Low-noise non-oriented silicon steel for driving motor of electric vehicle and production method of low-noise non-oriented silicon steel

Abstract

The invention discloses a production method of low-noise non-oriented silicon steel for a driving motor of an electric vehicle, and the non-oriented silicon steel with the thickness ranging from 0.20 mm to 0.30 mm is prepared through the sequential steps of steelmaking, continuous casting, hot rolling, normalizing, pickling, cold rolling, annealing and coating. Aiming at the noise level improvement requirement of a driving motor of an electric vehicle, on the premise of considering the production feasibility of non-oriented silicon steel, on one hand, the average grain size of a non-oriented silicon steel hot-rolled coil after normalization is controlled according to the content of Si and Al in steel; on the other hand, cold rolling parameters are controlled by optimizing the cold rolling pass, the roller diameter and the inlet and outlet thickness of each pass, the texture of a finished product is controlled on the premise that the cold rolling property is guaranteed, and therefore the low-loss and low-noise non-oriented silicon steel for the driving motor of the electric vehicle is obtained, the product thickness ranges from 0.2 mm to 0.3 mm, the frequency ranges from 400 Hz, and the production cost is low. Under 1.0 T, the average magnetostriction coefficient lambda p-p parallel to the rolling direction and perpendicular to the rolling direction is smaller than or equal to 10 * 10 <-6 >, the average weighted sound level decibel value AWV (dBA) is smaller than or equal to 100, and the average loss P1.0 / 400 is smaller than or equal to 9 + 50 * t2W / kg.

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing non-oriented electrical steel, and particularly relates to a low-noise non-oriented electrical steel for an electric vehicle drive motor and a production method thereof. Background Art

[0002] In recent years, new energy vehicles have been changing the global automotive industry at an unprecedented speed, depth, and breadth, not only endowing the development of the global automotive industry with new impetus but also bringing historical opportunities to reshape the world's automotive energy pattern, address global climate change, and achieve sustainable development of the automotive industry. As the heart of new energy vehicles, the performance of the drive motor is directly related to the endurance and driving performance of new energy vehicles.

[0003] Noise is one of the important indicators of the drive motor, which can be roughly divided into mechanical noise, electromagnetic noise, and pneumatic noise. Among them, the mechanism of electromagnetic noise is relatively complex, and the sound quality is poor. It often appears as a high-frequency whistle, which is likely to cause discomfort to people. Electromagnetic noise is one of the main sources of noise in a variable-speed permanent magnet synchronous motor. The air-gap magnetic field of the motor acts on the stator core of the motor to generate electromagnetic force, and the electromagnetic force causes the vibration of the stator core, thereby generating electromagnetic noise. The main sources of electromagnetic noise are Maxwell force and magnetostrictive force. The Maxwell force mainly exists in the air gap, where the relative magnetic permeability of the material is discontinuously distributed. The Maxwell force acting on the top of the stator teeth is the main reason for the vibration of the stator core of a rotating motor. When the non-oriented electrical steel of the core material is magnetized, the size of the material will change due to the magnetostrictive force. Therefore, magnetostriction is an important source of core vibration and noise, and the magnetostrictive characteristics of the non-oriented electrical steel used for the drive motor are crucial for motor noise control.

[0004] Chinese patent CN116426810A discloses a method for manufacturing high-frequency, low-iron-loss, non-oriented silicon steel for new energy vehicle drive motors. First, alloy and molten iron are smelted in a smelting furnace in proportion to obtain molten steel, wherein Si: 2.8%-3.2%, Al: 1.0-1.5%; the molten steel is smelted in a converter and continuously cast, and the ingot is heated to 1100-1220°C; after conventional hot rolling to a hot-rolled plate with a thickness of 2.0 mm, normalizing annealing is performed at a temperature of 900-1200°C for a normalizing time of 100 s-240s; then cold rolling to the finished thickness to obtain a non-oriented silicon steel sheet of 0.25±0.005mm; finally recrystallization annealing; the annealing heating rate is 70-100℃ / s; the annealing atmosphere in the soaking section of the recrystallization annealing process adopts a non-oxidizing atmosphere with a partial pressure ratio of P(H2O) / P(H2)=0.0002-0.0005; cooling after recrystallization annealing, the cooling rate is 7-10℃ / s; finally, an insulating coating is applied and dried at 300-550℃. This technology is designed for typical high Si and Al components. The highest normalizing temperature reaches 1200℃, which can easily lead to coarse normalized structure and decreased toughness during cold deformation processing. The highest heating temperature of the ingot is 1220℃. The solid solubility of inclusions such as AlN and MnS is significantly increased. A large amount of precipitation during the subsequent hot rolling cooling process hinders the subsequent recrystallization growth and deteriorates the magnetic properties. The introduction of H2O atmosphere during the recrystallization annealing process is likely to form an inner oxide layer, which will also deteriorate the magnetic properties.

