Wide strip sheet of non-oriented silicon steel and method for manufacturing the same

Abstract

This invention discloses a wide strip of non-oriented silicon steel and its preparation method. The preparation method includes: preparing a single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm by steelmaking, billet casting, hot rolling, pickling, and cold rolling; stacking two single-layer cold-rolled coils of the same thickness and width, separating them by a high-temperature resistant insulating coating to form a laminate; the difference in Si content, Al content, and Mn content between the two single-layer cold-rolled coils does not exceed 0.20%, and the difference in P content does not exceed 0.02%; rolling the laminate on a single-stand rolling mill for 2-3 passes with a total reduction rate of 30%-50% to obtain a double-layer cold-rolled coil with a total thickness of 0.20-0.50 mm; and subjecting the obtained double-layer cold-rolled coil to continuous annealing, coating, and finishing to obtain the finished non-oriented silicon steel product.

Description

Technical Field

[0001] This invention belongs to the field of steel material preparation technology, and relates to a method for preparing a wide strip of non-oriented silicon steel, and the wide strip of non-oriented silicon steel prepared by the method. Background Technology

[0002] Non-oriented silicon steel is an important soft magnetic material, mainly used to manufacture the stator and rotor cores of various motors and generators. Iron loss is a key indicator for distinguishing non-oriented silicon steel grades. With the rapid development of new energy vehicles, their drive motors are developing towards higher speeds, higher power densities, and higher efficiency. As motor speeds increase and frequencies rise, the iron losses of the motor increase dramatically.

[0003] To reduce iron loss in high-frequency, high-speed motors, the thickness of non-oriented silicon steel should be reduced. However, during cold rolling, when the thickness of the rolled piece is reduced to a certain value, it cannot be further reduced. Even increasing the rolling force to the maximum equipment capacity or increasing the number of rolling passes will not help. This thickness limit is called the minimum rollable thickness for cold rolling.

[0004] Studies have shown that the minimum rollable thickness for cold rolling is directly proportional to the diameter of the mill's work rolls and the width of the rolled piece. Therefore, to obtain thinner non-oriented silicon steel and reduce iron loss, wide strip steel is typically slit into narrow strip steel, which is then cold rolled using a narrow strip steel mill. This method suffers from low production efficiency and high cost.

[0005] To date, there has been no report on the use of wide strip steel rolling mills to produce wide strip steel sheets of non-oriented silicon steel. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a wide strip of non-oriented silicon steel, and a wide strip of non-oriented silicon steel prepared by the method.

[0007] To achieve the above-mentioned objective, one embodiment of the present invention provides a method for preparing a wide strip of non-oriented silicon steel. The preparation method includes:

[0008] Single-layer cold-rolled coils with a width of 800–1300 mm and a thickness of 0.20–0.50 mm are produced through steelmaking, billet casting, hot rolling, pickling, and cold rolling.

[0009] Two single-layer cold-cured rolls of the same thickness and width are stacked together, and the two single-layer cold-cured rolls are separated by a high-temperature resistant insulating coating to form a laminate. The chemical composition of the two single-layer cold-cured rolls, by mass percentage, is as follows: C≤0.003%, S≤0.003%, Si:0.50~3.40%, Al:0.10~1.00%, Mn:0.20~1.00%, P:0.005~0.04%, Nb≤0.004%, V≤0.004%, Ti≤0.004%, Ni≤0.03%, Cr≤0.03%, N≤0.004%, with the remainder being Fe and unavoidable impurities. Furthermore, the difference in Si content, Al content, and Mn content between the two single-layer cold-cured rolls does not exceed 0.20%, and the difference in P content does not exceed 0.02%.

[0010] The laminate is rolled in 2 to 3 passes on a single-stand rolling mill with a total reduction of 30% to 50% to obtain a double-layer cold-rolled coil with a total thickness of 0.20 to 0.50 mm.

[0011] The resulting double-layer cold-hardened coil is subjected to continuous annealing, coating and finishing to obtain a non-oriented silicon steel finished product, which has a double-layer silicon steel sheet arranged in a stacked manner.

[0012] As a further improvement, the chemical composition of both of the single-layer cold-rolled coils further includes, by mass percentage: Sn: 0.01–0.1%, or Sb: 0.01–0.1%, or Sn+Sb: 0.01–0.1%.

[0013] As a further improvement, the chemical composition of both of the single-layer cold-rolled coils also includes, by mass percentage: Cu: 0.10–1.00%.

[0014] As a further improvement, the difference in Sn content and Sb content between the two single-layer cold-rolled coils does not exceed 0.02%, and the difference in Cu content does not exceed 0.20%.

