Thin-gauge non-oriented silicon steel and production method thereof as well as motor iron core and manufacturing method thereof

Abstract

The invention discloses thin-gauge non-oriented silicon steel and a production method thereof, and a motor iron core and a manufacturing method thereof. The production method comprises the following steps: heating a steel billet to 1080-1120 DEG C, preserving heat for 150-200 minutes, performing rough rolling to obtain an intermediate billet of 35-45 mm, performing finish rolling, and coiling to obtain a hot-rolled coiled plate of 2.30-3.00 mm; the initial rolling temperature of finish rolling is 970 + / -20 DEG C, the final rolling temperature is 850 + / -20 DEG C, the reduction rate is 92% or above, and the coiling temperature is 700 + / -20 DEG C; acid pickling and cold rolling are carried out under the condition that normalizing is not carried out, and cold-rolled strip steel with the thickness ranging from 0.15 mm to 0.35 mm is obtained; the total reduction rate of cold rolling is greater than or equal to 86%; performing primary annealing, cooling and coating to obtain a steel plate finished product; the annealing temperature is 830-870 DEG C, and the temperature is kept for 60-90 seconds. Therefore, the same piece of non-oriented silicon steel can meet the requirements of the stator and rotor iron cores at the same time, the manufacturing cost of the stator and rotor iron cores is low, and material waste is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of steel material preparation, and relates to a production method of thin-gauge non-oriented silicon steel for motor stator and rotor cores, and also relates to a motor core and a manufacturing method thereof. 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 a thin-gauge 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 sheet 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 motor core.

[0013] 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 process: Refining molten steel and casting the molten steel into a steel billet with a thickness of 200~240mm. After leaving the continuous casting machine, the steel billet is kept warm at a temperature range of 600~900℃ for 3~8h; the chemical composition of the steel billet includes, by mass percentage: C≤0.0025%, S≤0.0020%, Si 3.00~3.40%, Al 0.50~1.00%, Mn 0.30~0.80%, 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; Hot rolling process: 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 2.30~3.00mm; wherein, the start rolling temperature of the finish rolling is 970±20℃, the final rolling temperature is 850±20℃, the reduction rate of the finish rolling is controlled at more than 92%, and the coiling temperature is 700±20℃; Cold rolling process: the hot rolled coil is pickled and cold rolled once in sequence without normalization to obtain a cold rolled strip with a thickness of 0.15-0.35 mm; wherein the total reduction ratio of cold rolling is ≥86%; 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 830~870℃ and the temperature is kept for 60~90s.

[0014] Preferably, in the hot rolling process: the steel billet is fed into a heating furnace for heating, the furnace entry temperature is ≥450°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.

[0015] Preferably, in the cold rolling process: the first cold rolling reduction rate is 32-34%, the last cold rolling reduction rate is 20-25%, and the remaining cold rolling reduction rates are 25-30%.

[0016] Preferably, the production method further comprises, Stamping process: stamping the finished steel plate to obtain a series of thin sheets; Secondary annealing process: 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°C / min, the annealing temperature is 900~940°C, and the heat preservation time is 90~120min.

[0017] Preferably, in the secondary annealing process: after the heat preservation is completed, the cooling rate is controlled to be ≤3°C / min.

[0018] 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 concentrically distributed; the stator sheets enter the secondary annealing process to prepare the stator core; The production method also includes a rotor core preparation step: assembling a series of rotor sheets into a rotor core by lamination press-fitting.

[0019] To achieve the above-mentioned purpose, an embodiment of the present invention provides a non-oriented silicon steel, characterized in that its chemical composition includes, by mass percentage: C≤0.0025%, S≤0.0020%, Si 3.00-3.40%, Al 0.50-1.00%, Mn 0.30-0.80%, 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 0.15-0.35 mm, an average grain size of 20-40 μm, and an iron loss P 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.62T, yield strength ≥550MPa, tensile strength ≥650MPa, elongation ≥12%.

[0020] Preferably, after the secondary annealing, the average grain size of the non-oriented silicon steel is 90-120 μm, and the iron loss P is 1.0 / 400 ≤19.0W / 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 900~940°C, and the heat preservation time is 90~120min.

