Ultra-thin non-oriented silicon steel for stator core and rotor core of motor, and production method therefor

Abstract

Disclosed in the present invention are an ultra-thin non-oriented silicon steel for a stator core and a rotor core of a motor, and a production method therefor. The thickness of the non-oriented silicon steel is 0.15-0.25 mm, and the non-oriented silicon steel comprises the following chemical components in percentage by mass: C≤0.0020%, S≤0.0010%, Si: 3.25-3.55%, Al: 0.55-0.85%, Mn: 0.25-0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the balance being Fe and inevitable impurities. The average grain size of the non-oriented silicon steel is 50 μm or less, the iron loss P 1.0 / 400 is less than or equal to 15.0 W / kg, the magnetic induction intensity B 5000 is greater than or equal to 1.63 T, the yield strength is greater than or equal to 500 MPa, the tensile strength is greater than or equal to 600 MPa, and the elongation is greater than or equal to 15%. The present invention can meet the application requirements of both a stator core and a rotor core, so that the manufacturing cost of a motor is greatly reduced, and the waste of materials is avoided.

Description

Ultra-thin non-oriented silicon steel for motor stator and rotor cores and its production method Technical Field

[0001] This invention belongs to the field of steel material preparation technology, and relates to a non-oriented silicon steel and its production method, especially an ultra-thin non-oriented silicon steel for motor stator and rotor cores and its production method. Background Technology

[0002] The drive motor is one of the three core components of an electric vehicle. Its driving characteristics directly determine the vehicle's main performance indicators such as hill climbing, acceleration, and top speed, making it a crucial component. Electric vehicle drive motors operate based on electromagnetic induction, utilizing a rotating magnetic field generated by the stator to act on the rotor, creating magnetoelectric power that propels the electric vehicle.

[0003] Non-oriented silicon steel is an important material used to manufacture the core components of motors—the stator and rotor cores, and iron loss is one of the important magnetic property parameters of non-oriented silicon steel.

[0004] Based on research, the two main ways to reduce iron loss are: increasing the resistivity of the steel plate and decreasing its thickness. Increasing the Si and Al content in non-oriented silicon steel can increase the resistivity of the steel plate, thereby reducing iron loss. However, as the Si and Al content increases, the rollability of the steel plate decreases, which is detrimental to smooth production. Therefore, this method of reducing iron loss by increasing Si and Al content has certain limitations. Reducing the thickness of the steel plate not only directly reduces iron loss but also increases its resistivity, thus indirectly reducing iron loss. Therefore, as the speed and frequency of motors increase, reducing the thickness of the non-oriented silicon steel is the most effective method to reduce iron loss.

[0005] In particular, given the higher requirements for magnetic properties of stator cores, reducing iron loss by decreasing the thickness of the steel plate is an important research direction for non-oriented silicon steel used in stator cores.

[0006] Furthermore, in drive motors, as speed and frequency increase, the rotor core requires higher structural strength to overcome the challenge of high centrifugal forces. To ensure structural strength, the rotor core must be made of relatively thick non-oriented silicon steel or non-oriented silicon steel with higher mechanical strength.

[0007] Clearly, in terms of thickness, the rotor core and stator core have different requirements for the thickness of non-oriented silicon steel. The rotor core requires a thicker steel plate due to structural strength requirements, while the stator core requires a thinner steel plate due to iron loss requirements.

[0008] On the other hand, the high mechanical strength required for rotor cores is usually achieved through solid solution strengthening, precipitation strengthening, dislocation strengthening, and grain refinement strengthening. For example: 1. Adding a large amount of alloying elements, such as Cu, Cr, Ni, Nb, V, Ti, etc. to the composition; 2. Using incomplete recrystallization annealing or secondary cold rolling in the process. However, these methods will destroy the magnetic properties and cause the iron loss of the steel plate to increase.

[0009] For the reasons mentioned above, current technologies for manufacturing high-speed drive motors for electric vehicles generally require separate non-oriented silicon steel sheets for the rotor and stator cores. Specifically, a thin non-oriented silicon steel sheet is used to prepare the stator core, while a thicker sheet or a thin sheet with poor magnetic properties is used to prepare the rotor core. This not only increases the manufacturing cost of the motor but also results in a significant waste of non-oriented silicon steel materials.

[0010] To date, there has never been a product in the field of non-oriented silicon steel that can simultaneously meet the application requirements of both stator cores and rotor cores. Summary of the Invention

[0011] To address the technical problem that existing non-oriented silicon steel cannot simultaneously meet the application requirements of stator cores and rotor cores, the present invention aims to provide a non-oriented silicon steel and its production method, particularly an ultra-thin non-oriented silicon steel for motor stator and rotor cores and its production method.

[0012] To address the technical problem of not being able to use the same non-oriented silicon steel sheet to produce stator and rotor cores, the present invention also aims to provide a motor core and a method for manufacturing a stator and rotor core for a motor.

[0013] To achieve the above-mentioned objective, one embodiment of the present invention provides a non-oriented silicon steel. The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions.

[0014] The non-oriented silicon steel is a steel plate with a thickness of 0.15~0.25mm, an average grain size of less than 50μm, and an iron loss P. 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%.

[0015] Preferably, the non-oriented silicon steel is a steel plate with a thickness of 0.25 mm, and its iron loss P 1.0 / 400 ≤15.0W / kg; or, the non-oriented silicon steel is a steel plate with a thickness of 0.20mm, and its iron loss P 1.0 / 400 ≤14.0W / kg; or, the non-oriented silicon steel is a steel plate with a thickness of 0.15mm, and its iron loss P 1.0 / 400 ≤13.0W / kg.

[0016] Preferably, after secondary annealing, the non-oriented silicon steel has an average grain size of 80-150 μm and an iron loss P0.05 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T;

[0017] During annealing: the heating rate is ≤5℃ / min, the annealing temperature is 980~1000℃, and the holding time is 90~120min.

[0018] Preferably, the chemical composition of the non-oriented silicon steel, by mass percentage, also satisfies: a total of 4.35-4.55% Si, Al, and Mn.

