Non-oriented silicon steel sheet for new energy drive motor and method for producing same

Abstract

The present invention discloses a non-oriented silicon steel for new energy drive motors and a method for producing the same. The silicon steel is produced by sequentially carrying out steelmaking, continuous casting, hot rolling, normalizing, pickling, single stand cold rolling without preheating, annealing, cooling, coating and finishing. No Cu, Cr, Ni, Nb, V or Ti is added in the steelmaking process, and the chemical composition of the silicon steel is Si: 2.95%-3.15%, Al: 0.75%-0.95%, Si+2Al: 4.6%-4.9%, Mn: 0.5%-0.7%, Sn: 0.03%-0.04%, C≦0.0025%, the balance being iron, Mn / S≧380, Al / N≧200. The present invention improves strength while ensuring magnetic performance, solving the problem of compatibility between magnetic performance and strength that exists in the prior art, and can meet the requirements for application to drive motors of new energy vehicles.

Description

[Technical Field]

[0001] The present invention belongs to the technical field of steel material preparation, and relates to a non-oriented silicon steel for new energy drive motors. plate and its production method. [Background technology]

[0002] Non-oriented silicon steel is used as the core material for the rotors of electric motors and generators operating in rotating magnetic fields. Its magnetic properties, including low core loss and high magnetic flux density, are essential for its success. Therefore, improving its magnetic properties is a key research topic for those skilled in the art. From the chemical composition perspective, the addition of a series of alloying elements, such as Cu, Cr, Ni, Nb, V, and Ti, is usually strictly limited to avoid deterioration of the magnetic properties of non-oriented silicon steel due to the high content of these alloying elements.

[0003] In recent years, with the rapid development of new energy vehicles, higher performance is required for the non-oriented silicon steel used in the drive motor. Specifically, the drive motor of a new energy vehicle has a higher rotation speed than other conventional motors, and with the development of technology, the rotation speed of the drive motor of a new energy vehicle continues to increase, so the non-oriented silicon steel used is required to have high strength in addition to good magnetic properties.

[0004] However, in the prior art, in order to improve the strength of steel, from the viewpoint of chemical composition, it is usually necessary to increase the amount of a series of alloying elements such as Cu, Cr, Ni, Nb, V, Ti, etc. As mentioned above, the increase in the amount of these alloying elements leads to a deterioration in the magnetic properties of non-oriented silicon steel.

[0005] It can be seen from this that the design direction of the chemical composition is inconsistent with respect to the influence of the magnetic performance and strength of non-oriented silicon steel, so how to ensure the magnetic performance and strength of non-oriented silicon steel at the same time is a key issue facing non-oriented silicon steel used in the drive motors of new energy vehicles. Summary of the Invention

[0006] The object of the present invention is to provide a non-oriented silicon steel for new energy drive motors that improves strength while ensuring magnetic performance, thereby solving the problem of achieving both magnetic performance and strength that exists in the prior art. plate and to provide a method for producing the same.

[0007] In order to achieve the above object of the invention, an embodiment of the present invention provides a non-oriented silicon steel for new energy drive motors, and its chemical composition, in mass%, is as follows: Si: 2.95% to 3.15%, Al: 0.75% to 0.95%, Si+2Al: 4.6% to 4.9%, Mn: 0.5% to 0.7%, Sn: 0.03% to 0.04%, Cu≦0.03%, Cr≦0.03%, Ni ≦0.03%, Cr+Ni+Cu≦0.07%, Nb≦0.004%, V≦0.004%, Ti≦0.004%, Nb+V+Ti≦0.008%, C≦0.0025%, P≦0.015%, S≦0.0015%, N≦0.004%, C+S+N≦0.007%, and the balance is Fe and unavoidable impurities, and Mn / S≧380, Al / N≧200.

[0008] Furthermore, the recrystallized grain size of the non-oriented silicon steel is 50 μm to 80 μm.

[0009] Furthermore, the non-oriented silicon steel is a steel plate having a thickness of 0.25 mm to 0.35 mm, and has a yield strength of 460 MPa or more, a tensile strength of 550 MPa or more, and an iron loss P 1.0 / 400 ≦18.5W / kg, magnetic flux density B 5000 ≧1.67T.

