A method for improving the cold rolling processability of high silicon non-oriented silicon steel

Abstract

A method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel, belonging to the field of non-oriented silicon steel manufacturing technology, includes the following steps: A continuously cast billet with a silicon content of not less than 3.2% and a thickness of 70–240 mm is heated and held in a furnace. After exiting the furnace, the surface iron oxide scale is removed using high-pressure water, followed by rough rolling to obtain an intermediate billet. After removing the surface iron oxide scale again using high-pressure water, the billet is finished rolled to obtain a hot-rolled plate. The hot-rolled plate is then cooled by laminar water and coiled to obtain a hot-rolled coil. The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The soaking time t satisfies t = 15 + (690 - T) × (0.3–0.5) h, and the furnace atmosphere is hydrogen. After cooling to room temperature, the coil is removed from the bell-type annealing furnace to obtain a hot-rolled annealed coil. After uncoiling, the hot-rolled annealed coil is sequentially pickled and cold-rolled in a pickling and cold rolling mill to obtain a cold-rolled steel plate with a thickness of 0.20–0.50 mm.

Description

Technical Field

[0001] This invention belongs to the field of non-oriented silicon steel manufacturing technology, specifically relating to a method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel. Background Technology

[0002] High-silicon non-oriented silicon steel is mainly used in large generators, high-efficiency electric motors and compressors, and drive motors for new energy vehicles. Its manufacturing process generally includes steelmaking, continuous casting, hot rolling, normalizing, pickling, cold rolling, annealing, and coating with an insulating layer. It has stringent magnetic property requirements and is technically challenging to manufacture. In particular, when the silicon mass percentage in electrical steel exceeds 3.2%, the resistance to cold rolling deformation is very high. Therefore, normalizing the hot-rolled sheet before cold rolling is necessary to promote recrystallization of the hot-rolled deformed structure and reduce deformation resistance. Furthermore, high-silicon non-oriented electrical steel hot-rolled sheets contain fibrous, elongated deformed grains. Normalizing the hot-rolled sheet promotes the recrystallization of these deformed grains, helping to prevent "corrugation" defects in the final product. However, normalizing the hot-rolled sheet results in coarser recrystallized grains, which can cause severe edge cracking or even strip breakage during cold rolling, requiring edge trimming, which not only reduces the yield but also increases production difficulty. Furthermore, in the production of high-silicon non-oriented silicon steel, edge cracking during cold rolling has become the biggest bottleneck in the cold rolling process. Multiple edge cracks exist on the end face of the steel coil, with crack depths exceeding 5mm and lengths exceeding 10mm, resulting in low mill speeds and severely restricting output and rolling stability. Therefore, mitigating edge cracking during cold rolling has become a crucial and urgent problem to be solved in the manufacture of high-silicon non-oriented electrical steel.

[0003] Patent CN110565022B discloses a method for manufacturing high-grade non-oriented electrical steel. The weight percentage composition of the steel is as follows: Si: 2.9–3.5%, Mn: 0.15–1.0%, Al: 0.5–1.5%, C ≤ 0.0040%, S ≤ 0.0060%, Ti ≤ 0.0030%, N ≤ 0.0040%, with the total content of impurities V, Nb, B, Ca, Mo, and Ni controlled below 0.02%, and the remainder being Fe and unavoidable impurities. The slab is rolled into a hot-rolled plate with a thickness of 2.0–3.0 mm, then normalized at 900–1050 °C before rolling. During rolling, edge cracks are removed, and the strip edges are trimmed online by 2–10 mm. At this point, the strip temperature is above 100 °C. Trimming is performed simultaneously with rolling without stopping the mill. This operation avoids the need for pre-rolling preparation to remove edge cracks, reducing the shear stress from cold cutting. The final finished product thickness is 0.5 mm. This method reduces the risk of strip breakage caused by cold-rolled edge cracks through online trimming, but it increases production difficulty, reduces production efficiency, and significantly lowers the yield.

[0004] Patent CN105396879A discloses a method for controlling edge cracking in the cold continuous rolling of high-grade non-oriented silicon steel. This technology requires reducing the load distribution on the first stand from 33%–36% under automatic system allocation to 25%–30%, which reduces edge cracking at the first stand exit. Setting the work roll shift value of the UCMW mill to -40–20mm effectively reduces edge stress in the strip, preventing edge cracking in high-grade non-oriented silicon steel during cold continuous rolling, thus improving the production capacity of high-grade non-oriented silicon steel and ensuring its quality. This technology reduces edge stress by optimizing cold rolling mill parameter settings to avoid edge cracking during cold continuous rolling.

[0005] Patent CN114369761A discloses a thin-gauge non-oriented silicon steel and its preparation method. Its composition by weight percentage is: C≤0.005%, Si: 2.0~4.0%, Mn: 0.20~2.0%, P≤0.02%, S≤0.005%, Al: 0.3~1.4%, N≤0.005%, Ti≤0.005%, Nb≤0.005%, and (Si+1.3Al) / Mn≥2.1%, 3.0%≤Si+Mn≤4.4%, with the remainder being iron and unavoidable impurities. After continuous casting, it undergoes rough rolling at 900~1150℃ and finish rolling at 800~950℃ to obtain a 2mm thick hot-rolled plate. After normalizing at 760~840℃, edge trimming, and one-step cold rolling to 0.2mm using a 20-roll mill, it undergoes final annealing at 830~880℃ to obtain the finished product. This method prevents large-scale edge cracks by controlling the reduction rate of the first cold rolling pass to be less than 18% and the reduction rate of the last cold rolling pass to be less than 20%. However, this method requires edge trimming of the normalized steel sheet and imposes strict requirements on the cold rolling reduction schedule and amount, which is detrimental to maximizing the mill's production capacity and improving production efficiency. Furthermore, it can only prevent large-scale edge cracks and cannot suppress the formation of medium and small cracks.

[0006] Patent CN116213458A discloses a method for improving the edge quality of high-grade non-oriented silicon steel used in cold continuous rolling for new energy vehicle drive motors. The method includes: controlling the pickling time t of the hot-rolled raw material to be: T×Si% / 600≤t≤T×Si% / 300; setting the intermediate roll shifting amount of the continuous rolling mill to 30~80mm; and controlling the ratio L / R of the work roll body length L to the work roll surface curvature radius R within the range of -0.25≤L / R≤-0.15. By optimizing the pickling time of the hot-rolled coil, adopting reasonable work roll profile dimensions, and adjusting the intermediate roll shifting amount, the method maximizes the reduction of edge waviness while suppressing edge cracking in cold continuous rolling. This improves the edge quality of high-grade non-oriented silicon steel used in cold continuous rolling for new energy vehicle drive motors without edge trimming of the hot-rolled raw material, achieving efficient production, reducing edge trimming loss after cold rolling, and increasing the yield.

