Non-oriented electrical steel for electric vehicle drive motor and method of manufacturing the same

Abstract

This invention discloses a non-oriented electrical steel for electric vehicle drive motors, which contains Fe and unavoidable impurities, and also contains the following chemical elements in the following mass percentages: C ≤ 0.003%, Si: 3.0-4.5%, Al: 0.15-2.5%, Mn: 0.15-2.5%; the magnetic induction intensity B of the non-oriented electrical steel for electric vehicle drive motors is... 50M ≥1.60T, of which B 50M = (B 50L +B 50C +2B 50X ) / 4, where B 50L B represents the magnetic flux density in the rolling direction when magnetized in a magnetic field of 5000 A / m. 50C B represents the magnetic flux density perpendicular to the rolling direction when magnetized in a magnetic field of 5000 A / m; 50X This refers to the minimum magnetic induction intensity at an angle different from the rolling direction when magnetized in a magnetic field of 5000 A / m. Accordingly, the present invention also discloses a method for manufacturing the above-mentioned non-oriented electrical steel.

Description

Technical Field

[0001] This invention relates to a steel plate and a method for manufacturing the same, and more particularly to a non-oriented electrical steel plate and a method for manufacturing the same. Background Technology

[0002] In recent years, with increasing attention paid to carbon emission reduction, environmental protection and energy conservation by countries around the world, traditional gasoline-powered cars are gradually being replaced by electric vehicles. The market and users' demand for electric vehicles is also growing, and more and more car companies are investing in the production and research and development of electric vehicles.

[0003] Currently, in order to obtain more competitive electric vehicles, many car manufacturers are constantly raising the requirements for the drive motors of electric vehicles. They require the drive motors to have the characteristics of miniaturization, high power density, and high speed, while the operating frequency range has reached 400Hz to several kilohertz.

[0004] To meet these requirements for drive motors, non-oriented silicon steel, used as the core material, needs to possess high frequency and low iron loss characteristics to ensure high-efficiency energy conversion. Furthermore, the non-oriented silicon steel also needs to have sufficiently high strength to ensure that the motor rotor does not deform or break during high-speed rotation. Additionally, the non-oriented silicon steel must possess excellent magnetic induction intensity to meet the high torque requirements during motor start-up or acceleration. Besides requiring excellent longitudinal (rolling direction) and transverse (perpendicular to the rolling direction) magnetic induction intensity, the magnetic properties in other directions, especially the direction of magnetic minimum, also have a significant impact on motor performance; that is, it is desirable that the magnetic induction intensity in the direction of magnetic minimum is also excellent.

[0005] To address this need, some researchers have conducted extensive research and achieved certain results, but the practical application effects have not been ideal.

[0006] For example, Chinese patent document CN106435358A, published on February 22, 2017, entitled "A Manufacturing Method of High-Strength Non-Oriented Silicon Steel for New Energy Vehicle Drive Motors," discloses a method for producing high-strength non-oriented silicon steel for new energy vehicle drive motors. This method employs thin-strip continuous casting and low-temperature annealing processes, strengthening the steel through NbC precipitation and fine-grained microstructure, resulting in non-oriented silicon steel with a yield strength of 600-780 MPa. However, the high-frequency iron loss in the non-oriented silicon steel sheet obtained by this technical solution is relatively high, with P at 400 Hz... 10 / 400 The iron loss has reached 28.0-38.2 W / kg, and it will increase further at 600 Hz. At the same time, there are no reports on the control of magnetic anisotropy.

[0007] For example, Chinese patent document CN111471941A, published on July 31, 2020, entitled "A High-Strength Non-Oriented Silicon Steel for the Rotor of a New Energy Vehicle Drive Motor with a Yield Strength of 600MPa and Its Manufacturing Method," discloses a high-strength non-oriented silicon steel. Its chemical composition (wt%) is: Si: 2.8%-3.5%, Mn: 0.35%-0.65%, Als: 0.50%-0.80%. It is strengthened by adding any two elements from Cr, Nb, Ti, Ni, and V, with a content ranging from 0.05% to 0.55%. This technical solution achieves a yield strength exceeding 600MPa by enhancing the {111} surface texture, but its iron loss P10 / 400 is as high as 22.6-30.4W / kg. At a higher frequency of 600Hz, the loss will be even higher.

