Non-oriented silicon steel for high-speed motors and method for manufacturing the same

Abstract

The present application relates to the technical field of non-oriented silicon steel, and more particularly to a non-oriented silicon steel for high-speed motors and a manufacturing method thereof. The chemical components of the non-oriented silicon steel for high-speed motors are as defined in the specification. The thickness of the final product is 0.20-0.30 mm, and the grain size of the final product is 80-100 μm. The manufacturing method of the non-oriented silicon steel for high-speed motors includes the steps of smelting to cast a continuous casting billet, cooling the continuous casting billet, heating, hot rolling, normalizing, pickling, cold rolling, annealing, and coating. The present application provides a method for improving strength and reducing high-frequency iron loss P by utilizing means such as resistivity control, inclusion control, texture control, and grain size control through the control of chemical components and the design of the entire process of the above flow. 1.0 / 1000 Moreover, the smelting cost is low, the production process is simple, the production cost is low, and the requirements for high speed motors, such as high rotation speed, small size and high efficiency, are met.

Description

Cross-reference of related applications

[0001] This application claims priority to the Chinese patent application filed with the China National Intellectual Property Administration on September 13, 2022, with application number 202211107301.5, titled "Non-oriented silicon steel for high-speed motors and method for manufacturing the same," all of which are incorporated herein by reference. [Technical Field]

[0002] This application relates to the technical field of non-oriented silicon steel, and more specifically, to non-oriented silicon steel for high-speed motors and a method for manufacturing the same. [Background technology]

[0003] High-speed motors typically refer to motors with a rotational speed exceeding 10,000 r / min. High-speed motors offer significant advantages such as high rotational speed, compact size, high power density, and high efficiency. They are widely used in many applications, including centrifugal compressors in air conditioners and refrigerators, energy storage flywheels, and high-speed grinders, and have broad potential applications in electric vehicles and distributed power generation systems. Currently, they are one of the hottest research spots in the international field of electrical engineering.

[0004] The main characteristics of high-speed motors are high rotor speed, high stator winding current, and high magnetic flux frequency within the core. The centrifugal force acting on the motor rotor is proportional to the square of the linear velocity. Because high-speed motors have rotational speeds exceeding 10,000 r / min, the non-oriented silicon steel used in the rotor core requires high mechanical strength. Furthermore, to meet the technical requirements of high rotational speed, the size of high-speed motors is much smaller than that of normal-speed motors of the same output, thus requiring high magnetic induction in the non-oriented silicon steel used in the core of high-speed motors. Simply put, to achieve the control requirements of high rotational speed, small size, and high efficiency of high-speed motors, the non-oriented silicon steel, the main material of the core, must have low strength and high-frequency iron loss P 1.0 / 1000 A small size and high magnetic induction are required.

[0005] Most existing technologies for producing non-oriented silicon steel focus only on iron loss under frequency conditions of 50Hz to 400Hz. There are few production technologies that focus on iron loss under frequency conditions of 1000Hz or higher, but these production processes are complex and difficult to meet the needs of the rapid development of future high-speed motors.

[0006] For example, the patent document in Chinese Patent Publication No. CN111471927A discloses a high magnetic induction non-oriented silicon steel for automotive generators and a method for manufacturing the same. The non-oriented silicon steel contains, as a chemical composition, Si 0.60~1.60 wt%, Mn 0.10~0.65 wt%, P 0.040~0.100 wt%, Als ≤ 0.0080 wt%, and Sn 0.01~0.10 wt%, with C+S+O+N+Ti ≤ 100 ppm, and the content of each element is all 25 ppm or less, with the remaining components being Fe and unavoidable impurity elements. By optimizing the design of the components and process, the magnetic properties of the final product are such that iron loss P 1.5 / 50 ≤4.50 W / kg, Magnetic induction B 5000 It satisfies ≥1.74T, and its mechanical properties satisfy a Vickers microhardness HV1 in the range of 110-120 and an elongation A50 ≥ 40%.

[0007] The patent document, Chinese Patent Publication No. CN107964631B, discloses a non-oriented silicon steel for high-speed motor rotors with a yield strength of ≥500 MPa, the chemical composition of which is Si: 4.12~4.5 wt%, Al: 1.62~2.0 wt%, Mn: 0.5~2.0 wt%, N ≤ 0.005 wt%, S ≤ 0.002 wt%, C ≤ 0.003 wt%, P ≤ 0.05 wt%, Cu ≤ 0.05 wt%, Ti + Nb + V + Zr ≤ 0.01 wt%. The production method is converter smelting, RH vacuum refining, casting billet heating, rough rolling and finish rolling, winding, pickling, cold rolling, and annealing. The non-oriented silicon steel for high-speed motor rotors disclosed herein has a yield strength of 500 MPa or more, and the final product having a thickness of 0.35 mm or less has iron loss of P 1.0 / 400 It is ≤18 W / kg.