[0007] Patent CN116411152A discloses a normalizing method for non-oriented electrical steel. Specifically, for non-oriented silicon steel with the following composition range: C ≤ 0.004%, Si: 2.2–4.0%, Mn: 0.1–1.2%, Al: 0.1–1.2%, S ≤ 0.01%, Ti ≤ 0.005%, Nb ≤ 0.005%, the normalizing process is as follows: A hot-rolled sheet is heated to a target temperature; a hot-rolled sheet of non-oriented electrical steel with a set chemical composition is heated to reach the target temperature; under the conditions of the target temperature and a first set time, the heated hot-rolled sheet is homogenized; and then, for a second set time… Under these conditions, the hot-rolled sheet after homogenization is subjected to self-homogenization and then cooled to obtain a normalized substrate. The normalization temperature and time are calculated based on the composition, specifically: target temperature = 1133 - 66.67 × [Si] + 66.67 × [Mn] - 33.33 × [Al], first set time = -44.18 + 25.45 × [Si] + 15.00 × [Mn] + 11.36 × [Al], second set time = 188.18 - 25.45 × [Si] - 15.00 × [Mn] - 11.36 × [Al]. Because the target temperature of the normalization process in this technology is still relatively high, the equiaxed grain size obtained after normalization is still relatively coarse. This is detrimental to the improvement of the steel sheet's toughness and plasticity, and cannot completely avoid the risk of edge cracking or strip breakage during cold rolling.

[0008] In summary, due to the high silicon content of high-silicon non-oriented silicon steel, its deformation resistance during cold rolling is very high, necessitating normalizing treatment of the hot-rolled sheet before cold rolling. However, normalized sheets often contain coarse equiaxed grains, resulting in poor toughness and plasticity. This often leads to severe edge cracking or even strip breakage during cold rolling, causing problems such as edge trimming and reduced yield. As the aforementioned patented technology shows, to mitigate edge cracking, existing methods require strict control over the normalizing process, edge trimming, pass reduction distribution, pickling process, and roll configuration, making the production process complex and difficult to control. Furthermore, the presence of some coarse equiaxed recrystallized grains in the normalized sheet hinders further improvement in toughness and plasticity. Therefore, it is necessary to effectively control the grain structure of the steel sheet before cold rolling and, based on this, develop a new method to improve the cold rolling performance of high-silicon non-oriented silicon steel. Summary of the Invention

[0009] To address the problem of severe edge cracking during the cold rolling process of high-silicon non-oriented silicon steel, this invention provides a method to improve the cold rolling processing performance of high-silicon non-oriented silicon steel. By combining hot rolling technology with bell-type annealing technology to control the microstructure of hot rolling and annealing, a gradient microstructure is ultimately obtained in the hot-rolled and annealed plate, consisting of fine equiaxed crystals on the surface of the steel plate and flat recrystallized grains inside the steel plate. This gradient microstructure can effectively prevent crack nucleation and propagation, thereby significantly improving the cold rolling plasticity and toughness of high-silicon non-oriented silicon steel and avoiding edge cracking during the cold rolling process.

[0010] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0011] (1) Heat the continuous casting billet with a silicon mass percentage of not less than 3.2% and a thickness of 70-240 mm to 1060-1100℃, hold it in the furnace for 90-180 min, remove the surface iron oxide scale with high pressure water after taking it out of the furnace, and then perform rough rolling. The initial rolling temperature is 1020-1070℃ and the final rolling temperature is 930-980℃ to obtain an intermediate billet with a thickness of 20-30 mm.

[0012] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 890-940℃ and a final rolling temperature of 790-840℃ to obtain a hot-rolled plate with a thickness of 2.4-2.8mm. The hot-rolled plate is then cooled to 500-570℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0013] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 20-35℃ / h, the temperature T in the soaking section is 620-690℃, the soaking time t satisfies t=15+(690-T)×(0.3-0.5)h, the cooling rate in the cooling section is 15-40℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0014] (4) After the hot-rolled annealed coil is uncoiled, it is pickled and cold-rolled in the pickling and cold rolling mill to obtain a cold-rolled steel plate with a thickness of 0.20 to 0.50 mm.

[0015] In step (1), the chemical composition of the continuously cast billet by weight percentage is: Si: 3.2-4.1%, Mn: 0.20-0.55%, Al: 0.2-1.5%, C≤0.0027%, S≤0.0025%, N≤0.0020%, O≤0.0010%, Sn or Sb or Sn+Sb≤0.15%, with the balance being Fe and unavoidable impurities.

[0016] In step (2), the surface of the hot-rolled coil is composed of fine equiaxed grains with an average grain size of 10-25 μm, while the interior of the steel plate is composed of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 5-18% of the entire thickness range of the steel plate.

[0017] In step (3), the surface layer of the hot-rolled annealed steel coil obtained has equiaxed grains with an average grain size of 30-50 μm.

[0018] In step (3), the steel plate obtained by hot rolling annealing has flat recrystallized grains inside, with an average width of 35-75 μm and an average aspect ratio of 2-6.

[0019] In step (3), the equiaxed grain region on the surface of the hot-rolled annealed steel coil accounts for 20-55% of the entire steel plate thickness range.

[0020] In step (4), the pickling solution is a hydrochloric acid aqueous solution with a mass concentration of 1-2%, and the pickling temperature is 50-85℃.

[0021] In step (4), the pickled plate needs to be preheated to 70-100°C before the first cold rolling pass.

[0022] The control principle of the process parameters of each process in this invention is as follows:

[0023] (1) The mass percentage of silicon in steel is 3.2% to 4.1%. If the silicon content is higher than 4.1%, the toughness and plasticity of the steel deteriorate sharply, and strip breakage will occur during cold rolling; if the silicon content is lower than 3.2%, the toughness and plasticity of the steel are good, and it is not necessary to improve the cold rolling performance through this technology. If the mass percentage of aluminum is higher than 1.5%, it is easy to clog the nozzle, making continuous casting production impossible. Carbon, sulfur, oxygen, and nitrogen are harmful impurities that impair magnetic properties and easily form non-magnetic compounds such as cementite, manganese sulfide, alumina, and aluminum nitride, so their content should be strictly controlled. Sn and Sb elements help improve the magnetic properties of steel; however, if the mass percentage of Sn or Sb or Sn+Sb exceeds 0.15%, gray stripe defects will appear on the surface of the steel plate.