[0019] Preferably, the non-oriented silicon steel is prepared by steelmaking, continuous casting, hot rolling, normalizing, pickling, one cold rolling and one annealing; wherein, the average grain size of the recrystallized steel plate obtained by normalizing is ≤50μm;

[0020] The average grain size of the non-oriented silicon steel is 30~50μm.

[0021] To achieve the above-mentioned objective, one embodiment of the present invention provides a method for manufacturing a stator and rotor core for an electric motor. The manufacturing method uses the aforementioned non-oriented silicon steel and includes:

[0022] Stamping: The non-oriented silicon steel is stamped to obtain a series of rotor sheets and stator sheets;

[0023] Rotor core fabrication: A series of rotor laminations are assembled into a rotor core through lamination and pressing.

[0024] Stator core preparation: First, a series of stator sheets are assembled into stator core laminations by lamination and pressing, and then a second annealing is performed to obtain the stator core; or, a series of stator sheets are first annealed twice, and then assembled into stator cores by lamination and pressing.

[0025] During the secondary annealing: the heating rate is ≤5℃ / min, the annealing temperature is 980~1000℃, and the holding time is 90~120min.

[0026] Preferably, in the stamping process: a pair of rotor sheets and stator sheets are stamped out from the non-oriented silicon steel in a concentric distribution.

[0027] To achieve the above-mentioned objective, one embodiment of the present invention provides an iron core for an electric motor. The iron core for the electric motor includes a laminated rotor core and a laminated stator core;

[0028] Both the laminated rotor core and the laminated stator core are made of non-oriented silicon steel with a thickness of 0.15~0.25mm, and the chemical composition, by mass percentage, includes: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions.

[0029] The average grain size of the non-oriented silicon steel sheets in the laminated rotor core is 30~50μm, and the iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%;

[0030] The average grain size of the non-oriented silicon steel sheets in the laminated stator core is 80~150μm, and the iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0031] To achieve the above-mentioned objective, one embodiment of the present invention provides a method for producing non-oriented silicon steel. The production method includes:

[0032] Steelmaking: Refining molten steel and casting it into steel billets with a thickness of 200~240mm. After leaving the continuous casting machine, the steel billets are held at a temperature of 600~900℃ for 3~8h. The chemical composition of the steel billets, by mass percentage, includes: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions.

[0033] Hot rolling: After heating the steel billet to 1080~1120℃ and holding it at that temperature for 150~200min, it is first rough rolled to obtain an intermediate billet with a thickness of 35~45mm, and then finished rolled and coiled to obtain a hot rolled coil with a thickness of 1.80~2.20mm; wherein, the initial rolling temperature of the finish rolling is 950±20℃, the final rolling temperature is 820±20℃, and the coiling temperature is 600±20℃;

[0034] Cold rolling: Hot-rolled coils are sequentially normalized, pickled, and cold-rolled once to obtain cold-rolled strip steel with a thickness of 0.15~0.25mm; wherein, the normalizing temperature is 800~820℃ and held for 180~200s, and the total reduction rate of the first cold rolling is 90±2%;

[0035] Single annealing: After the cold-rolled strip steel is annealed, cooled and coated once, the finished steel plate is obtained; the annealing temperature is 850~900℃ and held for 60~90s.

[0036] Preferably, in a single annealing process, the average grain size of the resulting steel plate is 30~50μm.

[0037] Preferably, in the cold rolling process: the proportion of recrystallized grains in the normalized steel sheet is 50-60%, and the average grain size of the recrystallized grains is ≤50μm.

[0038] Preferably, the production method further includes,

[0039] Stamping: The finished steel plate is stamped to obtain a series of thin sheets;

[0040] Secondary annealing: First, stack and press a series of thin sheets, then perform secondary annealing; or, first, perform secondary annealing on a series of thin sheets, then stack and press them; wherein, during secondary annealing: heating rate ≤ 5℃ / min, annealing temperature 980~1000℃, holding time 90~120min.

[0041] Preferably, in the secondary annealing process: after the heat preservation is completed, the cooling rate is controlled to be ≤3℃ / min.

[0042] Preferably, in the stamping process: a series of pairs of rotor and stator sheets are stamped from the finished steel plate, each pair of rotor and stator sheets being concentrically distributed; the stator sheets then enter the secondary annealing process.

[0043] The production method also includes a rotor core preparation process: a series of rotor laminations are assembled into a rotor core by lamination pressing.

[0044] Preferably, after secondary annealing, the average grain size of the non-oriented silicon steel is 80~150μm.

[0045] Preferably, in the hot rolling process: the steel billet is sent into a heating furnace for heating, with an entry temperature ≥500℃, a preheating temperature of 950~1000℃, a heating and homogenization temperature of 1080~1120℃, and a total heating and homogenization time of 150~200min.

[0046] Preferably, in the cold rolling process: except for the last pass, the reduction rate of each of the remaining passes in a single cold rolling process is more than 30%.

[0047] Preferably, in one annealing process: the annealing temperature is 850~870℃ and the holding time is 80~90s.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows: the same non-oriented silicon steel sheet can simultaneously meet the needs of both the stator core and the rotor core for cold-rolled and one-time annealed non-oriented silicon steel sheets. Compared with the conventional technology where the cold-rolled and one-time annealed non-oriented silicon steel sheets used for the stator core and the rotor core must be prepared separately, this invention not only greatly reduces the manufacturing cost of the motor and its stator and rotor cores, but also greatly realizes the full utilization of non-oriented silicon steel materials. For example, in one area of ​​the steel sheet, the outer periphery forms the annular sheet of the stator core, and the center forms the sheet of the rotor core, thereby avoiding material waste. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0050] First Implementation Method

[0051] One embodiment of the present invention provides an ultra-thin non-oriented silicon steel that can meet the requirements of both rotor cores and stator cores for base material, thus satisfying the requirements of stator cores.

[0052] The chemical composition of the non-oriented silicon steel, by mass percentage, includes: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions.

[0053] The role of each chemical element in this embodiment will be described in detail below.

[0054] Si and Al: Si and Al can increase the resistivity of steel plates, thereby reducing iron loss. In addition, Si and Al can improve the strength of steel plates. However, an increase in Si and Al content will cause difficulties in cold rolling. In one embodiment of this application, the Si content is controlled between 3.25% and 3.55%, and the Al content is controlled between 0.55% and 0.85%.