[0008] In the patent document with Chinese Patent Publication Number CN107974620B, non-oriented silicon steel for high-speed rotors with a yield strength of 600 MPa grade is disclosed. Its chemical composition is C 0.001 - 0.003 wt%, Si 2.6 - 3.4 wt%, Mn 0.20 - 0.60 wt%, P ≤ 0.005 wt%, S ≤ 0.005 wt%, Als 0.75 - 0.95 wt%, N 0.002 - 0.006 wt%, Nb 0.053 - 0.20 wt%. The production steps include smelting in a converter and casting into billets, heating the continuous casting billets, normal rough rolling and finish rolling steps, annealing steps, pickling and then cold rolling steps, and continuous annealing steps. In the non-oriented silicon steel disclosed in the present application, for the final product with a thickness of 0.35 mm or less, the yield strength ≥ 600 MPa, tensile strength ≥ 700 MPa, P 1.0 / 400 ≤ 35 W / kg, B 5000 ≥ 1.60 T.

[0009] The non-oriented silicon steel for general motors provided by the above patents CN111471927A, CN107964631B, and 107974620B can meet the requirements of high-speed motors in terms of mechanical strength and magnetic induction, but only focuses on the iron loss under the conditions of a frequency of 50 Hz - 400 Hz. The iron loss of non-oriented silicon steel includes three types: hysteresis loss, eddy current loss, and abnormal loss. Since the proportion of abnormal loss in the iron loss is small, generally, hysteresis loss and eddy current loss are noted. Hysteresis loss P h = k h * f * B 2 , eddy current loss P e = k e * f 2 * B 2 is. From the formulas of hysteresis loss and eddy current loss, hysteresis loss P h is proportional to f, and eddy current loss P e and f 2They are inversely proportional. Therefore, as the frequency increases, eddy current loss increases significantly within the iron loss. At low frequencies (50Hz to 400Hz), hysteresis loss accounts for the majority of the iron loss, while at high frequencies (≥1000Hz), eddy current loss accounts for the majority of the iron loss. Clearly, the composition of iron loss differs between high-frequency and low-frequency conditions, making it difficult to ensure that non-oriented silicon steel with good magnetic properties at low frequencies maintains good magnetic properties at high frequencies. In other words, in the non-oriented silicon steel and its manufacturing method described in the above patent, the high-frequency iron loss P of non-oriented silicon steel for high-speed motors is... 1.0 / 1000 It is difficult to meet the requirements for use and has the disadvantage of high iron loss at high frequencies.

[0010] The patent document with Chinese Patent Publication No. CN104480386B discloses a 0.2 mm thick non-oriented silicon steel for high-speed motors, the composition of which is C 0.001~0.025 wt%, Si 2.6~3.0 wt%, Al 0.25~0.55 wt%, Mn 0.10~0.30 wt%, P ≤ 0.015 wt%, S 0.001~0.0025 wt%, N 0.001~0.0025 wt%. The production steps include: smelting in a vacuum induction furnace to cast into a steel ingot; dividing and heating the ingot; forging and heating; hot rolling; normalizing; pickling; first cold rolling; intermediate annealing; second cold rolling; annealing the final product; and cooling, cutting, sample preparation, and measurement of magnetic and mechanical properties by conventional methods. This application relates to the magnetic properties P 1.0 / 1000 ≤40 w / kg, B 5000 Assuming a torque of ≥1.68T is ensured, the yield ratio of the mechanical properties is 0.70 to 0.73, and the requirements for manufacturing iron cores for high-speed motors are met.

[0011] The patent document with Chinese Patent Publication No. CN112538592B discloses non-oriented silicon steel for high-speed motors with a frequency of ≥ 10000 Hz, wherein the composition includes C ≤ 0.003 wt%, Si 2.8~3.5 wt%, Mn 0.05~1.0 wt%, P ≤ 0.0015 wt%, N ≤ 0.0008 wt%, Al 0.75~1.5 wt%, S ≤ 0.0009 wt%, Sb 0.001~0.1 wt%, Sn 0.001~0.1 wt%, and satisfies the condition that Sb + Sn is 0.001~0.1%. The steps include smelting and casting into a billet, heating the cast billet, maintaining the temperature, hot rolling and winding, normalizing, maintaining the temperature, pickling and winding, the first cold rolling step, the first continuous annealing step, the second cold rolling step, the second continuous annealing step, the third cold rolling step, the continuous annealing step of the final product, and the steps of slow cooling, insulating layer coating and curling. The present invention relates to a material with a thickness of 0.02 to 0.15 mm, excellent magnetic properties, i.e., P 0.1 / 10000 is 15.5 W / kg or less, P 0.1 / 400 is 9.5 W / kg or less, B 5000 It is 1.6T or more.

[0012] Patent documents with Chinese patent publication numbers CN104480386B and CN112538592B disclose non-oriented silicon steel for high-speed motors with current frequencies of 1000Hz and 10000Hz, respectively, but the production process is complex and costly. For example, patent document CN104480386B discloses 0.2mm thick non-oriented silicon steel for high-speed motors, and its production process involves two cold rolling cycles and two annealing cycles, while patent document CN112538592B discloses non-oriented silicon steel for high-speed motors with frequencies ≥ 10000Hz, and its production process includes three cold rolling cycles and three annealing cycles.

[0013] Most of the existing technologies for producing non-oriented silicon steel focus only on iron loss under conditions of frequencies from 50 Hz to 400 Hz. Although there are only a few production technologies that focus on iron loss under conditions of frequencies of 1000 Hz or higher, the production process is complex and it is difficult to meet the needs of the rapid development of future high-speed motors.