[0010] Furthermore, the non-oriented silicon steel is a steel plate having a thickness of 0.25 mm, and the iron loss P 1.0 / 400 ≦17.5W / kg, or 0.30mm thick steel plate, iron loss P 1.0 / 400 ≦18.0W / kg, or 0.35mm thick steel plate, iron loss P 1.0 / 400 ≦18.5W / kg.

[0011] In order to achieve the above object of the invention, an embodiment of the present invention provides a method for producing non-oriented silicon steel for new energy drive motors, and the chemical composition of the non-oriented silicon steel is, in mass %, Si: 2.95% to 3.15%, Al: 0.75% to 0.95%, Si+2Al: 4.6% to 4.9%, Mn: 0.5% to 0.7%, Sn: 0.03% to 0.04%, Cu≦0.03%, Cr≦0.0 3%, Ni≦0.03%, Cr+Ni+Cu≦0.07%, Nb≦0.004%, V≦0.004%, Ti≦0.004%, Nb+V+Ti≦0.008%, C≦0.0025%, P≦0.015%, S≦0.0015%, N≦0.004%, C+S+N≦0.007%, the balance being Fe and unavoidable impurities, and Mn / S≧380, Al / N≧200; The recrystallized grain size of the non-oriented silicon steel is 50 μm to 80 μm, The production method includes sequentially carrying out steelmaking, continuous casting, hot rolling, normalizing, pickling, single-stand cold rolling, annealing, cooling, coating, and finishing to produce non-oriented silicon steel; In the hot rolling process, the continuously cast billet obtained in the continuous casting process is heated to 1080°C to 1110°C and held for 160 to 180 minutes, and then subjected to rough rolling, finish rolling, and coiling in sequence to obtain a hot rolled coil plate. The rolling start temperature during finish rolling is 950±20°C, the rolling end temperature is 840±20°C, the total reduction is 94 to 95%, and the coiling temperature during coiling is 620±20°C. In the normalizing process, the normalizing temperature is set to 840°C to 860°C and held for 180s to 200s. In the annealing step, the annealing temperature is set to 960°C to 980°C and is held for 40 to 45 seconds.

[0012] Preferably, in the single stand cold rolling step, multi-pass rolling is performed, the total reduction is 85±3%, and the reduction of each pass other than the final pass is 30% or more.

[0013] Preferably, the obtained non-oriented silicon steel is a steel plate having a thickness of 0.25 mm to 0.35 mm, and in the hot rolling step, a continuously cast billet having a thickness of 220 mm is roughly rolled into an intermediate billet having a thickness of 35 mm to 40 mm, and then finish-rolled into a hot-rolled plate having a thickness of 2.00 mm to 2.30 mm.

[0014] Preferably, the obtained non-oriented silicon steel is a steel plate having a thickness of 0.25 mm, the thickness of the intermediate billet is 35 mm, and the thickness of the hot-rolled plate is 2.00 mm; alternatively, the obtained non-oriented silicon steel is a steel plate having a thickness of 0.30 mm, the thickness of the intermediate billet is 37.5 mm, and the thickness of the hot-rolled plate is 2.15 mm; alternatively, the obtained non-oriented silicon steel is a steel plate having a thickness of 0.35 mm, the thickness of the intermediate billet is 40 mm, and the thickness of the hot-rolled plate is 2.30 mm.

[0015] Preferably, in the single stand cold rolling step, rolling is started directly without preheating the steel sheet after the pickling step. [Effects of the Invention]

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) From the viewpoint of chemical composition, alloying elements such as Cu, Cr, Ni, Nb, V, and Ti are not added, and in combination with the design of element contents such as Si, Al, Mn, and Sn, the magnetic performance of non-oriented silicon steel is improved, ensuring that the non-oriented silicon steel has low core loss and high magnetic flux density. At the same time, the grain size is controlled to 50 μm to 80 μm based on the chemical composition, thereby realizing refined crystal strengthening of the steel sheet and ensuring that the non-oriented silicon steel has high strength. While ensuring low cost and low production difficulty, the magnetic performance and strength of non-oriented silicon steel are comprehensively optimized, and non-oriented silicon steel can meet the application requirements for the drive motor of new energy vehicles. (2) Furthermore, by controlling the series of processes of hot rolling, normalizing, single-stand cold rolling, and annealing based on the design of the chemical composition, on the one hand, the recrystallized grain size of the non-oriented silicon steel can be refined, ensuring non-oriented silicon steel with excellent magnetic properties and high strength. On the other hand, the problem of cracking and fracture during cold rolling can be avoided, and the pre-roll preheating or secondary cold rolling commonly used in existing production processes can be omitted. Final rolling can be achieved using only the single-stand cold rolling process without preheating, thereby ensuring low production difficulty, low cost, and stable and continuous production. On the other hand, by controlling the low temperatures such as the heating temperature, rolling start temperature, and normalizing temperature, production energy consumption can be significantly reduced. Furthermore, not only can the normalizing temperature and holding time be lowered, but the thickness of the oxide scale on the steel sheet surface before the pickling process can be reduced, improving the pickling efficiency and the yield of the final non-oriented silicon steel. DETAILED DESCRIPTION OF THE INVENTION