[0024] (2) The purpose of heating to 1060–1100℃ and holding in the furnace for 90–180 min is to ensure uniform billet temperature and reduce the billet's resistance to hot rolling deformation. If the heating temperature is too high and the holding time is too long, on the one hand, the grains will coarsen significantly, leading to edge crease defects in hot rolling; on the other hand, severe surface oxidation will increase the difficulty of removing iron oxide scale. If the heating temperature is too low and the holding time is too short, the billet temperature will be uneven, leading to increased difficulty in controlling hot rolling thickness and shape.

[0025] (3) The purpose of rough rolling start temperature of 1020~1070℃, finish rolling temperature of 930~980℃, and intermediate billet thickness of 20~30mm is to ensure the subsequent finishing rolling temperature and reduce the finishing rolling reduction load.

[0026] (4) The finishing rolling temperature is 890-940℃, the final rolling temperature is 790-840℃, and laminar cooling is performed after hot rolling, with the coiling temperature set at 500-570℃. The purpose is to: utilize the lower temperature of hot rolling to promote shear deformation of the surface layer of the hot-rolled plate, thereby inducing dynamic recrystallization, resulting in more fine equiaxed recrystallized grains on the surface of the steel plate; at the same time, to prevent the formation of coarse equiaxed grains inside the hot-rolled plate due to dynamic recrystallization, ensuring that a large number of fibrous elongated deformed grains are obtained inside the steel plate; and to use a lower coiling temperature to prevent the growth of equiaxed grains on the surface of the hot-rolled plate, and to prevent the formation of coarse equiaxed grains inside the hot-rolled plate due to static recrystallization. Through the coordinated control of the finishing rolling temperature, the final rolling temperature, and the coiling temperature, it is ensured that the hot-rolled plate obtains a gradient structure composed of more fine equiaxed grains on the surface and fibrous deformed grains inside. If the initial rolling temperature, final rolling temperature, and coiling temperature of the finishing mill are too high, a mixed microstructure consisting of coarse equiaxed grains on the surface and partially recrystallized equiaxed grains in the interior will be obtained; if the initial rolling temperature and final rolling temperature of the finishing mill are too low, the fine equiaxed grains on the surface will decrease sharply, and the deformed grains in the interior will increase sharply.

[0027] (5) The purpose of controlling the thickness of hot-rolled plates to 2.4 to 2.8 mm is to reduce the subsequent cold rolling load while ensuring the toughness and plasticity of the cold rolling process. The cold rolling processing performance of steel with ferritic structure exhibits a significant thickness effect. If the thickness of the hot-rolled plate is too large, the tendency for edge cracking during the cold rolling process will increase; if the thickness of the hot-rolled plate is too small, the difficulty of thickness accuracy and plate shape control during the hot rolling process will increase sharply.

[0028] (6) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 20-35℃ / h. If the heating rate is too low, the production efficiency is low, limiting the furnace's production capacity. If the heating rate is too high, the temperature gradient between the outside and inside of the steel coil, and between the upper and lower parts, will increase, leading to increased stress between the steel plates and causing steel sticking. The temperature T in the soaking section is 620-690℃, and the soaking time t satisfies t=15+(690-T)×(0.3~0.5)h. If the soaking temperature is too high or the soaking time is too long, on the one hand, the equiaxed grains on the surface of the steel plate will grow rapidly, making it difficult to obtain fine equiaxed grains; on the other hand, the deformed grains inside the steel plate will transform into coarse equiaxed grains due to rapid static recrystallization, making it difficult to obtain flat recrystallized grains. Therefore, it is impossible to obtain a gradient grain structure consisting of fine equiaxed grains on the surface of the steel plate and flat recrystallized grains inside the steel plate, which deteriorates the toughness and plasticity of the steel plate and leads to severe edge cracking during cold rolling. If the temperature in the soaking zone is too low and the soaking time is too short, more of the deformed grains inside the steel plate will remain due to insufficient recrystallization and will not be completely transformed into flat recrystallized grains. The cooling rate in the cooling zone is 15-40℃ / h. If the cooling rate is too low, the production efficiency is low, limiting the furnace's production capacity; if the cooling rate is too high, the temperature gradient between the outside and inside, and between the top and bottom of the steel coil will increase, leading to increased stress between the steel plates and causing steel sticking. The purpose of using a hydrogen atmosphere in the heating, soaking, and cooling zones is to utilize the high heat transfer efficiency of hydrogen and prevent further oxidation and nitriding of the steel plate in the furnace.

[0029] (7) After uncoiling, the hot-rolled annealed coils undergo pickling and cold rolling sequentially in the pickling and cold rolling mill. Because a hydrogen-reducing atmosphere is used in the bell-type annealing furnace, the iron oxide scale on the steel plate surface is largely reduced to iron, leaving only a small amount of iron oxide scale debris. Therefore, a low-concentration 1-2% hydrochloric acid aqueous solution is sufficient to remove it, and a higher pickling temperature of 50-85℃ is used to improve pickling efficiency. Since the pickled steel plate needs to travel for a certain period before reaching the cold rolling mill, this process involves temperature drop. Therefore, before the first pass of cold rolling, the pickled plate needs to be preheated to 70-100℃ to reduce deformation resistance and further improve the toughness and plasticity of the steel plate. The target thickness of the cold-rolled steel plate is 0.20-0.50 mm, which is the conventional rolling thickness of the existing pickling and rolling mill. If the target thickness is too small, the deformation resistance increases sharply, making strip breakage more likely during continuous rolling and hindering smooth production.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention, through the coordinated control of heating, roughing, finishing, and coiling process parameters, ensures that the hot-rolled sheet achieves a gradient microstructure composed of numerous fine equiaxed grains on the surface and fibrous deformed grains inside. Furthermore, through coordinated control of the bell-type annealing process parameters, it ensures that the hot-rolled annealed coil achieves a gradient grain structure composed of fine equiaxed grains on the steel sheet surface and flat recrystallized grains inside the steel sheet. This gradient microstructure differs from the equiaxed recrystallized microstructure obtained by traditional normalizing treatment, exhibiting excellent deformation coordination capabilities. It can effectively prevent crack nucleation and lateral propagation, thereby significantly improving the cold-rolled plasticity and toughness of high-silicon non-oriented silicon steel.