Summary of the Invention

Problems to be Solved by the Invention

[0014] The technical problem to be solved by the present application is to provide a non-oriented silicon steel for high-speed motors and a manufacturing method thereof in order to solve the defects of the conventional non-oriented silicon steel for high-speed motors, which has a complex production process or large iron loss at high frequencies.

Means for Solving the Problems

[0015] Therefore, the present application provides a non-oriented silicon steel for high-speed motors, the chemical composition of which is C≤0.0020% by mass, S≤0.0010% by mass, N≤0.0030% by mass, Si: 3.0 - 3.4% by mass, Al: 0.80 - 1.0% by mass, Mn: 0.2 - 0.4% by mass, P≤0.01% by mass, Sn + Sb≤0.004% by mass, Nb≤0.005% by mass, V≤0.005% by mass, Ti≤0.005% by mass, Mo≤0.005% by mass, Cr≤0.05% by mass, Ni≤0.05% by mass, Cu≤0.05% by mass, and the rest are Fe and inevitable impurities, 0 < C + S + N≤0.0050%, the thickness of the final product is 0.20 - 0.30 mm, and the grain size of the final product is 80 - 100 μm.

[0016] Furthermore, the non-oriented silicon steel for high-speed motors has a yield strength of ≥550 MPa, magnetic induction B 5000 ≥1.65, and at a thickness of 0.30 mm, the high-frequency iron loss P 1.0 / 1000 ≤45 W / kg, at a thickness of 0.25 mm, the high-frequency iron loss P 1.0 / 1000 ≤40 W / kg, and at a thickness of 0.20 mm, the high-frequency iron loss P 1.0 / 1000 ≤35 W / kg.

[0017] Furthermore, 4.8% ≦ Si + 2Al ≦ 5.2%.

[0018] The main functions of each element and process in this application are as follows.

[0019] C ≦ 0.0020%, S ≦ 0.0010%, N ≦ 0.0030%: C, S, and N are all harmful elements in non-oriented silicon steel. When the C content increases, the iron loss increases and the magnetic induction decreases. When C is high, there may also be problems with magnetic aging, and the lower its content, the better. S and Mn form fine MnS, and N and Al form fine AlN. This not only hinders the growth of crystal grains during annealing but also directly hinders the movement of magnetic walls and increases the hysteresis loss. Non-oriented silicon steel generally adopts vacuum refining, and it is not difficult to control C below 0.002% and N below 0.003%. Generally, the S content of medium and low-grade non-oriented silicon steel is controlled below 0.0030%, but if the S content continues to be reduced, the cost will increase. However, for the high-grade non-oriented silicon steel for high-speed motors in this application, since the Si content is controlled at 3.0 - 3.4% and the Al content is controlled at 0.80 - 1.0%, the O content in the molten steel is significantly reduced. According to the desulfurization reaction CaO + S = CaS + O, when the O content in the molten steel decreases, the difficulty of desulfurization is reduced. Therefore, in this application, C is controlled below 0.0020%, S below 0.0010%, and N below 0.0030%, and also 0 < C + S + N ≦ 0.0050%. By controlling the harmful elements C, S, and N, not only is the hysteresis loss during high-frequency operation of the non-oriented silicon steel in this application reduced, but the magnetic induction is improved and magnetic aging is also reduced.

[0020] Si 3.0~3.4%, Al 0.80~1.0%: Both Si and Al are effective additives for improving resistivity, reducing iron loss, and increasing strength. However, as the Si and Al content increases, the difficulty of rolling the steel increases, making edge cracking more likely during hot rolling and plate fracture more likely during cold rolling. In particular, when the Si content exceeds 3.5%, the difficulty of rolling increases significantly. Also, as the Si and Al content increases, the magnetic induction of the steel sheet is reduced. In this application, by controlling the Si content to 3.0~3.4% and the Al content to 0.80~1.0%, high-frequency iron loss is reduced, the strength of the steel sheet is improved, and the O content in the molten steel is significantly reduced, creating conditions for ultra-low S smelting. By controlling the chemical composition (P, Sn+Sb), the cast billet is naturally cooled to 400-500°C, then heated to 1080-1100°C at a heating rate of 10°C / min or less, followed by 0.5-1.0h of heat retention before hot rolling, and then normalized at a low temperature of 830-870°C. Furthermore, by preheating the steel sheet to 100-200°C before cold rolling, stable production is possible without edge cracking during hot rolling, and stable production with a large reduction ratio is possible during cold rolling, with a sheet fracture rate of less than 0.5% during cold rolling. In addition, the above low-temperature normalizing process imparts high magnetic induction to the final product.

[0021] Mn 0.2~0.4%: Adding an appropriate amount of Mn is advantageous for improving the magnetic properties of steel sheets and also for improving the strength of steel sheets. Mn suppresses thermal brittleness caused by S and readily forms coarse MnS precipitates together with S, reducing iron loss in steel sheets. Since Mn alloys are relatively expensive, the Mn content is controlled to 0.2~0.4% in this application to take cost into consideration. In this application, the S content is ≤0.0010%, so the Mn / S ratio is high, which can promote the precipitation and growth of MnS, and is advantageous for magnetic properties.