[0008] Based on this, unlike the existing technical solutions mentioned above, the inventors designed and expect to obtain a new type of non-oriented electrical steel for electric vehicle drive motors and its manufacturing method to meet the needs of the market and users. Summary of the Invention

[0009] One objective of this invention is to provide a non-oriented electrical steel for electric vehicle drive motors. This non-oriented electrical steel for electric vehicle drive motors features high strength, high frequency and low iron loss, high magnetic induction intensity, and low magnetic anisotropy, exhibiting promising prospects and application value. Using this non-oriented electrical steel for electric vehicle drive motors can effectively manufacture drive motors for new energy vehicles and effectively meet market requirements for high speed, miniaturization, and high torque in electric vehicle drive motors.

[0010] To achieve the above objectives, this invention provides a non-oriented electrical steel for electric vehicle drive motors, which contains Fe and unavoidable impurities, and also contains the following chemical elements in the following mass percentages:

[0011] C≤0.003%, Si: 3.0-4.5%, Al: 0.15-2.5%, Mn: 0.15-2.5%;

[0012] The magnetic induction intensity B of the non-oriented electrical steel used in the electric vehicle drive motor 50M ≥1.60T, of which B 50M = (B 50L +B 50C +2B 50X ) / 4, where B 50L B represents the magnetic flux density in the rolling direction when magnetized in a magnetic field of 5000 A / m. 50C B represents the magnetic flux density perpendicular to the rolling direction when magnetized in a magnetic field of 5000 A / m; 50XThis represents the minimum magnetic induction intensity at an angle different from the rolling direction when magnetized in a magnetic field of 5000 A / m.

[0013] Furthermore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, the mass percentage content of each chemical element is as follows:

[0014] C ≤ 0.003%, Si: 3.0-4.5%, Al: 0.15-2.5%, Mn: 0.15-2.5%; balance is Fe and unavoidable impurities.

[0015] The design principles of each chemical element in the non-oriented electrical steel for electric vehicle drive motors described in this invention are as follows:

[0016] C: In the non-oriented electrical steel for electric vehicle drive motors described in this invention, element C is an impurity element, which is harmful to the magnetism of non-oriented silicon steel. Therefore, the content of element C must be strictly controlled at 0.003% or below, that is, the element C in the steel must be controlled to satisfy: C≤0.003%.

[0017] Of course, in some implementations, in order to obtain better implementation results, the mass percentage content of element C can be further preferably controlled as follows: C≤0.002%.

[0018] Si: In the non-oriented electrical steel for electric vehicle drive motors described in this invention, adding an appropriate amount of Si can increase the resistivity of the non-oriented electrical steel sheet and reduce iron loss; at the same time, Si, as a solid solution strengthening element, can also improve the strength of the steel sheet. Therefore, in order to exert the beneficial effects of Si and enable the steel to obtain high yield strength, high frequency and low iron loss properties, the Si content in the steel needs to be greater than 3.0%. However, it should be noted that the Si content in the steel should not be too high. When the Si content in the steel exceeds 4.5%, the ordered phase Fe3Si or FeSi will appear, and the room temperature plasticity of the material will deteriorate sharply, making it impossible to carry out large-scale industrial cold rolling production. At the same time, the magnetic induction intensity will also deteriorate. Based on this, considering the influence of Si content on the performance of steel, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, the mass percentage of Si is controlled between 3.0% and 4.5%.

[0019] Al: In the non-oriented electrical steel for electric vehicle drive motors described in this invention, Al is also an effective element for increasing resistivity and reducing iron loss. Considering the role of this element in improving iron loss, more than 0.15% Al needs to be added to the steel. However, the Al content in the steel should not be too high. Adding excessive Al will be detrimental to the magnetic induction strength of the steel, cause difficulties in steelmaking and casting, and lead to a deterioration in the cold working performance of the steel plate. Therefore, the amount of Al added to the steel should not exceed 2.5%. Based on this, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, the mass percentage content of Al is controlled between 0.15% and 2.5%.