[0017] The technical solutions of the present invention are further described below in connection with specific embodiments.

[0018] In an embodiment of the present invention, there is provided a non-oriented silicon steel having a chemical composition, in mass %, of Si: 2.95% to 3.15%, Al: 0.75% to 0.95%, Si+2Al: 4.6% to 4.9%, Mn: 0.5% to 0.7%, Sn: 0.03% to 0.04%, Cu≦0.03%, Cr≦0.03%, Ni≦0.03%, Cr+Ni+Cu≦0.07%, and N. b≦0.004%, V≦0.004%, Ti≦0.004%, Nb+V+Ti≦0.008%, C≦0.0025%, P≦0.015%, S≦0.0015%, N≦0.004%, C+S+N≦0.007%, and the balance being Fe and unavoidable impurities, with Mn / S≧380 and Al / N≧200.

[0019] Here, the function and effect of each element in the chemical composition will be explained as follows. C, S, N, Cu, Cr, Ni, Nb, V, Ti, and P: Increasing the content of these elements leads to deterioration of the magnetic properties of non-oriented silicon steel, including increased iron loss and decreased magnetic flux density. In the present invention, the upper limits of the content of these elements are appropriately lowered to C≦0.0025%, S≦0.0015%, N≦0.004%, C+S+N≦0.007%, Cu≦0.03%, Cr≦0.03%, Ni≦0.03%, Cr+Ni+Cu≦0.07%, Nb≦0.004%, V≦0.004%, Ti≦0.004%, Nb+V+Ti≦0.008%, and P≦0.015% without increasing the difficulty or cost of steelmaking.

[0020] Si, Al: Si is a solid-solution strengthening element, and increasing its content can increase the strength of the steel sheet, increase its resistivity, and reduce its iron loss. In the present invention, the Si content (by mass%) is controlled to 2.95% to 3.15%. Increasing the Al content increases the resistivity of the steel sheet and reduces its iron loss, but also reduces its magnetic flux density. In the present invention, the Al content (by mass%) is controlled to 0.75% to 0.95%. Furthermore, Al tends to form coarse AlN precipitates with N, which reduces the iron loss of the steel sheet. In the present invention, the Al content (by mass%) and the N content (by mass%) further satisfy the relationship Al / N≧200, thereby converting the adverse effect of N on the magnetic properties of the steel sheet into an advantageous effect and easing the difficulty of controlling N during steelmaking. Furthermore, an increase in the Si and Al contents makes cold rolling difficult, which increases the difficulty of production and thus increases production costs. To avoid this, the Si content (in mass%) and Al content (in mass%) in the present invention further satisfy the following: Si + 2Al: 4.6% to 4.9%.

[0021] Mn: Adding an appropriate amount of Mn is beneficial to improving the magnetic properties of steel sheet. Mn can suppress thermal shortness caused by S and easily form coarse MnS precipitates with S, thereby reducing the iron loss of the steel sheet. In the present invention, the Mn content (in mass%) and S content (in mass%) must satisfy the relationship Mn / S≧380, thereby converting the adverse effect of S element on the magnetic properties of the steel sheet into a beneficial effect and reducing the difficulty and cost of controlling S element in steelmaking.

[0022] Sn: A grain boundary segregation element that can improve magnetic performance. The Sn content (in mass %) in the present invention is 0.03% to 0.04%.

[0023] As described above, in this embodiment, the chemical composition reduces alloy costs, eases production difficulty, and reduces production costs, while not adding alloy elements such as Cu, Cr, Ni, Nb, V, and Ti, and by combining this with the design of the contents of elements such as Si, Al, Mn, and Sn, the magnetic performance of the non-oriented silicon steel is improved, ensuring that the non-oriented silicon steel has low iron loss and high magnetic flux density.