[0021] Preferably, the non-oriented silicon steel is a steel plate with a thickness of 0.35 mm and an iron loss P 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.64T, and after secondary annealing, its iron loss P 1.0 / 400 ≤19.0W / kg, magnetic induction intensity B 5000 ≥1.65T; Alternatively, the non-oriented silicon steel is a steel plate with a thickness of 0.30 mm and an iron loss P 1.0 / 400 ≤18.0W / kg, magnetic induction intensity B 5000 ≥1.63T, and after secondary annealing, its iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.64T; Alternatively, the non-oriented silicon steel is a steel plate with a thickness of 0.25 mm and an iron loss P of 1.0 / 400 ≤16.0W / kg, magnetic induction intensity B 5000 ≥1.63T, and after secondary annealing, its iron loss P 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.64T; Alternatively, the non-oriented silicon steel is a steel plate with a thickness of 0.20 mm and an iron loss P of 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.62T, and after secondary annealing, its iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T; Alternatively, the non-oriented silicon steel is a steel plate with a thickness of 0.15 mm and an iron loss P of 1.0 / 400 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.62T, and after secondary annealing, its iron loss P 1.0 / 400 ≤11.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0022] To achieve the above-mentioned purpose, an embodiment of the present invention provides a method for manufacturing a motor core, characterized in that the manufacturing method comprises: Stamping process: stamping the non-oriented silicon steel to obtain a series of thin sheets; Secondary annealing process: 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°C / min, the annealing temperature is 900~940°C, and the heat preservation time is 90~120min.

[0023] To achieve the above-mentioned purpose, an embodiment of the present invention provides a motor core. The motor core 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 0.15-0.35 mm, and the chemical composition includes, by mass percentage: C≤0.0025%, S≤0.0020%, Si 3.00-3.40%, Al 0.50-1.00%, Mn 0.30-0.80%, 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 20-40 μm, and the iron loss P 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.62T, yield strength ≥550MPa, tensile strength ≥650MPa, elongation ≥12%; The average grain size of the non-oriented silicon steel sheets of the laminated stator core is 90-120 μm, and the iron loss P 1.0 / 400≤19.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: the same piece of non-oriented silicon steel can meet the needs of the stator core and the rotor core at the same time. Compared with the current situation in which the non-oriented silicon steel products used for the stator core and the rotor core in the conventional technology must be prepared separately, 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, thereby avoiding the waste of materials; in addition, the design based on chemical composition, grain size, performance, etc. can also make the production process of the non-oriented silicon steel simple and easy to implement, improve the rollability, avoid the conventional normalization treatment, and save energy and reduce consumption. DETAILED DESCRIPTION

[0025] 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.

[0026] An embodiment of the present invention provides a thin-gauge 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.

[0027] The chemical composition of the non-oriented silicon steel includes, by mass percentage, C≤0.0025%, S≤0.0020%, Si3.00~3.40%, Al 0.50~1.00%, Mn 0.30~0.80%, 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.

[0028] The role of each chemical element in this embodiment is described in detail below.

[0029] 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 3.00~3.40%, and the Al content is controlled between 0.50~1.00%.

[0030] 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 steel plate. In one embodiment of the present application, the Mn content is controlled between 0.30% and 0.80%.

[0031] Nb, V, Ti, Cr, Ni, Cu: Adding Nb, V, Ti, Cr, Ni, and Cu to non-oriented silicon steel can improve 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%. 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. 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.

[0032] 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≤0.0025%, S≤0.0020%, and N≤0.0020%.

[0033] 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%.

[0034] The non-oriented silicon steel is a steel plate with a thickness of 0.15~0.35mm. In this way, this thin-gauge non-oriented silicon steel can not only directly reduce iron loss, but also cause the resistivity of the steel plate to increase, thereby indirectly reducing iron loss. Therefore, the non-oriented silicon steel of one embodiment of the present application has low iron loss.

[0035] Furthermore, the non-oriented silicon steel hot-rolled coil is pickled and cold-rolled in sequence without normalization. In this way, the fibrous metallographic structure of the hot-rolled coil is controlled by the hot rolling process, and the rollability of the steel plate is greatly improved compared with the equiaxed crystal metallographic structure after conventional normalization. As a result, the content of Si, Mn and Al can be increased to a certain extent, so as to improve the mechanical strength and reduce the iron loss from the composition; at the same time, a single cold rolling can be achieved to obtain a non-oriented silicon steel with a high alloy content of 0.15~0.35mm. Furthermore, combined with 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 terms of 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.

