the requirements for non-oriented silicon steel, and can be implemented using the chemical composition of existing known non-oriented silicon steel.

[0104] In a preferred embodiment, the chemical composition of the continuously cast billet, by mass percentage, is: C ≤ 0.0025%, S ≤ 0.0015%, Si: 2.50–3.40%, Al: 0.30–1.00%, Mn: 0.20–0.80%, P: 0.02–0.04%, Nb ≤ 0.004%, V ≤ 0.004%, Ti ≤ 0.004%, Ni ≤ 0.03%, Cr ≤ 0.03%, Cu ≤ 0.03%, N ≤ 0.002%, with the remainder being Fe and unavoidable inclusions. Based on this chemical composition, high-grade non-oriented silicon steel can be produced. On the one hand, compared to the chemical composition of existing known non-oriented silicon steel, this chemical composition can significantly improve the magnetic properties of the final non-oriented silicon steel product.

[0105] [Slab heating process]

[0106] After leaving the continuous casting equipment, the continuously cast billet is heated in a heating furnace, with a soaking temperature of T1 = T 10 ±10℃, furnace time 180~200min. Among them, T 10 =1100℃ - 30 × [Si] - 20 × [Al], where [Si] and [Al] are 100 times the mass percentage of Si and Al in the continuously cast billet. For example, if the mass percentage of Si in the continuously cast billet is 2.5%, then the value of [Si] in the formula is 2.5. In this way, by adopting this soaking temperature, the surface quality of the continuously cast billet can be guaranteed and excellent microstructure can be obtained in subsequent billet processing, thereby improving the performance of the final non-oriented silicon steel product.

[0107] Preferably, the continuously cast billet is directly heated in a heating furnace after leaving the continuous casting equipment. That is, the continuously cast billet is heated while still warm.

[0108] Rough rolling process

[0109] After leaving the heating furnace, the continuously cast billet is rolled in multiple passes to produce an intermediate billet. The thickness of the intermediate billet is 100–125 mm, preferably 110 mm.

[0110] In a further optimized configuration, the reduction rate per rolling pass is 20–22%, and the exit temperature of the final rolling pass is T2 = 900 ± 25℃. More preferably, T2 = T1 - 100℃. Such temperature and reduction rate control, combined with the aforementioned control of the soaking temperature, can further improve the billet opening effect and ensure the surface quality and microstructure of the intermediate billet.

[0111] Furthermore, in this billet-making process, it is preferable to use three rolling passes to produce intermediate billets.

[0112] Intermediate billet heat treatment process

[0113] The intermediate billet obtained from the billet-making process is placed in a tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere (90% H2 + 10% H2S), with a holding temperature of 1000–1050℃ and a holding time of 15–30 minutes. Thus, after billet-making, the intermediate billet is directly placed in the tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. This process effectively removes the surface oxide scale, improving the surface quality of the subsequent non-oriented silicon steel product and ensuring a higher yield. Compared to existing mechanical oxide scale removal methods, the intermediate billet in this application maintains a high temperature (e.g., holding temperature 1000–1050℃) throughout the intermediate billet heat treatment process without needing to be cooled to room temperature, thus avoiding surface cracks caused by intermediate billet cooling. On the other hand, it can improve the rolling structure after rough rolling, coarsen the grain size before finishing rolling, and reduce the hot rolling load; on the other hand, it can improve the uniformity and stability of the finishing rolling temperature, improve the structure after hot finishing rolling, reduce the normalizing heat treatment process after hot rolling, avoid the corrugated defects on the surface of high silicon steel after cold rolling, and further reduce production costs.

[0114] Intermediate billet assembly process

[0115] N intermediate billets are arranged into a stacked billet, and the four sides of the stacked billet are welded together to form a composite billet.

[0116] Where N ≥ 2, it means that the laminated billet is composed of at least two intermediate billets. Understandably, the N intermediate billets in this process are obtained through the preceding continuous casting, slab heating, billet preparation, and intermediate billet heat treatment. Furthermore, the chemical compositions of the N intermediate billets can be the same or different.

[0117] Preferably, the four sides of the laminated blank are arc welded. Of course, this application is not limited to this, and other welding techniques known in the art can also be used.