[0024] In this embodiment, the recrystallized grain size of the non-oriented silicon steel is 50 μm to 80 μm, and thus the chemical composition ensures low core loss and high magnetic flux density of the non-oriented silicon steel, while controlling the grain size to 50 μm to 80 μm realizes refined crystal strengthening of the steel sheet and ensures high strength of the non-oriented silicon steel, thereby achieving comprehensive optimization of the magnetic performance and strength of the non-oriented silicon steel while aiming for low cost and low production difficulty, and making the non-oriented silicon steel meet the requirements for application to the drive motors of new energy vehicles.

[0025] Specifically, the non-oriented silicon steel is a steel plate having a thickness of 0.25 mm to 0.35 mm, a yield strength of 460 MPa, a tensile strength of 550 MPa, and an iron loss P 1.0 / 400 ≦18.5W / kg, magnetic flux density B 5000 ≧1.67T.

[0026] Here, the non-oriented silicon steel is specifically a steel plate having a thickness of 0.35 mm, and its iron loss P 1.0 / 400 ≦18.5W / kg, or 0.30mm thick steel plate, iron loss P 1.0 / 400 ≦18.0W / kg, or 0.25mm thick steel plate, iron loss P 1.0 / 400 ≦17.5W / kg.

[0027] Furthermore, this embodiment also provides a preferred production method for the non-oriented silicon steel. The production method sequentially includes steelmaking, continuous casting, hot rolling, normalizing, pickling, single-stand cold rolling, annealing, cooling, coating, and finishing to produce the non-oriented silicon steel. That is, the non-oriented silicon steel can be prepared by this preferred production method. The production method of this embodiment not only enables smooth production of the non-oriented silicon steel with excellent magnetic properties and high strength, but also has the advantages of low production difficulty and low production costs, ensuring stable production of the non-oriented silicon steel.

[0028] Specifically, in the steelmaking process, molten iron is refined into molten steel, and in the continuous casting process, the molten steel obtained in the steelmaking process is continuously cast into a billet using a continuous casting machine. As will be understood, the chemical composition of the molten steel obtained in the steelmaking process and the chemical composition of the continuously cast billet obtained in the continuous casting process both coincide with the chemical composition of the non-oriented silicon steel finally obtained from the production method. That is, in mass%, it contains Si: 2.95% to 3.15%, Al: 0.75% to 0.95%, Si + 2Al: 4.6% to 4.9%, Mn: 0.5% to 0.7%, Sn: 0.03% to 0.04%, Cu≦0.03%, Cr≦0.03%, Ni≦0.03%, Cr + Ni + Cu≦0.07%, Nb≦0.004%, V≦0.004%, Ti≦0.004%, Nb + V + Ti≦0.008%, C≦0.0025%, P≦0.015%, S≦0.0015%, N≦0.004%, C + S + N≦0.007%, and the remainder is Fe and unavoidable impurities, with Mn / S≧380 and Al / N≧200.

[0029] In this embodiment, in the hot rolling process, the continuously cast billet obtained in the continuous casting process is heated to 1080°C to 1110°C and held for 160 to 180 minutes, and then rough rolling, finish rolling, and coiling are sequentially performed to obtain a hot rolled coil plate. In the finish rolling, the rolling start temperature is 950±20°C, the rolling end temperature is 840±20°C, the total reduction is 94 to 95%, and the coiling temperature is 620±20°C. In the normalizing process, the normalizing temperature is 840°C to 860°C and held for 180 to 200 seconds. In the annealing process, the annealing temperature is 960°C to 980°C and held for 40 to 45 seconds.

