A low-magnetostriction ultra-thin electrical steel and a production method thereof

Abstract

The application discloses a low-magnetostrictive ultrathin electrical steel and a production method thereof, and belongs to the technical field of metallurgy. The low-magnetostrictive ultrathin electrical steel prepared by the application has the following chemical components: C is less than or equal to 0.0020%, Si is 2.8%-3.8%, Mn is 0.20%-1.0%, P is 0.005%-0.05%, S is less than or equal to 0.0010%, N is less than or equal to 0.0015%, Ti is less than or equal to 0.0015%, V is less than or equal to 0.0020%, Nb is less than or equal to 0.0020%, Al is 0.20%-0.80%, RE is 0.0005%-0.0050%, and the rest is iron (Fe) and inevitable impurity elements. The application adjusts and optimizes the components by introducing RE, purifies the molten steel from the component end, forms dispersed RE compounds, and inhibits harmful texture of hot rolling; in combination with a secondary cold rolling strategy, the strain accumulation gradient and the texture gradient are actively compensated, the problem of magnetic domain oscillation of the ultrathin specification is broken through, and thus the strict requirement of low magnetostriction of low-altitude aircraft driving motors and other high-end motors is met.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a low magnetostrictive ultrathin electrical steel and its production method. Background Technology

[0002] The performance requirements for electrical steel in low-altitude aircraft (such as eVTOL and drones) are concentrated on three core indicators: low iron loss, high magnetic induction, and low noise. These requirements are directly related to the energy efficiency, power output quality, and environmental adaptability of the aircraft.

[0003] Low iron loss directly reduces motor energy loss, extends aircraft endurance, and reduces the burden on the cooling system. Low-altitude aircraft motors require frequent start-stop and speed changes (such as during vertical takeoff and landing), resulting in high operating frequencies. Traditional electrical steel experiences significantly increased eddy current and magnetostrictive losses at high frequencies, leading to decreased motor efficiency and excessive temperature rise. By using ultra-thin silicon steel sheets with a uniform insulation layer, eddy current paths are reduced; simultaneously, increasing the silicon (Si) and aluminum (Als) content and controlling the hot-rolling coiling temperature reduces high-frequency losses by 20%.

[0004] High magnetic induction motors enable miniaturization and weight reduction to meet the payload and space constraints of aircraft. Low-altitude aircraft have stringent requirements for motor power density. High magnetic induction can generate a stronger magnetic field within the same volume, increasing output torque. This requires optimizing material texture, suppressing unfavorable textures, and improving the purity of molten steel.

[0005] Aircraft have extremely high requirements for noise control, directly affecting passenger comfort and environmental compatibility. The noise mainly originates from vibrations caused by the magnetostriction of the iron core. Material innovation is needed to reduce the magnetostriction effect by adjusting the composition and process.

[0006] While existing technologies CN120099388A and CN120193196A have achieved the production of 0.20~0.30mm low-noise non-oriented silicon steel, they still have significant shortcomings: ① Composition control is limited to traditional elements such as Si, Al, Sn, and Sb, and performance is optimized only by coarsening grains or suppressing {111} texture, without addressing the precise matching between steel purity and microstructure. Residual stress and texture gradient are still difficult to eliminate; ② The process relies on adjustments to parameters such as cold rolling passes and roll diameter, and the uniformity of texture in the thickness direction is not quantitatively controlled. When ultra-thin (≤0.20mm), the problems of plate shape and magnetic domain oscillation become prominent; ③ The magnetostriction coefficient is only ≤10×10 -6 It does not meet the requirements for ultimate noise reduction, with an average weighted sound level (AWV) of ≤100 dBA, which is insufficient to meet the needs of low-altitude aircraft and other scenarios.