[0022] P ≤ 0.01%: P does not significantly affect magnetism, and increasing its content can improve the strength of the steel sheet. However, in the case of high-grade non-oriented silicon steel, a high P content significantly increases the difficulty of cold rolling, making sheet fracture more likely during rolling. In this application, the control concept is to obtain high strength by controlling the fine crystal structure of the final product through a high Si and high Al component design and a thin specification design. Since the thickness of the final product is obtained in a single cold rolling, it is necessary to control P to ≤ 0.01% in order to improve the rollability of the steel sheet and simplify the manufacturing process.

[0023] Sn+Sb≦0.004%: Both Sn and Sb are grain boundary segregation elements. The purpose of adding Sn alone, Sb alone, or a combination of Sn and Sb to non-oriented silicon steel is to reduce the proportion of undesirable textures in {111} due to grain boundary segregation of Sn and Sb, thereby improving the magnetic induction of the final product. This effect is particularly pronounced in production processes without a normalizing step. However, the grain boundary segregation behavior of Sn and Sb causes the grain boundaries of the steel sheet to become brittle, making sheet fracture more likely during cold rolling and making production more difficult. In this application, since the proportion of undesirable textures in the final product {111} can be significantly reduced by performing a normalizing treatment on the hot-rolled coil before cold rolling, Sn and Sb are intentionally not added when designing the composition, and Sn+Sb is controlled to 0.004% or less, in order to ensure the rollability of the steel sheet and simplify the manufacturing process.

[0024] Nb≦0.005%, V≦0.005%, Ti≦0.005%, Mo≦0.005%, Cr≦0.05%, Ni≦0.05%, Cu≦0.05%: Nb, V, Ti, Mo, Cr, Ni, and Cu reduce the grain size of the final product of non-oriented silicon steel, resulting in a decrease in the magnetic properties of the non-oriented silicon steel under low-frequency conditions, such as increased iron loss and decreased magnetic induction strength. In this application, non-oriented silicon steel for high-speed motors requires low iron loss under high-frequency operating conditions in the final product, and the grain size needs to be appropriately reduced to reduce eddy current loss. Therefore, in this application, the presence of appropriate content of Nb, V, Ti, Mo, Cr, Ni, and Cu in the non-oriented silicon steel for high-speed motors allows for a reduction in the grain size of the final product of non-oriented silicon steel. This not only improves strength but also helps to reduce high-frequency eddy current loss. However, considering the relatively high alloy prices of these elements, this application aims to reduce the difficulty of steelmaking by appropriately broadening the control requirements rather than intentionally adding them. The elements are controlled to Nb ≤ 0.005%, V ≤ 0.005%, Ti ≤ 0.005%, Mo ≤ 0.005%, Cr ≤ 0.05%, Ni ≤ 0.05%, and Cu ≤ 0.05%.

[0025] Iron loss in non-oriented silicon steel includes three components: hysteresis loss, eddy current loss, and anomalous loss. Hysteresis loss is energy loss caused by a hysteresis phenomenon in which the magnetic induction strength lags behind the change in magnetic field strength, resulting from the obstruction of magnetic domain wall movement and the resulting hindering of magnetic flux changes during the magnetization and demagnetization process of magnetic materials due to factors such as inclusions, crystal defects, internal stresses, and crystal orientation in the material. Eddy current loss is energy loss caused by the generation of eddy currents by local electromotive forces induced around the magnetic flux according to Faraday's law of electromagnetic induction when the magnitude and direction of the magnetic flux change during the alternating magnetization process of magnetic materials. In other words, when magnetic domain walls move, the magnetization changes rapidly, eddy current loss occurs, and can be calculated according to the classical eddy current loss formula. Anomaly loss is energy loss caused by differences in magnetic domain structure when the material is magnetized, and accounts for a small proportion of iron loss.

number

[0026] From the above, it was found that hysteresis loss, eddy current loss, and abnormal loss are all energy losses that occur during the magnetization and demagnetization process of magnetic materials. Since abnormal loss accounts for a small proportion of iron loss, hysteresis loss and eddy current loss are generally the focus of attention. Hysteresis loss P h =k h *f*B 2 , eddy current loss P e =k e *f 2 *B 2 Therefore, at the power supply frequency (50Hz), hysteresis loss accounts for approximately 70% and eddy current loss accounts for approximately 30%. From the formulas for hysteresis loss and eddy current loss, P h f is proportional to P e f2 is proportional to the iron loss, and therefore, as the frequency increases, eddy current loss increases significantly within the iron loss. At low frequencies (50Hz to 400Hz), hysteresis loss accounts for the majority of the iron loss, while at high frequencies (≥1000Hz), eddy current loss accounts for the majority of the iron loss.

[0027] Because the composition of low-frequency iron loss and high-frequency iron loss are different, this invention employs a completely different design philosophy from conventional non-oriented silicon steel.

[0028] Conventional design philosophy for non-oriented silicon steel: Under low-frequency conditions, the proportion of hysteresis loss increases for non-oriented silicon steel of the same composition. Therefore, process design generally requires focusing on large crystal grains in the final product. Because grain boundaries hinder the movement of magnetic domain walls, the number of crystal grains increases, the number of grain boundaries decreases, hysteresis loss decreases, and iron loss decreases. Designing the final product to have large crystal grains is advantageous for reducing low-frequency iron loss, but an increase in crystal grains reduces the strength of the steel sheet. In other words, under low-frequency conditions, controlling the crystal grain size creates a contradiction between low iron loss and high strength. To reduce iron loss, it is necessary to increase the crystal grain size and improve strength through strengthening methods such as solid solution strengthening, precipitation strengthening, or dislocation strengthening. For example, in composition design, this involves adding alloying elements such as Cu, Cr, Ni, Nb, V, and Ti, and in process design, it involves performing incomplete recrystallization annealing or secondary cold rolling, or a combination of the above two methods.