[0055] Mn: Mn can improve the microstructure and texture of hot-rolled plates, promote the strengthening of (100) and (110) components and weaken the (111) component, which is beneficial to improving magnetic properties; in addition, Mn easily forms MnS with S, and coarse MnS is conducive to grain growth and reducing iron loss; in addition, Mn can also improve the strength of steel plates; in one embodiment of this application, the Mn content is controlled between 0.25 and 0.55%.

[0056] Nb, V, Ti, Cr, Ni, Cu: Adding Nb, V, Ti, Cr, Ni, and Cu to non-oriented silicon steel can improve its strength, but it will also lead to increased iron loss and decreased magnetic induction. In one embodiment of this application, Nb ≤ 0.003%, V ≤ 0.003%, Ti ≤ 0.003%, Cr ≤ 0.02%, Ni ≤ 0.02%, and Cu ≤ 0.02%.

[0057] C, S, N: C, S, and N are all harmful elements in non-oriented silicon steel, which will lead to increased iron loss and reduced magnetic induction intensity. In order to meet the requirements of low iron loss and high magnetic induction intensity for ultra-thin non-oriented silicon steel used in the stator core of high-speed drive motor of electric vehicle, in one embodiment of this application, C≤0.0020%, S≤0.0010%, and N≤0.0020% are controlled.

[0058] P: P is a residual element, which is detrimental to magnetic properties and also causes difficulties in cold rolling. In one embodiment of this application, P is controlled to be ≤0.015%.

[0059] Furthermore, regarding the content of Nb, V, Ti, Cr, Ni, and Cu in this embodiment: Specifically, in one embodiment, during the steelmaking process, alloying elements such as Nb, V, Ti, Cr, Ni, and Cu may not be intentionally added, and these elements can exist as impurity elements in the molten steel, only needing to satisfy Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, and Cu≤0.02%. In this case, the content of any one or more of Nb, V, Ti, Cr, Ni, and Cu may be 0. Alternatively, in another embodiment, during the steelmaking process, any one or more of alloying elements such as Nb, V, Ti, Cr, Ni, and Cu may be added, and satisfying Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, and Cu≤0.02%. In this case, the content of any one or more of Nb, V, Ti, Cr, Ni, and Cu is not 0.

[0060] The non-oriented silicon steel is a steel plate with a thickness of 0.15~0.25mm. Thus, this ultra-thin non-oriented silicon steel not only directly reduces iron loss, but also increases the resistivity of the steel plate, thereby indirectly reducing iron loss. Therefore, the non-oriented silicon steel of this embodiment has low iron loss.

[0061] Furthermore, the non-oriented silicon steel is prepared through steelmaking, continuous casting, hot rolling, normalizing, pickling, one cold rolling, and one annealing. The normalized steel plate has a recrystallized grain ratio of 50-60%, with an average recrystallized grain size ≤50μm. By controlling the recrystallized grain ratio and average grain size of the normalized steel plate, the average grain size of the non-oriented silicon steel is 30-50μm, which improves the rollability of the steel plate to a certain extent. This allows for a certain increase in the content of Si, Mn, and Al, thereby improving mechanical strength and reducing iron loss from a compositional perspective. Furthermore, considering the grain size and the content of Si, Al, and Mn, this not only meets the high mechanical performance requirements of the non-oriented silicon steel used in the rotor core of electric vehicle drive motors but also creates conditions for the preparation of the stator core of electric vehicle drive motors, especially laying the foundation for obtaining coarse grains after secondary annealing to further reduce iron loss.

[0062] In one embodiment of this application, the iron loss P of the non-oriented silicon steel 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%.

[0063] Based on the above settings and controls regarding chemical composition, thickness, grain size, and properties (including magnetic and mechanical properties), the non-oriented silicon steel of one embodiment of this application can not only meet the requirements of rotor cores for low iron loss, high magnetic induction intensity, and high strength without requiring a large amount of alloying elements, that is, the non-oriented silicon steel can be used to prepare rotor cores, for example, by stamping or laminating to obtain laminated rotor cores, and the resulting rotor cores have the properties of low iron loss, high magnetic induction intensity, and high strength; at the same time, the non-oriented silicon steel can also meet the requirements of stator cores for base material, that is, the non-oriented silicon steel can be used to prepare stator cores, for example, by stamping, laminating and then annealing, or annealing and then laminating to obtain laminated stator cores, and the resulting stator cores have the properties of ultra-low iron loss and high magnetic induction intensity.

[0064] Therefore, the non-oriented silicon steel described in one embodiment of this application can be used as the base material for both the rotor core and the stator core, and can simultaneously meet the needs of both the stator core and the rotor core for cold-rolled and one-time annealed non-oriented silicon steel finished steel plates. Compared with the conventional technology where the cold-rolled and one-time annealed non-oriented silicon steel finished steel plates used for the stator core and the cold-rolled and one-time annealed non-oriented silicon steel finished steel plates used for the rotor core must be prepared separately, this not only greatly reduces the manufacturing cost of the motor and its stator and rotor cores, but also greatly realizes the full utilization of non-oriented silicon steel materials. For example, in one area of ​​the steel plate, the outer periphery forms the annular thin sheet of the stator core, and the center forms the thin sheet of the rotor core, thereby avoiding material waste.

[0065] Furthermore, in one embodiment of this application, the non-oriented silicon steel, based on its chemical composition, thickness, average grain size, and properties, after undergoing a second annealing treatment, has an average grain size of 80~150μm and an iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T. It can be seen that after secondary annealing, the average grain size of this non-oriented silicon steel can be greatly increased and the iron loss can be reduced, making it suitable as a stator core material.

[0066] In the secondary annealing process, the heating rate is ≤5℃ / min, the annealing temperature is 980~1000℃, and the holding time is 90~120min. Of course, the annealing process in this embodiment is not limited to this, and other feasible annealing conditions can also be used.

[0067] In a preferred embodiment, the chemical composition of the non-oriented silicon steel further satisfies the following condition: a total content of 4.35% to 4.55% for Si, Al, and Mn. Thus, by further controlling the total content of Si, Al, and Mn, mechanical strength and magnetic properties can be guaranteed, while rollability can also be enhanced.