[0005] In addition, in the prior art, some non-oriented silicon steels for new energy vehicle drive motors are added with relatively expensive Sn, Sb, etc., and the magnetic properties are improved by these segregation elements, but the cost is relatively high; some are added with Cu, which is easy to precipitate fine Cu2S during the hot rolling process, hindering the recrystallization growth and deteriorating the magnetic properties, and making pickling difficult after normalization, affecting the surface quality of the finished product. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for producing low-noise non-oriented silicon steel for electric vehicle drive motors in view of the deficiencies of the above-mentioned prior art. The product thickness t is in the range of 0.2mm to 0.3mm, and its performance index reaches the average magnetostriction coefficient λp-p ≤ 10×10 at 400Hz and 1.0T in parallel to the rolling direction and perpendicular to the rolling direction. -6 , average weighted sound level decibel value AWV (dBA) ≤ 100, average loss P 1.0 / 400 ≤9+50×t 2 W / kg.

[0007] The technical solution adopted by the present invention to solve the above-mentioned problems is:

[0008] A production method of low-noise non-oriented silicon steel for an electric vehicle drive motor, which prepares non-oriented silicon steel with a thickness in the range of 0.20 mm to 0.30 mm through steelmaking, continuous casting, hot rolling, normalizing, pickling, cold rolling, annealing, and coating in sequence. Specifically, it includes the following steps:

[0009] 1) Molten steel smelting and continuous casting: After desulfurization of hot metal, it is smelted in a converter to obtain molten steel with the target composition; this molten steel enters the mold for initial solidification and forming, and the obtained billet with a liquid core is pulled out from the mold and enters the secondary cooling zone for continuous cooling and solidification until it is completely solidified to form a billet;

[0010] 2) Billet heating and hot continuous rolling: The above billet is heated and heat-insulated evenly in a tunnel furnace, and then enters a hot continuous rolling mill for hot continuous rolling, and a hot rolled coil is obtained after coiling;

[0011] 3) Normalize and pickle the above hot rolled coil to obtain a pickled hot rolled coil; among them, the average grain size D after normalizing the hot rolled coil satisfies:

[0012] 160 - (3Si% + Al%) × 10 3 ≤ D ≤ 170 - (2Si% + Al%) × 10 3

[0013] The unit of D is μm, Si% is the weight percentage content of Si in the steel; Al% is the weight percentage content of Al in the steel;

[0014] 4) Cold roll the pickled hot rolled coil once to obtain a cold rolled coil; among them, the cold rolling parameter M ranges from 3.0 to 6.5, and the calculation formula of M is as follows:

[0015]

[0016] In the above formula, n is the number of rolling passes, H i is the entrance thickness of the i-th pass, H i+1 is the exit thickness of the i-th pass (i.e., the entrance thickness of the i + 1-th pass), and Ri is the roll diameter of the work roll; in this formula, H i 、H i+1 and Ri adopt the same length unit;

[0017] 5) Anneal and coat the cold rolled coil finished product, and finally obtain non-oriented silicon steel with a thickness in the range of 0.20 mm to 0.30 mm.

[0018] According to the above scheme, in step 1), the molten steel composition meets 2.5% ≤ Si% ≤ 4.0% and Al% ≤ 1.5%, 0.15% ≤ Mn% ≤ 1.0% by weight percentage.

[0019] According to the above solution, in step 1), during continuous casting, the casting speed is controlled at 0.7 - 1.1 m / min, and the superheat is 10 - 30 °C; the cooling system of the continuous caster: the cooling water flow rate on the narrow side of the mold is 25 - 45 m 3 / h, the cooling water flow rate on the wide side of the mold is 290 - 370 m 3 / h, and the secondary cooling intensity is 1.8 - 3.2 L / kg.

[0020] According to the above solution, in step 2), the temperature of the continuous casting slab entering the tunnel furnace is ≥400 °C, the soaking temperature is 1000 - 1150 °C, and the soaking time is 60 - 90 min; after the continuous casting slab leaves the furnace, it enters the hot continuous rolling mill for hot continuous rolling. The finishing rolling temperature of the rough rolling is ≥940 °C, the thickness of the intermediate slab is 25 - 35 mm, the finishing rolling temperature of the finishing rolling is ≥840 °C, and the coiling temperature after laminar cooling is 550 °C - 680 °C.