[0015] As a further improvement, in the process of "preparing single-layer cold-rolled coils with a width of 800-1300 mm and a thickness of 0.20-0.50 mm through steelmaking, billet casting, hot rolling, pickling, and cold rolling", the microstructure of the steel after pickling and before cold rolling is a fully recrystallized microstructure.

[0016] As a further improvement, in the description of "preparing single-layer cold-rolled coils with a width of 800-1300 mm and a thickness of 0.20-0.50 mm through steelmaking, billet casting, hot rolling, pickling, and cold rolling", the hot rolling process includes sequential billet heating, rough rolling, finish rolling, and coiling. The billet heating temperature is 1090-1130℃, the heating time is 150-200 min, the initial rolling temperature of finish rolling is 900-980℃, the final rolling temperature is 840-880℃, and the coiling temperature is 580-680℃.

[0017] As a further improvement, in the process of "preparing a single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm by steelmaking, billet casting, hot rolling, pickling, and cold rolling", a normalizing process is performed between the hot rolling and the pickling process, with a normalizing temperature of 850-950℃ and a holding time of 150-200 s; or, the normalizing process is not performed between the hot rolling and the pickling process.

[0018] As a further improvement, in the continuous annealing process, the annealing temperature is 850–1000℃ and the holding time is 30–60s.

[0019] As a further improvement, in the process of "preparing a single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm by steelmaking, billet casting, hot rolling, pickling, and cold rolling", the surface roughness of the working rolls of the cold rolling mill is 3.0-5.0 μm, and the surface roughness of the single-layer cold-rolled coil is 1.0-1.5 μm.

[0020] In the phrase "rolling the laminated body in 2 to 3 passes on a single-stand rolling mill with a total reduction of 30% to 50% to obtain a double-layer cold-rolled coil with a total thickness of 0.20 to 0.50 mm", the roughness of the work rolls of the single-stand rolling mill is 0.3 to 0.6 μm.

[0021] As a further improvement, in the process of "preparing a single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm by steelmaking, billet casting, hot rolling, pickling, and cold rolling", the thickness of the obtained single-layer cold-rolled coil is the minimum rollable thickness of the rolling mill used for cold rolling.

[0022] To achieve the above-mentioned objective, one embodiment of the present invention provides a wide strip steel sheet of non-oriented silicon steel. The wide strip steel sheet comprises two layers of silicon steel sheets stacked together, the total thickness of the wide strip steel sheet is 0.20-0.50 mm, and the thickness of each silicon steel sheet is half the total thickness of the wide strip steel sheet; furthermore, the contact surface of the two silicon steel sheets has a high-temperature resistant insulating coating.

[0023] The chemical composition of each layer of silicon steel sheet, by mass percentage, is as follows: C≤0.003%, S≤0.003%, Si:0.50~3.40%, Al:0.10~1.00%, Mn:0.20~1.00%, P:0.005~0.04%, Nb≤0.004%, V≤0.004%, Ti≤0.004%, Ni≤0.03%, Cr≤0.03%, N≤0.004%, with the remainder being Fe and unavoidable impurities;

[0024] Furthermore, the differences in Si content, Al content, and Mn content between the two silicon steel plates do not exceed 0.20%, and the difference in P content does not exceed 0.02%.

[0025] The method for preparing the wide strip steel sheet includes: preparing a single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm by steelmaking, billet casting, hot rolling, pickling, and cold rolling; stacking two of the single-layer cold-rolled coils and separating them by a high-temperature resistant insulating coating to form a laminate; rolling the laminate on a single-stand rolling mill for 2-3 passes with a total reduction of 30%-50% to obtain a double-layer cold-rolled coil; and subjecting the obtained double-layer cold-rolled coil to continuous annealing, coating, and finishing to obtain the wide strip steel sheet.

[0026] As a further improvement, the chemical composition of each layer of silicon steel sheet, by mass percentage, also includes: Sn: 0.01–0.1%, or Sb: 0.01–0.1%, or Sn+Sb: 0.01–0.1%;

[0027] The difference in Sn content and the difference in Sb content between the two layers of silicon steel plates do not exceed 0.02%.