[0068] Preferably, the average grain size of the non-oriented silicon steel can be controlled within 30~50μm. By controlling this average grain size, coarse grains can be obtained after the secondary annealing process to further reduce iron loss, thus enabling the non-oriented silicon steel to meet the application requirements of stator cores.

[0069] In addition, the microstructure of the non-oriented silicon steel is a fully recrystallized microstructure, that is, the proportion of recrystallized grains is 100%.

[0070] In addition, the yield strength of the non-oriented silicon steel is 500~550MPa and the tensile strength is 600~650MPa.

[0071] In one embodiment, the non-oriented silicon steel can specifically be a steel plate with a thickness of 0.25 mm, and its iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0072] Correspondingly, after the secondary annealing treatment, the 0.25mm thick non-oriented silicon steel sheet of this embodiment has a lower iron loss P. 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0073] Alternatively, in a variation, the non-oriented silicon steel may specifically be a steel plate with a thickness of 0.20 mm, whose iron loss P 1.0 / 400 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0074] Correspondingly, after the secondary annealing treatment, the 0.20mm thick non-oriented silicon steel sheet of this embodiment has a lower iron loss P. 1.0 / 400 ≤11.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0075] Alternatively, in a variation, the non-oriented silicon steel may specifically be a steel plate with a thickness of 0.15 mm, whose iron loss P 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0076] Correspondingly, after the secondary annealing treatment, the 0.15mm thick non-oriented silicon steel sheet of this embodiment has a lower iron loss P. 1.0 / 400 ≤10.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0077] Furthermore, this embodiment also provides a method for manufacturing a stator and rotor core for an electric motor, and more particularly a method for manufacturing a stator and rotor core for an electric vehicle drive motor.

[0078] The manufacturing method uses the non-oriented silicon steel described above to prepare the rotor core and stator core.

[0079] The manufacturing method includes processes such as stamping, rotor core preparation, and stator core preparation. These processes are described in detail below.

[0080] Stamping process: The non-oriented silicon steel is stamped to obtain a series of rotor sheets and stator sheets.

[0081] As mentioned earlier, the thickness of the non-oriented silicon steel is 0.15~0.25mm. Therefore, the thickness of each rotor sheet and stator sheet obtained in the stamping process is the same as the thickness of the non-oriented silicon steel, which is also between 0.15~0.25mm.

[0082] Rotor core manufacturing process: A series of rotor laminations are assembled into a rotor core by lamination and pressing.

[0083] In this way, a rotor core for an electric motor can be prepared, namely a laminated rotor core. In this laminated rotor core, the non-oriented silicon steel sheets exhibit low iron loss, high magnetic induction intensity, and high mechanical strength. Specifically, for example, the average grain size of the non-oriented silicon steel sheets is 30~50μm, and the iron loss P... 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%.

[0084] Stator core manufacturing process: First, a series of stator sheets are assembled into stator core laminations by lamination and pressing, and then a second annealing is performed to obtain the stator core; or, a series of stator sheets are first annealed twice, and then assembled into stator cores by lamination and pressing.

[0085] During the secondary annealing: the heating rate is ≤5℃ / min, the annealing temperature is 980~1000℃, and the holding time is 90~120min.

[0086] In this way, a stator core for motors can be prepared, namely a laminated stator core. In this laminated stator core, the non-oriented silicon steel sheets have lower iron loss and higher magnetic induction intensity. Specifically, for example, the average grain size of the non-oriented silicon steel sheets is 80~150μm, and the iron loss P... 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0087] Therefore, the manufacturing method described in one embodiment of this application can use the same non-oriented silicon steel sheet for stamping, and then prepare the rotor core and stator core. The rotor core has high strength and the stator core has low iron loss. Compared with the commonly used technology where the non-oriented silicon steel sheets of the stator core and rotor core cannot be derived from the same non-oriented silicon steel sheet, this method not only greatly reduces the manufacturing cost of the motor and its stator and rotor cores, but also greatly realizes the full utilization of non-oriented silicon steel materials and avoids material waste.

[0088] It is understood that the order of operations in the manufacturing method is not limited by the order in which they are described in the technical introduction. For example, although the "rotor core preparation process" is introduced first and the "stator core preparation process" is introduced later, the two processes can be performed simultaneously, or the rotor core preparation process can be performed first and then the stator core preparation process, or vice versa, and so on. Similarly, although the "stamping process" is introduced first and then the "rotor core preparation process" and "stator core preparation process," in practice, the "stamping process" can be performed entirely before the "rotor core preparation process" and "stator core preparation process," or it can be performed simultaneously with the "rotor core preparation process" and "stator core preparation process" (e.g., stamping while laminating). These changes in the order of implementation do not deviate from the technical purpose of this application.

[0089] In another embodiment, the secondary annealing of the stator core preparation process can be carried out using either a bell-type annealing furnace or a continuous annealing furnace, but is not limited to these methods.

[0090] Secondary annealing can be performed in a weakly reducing protective atmosphere, such as a protective atmosphere of N2 and H2, wherein the volume percentage of H2 is 20-30% and the remainder is N2.

[0091] Furthermore, in one embodiment, after the holding time for secondary annealing is completed in the stator core manufacturing process, the cooling rate can be controlled to be ≤3℃ / min. For example, in an embodiment of secondary annealing of stator core laminations, the stator core laminations can be cooled in an annealing furnace, and the cooling rate of the annealing furnace can be controlled to be ≤3℃ / min, so that the cooling rate of the stator core laminations is ≤3℃ / min; or, in an embodiment of secondary annealing of a series of stator sheets, these stator sheets can be cooled in an annealing furnace, and the cooling rate of the annealing furnace can be controlled to be ≤3℃ / min, so that the cooling rate of these stator sheets is ≤3℃ / min.

[0092] Furthermore, in one embodiment, the stamping process involves stamping a pair of rotor sheets and stator sheets from the non-oriented silicon steel in a concentrically distributed manner.

[0093] In other words, for every rotor sheet punched out from the non-oriented silicon steel around a center, a stator sheet surrounding the rotor sheet will also be punched out from the non-oriented silicon steel around that center (that is, the rotor sheet makes full use of the steel plate in the central area of ​​the annular stator sheet).