[0020] Mn: In the non-oriented electrical steel for electric vehicle drive motors described in this invention, Mn can increase the resistivity of the steel. Simultaneously, Mn can react with S to form MnS, thereby improving the electromagnetic properties of the steel. Therefore, to maximize the beneficial effects of Mn, it is necessary to add more than 0.1% Mn to the steel. However, it should be noted that the Mn content in the steel should not be too high. When the Mn content exceeds 2.5%, it will reduce the plasticity of the steel and lead to cold-rolled strip breakage. Based on this, to maximize the beneficial effects of Mn, the mass percentage of Mn in the non-oriented electrical steel for electric vehicle drive motors described in this invention is controlled between 0.15% and 2.5%.

[0021] The non-oriented electrical steel for electric vehicle drive motors designed in this invention possesses high strength, high frequency, low iron loss, and high magnetic induction intensity, while also exhibiting low magnetic anisotropy. Its yield strength is ≥440MPa, and its iron loss P... 10 / 600 ≤30W / kg, and magnetic induction intensity B 50M ≥1.60T.

[0022] Regarding iron loss, as the drive motors of new energy electric vehicles continue to develop towards miniaturization and high efficiency, the high-frequency iron loss of non-oriented electrical steel is required to be as low as possible. Therefore, this invention exhibits low iron loss, with iron loss P under the conditions of magnetic flux density 1.0T and frequency 600Hz. 10 / 600 ≤30W / kg.

[0023] Regarding yield strength, the rotor of the drive motor for electric vehicles must possess high reliability under high-speed operation, especially at speeds exceeding 15,000 rpm. The core material needs to have sufficiently high strength to ensure that the material does not deform or fracture. Therefore, this invention designs a high yield strength, specifically controlling the yield strength to ≥440 MPa.

[0024] Regarding magnetic induction intensity, the direction of excitation of the steel plate changes continuously during the operation of the drive motor of an electric vehicle. In motor design, for the non-oriented electrical steel used, in addition to requiring excellent magnetic induction intensity in the longitudinal (rolling direction) and transverse (perpendicular to the rolling direction), the magnetic induction intensity in other directions, especially the direction of magnetic minimum, also has an important impact on the performance of the motor.

[0025] Therefore, in this invention, when designing this non-oriented electrical steel for electric vehicle drive motors, the magnetic induction intensity B of the steel is specifically designed. 50M ≥1.60T, and the designed magnetic induction intensity B is limited. 50M = (B 50L +B 50C +2B 50X ) / 4.

[0026] Furthermore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, C ≤ 0.002%.

[0027] Furthermore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, the unavoidable impurities are P≤0.03%, S≤0.003%, N≤0.005%, and O≤0.0030%.

[0028] In the non-oriented electrical steel for electric vehicle drive motors described in this invention, P, S, N and O are all impurity elements in the non-oriented electrical steel sheet. Where technical conditions permit, in order to obtain steel with better performance and higher quality, the content of impurity elements in the steel should be reduced as much as possible.

[0029] P: In this invention, P is a grain boundary segregating element. For a composition system with Si ≥ 3.0%, if the content of impurity element P in the steel exceeds 0.03%, it will exacerbate the brittleness of the electrical steel sheet and make it difficult to roll. Therefore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, the mass percentage content of P element is controlled to be P ≤ 0.03%. Of course, in some preferred embodiments, it can be further controlled to be P ≤ 0.02%.

[0030] S: In this invention, S is a magnetically detrimental element that combines with Mn to form fine MnS, thereby hindering grain growth during annealing and degrading the magnetic properties of the steel sheet. Therefore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, the mass percentage content of S element is controlled to be: S≤0.003%.

[0031] N: In this invention, N is a magnetically detrimental element that forms fine nitrides with elements such as Al, Ti, Nb, and V, hindering grain growth. Therefore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, the mass percentage content of N is controlled to be N ≤ 0.005%. Of course, in some preferred embodiments, it can be further controlled to N ≤ 0.0035%.