[0028] As a further improvement, the chemical composition of each layer of silicon steel sheet, by mass percentage, also includes: Cu: 0.10–1.00%;

[0029] The difference in Cu content between the two layers of silicon steel sheets shall not exceed 0.20%.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: By laminating, rolling, annealing, coating, and finishing a single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm, a double-layer non-oriented silicon steel product is obtained, with each layer of silicon steel sheet having a thickness of 0.10-0.25 mm. On the one hand, this solves the problem of limited minimum rollable thickness in wide strip steel rolling, realizing the cold rolling of wide strip steel and thin specifications of non-oriented silicon steel. The two layers of silicon steel sheets have similar compositions, making rolling less difficult and easier to ensure microstructure and properties. Furthermore, the simultaneous annealing of the two layers of silicon steel sheets greatly improves production efficiency. On the other hand, the obtained double-layer non-oriented silicon steel product can be used for subsequent lamination, reducing the processing steps for downstream enterprises (such as stator and rotor core manufacturers) and greatly improving the production efficiency of downstream products (such as stator and rotor cores). Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0032] One embodiment of the present invention provides a method for preparing non-oriented silicon steel sheet, and provides a non-oriented silicon steel sheet prepared based on the method. On the one hand, the non-oriented silicon steel sheet prepared by this method is a wide strip steel sheet, which has high production efficiency. On the other hand, the non-oriented silicon steel sheet prepared by this method can be directly used to manufacture stator and rotor cores of various motors and generators in the form of double-layer finished products. For example, double-layer lamination can be performed simultaneously to prepare stator and rotor cores, thereby improving the production efficiency of stator and rotor cores.

[0033] The preparation method includes the following steps:

[0034] Step 1 – Through steelmaking, billet casting, hot rolling, pickling, and cold rolling, single-layer cold-rolled coils with a width of 800–1300 mm and a thickness of 0.20–0.50 mm are produced;

[0035] Step 2 – Stack two single-layer cold-hardened rolls of the same thickness and width together, and separate the two single-layer cold-hardened rolls with a high-temperature resistant insulating coating to form a laminate.

[0036] Step 3 – The laminated body is rolled in 2 to 3 passes on a single-stand rolling mill with a total reduction of 30% to 50% to obtain a double-layer cold-rolled coil with a total thickness of 0.20 to 0.50 mm.

[0037] Step 4 – The resulting double-layer cold-hardened coil undergoes continuous annealing, coating, and finishing to obtain the finished non-oriented silicon steel product.

[0038] Thus, the resulting non-oriented silicon steel product is the wide strip steel sheet, which has two layers of silicon steel sheets stacked together; and, based on the high-temperature resistant insulating coating in step 2, the contact surface of the two layers of silicon steel sheets in the resulting non-oriented silicon steel product has a high-temperature resistant insulating coating; furthermore, based on the total thickness of the double-layer cold-rolled coil in step 3 being 0.20 to 0.50 mm, the total thickness of the resulting non-oriented silicon steel product is 0.20 to 0.50 mm, and the thickness of each layer of silicon steel sheet is half the total thickness of the non-oriented silicon steel product, i.e., 0.10 to 0.25 mm; in addition, the width of the resulting non-oriented silicon steel product is 800 to 1300 mm and not less than the width of the single-layer cold-rolled coil.

[0039] In step 2, the chemical composition of the two single-layer cold-rolled coils, by mass percentage, is as follows: C ≤ 0.003%, S ≤ 0.003%, Si: 0.50–3.40%, Al: 0.10–1.00%, Mn: 0.20–1.00%, P: 0.005–0.04%, Nb ≤ 0.004%, V ≤ 0.004%, Ti ≤ 0.004%, Ni ≤ 0.03%, Cr ≤ 0.03%, N ≤ 0.004%, with the remainder being Fe and unavoidable impurities. Furthermore, the difference in Si content, Al content, and Mn content between the two single-layer cold-rolled coils does not exceed 0.20%, and the difference in P content does not exceed 0.02%.

[0040] Correspondingly, the chemical composition of the two-layer silicon steel sheet of the obtained non-oriented silicon steel product is consistent with the chemical composition of the corresponding single-layer cold-rolled coil. That is, the chemical composition of the two-layer silicon steel sheet by mass percentage is: C≤0.003%, S≤0.003%, Si:0.50~3.40%, Al:0.10~1.00%, Mn:0.20~1.00%, P:0.005~0.04%, Nb≤0.004%, V≤0.004%, Ti≤0.004%, Ni≤0.03%, Cr≤0.03%, N≤0.004%, with the remainder being Fe and unavoidable impurities. Furthermore, the difference in Si content, Al content, and Mn content between the two single-layer cold-rolled coils does not exceed 0.20%, and the difference in P content does not exceed 0.02%.