[0032] 2. This invention avoids edge cracking during cold rolling, thus significantly reducing the risk of strip breakage due to edge cracking. This eliminates the need for edge trimming during cold rolling, improving yield and production efficiency. Furthermore, it eliminates the need for strict control over pass reduction ratios and roll configurations, simplifying cold rolling production and making it easier to operate. By preventing edge cracking, the method of this application helps improve the rolling stability of the cold rolling mill, thereby increasing rolling speed and hourly output, further improving production efficiency. Since the required homogenization temperature of the bell-type annealing furnace is significantly lower than that of traditional large continuous normalizing furnaces for hot-rolled plates, this technology is beneficial for energy conservation and cost reduction.

[0033] 3. Unlike traditional normalized steel plates with a thicker layer of iron oxide scale, the technology of this invention utilizes a hydrogen reducing atmosphere within the bell-type annealing furnace. This reduces a large portion of the iron oxide scale on the steel plate surface to iron, leaving only a small amount of scale debris. Therefore, a low-concentration hydrochloric acid solution can be used as the pickling solution to remove it completely, helping to reduce hydrochloric acid consumption and pickling costs. Furthermore, since the bell-type annealing furnace is less expensive than traditional large continuous normalizing furnaces for hot-rolled plates, it also helps to reduce equipment investment and lower equipment costs. Attached Figure Description

[0034] Figure 1 Typical metallographic images of the longitudinal section of the hot-rolled plate in Embodiment 1 of this invention;

[0035] Figure 2 Typical metallographic images of the longitudinal section of the hot-rolled annealed plate in Embodiment 1 of this invention;

[0036] Figure 3 Typical appearance morphology photograph of the edge of the cold-rolled sheet in Embodiment 1 of the present invention;

[0037] Figure 4 Typical metallographic images of the longitudinal section of the hot-rolled annealed plate in Embodiment 2 of the present invention;

[0038] Figure 5Typical appearance morphology photograph of the edge of the cold-rolled sheet in Embodiment 2 of the present invention;

[0039] Figure 6 Typical appearance morphology photograph of the edge of the cold-rolled sheet in Embodiment 3 of the present invention;

[0040] Figure 7 Typical metallographic images of the longitudinal section of the hot-rolled plate in Comparative Example 1 of this invention;

[0041] Figure 8 Typical metallographic images of the longitudinal section of the hot-rolled annealed plate in Comparative Example 1 of this invention;

[0042] Figure 9 A photograph of the typical appearance morphology of the edge of the cold-rolled sheet in Comparative Example 1 of this invention;

[0043] Figure 10 Typical metallographic images of the longitudinal section of the hot-rolled annealed plate in Comparative Example 2 of this invention;

[0044] Figure 11 A photograph showing the typical appearance of the edge of the cold-rolled sheet in Comparative Example 2 of this invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. The following are preferred embodiments of the present invention.

[0046] The metallographic microstructure observation in this invention was performed using a Leica DM2500 M metallographic microscope. The morphological photographs of the edge of the cold-rolled sheet in this invention were taken using a HUAWEI Mate 50 Pro mobile phone. The impact energy testing of the hot-rolled annealed sheet in this invention was performed using a SANS ZBC2452-B pendulum impact testing machine. Samples with a length of 5 cm and a width of 10 mm were cut parallel to the initial hot-rolling direction, and impact samples with a 45° V-notch and a depth of 2 mm were machined. The impact direction was perpendicular to the initial hot-rolling direction, and the unit of impact energy was J. The average value of three impact samples was taken. Before the impact test, the samples were kept in hot water at 85±15℃ for 10 min.

[0047] The following are embodiments and comparative examples of the present invention.

[0048] Example 1

[0049] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0050] (1) The chemical composition of the continuously cast billet by weight percentage is: Si: 3.2%, Mn: 0.20%, Al: 0.25%, C: 0.0020%, S: 0.0015%, N: 0.0008%, O: 0.0005%, Sn: 0.06%, with the balance being Fe and unavoidable impurities, and the thickness is 230 mm. The continuously cast billet is heated to 1070℃ and held in the furnace for 120 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1020℃ and the final rolling temperature is 930℃ to obtain an intermediate billet with a thickness of 20 mm.

[0051] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 890℃ and a final rolling temperature of 790℃ to obtain a 2.4mm thick hot-rolled plate. The hot-rolled plate is then cooled to 510℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0052] The surface layer of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 13 μm, while the interior layer contains severely elongated fibrous deformed grains. The equiaxed grain region on the surface accounts for 10% of the total thickness of the steel plate. Metallographic images of the longitudinal section of the hot-rolled plate are shown below. Figure 1 .

[0053] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 20℃ / h, the temperature in the soaking section is 620℃, the soaking time is 43h, the cooling rate in the cooling section is 15℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0054] The surface layer of the hot-rolled annealed steel coil consists of equiaxed grains with an average grain size of 32 μm. The interior of the steel sheet contains flattened recrystallized grains with an average width of 45 μm and an average aspect ratio of 5. The equiaxed grain region on the surface of the steel sheet accounts for 23% of the total thickness of the steel sheet. Metallographic images of the longitudinal section of the hot-rolled annealed steel sheet are shown below. Figure 2 The impact energy of hot-rolled annealed plates is shown in Table 1.

[0055] (4) After uncoiling, the hot-rolled annealed coil undergoes pickling and cold rolling sequentially in a pickling and cold rolling mill. The pickling solution is a 1% hydrochloric acid aqueous solution, and the pickling temperature is 50℃. Before the first pass of cold rolling, the pickled plate needs to be preheated to 70℃. The thickness of the cold-rolled steel plate is 0.50mm. See the photograph of the edge morphology of the cold-rolled plate. Figure 3 No edge cracks occurred.

[0056] Example 2

[0057] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0058] (1) The chemical composition of the continuously cast billet by weight percentage is: Si: 3.4%, Mn: 0.45%, Al: 1.0%, C: 0.0024%, S: 0.0022%, N: 0.0010%, O: 0.0006%, Sb: 0.07%, with the balance being Fe and unavoidable impurities, and the thickness is 230 mm. The continuously cast billet is heated to 1100℃ and held in the furnace for 180 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1070℃ and the final rolling temperature is 980℃ to obtain an intermediate billet with a thickness of 30 mm.

[0059] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 940℃ and a final rolling temperature of 838℃ to obtain a 2.5mm thick hot-rolled plate. The hot-rolled plate is then cooled to 570℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0060] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 20μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 15% of the entire thickness of the steel plate.