[0118] Furthermore, the composite blank is a cubic blank with parallel upper and lower surfaces and planar sides. Specifically, in one embodiment, N intermediate blanks of the same length and width are stacked together and then welded together at their joints, resulting in a cubic composite blank. In another embodiment, N intermediate blanks of different lengths and / or different widths are stacked together and then the differing sides are filled with sealant or solder to make the resulting composite blank cubic. Of course, these are just some examples, and this application is not limited thereto.

[0119] Preferably, a high-temperature resistant insulating coating is applied to the upper and lower surfaces of the intermediate billet after the intermediate billet heat treatment process, and then the two intermediate billets are stacked. Alternatively, at least one of the surfaces of two adjacent intermediate billets to be in contact can be coated with a high-temperature resistant insulating coating before stacking the two intermediate billets.

[0120] Here, the surface to be contacted refers to the surface of an intermediate blank that faces and is in contact with another intermediate blank in a stacked blank. For example, if an intermediate blank A and an intermediate blank B are stacked adjacent to each other, and the lower surface P1 of intermediate blank A is in contact with / fitted to the upper surface P2 of intermediate blank B, then the lower surface P1 constitutes the surface to be contacted of intermediate blank A, and the upper surface P2 constitutes the surface to be contacted of intermediate blank B.

[0121] When applying the high-temperature resistant insulating coating, it is possible to apply the high-temperature resistant insulating coating only to the lower surface P1 of intermediate blank A, or only to the upper surface P2 of intermediate blank B, or to apply the high-temperature resistant insulating coating to both the lower surface P1 of intermediate blank A and the upper surface P2 of intermediate blank B. In all three ways, the two adjacent intermediate blanks A and B in the stacked blanks can be separated by the high-temperature resistant insulating coating.

[0122] Preferably, the high-temperature resistant insulating coating contains MgO, and mainly uses high-temperature resistant coating MgO.

[0123] Hot rolling finishing process

[0124] The composite blank is heated in a heating furnace at a temperature of 1090–1130℃ for 180–200 min.

[0125] After the composite billet exits the heating furnace, it is hot-rolled to produce a composite hot-rolled plate with a thickness of 2.20 to 2.80 mm. The composite hot-rolled plate is then rolled into a composite hot-rolled coil.

[0126] Thus, in this embodiment, the composite billet is hot-rolled, and the prepared composite hot-rolled plate only needs to meet the thickness requirement of 2.20 to 2.80 mm. This ensures that a non-oriented silicon steel product with a thickness similar to or even thinner than that of conventional technology can be obtained with a small cold rolling reduction. This not only improves the magnetic properties of non-oriented silicon steel based on the thinner thickness (e.g., thinner thickness results in lower iron loss), but also improves the magnetic induction intensity and reduces iron loss based on the lower cold rolling reduction. Furthermore, it avoids the difficulties of hot rolling, hot rolling temperature and plate shape, and low-load rolling (i.e., there is no need to excessively hot roll in pursuit of ultra-thinness, which would cause a significant increase in rolling difficulty, plate shape deterioration, or even microstructure deterioration).

[0127] In addition, when hot rolling is performed in the form of composite billets, the surfaces of the two adjacent intermediate billets are not exposed to the external environment, so it is not easy to generate surface oxide scale, which can improve the surface quality of the final non-oriented silicon steel product and reduce the steel loss rate.

[0128] The final rolling temperature for hot rolling is 880–900℃, and the coiling temperature is 700–720℃. This can further improve the microstructure, surface quality, and sheet shape of the non-oriented silicon steel product, and improve its performance, especially its magnetic properties.

[0129] Furthermore, after the composite billet exits the heating furnace, it undergoes two-stage hot rolling: roughing and finishing, with finishing preferably using 7 passes.

[0130] Pickling process

[0131] The hot-rolled coils obtained from the hot-rolling finishing process are directly shot-blasted and pickled to remove the surface oxide scale.

[0132] Thus, in this embodiment, pickling is performed on composite hot-rolled coils (i.e., before the coils are separated during pickling), which reduces the surface area that needs to be pickled and decreases the possibility of environmental pollution caused by pickling.

[0133] Cold rolling process

[0134] After pickling, the composite hot-rolled coil is cold-rolled on a single-stand cold rolling mill to produce composite cold-rolled coil.

