A method for preparing a low cobalt soft magnetic alloy strip

Abstract

This application discloses a method (100) for preparing low-cobalt soft magnetic alloy strip, comprising: weighing raw materials (S102), which, by weight percentage, include: 3wt%-12wt% Co, 0.2wt%-0.8wt% Cr, 0.6wt%-2.5wt% Si, 0.03wt%-0.06wt% Nb, 0.2wt%-0.8wt% Mn, 0.01wt%-0.05wt% C, with the balance being Fe and unavoidable impurities; melting and casting the raw materials into an ingot to form a billet (S104); removing the oxide scale from the billet (S106); and further processing the raw materials. The billet after removing the oxide scale is heated (S108); the heated billet is rolled into a strip (S110); the strip is water-quenched and solution-treated to form a finished strip (S112); the finished strip is cold-rolled at least once until a set first thickness is reached (S114), wherein the total deformation is controlled at 50-65%; softening annealing is performed (S116); the finished strip of the first thickness is cold-rolled at least once again (S118) until a set second thickness is reached; the finished strip of the second thickness is heat-treated and annealed (S120) to obtain a set hardness value.

Description

Technical Field

[0001] This application relates to a method specifically for manufacturing soft magnetic alloy strips, and more particularly to a method for preparing high-performance low-cobalt soft magnetic alloy strips. Background Technology

[0002] Typically, motors for eVTOL (electric vertical takeoff and landing aircraft) and robot joint motors use inexpensive silicon steel sheets to make the motor stator core. However, although silicon steel sheets are inexpensive, their saturation magnetic induction intensity is only 1.65T, and they have high high-frequency losses. Motors with the same power are large in size and heavy, and are only suitable for applications where motor performance requirements are not high.

[0003] With the rapid development of eVTOL and robotics technologies, unprecedented performance requirements have been placed on soft magnetic materials. These emerging industries not only require materials to possess traditional characteristics of high permeability and low coercivity, but also set stringent standards in terms of power density, environmental adaptability, and lightweighting.

[0004] First, the eVTOL motor needs to simultaneously meet the high torque requirements of vertical takeoff and landing and the high power requirements of cruise. Specifically, the motor power density needs to reach 5-8 kW / kg, and the torque density needs to exceed 15 N·m / kg. This dynamic switching capability of "high power - high torque" requires soft magnetic materials to maintain stable performance over a wide speed range to avoid flight attitude instability caused by speed fluctuations. Aerospace-grade motors need to operate stably in a wide temperature range of -40℃ to 125℃, which requires soft magnetic materials to have excellent thermal stability and mechanical strength. At the same time, to increase the payload, the weight of the eVTOL motor needs to be reduced by 20-30%, which has driven the development of soft magnetic materials with high saturation magnetic induction (Bs). CoFe alloys can increase the motor power density by 20-30%.

[0005] Similarly, the widespread adoption of humanoid robots has placed revolutionary demands on joint servo motors, whose performance directly determines the robot's motion accuracy and response speed. Modern humanoid robot joint modules need to be 50% lighter and have response speeds improved to the millisecond level. This requires soft magnetic materials that maintain high permeability (μ... i While achieving a perfect balance between high saturation magnetic induction intensity and low coercivity (≥8000 H / m), it also achieves a perfect balance between high saturation magnetic induction intensity and low coercivity.

[0006] Traditional cobalt-based soft magnetic alloys (such as 1J22) occupy an important position in high-end fields due to their excellent magnetic properties. The 1J22 alloy has a cobalt (Co) content as high as approximately 50%. Among existing soft magnetic materials, the 1J22 iron-cobalt-vanadium soft magnetic alloy, as defined in national standards, has the highest saturation magnetic induction (Bs) (2.4T) and a very high Curie point (980℃). Due to its high saturation magnetic induction, the size of motors of the same power can be significantly reduced, and when manufacturing electromagnets, a large attraction force can be generated within the same cross-sectional area. The high Curie point allows the alloy to operate at relatively high temperatures, where other soft magnetic materials have already been completely demagnetized, while maintaining good magnetic stability. Therefore, 1J22's excellent magnetic properties make it indispensable in high-end fields such as aerospace and advanced medical equipment, where extremely high magnetic performance is required. However, the cobalt content of 1J22 alloy is as high as about 50%. Due to the scarcity of cobalt resources and the poor processing performance of high cobalt alloys, the cost of 1J22 cobalt-based alloy remains high, which means it can only be used in high-end aerospace fields. It cannot be used in the civilian market due to cost constraints. This has prompted the industry to accelerate the search for a high-performance low-cobalt soft magnetic alloy solution to replace it.

