Ultra-thin non-oriented silicon steel for motor stator and rotor iron core and production method and application of ultra-thin non-oriented silicon steel

Abstract

The invention discloses ultra-thin non-oriented silicon steel for a motor stator and rotor iron core and a production method and application of the ultra-thin non-oriented silicon steel. 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: 3.25-3.55% of Si, 0.55-0.85% of Al, 0.25-0.55% of Mn, less than or equal to 0.003% of Nb, less than or equal to 0.003% of V, less than or equal to 0.003% of Ti, less than or equal to 0.02% of Cr, less than or equal to 0.02% of Ni, less than or equal to 0.02% of Cu and the balance of Fe and impurities. The average grain size of the non-oriented silicon steel is smaller than 50 micrometers, the iron loss P1.0 / 400 is smaller than or equal to 15.0 W / kg, the magnetic induction intensity B5000 is larger than or equal to 1.63 T, the yield strength is larger than or equal to 500 MPa, the tensile strength is larger than or equal to 600 MPa, and the ductility is larger than or equal to 15%. According to the invention, the application requirements of the stator core and the rotor core can be simultaneously met, so that the manufacturing cost of the motor is greatly reduced, and material waste is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel material preparation, and relates to non-oriented silicon steel and a production method thereof, in particular to ultra-thin non-oriented silicon steel for motor stator and rotor cores and a production method thereof, and also to an application of the non-oriented silicon steel in motor stator and rotor cores. Background Art

[0002] The drive motor is one of the three core components of electric vehicles. Its driving characteristics directly determine the main performance indicators of the vehicle, such as climbing, acceleration, and maximum speed. It is an important component of electric vehicles. The electric vehicle drive motor is based on the electromagnetic induction phenomenon. It uses the stator to generate a rotating magnetic field and acts on the rotor to form magneto-electric power to drive the electric vehicle.

[0003] Non-oriented silicon steel is an important material for manufacturing the core components of motors - stator and rotor cores, and iron loss is one of the important magnetic performance parameters of non-oriented silicon steel.

[0004] Based on research, there are two main ways to reduce iron loss: increasing the resistivity of the steel plate and reducing the thickness of the steel plate. By increasing the Si and Al content in non-oriented silicon steel, the resistivity of the steel plate can be increased, thereby reducing the iron loss of non-oriented silicon steel; however, as the Si and Al content increases, the rollability of the steel plate decreases, which is not conducive to smooth production. Therefore, the method of reducing iron loss by increasing the Si and Al content has certain limitations. Reducing the thickness of the steel plate can not only directly reduce the iron loss, but also cause the resistivity of the steel plate to increase, thereby indirectly reducing the iron loss. Therefore, as the speed and frequency of the motor increase, the thickness of the non-oriented silicon steel is reduced-this is the most effective method to reduce iron loss.

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

[0006] Furthermore, in the drive motor, as the speed and frequency increase, the rotor core needs higher structural strength to overcome the challenge of high centrifugal force. In order to ensure the 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] Obviously, in terms of thickness, the rotor core and the stator core have different requirements for the thickness of non-oriented silicon steel - the rotor core requires a thicker steel plate based on structural strength requirements, and the stator core requires a thinner steel plate based on iron loss requirements.

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

[0009] Based on the above reasons, in the prior art, in the manufacture of high-speed drive motors for electric vehicles, the rotor core and the stator core generally need to prepare their own corresponding non-oriented silicon steel plates, that is, a thin non-oriented silicon steel plate is used to prepare the stator core, and another thick non-oriented silicon steel plate or a thin non-oriented silicon steel plate with poor magnetic properties is used to prepare the rotor core. This not only makes the manufacturing cost of the motor high, but also causes a large amount of waste of non-oriented silicon steel materials.

[0010] So far, there has never been a corresponding product in the field of non-oriented silicon steel that can meet the application requirements of stator core and rotor core at the same time. Summary of the invention

[0011] In order to solve the technical problem that the existing non-oriented silicon steel cannot meet the application requirements of stator core and rotor core at the same time, the purpose of the present invention is to provide a non-oriented silicon steel and a production method thereof, especially an ultra-thin non-oriented silicon steel for motor stator and rotor core and a production method thereof.

[0012] In order to solve the technical problem that the same non-oriented silicon steel plate cannot be used to produce the stator core and the rotor core, the present invention also aims to provide a motor core and a method for manufacturing the stator and rotor core for a motor.

[0013] To achieve the above-mentioned purpose, an embodiment of the present invention provides a non-oriented silicon steel. The chemical composition of the non-oriented silicon steel includes, 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%, and the rest is Fe and unavoidable inclusions; The non-oriented silicon steel is a steel plate with a thickness of 0.15-0.25 mm, an average grain size of less than 50 μm, 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%.

[0014] Preferably, the non-oriented silicon steel is a steel plate with a thickness of 0.25 mm and 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.

[0015] Preferably, after the secondary annealing, the average grain size of the non-oriented silicon steel is 80-150 μm, and the iron loss P is 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T; During annealing: the heating rate is ≤5°C / min, the annealing temperature is 980~1000°C, and the heat preservation time is 90~120min.

[0016] Preferably, the chemical composition of the non-oriented silicon steel further satisfies the following percentage by mass: Si, Al and Mn total 4.35-4.55%.

[0017] Preferably, the non-oriented silicon steel is prepared by molten steel refining, 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 ≤50 μm; The average grain size of the non-oriented silicon steel is 30-50 μm.

[0018] To achieve the above-mentioned purpose, an embodiment of the present invention provides a method for manufacturing a stator and rotor core for a motor. The manufacturing method uses the non-oriented silicon steel and comprises: Stamping: stamping the non-oriented silicon steel to obtain a series of rotor sheets and stator sheets; Rotor core preparation: A series of rotor sheets are assembled into a rotor core by lamination press-fitting; Preparation of stator core: first assembling a series of stator sheets into stator core laminations by lamination press-fitting, and then performing secondary annealing to obtain a stator core; or first performing secondary annealing on a series of stator sheets, and then assembling the stator core by lamination press-fitting; Among them, during the secondary annealing: the heating rate is ≤5°C / min, the annealing temperature is 980~1000°C, and the insulation time is 90~120min.