[0021] According to the above solution, in step 3), the hot rolled steel coil enters the normalizing furnace for heat treatment. The soaking section temperature of the normalizing furnace is 820 - 1050 °C, the soaking section time is 90 - 120 s, and after normalizing, the hot rolled coil is pickled, and the acid tank uses hydrochloric acid with a concentration of 6 - 12%.

[0022] Furthermore, when 2.5% ≤ Si% ≤ 3.0% and (Si + Al)% < 4.0%, the soaking section temperature of the normalizing furnace is greater than 1000 °C and does not exceed 1050 °C;

[0023] When 2.5% ≤ Si% ≤ 3.0% and 4.0% ≤ (Si + Al)% ≤ 4.5%, the soaking section temperature of the normalizing furnace is greater than 950 °C and does not exceed 1000 °C;

[0024] When 3.0% < Si% ≤ 4.0% and (Si + Al)% < 4.2%, the soaking section temperature of the normalizing furnace is greater than 880 °C and does not exceed 950 °C;

[0025] When 3.0% < Si% ≤ 4.0% and 4.2% ≤ (Si + Al)% ≤ 5.5%, the soaking section temperature of the normalizing furnace is 820 - 880 °C.

[0026] According to the above solution, in step 4), the hot rolled coil after normalizing and pickling is heated by an induction heating furnace to ensure that the actual temperature at the entrance of the cold rolling mill reaches 60 - 150 °C.

[0027] According to the above solution, in step 5), a continuous annealing furnace is used. In the radiant tube heating and warming section, it is heated at a heating rate of 30 - 60 °C to 900 - 1050 °C and then enters the soaking section for soaking heat treatment, and then enters the gas protection circulation cooling section to cool at a rate of ≤15 °C to below 100 °C; the coating uses a conventional phosphate coating, and the coating thickness is controlled at 0.3 - 0.7 μm.

[0028] The non-oriented electrical steel with low noise produced by the above method has a product thickness in the range of 0.20 mm to 0.30 mm, and its performance indicators are as follows: at 400 Hz and 1.0 T, the average magnetostriction coefficient λp-p parallel and perpendicular to the rolling direction ≤ 10×10 -6 , the average weighted sound level decibel value AWV (dBA) ≤ 100, and the average loss P 1.0 / 400 ≤ 9 + 50×t 2 W / kg (t is the finished product thickness, and 0.20 mm ≤ t ≤ 0.30 mm), that is, P 1.0 / 400 is 11 - 13.5 W / kg.

[0029] The production method of the above non-oriented electrical steel with low noise for an electric vehicle drive motor provided by the present invention is described in detail for its technical improvement concept as follows:

[0030] The normalized average grain size directly affects the average grain size and texture components after annealing. Si and Al promote grain growth during normalization. The higher the normalization temperature and the longer the soaking time, the larger the average grain size, which significantly reduces the strength of the unfavorable γ texture. Due to the heredity of the tissue texture, the grain size after finished product annealing is also larger, and the strength of the unfavorable γ texture decreases accordingly, while the strength of the favorable α and λ textures increases, and the average iron loss and magnetostriction coefficient decrease. Therefore, the present invention defines that the average grain size D after normalization ≥ 160 - (3Si% + Al%)×10 3 .

[0031] When the normalized average grain size is too large, it results in too large an average grain size of the finished product after annealing. The reduction in hysteresis loss at medium and high frequencies decreases, while the eddy current loss, which accounts for a higher proportion, increases sharply, thus leading to an increase in the total iron loss. When the average grain size D > 170 - (2Si% + Al%)×10 3 , the cold rolling deformation energy storage is small. During annealing, the unfavorable {111} texture does not preferentially nucleate and grow during recrystallization, resulting in deterioration of the finished product iron loss and an increase in the magnetostriction coefficient. On the other hand, when the Si and Al contents are relatively high, and the normalization temperature is relatively high or the soaking time is too long, the average grain size is too large, and the brittleness of the steel will increase sharply, and the cold rolling formability will be severely reduced. Therefore, the present invention defines that the average grain size D after normalization ≤ 170 - (2Si% + Al%)×10 3 .

[0032] The shear band formed during cold rolling is a concentrated deformation area caused by uneven deformation. It is a common recrystallization nucleation site, and Goss-oriented grains are mainly nucleated on the shear band during recrystallization annealing. Therefore, if the characteristics of the shear band can be effectively controlled, the development of the recrystallized Goss texture and cubic texture can be controlled, thereby effectively improving the magnetic properties of the product. The main factors affecting the formation of cold rolling shear bands include cold rolling strain rate, cold rolling reduction rate, etc., and the work roll diameter directly affects the cold rolling strain rate.