[0007] The national standard includes a 27% cobalt iron-cobalt alloy called 1J27, whose magnetic induction intensity is slightly lower than that of 1J22. It is used in less demanding applications such as motors, mobile phone antennas, and relays. However, although its 27% cobalt content significantly reduces its cost compared to 1J22, it is still too high for civilian markets such as drones.

[0008] In recent years, research on iron-cobalt alloys has focused on improving the mechanical strength of 1J22. For example, patent CN114717460A discloses a high-strength iron-cobalt soft magnetic alloy strip and its preparation method. The chemical composition of the iron-cobalt soft magnetic alloy strip, by weight percentage, is: Co 47.5%–51.0%, V 0.5%–2.0%, Nb 0.03%–0.5%, Si < 0.3%, Mn < 0.3%, C ≤ 0.03%, P < 0.015%, S < 0.015%, with the balance being Fe. Patent CN120575101A relates to a high-strength FeCo-V-Nb soft magnetic alloy and its heat treatment method. The chemical composition, by weight percentage, is: Fe: 40%–60%; Co: 40%–60%; V: 1%–3%; Nb: 0.01%–1%. After smelting, casting, hot rolling, and cold rolling, a thin strip with a thickness of 0.25-0.45 mm is finally obtained. This invention addresses the problem that existing iron-cobalt soft magnetic alloys cannot simultaneously achieve high magnetic and mechanical properties, significantly improving both the mechanical and magnetic properties of iron-cobalt soft magnetic alloys under both room temperature and high temperature conditions. However, the Co content remains very high, making it more expensive than 1J22.

[0009] Therefore, although existing iron-cobalt alloys have high magnetic induction intensity and mechanical strength, their high cobalt content leads to high cost and price, making them unsuitable for the rapidly developing high-performance drones and the core requirements of motors for robots in the field of artificial intelligence. There is an urgent need to develop an alloy material with low cobalt content, high saturation magnetic induction intensity, and low cost to meet the needs of new fields. Summary of the Invention

[0010] This application provides a low-cost, low-cobalt soft magnetic alloy and a method for preparing its core. While maintaining high saturation magnetic induction and low coercivity, it reduces the cobalt content, thereby lowering the price of the high-performance iron-cobalt soft magnetic alloy, which can meet the development needs of high-end drones and robots.

[0011] According to a first aspect of the present invention, a method for preparing a low-cobalt soft magnetic alloy strip is provided.

[0012] This method includes the following operations:

[0013] • Weigh the raw materials, by weight percentage, wherein the raw materials include: 3wt%-12wt% Co, 0.2wt%-0.8wt% Cr, 0.6wt%-2.5wt% Si, 0.03wt%-0.06wt% Nb, 0.2wt%-0.8wt% Mn, 0.01wt%-0.05wt% C, with the balance being Fe and unavoidable impurities;

[0014] • The raw materials are melted and cast into ingots to form billets;

[0015] • Remove the oxide scale from the billet;

[0016] • Heating is performed on the billet after removing the oxide scale;

[0017] • Roll the heated square billet into a strip;

[0018] • The strip blank is subjected to water quenching and solution treatment to form a finished strip;

[0019] • The finished strip is cold-rolled at least once until the set first thickness is reached, wherein the total deformation is controlled to be between 50% and 65%;

[0020] • Perform softening annealing;

[0021] • The finished strip of the first thickness is cold rolled at least once more until the set second thickness is reached;

[0022] • The finished strip of the second thickness is subjected to heat treatment and annealing to obtain the set hardness value.