[0041] Thus, in one embodiment of the present invention, by laminating, rolling, annealing, coating, and finishing a single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm, a double-layer non-oriented silicon steel product is obtained, with each layer of silicon steel sheet having a thickness of 0.10-0.25 mm. On the one hand, this solves the problem of limited minimum rollable thickness in wide strip steel rolling, realizing the cold rolling of wide strip steel and thin specifications of non-oriented silicon steel. The two layers of silicon steel sheets have similar compositions, making rolling easier and ensuring microstructure and properties. Furthermore, the simultaneous annealing of the two layers of silicon steel sheets significantly improves production efficiency. On the other hand, the obtained double-layer non-oriented silicon steel product can be used for subsequent lamination, reducing the processing steps for downstream enterprises (such as stator and rotor core manufacturers) and significantly improving the production efficiency of downstream products (such as stator and rotor cores).

[0042] Next, a detailed description will be given of step 1, "preparing single-layer cold-rolled coils with a width of 800-1300 mm and a thickness of 0.20-0.50 mm through steelmaking, billet casting, hot rolling, pickling, and cold rolling".

[0043] The steelmaking and billet casting processes can both be carried out using existing known technologies. It is understood that the chemical composition of the molten steel and the cast billet are consistent with the chemical composition of the single-layer cold-rolled coil.

[0044] Preferably, in step 1, the hot rolling includes sequential slab heating, rough rolling, finish rolling, and coiling. The slab heating temperature is 1090–1130℃, and the heating time is 150–200 min. The initial rolling temperature of the finish rolling is 900℃–980℃, the final rolling temperature is 840℃–880℃, and the coiling temperature is 580℃–680℃. Rough rolling may include 6 passes, resulting in an intermediate slab with a thickness of 30–40 mm. Finish rolling may include 7 passes, resulting in a hot-rolled plate with a thickness of 1.5–3.0 mm and a width of 800–1300 mm.

[0045] In addition, the pickling in step 1 can be carried out using existing known techniques.

[0046] In step 1, the steel structure after pickling and before cold rolling is a fully recrystallized structure. Specifically, in one embodiment of step 1, normalizing is performed between hot rolling and pickling at a temperature of 850–950°C for 150–200 seconds. In another embodiment, normalizing is not performed between hot rolling and pickling.

[0047] Furthermore, the wedge shape of steel after pickling and before cold rolling should be ≤40μm, the convexity should be 30~50mm, the camber should not exceed 3mm / m, and the waviness should not exceed 20mm / m.

[0048] Furthermore, in step 1, the cold rolling is carried out using an acid continuous rolling mill or a single-stand rolling mill. Here, the acid continuous rolling mill is, for example, a five-stand six-high rolling mill or a six-stand six-high rolling mill; the single-stand rolling mill is, for example, a six-high single-stand rolling mill, a sixteen-high single-stand rolling mill, or a twenty-high single-stand rolling mill.

[0049] Preferably, in step 1, the work roll roughness of the cold rolling mill (e.g., the aforementioned pickling mill or single-stand mill) is 3.0–5.0 μm, and the surface roughness of the single-layer cold-rolled coil obtained in step 1 is 1.0–1.5 μm. Thus, combined with the work roll roughness of the single-stand mill in step 3 described later, the overall rolling process of the laminated body in step 3 can be smoothly controlled, preventing interlayer slippage, reducing production difficulty, and improving production efficiency.

[0050] In addition, the steel before cold rolling (that is, before entering the acid continuous rolling mill or single-stand rolling mill) is trimmed; furthermore, in the "single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm" obtained in step 1, the width adopts a positive deviation of 0-3 mm and the thickness tolerance is ±0.01 mm.

[0051] Furthermore, in step 1, the thickness of the obtained single-layer cold-rolled coil is the minimum rollable thickness of the rolling mill used for cold rolling (e.g., the acid continuous rolling mill or single-stand rolling mill mentioned above).

[0052] Next, a detailed description will be given of step 2, "Laying two single-layer cold-hardened rolls of the same thickness and width together, and separating the two single-layer cold-hardened rolls by a high-temperature resistant insulating coating to form a laminate".

[0053] It is understood that both of the single-layer cold-hardened rolls are prepared by step 1.

[0054] Preferably, in addition to satisfying the foregoing, the chemical composition of each single-layer cold-rolled roll may also include: Sn: 0.01-0.1%, or Sb: 0.01-0.1%, or Sn+Sb: 0.01-0.1%.

[0055] The difference in Sn content and the difference in Sb content between the two single-layer cold-rolled coils do not exceed 0.02%.