[0030] As described above, in the production method of this embodiment, by controlling the heating temperature in the hot rolling process low, the solid solution of coarse precipitates such as MnS and AlN in the continuous cast billet is avoided, and precipitate control in the subsequent rough rolling and finish rolling processes is more reliable, thereby solidifying the basis for the magnetic performance of the finally obtained grain-oriented silicon steel. By controlling the rolling start temperature, rolling finish temperature, total reduction rate, and coiling temperature in the finish rolling process, combined with the design of Si+2Al: 4.6% to 4.9% in the chemical composition, the structure of the hot-rolled coil plate is stable and the storage capacity is consistent. The recrystallization temperature of the hot-rolled coil plate in the subsequent normalizing process is stably maintained, providing conditions for accurate control of the degree of recrystallization in the subsequent normalizing process. The design of the normalizing temperature and holding time in the normalizing process based on the hot rolling process prevents partial recrystallization from occurring in the normalizing process (i.e., complete recrystallization is not completed). The method achieves precise control of the area ratio of the unrecrystallized structure and the recrystallized grain size in the resulting steel sheet (specifically, the area ratio of the unrecrystallized structure is approximately 5% to 20%), and the recrystallized grain size is ≦50 μm. This provides the conditions for controlling the recrystallized grain size in the annealing process, while forming numerous grain boundaries between the unrecrystallized structure and the recrystallized grains, preventing cracks from expanding in the subsequent cold rolling. This reduces the difficulty of the cold rolling process and ensures stable production in the cold rolling process. It also eliminates the pre-roll preheating or secondary cold rolling commonly used in prior art, and allows final rolling to be completed with a low-cost single-stand cold rolling process without preheating. By designing the annealing temperature and holding time based on the normalizing process, complete recrystallization occurs in the annealing process, preventing the recrystallized grains from growing too large, resulting in a small recrystallized grain size in the final non-oriented silicon steel.

[0031] As described above, in the production method of this embodiment, the series of processes, including the hot rolling process, normalizing process, single-stand cold rolling process, and annealing process, are controlled based on the chemical composition design, thereby minimizing the recrystallized grain size of the non-oriented silicon steel and ensuring non-oriented silicon steel with excellent magnetic properties and high strength. Meanwhile, cracking and fracture problems during cold rolling are avoided. The pre-roll preheating or secondary cold rolling commonly used in existing production processes can be omitted, and final rolling can be completed using only the single-stand cold rolling process without preheating, ensuring low production difficulty, low cost, and stable continuous production. Meanwhile, low-temperature control of the heating temperature, rolling start temperature, normalizing temperature, etc. significantly reduces production energy consumption. Furthermore, the low normalizing temperature and short holding time reduce the thickness of oxide scale on the steel sheet surface before the pickling process, which is beneficial to improving the pickling efficiency and improving the surface quality and yield of the final non-oriented silicon steel.

[0032] More preferably, based on the chemical composition required for the final molten steel, no alloying materials such as Cu, Cr, Ni, Nb, V, and Ti are added in the steelmaking process, thereby reducing the cost of alloying materials.

[0033] More preferably, in the single stand cold rolling process, the steel sheet after the pickling process is directly rolled without preheating. In the prior art, the steel sheet usually needs to be preheated before cold rolling, but in this embodiment, the steel sheet is directly rolled without preheating after the normalizing process, which can save production costs.

[0034] In the single-stand cold rolling process, multi-pass rolling is performed with a total reduction of 85±3%. By controlling in this manner, the cold rolling storage capacities of non-oriented silicon steels of different thicknesses in the single-stand cold rolling process are basically the same, and further, the same annealing temperature and holding time are used in the subsequent annealing process, which has the effect of eliminating the need for frequent changeover operations when continuously producing non-oriented silicon steels of different thicknesses on the same production line.

[0035] In the single-stand cold rolling process, multi-pass rolling is performed, and the reduction ratio of each pass except the final pass is 30% or more. For example, when five-pass rolling is performed, the reduction ratios of the first to fourth passes are 30% or more, and the reduction ratio of the fifth pass is selectively less than 30%. This not only effectively avoids the generation of cold-rolled fragments in the single-stand cold rolling process, but also reduces the number of rolling passes, and further ensures a good plate shape of the final non-oriented silicon steel.

[0036] As described above, the non-oriented silicon steel is a steel plate having a thickness of 0.25 mm to 0.35 mm. In a preferred embodiment, the thickness of the continuously cast billet obtained in the continuous casting step is 220 mm, and in the hot rolling step, the 220 mm thick continuously cast billet is rough rolled to an intermediate billet having a thickness of 35 mm to 40 mm, and then finish rolled to a hot rolled plate having a thickness of 2.00 mm to 2.30 mm. As will be understood, in the single stand cold rolling step, the hot rolled plate having a thickness of 2.00 mm to 2.30 mm is further rolled to a finished non-oriented silicon steel product having a target thickness.