[0032] O: In this invention, O is a harmful element. For a composition system with Si ≥ 3.0%, the cold working performance of the material is very sensitive to the segregation of oxygen at grain boundaries. At the same time, the formed oxides such as silicon, aluminum, and manganese will also degrade the magnetic properties of the material. Therefore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, the mass percentage content of O element is controlled to be O ≤ 0.0030%.

[0033] Furthermore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, P ≤ 0.02% and N ≤ 0.0035% are present in unavoidable impurities.

[0034] Furthermore, the non-oriented electrical steel for electric vehicle drive motors described in this invention also contains B: 0.0005%-0.010%.

[0035] In the above-mentioned technical solution of the present invention, in order to further optimize the performance of the non-oriented electrical steel for electric vehicle drive motor, an appropriate amount of B element can preferably be added to the steel.

[0036] B: In the non-oriented electrical steel for electric vehicle drive motors described in this invention, B is a grain boundary strengthening element, which can enhance the grain boundary bonding ability of high-silicon content systems, thereby improving the cold rolling processing performance of the material. However, it should be noted that an appropriate amount of B needs to be added to the steel. When B is added in excess, it will refine the grain structure and is detrimental to magnetic properties; therefore, the content should not exceed 0.010%. When the B content in the steel is less than 0.0005%, it will not play a grain boundary strengthening role. Therefore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, it is preferable to control the addition of 0.0005%-0.010% of B.

[0037] Furthermore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, it also contains at least one of Co, Ni, Sn, Sb, Cu, and Cr, and the total mass percentage of these elements is controlled between 0.020 and 4.0%.

[0038] In the above technical solution of the present invention, the non-oriented electrical steel for electric vehicle drive motor designed may further preferably contain elements of Co, Ni, Sn, Sb, Cu, and Cr.

[0039] Sn and Sb are both grain boundary segregation elements. On the one hand, they can hinder the diffusion of trace oxygen along grain boundaries during the normalizing annealing process of hot-rolled plates, preventing oxidation and plasticity deterioration within the steel plate. On the other hand, they can improve the magnetically favorable textures such as the {100} surface texture and Goss texture during the annealing process of finished plates. Co, Ni, Cu, Cr, and other elements can play a role in solid solution strengthening, while also increasing the resistivity of the material and improving the iron loss performance of the steel.

[0040] Therefore, to achieve the aforementioned beneficial effects, in this invention, it is preferable to control the addition of at least one of Co, Ni, Sn, Sb, Cu, and Cr, and to control the total mass percentage of these elements to be above 0.020%. When the total mass percentage of these elements exceeds 4%, their improving effect tends to saturate, and manufacturing costs increase; therefore, the upper limit of the total mass percentage of these elements should not exceed 4%.

[0041] Furthermore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, its thickness is 0.1–0.3 mm.

[0042] In the above technical solution of the present invention, the thickness of the non-oriented electrical steel for the finished electric vehicle drive motor can preferably be controlled between 0.10-0.30mm. This is because: by reducing the thickness, the eddy current loss in high-frequency iron loss can be effectively reduced, so the thickness of the finished steel plate is preferably below 0.30mm; in addition, from the perspective of the manufacturing efficiency of the drive motor, when the steel plate used is too thin, the production efficiency will be reduced, so the thickness of the finished steel plate is specifically controlled above 0.10mm.

[0043] Furthermore, in the non-oriented electrical steel for electric vehicle drive motors described in this invention, its yield strength is ≥440MPa, and its iron loss P 10 / 600 ≤30W / kg.

[0044] Accordingly, another objective of the present invention is to provide a manufacturing method for the non-oriented electrical steel for electric vehicle drive motors described above. This manufacturing method is simple and feasible, and can produce non-oriented electrical steel sheets with excellent mechanical and electromagnetic properties.