[0036] In one embodiment of the present application, the iron loss P of the non-oriented silicon steel is 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.62T, yield strength ≥550MPa, tensile strength ≥650MPa, elongation ≥12%.

[0037] 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.

[0038] Therefore, the non-oriented silicon steel of one embodiment of the present application can be used as the base material of the rotor core and the stator core at the same time, and can meet the needs of the stator core and the rotor core for the non-oriented silicon steel finished steel sheet after cold rolling and one-time annealing. Compared with the current situation in which the non-oriented silicon steel finished steel sheet after cold rolling used for the stator core and the non-oriented silicon steel finished steel sheet after cold rolling used for the rotor core must be prepared separately in the conventional technology, 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 sheet, the outer periphery constitutes the annular thin sheet of the stator core and the center constitutes the thin sheet of the rotor core, thereby avoiding the waste of materials. In addition, the design based on chemical composition, grain size, performance and other aspects can also make the production process of the non-oriented silicon steel simple and easy to implement, improve the rollability, avoid the conventional normalizing treatment, and save energy and reduce consumption.

[0039] In one embodiment, the average grain size of the non-oriented silicon steel is 20-40 μm.

[0040] Furthermore, in one embodiment of the present application, the non-oriented silicon steel has an average grain size of 90-120 μm and an iron loss P of 90-120 μm after secondary annealing based on the chemical composition, thickness, average grain size and performance. 1.0 / 400 ≤19.0W / 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.

[0041] In the secondary annealing treatment, the heating rate is ≤5°C / min, the annealing temperature is 900-940°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.

[0042] In addition, the structure of the non-oriented silicon steel is a completely recrystallized structure, that is, the proportion of recrystallized grains is 100%.

[0043] In one embodiment, the non-oriented silicon steel is a steel plate with a thickness of 0.35 mm and an iron loss P of 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.64T, and after the above secondary annealing treatment, its iron loss P 1.0 / 400 ≤19.0W / kg, magnetic induction intensity B 5000 ≥1.65T.

[0044] Alternatively, in a variation, the non-oriented silicon steel is a steel plate with a thickness of 0.30 mm and an iron loss P of 1.0 / 400≤18.0W / kg, magnetic induction intensity B 5000 ≥1.63T, and after the above secondary annealing treatment, its iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.64T; Alternatively, in another embodiment, the non-oriented silicon steel is a steel plate with a thickness of 0.25 mm and an iron loss P of 1.0 / 400 ≤16.0W / kg, magnetic induction intensity B 5000 ≥1.63T, and after the above secondary annealing treatment, its iron loss P 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.64T; Alternatively, in another embodiment, the non-oriented silicon steel is a steel plate with a thickness of 0.20 mm and an iron loss P of 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.62T, and after the above secondary annealing treatment, its iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T; Alternatively, in another variation, the non-oriented silicon steel is a steel plate with a thickness of 0.15 mm and an iron loss P of 1.0 / 400 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.62T, and after the above secondary annealing treatment, its iron loss P 1.0 / 400 ≤11.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

[0045] Furthermore, an embodiment also provides a method for producing the non-oriented silicon steel, which produces the non-oriented silicon steel product mentioned above through a process route of steelmaking, hot rolling, cold rolling, and primary annealing.

[0046] The following is a detailed introduction to each process.

[0047] <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.

[0048] 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 of the non-oriented silicon steel introduced above. For example, the chemical composition of the steel billet includes, by mass percentage: C≤0.0025%, S≤0.0020%, Si 3.00~3.40%, Al 0.50~1.00%, Mn 0.30~0.80%, 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.

[0049] In this way, the present application can control the metallographic structure of the hot-rolled plate to be a fibrous metallographic structure through the design and control of the chemical composition, combined with the subsequent hot rolling process, which significantly improves the toughness of the conventional equiaxed crystal metallographic structure after normalization, laying the foundation for the subsequent realization of a single cold rolling without normalization, and creating conditions for the subsequent realization of the high strength requirements of non-oriented silicon steel for the rotor core of the electric vehicle drive motor and the low iron loss requirements of non-oriented silicon steel for the stator core.