[0033] In the present invention, the cold rolling work roll diameter and the cold rolling reduction rate of each pass are comprehensively considered and summarized as the cold rolling parameter M. When M < 3.0, the shear band density is insufficient, the Goss-oriented grains and the cubic-oriented grains cannot grow fully after annealing, the average magnetostriction coefficient is too high, and the iron loss is too high. When M > 6.5, the shear band density is too high, {111} <112> , {1l1} <110> The unfavorable oriented grains nucleate in large quantities on the shear band, have size advantages after annealing, and swallow up nearby Goss oriented grains and cubic orientations, resulting in an excessively high average magnetostriction coefficient and excessively high iron loss. Therefore, the present invention controls M within the range of 3.0 to 6.5.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] Firstly, in view of the demand for improving the noise level of electric vehicle drive motors, the present invention, while considering the feasibility of non-oriented silicon steel production, controls the average grain size of the non-oriented silicon steel hot-rolled coil after normalization according to the content of Si and Al in the steel, and controls the cold rolling parameters by optimizing the cold rolling passes, the roller diameter and the entrance and exit thickness of each pass, thereby controlling the texture of the finished product while ensuring the cold rolling performance, thereby obtaining a low-loss, low-noise non-oriented silicon steel for electric vehicle drive motors.

[0036] Second, the average magnetostriction coefficient λp-p, average weighted sound level decibel value AWV and average iron loss of the low-noise non-oriented silicon steel for electric vehicle drive motor produced by the present invention are maintained at a relatively good level, the product thickness is in the range of 0.20mm to 0.30mm, and the average magnetostriction coefficient λp-p parallel to the rolling direction and perpendicular to the rolling direction at 400Hz and 1.0T is ≤10×10 -6 , average weighted sound level decibel value AWV (dBA) ≤ 100, average loss P 1.0 / 400 11~13.5W / kg.

[0037] Thirdly, the low-noise non-oriented silicon steel for the electric vehicle drive motor of the present invention avoids adding too many expensive alloy elements, has strong manufacturability and good production feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the orientation distribution function (ODF) diagram of the finished product plate in Example 1-1;

[0039] Figure 2 It is the orientation distribution function (ODF) diagram of the finished product plate in Example 1-4;

[0040] Figure 3 It is the orientation distribution function (ODF) diagram of the finished product plate in Comparative Example 1-2;

[0041] Figure 4 is Figures 1 to 3 The Euler space coordinate axes, the abscissa is The ordinate is Φ; Figures 1 to 3 is The sectional view of Specific implementation manners

[0042] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the present invention is not limited to the following embodiments only.

[0043] In the following embodiments, the production method of the low-noise non-oriented silicon steel for an electric vehicle drive motor includes the following steps:

[0044] 1) Molten steel smelting and continuous casting: The hot metal is pretreated for desulfurization and then enters the converter for smelting. After vacuum decarburization and alloying, molten steel with the target composition is obtained. In the molten steel, 2.5% ≤ Si% ≤ 4.0% and Al% ≤ 1.5%, 0.15% ≤ Mn% ≤ 1.0%; the molten steel enters the mold through the tundish for initial solidification and forming, and the slab with a liquid core is pulled out from the mold and enters the secondary cooling zone for continuous cooling and solidification until it is completely solidified to form a slab. Among them, during the continuous casting process, the drawing speed is controlled at 0.9 - 1.0 m / min, the superheat is 20 - 25 °C, and the cooling system of the continuous caster: the cooling water flow rate on the narrow side of the mold is 35 - 40 m 3 / h, the cooling water flow rate on the wide side of the mold is 340 - 350 m 3 / h, and the secondary cooling intensity is 2.2 - 2.5 L / kg.

[0045] 2) Heating and hot continuous rolling of the above slab: The above slab is heated and heat-insulated in a tunnel furnace and then enters a hot continuous rolling mill for hot continuous rolling and laminar cooling, and a hot rolled coil is obtained after coiling. Among them, the temperature of the slab entering the tunnel furnace is ≥ 600 °C, the soaking temperature is 1020 - 1120 °C, and the soaking time is 65 - 85 min; after the slab leaves the furnace, it enters a hot continuous rolling mill for hot continuous rolling. The finishing rolling temperature of the rough rolling is ≥ 950 °C, the thickness of the intermediate slab is 25 - 32 mm, the finishing rolling temperature of the finishing rolling is ≥ 860 °C, and the coiling temperature after laminar cooling is 550 °C - 630 °C.