[0061] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 35℃ / h, the temperature in the soaking section is 690℃, the soaking time is 15h, the cooling rate in the cooling section is 35℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0062] The surface layer of the hot-rolled annealed steel coil consists of equiaxed grains with an average grain size of 45 μm. The interior of the steel sheet contains flattened recrystallized grains with an average width of 66 μm and an average aspect ratio of 2.5. The equiaxed grain region on the surface of the steel sheet accounts for 27% of the total thickness of the steel sheet. Metallographic images of the longitudinal section of the hot-rolled annealed steel sheet are shown below. Figure 4 The impact energy of hot-rolled annealed plates is shown in Table 1.

[0063] (4) After uncoiling, the hot-rolled annealed coil undergoes pickling and cold rolling sequentially in a pickling and cold rolling mill. The pickling solution is a 2% hydrochloric acid aqueous solution, and the pickling temperature is 65℃. Before the first pass of cold rolling, the pickled plate needs to be preheated to 90℃. The thickness of the cold-rolled steel plate is 0.35mm. See the photograph of the edge morphology of the cold-rolled plate. Figure 5 No edge cracks occurred.

[0064] Example 3

[0065] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0066] (1) The chemical composition of the continuously cast billet by weight percentage is as follows: Si: 4.10%, Mn: 0.55%, Al: 1.0%, C: 0.0015%, S: 0.0010%, N: 0.0006%, O: 0.0007%, Sn: 0.07%, Sb: 0.08%, with the balance being Fe and unavoidable impurities. The thickness is 220 mm. The continuously cast billet is heated to 1090℃ and held in the furnace for 150 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water before rough rolling. The initial rolling temperature is 1050℃ and the final rolling temperature is 970℃ to obtain an intermediate billet with a thickness of 30 mm.

[0067] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 920℃ and a final rolling temperature of 830℃ to obtain a 2.6mm thick hot-rolled plate. The hot-rolled plate is then cooled to 560℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0068] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 24μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 16% of the entire thickness of the steel plate.

[0069] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 30℃ / h, the temperature in the soaking section is 680℃, the soaking time is 18h, the cooling rate in the cooling section is 40℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0070] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 46 μm. The interior of the steel plate has flat recrystallized grains with an average width of 71 μm and an average aspect ratio of 3. The equiaxed grain region on the surface of the steel plate accounts for 45% of the entire thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0071] (4) After uncoiling, the hot-rolled annealed coil undergoes pickling and cold rolling sequentially in a pickling and cold rolling mill. The pickling solution is a 1.5% hydrochloric acid aqueous solution, and the pickling temperature is 80℃. Before the first pass of cold rolling, the pickled plate needs to be preheated to 100℃. The thickness of the cold-rolled steel plate is 0.25mm. See the photograph of the edge morphology of the cold-rolled plate. Figure 6 No edge cracks occurred.

[0072] Example 4

[0073] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0074] (1) The chemical composition of the continuously cast billet by weight percentage is as follows: Si: 3.50%, Mn: 0.35%, Al: 0.51%, C: 0.0025%, S: 0.0024%, N: 0.0018%, O: 0.0010%, Sn: 0.15%, with the balance being Fe and unavoidable impurities, and the thickness is 70 mm. The continuously cast billet is heated to 1090℃ and held in the furnace for 90 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1050℃ and the final rolling temperature is 960℃ to obtain an intermediate billet with a thickness of 20 mm.

[0075] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 900℃ and a final rolling temperature of 790℃ to obtain a 2.75mm thick hot-rolled plate. The hot-rolled plate is then cooled to 570℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0076] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 13μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 8.5% of the total thickness of the steel plate.

[0077] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 24℃ / h, the temperature in the soaking section is 650℃, the soaking time is 35h, the cooling rate in the cooling section is 17℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0078] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 32 μm. The interior of the steel plate has flat recrystallized grains with an average width of 45 μm and an average aspect ratio of 6. The equiaxed grain region on the surface accounts for 25% of the total thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0079] (4) The hot-rolled annealed coils are sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution is a 1.3% hydrochloric acid aqueous solution, and the pickling temperature is 85℃. During the first pass of cold rolling, the temperature of the steel plate is 75℃. The thickness of the steel plate after cold rolling is 0.20mm. See the photograph of the edge morphology of the cold-rolled plate. Figure 6 No edge cracks occurred.

[0080] Example 5

[0081] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0082] (1) The chemical composition of the continuously cast billet by weight percentage is: Si: 3.90%, Mn: 0.35%, Al: 0.51%, C: 0.0025%, S: 0.0024%, N: 0.0018%, O: 0.0010%, Sn: 0.15%, with the balance being Fe and unavoidable impurities, and the thickness is 70 mm. The continuously cast billet is heated to 1090℃ and held in the furnace for 90 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1050℃ and the final rolling temperature is 960℃ to obtain an intermediate billet with a thickness of 20 mm.

[0083] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 900℃ and a final rolling temperature of 790℃ to obtain a 2.75mm thick hot-rolled plate. The hot-rolled plate is then cooled to 570℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0084] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 13μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 8.5% of the total thickness of the steel plate.

[0085] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 32℃ / h, the temperature in the soaking section is 620℃, the soaking time is 50h, the cooling rate in the cooling section is 36℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0086] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 37 μm. The interior of the steel plate has flat recrystallized grains with an average width of 55 μm and an average aspect ratio of 3.5. The equiaxed grain region on the surface of the steel plate accounts for 41% of the entire thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0087] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 1.7% hydrochloric acid aqueous solution, and the pickling temperature was 82℃. During the first pass of cold rolling, the temperature of the steel plate was 83℃. The thickness of the steel plate after cold rolling was 0.20mm. The cracking situation at the edge of the cold-rolled plate is shown in Table 1. No edge cracks occurred.

[0088] Example 6

[0089] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0090] (1) The chemical composition of the continuously cast billet by weight percentage is: Si: 4.0%, Mn: 0.51%, Al: 1.4%, C: 0.0015%, S: 0.0010%, N: 0.0006%, O: 0.0007%, Sn: 0.07%, Sb: 0.03%, with the balance being Fe and unavoidable impurities, and the thickness is 210 mm. The continuously cast billet is heated to 1090℃ and held in the furnace for 150 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1050℃ and the final rolling temperature is 970℃ to obtain an intermediate billet with a thickness of 30 mm.

[0091] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 920℃ and a final rolling temperature of 830℃ to obtain a 2.6mm thick hot-rolled plate. The hot-rolled plate is then cooled to 560℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0092] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 24μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 16% of the entire thickness of the steel plate.