[0019] 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 manner.

[0020] To achieve the above-mentioned purpose, an embodiment of the present invention provides an iron core for a motor. The iron core for a motor comprises a laminated rotor iron core and a laminated stator iron core; The laminated rotor core and the laminated stator core are both made of non-oriented silicon steel with a thickness of 0.15-0.25 mm, and the chemical composition includes, 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%, and the rest is Fe and unavoidable inclusions; The average grain size of the non-oriented silicon steel sheets of the laminated rotor core is 30-50 μm, 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%; The average grain size of the non-oriented silicon steel sheets of the laminated stator core is 80-150 μm, and the iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0021] To achieve the above-mentioned purpose, an embodiment of the present invention provides a method for producing non-oriented silicon steel. The production method comprises: Steelmaking: Refining molten steel and casting it into billets with a thickness of 200~240mm. After leaving the continuous casting machine, the billets are kept warm at a temperature range of 600~900℃ for 3~8h. The chemical composition of the billets, in terms of 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 rest are Fe and unavoidable inclusions. Hot rolling: After heating the steel billet to 1080~1120℃ and keeping it warm for 150~200min, it is firstly subjected to rough rolling to obtain an intermediate billet with a thickness of 35~45mm, and then subjected to finish rolling and coiling to obtain a hot rolled coil with a thickness of 1.80~2.20mm; wherein, the start 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: The hot rolled coil is subjected to normalization, pickling and one-time cold rolling in sequence to obtain a cold rolled strip with a thickness of 0.15-0.25 mm; wherein the normalization temperature is 800-820°C and the temperature is kept for 180-200 seconds, and the total reduction rate of one-time cold rolling is 90±2%; Primary annealing: After the cold-rolled strip is subjected to primary annealing, cooling and coating, a finished steel plate is obtained; wherein, the annealing temperature is 850~900℃ and the temperature is kept for 60~90s.

[0022] Preferably, in the primary annealing process: the average grain size of the obtained steel plate product is 30-50 μm.

[0023] Preferably, in the cold rolling process: in the normalized steel sheet, the proportion of recrystallized grains is 50-60%, and the average recrystallized grain size is ≤50 μm.

[0024] Preferably, the production method further comprises, Stamping: stamping the finished steel plate to obtain a series of thin sheets; Secondary annealing: firstly stack and press a series of thin sheets, and then perform secondary annealing; or, firstly perform secondary annealing on a series of thin sheets, and then stack and press; wherein, during the secondary annealing: the heating rate is ≤5℃ / min, the annealing temperature is 980~1000℃, and the heat preservation time is 90~120min.

[0025] Preferably, in the secondary annealing process: after the heat preservation is completed, the cooling rate is controlled to be ≤3°C / min.

[0026] Preferably, in the stamping process: a series of pairs of rotor sheets and stator sheets are stamped out from the finished steel plate, and each pair of rotor sheets and stator sheets are distributed concentrically; and the stator sheets enter the secondary annealing process; The production method also includes a rotor core preparation step: assembling a series of rotor sheets into a rotor core by lamination press-fitting.

[0027] Preferably, after the secondary annealing, the average grain size of the non-oriented silicon steel is 80-150 μm.

[0028] Preferably, in the hot rolling process: the steel billet is fed into a heating furnace for heating, the furnace entry temperature is ≥500°C, the preheating temperature is 950-1000°C, the heating and soaking temperature is 1080-1120°C, and the total heating and soaking time is 150-200 min.

[0029] Preferably, in the cold rolling process: except for the last pass, the reduction rate of each of the remaining cold rolling passes is above 30%.

[0030] Preferably, in one annealing process, the annealing temperature is 850-870° C. and the temperature is maintained for 80-90 seconds.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: the same non-oriented silicon steel finished plate can simultaneously meet the needs of the stator core and the rotor core for the non-oriented silicon steel finished plate that is annealed once after cold rolling. Compared with the current situation in which the non-oriented silicon steel finished plate that is annealed once after cold rolling used for the stator core and the non-oriented silicon steel finished plate that is annealed once after cold rolling used for the rotor core in the conventional technology must be prepared separately, not only the manufacturing cost of the motor and its stator and rotor cores is greatly reduced, but also the full utilization of the non-oriented silicon steel material is greatly realized. For example, in one area of ​​the steel plate, the outer periphery can constitute the annular thin sheet of the stator core and the center can constitute the thin sheet of the rotor core, thereby avoiding material waste. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific implementation methods of the present invention. Obviously, the described implementation methods are only part of the implementation methods of the present invention, not all of the implementation methods. Based on the implementation methods of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] First embodiment An embodiment of the present invention provides an ultra-thin non-oriented silicon steel, which can meet the use requirements of the rotor core and the requirements of the stator core for the base material, that is, can meet the use requirements of the stator core.

[0034] The chemical composition of the non-oriented silicon steel includes, by mass percentage, C≤0.0020%, S≤0.0010%, Si3.25~3.55%, 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 rest is Fe and unavoidable inclusions.

[0035] The role of each chemical element in this embodiment is described in detail below.

[0036] Si, Al: Si and Al can increase the resistivity of the steel plate, thereby reducing iron loss. In addition, Si and Al can improve the strength of the steel plate; however, increased Si and Al content will cause difficulties in cold rolling; in one embodiment of the present application, the Si content is controlled between 3.25~3.55%, and the Al content is controlled between 0.55~0.85%.