[0023] In an embodiment of the present invention, the raw materials include: 5.0wt%-9.0wt% Co, 0.3wt%-0.7wt% Cr, 1.0wt%-2.0wt% Si, 0.035wt%-0.055wt% Nb, 0.3wt%-0.7wt% Mn, 0.015wt%-0.03wt% C, with the balance being Fe and unavoidable impurities.

[0024] In an embodiment of the present invention, the unavoidable impurities, based on the weight percentage of the raw materials, include: P≤0.02wt%, S≤0.02wt%.

[0025] In an embodiment of the present invention, melting and casting the raw materials to form a billet includes: placing the raw materials in a vacuum induction melting furnace; evacuating to 5×10⁻² Pa; filling with high-purity argon for protection; heating to 1500℃-1600℃ to completely melt the raw materials; refining for 35 minutes to ensure uniform composition; and pouring the molten raw materials into a water-cooled copper mold to obtain an ingot, thus forming the billet.

[0026] In an embodiment of the present invention, heating the billet after removing the oxide scale includes: holding the billet at 1150±30°C for 2 hours. Rolling the heated billet into a strip includes: forging the heated billet into a 60mm thick slab, reheating the slab to 1100-1180°C, holding it for 1 hour, and performing at least one hot rolling to form the strip, with a final rolling thickness of 3-5mm and a final rolling temperature not lower than 900°C. Water quenching and solution treatment of the strip to form the finished strip includes: quenching in ice-salt water below 0°C after hot rolling.

[0027] In an embodiment of the present invention, the heat treatment and annealing of the finished strip of the second thickness to obtain the set hardness value includes: heating to 800-900°C at 5-10°C / min under vacuum or protective atmosphere, holding at the temperature for 2-5 hours, cooling to below 500°C at a rate of 100-400°C / h, and finally furnace cooling or air cooling to room temperature.

[0028] In an embodiment of the present invention, the finished strip of the second thickness is subjected to heat treatment and annealing to obtain a set hardness value, including: heating to 870°C at a rate of 8°C / minute; holding at 800°C for 4 hours; cooling to 600°C at a rate of 200°C / hour; cooling from 600°C to below 80°C at a rate of 400°C / hour; and air cooling to room temperature after removal from the furnace.

[0029] In an embodiment of the present invention, the method further includes: processing the finished strip of the second thickness into a sample ring; cleaning and drying the sample ring; placing the sample ring in a stainless steel heat treatment box with Al2O3 powder at the bottom; and placing the stainless steel heat treatment box in a constant temperature zone in a vacuum heat treatment furnace for heat treatment.

[0030] According to another aspect of the present invention, a low-cobalt soft magnetic alloy strip is also provided, which is made by the method described in any one of the above-mentioned methods.

[0031] According to another aspect of the invention, a low-cobalt soft magnetic alloy material is also provided, comprising, by weight percentage: 3wt%-12wt% Co, 0.2wt%-0.8wt% Cr, 0.6wt%-2.5wt% Si, 0.03wt%-0.06wt% Nb, 0.2wt%-0.8wt% Mn, 0.01wt%-0.05wt% C, with the balance being Fe and unavoidable impurities.

[0032] In embodiments of the present invention, the low-cobalt soft magnetic alloy material comprises, by weight percentage: 5.0wt%-9.0wt% Co, 0.3wt%-0.7wt% Cr, 1.0wt%-2.0wt% Si, 0.035wt%-0.055wt% Nb, 0.3wt%-0.7wt% Mn, 0.015wt%-0.03wt% C, with the balance being Fe and unavoidable impurities. Attached Figure Description

[0033] Figure 1 The flowchart illustrates a method for preparing low-cobalt soft magnetic alloy strips provided by this invention.

[0034] Figure 2 This is a comparison chart of the magnetization curves (BH curves) of the alloys of Embodiment 1, Embodiment 3 and Comparative Example 1 (1J22) under the same test conditions.