[0094] In this way, non-oriented silicon steel materials can be fully utilized, greatly improving the material utilization rate, avoiding material waste, and reducing the production cost of motors.

[0095] Furthermore, one embodiment of this application also provides an iron core for an electric motor, the iron core including a laminated rotor iron core and a laminated stator iron core.

[0096] The laminated rotor core and the laminated stator core can be made of the non-oriented silicon steel described above, and the specific preparation process can adopt the manufacturing method described above. Of course, this application is not limited to this.

[0097] Specifically, both the laminated rotor core and the laminated stator core are made of non-oriented silicon steel with a thickness of 0.15~0.25mm, and the chemical composition, by mass percentage, includes: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions.

[0098] That is, the chemical composition of the non-oriented silicon steel sheets of the laminated rotor core satisfies the following by mass percentage: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions.

[0099] Meanwhile, the chemical composition of the non-oriented silicon steel sheet of the laminated stator core also meets the following requirements by mass percentage: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions.

[0100] Preferably, the non-oriented silicon steel sheets of the laminated rotor core and the non-oriented silicon steel sheets of the laminated stator core each have a chemical composition of Si, Al and Mn totaling 4.35-4.55% by mass percentage.

[0101] In one alternative embodiment, the chemical composition of the non-oriented silicon steel sheets of the laminated rotor core and the laminated stator core can be exactly the same, for example, made from the same non-oriented silicon steel sheet; or they can be not exactly the same, for example, made from two different non-oriented silicon steel sheets.

[0102] The average grain size of the non-oriented silicon steel sheets in the laminated rotor core is 30~50μm, and the iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 The core exhibits a strength of ≥1.63T, a yield strength of ≥500MPa, a tensile strength of ≥600MPa, and an elongation of ≥15%. This demonstrates that the laminated rotor core possesses excellent magnetic properties and high mechanical strength, meeting the strength requirements of electric vehicle drive motors under high-speed conditions.

[0103] The average grain size of the non-oriented silicon steel sheets in the laminated stator core is 80~150μm, and the iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T. This demonstrates that the laminated stator core possesses superior magnetic properties, meeting the requirements of electric vehicle drive motors regarding stator iron loss under high-speed conditions.

[0104] In one embodiment, the thickness of the non-oriented silicon steel sheet of the laminated rotor core is 0.25 mm, and the iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%; correspondingly, the thickness of the non-oriented silicon steel sheet of the laminated stator core is 0.25mm, and the iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0105] Alternatively, in a variation, the thickness of the non-oriented silicon steel sheet of the laminated rotor core is 0.20 mm, and the iron loss P 1.0 / 400 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%; correspondingly, the thickness of the non-oriented silicon steel sheet of the laminated stator core is 0.20mm, and the iron loss P 1.0 / 400 ≤11.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0106] Alternatively, in another variation, the thickness of the non-oriented silicon steel sheet of the laminated rotor core is 0.15 mm, and the iron loss P 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%; correspondingly, the thickness of the non-oriented silicon steel sheet of the laminated stator core is 0.15mm, and the iron loss P 1.0 / 400 ≤10.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0107] The detailed description listed above is merely a specific description of feasible implementation methods of the present invention. The specific implementation methods of the present invention will be introduced below through several specific embodiments.

[0108] These embodiments provide a non-oriented silicon steel sheet, such as steel sheet 1-11 to 1-33, specifically a finished steel sheet that is cold-rolled and then annealed in one step.

[0109] The chemical composition of the steel plate is shown in Table 1.

[0110] [Table 1]

[0111] The thickness of each steel plate is shown in Table 2.

[0112] Performance tests were performed on each steel plate, including: tensile strength Rm, yield strength Re, and elongation δ were tested according to GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Room temperature test method"; iron loss and magnetic induction intensity were tested according to GB / T 3655-2008 "Method for measuring the magnetic properties of electrical steel sheets (strips) by means of Epstein square"; and grain size was measured according to GB / T 4335-2013 "Method for determining the ferrite grain size of cold-rolled low-carbon steel sheets". The results are shown in Table 2.

[0113] [Table 2]

[0114]

[0115] Furthermore, steel plates 1-11 to 1-33 underwent secondary annealing treatment, with a heating rate ≤5℃ / min, an annealing temperature of 980~1000℃, and a holding time of 90~120min. After the annealing, steel plates 2-11 to 2-33 were obtained with new numbers. The steel plates were then subjected to performance tests, including: testing iron loss and magnetic induction intensity using the national standard GB / T 3655-2008 "Method for Measuring the Magnetic Properties of Electrical Steel Sheets (Strips) Using Epstein Squares"; and measuring grain size using GB / T 4335-2013 "Method for Determining Ferrite Grain Size of Cold-Rolled Low-Carbon Steel Sheets". The results are shown in Table 3.

[0116] [Table 3]

[0117]

[0118] As can be seen from Tables 2 and 3, in this application, steel plates 1-11 to 1-33 have high mechanical strength, which can meet the high strength requirements of rotor cores when used in the preparation of rotor cores. At the same time, based on the chemical composition, microstructure and properties of steel plates 1-11 to 1-33, the corresponding annealed steel plates 2-11 to 2-33 can have low iron loss, which can meet the high requirements of stator cores in terms of low iron loss. That is, the non-oriented silicon steel plates of this application can meet the requirements of rotor cores for low iron loss, high magnetic induction intensity and high strength, and also meet the requirements of stator cores for base material, that is, they can have ultra-low iron loss and high magnetic induction intensity after annealing. Therefore, they can simultaneously meet the requirements of stator cores and rotor cores for cold-rolled and one-time annealed non-oriented silicon steel finished steel plates.

[0119] Second Implementation Method

[0120] The second embodiment of this application also provides a method for producing non-oriented silicon steel.

[0121] This production method, through a process route of steelmaking, hot rolling, cold rolling, and primary annealing, more specifically including steelmaking, continuous casting, hot rolling, normalizing, pickling, primary cold rolling, and primary annealing, can produce non-oriented silicon steel for the stator and rotor cores of electric vehicle motors. For example, it can be used to produce the non-oriented silicon steel described in the first embodiment above.