[0037] Mn: Mn can improve the microstructure and texture of hot-rolled plate, strengthen the (100) and (110) components, and weaken the (111) component, which is beneficial to improving magnetic properties. Moreover, Mn easily forms MnS with S, and coarse MnS is beneficial to grain growth and reduces iron loss. In addition, Mn can also improve the strength of the steel plate. In one embodiment of the present application, the Mn content is controlled between 0.25% and 0.55%.

[0038] Nb, V, Ti, Cr, Ni, Cu: Adding Nb, V, Ti, Cr, Ni, and Cu to non-oriented silicon steel can improve the strength, but at the same time it will lead to increased iron loss and reduced magnetic induction; in one embodiment of the present application, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, and Cu≤0.02%.

[0039] 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 motors of electric vehicles, in one embodiment of the present application, C≤0.0020%, S≤0.0010%, and N≤0.0020%.

[0040] P: P is a residual element, which is detrimental to magnetic properties and causes difficulty in cold rolling. In one embodiment of the present application, P is controlled to be ≤ 0.015%.

[0041] In addition, in this embodiment, regarding the content of Nb, V, Ti, Cr, Ni, and Cu. Specifically, in one embodiment, in the steelmaking process, alloying elements such as Nb, V, Ti, Cr, Ni, and Cu may not be added intentionally, and these elements may exist as impurity elements in the molten steel, and only need 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, in the steelmaking process, any one or more of alloying elements such as Nb, V, Ti, Cr, Ni, and Cu may be added, and 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 is not 0.

[0042] The non-oriented silicon steel is a steel plate with a thickness of 0.15-0.25 mm. In this way, this ultra-thin non-oriented silicon steel can not only directly reduce iron loss, but also increase the resistivity of the steel plate, thereby indirectly reducing iron loss. Therefore, the non-oriented silicon steel of one embodiment of the present application has low iron loss.

[0043] Furthermore, the non-oriented silicon steel is prepared by molten steel refining, continuous casting, hot rolling, normalizing, pickling, one cold rolling and one annealing; wherein, the proportion of recrystallized grains of the steel plate obtained by normalization is 50-60%, and the average grain size of recrystallization is ≤50μm. In this way, by controlling the proportion of recrystallized grains and the average grain size of the steel plate after normalization, 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, thereby increasing the content of Si, Mn and Al to a certain extent, so as to improve the mechanical strength and reduce the iron loss from the composition, and then combining the grain size and the content of Si, Al and Mn, it can not only meet the requirements of the electric vehicle drive motor rotor core for the non-oriented silicon steel used in high mechanical properties, but also create conditions for the preparation of the electric vehicle drive motor stator core, especially for obtaining coarse grains after secondary annealing to further reduce iron loss and lay the foundation.

[0044] In one embodiment of the present application, the iron loss P of the non-oriented silicon steel is 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%.

[0045] Based on the above settings and controls in terms of chemical composition, thickness, grain size and performance (including magnetic properties and mechanical properties), the non-oriented silicon steel of one embodiment of the present application can not only meet the requirements of the rotor core for low iron loss, high magnetic induction intensity and high strength without the need for a large amount of alloy elements, that is, the non-oriented silicon steel can be used to prepare the rotor core, for example, by stamping and laminating to obtain a laminated rotor core, and the obtained rotor core has the performance 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 the stator core for the base material, that is, the non-oriented silicon steel can be used to prepare the stator core, for example, by stamping, laminating and then annealing or laminating after annealing to obtain a laminated stator core, and the obtained stator core has the performance of ultra-low iron loss and high magnetic induction intensity.

[0046] Therefore, the non-oriented silicon steel of one embodiment of the present application can be used as the base material of both the rotor core and the stator core, and can simultaneously meet the needs of the stator core and the rotor core for the non-oriented silicon steel finished steel plates that are annealed once after cold rolling. Compared with the current situation in which the non-oriented silicon steel finished steel plates that are annealed once after cold rolling used for the stator core and the non-oriented silicon steel finished steel plates that are annealed once after cold rolling used for the rotor core in conventional technology must be prepared separately, not only the manufacturing cost of the motor and its stator and rotor cores is greatly reduced, but also the full utilization of the non-oriented silicon steel materials is greatly realized. For example, in one area of ​​the steel plate, the outer periphery can constitute the annular thin sheets of the stator core, and the center can constitute the thin sheets of the rotor core, thereby avoiding material waste.

[0047] Furthermore, in one embodiment of the present application, the non-oriented silicon steel has an average grain size of 80-150 μm and an iron loss P of 0.05 μm after secondary annealing based on the chemical composition, thickness, average grain size and performance. 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T. It can be seen that after the secondary annealing treatment, the average grain size of the non-oriented silicon steel can be greatly increased, the iron loss can be reduced, and it can be used as a stator core material.

[0048] In the secondary annealing treatment, the heating rate is ≤5°C / min, the annealing temperature is 980-1000°C, and the temperature is kept for 90-120min. Of course, the annealing treatment of this embodiment is not limited thereto, and other feasible annealing treatment conditions may also be used for annealing treatment.

[0049] In a preferred embodiment, the chemical composition of the non-oriented silicon steel further satisfies: Si, Al and Mn total 4.35-4.55%. Thus, by further controlling the total content of Si, Al and Mn, the mechanical strength and magnetic properties can be ensured, and the rollability can also be enhanced.

[0050] Preferably, the average grain size of the non-oriented silicon steel can be controlled within 30-50 μm. Thus, by controlling the average grain size, coarse grains can be obtained after secondary annealing to further reduce iron loss, so that the non-oriented silicon steel can meet the application requirements of the stator core.

[0051] In addition, the structure of the non-oriented silicon steel is a completely recrystallized structure, that is, the proportion of recrystallized grains is 100%.

[0052] In addition, the yield strength of the non-oriented silicon steel is 500-550 MPa, and the tensile strength is 600-650 MPa.