[0050] 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.

[0051] 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.

[0052] 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 the subsequent cold rolling, primary annealing and high-temperature secondary annealing without normalization and preheating.

[0053] <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 2.30~3.00mm.

[0054] Among them, the starting rolling temperature of the finishing rolling is 970±20℃, the final rolling temperature is 850±20℃, and the coiling temperature is 700±20℃.

[0055] In this way, on the basis of chemical composition, by controlling the heating temperature, the solid solution of coarse precipitates (MnS, AlN) in the ingot can be avoided, creating conditions for the control of subsequent organizational properties, and further combined with the control of finishing deformation, temperature and coiling temperature, a hot-rolled coil with a fibrous metallographic structure can be obtained, which has significantly improved toughness than the conventional equiaxed crystal metallographic structure after normalization, laying the foundation for the subsequent cold rolling without normalization, and creating conditions for the precise control of the recrystallization process and grain size during the primary annealing and high-temperature secondary annealing.

[0056] Preferably, in the hot rolling process: the steel billet is sent to a heating furnace for heating, the furnace entry temperature is ≥ 450°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 minutes. In this way, in addition to meeting the lower heating temperature introduced 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.

[0057] <Cold rolling process> In this process, the hot-rolled coil is pickled and cold-rolled once in sequence without normalization to obtain a cold-rolled strip with a thickness of 0.15-0.35 mm.

[0058] In this process, the total cold rolling reduction ratio is ≥86%.

[0059] In this way, on the basis of the previous hot rolling, combined with the large reduction rate of cold rolling, a large number of dislocation defects are provided for the cold-rolled strip, which is conducive to a large number of nucleations during the primary annealing, forming a fine-grained structure with high strength, and then the high strength requirements of non-oriented silicon steel for the rotor core of new energy high-speed motors are achieved with the help of the subsequent primary annealing, and the foundation is laid for achieving the low iron loss requirements of non-oriented silicon steel for the stator core through the subsequent secondary annealing process.

[0060] Preferably, in this process, the first pass reduction rate of cold rolling is 32-34%, the last pass reduction rate is 20-25%, and the remaining pass reduction rates are 25-30%. In this way, not only can the high silicon and high aluminum steel be directly cold rolled without preheating with the help of the hot rolled fiber metallographic structure, but also the cold rolling stability and plate shape quality can be effectively guaranteed. Of course, the present application is not limited to this.

[0061] In addition, in this process, the specific operation of pickling can be implemented in a feasible manner known in the art and is not limited in this application.

[0062] <Primary Annealing Process> In this process, the cold-rolled strip is annealed, cooled and coated once to obtain a non-oriented silicon steel product.

[0063] The annealing temperature is 830~870℃ and kept for 60~90s to control the steel plate to complete full recrystallization. Compared with the same level of high silicon and high aluminum steel, the annealing temperature is 100~200℃ lower, ensuring fine grains after the first annealing, achieving the high strength requirements of non-oriented silicon steel for rotor cores of new energy high-speed motors, and creating conditions for subsequent secondary annealing.

[0064] Specifically, on the basis of the previous hot rolling and 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 20-40 μm, 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.

[0065] During the primary annealing, a weak reducing protective atmosphere may be used, for example, a protective atmosphere of N2 and H2, wherein the volume percentage of H2 is 20-30% and the remainder is N2.

[0066] Furthermore, the production method also includes a stamping process and a secondary annealing process located after the primary annealing process; and from another perspective, the stamping and secondary annealing process is a process of using the non-oriented silicon steel finished product to manufacture a motor core, that is, one embodiment also provides a method for manufacturing a motor core.

[0067] The stamping process and secondary annealing process are introduced in detail below.

[0068] <Pressing process> In this process, the non-oriented silicon steel (or the non-oriented silicon steel product obtained in the primary annealing process) is punched to obtain a series of thin sheets.

[0069] <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.

[0070] Among them, during the secondary annealing: the heating rate is ≤5°C / min, the annealing temperature is 900~940°C, and the insulation time is 90~120min.