[0135] Among them, a 20-roll single-stand cold rolling mill is preferred for single-stand cold rolling mill.

[0136] Thus, as can be seen from the foregoing, this application only requires one cold rolling operation, and with a low cold rolling reduction, to obtain a non-oriented silicon steel product with a thickness comparable to or even thinner than that of conventional technologies. In other words, even with a smaller cold rolling reduction than conventional technologies, a thinner non-oriented silicon steel product can be obtained.

[0137] For example, in one embodiment, the cold rolling reduction rate is 73-86%, and the thickness of the composite cold-rolled coil is 0.30-0.60 mm.

[0138] [Roll Separation Process]

[0139] The composite cold-rolled coil obtained in the cold rolling process is divided into N single-layer cold-rolled coils by a slitting machine. The N single-layer cold-rolled coils correspond to the N intermediate billets that preceded them, that is, each intermediate billet is converted into a corresponding single-layer cold-rolled coil.

[0140] In one embodiment, the N intermediate billets have the same thickness, and correspondingly, the N single-layer cold-rolled coils have the same thickness. The thickness of each single-layer cold-rolled coil is one-Nth of the thickness of the composite cold-rolled coil, for example, N is 2. This coiling process yields two single-layer cold-rolled coils, and the thickness of each single-layer cold-rolled coil is half the thickness of the composite cold-rolled coil (for example, the thickness of the composite cold-rolled coil is 0.30-0.60 mm, and the thickness of the single-layer cold-rolled coil is 0.15-0.30 mm). Of course, in a variation embodiment, the thickness of the N intermediate billets may be partially or completely different, and correspondingly, the thickness of the N single-layer cold-rolled coils may be partially or completely different. In this way, non-oriented finished products with different thicknesses can be prepared simultaneously (for example, the thickness of the composite cold-rolled coil is 0.30 mm, N=2, one single-layer cold-rolled coil has a thickness of 0.25 mm, and the other single-layer cold-rolled coil has a thickness of 0.05 mm).

[0141] Annealing process

[0142] Single-layer cold-rolled coils are annealed in a continuous annealing furnace to obtain annealed strip steel.

[0143] During the annealing process, the heating rate is 30–50℃ / s, the soaking temperature is 980–1020℃, the cooling rate is 10–15℃ / s, the protective atmosphere is 20% H2 + 80% N2, the dew point is 10–20℃, and the unit tension is 2–3 N / mm. 2 .

[0144] Coating process

[0145] An insulating coating with a thickness of 0.5 to 0.8 μm is applied to each surface of the annealed strip steel, thus obtaining the finished non-oriented silicon steel product.

[0146] Understandably, the thickness of the resulting non-oriented silicon steel product is the sum of the thickness of the corresponding single-layer cold-rolled coil and the thicknesses of the upper and lower surface insulating coatings of the corresponding annealed strip. For example, for a single-layer cold-rolled coil with a thickness of 0.15 mm, the thickness of both the upper and lower surface insulating coatings of the corresponding annealed strip is 0.5 μm. Therefore, the thickness of the corresponding non-oriented silicon steel product is 0.15 mm + 0.5 μm + 0.5 μm = 0.1510 mm. However, in this application, the coating thickness is very small relative to the thickness of the cold-rolled coil, and the thickness of the non-oriented silicon steel product is basically the same as the thickness of the cold-rolled coil. Therefore, the thickness of the cold-rolled coil is taken as the thickness of the non-oriented silicon steel product.

[0147] Furthermore, the non-oriented silicon steel sheet provided in this embodiment is prepared using the aforementioned preparation method. Even with the same chemical composition and thickness as conventional technologies, its magnetic properties are significantly improved compared to conventional technologies, and it is easier and cheaper to produce.

[0148] The thickness of the non-oriented silicon steel sheet is 0.15–0.30 mm, and the iron loss P 1.5 / 50 ≤2.35W / kg, P 1.0 / 400 ≤14.5W / kg, magnetic induction intensity B 5000 ≥1.66T.