[0053] In one embodiment, the non-oriented silicon steel may be a steel plate with a thickness of 0.25 mm, and its iron loss P1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0054] Correspondingly, after the secondary annealing treatment, the iron loss P of the non-oriented silicon steel sheet with a thickness of 0.25 mm in this embodiment is 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0055] Or in a variation embodiment, the non-oriented silicon steel may be a steel plate with a thickness of 0.20 mm, and its iron loss P 1.0 / 400 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0056] Correspondingly, after the secondary annealing treatment, the iron loss P of the non-oriented silicon steel sheet with a thickness of 0.20 mm in this embodiment is 1.0 / 400 ≤11.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0057] In another embodiment, the non-oriented silicon steel may be a steel plate with a thickness of 0.15 mm, and its iron loss P 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0058] Correspondingly, after the secondary annealing treatment, the non-oriented silicon steel sheet with a thickness of 0.15 mm in this embodiment has an iron loss P of 1.0 / 400 ≤10.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0059] Furthermore, the present embodiment also provides a method for manufacturing a stator and rotor core for a motor, and in particular, a method for manufacturing a stator and rotor core for a drive motor of an electric vehicle.

[0060] The manufacturing method adopts the non-oriented silicon steel mentioned above to prepare the rotor core and the stator core.

[0061] The manufacturing method includes processes such as stamping, rotor core preparation, stator core preparation, etc. These processes are introduced below.

[0062] Stamping process: stamping the non-oriented silicon steel to obtain a series of rotor sheets and stator sheets.

[0063] As mentioned above, the thickness of the non-oriented silicon steel is 0.15-0.25 mm. 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 0.15-0.25 mm.

[0064] Rotor core preparation process: A series of rotor sheets are assembled into the rotor core through lamination pressing.

[0065] In this way, a rotor core for a motor can be prepared, that is, a laminated rotor core, and in the laminated rotor core, the non-oriented silicon steel sheets have low iron loss, high magnetic induction intensity, and high mechanical strength. For example, the average grain size of the non-oriented silicon steel sheets is 30-50 μm, and the iron loss P is 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%.

[0066] Stator core preparation process: first, a series of stator sheets are assembled into stator core laminations by lamination press-fitting, and then secondary annealing is performed to obtain the stator core; or, a series of stator sheets are first subjected to secondary annealing, and then assembled into the stator core by lamination press-fitting.

[0067] Among them, during the secondary annealing: the heating rate is ≤5°C / min, the annealing temperature is 980~1000°C, and the insulation time is 90~120min.

[0068] In this way, a stator core for a motor can be prepared, that is, a laminated stator core, and in the laminated stator core, the non-oriented silicon steel sheets have lower iron loss and high magnetic induction intensity. For example, the average grain size of the non-oriented silicon steel sheets is 80-150 μm, and the iron loss P is 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0069] It can be seen that the manufacturing method of one embodiment of the present application can use the same non-oriented silicon steel plate for stamping, and then prepare the rotor core and the stator core, and the rotor core has high strength and the stator core has low iron loss. Compared with the conventional technology that the non-oriented silicon steel sheets of the stator core and the rotor core cannot be derived from the same non-oriented silicon steel plate, not only the manufacturing cost of the motor and its stator and rotor core is greatly reduced, but also the full utilization of the non-oriented silicon steel material is greatly realized, avoiding material waste.

[0070] Among them, it can be understood that the order of operation of each process in the manufacturing method is not limited by the order of the technical introduction. For example, although the "rotor core preparation process" is introduced first and the "stator core preparation process" is introduced later in the technical introduction, the implementation order of the two processes can occur simultaneously, or the rotor core preparation process is carried out first and then the stator core preparation process, or the stator core preparation process is carried out first and then the rotor core preparation process, etc. For another example, although the "stamping process" is introduced first and then the "rotor core preparation process" and the "stator core preparation process" are introduced in the technical introduction, in the specific implementation, the "stamping process" can be completely carried out before the "rotor core preparation process" and the "stator core preparation process", or it can be carried out simultaneously with the "rotor core preparation process" and the "stator core preparation process" (such as laminating while stamping). These changes in the implementation order do not deviate from the technical purpose of this application.

[0071] In addition, in one embodiment, the secondary annealing in the stator core preparation process can be performed using either a bell annealing furnace or a continuous annealing furnace, but is not limited thereto.

[0072] The secondary annealing may 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.

[0073] Furthermore, in one embodiment, in the stator core preparation process, after the insulation of the secondary annealing is completed, the cooling rate can be controlled to be ≤3°C / min. For example, in an embodiment of performing secondary annealing on the stator core laminations, the stator core laminations can be cooled in an annealing furnace, and the cooling rate of the annealing furnace is controlled to be ≤3°C / min, so that the cooling rate of the stator core laminations is ≤3°C / min; or, in an embodiment of performing secondary annealing on a series of stator sheets, the stator sheets can be cooled in an annealing furnace, and the cooling rate of the annealing furnace is controlled to be ≤3°C / min, so that the cooling rate of the stator sheets is ≤3°C / min.

[0074] Furthermore, in one embodiment, the stamping process is as follows: stamping out a pair of rotor sheets and stator sheets from the non-oriented silicon steel in a concentric distribution manner.

[0075] That is to say, every time a rotor sheet is punched out from non-oriented silicon steel around a center of a circle, a stator sheet surrounding the rotor sheet will also be punched out from non-oriented silicon steel around the center of the circle (that is, the rotor sheet just utilizes the steel plate in the center area of ​​the circular stator sheet).

[0076] In this way, full utilization of non-oriented silicon steel materials can be achieved, which greatly improves material utilization, avoids material waste, and reduces the production cost of the motor.

[0077] Furthermore, an embodiment of the present application also provides an iron core for a motor, the iron core comprising a laminated rotor core and a laminated stator core.

[0078] The laminated rotor core and the laminated stator core can be made of the non-oriented silicon steel mentioned above, and the specific preparation process can adopt the manufacturing method mentioned above. Of course, the present application is not limited thereto.