[0029] Design philosophy for non-oriented silicon steel in this application: Under high-frequency conditions, in the case of non-oriented silicon steel with the same composition, the proportion of eddy current loss is high, so there is no need to pursue large crystal grains in the final product during process design. This is because as the crystal grain size increases, the grain boundaries decrease, the movement speed of magnetic domains increases, the magnetization changes rapidly, and the eddy current loss increases. In other words, under high-frequency conditions, by reducing the crystal grain size, the eddy current loss, which accounts for the largest proportion of high-frequency iron loss, can be reduced. Although hysteresis loss increases, the overall high-frequency iron loss decreases. In addition, the strength of the steel sheet can be improved by refining the crystal grains. That is, under high-frequency conditions, low iron loss and high strength are organically integrated in terms of crystal grain size control, and fine-grain strengthening and low iron loss at high frequencies can be achieved simultaneously by controlling the crystal grain size.

[0030] The present invention also provides a method for producing non-oriented silicon steel for high-speed motors, comprising the steps of smelting to cast a continuous cast billet, cooling the continuous cast billet, and performing heating, hot rolling, normalizing, pickling, cold rolling, annealing, and coating treatments.

[0031] Furthermore, the normalizing temperature is 830 - 870°C, the holding time is 3 - 5 min, the cold rolling reduction rate is controlled to be 89% - 90%, the annealing temperature is 880 - 900°C, and the holding time is 120 - 150 s.

[0032] Furthermore, it is smelted using a vacuum induction furnace, controlled to 0 < C + S + N ≤ 0.0050%, and a continuous casting billet with a thickness of 200 - 250 mm is cast.

[0033] Furthermore, in the steps of cooling and heating the casting billet, after the casting billet is naturally cooled to 400 - 500°C, it is heated to 1080 - 1100°C at a heating rate of 10°C / min or less, and then held for 0.5 - 1.0 h.

[0034] Furthermore, the hot rolling includes 6 rough rolling passes and 7 finish rolling passes, and / or An intermediate billet with a thickness of 30 - 45 mm is obtained by rough rolling, and a hot rolled sheet with a thickness of 2.0 - 3.0 mm is obtained by finish rolling, and / or The final rolling temperature of the finish rolling is 800 - 860°C, the coiling temperature is 600 - 660°C, the variation range of the final rolling temperature and the coiling temperature of the finish rolling is ±15°C, and the total reduction rate of the finish rolling is 92.5 - 93.5%.

[0035] Furthermore, after normalizing, the steel plate is cooled to 80 - 150°C, and then shot blasting and pickling processes are carried out.

[0036] For pickling, existing conventional reagents such as hydrochloric acid can be used. The temperature of the acid solution is 75 - 85°C, and the concentration of hydrochloric acid in the acid solution is 120 - 160 g / L.

[0037] Furthermore, before cold rolling, the steel plate is preheated to 100 - 200°C, and / or the recrystallized grain size after normalizing is 60 - 80 μm, and the volume ratio of the recrystallized structure is 100%.

Advantages of the Invention

[0038] The technical solution of the present application has the following advantages.

[0039] 1. The non-oriented silicon steel for high-speed motors according to the present application has a chemical composition of C≤0.0020% by mass, S≤0.0010% by mass, N≤0.0030% by mass, Si: 3.0 - 3.4% by mass, Al: 0.80 - 1.0% by mass, Mn: 0.2 - 0.4% by mass, P≤0.01% by mass, Sn + Sb≤0.004% by mass, Nb≤0.005% by mass, V≤0.005% by mass, Ti≤0.005% by mass, Mo≤0.005% by mass, Cr≤0.05% by mass, Ni≤0.05% by mass, Cu≤0.05% by mass, and the rest is Fe and inevitable impurities, and 0 < C + S + N≤0.0050%. The thickness of the final product is 0.20 - 0.30 mm, and the grain size of the final product is 80 - 100 μm. By accurately controlling the chemical composition and controlling the thickness and grain size of the final product, the strength is improved, and the high-frequency iron loss P 1.0 / 1000 is reduced. Moreover, the smelting cost is low, the production process is simple, the production cost is low, and it meets the requirements for the use of high-speed motors with high rotational speed, small size, and high efficiency. There is no need to additionally add alloy strengthening elements such as Cu, Cr, Ni, Nb, V, and Ti, and there is also no need to add grain structure control elements such as Sn and Sb.

[0040] 2. In the final product of the non-oriented silicon steel for high-speed motors according to the present application, the yield strength is ≥550 MPa, the magnetic induction B 5000 is ≥1.65, and the high-frequency iron loss P 1.0 / 1000 is ≤45 W / kg at a thickness of 0.30 mm, the high-frequency iron loss P 1.0 / 1000 is ≤40 W / kg at a thickness of 0.25 mm, and the high-frequency iron loss P 1.0 / 1000 is ≤35 W / kg at a thickness of 0.20 mm. It can meet the needs of the rapid development of future high-speed motors.