[0007] In summary, electrical steel for low-altitude aircraft needs to achieve breakthroughs in comprehensive performance through material composition optimization, thin-gauge design, and technological innovation, with the goals of low iron loss to ensure energy efficiency, high magnetic induction to support dynamic density, and low noise to improve environmental friendliness. These requirements are driving the evolution of electrical steel towards high-frequency, low-loss, high magnetic permeability, and low vibration and noise. Therefore, developing a low-magnetostriction, ultra-thin electrical steel for application in low-altitude aircraft and other high-end motor fields has become one of the most important issues that urgently needs to be addressed. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention introduces RE for composition adjustment and optimization, purifies the molten steel from the composition end and forms dispersed RE compounds, suppressing harmful textures from hot rolling; combined with a secondary cold rolling strategy, it actively compensates for strain accumulation gradient and texture gradient, overcoming the problem of magnetic domain oscillation in ultra-thin specifications, thereby meeting the stringent requirements of low magnetostriction for low-altitude aircraft drive motors and other high-end motors.

[0009] In view of this, the present invention provides a low magnetostriction ultrathin electrical steel and its production method, which achieves efficient preparation of low magnetostriction ultrathin electrical steel through synergistic optimization of smelting composition and the entire process.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] Firstly, this invention provides a low magnetostrictive ultrathin electrical steel, the material composition of which follows the principle of "high silicon, low aluminum, low impurities, and trace amounts of RE". The chemical composition of the low magnetostrictive ultrathin electrical steel is (wt%): C≤0.0020%, Si: 2.8%~3.8%, Mn: 0.20%~1.0%, P: 0.005%~0.05%, S≤0.0010%, N≤0.0015%, Ti≤0.0015%, V≤0.0020%, Nb≤0.0020%, Als: 0.20%~0.80%, RE: 0.0005%~0.0050%, with the remainder being iron (Fe) and unavoidable impurity elements.

[0012] The chemical composition of this invention, by weight percentage, is as follows: Carbon (C), Nitrogen (N), Titanium (Ti), Vanadium (V), and Niobium (Nb) contents are extremely low, controlled at ≤0.0020%, to avoid increased aging due to excessive carbon content. Silicon (Si) content is 2.8%~3.8%, which improves resistivity, reduces eddy current losses, and optimizes electromagnetic properties. Manganese (Mn) content is 0.20%~1.0%, mainly used to improve electromagnetic properties and machinability. Phosphorus (P) content is controlled at 0.005%~0.05% to avoid adverse effects on the toughness and weldability of the steel. Sulfur (S) content is strictly controlled at ≤0.0010% to reduce sulfide inclusions and improve the purity and electromagnetic properties of the steel. Aluminum (Als) content is 0.20%~0.80%, as aluminum improves electromagnetic properties. RE is precisely added at a mass percentage of 0.0005%~0.0050%, purifying the molten steel from the composition stage and forming dispersed RE compounds to inhibit harmful textures in hot rolling.

[0013] Secondly, the present invention provides a method for producing the above-mentioned low magnetostrictive ultrathin electrical steel, comprising the following steps: converter smelting, continuous casting, hot rolling, normalizing, cold rolling and finished product annealing; The cold rolling process is a two-stage cold rolling method with a total reduction rate of 88% to 94%, an intermediate annealing temperature of 880 to 920°C, and an annealing time of 65 to 95 seconds. The aforementioned two-stage cold rolling method breaks through the traditional single-stage cold rolling mode and adopts dynamic reduction ratio allocation: The first pass has a reduction rate of 50% to 75%, forming a high-strength deformation texture. The second pass has a reduction rate of 40%~80% to compensate for the strain gradient and texture gradient in the thickness direction; Its core objective is to actively compensate for the cumulative strain gradient in the thickness direction caused by material work hardening and changes in friction conditions. The texture state from the subsurface layer to the quarter layer changes from a strong γ texture to a weaker γ and α' texture, thereby ensuring a high degree of consistency in texture and performance across the entire thickness of the finished plate. Furthermore, the carbon content at the end of the converter smelting process is controlled below 0.03% to ensure smooth subsequent decarburization; slag-blocking tapping technology is employed during the steel tapping process to reduce the source of non-metallic inclusions in the steel.