[0046] 3) Normalize the above hot-rolled coil and then pickling it (using hydrochloric acid with a concentration of 9% - 10% in the acid tank) to obtain the pickled hot-rolled coil. Among them, the soaking section temperature of the normalizing furnace is 820 - 1050 °C, and the soaking time is 90 - 120 s. Further, when 2.5% ≤ Si% ≤ 3.0% and (Si + Al)% < 4.0%, 1000 °C < the soaking section temperature of the normalizing furnace ≤ 1050 °C; when 2.5% ≤ Si% ≤ 3.0% and 4.0% < (Si + Al)% ≤ 4.5%, 950 °C < the soaking section temperature of the normalizing furnace ≤ 1000 °C; when 3.0% < Si% ≤ 4.0% and (Si + Al)% < 4.2%, 880 °C < the soaking section temperature of the normalizing furnace ≤ 950 °C; when 3.0% < Si% ≤ 4.0% and 4.2% ≤ (Si + Al)% ≤ 5.5%, the soaking section temperature of the normalizing furnace is 820 - 880 °C.

[0047] The average grain size D after normalization satisfies: 160 - (3Si% + Al%) × 10 3 ≤ D ≤ 170 - (2Si% + Al%) × 10 3 ; where, the unit of D is μm, Si% is the weight percentage content of Si in the steel; Al% is the weight percentage content of Al in the steel;

[0048] 4) The above pickled hot-rolled coil is first heated by an induction heating furnace to ensure that the actual temperature of the steel coil at the entrance of the cold rolling mill reaches 80 - 150 °C, and then undergoes a single cold rolling to obtain a cold-rolled coil with a thickness of 0.20 - 0.30 mm. ; Among them, the value range of the cold rolling parameter M is 3.0 - 6.5, and the calculation formula of M is as follows:

[0049]

[0050] n is the number of rolling passes, H i is the entrance thickness of the i-th pass, H i+1 is the exit thickness of the i-th pass (i.e., the entrance thickness of the i + 1-th pass), and Ri is the work roll diameter.

[0051] 5) The above cold-rolled coil is degreased by electrolytic cleaning and then enters a continuous annealing furnace. The radiant tube heating and rising section is heated at a heating rate of 30 - 50 °C to 920 - 1020 °C and then enters the soaking section for homogenizing treatment, and then enters the gas protection circulation cooling section to be cooled at a speed of ≤ 10 °C to below 100 °C. Finally, a conventional phosphate coating is applied on a three-roll coater, and the coating thickness is generally 0.3 - 0.7 μm, and finally a low-noise non-oriented silicon steel for electric vehicle drive motors with a thickness in the range of 0.20 mm - 0.30 mm is obtained.

[0052] In the following embodiments, the target molten steel composition of the non-oriented electrical steel, by weight percentage, includes: Si 2.8% - 3.2%, Al 0.80% - 1.0%, Mn 0.30% - 0.55%, P < 0.035%, N < 0.002%, S < 0.0015%, Ti 0.0013% - 0.0016%, C 0.0016% - 0.0022%, Nb 0.0011% - 0.0015%, V 0.0012% - 0.0017%, Cu 0.02% - 0.03%, Cr 0.03% - 0.05%, and the balance is Fe and inevitable impurities.

[0053] Example 1

[0054] The molten steel of the non-oriented electrical steel is smelted and continuously cast into a slab. The composition of the slab, by weight percentage, is: Si 3.2%, Al 0.80%, Mn 0.30%, P 0.02%, N 0.0013%, S 0.0009%, Ti 0.0016%, C 0.0022%, Nb 0.0015%, V 0.0017%, Cu 0.03%, Cr 0.05%, and the balance is Fe and inevitable impurities; the temperature of the slab entering the tunnel furnace is 650°C, the soaking temperature is 1050°C, and the soaking time is 73 min. After the slab is taken out of the furnace, it enters the hot continuous rolling mill for hot continuous rolling. The finishing rolling temperature of the rough rolling is 970°C, the thickness of the intermediate slab is 29 mm, the finishing rolling temperature of the finish rolling is 880°C, the coiling temperature after laminar cooling is 580°C, and it is coiled into a hot rolled coil. The above hot rolled coil is normalized. The specific temperature and time of the soaking section of the normalizing furnace are shown in Table 1-1, and then pickled to obtain the pickled hot rolled coil. The pickled hot rolled coil is first heated by an induction heating furnace, and the actual temperature of the steel coil at the entrance of the rolling mill is 105°C, and then cold rolled once to obtain a cold rolled coil with a thickness of 0.30 mm. The cold rolled coil is degreased by electrolytic cleaning and then enters the continuous annealing furnace. In the radiant tube heating and rising section, it is heated at a heating rate of 35°C to 960°C and then enters the soaking section for soaking treatment, and then enters the gas protection circulation cooling section and is cooled at a rate of 7°C to 80°C. Finally, a phosphate coating is applied on a three-roll coater, and the coating thickness is 0.5 μm (the coating is extremely thin and can be ignored relative to the finished product thickness), and finally a finished product of non-oriented electrical steel sample is obtained, and the thickness of the finished product is about 0.30 mm.