[0071] In this way, the non-oriented silicon steel obtained by stamping, lamination and secondary annealing or lamination after secondary annealing has a significant grain growth compared to the non-oriented silicon steel product before stamping. For example, the average grain size of recrystallization grows from 20~40μm to 90~120μm, so that the non-oriented silicon steel obtained after secondary annealing has lower iron loss, thereby producing a non-oriented silicon steel core with low iron loss.

[0072] 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.

[0073] 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.

[0074] Furthermore, in one embodiment, in the stamping process, a series of pairs of rotor sheets and stator sheets can be stamped out from the non-oriented silicon steel product, and each pair of rotor sheets and stator sheets are concentrically distributed.

[0075] The stator slices enter the secondary annealing process to prepare a stator core.

[0076] The rotor sheets then enter the rotor core preparation process, which specifically includes: assembling a series of rotor sheets into a rotor core by lamination press-fitting.

[0077] 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.

[0078] As mentioned above, in the first annealing process, the thickness of the non-oriented silicon steel product obtained is 0.15-0.35 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 0.15-0.35 mm.

[0079] In one embodiment, after the heat preservation of the secondary annealing is completed, the cooling rate can be controlled to be ≤3° C. / min.

[0080] For example, in an embodiment of performing secondary annealing on stator core laminations, the stator core laminations may 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 may 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.

[0081] It is understandable that in this application, the order of operations of each process is not limited by the order in which the technology is introduced. For example, the implementation order of the "rotor core preparation process" and the "stator core preparation process" can occur simultaneously, or the rotor core preparation process can be performed first and then the stator core preparation process, or the stator core preparation process can be performed first and then the rotor core preparation process; for another example, the "stamping process" can be performed completely before the "rotor core preparation process" and the "stator core preparation process", or it can be performed 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.

[0082] Furthermore, an embodiment of the present application also provides a motor core, which includes a laminated rotor core and a laminated stator core.

[0083] The laminated rotor core and the laminated stator core can be made of the non-oriented silicon steel mentioned above, respectively, and the specific preparation process can adopt the manufacturing method or the production method mentioned above.

[0084] 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.

[0085] The average grain size of the non-oriented silicon steel sheets of the laminated rotor core is 20-40 μm, and the iron loss P 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.62T, yield strength ≥550MPa, tensile strength ≥650MPa, elongation ≥12%. 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.

[0086] The average grain size of the non-oriented silicon steel sheets of the laminated stator core is 90-120 μm, and the iron loss P 1.0 / 400 ≤19.0W / kg, magnetic induction intensity B5000 ≥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.

[0087] Specifically, in one embodiment, the non-oriented silicon steel sheets of the laminated rotor core and the laminated stator core are both steel plates with a thickness of 0.35 mm, and the iron loss P of the laminated rotor core is 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.64T, iron loss P of laminated stator core 1.0 / 400 ≤19.0W / kg, magnetic induction intensity B 5000 ≥1.65T.

[0088] Alternatively, in a variation, the non-oriented silicon steel sheets of the laminated rotor core and the laminated stator core are both steel plates with a thickness of 0.30 mm, and the iron loss P of the laminated rotor core is 1.0 / 400 ≤18.0W / kg, magnetic induction intensity B 5000 ≥1.63T, iron loss P of laminated stator core 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.64T; Alternatively, in another embodiment, the non-oriented silicon steel sheets of the laminated rotor core and the laminated stator core are both steel plates with a thickness of 0.25 mm, and the iron loss P of the laminated rotor core is 1.0 / 400 ≤16.0W / kg, magnetic induction intensity B 5000 ≥1.63T, iron loss P of laminated stator core 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.64T; Alternatively, in another embodiment, the non-oriented silicon steel sheets of the laminated rotor core and the laminated stator core are both steel plates with a thickness of 0.20 mm, and the iron loss P of the laminated rotor core is 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.62T, iron loss P of laminated stator core 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T; Alternatively, in another variation, the non-oriented silicon steel sheets of the laminated rotor core and the laminated stator core are both steel plates with a thickness of 0.15 mm, and the iron loss P of the laminated rotor core is 1.0 / 400 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.62T, iron loss P of laminated stator core 1.0 / 400 ≤11.0W / 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 product, 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 production methods of each non-oriented silicon steel finished product are as follows: (1) preparing molten steel and casting the molten steel into billets with chemical composition as shown in Table 1. After leaving the continuous casting machine, the billets are kept at a temperature range of 600-900°C for 3-8 hours; (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 thickness of the steel billet, heating temperature, holding time, thickness of the intermediate billet, start rolling temperature of finish rolling, final rolling temperature, coiling temperature and thickness of the hot-rolled coil are shown in Table 2 respectively; [Table 2]