[0035] Figure 3 The images show the metallographic structure of the alloy strip prepared in Example 1 of this invention before (left) and after (right) heat treatment, magnified 200 times.

[0036] Figure 4 These are metallographic images of the alloy strip prepared in Example 3 of the present invention, magnified 200 times before (left) and after (right) heat treatment. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments of this invention. The following embodiments are only for further illustrating this invention and should not be construed as limiting the scope of protection of this invention.

[0038] Figure 1 The flowchart illustrates a method for preparing low-cobalt soft magnetic alloy strips provided by this invention.

[0039] like Figure 1 As shown, the method (100) includes the following operations: weighing raw materials (S102), wherein the raw materials include, by weight percentage: 3wt%-12wt% Co, 0.2wt%-0.8wt% Cr, 0.6wt%-2.5wt% Si, 0.03wt%-0.06wt% Nb, 0.2wt%-0.8wt% Mn, 0.01wt%-0.05wt% C, with the balance being Fe and unavoidable impurities; the raw materials are melted and cast into ingots to form a billet (S104); the oxide scale on the billet is removed (S106); the billet after oxide scale removal is heated (S108); the heated billet is rolled into a strip (S110); the strip is water-quenched and solution-treated to form a finished strip (S112); the finished strip is cold-rolled at least once until a set first thickness is reached (S114), wherein the total deformation is controlled at 50%-65%; softening annealing (i.e., intermediate softening annealing) is performed (S116); the finished strip of the first thickness is cold-rolled at least once again until a set second thickness (e.g., 0.35mm, 0.20mm, etc.) is reached (S118); the finished strip of the second thickness is heat-treated and annealed to obtain a set hardness value (S120).

[0040] In an embodiment of the present invention, the process of melting and casting raw materials into ingots to form billets includes: placing the raw materials in a vacuum induction melting furnace; evacuating to 5×10⁻² Pa; filling with high-purity argon for protection; heating to 1500℃-1600℃ to completely melt the raw materials; refining for 35 minutes to ensure uniform composition; and pouring the molten raw materials into a water-cooled copper mold to obtain ingots, thus forming billets.

[0041] In embodiments of the present invention, heating the billet after removing the oxide scale includes: holding the billet at 1150±30°C (e.g., 1180°C) for 2 hours (homogenization treatment). Rolling the heated billet into a strip includes: forging (e.g., multi-directional forging) the heated billet into a slab of the required size (e.g., 60 mm thick), reheating the slab to 1100-1180°C, holding it for 1 hour, and performing at least one (e.g., multiple) hot rolling to form a strip with a final rolling thickness of 3-5 mm and a final rolling temperature not lower than 900°C (e.g., 920°C). Water quenching and solution treatment of the strip to form the finished strip includes: quenching the strip in ice-salt water (or water) below 0°C after hot rolling to refine the initial grain structure.

[0042] In an embodiment of the present invention, heat treatment and annealing of the finished strip of the second thickness to obtain the set hardness value includes: heating to 800-900°C at 5-10°C / min under vacuum or protective atmosphere, holding at the temperature for 2-5 hours, cooling to below 500°C at a rate of 100-400°C / h, and finally furnace cooling or air cooling to room temperature.

[0043] In an embodiment of the present invention, the heat treatment and annealing of the finished strip of the second thickness to obtain the set hardness value includes: heating to 800°C at a rate of 6°C / min (or heating to 870°C at a rate of 8°C / min); holding at 800°C for 4 hours; cooling to 600°C at a rate of 200°C / hour; cooling from 600°C to below 80°C at a rate of 400°C / hour; and air cooling to room temperature after removal from the furnace.

[0044] In an embodiment of the present invention, the method further includes: processing the finished strip into a sample ring; cleaning and drying the sample ring; placing the sample ring in a stainless steel heat treatment box with Al2O3 powder at the bottom; and placing the stainless steel heat treatment box in a constant temperature zone in a vacuum heat treatment furnace for heat treatment.