[0055] The magnetostriction coefficient λp-p of the sample parallel and perpendicular to the rolling direction, the weighted sound level decibel value AWV, are measured on the MPG-200D magnetic testing system in accordance with IEC60404-17, and the iron loss P at 400 Hz and 1.0 T is measured using an Epstein square according to GB / T3655-2022. 1.0 / 400; The dimensions of the magnetostrictive coefficient test specimen are 600×100 mm, and the iron loss test specimen is a standard Epstein square specimen (half for the rolling direction and half for the direction perpendicular to the rolling direction), and the average value of the measured values in different directions is calculated. Table 1-1 shows the normalizing specific temperatures and soaking times of Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-4, as well as the average grain size after normalization and the cold rolling process; Table 1-2 shows the finished product properties of Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-4.

[0056] Table 1-1 Normalizing Process and Cold Rolling Process

[0057]

[0058]

[0059]

[0060] Table 1-2 Finished Product Properties of Examples and Comparative Examples

[0061]

[0062] As can be seen from Table 1-1 and Table 1-2, the average grain size after normalization and the cold rolling parameters of Examples 1-1 to 1-4 are all within the scope of the present invention, and the average magnetostrictive coefficient λp-p of the finished product ≤ 10×10 -6 , the average weighted sound level decibel value AWV (dBA) ≤ 100, and the average iron loss ≤ 13.5 W / kg, which have advantages in three aspects of magnetostrictive characteristics, low noise and iron loss level. In Comparative Example 1-1, due to the too small average grain size after normalization, the strength of the unfavorable γ texture in the corresponding annealed finished product is relatively high, and the too small average grain size results in relatively high average magnetostrictive coefficient λp-p, average weighted sound level decibel value AWV and average iron loss of the finished product. In Comparative Example 1-2, due to the too large average grain size after normalization, the strength of the unfavorable γ texture in the corresponding annealed finished product begins to increase. The too large average grain size of the finished product will lead to an increase in eddy current loss and relatively high average iron loss, and at the same time, the average magnetostrictive coefficient λp-p and the average weighted sound level decibel value AWV are also relatively high. In Comparative Example 1-3, the cold rolling parameter M < 3, the shear band density is insufficient, and the Goss-oriented grains and cube-oriented grains cannot grow fully after annealing, resulting in too high average magnetostrictive coefficient λp-p, average weighted sound level decibel value AWV and average iron loss of the finished product. In Comparative Example 1-4, the cold rolling parameter M > 6.5, the size of the unfavorable-oriented grains is relatively large after annealing, and the average magnetostrictive coefficient λp-p, average weighted sound level decibel value AWV and average iron loss of the finished product are also very high.

[0063] From Figures 1 to 3It can be seen that the unfavorable γ - orientation texture in Example 1 - 1 is relatively weak; the favorable λ - texture in Example 1 - 4 is relatively strong, and the unfavorable γ - orientation texture is relatively weak; the unfavorable γ - orientation texture in Comparative Example 1 - 2 is relatively strong. The γ - orientation grains represented by {111}<112> and {111}<110> have an advantage in size. During the magnetization process, they hinder the movement of magnetic domains, resulting in an increase in the applied magnetic field, higher energy consumption for magnetic domain movement, an increase in iron loss, an increase in the magnetostriction coefficient, and an increase in noise. While the λ - texture contains more easy - magnetization crystal directions, and with the same applied magnetic field, the magnetic domains are easier to move, resulting in a decrease in iron loss, a decrease in the magnetostriction coefficient, and a decrease in noise.