[0122] The following is a detailed description of each process.

[0123] <Steelmaking process>

[0124] In this process, molten steel is refined and cast into steel billets with a thickness of 200~240mm. After leaving the continuous casting machine, the steel billets are held at a temperature range of 600~900℃ for 3~8 hours.

[0125] In this process, the chemical composition of the resulting steel billet is controlled to be within the same range as that described in the first embodiment above, through steelmaking. For example, the chemical composition of the steel billet, by mass percentage, includes: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, and the remainder is Fe and unavoidable inclusions.

[0126] Thus, this application, through the design and control of chemical composition, creates conditions for subsequently achieving the high strength requirements of non-oriented silicon steel for the rotor core of electric vehicle drive motors and the low iron loss requirements of non-oriented silicon steel for the stator core.

[0127] Regarding the contents of Nb, V, Ti, Cr, Ni, and Cu.

[0128] Specifically, in one embodiment, during steelmaking, alloying elements such as Nb, V, Ti, Cr, Ni, and Cu may not be intentionally added, and these elements can exist as impurity elements in the molten steel, only needing to satisfy Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, and Cu≤0.02%. In this case, the content of any one or more of Nb, V, Ti, Cr, Ni, and Cu may be 0. Alternatively, in another embodiment, during steelmaking, any one or more of alloying elements such as Nb, V, Ti, Cr, Ni, and Cu may be added, satisfying Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, and Cu≤0.02%. In this case, the content of any one or more of Nb, V, Ti, Cr, Ni, and Cu is not 0.

[0129] In a preferred embodiment, during the steelmaking process, the chemical composition of the steel billet can be further controlled to meet the following requirements: a total of 4.35-4.55% Si, Al and Mn.

[0130] In this process, the specific method of steelmaking can be to use conventional processes such as KR desulfurization of molten iron, converter smelting, and vacuum refining to prepare molten steel that meets the above chemical composition. It can be implemented in any way known in the art and is not limited in this application.

[0131] Similarly, in this process, molten steel is cast into steel billets using continuous casting technology. The specific continuous casting technology can be implemented in any feasible manner known in the art, and this application does not limit it.

[0132] Furthermore, in this process, after the billet leaves the continuous casting machine, the heat treatment, especially the design of the heat treatment temperature and duration, is conducive to the full precipitation of MnS and AlN in the billet, creating conditions for precise control of recrystallization process and grain size in subsequent normalization, low-temperature primary annealing and high-temperature secondary annealing.

[0133] <Hot Rolling Process>

[0134] In this process, the steel billet is heated to 1080~1120℃ and held for 150~200 minutes. It is first rough rolled to obtain an intermediate billet with a thickness of 35~45mm, and then finished rolled and coiled to obtain a hot-rolled coil with a thickness of 1.80~2.20mm.

[0135] The finishing rolling temperature is 950±20℃, the final rolling temperature is 820±20℃, and the coiling temperature is 600±20℃.

[0136] In this way, by using lower heating temperatures, finishing rolling temperatures, and coiling temperatures, the coarse precipitates (MnS, AlN) in the billet are prevented from undergoing solid solution, creating conditions for precise control of the recrystallization process and grain size during subsequent normalizing, low-temperature primary annealing, and high-temperature secondary annealing.

[0137] Preferably, in this hot rolling process: the steel billet is fed into a heating furnace for heating, with an initial furnace temperature ≥500℃, a preheating temperature of 950~1000℃, and a heating and soaking temperature of 1080~1120℃, and the total heating and soaking time is 150~200min. That is, the steel billet undergoes three stages in the heating furnace: preheating, heating, and soaking. The preheating temperature is 950~1000℃, the heating and soaking temperatures are both 1080~1120℃, and the total time in the heating and soaking stages is 150~200min.

[0138] In this way, in addition to meeting the lower heating temperature requirements mentioned above, the hot-rolled edge cracks caused by rapid heating can be avoided by setting the furnace entry temperature and preheating temperature. Of course, under the basic technical principles of this application, if the problem of hot-rolled edge cracks is not considered, the furnace entry temperature and preheating temperature are not limited to these.

[0139] <Cold rolling process>

[0140] In this process, the hot-rolled coil is sequentially normalized, pickled, and cold-rolled once to obtain cold-rolled strip steel with a thickness of 0.15~0.25mm.

[0141] The normalizing temperature is 800~820℃ and held for 180~200s. This ensures that the proportion of recrystallized grains in the normalized steel sheet is 50~60%, and the average grain size of the recrystallized grains is ≤50μm. This improves the rollability of the steel sheet under high silicon and high aluminum content conditions, creating conditions for subsequent cold rolling of ultra-thin steel sheets of 0.15~0.25mm without preheating (i.e., no preheating required before cold rolling) and low-temperature complete recrystallization annealing.

[0142] In this process, the total reduction rate of a single cold rolling is 90±2%. Combined with the temperature control of the first annealing described later, the steel plate can be fully recrystallized during the first annealing, and the average grain size of the recrystallized grains can be controlled.

[0143] Preferably, in this process, except for the final pass, the reduction rate of each pass in a single cold rolling operation is above 30%. Of course, this application is not limited to this.

[0144] <Single annealing process>

[0145] In this process, the cold-rolled strip steel is annealed, cooled and coated once to obtain the finished steel plate, which is the non-oriented silicon steel with a thickness of 0.15~0.25mm described in the first embodiment above.

[0146] The annealing temperature is 850~900℃ and the holding time is 60~90s.

[0147] As mentioned earlier, based on the total reduction rate of cold rolling and combined with the design of the annealing temperature, the steel sheet can be fully recrystallized in the first annealing, that is, the finished steel sheet has a fully recrystallized structure, and the average grain size of recrystallization can be controlled. For example, the average grain size of recrystallization in the finished steel sheet is ≤50μm. In this way, the finished steel sheet can not only meet the performance requirements of high-strength non-oriented silicon steel for the rotor core of electric vehicle drive motor (for example, laminated rotor cores can be directly produced after stamping), but also meet the requirements of non-oriented silicon steel base material for the stator core of electric vehicle drive motor (for example, the grain structure can create conditions for obtaining a low-iron-loss grain structure in the subsequent secondary annealing). For example, laminated stator cores can be obtained by stamping, laminating and then annealing or annealing and then laminating, and the obtained stator cores have ultra-low iron loss and high magnetic induction intensity.