[0056] Corresponding to the chemical composition of the single-layer cold-rolled coil, the chemical composition of the two-layer silicon steel sheet of the resulting non-oriented silicon steel product, by mass percentage, also includes: Sn: 0.01-0.1%, or Sb: 0.01-0.1%, or Sn+Sb: 0.01-0.1%; the difference in Sn content and the difference in Sb content between the two layers of silicon steel sheet do not exceed 0.02%.

[0057] More preferably, the chemical composition of each single-layer cold-rolled coil, by mass percentage, further includes: Cu: 0.10–1.00%.

[0058] The difference in Cu content between the two single-layer cold-rolled coils does not exceed 0.20%.

[0059] Corresponding to the chemical composition of the single-layer cold-rolled coil, the chemical composition of the resulting non-oriented silicon steel finished product, consisting of two layers of silicon steel sheets, also includes, by mass percentage: Cu: 0.10–1.00%; the difference in Cu content between the two layers of silicon steel sheets does not exceed 0.20%.

[0060] Of course, the chemical composition of each single-layer cold-rolled coil is based on the steelmaking process described in step 1. For example, in the steelmaking process described in step 1, at least one of Sb and Sn, as well as Cu, can be added so that the chemical composition of the single-layer cold-rolled coil can include Sn: 0.01-0.1% or Sb: 0.01-0.1% or Sn+Sb: 0.01-0.1%, and Cu: 0.10-1.00%. Alternatively, in the steelmaking process described in step 1, only at least one of Sb and Sn can be added without adding Cu. Alternatively, in the steelmaking process described in step 1, only Cu can be added without adding at least one of Sb and Sn.

[0061] Furthermore, in step 2, before stacking the two single-layer cold-hardened coils, a high-temperature resistant insulating coating is applied to the contact surfaces of the two single-layer cold-hardened coils (i.e., the surfaces that come into contact with each other when forming the laminate) to prevent electrical conduction and short circuits between the two layers of silicon steel sheets in the subsequent non-oriented silicon steel finished product during application (e.g., when making stator and rotor cores).

[0062] Preferably, the high-temperature resistant insulating coating is a silicon steel magnesium oxide coating or a magnesium silicate coating, which can withstand a high temperature of 1000℃.

[0063] Next, a detailed description will be given of step 3, "rolling the laminated body in 2 to 3 passes on a single-stand rolling mill with a total reduction rate of 30% to 50% to obtain a double-layer cold-rolled coil with a total thickness of 0.20 to 0.50 mm".

[0064] It is understandable that the total thickness of the double-layer cold-hardened coil obtained in this step is the same as the total thickness of the final non-oriented silicon steel product. Of course, given the coating treatment in step 4, the total thickness of the final non-oriented silicon steel product is slightly larger than the total thickness of the double-layer cold-hardened coil obtained in step 3 (due to the increased thickness of the two coating layers, for example, twice the thickness of a single coating layer of 0.5 to 5 μm). However, since the thickness of the coating is very small relative to the total thickness of the double-layer cold-hardened coil, the total thickness of the double-layer cold-hardened coil obtained in step 3 can be regarded as the total thickness of the final non-oriented silicon steel product.

[0065] Furthermore, in step 3, the surface roughness of the work rolls of the single-stand mill is 0.3–0.6 μm. Thus, combined with the surface roughness of the work rolls of the cold rolling mill mentioned in step 1 and the surface roughness of the single-layer cold-rolled coil obtained in step 1, the smooth progress of the laminate rolling in step 3 can be controlled as a whole, avoiding interlayer slippage, reducing production difficulty, and improving production efficiency.

[0066] In this step 3, the single-stand mill can be, for example, a six-roll single-stand mill, a sixteen-roll single-stand mill, or a twenty-roll single-stand mill.

[0067] Next, we will provide a detailed introduction to step 4, "the obtained double-layer cold-hardened coil is subjected to continuous annealing, coating and finishing to obtain non-oriented silicon steel finished products".

[0068] In step 4, the continuous annealing process involves an annealing temperature of 850–1000℃ and a holding time of 30–60 seconds. This ensures that the steel sheet undergoes sufficient recrystallization after continuous annealing, guaranteeing the microstructure and properties of the final non-oriented silicon steel product.

[0069] Furthermore, in the coating process described in step 4, a high-temperature resistant insulating coating is applied to both the upper and lower surfaces of the continuously annealed steel. This high-temperature resistant insulating coating is either a magnesium oxide coating or a magnesium silicate coating for silicon steel, which can withstand temperatures up to 1000℃. Thus, the upper and lower surfaces of the final non-oriented silicon steel product, as well as the contact surface between its two silicon steel layers, are all coated with a high-temperature resistant insulating coating. Consequently, the resulting non-oriented silicon steel product can be directly used by downstream enterprises for lamination to manufacture stators and rotor cores for various motors and generators, resulting in high production efficiency.