[0064] Example 2

[0065] The non - oriented silicon steel molten steel is smelted and continuously cast into a slab. The composition of the slab is by weight percentage: Si 2.8%, Al 1.0%, Mn 0.55%, P 0.03%, N 0.0015%, S 0.0011%, Ti 0.0013%, C 0.0016%, Nb 0.0011%, V 0.0012%, Cu 0.02%, Cr 0.03%, and the rest is Fe and inevitable impurities. The temperature of the slab entering the tunnel furnace is 665°C, the soaking temperature is 1020°C, and the soaking time is 79 min. After the slab is taken out of the furnace, it enters the hot continuous rolling mill for hot continuous rolling. The rough rolling final rolling temperature is 980°C, the thickness of the intermediate slab is 32 mm, the finish rolling final rolling temperature is 890°C, and the coiling temperature after laminar cooling is 590°C, and it is coiled into a hot - rolled coil. The above - mentioned hot - rolled coil is normalized. The specific temperature and time in the soaking section of the normalizing furnace are shown in Table 2 - 1, and then pickled to obtain the pickled hot - rolled coil. This pickled hot - rolled coil is first heated by an induction heating furnace, and the actual temperature of the steel coil at the mill inlet is 115°C, and then subjected to one - pass cold rolling to obtain a cold - rolled coil with a thickness of 0.25 mm. This cold - rolled coil is electrolytically cleaned and degreased and then enters the continuous annealing furnace. In the radiant tube heating and heating - up section, it is heated at a heating rate of 33°C to 980°C and then enters the soaking section for soaking treatment, and then enters the gas - protected circulation cooling section and is cooled at a rate of 5°C to 90°C. Finally, a phosphate coating is applied on a three - roll coater, and the coating thickness is about 0.4 μm, and finally a non - oriented silicon steel specimen product is obtained, and the thickness of the product is about 0.25 mm.

[0066] Table 2 - 1 shows the normalizing process and cold rolling process of Examples 2 - 1 to 2 - 4 and Comparative Examples 2 - 1 to 2 - 4; according to the method of Example 1, the performance of the finished product is tested, and Table 2 - 2 shows the performance of the finished products of Examples 2 - 1 to 2 - 4 and Comparative Examples 2 - 1 to 2 - 4.

[0067] Table 2 - 1 Normalizing Process and Cold Rolling Process

[0068]

[0069]

[0070] Table 2-2 Product Performance of Examples and Comparative Examples

[0071]

[0072]

[0073] As can be seen from Table 2-1 and Table 2-2, the average grain size after normalization and the cold rolling parameters of Examples 2-1 to 2-4 are all within the scope of the invention, and the average magnetostriction coefficient λp-p (≤10×10 -6 ), the average weighted sound level in decibels AWV (≤92), and the average iron loss (P 1.0 / 400 ≤12.0 W / kg) of the products are all maintained at a relatively good low level. In Comparative Example 2-1, since the average grain size after normalization is too small, the strength of the unfavorable γ texture in the corresponding annealed product is relatively high, and the average grain size is too small, resulting in a relatively high average magnetostriction coefficient λp-p and average weighted sound level in decibels AWV of the product, and the average iron loss is also relatively high. In Comparative Example 2-2, since the average grain size after normalization is too large, the brittleness of the steel will increase sharply, and the strip breaks during the first pass of rolling, and no product is produced. In Comparative Example 1-3, the cold rolling parameter M < 3, and the density of shear bands is insufficient. The Goss-oriented grains and cube-oriented grains cannot grow sufficiently after annealing, resulting in too high average magnetostriction coefficient λp-p, average weighted sound level in decibels AWV, and average iron loss of the product. In Comparative Example 1-4, the cold rolling parameter M > 6.5, and the size of the unfavorably oriented grains is relatively large after annealing, and the average magnetostriction coefficient λp-p, average weighted sound level in decibels AWV, and average iron loss of the product are also very high.

[0074] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several improvements and transformations can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for producing low-noise non-oriented silicon steel for electric vehicle drive motors, characterized in that: The steps include: 1) Desulfurization of molten iron, smelting in a converter, obtaining molten steel with target composition, and continuous casting into billets; 2) The ingot is heated and kept warm in the tunnel furnace, and then enters the hot rolling unit for hot rolling to obtain hot rolled coils; 3) normalizing and pickling the hot-rolled coil to obtain a pickled hot-rolled coil; wherein the average grain size D of the hot-rolled coil after normalization satisfies: <h2 style=";text-align:left;direction:ltr">160-(3Si%+Al%)×10<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> ≤D≤170-(2Si%+Al%)×10<h2 style=";text-align:left;direction:ltr"> 3 Wherein, the unit of D is μm, Si% is the weight percentage content of Si in steel; Al% is the weight percentage content of Al in steel; 4) cold rolling the pickled hot-rolled coil, controlling the cold rolling parameters according to the cold rolling passes, the roll diameter and the inlet and outlet thickness of each pass, to obtain a cold-rolled coil; 5) The cold rolled coil is annealed and coated to obtain low-noise non-oriented silicon steel for electric vehicle drive motors.