[0037] For example, if the non-oriented silicon steel finally obtained by the production method is a steel plate having a thickness of 0.25 mm, in the hot rolling step, a continuously cast billet having a thickness of 220 mm is rough rolled into an intermediate billet having a thickness of 35 mm, and then finish rolled into a hot rolled sheet having a thickness of 2.00 mm. Also, if the non-oriented silicon steel finally obtained by the production method is a steel plate having a thickness of 0.30 mm, in the hot rolling step, a continuously cast billet having a thickness of 220 mm is rough rolled into an intermediate billet having a thickness of 37.5 mm, and then finish rolled into a hot rolled sheet having a thickness of 2.15 mm. Also, if the non-oriented silicon steel finally obtained by the production method is a steel plate having a thickness of 0.35 mm, in the hot rolling step, a continuously cast billet having a thickness of 220 mm is rough rolled into an intermediate billet having a thickness of 40 mm, and then finish rolled into a hot rolled sheet having a thickness of 2.30 mm. Of course, these are merely preferred embodiments, and the present invention is not limited to these specific embodiments.

[0038] Preferably, in the normalizing step, normalizing is performed in a pure dry N2 atmosphere at a constant speed, i.e., the front, middle and rear ends of the steel sheet are normalized at a constant roll speed.

[0039] Furthermore, in the annealing process, annealing is performed in a mixed atmosphere of H2 and N2 at a constant speed, i.e., the leading, middle and trailing ends of the steel sheet are annealed at a constant roll speed.

[0040] Furthermore, in the production method, the pickling process, cooling process, coating process and finishing process can be carried out by feasible techniques disclosed in the prior art, so they will not be repeated here.

[0041] As described above, compared with the prior art, the embodiments of the present invention have the following beneficial effects: (1) In the chemical composition, alloying elements such as Cu, Cr, Ni, Nb, V, and Ti are not added, but rather, in combination with the design of the contents of elements such as Si, Al, Mn, and Sn, the magnetic performance of the non-oriented silicon steel is improved, ensuring that the non-oriented silicon steel has low core loss and high magnetic flux density. At the same time, by controlling the particle size to 50 μm to 80 μm based on the chemical composition, refined crystal strengthening of the steel sheet is achieved, ensuring that the non-oriented silicon steel has high strength. This achieves comprehensive optimization of the magnetic performance and strength of non-oriented silicon steel at low cost and low production difficulty, and ensures that the non-oriented silicon steel meets the requirements for use in the drive motors of new energy vehicles.

[0042] (2) Furthermore, by controlling the series of processes including hot rolling, normalizing, single-stand cold rolling, and annealing based on the chemical composition design, the recrystallized grain size of the non-oriented silicon steel is refined, ensuring that non-oriented silicon steel with excellent magnetic properties and high strength is obtained. At the same time, cracking and fracture problems during cold rolling are avoided, and the pre-roll preheating or secondary cold rolling commonly used in conventional production processes can be omitted. Final rolling can be completed using only the single-stand cold rolling process without preheating, ensuring low production difficulty, low cost, and stable continuity. At the same time, low control of the heating temperature, rolling start temperature, normalizing temperature, etc. significantly reduces production energy consumption. Furthermore, the low normalizing temperature and short holding time reduce the thickness of oxide scale on the steel sheet surface before the pickling process, which is beneficial to improving the pickling efficiency and improving the surface quality and yield of the final non-oriented silicon steel.

[0043] The above detailed description is only a specific description of the feasible embodiments of the present invention, and does not define the protection scope of the present invention, and all equivalent embodiments or modifications obtained without departing from the technical spirit of the present invention shall be included in the protection scope of the present invention.

[0044] Hereinafter, six embodiments of the present invention will be provided to further illustrate the technical solutions of the present invention, of course, these embodiments are only a part of the multiple variations included in the present invention, but not all of them.

[0045] Examples 1 to 6 each provide a non-oriented silicon steel. The chemical composition, expressed in mass %, is as shown in Table 1. The non-oriented silicon steel of each example is specifically a steel plate having the thickness shown in Table 1.