[0070] Furthermore, one embodiment of the present invention provides a wide strip of non-oriented silicon steel prepared by the aforementioned preparation method, namely the non-oriented silicon steel finished product obtained in step 4 above.

[0071] Specifically, the wide-band steel sheet comprises two layers of silicon steel sheets stacked together, the total thickness of the wide-band steel sheet being 0.20–0.50 mm, and the thickness of each silicon steel sheet being half the total thickness of the wide-band steel sheet; furthermore, the contact surface of the two silicon steel sheets has a high-temperature resistant insulating coating; the chemical composition of each silicon steel sheet, by mass percentage, is: C ≤ 0.003%, S ≤ 0.003%, Si: 0.50–3.40%, Al: 0.10–1%. The composition is as follows: 0.00%, Mn: 0.20~1.00%, P: 0.005~0.04%, Nb≤0.004%, V≤0.004%, Ti≤0.004%, Ni≤0.03%, Cr≤0.03%, N≤0.004%, with the remainder being Fe and unavoidable impurities; furthermore, the differences in Si content, Al content, and Mn content between the two silicon steel plates do not exceed 0.20%, and the difference in P content does not exceed 0.02%.

[0072] Furthermore, based on the aforementioned preparation method, it is known that the width of the wide strip steel sheet is not less than the width of the single-layer cold-rolled coil in step 1 above, which is 800-1300 mm.

[0073] More preferably, the chemical composition of each silicon steel sheet, by mass percentage, further includes: Sn: 0.01–0.1%, or Sb: 0.01–0.1%, or Sn+Sb: 0.01–0.1%; the difference in Sn content and the difference in Sb content between the two silicon steel sheets do not exceed 0.02%; and / or, the chemical composition of each silicon steel sheet, by mass percentage, further includes: Cu: 0.10–1.00%; the difference in Cu content between the two silicon steel sheets does not exceed 0.20%.

[0074] In summary, the beneficial effects of one embodiment of the present invention are as follows: by laminating, rolling, annealing, coating, and finishing a single-layer cold-rolled coil with a width of 800-1300 mm and a thickness of 0.20-0.50 mm, a double-layer non-oriented silicon steel product is obtained, with each layer of silicon steel sheet having a thickness of 0.10-0.25 mm. On the one hand, this solves the problem of limited minimum rollable thickness in wide strip steel rolling, realizing the cold rolling of wide strip steel and thin specifications of non-oriented silicon steel. The two layers of silicon steel sheets have similar compositions, making rolling easier and ensuring microstructure and properties. Furthermore, the simultaneous annealing of the two layers of silicon steel sheets significantly improves production efficiency. On the other hand, the obtained double-layer non-oriented silicon steel product can be used for subsequent lamination, reducing the processing steps for downstream enterprises (such as stator and rotor core manufacturers) and significantly improving the production efficiency of downstream products (such as stator and rotor cores).

[0075] The following are several specific embodiments implemented based on one embodiment of the present invention, and the implementation process of these embodiments is as follows:

[0076] (1) Steelmaking: The chemical composition of the molten steel for each furnace number is shown in Table 1. The molten steel obtained is continuously cast into a 220mm thick continuous casting billet.

[0077] Table 1 Chemical composition of molten steel for each heat number

[0078]

[0079]

[0080] (2) The continuous casting billets of heat numbers 1 to 4 are hot-rolled, pickled without normalization, and cold-rolled to prepare single-layer cold-rolled coils numbered 1 to 4 as shown in Table 2; the continuous casting billets of heat numbers 5 to 10 are hot-rolled, normalized, pickled, and cold-rolled to prepare single-layer cold-rolled coils numbered 5 to 10 as shown in Table 2; wherein, the steel heat number, key parameters of hot rolling and normalization, width and thickness of the single-layer cold-rolled coils corresponding to each number are shown in Table 1.

[0081] Table 2. Key parameters of each single-layer steel coil during the manufacturing process.

[0082]

[0083] (3) Single-layer cold-hardened roll 1 and single-layer cold-hardened roll 2 with the same thickness and width are stacked and separated by a high-temperature resistant insulating coating to form a laminate; wherein, the numbers of the single-layer cold-hardened roll 1 and single-layer cold-hardened roll 2 contained in the laminate of each embodiment are shown in Table 3.