[0149] Regarding the chemical composition, the non-oriented silicon steel sheet, by mass percentage, contains: C ≤ 0.0025%, S ≤ 0.0015%, Si: 2.50–3.40%, Al: 0.30–1.00%, Mn: 0.20–0.80%, P: 0.02–0.04%, Nb ≤ 0.004%, V ≤ 0.004%, Ti ≤ 0.004%, Ni ≤ 0.03%, Cr ≤ 0.03%, Cu ≤ 0.03%, N ≤ 0.002%, with the remainder being Fe and unavoidable inclusions. Based on this chemical composition, the non-oriented silicon steel sheet is a high-grade non-oriented silicon steel with excellent magnetic properties.

[0150] Compared with the prior art, the beneficial effects of this embodiment are at least as follows:

[0151] 1) After billet preparation, the intermediate billet is directly fed into a tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. This process can remove the surface oxide scale, which is beneficial to the surface quality of the subsequent non-oriented silicon steel products and ensures the yield. Compared with existing flame cleaning methods, the intermediate billet in this application is kept at a high temperature (e.g., holding temperature 950-1000℃) during the intermediate billet heat treatment process without having to be cooled to room temperature. This avoids the formation of surface cracks due to the cooling of the intermediate billet and further improves the surface quality of the non-oriented silicon steel products. Furthermore, the high temperature can improve the microstructure of the intermediate billet, which is beneficial to further improve the magnetic properties of the final non-oriented silicon steel. The normalizing process can be omitted to obtain excellent magnetic properties, thereby shortening the process flow and reducing production costs.

[0152] 2) Compared to the conventional technology of directly hot-rolling an intermediate billet into a hot-rolled coil, this embodiment combines N intermediate billets into a composite billet, and then hot-rolls the composite billet in the hot-rolling finishing process to obtain a composite hot-rolled coil with N single-layer hot-rolled coils. When the thickness of the composite hot-rolled coil is the same as that of the hot-rolled coil in the conventional technology (for example, the same thickness of 2.20 mm), it not only ensures the hot-rolling temperature and shape, low load and low rolling difficulty (that is, there is no need to excessively hot-roll in pursuit of ultra-thinness, which would cause a significant increase in rolling difficulty, deterioration of shape, or even deterioration of microstructure), but also the thickness of the single-layer hot-rolled coil rolled from each intermediate billet is much smaller than that of the hot-rolled coil in the conventional technology. As a result, the cold rolling reduction in the subsequent cold rolling process is lower than that of the conventional technology, resulting in a thinner single-layer cold-rolled coil than the conventional technology.

[0153] 3) Building upon point 2) above, not only can the magnetic properties of non-oriented silicon steel be improved due to its thinner thickness (e.g., thinner thickness results in lower iron loss), but also the cold rolling reduction is lower, which ensures that the {111} texture, which is detrimental to magnetic properties, is weakened, while the {100} and {110} textures, which are beneficial to magnetization, are strengthened. This avoids a decrease in magnetic induction intensity due to cold rolling, thus improving magnetic induction intensity compared to existing conventional technologies. Furthermore, the lower cold rolling reduction results in less cold rolling deformation storage, making it easier for grains to grow during annealing, thereby reducing iron loss compared to existing conventional technologies.

[0154] 4) In addition, by precisely controlling the temperature and time in the slab heating process, as well as the temperature in the heating process and the hot rolling and finishing process, the microstructure, surface quality and plate shape of the non-oriented silicon steel product can be further improved, thereby improving the performance of the non-oriented silicon steel product, especially its magnetic properties.

[0155] 5) Furthermore, the overall process flow of the present invention is simple. Compared with existing conventional technologies, there are no additional high-cost and high-difficulty processes. In fact, compared with existing conventional technologies, it can greatly reduce the difficulty of hot rolling and cold rolling. Overall, it has the advantages of low production cost, low production difficulty, and stronger quality stability, which is conducive to industrial implementation and has huge economic benefits.

[0156] The preparation method of the non-oriented silicon steel sheet provided in this embodiment, as well as the provided non-oriented silicon steel sheet, have been described in detail above. Three specific embodiments based on this embodiment are provided below. Specifically, the implementation process of these embodiments is as follows:

[0157] (1) Molten steel is cast into a continuous casting billet with a thickness of 200mm using a continuous casting equipment;

[0158] (2) After leaving the continuous casting equipment, the continuously cast billet is heated in a heating furnace. The soaking temperature and the time in the furnace are shown in Table 5.