[0079] Specifically, the laminated rotor core and the laminated stator core are both made of non-oriented silicon steel with a thickness of 0.15-0.25 mm, and the chemical composition, in 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 rest are Fe and unavoidable inclusions.

[0080] That is, the chemical composition of the non-oriented silicon steel sheets of the laminated rotor core meets the following requirements, calculated 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%, and the rest are Fe and unavoidable inclusions.

[0081] At the same time, the chemical composition of the non-oriented silicon steel sheets of the laminated stator core also meets the following requirements, calculated 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%, and the rest are Fe and unavoidable inclusions.

[0082] Preferably, the non-oriented silicon steel sheets of the laminated rotor core and the non-oriented silicon steel sheets of the laminated stator core respectively satisfy the total chemical composition of Si, Al and Mn of 4.35-4.55% by mass percentage.

[0083] In an optional embodiment, the chemical composition of the non-oriented silicon steel sheets of the laminated rotor core and the laminated stator core can be completely the same, for example, they are made from the same non-oriented silicon steel plate; or they can be not completely the same, for example, they are made from two different non-oriented silicon steel plates.

[0084] The average grain size of the non-oriented silicon steel sheets of the laminated rotor core is 30-50 μm, 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%. It can be seen that the laminated rotor core has excellent magnetic properties and high mechanical strength, which can meet the requirements of electric vehicle drive motors for rotor strength at high speeds.

[0085] The average grain size of the non-oriented silicon steel sheets of the laminated stator core is 80-150 μm, and the iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63 T. It can be seen that the laminated stator core has more excellent magnetic properties and can meet the requirements of electric vehicle drive motors on stator iron loss at high speeds.

[0086] 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%; accordingly, 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.

[0087] 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%; accordingly, 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.

[0088] Alternatively, in another embodiment, the thickness of the non-oriented silicon steel sheet of the laminated rotor core is 0.15 mm, and the iron loss P1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.63T, yield strength ≥500MPa, tensile strength ≥600MPa, elongation ≥15%; accordingly, 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.

[0089] The detailed description listed above is only a specific description of the feasible implementation mode of the present invention. The specific implementation mode of the present invention is introduced through several specific examples below.

[0090] These embodiments respectively provide a non-oriented silicon steel plate, such as steel plates 1-11 to 1-33, specifically, a finished steel plate that is annealed once after cold rolling.

[0091] The chemical composition of the steel plates is shown in Table 1.

[0092] [Table 1]

[0093] The thickness of each steel plate is shown in Table 2.

[0094] The performance tests of each steel plate were carried out, including: using the standard GB / T 228.1-2021 "Tensile test of metallic materials Part 1 Room temperature test method" to test the tensile strength Rm, yield strength Re and elongation δ; using the national standard GB / T 3655-2008 "Method for measuring the magnetic properties of electrical steel sheets (strips) using Epstein square rings" to test the iron loss and magnetic induction intensity; using GB / T 4335-2013 "Determination of ferrite grain size of cold-rolled low-carbon steel sheets" to measure the grain size; the results are shown in Table 2.

[0095] [Table 2]

[0096] In addition, the steel plates 1-11 to 1-33 were subjected to secondary annealing treatment, with a heating rate of ≤5°C / min, an annealing temperature of 980~1000°C, and a heat preservation time of 90~120min. After the treatment, the renumbered steel plates 2-11 to 2-33 were obtained, and then the steel plates were subjected to performance testing, including: using the national standard GB / T 3655-2008 "Method for measuring magnetic properties of electrical steel sheets (strips) using Epstein square rings" to test iron loss and magnetic induction intensity; using GB / T 4335-2013 "Method for determining ferrite grain size of cold-rolled low-carbon steel sheets" to measure grain size; the results are shown in Table 3.

[0097] [Table 3]

[0098] It can be seen from Table 2 and Table 3 that in the present application, the steel plates 1-11 to 1-33 have high mechanical strength, and when used in the preparation of the rotor core, they can meet the high strength requirements of the rotor core; at the same time, based on the chemical composition, organization and performance settings of the steel plates 1-11 to 1-33, the corresponding steel plates 2-11 to 2-33 after annealing can have low iron loss, which can meet the high requirements of the stator core in terms of low iron loss; that is, the non-oriented silicon steel plates of the present application can not only meet the requirements of the rotor core for low iron loss, high magnetic induction intensity and high strength, but also meet the requirements of the stator core for the parent material, that is, they can have the performance of ultra-low iron loss and high magnetic induction intensity after annealing, so they can simultaneously meet the needs of the stator core and the rotor core for the non-oriented silicon steel finished steel plates that are annealed once after cold rolling.

[0099] Second embodiment The second embodiment of the present application also provides a method for producing non-oriented silicon steel.

[0100] The production method can produce non-oriented silicon steel for the stator and rotor cores of electric vehicles through a process route of steelmaking, hot rolling, cold rolling and primary annealing, which includes more specifically molten steel refining, continuous casting, hot rolling, normalizing, pickling, primary cold rolling and primary annealing. For example, it can be used to produce the non-oriented silicon steel introduced in the first embodiment above.

[0101] The following is a detailed introduction to each process.

[0102] <Steelmaking Process> In this process, molten steel is refined and cast into billets with a thickness of 200-240 mm. After leaving the continuous casting machine, the billets are kept at a temperature range of 600-900°C for 3-8 hours.

[0103] In this process, by refining molten steel, the chemical composition of the obtained steel billet is controlled to be the same as the range of the chemical composition introduced in the first embodiment. For example, the chemical composition of the steel billet includes, 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%, and the rest is Fe and unavoidable inclusions.

[0104] In this way, this application creates conditions for the subsequent realization of the high strength requirements of non-oriented silicon steel for rotor cores of electric vehicle drive motors and the low iron loss requirements of non-oriented silicon steel for stator cores through the design and control of chemical composition.