[0041] 3. The present invention relates to a method for manufacturing non-oriented silicon steel for high-speed motors, comprising the steps of smelting to cast a continuous casting billet, cooling the continuous casting billet, and performing heating, hot rolling, normalizing, pickling, cold rolling, annealing, and coating treatments. The production flow is short and production efficiency is high. By controlling the chemical composition and designing the overall process of the above flow, the contradictions between high-frequency iron loss, magnetic induction, and strength are harmonized by utilizing means such as resistivity control, inclusion control, texture control, and grain size control, and high strength, high magnetic properties, and excellent high-frequency magnetic properties are achieved.

[0042] 4. The method for manufacturing non-oriented silicon steel for high-speed motors according to this invention can avoid cracking of high-silicon steel casting billets and ensure smooth hot rolling by controlling the content of P, Sn, and Sb elements in the composition design and controlling the temperature of natural cooling and heating rate of the casting billet. By controlling the recrystallization grain size after normalizing and preheating before cold rolling, a single cold rolling of high-silicon steel with a large reduction ratio can be achieved, and a final product with a thickness of 0.20 to 0.30 mm can be obtained in a single annealing, resulting in a short production flow and high production efficiency.

[0043] 5. The present invention provides a method for manufacturing non-oriented silicon steel for high-speed motors, which involves normalizing by holding the sheet at 830-870°C for 3-5 minutes and then heating it at a low temperature for a long time. This not only achieves complete recrystallization of the hot-rolled sheet but also avoids excessive grain size, resulting in a grain size of 60-80 μm. The reason for controlling the cold-rolling reduction ratio to 89-90% is to increase the stored energy and nucleation points, enhance the annealing nucleation rate, and create conditions for accurately and stably controlling the grain size of the final product during the annealing process. Combined with annealing at 880-900°C for 120-150 seconds, and precise control of the chemical composition, the above three process conditions ensure complete recrystallization, and the grain size of the final product is controlled to 80-100 μm. [Modes for carrying out the invention]

[0044] The following examples are provided to better understand the present application. The present application is not limited to the aforementioned best embodiment, and the following examples do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone's suggestion of the present application or combination of the features of the present application and other prior arts falls within the protection scope of the present application.

[0045] When specific experimental steps or conditions are not specified in the examples, they may be carried out according to the operations or conditions of the normal experimental steps described in the literature of the relevant field. The reagents or instruments used are not specified by the manufacturer, and all are ordinary reagent products that can be obtained commercially.

[0046] Examples 1 to 8 each provide non-oriented silicon steel for high-speed motors, and their chemical compositions are shown in Table 1 in mass percentage, and the rest are Fe and inevitable impurities. Also, the non-oriented silicon steel for high-speed motors manufactured in each example is specifically a steel plate with the thickness shown in Table 1.

[0047]

Table 1

[0048] The non-oriented silicon steel for high-speed motors in each example of the present application is produced according to the following steps.

[0049] (1) Smelt using a vacuum induction furnace, control 0<C+S+N≦0.0050%, and cast a continuous casting billet with a thickness of 220 mm. The chemical composition of the continuous casting billet is shown in Table 1. Nb, V, Ti, Mo, Cr, Ni, and Cu are not intentionally added during the smelting process, but appropriately expand the requirements of these controls to control Nb≦0.005%, V≦0.005%, Ti≦0.005%, Mo≦0.005%, Cr≦0.05%, Ni≦0.05%, Cu≦0.05%. This reduces the difficulty of steelmaking.

[0050] (2) The continuous casting billets obtained in step (1) were stacked and allowed to cool naturally to 450°C, then sent to a heating furnace and heated at a heating rate of 5°C / min and held at that temperature. The heating temperature and holding time are shown in Table 2.

[0051] (3) The continuously cast billet heated in step (2) was subjected to rough rolling and finish rolling. A 1+5 mode was used for rough rolling, and an intermediate billet was obtained after 6 rolling cycles. Subsequently, 7 finish rolling cycles and winding were performed to obtain a hot-rolled sheet coil. The thickness of the intermediate billet obtained by rough rolling, the final rolling temperature of the finish rolling, the total reduction ratio at the finish pressure, the thickness of the obtained hot-rolled sheet, and the winding temperature are shown in Table 2.

[0052] (4) The hot-rolled sheet coil obtained in step (3) is normalized in a pure dry N2 atmosphere, and the normalizing temperature and normalizing time are shown in Table 3. After normalizing, the steel sheet is cooled to 100°C, shot blasted, and then pickled with hydrochloric acid, with the temperature of the acid solution being 80°C, the concentration of hydrochloric acid in the acid solution being 140 g / L, and the Fe in the pickling solution. 2+ The mass concentration of the solution was controlled to 50 ± 20 g / L. The microstructure of the normalized steel sheets in each example was detected, and the measured volume percentage of the recrystallized structure and the recrystallized grain size are shown in Table 3.

[0053] (5) The normalized and pickled steel sheet obtained in step (4) is preheated, and then cold-rolled. The preheating temperature, thickness before rolling, thickness after rolling, and reduction ratio of the cold-rolled sheet are shown in Table 4.

[0054] (6) The fully hardened steel sheet obtained in step (5) was subjected to continuous annealing in an atmosphere of H2 and N2 mixed gas. The H2 content was 15%. The annealing temperature and holding time are shown in Table 4.