[0148] In summary, the production method described in one embodiment of this application can produce cold-rolled, one-time annealed non-oriented silicon steel sheets that simultaneously meet the requirements of stator cores and rotor cores. Compared to the conventional technology where cold-rolled, one-time annealed non-oriented silicon steel sheets for stator cores and rotor cores must be prepared separately, this method not only significantly reduces the manufacturing cost of the motor and its stator and rotor cores but also greatly maximizes the utilization of non-oriented silicon steel materials. For example, within a region of the steel sheet, the outer periphery forms an annular sheet for the stator core, and the center forms a sheet for the rotor core, thereby avoiding material waste.

[0149] Preferably, in one embodiment, the average grain size of recrystallization in the resulting steel plate product is 30~50μm.

[0150] Preferably, in a single annealing process, the annealing temperature is 850~870℃ and the holding time is 80~90s. This allows for more precise control of the average grain size of the recrystallized grains.

[0151] Preferably, in a single annealing process: a continuous annealing furnace can be used for single annealing, and production can be carried out at a constant speed of 130~150m / min, but it is not limited to this.

[0152] The first annealing can be performed in a weakly reducing protective atmosphere, such as a protective atmosphere of N2 and H2, wherein the volume percentage of H2 is 20-30% and the remainder is N2.

[0153] Furthermore, in a single annealing process: the cooling after the annealing is completed can be achieved using known cooling techniques in the art, including air cooling and other methods. The coating after cooling can be applied to the steel plate surface with commonly used paints in the art, which are not limited in this application.

[0154] Furthermore, the production method also includes stamping and secondary annealing processes, which can further process the obtained steel sheet into a secondary annealed steel sheet. The stamping and secondary annealing processes are described in detail below.

[0155] <Stamping process>

[0156] In this process, the finished steel plate is stamped to obtain a series of thin sheets.

[0157] Secondary annealing process

[0158] In this process, a series of thin sheets are first stacked and pressed together, and then subjected to secondary annealing to obtain a non-oriented silicon steel core; or, a series of thin sheets are first subjected to secondary annealing, and then stacked and pressed together to obtain a non-oriented silicon steel core.

[0159] During the secondary annealing: the heating rate is ≤5℃ / min, the annealing temperature is 980~1000℃, and the holding time is 90~120min.

[0160] Thus, by stamping, laminating, and then annealing, or by laminating after annealing, the resulting non-oriented silicon steel exhibits a coarser grain structure compared to the finished steel sheet before stamping. For example, the average recrystallized grain size increases from less than 50 μm in the finished steel sheet to 80-150 μm. This results in lower iron loss in the non-oriented silicon steel obtained after annealing. Specifically, for example, the iron loss P... 1.0 / 400 With a strength of ≤12.0 W / kg, non-oriented silicon steel cores with low iron loss can be produced.

[0161] In one embodiment, the secondary annealing process can be carried out using either a bell-type annealing furnace or a continuous annealing furnace, but is not limited to these.

[0162] Secondary annealing can be performed in a weakly reducing protective atmosphere, such as a protective atmosphere of N2 and H2, wherein the volume percentage of H2 is 20-30% and the remainder is N2.

[0163] Furthermore, in one embodiment, after the holding time for the secondary annealing is completed, the cooling rate can be controlled to be ≤3℃ / min. For example, the stacked sheets undergoing secondary annealing can be cooled in the annealing furnace, and the cooling rate of the annealing furnace can be controlled to be ≤3℃ / min.

[0164] In one embodiment, the non-oriented silicon steel core obtained through the secondary annealing process can be used as a stator core, which can meet the high requirements of low iron loss for stator cores.

[0165] Furthermore, in one embodiment, during the stamping process, a series of pairs of rotor and stator sheets can be stamped from the finished steel plate, with each pair of rotor and stator sheets being concentrically distributed. The stator sheets then proceed to the secondary annealing process to prepare the stator core; while the rotor sheets proceed to the rotor core preparation process described later.

[0166] Specifically, the production method further includes a rotor core preparation process: a series of rotor laminations are assembled into a rotor core by lamination pressing.

[0167] In this way, not only can the rotor core and stator core be prepared by stamping the same non-oriented silicon steel sheet, but also, for each rotor sheet punched around a center, a corresponding stator sheet surrounding that rotor sheet will be punched around that center (that is, the rotor sheet makes full use of the steel sheet in the central area of ​​the annular stator sheet). This can make full use of the non-oriented silicon steel material, greatly improve the material utilization rate, avoid material waste, and reduce the production cost of the motor.

[0168] It is understood that the order of operation of each process is not limited by the order in which they are presented in the technical description.

[0169] The detailed description listed above is merely a specific description of feasible implementation methods of the present invention. The specific implementation methods of the present invention will be introduced below through several specific embodiments.

[0170] These embodiments each provide a method for producing non-oriented silicon steel, the specific process of which is as follows:

[0171] (1) Refine the molten steel and cast it into steel billets. After leaving the continuous casting machine, the steel billets are kept at a temperature range of 600~900℃ for 3~8h. The thickness and chemical composition of the steel billets are shown in Table 4.

[0172] [Table 4]

[0173]

[0174] (2) The steel billet is heated in a heating furnace, and then the intermediate billet is obtained by rough rolling, and then the hot-rolled coil is obtained by finish rolling and coiling. The steel billet thickness, heating temperature, holding time, intermediate billet thickness, finish rolling start temperature, finish rolling temperature, coiling temperature and hot-rolled coil thickness are shown in Table 5.

[0175] [Table 5]

[0176]

[0177] (3) The hot-rolled coil is subjected to normalization, pickling and cold rolling in sequence to obtain cold-rolled strip steel; then it is subjected to annealing, cooling and coating to obtain finished steel plate; wherein, the normalization temperature, holding time, total reduction rate of cold rolling, thickness of cold-rolled strip steel, annealing temperature and holding time are shown in Table 6 respectively;

[0178] [Table 6]

[0179]

[0180] The “Finished Steel Plates” column in Table 6 records the correspondence between each example and the steel plate in the “Number” column in Table 1 above. For example, the finished steel plate prepared in Example 3-11 is steel plate 1-11 in Table 1 above.