[0094] (3) The hot rolled coil is pickled and cold rolled in sequence without normalization to obtain a cold rolled strip; and then annealed, cooled and coated to obtain a finished steel plate; wherein the thickness, primary annealing temperature and holding time of the cold rolled strip are shown in Table 3; The performance tests were carried out on the finished steel plates of each embodiment, including: using GB / T 228.1-2021 "Tensile test of metallic materials Part 1 Room temperature test method" standard to test the tensile strength Rm, yield strength Re and elongation δ; using GB / T3655-2008 "Method for measuring magnetic properties of electrical steel sheets (strips) using Epstein square rings" national standard to test 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 3.

[0095] [Table 3]

[0096] (4) The finished steel sheets of each embodiment were subjected to stamping and secondary annealing, with a heating rate of ≤5°C / min, an annealing temperature of 900-940°C, and a heat preservation time of 90-120min. After the stamping, the non-oriented silicon steel sheets were subjected to performance testing, including: using GB / T 3655-2008 "Method for measuring magnetic properties of electrical steel sheets (strips) using Epstein square rings" national standard 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 4.

[0097] [Table 4]

[0098] It can be seen from Table 3 and Table 4 that in the present application, the non-oriented silicon steel product has high mechanical strength, and when applied to the preparation of the rotor core, it can meet the rotor core's demand for high strength; at the same time, after the secondary annealing of the non-oriented silicon steel product, the coarsening of the grains can be achieved, so that the obtained secondary annealed steel plate has the characteristics of low iron loss, which meets the high requirements of the stator core in terms of low iron loss; that is, the non-oriented silicon steel plate of the present application can not only meet the rotor core's requirements 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, 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 non-oriented silicon steel finished steel plate that is annealed once after cold rolling.

Claims

1. A method for producing non-oriented silicon steel, characterized in that: The production method comprises, Steelmaking process: Refining molten steel and casting the molten steel into a steel billet with a thickness of 200~240mm. After leaving the continuous casting machine, the steel billet is kept warm at a temperature range of 600~900℃ for 3~8h; the chemical composition of the steel billet includes, by mass percentage: C≤0.0025%, S≤0.0020%, Si 3.00~3.40%, Al 0.50~1.00%, Mn 0.30~0.80%, 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; Hot rolling process: 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 2.30~3.00mm; wherein, the start rolling temperature of the finish rolling is 970±20℃, the final rolling temperature is 850±20℃, the reduction rate of the finish rolling is controlled at more than 92%, and the coiling temperature is 700±20℃; Cold rolling process: the hot rolled coil is pickled and cold rolled once in sequence without normalization to obtain a cold rolled strip with a thickness of 0.15-0.35 mm; wherein the total reduction ratio of cold rolling is ≥86%; 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 830~870℃ and the temperature is kept for 60~90s.

2. The method for producing non-oriented silicon steel according to claim 1, characterized in that: In the hot rolling process: the steel billet is sent to the heating furnace for heating, the furnace entry temperature is ≥450℃, the preheating temperature is 950~1000℃, the heating and soaking temperature is 1080~1120℃ and the total heating and soaking time is 150~200min.

3. The method for producing non-oriented silicon steel according to claim 1, characterized in that: In the cold rolling process: the first pass reduction rate of cold rolling is 32~34%, the last pass reduction rate is 20~25%, and the remaining passes reduction rate is 25~30%.

4. The method for producing non-oriented silicon steel according to claim 1, characterized in that: The production method further comprises, Stamping process: stamping the finished steel plate to obtain a series of thin sheets; Secondary annealing process: 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°C / min, the annealing temperature is 900~940°C, and the heat preservation time is 90~120min.