[0055] (7) The steel plates obtained in step (6) were coated and finished according to conventional methods.

[0056] [Table 2]

[0057] [Table 3]

[0058] [Table 4]

[0059] Comparative Example Comparative Examples 1 to 8 each provide non-oriented silicon steel, and their chemical composition (mass%) is shown in Table 5. Specifically, the non-oriented silicon steel produced in each comparative example is a steel sheet having the thickness shown in Table 5.

[0060] [Table 5]

[0061] The non-oriented silicon steels in Comparative Examples 1 to 8 were all produced in accordance with the design philosophy of non-oriented silicon steel for low-frequency applications.

[0062] In Comparative Examples 1-3, controlling the normalizing temperature and holding time increased the recrystallized grain size after normalizing. Furthermore, combining this with control of the cold rolling reduction ratio, annealing temperature, and holding time resulted in larger crystal grains in the final product. Specific process parameters are shown in Tables 6-8.

[0063] In Comparative Examples 4-6, based on Comparative Examples 1-3, the Nb and Ti content was increased in the composition design, and the strength of the steel sheet was improved by solid solution strengthening with the minute alloying elements Nb and Ti and the strengthening effect of the fine grains.

[0064] In Comparative Example 7, the increase in Si content in the component design exceeds the scope of the present invention, making sheet fracture more likely during cold rolling. Therefore, in Comparative Example 8, based on Comparative Example 7, the thickness of the final product is increased to 0.35 mm to reduce the risk of sheet fracture.

[0065] The steps for producing the non-oriented silicon steel of Comparative Examples 1 to 8 are as follows:

[0066] (1) The material was smelted using a vacuum induction furnace and cast into a 220 mm thick continuous casting billet. The chemical composition of the continuous casting billet is shown in Table 5.

[0067] (2) The continuous casting billets obtained in step (1) were stacked and allowed to cool naturally to 450°C, then sent to a heating furnace and heated at a heating rate of 5°C / min and kept warm. The heating temperature and warming time are shown in Table 6.

[0068] (3) The continuously cast billet heated in step (2) was subjected to rough rolling and finish rolling. A 1+5 mode was used for rough rolling, and an intermediate billet was obtained after 6 rolling cycles. Subsequently, 7 finish rolling cycles and winding were performed to obtain a hot-rolled sheet coil. The thickness of the intermediate billet obtained by rough rolling, the final rolling temperature of the finish rolling, the total reduction ratio in the finish rolling, the thickness of the obtained hot-rolled sheet, and the winding temperature are shown in Table 6.

[0069] (4) The hot-rolled sheet coil obtained in step (3) is normalized in a pure dry N2 atmosphere, and the normalizing temperature and normalizing time are shown in Table 7. After the normalized steel sheet is cooled to 100°C, it is shot-blasted, and then pickled with hydrochloric acid, with the temperature of the acid solution being 80°C and the concentration of hydrochloric acid in the acid solution being 140 g / L, Fe 2+ The mass concentration was controlled to 50 ± 20 g / L. The microstructure of the normalized steel sheets in each comparative example was detected, and the measured volume percentage of the recrystallized structure and the recrystallized grain size are shown in Table 7.

[0070] (5) The normalized and pickled steel sheet obtained in step (4) was preheated, and then cold-rolled. The preheating temperature, thickness before rolling, thickness after rolling, and reduction ratio during cold rolling are shown in Table 8. In Comparative Example 7, sheet fracture occurred during cold rolling, and the rolling was not completed.

[0071] (6) The rolled hardened steel sheet obtained in step (5) was subjected to continuous annealing in an atmosphere of H2 and N2 mixed gas. The H2 content was ≥15%. The annealing temperature and holding time are shown in Table 8.

[0072] (7) The steel plates prepared in step (6) were coated and finished according to conventional methods.

[0073] [Table 6]

[0074] [Table 7]

[0075] [Table 8]

[0076] The recrystallized grain size, volume percentage (%) of the recrystallized structure, yield strength, tensile strength, and iron loss P of the non-oriented silicon steel produced in Examples 1-8, Comparative Examples 1-6, and Comparative Example 8 are as follows: 1.0 / 1000 The magnetic induction intensity B of the non-oriented silicon steel produced in Examples 1-8 and Comparative Examples 4-6 was measured and measured. 5000 The following measurements were taken. These results are shown in the table below.

[0077] [Table 9]

[0078] As can be seen from the above embodiments 1 to 8, when non-oriented silicon steel for high-speed motors is used according to the embodiments of the present invention, it not only has high strength and high magnetic induction, but also high-frequency iron loss P 1.0 / 1000 It has low production costs, low smelting costs, a simple production process, low production costs, and meets the application requirements for high-speed motors.

[0079] In Comparative Examples 1-3, similar chemical compositions to those in Examples 1-3 were used, and large crystal grains were obtained in the final product by controlling the normalizing temperature, holding time, cold rolling reduction ratio, annealing temperature, and holding time. However, the strength of the final product was much lower than that of Examples 1-3, and the high-frequency iron loss P for the same final product thickness was lower. 1.0 / 1000 It was much larger than in Examples 1-3.