[0105] As for the content of Nb, V, Ti, Cr, Ni and Cu.

[0106] Specifically, in one embodiment, when refining molten steel, alloy elements such as Nb, V, Ti, Cr, Ni, and Cu may not be added intentionally, and these elements may exist as impurity elements in the molten steel, and it is only necessary 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, when refining molten steel, any one or more of alloy elements such as Nb, V, Ti, Cr, Ni, and Cu may be added, and 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 is not 0.

[0107] In a preferred embodiment, in this process, by refining molten steel, the chemical composition of the steel billet can be controlled to further satisfy: the total content of Si, Al and Mn is 4.35-4.55%.

[0108] In this process, the specific method of refining molten steel can adopt the conventional process of molten iron KR desulfurization, converter smelting, and vacuum refining to prepare molten steel meeting the above-mentioned chemical composition. It can be implemented in a feasible manner known in the art, and this application does not limit it.

[0109] Similarly, in this process, the molten steel is cast into steel billets through continuous casting technology, wherein the specific continuous casting technology can also be implemented in a feasible manner known in the art, and this application does not limit it.

[0110] Furthermore, in this process, after the billet leaves the continuous casting machine, the insulation treatment, especially the design of the insulation temperature and duration, is conducive to the full precipitation of MnS and AlN in the billet, creating conditions for the precise control of the recrystallization process and grain size during subsequent normalization, low-temperature primary annealing and high-temperature secondary annealing.

[0111] <Hot rolling process> In this process, the steel billet is heated to 1080~1120℃ and kept warm for 150~200min, and then rough rolled to obtain an intermediate billet with a thickness of 35~45mm, and then fine rolled and coiled to obtain a hot-rolled coil with a thickness of 1.80~2.20mm.

[0112] Among them, the start rolling temperature of the finishing rolling is 950±20℃, the final rolling temperature is 820±20℃, and the coiling temperature is 600±20℃.

[0113] In this way, by lowering the heating temperature, finishing rolling temperature and coiling temperature, the solid solution of coarse precipitates (MnS, AlN) in the ingot can be avoided, creating conditions for accurately controlling the recrystallization process and grain size during subsequent normalizing, low-temperature primary annealing and high-temperature secondary annealing.

[0114] Preferably, in the hot rolling process: the steel billet is sent to a heating furnace for heating, the furnace entry temperature is ≥500°C, the preheating temperature is 950-1000°C, the heating and soaking temperatures are 1080-1120°C, and the total heating and soaking time is 150-200 minutes. That is, the steel billet undergoes three stages of preheating, heating, and soaking in the heating furnace, the preheating section temperature is 950-1000°C, the heating section and soaking section temperatures are both 1080-1120°C, and the total time in the heating section and soaking section is 150-200 minutes.

[0115] In this way, in addition to meeting the lower heating temperature described above, the hot rolling edge cracking caused by rapid heating can also be avoided by setting the furnace entry temperature and preheating temperature. Of course, under the basic technical purpose of this application, if the hot rolling edge cracking problem is not considered, it is not limited to the furnace entry temperature and preheating temperature.

[0116] <Cold rolling process> In this process, the hot-rolled coil is normalized, pickled and cold-rolled once in sequence to obtain a cold-rolled strip with a thickness of 0.15~0.25mm.

[0117] The normalizing temperature is 800~820℃ and the temperature is kept for 180~200s. In this way, the proportion of recrystallized grains in the normalized steel plate can be 50~60%, and the average recrystallized grain size is ≤50μm, thereby improving the rollability of the steel plate under the condition of high silicon and high aluminum content, creating conditions for the subsequent cold rolling of 0.15~0.25mm ultra-thin steel plates without preheating in advance (that is, no preheating before cold rolling) and low-temperature complete recrystallization annealing.

[0118] In this process, the total reduction ratio of the primary cold rolling is 90±2%. Combined with the temperature control of the primary annealing described later, the steel plate can be completely recrystallized in the primary annealing and the average grain size of the recrystallization can be controlled.

[0119] Preferably, in this process, except for the last pass, the reduction rate of each of the remaining passes of the primary cold rolling is above 30%. Of course, the present application is not limited thereto.

[0120] <Primary Annealing Process> In this process, the cold-rolled steel strip is subjected to annealing, cooling and coating to obtain a finished steel plate, that is, the non-oriented silicon steel with a thickness of 0.15-0.25 mm as described in the first embodiment above.

[0121] The annealing temperature is 850~900℃ and kept for 60~90s.

[0122] As mentioned above, based on the total reduction rate of the previous cold rolling, combined with the design of the annealing temperature, the steel plate can be completely recrystallized in one annealing, that is, the finished steel plate has a completely recrystallized structure, and the average grain size of the recrystallization can be controlled, for example, the average recrystallized grain size in the finished steel plate is ≤50μm, so that the finished steel plate can not only meet the performance requirements of high-strength non-oriented silicon steel for electric vehicle drive motor rotor core (for example, a laminated rotor core can be directly obtained after stamping), but also meet the requirements of non-oriented silicon steel base material for electric vehicle drive motor stator core (for example, the grain structure can create conditions for subsequent secondary annealing to obtain a grain structure with low iron loss), for example, a laminated stator core is obtained by stamping, annealing after lamination, or lamination after annealing, and the obtained stator core has the performance of ultra-low iron loss and high magnetic induction intensity.

[0123] In summary, the production method of one embodiment of the present application can produce finished non-oriented silicon steel plates that are annealed once after cold rolling and meet the requirements of both the stator core and the rotor core. Compared with the current situation in which the finished non-oriented silicon steel plates that are annealed once after cold rolling used for the stator core and the rotor core in conventional technology must be prepared separately, not only the manufacturing cost of the motor and its stator and rotor cores is greatly reduced, but also the full utilization of the non-oriented silicon steel materials is greatly realized. For example, in one area of ​​the steel plate, the outer periphery can constitute the annular thin sheets of the stator core, and the center can constitute the thin sheets of the rotor core, thereby avoiding material waste.