5. The method for producing non-oriented silicon steel according to claim 4, characterized in that: In the secondary annealing process: after the insulation is completed, the cooling rate is controlled to be ≤3℃ / min.

6. The method for producing non-oriented silicon steel according to claim 4, 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 to prepare the stator core; The production method also includes a rotor core preparation step: assembling a series of rotor sheets into a rotor core by lamination press-fitting.

7. A non-oriented silicon steel, characterized in that: Its chemical composition includes by mass percentage: C≤0.0025%, S≤0.0020%, Si 3.00~3.40%, Al 0.50~1.00%, Mn 0.30~0.80%, 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 0.15-0.35 mm, an average grain size of 20-40 μm, and an iron loss P 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.62T, yield strength ≥550MPa, tensile strength ≥650MPa, elongation ≥12%.

8. The non-oriented silicon steel according to claim 7, characterized in that: After secondary annealing, the non-oriented silicon steel has an average grain size of 90-120 μm and an iron loss of 1.0 / 400 ≤19.0W / 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 900~940°C, and the heat preservation time is 90~120min.

9. The non-oriented silicon steel according to claim 7, characterized in that: The non-oriented silicon steel is a steel plate with a thickness of 0.35 mm and an iron loss P 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.64T, and after secondary annealing, its iron loss P 1.0 / 400 ≤19.0W / kg, magnetic induction intensity B 5000 ≥1.65T; Alternatively, the non-oriented silicon steel is a steel plate with a thickness of 0.30 mm and an iron loss P 1.0 / 400 ≤18.0W / kg, magnetic induction intensity B 5000 ≥1.63T, and after secondary annealing, its iron loss P 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.64T; Alternatively, the non-oriented silicon steel is a steel plate with a thickness of 0.25 mm and an iron loss P of 1.0 / 400 ≤16.0W / kg, magnetic induction intensity B 5000 ≥1.63T, and after secondary annealing, its iron loss P 1.0 / 400 ≤13.0W / kg, magnetic induction intensity B 5000 ≥1.64T; Alternatively, the non-oriented silicon steel is a steel plate with a thickness of 0.20 mm and an iron loss P of 1.0 / 400 ≤15.0W / kg, magnetic induction intensity B 5000 ≥1.62T, and after secondary annealing, its iron loss P 1.0 / 400 ≤12.0W / kg, magnetic induction intensity B 5000 ≥1.63T; Alternatively, the non-oriented silicon steel is a steel plate with a thickness of 0.15 mm and an iron loss P of 1.0 / 400 ≤14.0W / kg, magnetic induction intensity B 5000 ≥1.62T, and after secondary annealing, its iron loss P 1.0 / 400 ≤11.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

10. A method for manufacturing a motor core, characterized in that: The manufacturing method comprises: Stamping process: stamping the non-oriented silicon steel according to claim 7 to obtain a series of thin sheets; Secondary annealing process: 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°C / min, the annealing temperature is 900~940°C, and the heat preservation time is 90~120min.

11. The method for manufacturing a motor core according to claim 10, characterized in that: In the secondary annealing process: after the insulation is completed, the cooling rate is controlled to be ≤3℃ / min.

12. The method for manufacturing a motor core according to claim 10, characterized in that: In the stamping process: a series of pairs of rotor sheets and stator sheets are stamped out from the non-oriented silicon steel, and each pair of rotor sheets and stator sheets are distributed concentrically; the stator sheets enter the secondary annealing process to prepare a stator core; The manufacturing method also includes a rotor core preparation step: assembling a series of rotor sheets into a rotor core by lamination press-fitting.

13. A motor core, 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 0.15-0.35 mm, and the chemical composition includes, by mass percentage: C≤0.0025%, S≤0.0020%, Si 3.00-3.40%, Al 0.50-1.00%, Mn0.30-0.80%, 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 20-40 μm, and the iron loss P 1.0 / 400 ≤22.0W / kg, magnetic induction intensity B 5000 ≥1.62T, yield strength ≥550MPa, tensile strength ≥650MPa, elongation ≥12%; The average grain size of the non-oriented silicon steel sheets of the laminated stator core is 90-120 μm, and the iron loss P 1.0 / 400 ≤19.0W / kg, magnetic induction intensity B 5000 ≥1.63T.

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