[0093] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 25℃ / h, the temperature in the soaking section is 625℃, the soaking time is 47h, the cooling rate in the cooling section is 40℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0094] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 38 μm. The interior of the steel plate has flat recrystallized grains with an average width of 69 μm and an average aspect ratio of 4. The equiaxed grain region on the surface of the steel plate accounts for 55% of the entire thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0095] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 1.8% hydrochloric acid aqueous solution, and the pickling temperature was 80℃. During the first pass of cold rolling, the temperature of the steel plate was 100℃. The thickness of the steel plate after cold rolling was 0.25mm. The cracking situation at the edge of the cold-rolled plate is shown in Table 1. No edge cracks occurred.

[0096] Example 7

[0097] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0098] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 3.75%, Mn: 0.50%, Al: 0.85%, C: 0.0020%, S: 0.0020%, N: 0.0010%, O: 0.0006%, Sn: 0.10%, Sb: 0.04%, with the balance being Fe and unavoidable impurities, and the thickness is 150 mm. The continuously cast billet is heated to 1100℃ and held in the furnace for 180 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1070℃ and the final rolling temperature is 980℃ to obtain an intermediate billet with a thickness of 30 mm.

[0099] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 935℃ and a final rolling temperature of 820℃ to obtain a 2.6mm thick hot-rolled plate. The hot-rolled plate is then cooled to 510℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0100] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 23 μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 16% of the entire thickness of the steel plate.

[0101] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 22℃ / h, the temperature in the soaking section is 640℃, the soaking time is 30h, the cooling rate in the cooling section is 38℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0102] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 48 μm. The interior of the steel plate has flat recrystallized grains with an average width of 75 μm and an average aspect ratio of 2.0. The equiaxed grain region on the surface of the steel plate accounts for 49% of the entire thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0103] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 2% hydrochloric acid aqueous solution, and the pickling temperature was 65℃. During the first pass of cold rolling, the temperature of the steel plate was 100℃. The thickness of the steel plate after cold rolling was 0.30mm. The cracking situation at the edge of the cold-rolled plate is shown in Table 1. No edge cracks occurred.

[0104] Example 8

[0105] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0106] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 3.35%, Mn: 0.40%, Al: 0.68%, C: 0.0010%, S: 0.0011%, N: 0.0010%, O: 0.0006%, Sb: 0.10%, with the balance being Fe and unavoidable impurities, and the thickness is 180 mm. The continuously cast billet is heated to 1080℃ and held in the furnace for 140 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1030℃ and the final rolling temperature is 960℃ to obtain an intermediate billet with a thickness of 28 mm.

[0107] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 900℃ and a final rolling temperature of 800℃ to obtain a 2.5mm thick hot-rolled plate. The hot-rolled plate is then cooled to 540℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0108] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 17μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 6% of the total thickness of the steel plate.

[0109] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 23℃ / h, the temperature in the soaking section is 660℃, the soaking time is 25h, the cooling rate in the cooling section is 15℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0110] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 38 μm. The interior of the steel plate has flat recrystallized grains with an average width of 60 μm and an average aspect ratio of 2.0. The equiaxed grain region on the surface of the steel plate accounts for 22% of the entire thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0111] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 2.0% hydrochloric acid aqueous solution, and the pickling temperature was 55℃. During the first pass of cold rolling, the temperature of the steel plate was 90℃. The thickness of the steel plate after cold rolling was 0.50mm. The cracking situation at the edge of the cold-rolled plate is shown in Table 1. No edge cracks occurred.

[0112] Example 9

[0113] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0114] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 3.65%, Mn: 0.40%, Al: 0.90%, C: 0.0010%, S: 0.0011%, N: 0.0010%, O: 0.0006%, Sb: 0.08%, with the balance being Fe and unavoidable impurities, and the thickness is 120 mm. The continuously cast billet is heated to 1090℃ and held in the furnace for 95 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1025℃ and the final rolling temperature is 975℃ to obtain an intermediate billet with a thickness of 21 mm.

[0115] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 925℃ and a final rolling temperature of 810℃ to obtain a 2.8mm thick hot-rolled plate. The hot-rolled plate is then cooled to 540℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0116] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 23μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 15% of the entire thickness of the steel plate.

[0117] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 35℃ / h, the temperature in the soaking section is 680℃, the soaking time is 20h, the cooling rate in the cooling section is 38℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0118] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 40 μm. The interior of the steel plate has flat recrystallized grains with an average width of 72 μm and an average aspect ratio of 6. The equiaxed grain region on the surface of the steel plate accounts for 33% of the entire thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0119] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 2.0% hydrochloric acid aqueous solution, and the pickling temperature was 80℃. During the first pass of cold rolling, the temperature of the steel plate was 100℃. The thickness of the steel plate after cold rolling was 0.50mm. The cracking situation at the edge of the cold-rolled plate is shown in Table 1. No edge cracks occurred.

[0120] Comparative Example 1

[0121] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0122] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 3.2%, Mn: 0.20%, Al: 0.25%, C: 0.0020%, S: 0.0015%, N: 0.0008%, O: 0.0005%, Sn: 0.06%, with the balance being Fe and unavoidable impurities, and the thickness is 230 mm. The continuously cast billet is heated to 1120℃ and held in the furnace for 200 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1080℃ and the final rolling temperature is 991℃ to obtain an intermediate billet with a thickness of 20 mm.

[0123] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 952℃ and a final rolling temperature of 860℃ to obtain a 2.4mm thick hot-rolled plate. The hot-rolled plate is then cooled to 590℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0124] The surface layer of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 27 μm, while the interior of the steel sheet contains severely elongated fibrous deformed grains. The equiaxed grain region on the surface accounts for 20% of the total thickness of the steel sheet. Metallographic images of the longitudinal section of the hot-rolled sheet are shown below. Figure 7 .

[0125] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 38℃ / h, the temperature in the soaking section is 705℃, the soaking time is 30h, the cooling rate in the cooling section is 40℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0126] The surface layer of the hot-rolled annealed steel coil consists of equiaxed grains with an average grain size of 55 μm. The interior of the steel sheet contains flattened recrystallized grains with an average width of 80 μm and an average aspect ratio of 1.5. The equiaxed grain region on the surface of the steel sheet accounts for 50% of the total thickness of the steel sheet. Metallographic images of the longitudinal section of the hot-rolled annealed steel sheet are shown below. Figure 8 The impact energy of hot-rolled annealed plates is shown in Table 1.

[0127] (4) The hot-rolled annealed coils are sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution is a 1% hydrochloric acid aqueous solution, and the pickling temperature is 50℃. During the first pass of cold rolling, the temperature of the steel plate is 70℃. The thickness of the steel plate after cold rolling is 0.50mm. See the photograph of the edge morphology of the cold-rolled plate. Figure 9 Edge cracks occurred.