[0046] [Table 1] JPEG0007789908000001.jpg122170

[0047] The non-oriented silicon steels of Examples 1 to 6 were sampled and detected. (1) The recrystallized grain size measured in the metallographic structure test is shown in Table 2, (2) The yield strength and tensile strength measured in the mechanical performance test are shown in Table 2, and (3) The iron loss P measured in the magnetic performance test are shown in Table 2. 1.0 / 400 and magnetic flux density B 5000 are shown in Table 2.

[0048] [Table 2] JPEG0007789908000002.jpg55170

[0049] The non-oriented silicon steels of Examples 1 to 6 were produced in the following manner. (1) Molten iron was refined into molten steel with the chemical composition shown in Table 1. No alloying materials, Cu, Cr, Ni, Nb, V, or Ti, were added during the steelmaking process. The molten steel refined using a continuous casting billet was then formed into a 220 mm thick continuous casting billet. The chemical composition of the continuous casting billet is also shown in Table 1. (2) The continuously cast billet obtained in step 1 was heated in a heating furnace. The heating temperature and holding time are shown in Table 3. A hot-rolled coil plate was then obtained by rough rolling, finish rolling, and coiling. Table 3 shows the thickness of the intermediate billet obtained by rough rolling, the rolling start temperature, rolling finish temperature, total reduction, thickness of the obtained hot-rolled plate, and coiling temperature during finish rolling.

[0050] [Table 3] JPEG0007789908000003.jpg65170

[0051] (3) The hot-rolled coil plate obtained in step 2 was normalized in a pure dry N2 atmosphere. The normalizing process was carried out at a constant rate. The normalizing temperature and holding time are shown in Table 4. After normalizing was completed, the metallographic structure of the steel plate of each example was examined. The measured area ratio of the unrecrystallized structure and the recrystallized grain size are shown in Table 4. Here, the area ratio of the unrecrystallized structure is the ratio of the area of ​​the unrecrystallized structure to the total area of ​​the sampled cross section of the steel plate.

[0052] [Table 4] JPEG0007789908000004.jpg55170

[0053] (4) The steel sheet obtained in step 3 was pickled, and after pickling, it was directly subjected to single-stand cold rolling without preheating. Here, five passes of rolling were performed during the single-stand cold rolling period. The total reduction was 85±3%, and the reduction of each pass except the final pass was 30% or more. The thickness of the obtained steel sheet is shown in Table 1. The reduction gauge of each pass is shown in Table 5.

[0054] [Table 5] JPEG0007789908000005.jpg67170

[0055] (5) The steel sheets obtained in step 4 were annealed in a mixed atmosphere of H2 and N2. The annealing process was carried out at a constant speed. The annealing temperature and holding time are shown in Table 6. After annealing, the steel sheets were sequentially cooled, coated, and finished. This resulted in the finished non-oriented silicon steel products of each example.

[0056] [Table 6] JPEG0007789908000006.jpg55170

[0057] As can be seen from the above Examples 1 to 6, the non-oriented silicon steel according to the embodiment of the present invention not only has excellent magnetic properties, but also has high strength, low alloying material costs, low production difficulty, and low production costs, which meets the requirements for application to the drive motor of a new energy vehicle.

Claims

1. A non-oriented silicon steel sheet having a thickness of 0.25 mm to 0.35 mm and a recrystallized grain size of 50 μm to 80 μm is prepared by sequentially carrying out steelmaking, continuous casting, hot rolling, normalizing, pickling, single-stand cold rolling without preheating, annealing, cooling, coating, and finishing; The chemical composition of the continuously cast billet obtained in the continuous casting process is, in mass%, Si: 2.95% to 3.15%, Al: 0.75% to 0.95%, Si + 2Al: 4.6% to 4.9%, Mn: 0.5% to 0.7%, Sn: 0.03% to 0.04%, Cu≦0.03%, Cr≦0.03%, Ni≦0.03%, Cr + Ni + C u≦0.07%, Nb≦0.004%, V≦0.004%, Ti≦0.004%, Nb+V+Ti≦0.008%, C≦0.0025%, P≦0.015%, S≦0.0015%, N≦0.004%, C+S+N≦0.007%, Mn / S≧380, Al / N≧200, and the balance being Fe and unavoidable impurities, In the hot rolling step, the continuously cast billet obtained in the continuous casting step is successively heated, rough rolled, finish rolled, and coiled to obtain a hot rolled coil plate, the rolling start temperature during finish rolling is 950±20°C, the rolling end temperature is 840±20°C, the total rolling reduction is 94 to 95%, and the coiling temperature during coiling is 620±20°C, A method for producing a non-oriented silicon steel sheet for a new energy drive motor, characterized in that in the normalizing process, the area ratio of the unrecrystallized structure is 5% to 20%.