[0045] In embodiments of the present invention, the addition of Mn to the raw materials helps to increase resistivity and reduce eddy current losses.

[0046] In an embodiment of the present invention, trace amounts of carbon in the raw materials can form carbides with alloying elements, which can play a certain role in precipitation strengthening and improve strength.

[0047] In embodiments of the present invention, the raw materials may include: 5.0wt%-9.0wt% Co, 0.3wt%-0.7wt% Cr, 1.0wt%-2.0wt% Si, 0.035wt%-0.055wt% Nb, 0.3wt%-0.7wt% Mn, 0.015wt%-0.03wt% C, with the balance being Fe and unavoidable impurities.

[0048] In embodiments of the present invention, unavoidable impurities, by weight percentage of raw materials, include: P ≤ 0.02 wt%, S ≤ 0.02 wt%. Furthermore, if C is not actively added, then C ≤ 0.03 wt%.

[0049] This can mitigate the adverse effects of harmful elements on magnetic properties and processing performance. According to another aspect of the invention, a low-cobalt soft magnetic alloy strip is also provided, which can be manufactured by the method described in any of the above-described embodiments.

[0050] According to another aspect of the invention, a low-cobalt soft magnetic alloy material is also provided, comprising, by weight percentage: 3wt%-12wt% Co, 0.2wt%-0.8wt% Cr, 0.6wt%-2.5wt% Si, 0.03wt%-0.06wt% Nb, 0.2wt%-0.8wt% Mn, 0.01wt%-0.05wt% C, with the balance being Fe and unavoidable impurities.

[0051] In an embodiment of the present invention, the low-cobalt soft magnetic alloy material may specifically include: 5.0wt%-9.0wt% Co, 0.3wt%-0.7wt% Cr, 1.0wt%-2.0wt% Si, 0.035wt%-0.055wt% Nb, 0.3wt%-0.7wt% Mn, 0.015wt%-0.03wt% C, with the balance being Fe and unavoidable impurities.

[0052] Table 1. Alloy chemical composition (wt%) of the Examples and Comparative Examples (balance not shown)

[0053] serial number Co Cr Si Nb Mn C Remark Example 1 5.0 0.5 1.8 0.045 0.5 0.02 The alloy of this invention Example 2 5.0 0.5 1.0 0.035 0.3 0.015 The alloy of this invention Example 3 9.0 0.7 1.8 0.055 0.3 0.03 The alloy of this invention Example 4 8.5 0.5 1.8 0.045 0.5 0.02 The alloy of this invention Example 5 5.0 0.3 1.0 0.035 0.3 0.015 The alloy of this invention Example 6 9.0 0.7 2.0 0.055 0.7 0.03 The alloy of this invention Comparative Example 1 50.0 - - - - - Traditional 1J22 alloy Comparative Example 2 3.15 0.05 Non-oriented silicon steel

[0054] The preparation method is as follows (taking Example 1 as an example):

[0055] 1. Melting and Casting: Weigh high-purity iron, cobalt, chromium, ferrosilicon, ferroniobium, and other raw materials according to the proportions in Table 1, place them in a vacuum induction melting furnace, evacuate to 5×10⁻² Pa, and then fill with high-purity argon for protection. Heat to 1550℃ to completely melt the raw materials, refine for 35 minutes to ensure uniform composition, and then pour into a water-cooled copper mold to obtain an ingot. Remove the oxide scale.

[0056] 2. Hot working: The ingot is held at 1180℃ for 2 hours, and then forged into a 60mm thick slab. The slab is reheated to 1150℃, held for 1 hour, and then subjected to multiple hot rolling processes to a final thickness of 4.0mm at a final rolling temperature of approximately 920℃. Immediately after rolling, it is quenched in ice-cold brine (below 0℃).

[0057] 3. Cold rolling and intermediate annealing: The hot-rolled and quenched strip is surface-ground and then cold-rolled from 4.0 mm to 1.5 mm (62.5% deformation). Subsequently, intermediate annealing is carried out under hydrogen protection at a temperature of 850℃ for 1.5 hours, followed by furnace cooling.