[0124] Preferably, in one embodiment, the average recrystallized grain size in the obtained steel sheet product is 30-50 μm.

[0125] Preferably, in the first annealing process, the annealing temperature is 850-870° C. and the temperature is kept for 80-90 seconds. In this way, the average grain size of the recrystallized product can be more accurately controlled.

[0126] Preferably, in the primary annealing process: a continuous annealing furnace may be used for primary annealing, and the production may be performed at a constant speed of 130-150 m / min, but is not limited thereto.

[0127] The primary annealing may 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.

[0128] Furthermore, in the primary annealing process: the cooling after the primary annealing is completed can adopt cooling techniques known in the art including wind cooling, air cooling, etc., and the coating after cooling can be specifically coated on the surface of the steel plate with coatings commonly used in the art, which are not limited in this application.

[0129] Furthermore, the production method further comprises stamping and secondary annealing steps, so that the obtained steel plate product can be further made into a secondary annealed steel plate. The stamping and secondary annealing steps are described in detail below.

[0130] <Pressing process> In this process, the finished steel plate is punched to obtain a series of thin sheets.

[0131] <Secondary Annealing Process> In this process, a series of thin sheets are first laminated and pressed, 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 laminated and pressed to obtain a non-oriented silicon steel core.

[0132] Among them, during the secondary annealing: the heating rate is ≤5°C / min, the annealing temperature is 980~1000°C, and the insulation time is 90~120min.

[0133] Thus, the non-oriented silicon steel obtained by stamping, lamination and secondary annealing or lamination after secondary annealing forms a coarse grain structure compared with the finished steel plate before stamping. For example, the average grain size of recrystallization grows from less than 50 μm of the finished steel plate to 80-150 μm, so that the non-oriented silicon steel obtained after secondary annealing has lower iron loss. For example, the iron loss P 1.0 / 400 ≤12.0W / kg, thus a non-oriented silicon steel core with low iron loss can be produced.

[0134] In one embodiment, in the secondary annealing process, the secondary annealing can be performed in a bell annealing furnace or a continuous annealing furnace, but is not limited thereto.

[0135] The secondary annealing may 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.

[0136] Furthermore, in one embodiment, after the heat preservation of the secondary annealing is completed, the cooling rate can be controlled to be ≤3°C / min. For example, the laminates subjected to the secondary annealing can be cooled in the annealing furnace, and the cooling rate of the annealing furnace is controlled to be ≤3°C / min.

[0137] In one embodiment, the non-oriented silicon steel core obtained through the secondary annealing process can be used as a stator core and can meet the high requirements of the stator core in terms of low iron loss.

[0138] Furthermore, in one embodiment, in the stamping process, a series of pairs of rotor sheets and stator sheets can be stamped out from the finished steel plate, and each pair of rotor sheets and stator sheets are concentrically distributed. The stator sheets enter the secondary annealing process to prepare the stator core, and the rotor sheets enter the rotor core preparation process described later.

[0139] Specifically, the production method also includes a rotor core preparation step: assembling a series of rotor sheets into a rotor core by lamination press-fitting.

[0140] In this way, not only can the rotor core and the stator core be prepared by stamping the same non-oriented silicon steel plate product, but also each time a rotor sheet is punched out around a center of a circle, a corresponding stator sheet surrounding the rotor sheet will also be punched out around the center of the circle (that is, the rotor sheet just utilizes the steel plate in the center area of ​​the circular stator sheet), which can achieve full utilization of the non-oriented silicon steel material, greatly improve the utilization rate of the material, avoid material waste, and reduce the production cost of the motor.

[0141] It is understandable that the order of operation of the various steps described is not limited by the order in which they are described in the technical introduction.

[0142] The detailed description listed above is only a specific description of the feasible implementation mode of the present invention. The specific implementation mode of the present invention is introduced through several specific examples below.

[0143] These embodiments respectively provide a method for producing non-oriented silicon steel, and the specific process is as follows: (1) Molten steel is refined and cast into billets. After leaving the continuous casting machine, the billets are kept at a temperature range of 600-900°C for 3-8 h. The thickness and chemical composition of the billets are shown in Table 4.

[0144] [Table 4]

[0145] (2) The steel billet is heated in a heating furnace, and then subjected to rough rolling to obtain an intermediate billet, and then subjected to finish rolling and coiling to obtain a hot-rolled coil; wherein the steel billet thickness, heating temperature, holding time, intermediate billet thickness, start rolling temperature of finish rolling, final rolling temperature, coiling temperature and hot-rolled coil thickness are shown in Table 5 respectively; [Table 5]

[0146] (3) The hot-rolled coil is subjected to normalization, pickling and primary cold rolling in sequence to obtain a cold-rolled steel strip; and then subjected to primary annealing, cooling and coating to obtain a finished steel plate; wherein the normalization temperature, the holding time, the total reduction ratio of the primary cold rolling, the thickness of the cold-rolled steel strip, the primary annealing temperature and the holding time are shown in Table 6 respectively; [Table 6]

[0147] Each embodiment in the column "Finished steel plate" in Table 6 records the corresponding relationship with each steel plate in the column "Number" in Table 1 above. For example, the finished steel plate prepared in Embodiment 3-11 is the steel plate 1-11 in Table 1 above. From the test results of the structure and properties of the finished steel plate shown in Table 2 and the test results of the structure and properties of the finished steel plate after secondary annealing shown in Table 3, it can be seen that the finished non-oriented silicon steel plate produced by one embodiment of the present application can not only meet the requirements of the rotor core for low iron loss, high magnetic induction intensity and high strength, but also meet the requirements of the stator core for the base material, that is, it can have the performance of ultra-low iron loss and high magnetic induction intensity after annealing, so it can simultaneously meet the needs of the stator core and the rotor core for the finished non-oriented silicon steel plate that is annealed once after cold rolling.