[0084] Table 3 Key parameters of the rolling and annealing processes in each embodiment

[0085]

[0086] (4) The laminates of each embodiment are rolled in 2 to 3 passes on a single stand rolling mill with a total reduction of 30% to 50% to obtain a double-layer cold-hardened coil; the obtained double-layer cold-hardened coil is continuously annealed, coated and finished to obtain a non-oriented silicon steel finished product.

[0087] The surface roughness of the work rolls, number of rolling passes, annealing temperature, holding time, and total thickness of the non-oriented silicon steel finished product of the single-stand rolling mill used in the rolling of the laminate are shown in Table 3.

[0088] Samples were taken from the two layers of non-oriented silicon steel sheets obtained in the above embodiments, and the iron loss and magnetic induction intensity were tested according to GB / T3655 standard, as shown in Table 4. It can be seen that, due to the single-layer silicon steel sheet thickness of only 0.10–0.25 mm in the embodiments, the magnetic properties are excellent.

[0089] Table 4 Magnetic properties of each embodiment

[0090] Serial Number Total thickness of finished product / mm Single-layer steel plate thickness / mm <![CDATA[P 1.0 / 400 (W / kg)]]> <![CDATA[B 5000 / T]]> Example 1 0.50 0.25 19.8 1.705 Example 2 0.35 0.175 17.5 1.693 Example 3 0.30 0.15 14.3 1.685 Example 4 0.30 0.15 12.9 1.673 Example 5 0.20 0.10 9.8 1.659

[0091] In addition, the non-oriented silicon steel products obtained in each embodiment are directly double-layered and simultaneously laminated to manufacture stator and rotor cores, and the performance of the resulting stator and rotor cores meets the requirements.

[0092] In summary, this invention can produce wide strip steel sheets of non-oriented silicon steel with high production efficiency and low cost. Furthermore, the obtained wide strip steel sheets of non-oriented silicon steel can be directly used in the form of double-layer finished products to manufacture stator and rotor cores of various motors and generators, thereby improving the production efficiency of stator and rotor cores.

Claims

1. A method for preparing a wide strip of non-oriented silicon steel, characterized in that, include: Two single-layer cold-rolled coils with a width of 800~1300mm and a thickness of 0.20~0.50mm are prepared by steelmaking, billet casting, hot rolling, pickling, and cold rolling; normalization may or may not be performed between the hot rolling and pickling processes; wherein, the hot rolling includes sequential billet heating, rough rolling, finish rolling, and coiling, with the initial rolling temperature of finish rolling being 900℃~980℃, the final rolling temperature being 840℃~880℃, and the coiling temperature being 580℃~680℃; Two single-layer cold-cured rolls of the same thickness and width are stacked together, and the two single-layer cold-cured rolls are separated by a high-temperature resistant insulating coating to form a laminate. The chemical composition of the two single-layer cold-cured rolls, by mass percentage, is as follows: C≤0.003%, S≤0.003%, Si:0.50~3.40%, Al:0.10~1.00%, Mn:0.20~1.00%, P:0.005~0.04%, Nb≤0.004%, V≤0.004%, Ti≤0.004%, Ni≤0.03%, Cr≤0.03%, N≤0.004%, with the remainder being Fe and unavoidable impurities. Furthermore, the difference in Si content, Al content, and Mn content between the two single-layer cold-cured rolls does not exceed 0.20%, and the difference in P content does not exceed 0.02%. The laminate is rolled in 2 to 3 passes on a single-stand rolling mill with a total reduction of 30% to 50% to obtain a double-layer cold-rolled coil with a total thickness of 0.20 to 0.50 mm. The resulting double-layer cold-hardened coil is subjected to continuous annealing, coating and finishing to obtain a non-oriented silicon steel finished product, which has a double-layer silicon steel sheet arranged in a stacked manner.

2. The method for preparing wide strip steel of non-oriented silicon steel according to claim 1, characterized in that, The chemical composition of both single-layer cold-rolled coils further includes, by mass percentage: Sn: 0.01-0.1%, or Sb: 0.01-0.1%, or Sn+Sb: 0.01-0.1%.

3. The method for preparing wide strip steel of non-oriented silicon steel according to claim 2, characterized in that, The chemical composition of both single-layer cold-rolled coils, by mass percentage, also includes: Cu: 0.10–1.00%.

4. The method for preparing wide strip steel of non-oriented silicon steel according to claim 3, characterized in that, The difference in Sn content and Sb content between the two single-layer cold-rolled coils does not exceed 0.02%, and the difference in Cu content does not exceed 0.20%.