[0045] To achieve the above-mentioned objectives, this invention proposes a method for manufacturing non-oriented electrical steel for electric vehicle drive motors, comprising the following steps:

[0046] (1) Obtain the casting billet;

[0047] (2) Hot rolling: The thickness of the hot-rolled plate is controlled to be 1.5 to 2.2 mm;

[0048] (3) Normalizing annealing: Control the normalizing annealing temperature to 820℃-950℃;

[0049] (4) Cold rolling;

[0050] (5) Continuous annealing is carried out in a continuous annealing furnace;

[0051] (6) Insulating coating.

[0052] In this invention, the inventors optimized the chemical composition design of the steel and defined a reasonable manufacturing process. After the continuous casting billet is prepared according to the designed chemical composition, it needs to go through hot rolling, normalizing annealing, cold rolling (for example, it can be a single cold rolling or a double cold rolling with intermediate annealing), final continuous annealing, and coating with an insulating coating in sequence to effectively prepare the non-oriented electrical steel for electric vehicle drive motors with excellent comprehensive performance designed in this invention. It can be effectively used to prepare electric vehicle drive motors and has the characteristics of high strength, high frequency and low iron loss, high magnetic induction intensity, and small magnetic anisotropy.

[0053] In the hot rolling process of step (2) of the present invention, the thickness of the hot-rolled steel coil needs to be controlled between 1.5 mm and 2.2 mm to obtain a thin-gauge hot-rolled plate. This is because: by reducing the thickness of the hot-rolled plate, the cold rolling reduction rate can be reduced, which can improve the texture composition of the cold-rolled plate and reduce the unfavorable texture strength of the γ-fiber texture. However, it should be noted that the hot-rolled plate cannot be too thin, otherwise it will lead to increased production difficulty and poor plate shape, which is not conducive to the control of plate differences. Therefore, the thickness of the hot-rolled steel coil needs to be controlled above 1.5 mm.

[0054] Accordingly, in the normalizing annealing process of step (3) of the present invention, the hot-rolled steel coil can be transported to a horizontal continuous annealing furnace for normalizing annealing treatment, and the normalizing annealing temperature is strictly controlled between 820℃ and 950℃. Through normalizing treatment, the magnetic induction intensity of the finished product can be improved, but the temperature cannot be too low, otherwise the magnetic induction intensity will not achieve the improvement effect. Therefore, the present invention controls the normalizing annealing temperature to be above 820℃. In addition, from the perspective of machinability, for high silicon content systems, especially normalized plates with Si+Al content exceeding 4.5%, the grain size of the steel plate is too large, and it is easy to break the strip during cold rolling, making it difficult to produce. Therefore, in the present invention, the normalizing annealing temperature is specifically controlled not to exceed 950℃, and the holding time can preferably be controlled not to exceed 3 minutes.

[0055] Furthermore, in the manufacturing method described in this invention, in step (3), the unit tension F of the strip in the annealing furnace is controlled to satisfy the following relationship: 1.5≤F≤(3.8+0.3d) / ([Si]). 2 ×T), where d is the thickness of the hot-rolled plate (in mm), T is the normalizing annealing temperature (in °C), [Si] is the mass percentage of silicon in the hot-rolled coil (in %), and F is in N / mm². 2 .

[0056] In the above-mentioned technical solution of the present invention, by controlling the small tension in the annealing furnace, it is possible to promote the uniform recrystallization, nucleation, and growth of grains in each orientation of the strip during the annealing process, thereby improving the magnetic properties in other directions, reducing magnetic anisotropy, and thus obtaining a high magnetic induction intensity B. 50M .

[0057] In this invention, the set range of the unit tension F value of the strip in the annealing furnace is related to the silicon content [Si] of the steel, the normalizing annealing temperature T, and the hot-rolled plate thickness d. Specifically, the higher the Si content [Si] in the steel, the higher the normalizing annealing temperature T, and the thinner the hot-rolled plate thickness d, the smaller the upper limit of the unit tension F value of the strip in the annealing furnace. This is because: a higher Si content [Si] in the steel, especially exceeding 3.5%, significantly increases the risk of brittle strip breakage; while a higher normalizing annealing temperature T and a thinner hot-rolled plate thickness d make the steel more prone to deformation at high temperatures.