[0014] Furthermore, the continuous casting adopts low superheat casting, and the electromagnetic stirring working current is 340~400A to reduce component segregation, and the proportion of equiaxed crystals in the billet is ≥65%.

[0015] Furthermore, the hot rolling furnace has the following characteristics: heating temperature: 1150~1250℃; holding time: 180~220min; furnace exit temperature: 1100~1150℃; final rolling temperature: 880~920℃; coiling temperature: 660~720℃; and hot-rolled plate thickness: 1.6~2.0mm.

[0016] Furthermore, in the normalizing step, the normalizing temperature is 850~1050℃; the process speed is 35~70m / min, which needs to be adjusted according to the normalizing temperature and material thickness to ensure sufficient homogenization of the microstructure; the atmosphere is a N2-H2 mixed atmosphere, in which the H2 content is 15%~40%; the reducing atmosphere can prevent surface oxidation and ensure surface quality; the grain size is controlled at 60~90 micrometers, and the relatively uniform grain size creates conditions for introducing more uniform energy storage in subsequent cold rolling.

[0017] Furthermore, the finished product annealing adopts segmented annealing, with a homogenization temperature of 850~950℃ and a homogenization time of 40~60s. The hydrogen dew point is controlled at -15~-25℃ to promote the dispersion and precipitation of RE and optimize the recrystallization texture composition. The cooling rate after annealing is 20~35℃ / s, and micro-tension control in the furnace is adopted, with tension ≤0.8KN to reduce the residual stress of the finished strip steel. The grain size is controlled at 100±20μm.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves the production of ultra-thin, low-magnetostrictive materials with a thickness of 0.10~0.20mm through RE micro-alloying, high purity control, and full-process process control. The magnetostriction coefficient of the product (λp-p≤8.2×10) -6 ) and iron loss (P 1.0 / 400 ≤9+45t 2 The W / kg) was significantly optimized, and the average weighted sound level in decibels (AWV) was ≤90.

[0019] 2. It systematically transcends the limitations of existing technologies, providing high-performance and high-reliability material solutions for the manufacturing of miniaturized, high-power-density motors in high-end application fields such as low-altitude aircraft and aerospace, promoting the green transformation of high-end equipment manufacturing industry, and has broad application prospects and significant economic benefits. Detailed Implementation

[0020] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0021] Example 1 A low magnetostrictive ultrathin electrical steel, with the following chemical composition by mass: Carbon (C): 0.0015%, Silicon (Si): 3.42%, Manganese (Mn): 0.51%, Phosphorus (P): 0.009%, Sulfur (S): 0.0008%, Nitrogen (N): 0.0015%, Titanium (Ti): 0.0015%, Niobium (Nb): 0.0018%, Vanadium (V): 0.0019%, Aluminum (Als): 0.72%, Re: 0.0032%, with the remainder being Iron (Fe) and unavoidable impurity elements.

[0022] The production process of the aforementioned low magnetostrictive ultrathin electrical steel includes the following steps: a) Converter smelting The final carbon content is strictly controlled below 0.03% to ensure the smooth progress of subsequent decarburization. Slag-blocking tapping technology is employed during the tapping process to reduce the source of non-metallic inclusions in the steel.

[0023] b) Continuous casting The continuous casting process is adopted, with an electromagnetic stirring current of 350A and an equiaxed crystal ratio of 65% for the billet. A slag baffle is used during tapping to control the slag thickness in the ladle to 88mm.

[0024] c) Hot-rolled Heating furnace temperature: 1170℃, holding time: 185min; furnace exit temperature: 1110℃; final rolling temperature: 885℃; coiling temperature: 690℃.

[0025] d) Normalization Normalizing temperature: 920℃, speed: 55m / min, atmosphere: N2-16%H2, grain size after normalizing: 75μm.