[0128] Comparative Example 2

[0129] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0130] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 4.10%, Mn: 0.50%, Al: 0.65%, C: 0.0020%, S: 0.0020%, N: 0.0010%, O: 0.0006%, Sb: 0.10%, with the balance being Fe and unavoidable impurities, and the thickness is 230 mm. The continuously cast billet is heated to 1150℃ and held in the furnace for 80 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1100℃ and the final rolling temperature is 1010℃ to obtain an intermediate billet with a thickness of 30 mm.

[0131] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 970℃ and a final rolling temperature of 885℃ to obtain a 2.6mm thick hot-rolled plate. The hot-rolled plate is then cooled to 650℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0132] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 30μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 22% of the entire thickness of the steel plate.

[0133] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 30℃ / h, the temperature T in the soaking section is 730℃, the soaking time is 20h, the cooling rate in the cooling section is 20℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0134] The hot-rolled annealed steel coil exhibits equiaxed recrystallized grains on both the surface and interior, without the formation of flattened recrystallized grains, with an average grain size of 87 μm. Metallographic images of the longitudinal section of the hot-rolled annealed steel coil are shown below. Figure 10 The impact energy of hot-rolled annealed plates is shown in Table 1.

[0135] (4) The hot-rolled annealed coils are sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution is a 2% hydrochloric acid aqueous solution, and the pickling temperature is 65℃. During the first pass of cold rolling, the temperature of the steel plate is 90℃. The thickness of the steel plate after cold rolling is 0.35mm. See the photograph of the edge morphology of the cold-rolled plate. Figure 11 Edge cracks occurred.

[0136] Comparative Example 3

[0137] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0138] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 4.10%, Mn: 0.50%, Al: 1.20%, C: 0.0018%, S: 0.0010%, N: 0.0012%, O: 0.0008%, Sn: 0.06%, Sb: 0.08%, with the balance being Fe and unavoidable impurities, and the thickness is 230 mm. The continuously cast billet is heated to 1150℃ and held in the furnace for 80 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1100℃ and the final rolling temperature is 1010℃ to obtain an intermediate billet with a thickness of 30 mm.

[0139] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 970℃ and a final rolling temperature of 885℃ to obtain a 2.6mm thick hot-rolled plate. The hot-rolled plate is then cooled to 650℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0140] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 15μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 10% of the entire thickness of the steel plate.

[0141] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 30℃ / h, the temperature in the soaking section is 600℃, the soaking time is 15h, the cooling rate in the cooling section is 20℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0142] The surface layer of the hot-rolled annealed steel coil consists of equiaxed grains with an average grain size of 22 μm. The interior of the steel coil contains fibrous deformed grains, without the formation of flat recrystallized grains. The impact energy of the hot-rolled annealed steel coil is shown in Table 1.

[0143] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 1.5% hydrochloric acid aqueous solution, and the pickling temperature was 65℃. During the first pass of cold rolling, the temperature of the steel plate was 85℃. The thickness of the steel plate after cold rolling was 0.20mm. The cracking of the edge of the cold-rolled plate is shown in Table 1, indicating that edge cracking occurred.

[0144] Comparative Example 4

[0145] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0146] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 3.75%, Mn: 0.50%, Al: 1.50%, C: 0.0024%, S: 0.0025%, N: 0.0015%, O: 0.0004%, Sn: 0.10%, with the balance being Fe and unavoidable impurities, and the thickness is 230 mm. The continuously cast billet is heated to 1100℃ and held in the furnace for 150 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1070℃ and the final rolling temperature is 980℃ to obtain an intermediate billet with a thickness of 30 mm.

[0147] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 950℃ and a final rolling temperature of 850℃ to obtain a 2.6mm thick hot-rolled plate. The hot-rolled plate is then cooled to 600℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0148] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 16μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 4% of the total thickness of the steel plate.

[0149] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 30℃ / h, the temperature in the soaking section is 600℃, the soaking time is 47h, the cooling rate in the cooling section is 20℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0150] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 40 μm. No flat recrystallized grains are formed inside the steel plate, while fibrous, non-recrystallized grains account for 60% of the total thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0151] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 1.7% hydrochloric acid aqueous solution, and the pickling temperature was 65℃. During the first pass of cold rolling, the temperature of the steel plate was 90℃. The thickness of the steel plate after cold rolling was 0.30mm. The cracking of the edge of the cold-rolled plate is shown in Table 1, indicating that edge cracking occurred.

[0152] Comparative Example 5

[0153] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0154] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 3.45%, Mn: 0.20%, Al: 0.55%, C: 0.0019%, S: 0.0015%, N: 0.0015%, O: 0.0005%, Sn: 0.12%, with the balance being Fe and unavoidable impurities, and the thickness is 230 mm. The continuously cast billet is heated to 1100℃ and held in the furnace for 135 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1055℃ and the final rolling temperature is 974℃ to obtain an intermediate billet with a thickness of 26 mm.

[0155] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 940℃ and a final rolling temperature of 860℃ to obtain a 2.4mm thick hot-rolled plate. The hot-rolled plate is then cooled to 580℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0156] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 25μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 23% of the entire thickness of the steel plate.

[0157] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 25℃ / h, the temperature in the soaking section is 680℃, the soaking time is 25h, the cooling rate in the cooling section is 40℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0158] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 55 μm. The interior of the steel plate has flat recrystallized grains with an average width of 110 μm and an average aspect ratio of 2. The equiaxed grain region on the surface of the steel plate accounts for 50% of the entire thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0159] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 2.0% hydrochloric acid aqueous solution, and the pickling temperature was 85℃. During the first pass of cold rolling, the temperature of the steel plate was 100℃. The thickness of the steel plate after cold rolling was 0.50mm. The cracking of the edge of the cold-rolled plate is shown in Table 1, indicating that edge cracking occurred.

[0160] Comparative Example 6

[0161] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0162] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 3.90%, Mn: 0.35%, Al: 1.42%, C: 0.0022%, S: 0.0025%, N: 0.0011%, O: 0.0004%, Sb: 0.15%, with the balance being Fe and unavoidable impurities, and the thickness is 170 mm. The continuously cast billet is heated to 1130℃ and held in the furnace for 155 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1090℃ and the final rolling temperature is 985℃ to obtain an intermediate billet with a thickness of 29 mm.

[0163] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 943℃ and a final rolling temperature of 855℃ to obtain a 2.8mm thick hot-rolled plate. The hot-rolled plate is then cooled to 620℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0164] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 32μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 21% of the entire thickness of the steel plate.