5. The method for preparing wide strip steel of non-oriented silicon steel according to claim 1, characterized in that, In the process of "preparing two single-layer cold-rolled coils with a width of 800~1300mm and a thickness of 0.20~0.50mm through steelmaking, billet casting, hot rolling, pickling, and cold rolling", the microstructure of the steel after pickling and before cold rolling is a fully recrystallized microstructure.

6. The method for preparing wide strip steel sheet of non-oriented silicon steel according to claim 1, characterized in that, In the billet heating process, the billet heating temperature is 1090~1130℃ and the heating time is 150~200min.

7. The method for preparing wide strip steel of non-oriented silicon steel according to claim 1 or 6, characterized in that, When normalization occurs between the hot rolling and pickling processes, the normalization temperature is 850~950℃ and the holding time is 150~200s.

8. The method for preparing wide strip steel sheet of non-oriented silicon steel according to claim 7, characterized in that, In the continuous annealing process, the annealing temperature is 850~1000℃ and the holding time is 30~60s.

9. The method for preparing wide strip steel sheet of non-oriented silicon steel according to claim 1, characterized in that, In the phrase "two single-layer cold-rolled coils with a width of 800~1300mm and a thickness of 0.20~0.50mm are prepared by steelmaking, billet casting, hot rolling, pickling, and cold rolling", the work roll roughness of the cold rolling mill is 3.0~5.0µm, and the surface roughness of the single-layer cold-rolled coil is 1.0~1.5μm. In the phrase "the laminate is rolled in 2 to 3 passes on a single-stand mill with a total reduction of 30% to 50% to obtain a double-layer cold-rolled coil with a total thickness of 0.20 to 0.50 mm", the roughness of the work rolls of the single-stand mill is 0.3 to 0.6 μm.

10. The method for preparing wide strip steel of non-oriented silicon steel according to claim 1, characterized in that, In the process of "preparing two single-layer cold-rolled coils with a width of 800~1300mm and a thickness of 0.20~0.50mm by steelmaking, billet casting, hot rolling, pickling, and cold rolling", the thickness of the obtained single-layer cold-rolled coil is the minimum rollable thickness of the rolling mill used for cold rolling.

11. A wide strip steel sheet of non-oriented silicon steel, characterized in that, It includes a double layer of silicon steel plates stacked together, wherein the total thickness of the wide steel sheet is 0.20~0.50mm, and the thickness of each silicon steel plate is half the total thickness of the wide steel sheet; and the contact surface of the two silicon steel plates has a high-temperature resistant insulating coating. The chemical composition of each layer of silicon steel sheet, by mass percentage, is as follows: C≤0.003%, S≤0.003%, Si:0.50~3.40%, Al:0.10~1.00%, Mn:0.20~1.00%, P:0.005~0.04%, Nb≤0.004%, V≤0.004%, Ti≤0.004%, Ni≤0.03%, Cr≤0.03%, N≤0.004%, with the remainder being Fe and unavoidable impurities; Furthermore, the differences in Si content, Al content, and Mn content between the two silicon steel plates do not exceed 0.20%, and the difference in P content does not exceed 0.02%. The method for preparing the wide strip steel sheet includes: preparing two single-layer cold-rolled coils with a width of 800~1300mm and a thickness of 0.20~0.50mm by steelmaking, billet casting, hot rolling, pickling, and cold rolling; stacking the two single-layer cold-rolled coils and separating them with a high-temperature resistant insulating coating to form a laminate; rolling the laminate in 2~3 passes on a single-stand rolling mill with a total reduction of 30%~50% to obtain a double-layer cold-rolled coil; The resulting double-layer cold-rolled coil is subjected to continuous annealing, coating and finishing to obtain the wide strip steel sheet; The hot rolling and pickling processes may or may not involve normalization; the hot rolling includes sequential billet heating, rough rolling, finish rolling and coiling, with the finish rolling starting temperature at 900℃~980℃, the finishing rolling temperature at 840℃~880℃, and the coiling temperature at 580℃~680℃.

12. The wide strip steel sheet of non-oriented silicon steel according to claim 11, characterized in that, The chemical composition of each layer of silicon steel sheet, by mass percentage, also includes: Sn: 0.01–0.1%, or Sb: 0.01–0.1%, or Sn+Sb: 0.01–0.1%; The difference in Sn content and the difference in Sb content between the two layers of silicon steel plates do not exceed 0.02%.

13. The wide strip steel sheet of non-oriented silicon steel according to claim 11, characterized in that, The chemical composition of each layer of silicon steel sheet, by mass percentage, also includes: Cu: 0.10–1.00%; The difference in Cu content between the two layers of silicon steel plates shall not exceed 0.20%.

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