[0026] e) Cold rolling The material is cold rolled in two stages. The raw material is 1.8 mm thick. It is cold rolled to the target thickness of 0.50 mm in one stage, with an intermediate annealing temperature of 920℃ and an annealing time of 70 s. It is then cold rolled to the target thickness of 0.15 mm in two stages, with a total reduction rate of 91.6%.

[0027] f) Finished product annealing Two-stage annealing was employed: the soaking temperature was 930℃, and the soaking time was 60s. The cooling rate after annealing was 25℃ / s, the furnace tension was 0.6kN, the dew point of the furnace atmosphere was strictly monitored and maintained at -23℃, and the grain size was controlled at 105μm.

[0028] The low magnetostrictive ultrathin electrical steel prepared in this embodiment has a specification of 0.15mm, and its product performance is shown in Table 1.

[0029] Table 10.15mm Specification Product Performance

[0030] Example 2 A low magnetostrictive ultrathin electrical steel, with the following chemical composition by mass: Carbon (C): 0.0019%, Silicon (Si): 3.28%, Manganese (Mn): 0.43%, Phosphorus (P): 0.006%, Sulfur (S): 0.0007%, Nitrogen (N): 0.0012%, Titanium (Ti): 0.0011%, Niobium (Nb): 0.0016%, Vanadium (V): 0.0020%, Aluminum (Als): 0.64%, Lanthanum (La) and Cerium (Ce) mixture: 0.0030%, the remainder being Iron (Fe) and unavoidable impurity elements.

[0031] The production process of the aforementioned low magnetostrictive ultrathin electrical steel includes the following steps: a) Converter smelting The final carbon content is strictly controlled below 0.03% to ensure the smooth progress of subsequent decarburization. Slag-blocking tapping technology is employed during the tapping process to reduce the source of non-metallic inclusions in the steel.

[0032] b) Continuous casting The continuous casting process is adopted, with an electromagnetic stirring current of 340A and an equiaxed crystal ratio of 70% for the billet. A slag baffle is used during tapping to control the slag thickness in the ladle to reach 90mm.

[0033] c) Hot-rolled Heat soaking temperature: 1180℃; holding time: 190min; furnace exit temperature: 1115℃; final rolling temperature: 900℃; coiling temperature: 690℃.

[0034] d) Normalization Normalizing temperature: 920℃, speed: 50m / min, atmosphere: N2-16%H2, grain size after normalizing: 85μm.

[0035] e) Cold rolling The material is cold rolled in two stages. The raw material is 1.6 mm thick. It is cold rolled to the target thickness of 0.45 mm in one stage, with an intermediate annealing temperature of 900℃ and an annealing time of 95 s. It is then cold rolled to the target thickness of 0.10 mm in two stages, with a total reduction rate of 93.75%.

[0036] f) Finished product annealing Two-stage annealing was employed: the soaking temperature was 950℃, and the soaking time was 45s. The cooling rate after annealing was 20℃ / s, and the furnace tension was 0.5kN. The dew point of the furnace atmosphere was strictly monitored and maintained at -21℃, and the grain size was controlled at 99μm.

[0037] The low magnetostrictive ultrathin electrical steel prepared in this embodiment has a specification of 0.10 mm, and its product performance is shown in Table 2.

[0038] Table 20.10mm Specification Product Performance

[0039] Example 3 A low magnetostrictive ultrathin electrical steel, with the following chemical composition by mass: Carbon (C): 0.0015%, Silicon (Si): 3.6%, Manganese (Mn): 0.49%, Phosphorus (P): 0.008%, Sulfur (S): 0.001%, Nitrogen (N): 0.0015%, Titanium (Ti): 0.0012%, Niobium (Nb): 0.0015%, Vanadium (V): 0.0017%, Aluminum (Als): 0.73%, Cerium (Ce): 0.0021%, with the remainder being Iron (Fe) and unavoidable impurity elements.