[0159] (3) After the continuous casting billet leaves the heating furnace, it is rolled in multiple passes to produce an intermediate billet with a thickness of 110 mm. The reduction rate of each rolling pass is 20-22%, and the exit temperature of the last rolling pass is shown in Table 5.

[0160] (4) The intermediate billet is placed in a tunnel furnace and subjected to high-temperature reduction heat treatment in a reducing atmosphere. The holding temperature and holding time are shown in Table 5. Then, a high-temperature resistant insulating coating is applied to the surface of the two intermediate billets. The two intermediate billets are then arranged into a stacked billet. The four sides of the stacked billet are then welded to form a composite billet.

[0161] (5) The composite billet is heated in a heating furnace. The heating temperature and heating time are shown in Table 5.

[0162] [Table 5]

[0163]

[0164]

[0165] (6) After the composite billet leaves the heating furnace, it is hot rolled to produce a composite hot-rolled plate. Then the composite hot-rolled plate is rolled into a composite hot-rolled coil. The thickness H1, final rolling temperature and coiling temperature of the composite hot-rolled plate are shown in Table 6.

[0166] (7) The composite hot-rolled coil is shot-blasted and pickled to remove the surface oxide scale;

[0167] (8) The composite hot-rolled coil after pickling is cold-rolled on a single-stand cold rolling mill to produce composite cold-rolled coil. The thickness H2 of the composite cold-rolled coil is shown in Table 6.

[0168] (9) The composite cold-rolled coil obtained in the cold rolling process is divided into two single-layer cold-rolled coils by a slitting machine;

[0169] (10) The single-layer cold-rolled coil is annealed in a continuous annealing furnace to obtain annealed strip steel. During the annealing process, the heating rate and the homogenization temperature are shown in Table 6. The cooling rate is 10℃ / s. The protective atmosphere is 20% H2 + 80% N2 with a dew point of 15℃. The unit tension is shown in Table 6.

[0170] [Table 6]

[0171]

[0172] (11) Apply an insulating coating with a thickness of 0.8 μm to each surface of the annealed strip steel to obtain the finished non-oriented silicon steel product.

[0173] The chemical composition of one of the non-oriented silicon steel products obtained in each embodiment is shown in Table 7. Apart from the elements shown in Table 7, the remaining chemical components are Fe and unavoidable inclusions. Furthermore, the thickness, iron loss and magnetic induction intensity of the non-oriented silicon steel product are shown in Table 8.

[0174] [Table 7]

[0175]

[0176] [Table 8]

[0177] Serial Number Thickness, mm <![CDATA[Iron loss P 1.5 / 50 , W / kg]]> <![CDATA[Iron loss P 1.0 / 400 , W / kg,]]> <![CDATA[Magnetic induction intensity B 5000 , T]]> 4 0.30 2.30 13.82 1.683 5 0.25 2.09 11.64 1.668 6 0.15 1.93 10.16 1.663

[0178] <Third Implementation Method>

[0179] This embodiment provides a method for preparing a non-oriented silicon steel sheet, and a non-oriented silicon steel sheet obtained by the method.

[0180] In this embodiment, the preparation method includes the following sequential processes: continuous casting, slab heating, billet preparation, intermediate billet heat treatment, billet assembly, hot rolling, coiling, pickling, cold rolling, annealing, and coating, thereby producing a non-oriented silicon steel finished product. These processes are described in detail below.

[0181] First, the steps of this embodiment—[slab continuous casting process], [slab heating process], [rough rolling and billet opening process], [intermediate billet heat treatment process], [bill assembly process], and [hot rolling and finishing process]—are the same as those in the second embodiment above, and will not be repeated here. Next, the remaining steps of this embodiment will be introduced.

[0182] [Roll Separation Process]

[0183] The composite hot-rolled coil obtained in the hot-rolling finishing process is divided into N single-layer hot-rolled coils by a slitting machine. The N single-layer hot-rolled coils correspond to the N intermediate billets that preceded them, that is, each intermediate billet is converted into a corresponding single-layer hot-rolled coil.