2. The method for producing low-noise non-oriented silicon steel for electric vehicle drive motor according to claim 1, characterized in that: In step 1), the composition of the molten steel meets the requirements of 2.5%≤Si%≤4.0% and Al%≤1.5%, 0.15%≤Mn%≤1.0% by weight; in step 3), the hot-rolled steel coil enters a normalizing furnace for normalization, the temperature of the normalizing furnace's soaking section is 820-1050°C, and the soaking section time is 90-120s.

3. The method for producing low-noise non-oriented silicon steel for electric vehicle drive motor according to claim 2, characterized in that: When 2.5%≤Si%≤3.0% and (Si+Al)%<4.0%, the temperature of the soaking section of the normalizing furnace is greater than 1000℃ and does not exceed 1050℃; When 2.5%≤Si%≤3.0% and 4.0%≤(Si+Al)%≤4.5%, the temperature of the soaking section of the normalizing furnace is greater than 950°C and does not exceed 1000°C; When 3.0%<Si%≤4.0% and (Si+Al)%<4.2%, the temperature of the soaking section of the normalizing furnace is greater than 880℃ and does not exceed 950℃; When 3.0%<Si%≤4.0% and 4.2%≤(Si+Al)%≤5.5%, the temperature of the soaking section of the normalizing furnace is 820-880°C.

4. The method for producing low-noise non-oriented silicon steel for electric vehicle drive motor according to claim 1, characterized in that: In step 1), the molten steel enters the crystallizer for initial solidification to obtain a casting with a liquid core, and then is pulled out of the crystallizer and enters the secondary cooling zone for further cooling and solidification until it is completely solidified to form a casting; wherein the cooling system of the continuous casting machine is: the cooling water flow rate of the narrow side of the crystallizer is 25-45m 3 / h, cooling water flow rate of the wide side of the crystallizer 290~370m 3 / h, secondary cooling intensity 1.8~3.2L / kg.

5. The method for producing low-noise non-oriented silicon steel for electric vehicle drive motor according to claim 4, characterized in that: During the continuous casting process, the pulling speed is controlled at 0.7-1.1 m / min and the superheat is controlled at 10-30°C.

6. The method for producing low-noise non-oriented silicon steel for electric vehicle drive motor according to claim 1, characterized in that: In step 2), the temperature of the ingot entering the tunnel furnace is ≥400°C, the soaking temperature is 1000-1150°C, and the soaking time is 60-90min; after the ingot is taken out of the furnace, it enters the hot rolling unit for hot rolling, the rough rolling and final rolling temperature is ≥940°C, the intermediate billet thickness is 25-35mm, and the finishing rolling temperature is ≥840°C.

7. The method for producing low-noise non-oriented silicon steel for electric vehicle drive motor according to claim 1, characterized in that: In step 4), the pickled hot rolled coil is heated by an induction heating furnace to ensure that the actual coil temperature at the entrance of the cold rolling mill reaches 80-150° C.; the cold rolling parameter M ranges from 3.0 to 6.5, and the calculation formula of M is as follows: In the above formula, n is the rolling pass, H i is the entrance thickness of the i-th pass, H i+1 is the exit thickness of the i-th pass (i.e. the entrance thickness of the i+1-th pass), Ri is the diameter of the working roll; in this formula, H i , H i+1 The same length unit is used as Ri.

8. The method for producing low-noise non-oriented silicon steel for electric vehicle drive motor according to claim 1, characterized in that: In step 5), a continuous annealing furnace is used, and the radiation tube heating section is heated to 900-1050°C at a heating rate of 30-60°C, then enters the insulation section for heat treatment, and then enters the gas protection circulation cooling section to cool to below 100°C at a rate of ≤15°C.

9. The method for producing low-noise non-oriented silicon steel for electric vehicle drive motor according to claim 1, characterized in that: The coating adopts conventional phosphate coating, and the coating thickness is controlled at 0.3-0.7 μm; the thickness of the low-noise non-oriented silicon steel for the electric vehicle driving motor is in the range of 0.2 mm-0.3 mm.

10. Low-noise non-oriented silicon steel for electric vehicle drive motor produced by the method of any one of claims 1 to 9, characterized in that: The product thickness is in the range of 0.20mm to 0.30mm, and its performance indicators are as follows: 400Hz, 1.0T, the average magnetostriction coefficient parallel to the rolling direction and perpendicular to the rolling direction λp-p≤10×10 -6 , average weighted sound level decibel value AWV (dBA) ≤ 100, average loss P 1.0 / 400 11~13.5W / kg.

Images