[0181] As shown in Table 2 above, the test results of the microstructure and properties of the finished steel plate are as well as the test results of the microstructure and properties of the finished steel plate after secondary annealing are shown in Table 3. It can be seen that the non-oriented silicon steel plate produced by the first embodiment of this application can meet the requirements of the rotor core for low iron loss, high magnetic induction intensity and high strength, and can also meet the requirements of the stator core for the base material. That is, it can have ultra-low iron loss and high magnetic induction intensity after annealing. Therefore, it can simultaneously meet the requirements of both the stator core and the rotor core for cold-rolled and one-time annealed non-oriented silicon steel plate.

Claims

1. A non-oriented silicon steel, characterized in that, Its chemical composition, by mass percentage, includes: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions; The non-oriented silicon steel is a steel plate with a thickness of 0.15~0.25mm, an average grain size of less than 50μm, and an iron loss P. 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%.

2. The non-oriented silicon steel according to claim 1, characterized in that, The non-oriented silicon steel is a 0.25mm thick steel plate with an iron loss P. 1.0 / 400 ≤15.0W / kg; or, the non-oriented silicon steel is a steel plate with a thickness of 0.20mm, and its iron loss P 1.0 / 400 ≤14.0W / kg; or, the non-oriented silicon steel is a steel plate with a thickness of 0.15mm, and its iron loss P 1.0 / 400 ≤13.0W / kg.

3. The non-oriented silicon steel according to claim 1, characterized in that, After secondary annealing, the non-oriented silicon steel has an average grain size of 80~150μm and an iron loss P. 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T; During the secondary annealing: the heating rate is ≤5℃ / min, the annealing temperature is 980~1000℃, and the holding time is 90~120min.

4. The non-oriented silicon steel according to claim 1, characterized in that, The chemical composition of the non-oriented silicon steel, by mass percentage, also satisfies the following: Si, Al and Mn total 4.35~4.55%.

5. The non-oriented silicon steel according to claim 1, characterized in that, The non-oriented silicon steel is prepared by steelmaking, continuous casting, hot rolling, normalizing, pickling, one cold rolling and one annealing; wherein, the average grain size of the recrystallized steel plate obtained by normalizing is ≤50μm; The average grain size of the non-oriented silicon steel is 30~50μm.

6. A method for producing non-oriented silicon steel, characterized in that, The production method includes, Steelmaking: Refining molten steel and casting it into steel billets with a thickness of 200~240mm. After leaving the continuous casting machine, the steel billets are held at a temperature of 600~900℃ for 3~8h. The chemical composition of the steel billets, by mass percentage, includes: C≤0.0020%, S≤0.0010%, Si 3.25~3.55%, Al 0.55~0.85%, Mn 0.25~0.55%, P≤0.015%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, with the remainder being Fe and unavoidable inclusions. Hot rolling: After heating the steel billet to 1080~1120℃ and holding it at that temperature for 150~200min, it is first rough rolled to obtain an intermediate billet with a thickness of 35~45mm, and then finished rolled and coiled to obtain a hot rolled coil with a thickness of 1.80~2.20mm; wherein, the initial rolling temperature of the finish rolling is 950±20℃, the final rolling temperature is 820±20℃, and the coiling temperature is 600±20℃; Cold rolling: Hot-rolled coils are sequentially normalized, pickled, and cold-rolled once to obtain cold-rolled strip steel with a thickness of 0.15~0.25mm; wherein, the normalizing temperature is 800~820℃ and held for 180~200s, and the total reduction rate of the first cold rolling is 90±2%; Single annealing: After the cold-rolled strip steel is annealed, cooled and coated once, the finished steel plate is obtained; the annealing temperature is 850~900℃ and held for 60~90s.

7. The method for producing non-oriented silicon steel according to claim 6, characterized in that, In a single annealing process, the average grain size of the resulting steel plate is 30~50μm.

8. The method for producing non-oriented silicon steel according to claim 6, characterized in that, In the cold rolling process: the proportion of recrystallized grains in the normalized steel sheet is 50~60%, and the average grain size of recrystallized grains is ≤50μm.

9. The method for producing non-oriented silicon steel according to claim 6, characterized in that, The production method also includes, Stamping: The finished steel plate is stamped to obtain a series of thin sheets; Secondary annealing: First, stack and press a series of thin sheets, then perform secondary annealing; or, first, perform secondary annealing on a series of thin sheets, then stack and press them; wherein, during secondary annealing: heating rate ≤ 5℃ / min, annealing temperature 980~1000℃, holding time 90~120min.

10. The method for producing non-oriented silicon steel according to claim 9, characterized in that, In the secondary annealing process: after the heat preservation is completed, the cooling rate should be controlled to be ≤3℃ / min.

11. The method for producing non-oriented silicon steel according to claim 9, characterized in that, In the stamping process: a series of pairs of rotor and stator sheets are stamped from the finished steel plate, with each pair of rotor and stator sheets being concentrically distributed; the stator sheets then enter the secondary annealing process. The production method also includes a rotor core preparation process: a series of rotor laminations are assembled into a rotor core by lamination pressing.

12. The method for producing non-oriented silicon steel according to claim 9, characterized in that, After secondary annealing, the average grain size of the non-oriented silicon steel is 80~150μm.

13. The method for producing non-oriented silicon steel according to claim 6, characterized in that, In the hot rolling process: the steel billet is sent into the heating furnace for heating. The furnace temperature is ≥500℃, the preheating temperature is 950~1000℃, the heating and homogenization temperature is 1080~1120℃, and the total heating and homogenization time is 150~200min.

14. The method for producing non-oriented silicon steel according to claim 6, characterized in that, In the cold rolling process: except for the last pass, the reduction rate of each of the remaining passes in a single cold rolling process is more than 30%.

15. The method for producing non-oriented silicon steel according to claim 6, characterized in that, In one annealing process: the annealing temperature is 850~870℃ and the holding time is 80~90s.

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