[0184] In one embodiment, the N intermediate billets have the same thickness, and correspondingly, the N single-layer hot-rolled coils have the same thickness. The thickness of each single-layer hot-rolled coil is one-Nth of the thickness of the composite hot-rolled coil, for example, N is 2. This slitting process yields two single-layer hot-rolled coils, and the thickness of each single-layer hot-rolled coil is half the thickness of the composite hot-rolled coil (for example, the thickness of the composite hot-rolled coil is 2.20–2.80 mm, and correspondingly, the thickness of the single-layer hot-rolled coil is 1.10–1.40 mm). Of course, in a variation embodiment, the thicknesses of the N intermediate billets may be partially or completely different, and correspondingly, the thicknesses of the N single-layer hot-rolled coils may be partially or completely different.

[0185] Pickling process

[0186] The hot-rolled coils obtained from the hot-rolling finishing process are directly shot-blasted and pickled to remove the surface oxide scale.

[0187] Cold rolling process

[0188] After pickling, the single-layer hot-rolled coil is cold-rolled on a single-stand cold rolling mill to produce a single-layer cold-rolled coil.

[0189] Among them, a 20-roll single-stand cold rolling mill is preferred for single-stand cold rolling mill.

[0190] Thus, as can be seen from the foregoing, this application only requires one cold rolling operation, and with a low cold rolling reduction, to obtain a non-oriented silicon steel product with a thickness comparable to or even thinner than that of conventional technologies. In other words, even with a smaller cold rolling reduction than conventional technologies, a thinner non-oriented silicon steel product can be obtained.

[0191] For example, in one embodiment, the cold rolling reduction rate is 74-87%, and the thickness of the single-layer cold-rolled coil is 0.15-0.30 mm.

[0192] Annealing process

[0193] Single-layer cold-rolled coils are annealed in a continuous annealing furnace to obtain annealed strip steel.

[0194] During the annealing process, the heating rate is 30–50℃ / s, the soaking temperature is 980–1020℃, the cooling rate is 10–15℃ / s, the protective atmosphere is 20% H2 + 80% N2, the dew point is 10–20℃, and the unit tension is 2–3 N / mm. 2 .

[0195] Coating process

[0196] An insulating coating with a thickness of 0.5 to 0.8 μm is applied to each surface of the annealed strip steel, thus obtaining the finished non-oriented silicon steel product.

[0197] Understandably, the actual thickness of the resulting non-oriented silicon steel product is the sum of the thickness of the corresponding single-layer cold-rolled coil and the thicknesses of the upper and lower surface insulating coatings of the corresponding annealed strip. For example, for a single-layer cold-rolled coil with a thickness of 0.15 mm, the thicknesses of the upper and lower surface insulating coatings of the corresponding annealed strip are both 0.5 μm. Therefore, the actual thickness of the corresponding non-oriented silicon steel product is 0.15 mm + 0.5 μm + 0.5 μm = 0.1510 mm. However, in this application, the coating thickness is very small relative to the thickness of the cold-rolled coil, and the thickness of the non-oriented silicon steel product is basically the same as the thickness of the cold-rolled coil. Therefore, the thickness of the cold-rolled coil is taken as the thickness of the non-oriented silicon steel product.

[0198] The preparation method described in this embodiment has been detailed above. Next, this embodiment also provides a non-oriented silicon steel sheet, which is prepared using the aforementioned method. Even using the same chemical composition and thickness as conventional technologies, its magnetic properties are significantly improved compared to conventional technologies, while ensuring excellent surface quality, low production difficulty, and low production cost.

[0199] The thickness of the non-oriented silicon steel sheet is 0.15–0.30 mm, and the iron loss P 1.5 / 50 ≤2.30W / kg, P 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.64T.

[0200] Regarding the chemical composition, the non-oriented silicon steel sheet, by mass percentage, contains: C ≤ 0.0025%, S ≤ 0.0015%, Si: 2.50–3.40%, Al: 0.30–1.00%, Mn: 0.20–0.80%, P: 0.02–0.04%, Nb ≤ 0.004%, V ≤ 0.004%, Ti ≤ 0.004%, Ni ≤ 0.03%, Cr ≤ 0.03%, Cu ≤ 0.03%, N ≤ 0.002%, with the remainder being Fe and unavoidable inclusions. Based on this chemical composition, the non-oriented silicon steel sheet is a high-grade non-oriented silicon steel with excellent magnetic properties.