[0058] However, it should be noted that in this technical solution designed in this invention, the unit tension F value of the strip in the annealing furnace cannot be too low, otherwise the strip will deviate or be scratched. Therefore, in this invention, the unit tension F value of the strip in the annealing furnace is specifically controlled at 1.5 N / mm. 2 above.

[0059] Compared with the prior art, the non-oriented electrical steel for electric vehicle drive motors and its manufacturing method described in this invention have the following advantages and beneficial effects:

[0060] In the non-oriented electrical steel for electric vehicle drive motors described in this invention, the inventors optimized the chemical element composition ratio and related manufacturing processes. The non-oriented electrical steel for electric vehicle drive motors produced by this manufacturing method has high strength, high frequency, low iron loss and high magnetic induction intensity, while also having small magnetic anisotropy.

[0061] In this invention, the designed non-oriented electrical steel for electric vehicle drive motors has a yield strength ≥440MPa and an iron loss P 10 / 600 ≤30W / kg, and magnetic induction intensity B 50M ≥1.60T. The use of this non-oriented electrical steel for electric vehicle drive motors can effectively manufacture drive motors for new energy vehicles and effectively meet the market requirements for high speed, miniaturization, and high torque of electric vehicle drive motors. It has good prospects for promotion and application value. Detailed Implementation

[0062] The non-oriented electrical steel for electric vehicle drive motors and its manufacturing method described in this invention will be further explained and illustrated below with reference to specific embodiments. However, this explanation and illustration do not constitute an undue limitation on the technical solution of this invention.

[0063] Examples 1-10 and Comparative Examples 1-6

[0064] Table 1 lists the mass percentage of each chemical element in the non-oriented electrical steel for electric vehicle drive motors of Examples 1-10 and the comparative steel plates of Comparative Examples 1-6.

[0065] Table 1. (wt%, balance Fe and unavoidable impurities other than P, S, O, N)

[0066]

[0067]

[0068] The non-oriented electrical steel for electric vehicle drive motors in Examples 1-10 and the comparative steel plates in Comparative Examples 1-6 were all prepared using the following steps:

[0069] (1) Prepare the billet according to the chemical composition ratio shown in Table 1.

[0070] (2) Hot rolling: The obtained billet is hot rolled to obtain a hot-rolled plate coil with a thickness of 1.5 to 2.2 mm.

[0071] (3) Normalizing Annealing: The obtained hot-rolled coil is fed into a horizontal continuous annealing furnace for normalizing annealing treatment. The normalizing annealing temperature is controlled at 820℃-950℃, and the holding time for normalizing annealing is 90s. The unit tension F of the strip in the annealing furnace is controlled to satisfy the following relationship: 1.5≤F≤(3.8+0.3d) / ([Si)). 2 ×T), where d is the thickness of the hot-rolled coil (in mm), T is the normalizing annealing temperature (in °C), [Si] is the mass percentage of silicon in the hot-rolled coil (in %), and F is in N / mm². 2 .

[0072] (4) Cold rolling: The target thickness is achieved by one cold rolling process, or by one cold rolling process + intermediate annealing + two cold rolling processes.

[0073] (5) Continuous annealing is carried out in a continuous annealing furnace.

[0074] (6) Insulating coating.

[0075] It should be noted that, in this invention, the chemical composition and related process parameters of the non-oriented electrical steel for electric vehicle drive motors in Examples 1-10 all meet the design specifications and control requirements of this invention; however, in Comparative Examples 1-6, although the comparative steels in Comparative Examples 1-6 were also prepared using the above process steps, their chemical element composition and / or related process parameters contained parameters that did not conform to the design of this invention.

[0076] Table 2 lists the specific process parameters and final product thickness of the non-oriented electrical steel for electric vehicle drive motors in Examples 1-10 and the comparative steel plates in Comparative Examples 1-6 in the above manufacturing process.

[0077] Table 2.