[0080] Comparative Examples 4-6 were based on Comparative Examples 1-3, but with increased Nb and Ti content in the composition design. Due to solid solution strengthening by the minute alloying elements Nb and Ti and the strengthening effect of fine grains, the strength of Comparative Examples 4-6 was slightly improved compared to the steel sheets of Comparative Examples 1-3. Measurement results showed that the crystal grain size was smaller than that of Comparative Examples 1-3, and the strength was higher than that of Comparative Examples 1-3. Compared with Examples 1-3, Comparative Examples 4-6 had lower strength, higher iron loss, lower magnetic induction, and higher alloy cost for the same final product thickness.

[0081] In Comparative Example 7, the Nb and Ti content was not increased in the composition design, but the Si content was increased to 3.5% or more. As a result, when rolling a steel sheet with a desired thickness of 0.30 mm, sheet fracture occurred during cold rolling, even when the preheating temperature before rolling was increased to 180°C.

[0082] In Comparative Example 8, based on Comparative Example 7, the thickness of the final product was increased to 0.35 mm. Due to the increase in the thickness of the steel plate, its resistivity decreased, and as a result, the high-frequency iron loss of the final product was significantly greater than that of Examples 1 to 8.

[0083] Clearly, the above embodiments are merely illustrative examples and do not limit the embodiments. Those skilled in the art may make various other forms of variations or modifications based on the above description. It is neither necessary nor possible to cover all embodiments here. Any obvious variations or modifications derived therefrom remain within the scope of the present invention.

Claims

1. Non-oriented silicon steel sheet for high-speed motors, The chemical components are C≦0.0020 mass%, S≦0.0010 mass%, N≦0.0030 mass%, Si: 3.0 to 3.4 mass%, Al: 0.80 to 1.0 mass%, Mn: 0.2 to 0.4 mass%, P≦0.01 mass%, Sn+Sb≦0.004 mass%, Nb≦0.005 mass%, V≦0.005 mass%, Ti≦0.005 mass%, Mo≦0.005 mass%, The composition is Cr ≤ 0.05 mass%, Ni ≤ 0.05 mass%, Cu ≤ 0.05 mass%, the remainder being Fe and unavoidable impurities, 0 < C + S + N ≤ 0.0050%, the final product thickness is 0.20 to 0.30 mm, the final product grain size is 80 to 100 μm, the non-oriented silicon steel sheet for high-speed motors has a yield strength ≥ 550 MPa, and magnetic induction B ５０００ The value is ≥1.65T, and the high-frequency iron loss P is 0.30 mm thick. １．０／１０００ High-frequency iron loss P at ≤45 W / kg and 0.25 mm thickness １．０／１０００ High-frequency iron loss P at ≤40 W / kg and 0.20 mm thickness １．０／１０００ A non-oriented silicon steel sheet for high-speed motors, characterized by having a wattage of ≤35 W / kg.

2. The non-oriented silicon steel sheet for high-speed motors according to Claim 1, characterized in that the (Si+2Al) content is 4.8% by weight or more and 5.2% by weight or less.

3. A method for manufacturing a non-oriented silicon steel sheet for a high-speed motor according to Claim 1, The process includes the steps of smelting to cast a continuous cast billet, cooling the continuous cast billet, and then heating, hot rolling, normalizing, pickling, cold rolling, annealing, and coating. The normalizing temperature is 830-870°C, the holding time is 3-5 min, the cold rolling reduction is controlled to 89-90%, the annealing temperature is 880-900°C, and the holding time is 120-150 s. The material is smelted using a vacuum induction furnace, controlled to 0 < C + S + N ≤ 0.0050%, and a continuous casting billet with a thickness of 200-250 mm is cast. The steps for cooling and heating the cast billet are as follows: the cast billet is naturally cooled to 400-500°C, then heated to 1080-1100°C at a heating rate of 10°C / min or less, and then kept at a constant temperature for 0.5-1.0 hours. The hot rolling process includes six rough rolling steps and seven finish rolling steps. Rough rolling yields intermediate billets with a thickness of 30 to 45 mm, and finish rolling yields hot-rolled plates with a thickness of 2.0 to 3.0 mm. A method for manufacturing non-oriented silicon steel sheets for high-speed motors, wherein the final rolling temperature of the finish rolling is 800 to 860°C, the winding temperature is 600 to 660°C, the deviation of the final rolling temperature of the finish rolling from the target value and the deviation of the winding temperature of the finish rolling from the target value are both within ±15°C, and the total reduction ratio of the finish rolling is 92.5 to 93.5%.

4. The method for manufacturing a non-oriented silicon steel sheet for a high-speed motor according to claim 3, characterized in that after normalizing, the steel sheet is cooled to 80 to 150°C, and then shot blasting and pickling are performed.

5. The method for producing a non-oriented silicon steel sheet for high-speed motors according to claim 3, characterized in that the steel sheet is preheated to 100 to 200°C before cold rolling, and / or the recrystallized grain size after normalizing is 60 to 80 μm, and the volume percentage of the recrystallized structure is 100%.

6. The non-oriented silicon steel sheet for high-speed motors according to claim 1, characterized in that the chemical composition is Si: 3.1 to 3.4 mass%, and Nb: 0.002 to 0.004 mass%.

7. The non-oriented silicon steel sheet for high-speed motors according to claim 1, characterized in that the yield strength is 569 MPa or higher.

8. The method for manufacturing non-oriented silicon steel sheets for high-speed motors according to claim 3, characterized in that the recrystallized grain size after normalizing is 64 to 76 μm.

Images