[0201] The preparation method of the non-oriented silicon steel sheet provided in this embodiment, as well as the provided non-oriented silicon steel sheet, have been described in detail above. Three specific embodiments based on this embodiment are provided below. Specifically, the implementation process of these embodiments is as follows:

[0202] (1) Molten steel is cast into a continuous casting billet with a thickness of 250mm using a continuous casting equipment;

[0203] (2) After leaving the continuous casting equipment, the continuously cast billet is heated in a heating furnace. The soaking temperature and the time in the furnace are shown in Table 9.

[0204] (3) After the continuous casting billet leaves the heating furnace, it is rolled in multiple passes to produce an intermediate billet with a thickness of 125 mm. The reduction rate of each rolling pass is 20-22%, and the exit temperature of the last rolling pass is shown in Table 9.

[0205] (4) The intermediate billet is placed in a tunnel furnace and subjected to high-temperature reduction heat treatment in a reducing atmosphere. The holding temperature and holding time are shown in Table 9. Then, a high-temperature resistant insulating coating is applied to the surface of the two intermediate billets. Then, the two intermediate billets are arranged into a stacked billet. Then, the four sides of the stacked billet are welded to form a composite billet.

[0206] (5) The composite billet is heated in a heating furnace. The heating temperature and heating time are shown in Table 9.

[0207] [Table 9]

[0208]

[0209] (6) After the composite billet leaves the heating furnace, it is hot rolled to produce a composite hot-rolled plate. Then the composite hot-rolled plate is rolled into a composite hot-rolled coil. The thickness H1, final rolling temperature and coiling temperature of the composite hot-rolled plate are shown in Table 10.

[0210] (7) The composite hot-rolled coil obtained in the hot rolling finishing process is divided into two single-layer hot-rolled coils by a slitting machine;

[0211] (8) The single-layer hot-rolled coil is shot-blasted and pickled to remove the surface oxide scale;

[0212] (9) The single-layer hot-rolled coil after pickling is cold-rolled on a single-stand cold rolling mill to produce a single-layer cold-rolled coil. The thickness H3 of the single-layer cold-rolled coil is shown in Table 10.

[0213] (10) The single-layer cold-rolled coil is annealed in a continuous annealing furnace to obtain annealed strip steel. During the annealing process, the heating rate and the homogenization temperature are shown in Table 10. The cooling rate is 10℃ / s. The protective atmosphere is 20% H2 + 80% N2 with a dew point of 15℃. The unit tension is shown in Table 10.

[0214] [Table 10]

[0215]

[0216] (11) Coat each surface of the annealed strip with an insulating coating as shown in Table 12. Thus, the non-oriented silicon steel product is obtained.

[0217] The chemical composition of one of the non-oriented silicon steel products obtained in each embodiment is shown in Table 11. Apart from the elements shown in Table 11, the remaining chemical components are Fe and unavoidable inclusions. Furthermore, the thickness, iron loss and magnetic induction intensity of the non-oriented silicon steel product are shown in Table 12.

[0218] [Table 11]

[0219]

[0220] [Table 12]

[0221] Serial Number Coating thickness, μm Thickness, mm <![CDATA[Iron loss P 1.5 / 50 , W / kg]]> <![CDATA[Iron loss P 1.0 / 400 , W / kg,]]> <![CDATA[Magnetic induction intensity B 5000 , T]]> 9 0.5 0.30 2.26 12.18 1.667 10 0.5 0.20 2.09 11.64 1.652 11 0.6 0.15 1.96 10.63 1.641