[0058] 4. Finished product rolling and final heat treatment: The strip after intermediate annealing is further cold rolled to a final thickness of 0.35 mm. The finished cold-rolled strip is placed in a vacuum heat treatment furnace, heated to 870°C at 8°C / min, held at that temperature for 4 hours, then cooled to 600°C at a rate of 200°C / h, and then cooled to below 80°C (e.g., 80°C) at a rate of 400°C / h. Finally, it is removed from the furnace and air-cooled.

[0059] Performance testing

[0060] The magnetic, mechanical and physical properties of the 0.35 mm thick strips after final heat treatment in Examples 1-3 and Comparative Example 1 were tested, and the results are shown in Table 2.

[0061] The magnetic flux density B was measured under the corresponding magnetic field strengths (H=400 A / m, H=8000 A / m); the saturation magnetic flux density Bs was determined by the impact method; the coercivity Hc was determined by a DC hysteresis loop apparatus; the resistivity ρ was determined by the four-probe method; the Curie temperature Tc was determined by the magnetic balance method; the iron loss P was determined by the Epstein square loop method at the corresponding frequency and magnetic flux density; and the mechanical properties were obtained through tensile tests.

[0062] Table 2. Performance comparison between the alloys of the examples and the comparative examples.

[0063] Performance indicators Example 1 Example 2 Example 3 Comparative Example 1 (1J22) Comparative Example 2: Non-oriented silicon steel Test standards / conditions Magnetic field strength B400 (T) 1.40 1.4 1.45 ~1.45* 1.25 H=400 A / m Magnetic field strength B8000 (T) 1.79 1.72 2.06 ~2.10* 1.71 H=8000 A / m Saturated magnetic induction Bs(T) 2.22 2.20 2.45 2.48 1.80 Peak magnetic field Coercivity Hc (A / m) 45 48 90 32 8 DC return line Resistivity ρ (μΩ·m) 0.55 0.58 0.53 0.40 0.59 room temperature Curie temperature Tc (°C) 915 880 930 980 780 - Iron loss P1.0T / 400Hz (W / kg) 15.2 14.8 15.8 20.5 11.6 f=400Hz, Bm=1.0T Iron loss P1.0T / 60Hz (W / kg) 1.08 1.02 1.12 1.25 1.06 f=60Hz, Bm=1.0T Yield strength Rp0.2 (MPa) 335 325 350 >220 (Highly brittle) 425 room temperature stretching Tensile strength Rm (MPa) 580 565 620 >650 563 room temperature stretching Elongation after fracture A (%) 32 35 28 <5 15 room temperature stretching

[0064] In addition, as examples, some performance metrics of embodiments 4, 5, and 6 are listed below.

[0065] Performance indicators Example 4 Example 5 Example 6 Magnetic field strength B400 (T) 1.35 1.31 1.38 Magnetic field strength B8000 (T) 1.85 1.78 1.90 Saturated magnetic induction Bs(T) 2.08 2.00 2.12 Coercivity Hc (A / m) 45 48 42 Tensile strength Rm (MPa) 580 565 620

[0066] Note: The data in Comparative Example 1 are typical publicly available values. Depending on the processing method, the actual performance of the thin strip may differ from the ideal laboratory values. Such differences do not affect the performance comparison with the embodiments of the present invention.

[0067] Results Analysis

[0068] Figure 2 This is a comparison chart of the magnetization curves (BH curves) of the alloys of Embodiment 1, Embodiment 3 and Comparative Example 1 (1J22) under the same test conditions.

[0069] As shown in the figure, the BH curve of Example 3 is closest to 1J22, exhibiting extremely high magnetic induction intensity under medium and low magnetic fields, indicating that the magnetic permeability and magnetization efficiency are both excellent.

[0070] Figure 3 The images show the metallographic structure of the alloy strip prepared in Example 1 of this invention before (left) and after (right) heat treatment, magnified 200 times.