2. 2. The method for producing a non-oriented silicon steel sheet for a new energy drive motor according to claim 1, wherein in the hot rolling step, the continuously cast billet obtained in the continuous casting step is heated to 1080°C to 1110°C and held at that temperature for 160 min to 180 min.

3. 2. The method for producing non-oriented silicon steel sheets for new energy drive motors according to claim 1, wherein in the normalizing process, the normalizing temperature is set to 840°C to 860°C and maintained for 180s to 200s.

4. 2. The method for producing non-oriented silicon steel sheets for new energy drive motors according to claim 1, wherein in the annealing step, the annealing temperature is set to 960°C to 980°C and maintained for 40s to 45s.

5. 2. The method for producing a non-oriented silicon steel sheet for a new energy drive motor according to claim 1, wherein in the single stand cold rolling process, multi-pass rolling is performed, the total reduction is 85±3%, and the reductions of each pass other than the final pass are all 30% or more.

6. 2. The method for producing a non-oriented silicon steel sheet for new energy drive motors according to claim 1, wherein in the hot rolling step, a continuously cast billet having a thickness of 220 mm is roughly rolled into an intermediate billet having a thickness of 35 mm to 40 mm, and then the intermediate billet is finish rolled into a hot rolled sheet having a thickness of 2.00 mm to 2.30 mm.

7. 7. The method for producing a non-oriented silicon steel sheet for a new energy traction motor according to claim 6, wherein the non-oriented silicon steel sheet is a steel sheet having a thickness of 0.25 mm, the thickness of the intermediate billet is 35 mm, and the thickness of the hot-rolled sheet is 2.00 mm; or the non-oriented silicon steel sheet is a steel sheet having a thickness of 0.30 mm, the thickness of the intermediate billet is 37.5 mm, and the thickness of the hot-rolled sheet is 2.15 mm; or the non-oriented silicon steel sheet is a steel sheet having a thickness of 0.35 mm, the thickness of the intermediate billet is 40 mm, and the thickness of the hot-rolled sheet is 2.30 mm.

8. 2. The method for producing non-oriented silicon steel sheets for new energy traction motors according to claim 1, wherein no alloying materials such as Cu, Cr, Ni, Nb, V, and Ti are added in the steelmaking process.

9. A non-oriented silicon steel sheet for a new energy drive motor, The chemical composition of the non-oriented silicon steel sheet is, in mass%, Si: 2.95% to 3.15%, Al: 0.75% to 0.95%, Si + 2Al: 4.6% to 4.9%, Mn: 0.5% to 0.7%, Sn: 0.03% to 0.04%, Cu≦0.03%, Cr≦0.03%, Ni≦0.03%, Cr + Ni + Cu≦0.07%, Nb≦0.004%, V≦0.004%, Ti≦0. 0.004%, Nb+V+Ti≦0.008%, C≦0.0025%, P≦0.015%, S≦0.0015%, N≦0.004%, C+S+N≦0.007%, and the balance being Fe and unavoidable impurities; Mn / S≧380, Al / N≧200; and a recrystallized grain size of 50 μm to 80 μm.

10. The non-oriented silicon steel sheet for new energy drive motors as described in claim 9, characterized in that it has a thickness of 0.25 mm to 0.35 mm.

11. The non-oriented silicon steel sheet has a yield strength of 460 MPa or more, a tensile strength of 550 MPa or more, and an iron loss P １．０／４００ ≦18.5W / kg, magnetic flux density B ５０００ 10. The non-oriented silicon steel sheet for new energy traction motors according to claim 9, wherein the non-oriented silicon steel sheet has a hardness of 1.67T or more.

12. The non-oriented silicon steel sheet is a steel sheet having a thickness of 0.25 mm, and the iron loss P １．０／４００ ≦17.5 W / kg, or a steel plate having a thickness of 0.30 mm, and iron loss P １．０／４００ ≦18.0 W / kg, or a steel plate having a thickness of 0.35 mm, and iron loss P １．０／４００ The non-oriented silicon steel sheet according to claim 11, characterized in that it has a strength of ≦18.5 W / kg.

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