Claims

1. A method for preparing non-oriented silicon steel sheet, characterized in that, The method includes the processes of continuous casting, slab heating, billet preparation, intermediate billet heat treatment, billet assembly, hot rolling and finishing, pickling, cold rolling, annealing and coating, as well as a coiling process located before or after the cold rolling process, wherein, Slab heating process: After leaving the continuous casting equipment, the continuously cast slab is heated in a heating furnace, and the soaking temperature is T1=T 10 ±10℃, furnace time 180~200min, T 10 =1100℃-30×[Si]-20×[Al], where [Si] and [Al] are 100 times the mass percentages of Si and Al in the continuously cast billet; Billeting process: After the continuous casting billet leaves the heating furnace, it is rolled in multiple passes to make an intermediate billet; the reduction rate of each rolling pass is 20~22%, and the exit temperature of the last rolling pass is T2=900±25℃. Intermediate billet heat treatment process: The intermediate billet prepared in the billet-making process is put into a tunnel furnace for high-temperature reduction heat treatment in a reducing atmosphere. The holding temperature is 1000~1050℃ and the holding time is 15~30min. Assembly process: Apply high-temperature resistant insulating coating to the upper and lower surfaces of the intermediate billet, then arrange N intermediate billets into a stacked billet, and weld the four sides of the stacked billet to form a composite billet. Hot rolling and finishing process: The composite billet is heated in a heating furnace, and after exiting the heating furnace, it is subjected to rough rolling and finishing rolling; the final rolling temperature is 880~900℃, and the coiling temperature is 700~720℃; Annealing process: heating rate is 30~50℃ / s, soaking temperature is 980~1020℃, cooling rate is 10~15℃ / s, and the protective atmosphere is 20%H2+80%N2.

2. The method for preparing non-oriented silicon steel sheet according to claim 1, characterized in that, The chemical composition of the continuously cast billet, by mass percentage, is: C≤0.0025%, S≤0.0015%, Si:2.50~3.40%, Al:0.30~1.00%, Mn:0.20~0.80%, P:0.02~0.04%, Nb≤0.004%, V≤0.004%, Ti≤0.004%, Ni≤0.03%, Cr≤0.03%, Cu≤0.03%, N≤0.002%, with the remainder being Fe and unavoidable inclusions.

3. The method for preparing non-oriented silicon steel sheet according to claim 1, characterized in that, The preparation method does not include normalization treatment.

4. The method for preparing non-oriented silicon steel sheet according to claim 1, characterized in that, Annealing process: Dew point 10~20℃, unit tension 2~3N / mm 2 .

5. The method for preparing non-oriented silicon steel sheet according to claim 1, characterized in that, The thickness of the continuously cast billet is 200~250mm, and the thickness of the intermediate billet is 100~125mm; Hot rolling finishing process: to obtain hot-rolled coils with a thickness of 2.00~2.30mm or 2.20~2.80mm.

6. The method for preparing non-oriented silicon steel sheet according to claim 1, characterized in that, The slitting process involves dividing the composite hot-rolled coil or composite cold-rolled coil, which is transformed from the composite billet, into N single-layer hot-rolled coils or N single-layer cold-rolled coils using a slitting machine.

7. The method for preparing non-oriented silicon steel sheet according to claim 6, characterized in that, The hot rolling finishing process involves heating at a temperature of 1090~1130℃ for 180~200 minutes; after the composite billet exits the heating furnace, it is rolled to obtain a composite hot-rolled coil.

8. The method for preparing non-oriented silicon steel sheet according to claim 7, characterized in that, The slitting process is performed before the pickling process; The cold rolling process involves cold rolling a single-layer hot-rolled coil once on a single-stand cold rolling mill to produce a single-layer cold-rolled coil with a cold rolling reduction rate of 74-87% and a thickness of 0.15-0.30 mm.

9. The method for preparing non-oriented silicon steel sheet according to claim 7, characterized in that, The slitting process is located between the cold rolling process and the annealing process; The cold rolling process involves cold rolling the composite hot-rolled coil on a single-stand cold rolling mill to produce a composite cold-rolled coil. The cold rolling reduction rate is 73-86%, the thickness of the composite cold-rolled coil is 0.30-0.60 mm, and the thickness of the single-layer cold-rolled coil is 0.15-0.30 mm.

10. The method for preparing non-oriented silicon steel sheet according to claim 1, characterized in that, The thickness of the N intermediate blanks may be the same or different.

11. The method for preparing non-oriented silicon steel sheet according to claim 1, characterized in that, The reducing atmosphere is 90% H2 + 10% H2S.

12. A non-oriented silicon steel sheet, characterized in that, It is prepared by the preparation method described in claim 1.

13. The non-oriented silicon steel sheet according to claim 12, characterized in that, The thickness of the non-oriented silicon steel sheet is 0.2~0.3mm, and the iron loss P 1.5 / 50 ≤2.35W / kg, P 1.0 / 400 ≤14.5W / kg, magnetic induction intensity B 5000 ≥1.66T.

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