[0165] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 18℃ / h, the temperature in the soaking section is 750℃, the soaking time is 50h, the cooling rate in the cooling section is 20℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0166] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 70 μm, while the interior of the steel coil has coarse equiaxed recrystallized grains with an average grain size of 110 μm. The impact energy of the hot-rolled annealed steel coil is shown in Table 1.

[0167] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 1.8% hydrochloric acid aqueous solution, and the pickling temperature was 85℃. During the first pass of cold rolling, the temperature of the steel plate was 96℃. The thickness of the steel plate after cold rolling was 0.35mm. The cracking of the edge of the cold-rolled plate is shown in Table 1, indicating that edge cracking occurred.

[0168] Comparative Example 7

[0169] A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel specifically includes the following steps:

[0170] (1) The chemical composition of the continuously cast billet by weight percentage is Si: 3.31%, Mn: 0.55%, Al: 0.75%, C: 0.0015%, S: 0.0010%, N: 0.0013%, O: 0.0008%, Sn: 0.02%, with the balance being Fe and unavoidable impurities, and the thickness is 230 mm. The continuously cast billet is heated to 1090℃ and held in the furnace for 100 min. After being taken out of the furnace, the surface iron oxide scale is removed by high pressure water and then rough rolling is performed. The initial rolling temperature is 1060℃ and the final rolling temperature is 965℃ to obtain an intermediate billet with a thickness of 28 mm.

[0171] (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 920℃ and a final rolling temperature of 820℃ to obtain a hot-rolled plate with a thickness of 2.75mm. The hot-rolled plate is then cooled to 590℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil.

[0172] The surface of the hot-rolled steel coil consists of fine equiaxed grains with an average grain size of 23 μm, while the interior of the steel plate consists of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 3% of the total thickness of the steel plate.

[0173] (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 20℃ / h, the temperature in the soaking section is 660℃, the soaking time is 15h, the cooling rate in the cooling section is 34℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil.

[0174] The surface layer of the hot-rolled annealed steel coil has equiaxed grains with an average grain size of 34 μm. The interior of the steel plate has flat recrystallized grains with an average width of 91 μm and an average aspect ratio of 1.6. The equiaxed grain region on the surface of the steel plate accounts for 26% of the entire thickness of the steel plate. The impact energy of the hot-rolled annealed steel plate is shown in Table 1.

[0175] (4) The hot-rolled annealed coils were sequentially pickled and cold-rolled in the pickling and cold rolling mill. The pickling solution was a 2% hydrochloric acid aqueous solution, and the pickling temperature was 50℃. During the first pass of cold rolling, the temperature of the steel plate was 80℃. The thickness of the steel plate after cold rolling was 0.50mm. The cracking of the edge of the cold-rolled plate is shown in Table 1, indicating that edge cracking occurred.

[0176] As can be seen from the comparative examples, when the manufacturing process is not within the scope of this invention, the impact energy of the hot-rolled annealed sheet is very low, the toughness and plasticity of the steel sheet are very poor, and edge cracking occurs during cold rolling. The hot-rolled annealed sheets in the embodiments of this invention all exhibit significantly better impact energy than the comparative examples, and no edge cracking occurs during cold rolling.

[0177] Table 1 shows the impact energy and cold-rolled edge cracking of the hot-rolled annealed plates in the examples and comparative examples.

[0178]

Claims

1. A method for improving the cold rolling processing properties of high-silicon non-oriented silicon steel, characterized in that, Specifically, the following steps are included: (1) Heat the continuous casting billet with a silicon mass percentage of not less than 3.2% and a thickness of 70-240 mm to 1060-1100℃, hold it in the furnace for 90-180 min, remove the surface iron oxide scale with high pressure water after taking it out of the furnace, and then perform rough rolling. The initial rolling temperature is 1020-1070℃ and the final rolling temperature is 930-980℃ to obtain an intermediate billet with a thickness of 20-30 mm. (2) After removing the surface iron oxide scale by high pressure water, the intermediate billet is precision rolled at an initial rolling temperature of 890-940℃ and a final rolling temperature of 790-840℃ to obtain a hot-rolled plate with a thickness of 2.4-2.8mm. The hot-rolled plate is then cooled to 500-570℃ by laminar flow water and then coiled to obtain a hot-rolled plate coil. (3) The hot-rolled coil is placed in a bell-type annealing furnace for annealing treatment. The heating rate in the heating section is 20-35℃ / h, the temperature T in the soaking section is 620-690℃, the soaking time t satisfies t=15+(690-T)×(0.3-0.5)h, the cooling rate in the cooling section is 15-40℃ / h, the atmosphere in the furnace is hydrogen, and after cooling to room temperature, it is taken out from the bell-type annealing furnace to obtain the hot-rolled annealed coil. (4) After the hot-rolled annealed coil is uncoiled, it is pickled and cold-rolled in the pickling and cold rolling mill to obtain a cold-rolled steel plate with a thickness of 0.20 to 0.50 mm.

2. The method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel according to claim 1, characterized in that, In step (1), the chemical composition of the continuously cast billet by weight percentage is: Si: 3.2-4.1%, Mn: 0.20-0.55%, Al: 0.2-1.5%, C≤0.0027%, S≤0.0025%, N≤0.0020%, O≤0.0010%, Sn or Sb or Sn+Sb≤0.15%, with the balance being Fe and unavoidable impurities.

3. The method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel according to claim 1, characterized in that, In step (2), the surface of the hot-rolled coil is composed of fine equiaxed grains with an average grain size of 10-25 μm, while the interior of the steel plate is composed of severely elongated fibrous deformed grains. The equiaxed grain region on the surface of the steel plate accounts for 5-18% of the entire thickness range of the steel plate.

4. The method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel according to claim 1, characterized in that, In step (3), the surface layer of the hot-rolled annealed steel coil obtained has equiaxed grains with an average grain size of 30-50 μm.

5. The method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel according to claim 1, characterized in that, In step (3), the steel plate obtained by hot rolling annealing has flat recrystallized grains inside, with an average width of 35-75 μm and an average aspect ratio of 2-6.

6. The method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel according to claim 1, characterized in that, In step (3), the equiaxed grain region on the surface of the hot-rolled annealed steel coil accounts for 20-55% of the entire steel plate thickness range.

7. The method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel according to claim 1, characterized in that, In step (4), the pickling solution is a hydrochloric acid aqueous solution with a mass concentration of 1-2%, and the pickling temperature is 50-85℃.

8. The method for improving the cold rolling processing performance of high-silicon non-oriented silicon steel according to claim 1, characterized in that, In step (4), the pickled plate needs to be preheated to 70-100°C before the first cold rolling pass.

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