[0078]

[0079]

[0080] Samples were taken from the final products, namely the non-oriented electrical steel for electric vehicle drive motors of Examples 1-10 and the comparative steel plates of Comparative Examples 1-6. Mechanical properties, magnetic induction, and iron loss were tested on the steel plate samples of Examples 1-10 and Comparative Examples 1-6 to measure the iron loss P. 10 / 600 Magnetic induction intensity B 50M The test results for yield strength and yield strength are listed in Table 3 below.

[0081] The relevant performance testing methods are as follows:

[0082] Tensile test: Based on the national standard GB / T 228.1-2010 Metallic materials, tensile testing - Part 1: Test method at room temperature, the mechanical properties of the steel plates in each embodiment and comparative example were tested to obtain the yield strength of the steel plates in each embodiment and comparative example.

[0083] Magnetic performance testing: Based on the national standard GB / T3655-2008 "Method for measuring the magnetic properties of electrical steel sheets (strips) using the Epstein square method", the magnetic performance was tested using the square method to obtain the magnetic induction intensity B in the rolling direction of the steel plates of each embodiment and comparative example when magnetized in a magnetic field of 5000 A / m. 50L The magnetic induction intensity B perpendicular to the rolling direction when magnetized in a magnetic field of 5000 A / m. 50C And the minimum magnetic induction intensity B at different angles from the rolling direction when magnetized in a magnetic field of 5000 A / m. 50X .

[0084] Meanwhile, based on the B obtained above 50L B 50C and B 50X From formula B 50M = (B 50L +B 50C +2B 50X The magnetic induction intensity B of the steel plate samples in Examples 1-10 and Comparative Examples 1-6 was calculated by 4 / 4. 50M .

[0085] Iron loss performance testing: Based on the standard "GB / T10129-2019 Method for Measuring Medium Frequency Magnetic Properties of Electrical Steel Strips (Sheets)", the iron loss performance was tested using the square circle method. The iron loss P of the steel plate samples from Examples 1-10 and Comparative Examples 1-6 at a magnetic flux density of 1.0T and a frequency of 600Hz was measured. 10 / 600 .

[0086] Table 3 lists the test results of the non-oriented electrical steel for electric vehicle drive motors in Examples 1-10 and the comparative steel plates in Examples 1-6.

[0087] Table 3.

[0088]

[0089] As can be seen from Tables 1, 2 and 3 above, in this invention, the non-oriented electrical steel for electric vehicle drive motors in Examples 1-4 adopts a single cold rolling process, and its chemical composition control, hot-rolled plate thickness, normalizing annealing temperature and furnace tension control are all within the design scope of this invention. Ultimately, it can obtain non-oriented silicon steel with low high-frequency iron loss, excellent magnetic anisotropy and high yield strength.

[0090] The chemical composition design and process of the non-oriented electrical steel for electric vehicle drive motors in Examples 5-10 also meet the requirements of the present invention. Unlike Examples 1-4, in Examples 5-10, the performance of the final steel plate can be further improved through further micro-alloying and secondary cold rolling processes.

[0091] As shown in Table 3 above, in this invention, the yield strength of the non-oriented electrical steel used in the electric vehicle drive motors of Examples 1-10 is between 448-565 MPa, and its magnetic induction intensity B 50M Between 1.632 and 1.662 T, the iron loss P 10 / 600 Between 17.5 and 28.5 W / kg, its overall performance is significantly better than that of the comparative steel plates in Comparative Examples 1-6. Comparative Examples 1-6 did not meet the conditions specified in this technical solution, therefore their implementation results were inferior to those of this invention.

[0092] Based on the data listed in Tables 1, 2 and 3 above, the five comparative examples prepared in this invention can be further analyzed and explained.

[0093] In Comparative Examples 1-3, although the chemical composition of the steel used was within the range designed in this invention, the normalizing annealing temperature used in the preparation process was too low (Comparative Example 1), or the furnace tension F was too high (Comparative Examples 2 and 3), resulting in a decrease in the magnetic induction intensity B of the final product. 50M Poor.

[0094] In Comparative Examples 4-6, although the production process used meets the requirements of the present invention, there are parameters in the chemical composition that do not meet the requirements of the present invention. The Si or Al content in the steel is too low, which will result in the high frequency iron loss of the final steel plate and the yield strength is lower than 440 MPa.