Claims

1. A non-oriented silicon steel, characterized in that: Its chemical composition includes 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%, and the rest is Fe and unavoidable inclusions; The non-oriented silicon steel is a steel plate with a thickness of 0.15-0.25 mm, an average grain size of less than 50 μm, 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 steel plate with a thickness of 0.25 mm and 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 80-150 μm and an iron loss of 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T; Among them, during the secondary annealing: the heating rate is ≤5°C / min, the annealing temperature is 980~1000°C, and the heat preservation 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 further satisfies, in terms of mass percentage, that the total amount of Si, Al and Mn is 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 molten steel refining, continuous casting, hot rolling, normalization, pickling, one cold rolling and one annealing; wherein the average grain size of the recrystallized steel plate obtained by normalization is ≤50μm; The average grain size of the non-oriented silicon steel is 30-50 μm.

6. A method for manufacturing a stator and rotor core for a motor, characterized in that: The manufacturing method adopts the non-oriented silicon steel according to claim 1, and comprises: Stamping: stamping the non-oriented silicon steel to obtain a series of rotor sheets and stator sheets; Rotor core preparation: A series of rotor sheets are assembled into a rotor core by lamination press-fitting; Preparation of stator core: first assembling a series of stator sheets into stator core laminations by lamination press-fitting, and then performing secondary annealing to obtain a stator core; or first performing secondary annealing on a series of stator sheets, and then assembling the stator core by lamination press-fitting; Among them, during the secondary annealing: the heating rate is ≤5°C / min, the annealing temperature is 980~1000°C, and the insulation time is 90~120min.

7. The method for manufacturing a stator and rotor core for a motor according to claim 6, characterized in that: In the punching process, a pair of rotor sheets and stator sheets are punched out from the non-oriented silicon steel in a concentrically distributed manner.

8. An iron core for a motor, characterized in that: It includes a laminated rotor core and a laminated stator core; The laminated rotor core and the laminated stator core are both made of non-oriented silicon steel with a thickness of 0.15-0.25 mm, and the chemical composition includes, by mass percentage: C≤0.0020%, S≤0.0010%, Si 3.25-3.55%, Al 0.55-0.85%, Mn0.25-0.55%, 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 rest is Fe and unavoidable inclusions; The average grain size of the non-oriented silicon steel sheets of the laminated rotor core is 30-50 μm, 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%; The average grain size of the non-oriented silicon steel sheets of the laminated stator core is 80-150 μm, and the iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

9. A method for producing non-oriented silicon steel, characterized in that: The production method comprises, Steelmaking: Refining molten steel and casting it into billets with a thickness of 200~240mm. After leaving the continuous casting machine, the billets are kept warm at a temperature range of 600~900℃ for 3~8h. The chemical composition of the billets, in terms of 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 rest are Fe and unavoidable inclusions. Hot rolling: After heating the steel billet to 1080~1120℃ and keeping it warm for 150~200min, it is firstly subjected to rough rolling to obtain an intermediate billet with a thickness of 35~45mm, and then subjected to finish rolling and coiling to obtain a hot rolled coil with a thickness of 1.80~2.20mm; wherein, the start 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: The hot rolled coil is subjected to normalization, pickling and one-time cold rolling in sequence to obtain a cold rolled strip with a thickness of 0.15-0.25 mm; wherein the normalization temperature is 800-820°C and the temperature is kept for 180-200 seconds, and the total reduction rate of the one-time cold rolling is 90±2%; Primary annealing: After the cold-rolled strip is subjected to primary annealing, cooling and coating, a finished steel plate is obtained; wherein, the annealing temperature is 850~900℃ and the temperature is kept for 60~90s.

10. The method for producing non-oriented silicon steel according to claim 9, characterized in that: In the primary annealing process: the average grain size of the obtained steel plate product is 30~50μm.

11. The method for producing non-oriented silicon steel according to claim 9, characterized in that: In the cold rolling process: in the normalized steel plate, the proportion of recrystallized grains is 50~60%, and the average recrystallized grain size is ≤50μm.

12. The method for producing non-oriented silicon steel according to claim 9, characterized in that: The production method further comprises, Stamping: stamping the finished steel plate to obtain a series of thin sheets; Secondary annealing: firstly stack and press a series of thin sheets, and then perform secondary annealing; or, firstly perform secondary annealing on a series of thin sheets, and then stack and press; wherein, during the secondary annealing: the heating rate is ≤5℃ / min, the annealing temperature is 980~1000℃, and the heat preservation time is 90~120min.

13. The method for producing non-oriented silicon steel according to claim 12, characterized in that: In the secondary annealing process: after the insulation is completed, the cooling rate is controlled to be ≤3℃ / min.

14. The method for producing non-oriented silicon steel according to claim 12, characterized in that: In the stamping process: a series of pairs of rotor sheets and stator sheets are stamped out from the finished steel plate, and each pair of rotor sheets and stator sheets are distributed concentrically; the stator sheets enter the secondary annealing process; The production method also includes a rotor core preparation step: assembling a series of rotor sheets into a rotor core by lamination press-fitting.

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

16. The method for producing non-oriented silicon steel according to claim 9, characterized in that: In the hot rolling process: the steel billet is sent to the heating furnace for heating, the furnace entry temperature is ≥500℃, the preheating temperature is 950~1000℃, the heating and soaking temperature is 1080~1120℃ and the total heating and soaking time is 150~200min.

17. The method for producing non-oriented silicon steel according to claim 9, characterized in that: In the cold rolling process: except for the last pass, the reduction rate of each pass of the cold rolling is more than 30%.

18. The method for producing non-oriented silicon steel according to claim 9, characterized in that: In the first annealing process: the annealing temperature is 850~870℃ and kept at this temperature for 80~90s.

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