[0040] The production process of the aforementioned low magnetostrictive ultrathin electrical steel includes the following steps: a) Converter smelting The final carbon content is strictly controlled below 0.03% to ensure the smooth progress of subsequent decarburization. Slag-blocking tapping technology is employed during the tapping process to reduce the source of non-metallic inclusions in the steel.

[0041] b) Continuous casting During continuous casting, the electromagnetic stirring current is 350A, the equiaxed crystal ratio of the billet is 66%, and the liquid level fluctuation in the crystallizer is controlled within ±3mm. A slag baffle is used during tapping to control the slag thickness in the ladle to 87mm.

[0042] c) Hot-rolled Heat soaking temperature: 1210℃; holding time: 220min; furnace exit temperature: 1110℃; final rolling temperature: 910℃; coiling temperature: 705℃.

[0043] d) Normalization Normalizing temperature: 890℃, speed: 55m / min, atmosphere: N2-16%H2, grain size after normalizing: 69μm.

[0044] e) Cold rolling The material is cold rolled in two stages. The raw material is 1.9 mm thick. It is cold rolled to the target thickness of 0.50 mm in one stage, with an intermediate annealing temperature of 920℃ and an annealing time of 95 s. It is then cold rolled to the target thickness of 0.20 mm in two stages, with a total reduction rate of 89.47%.

[0045] f) Finished product annealing Two-stage annealing was employed: a soaking temperature of 950℃ and a soaking time of 60s. The cooling rate after annealing was 25℃ / s, and the furnace tension was 0.8kN. The dew point of the furnace atmosphere was strictly monitored and maintained at -20℃, and the grain size was controlled at 110μm.

[0046] The low magnetostriction ultrathin electrical steel prepared in this embodiment has a specification of 0.20 mm, and its product performance is shown in Table 3.

[0047] Table 30.20mm Specification Product Performance

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low magnetostrictive ultrathin electrical steel, characterized in that, The chemical composition of the ultra-thin electrical steel is as follows (mass fraction): C ≤ 0.0020%, Si: 2.8%~3.8%, Mn: 0.20%~1.0%, P: 0.005%~0.05%, S ≤ 0.0010%, N ≤ 0.0015%, Ti ≤ 0.0015%, V ≤ 0.0020%, Nb ≤ 0.0020%, Als: 0.20%~0.80%, RE: 0.0005%~0.0050%, with the remainder being Fe and unavoidable impurity elements.

2. A method for producing the low magnetostrictive ultrathin electrical steel according to claim 1, characterized in that, Includes the following steps: Converter smelting, continuous casting, hot rolling, normalizing, cold rolling and finished product annealing; The cold rolling process is a two-stage cold rolling process with a total reduction rate of 88% to 94%, a first-pass reduction rate of 50% to 75%, a second-pass reduction rate of 40% to 80%, an intermediate annealing temperature of 880 to 920°C, and an annealing time of 65 to 95 seconds.

3. The production method according to claim 2, characterized in that, The carbon content at the end of the converter smelting process is controlled below 0.03%, and the tapping process adopts slag-blocking tapping technology.

4. The production method according to claim 2, characterized in that, In the continuous casting step, the electromagnetic stirring current is 340~400A, and the equiaxed crystal ratio of the billet is ≥65%.

5. The production method according to claim 2, characterized in that, The hot rolling process involves the following steps: heating furnace soaking temperature: 1150~1250℃; holding time: 180~220min; furnace exit temperature: 1100~1150℃; final rolling temperature: 880~920℃; coiling temperature: 660~720℃; and hot-rolled plate thickness: 1.6~2.0mm.

6. The production method according to claim 2, characterized in that, The finished product is annealed in stages, with a homogenization temperature of 850~950℃, a homogenization time of 40~60s, a hydrogen dew point controlled at -15~-25℃, and a cooling rate of 20~35℃ / s after annealing; the grain size is controlled at 100±20μm.

7. The production method according to claim 2, characterized in that, The furnace tension during the finished product annealing step is ≤0.8KN.

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