[0095] It should be noted that the scope of protection of the prior art in this invention is not limited to the embodiments given in this application. All prior art that does not contradict the solution of this invention, including but not limited to prior patent documents, prior publications, prior public uses, etc., can be included in the scope of protection of this invention.

[0096] Furthermore, the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0097] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A non-oriented electrical steel for an electric vehicle drive motor, characterized in that, Its mass percentage content of each chemical element is as follows: C ≤ 0.003%, Si: 3.0-4.5%, Al: 0.15-2.5%, Mn: 0.15-2.5%; balance is Fe and unavoidable impurities; The magnetic induction intensity B of the non-oriented electrical steel used in the electric vehicle drive motor 50M ≥1.60T, of which B 50M =(B 50L +B 50C +2B 50X ) / 4, where B 50L B represents the magnetic flux density in the rolling direction when magnetized in a magnetic field of 5000 A / m. 50C B represents the magnetic flux density perpendicular to the rolling direction when magnetized in a magnetic field of 5000 A / m. 50X The minimum magnetic induction intensity at a different angle from the rolling direction when magnetized in a magnetic field of 5000 A / m; iron loss P 10 / 600 ≤30W / kg; The non-oriented electrical steel for the electric vehicle drive motor is prepared by the following steps: A casting billet is obtained; Hot rolling: The thickness of the hot-rolled plate is controlled to be 1.5–2.2 mm; Normalizing annealing: The normalizing annealing temperature is controlled at 820℃-950℃, and a horizontal continuous annealing furnace is used for normalizing annealing. The unit tension F of the strip in the horizontal continuous annealing furnace is controlled to satisfy the following relationship: Where d is the thickness of the hot-rolled plate, with the unit parameter being mm; T is the normalizing annealing temperature, with the unit parameter being ℃; and F is the unit parameter being N / mm. 2 ; Cold rolling; Continuous annealing is performed in a continuous annealing furnace; Insulating coating.

2. The non-oriented electrical steel for electric vehicle drive motors as described in claim 1, characterized in that, Where C ≤ 0.002%.

3. The non-oriented electrical steel for electric vehicle drive motors as described in claim 1, characterized in that, Among the unavoidable impurities, P≤0.03%, S≤0.003%, N≤0.005%, and O≤0.0030%.

4. The non-oriented electrical steel for electric vehicle drive motors as described in claim 3, characterized in that, Among the unavoidable impurities, P ≤ 0.02% and N ≤ 0.0035%.

5. The non-oriented electrical steel for electric vehicle drive motors as described in claim 1, characterized in that, It also contains B: 0.0005%-0.010%.

6. The non-oriented electrical steel for electric vehicle drive motors as described in claim 1, characterized in that, It also contains at least one of Co, Ni, Sn, Sb, Cu, and Cr, and the total mass percentage of these elements is controlled between 0.020 and 4.0%.

7. The non-oriented electrical steel for electric vehicle drive motors as described in claim 1, characterized in that, Its thickness is 0.1 to 0.3 mm.

8. The non-oriented electrical steel for electric vehicle drive motors as described in claim 1, characterized in that, Its yield strength is ≥440MPa.

9. A method for manufacturing non-oriented electrical steel for an electric vehicle drive motor as described in any one of claims 1-8, characterized in that, Including the following steps: (1) Obtain the casting billet; (2) Hot rolling: The thickness of the hot-rolled plate is controlled to be 1.5 to 2.2 mm; (3) Normalizing annealing: The normalizing annealing temperature is controlled at 820℃-950℃, and a horizontal continuous annealing furnace is used for normalizing annealing. The unit tension F of the strip in the horizontal continuous annealing furnace is controlled to satisfy the following relationship: Where d is the thickness of the hot-rolled plate, with the unit parameter being mm; T is the normalizing annealing temperature, with the unit parameter being ℃; and F is the unit parameter being N / mm. 2 ; (4) Cold rolling; (5) Continuous annealing is performed in a continuous annealing furnace; (6) Insulating coating.

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