[0071] Figure 4 These are metallographic images of the alloy strip prepared in Example 3 of the present invention, magnified 200 times before (left) and after (right) heat treatment.

[0072] like Figure 3 and Figure 4 As shown, the following effect can be achieved after heat treatment:

[0073] Optimize magnetic properties: By eliminating deformed structures through recrystallization, reducing the resistance to magnetic domain wall movement, increasing magnetic permeability, and reducing coercivity, the material properties in each embodiment can be made close to 1J22.

[0074] Balanced mechanical properties: Through the combination of deformation and recrystallization, the strength gained from work hardening is retained, while the plasticity and toughness are restored through recrystallization, making the material less prone to brittle fracture during service.

[0075] Controlling grain size: By controlling the recrystallization process, the grain size can be precisely controlled. The finer the grain, the more pinning points of the magnetic domain walls, and the higher the coercivity; the coarser the grain, the higher the permeability and the lower the coercivity. The performance can be customized to a certain extent according to the needs.

[0076] In summary, based on Table 2 and... Figure 2 , Figure 3 , Figure 4 It can be seen that the alloys of Examples 1-6 of the present invention (especially Example 3), even with a cobalt content (5%-11%) far lower than that of the traditional 1J22 alloy (50%), still achieve excellent comprehensive performance after processing according to the methods described in the examples of the present invention:

[0077] 1. High saturation magnetic induction: The saturation magnetic induction intensity (Bs) reaches 2.2-2.37T, which is much higher than that of silicon steel (1.8T) and close to the level of high cobalt alloy, which is conducive to the miniaturization and weight reduction of motors.

[0078] 2. Excellent soft magnetic properties: Coercivity (Hc) is as low as 42-48 A / m, indicating that magnetization and demagnetization are easy and hysteresis loss is small.

[0079] 3. Low iron loss: Due to the addition of elements such as Si and Cr to increase resistivity, the resistivity of the alloy of this invention is significantly higher than that of the 1J22 alloy. Therefore, the iron loss (P) at the 400Hz intermediate frequency is low. 1.0T / 400Hz The iron loss is significantly lower than that of 1J22, demonstrating a clear advantage in high-frequency applications. The power frequency iron loss is also at an extremely low level.

[0080] 4. Good mechanical and processing properties: The yield strength and tensile strength meet the requirements of structural parts, while the elongation after fracture is as high as 28%-35%, which is far superior to the brittle 1J22 alloy (usually <5%). This indicates that the alloy of the present invention has excellent cold working formability and is suitable for stamping complex motor cores.

[0081] 5. Cost advantage: The significantly reduced cobalt content leads to a substantial decrease in raw material costs, giving it enormous application potential and market competitiveness in high-end civilian fields such as eVTOL motors and high-performance robot servo motors.

[0082] Compared to standard silicon steel, this alloy exhibits superior performance, specifically a high saturation induction intensity exceeding 2.22T, low coercivity, high resistivity, and low AC core loss. Furthermore, compared to the traditional 1J22 alloy containing 50% cobalt, the significantly reduced cobalt content results in lower cost and better machinability, making it an ideal soft magnetic alloy for manufacturing high-performance eVTOL motor cores and robot motor cores. In summary, this invention, through sophisticated component ratio design (low cobalt, composite addition of Cr, Si, Nb, Mn, etc.) and optimized manufacturing processes (hot rolling and quenching to refine grains, specific cold rolling and heat treatment regimes), has successfully developed a novel soft magnetic alloy strip that combines high performance, good processability, and low cost, solving the industry problems of excessively high cost of traditional high-cobalt alloys and insufficient performance of traditional silicon steel.

[0083] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing low-cobalt soft magnetic alloy strip (100), characterized in that, include: Weigh the raw materials (S102), which, by weight percentage, include: 3wt%-12wt% Co, 0.2wt%-0.8wt% Cr, 0.6wt%-2.5wt% Si, 0.03wt%-0.06wt% Nb, 0.2wt%-0.8wt% Mn, 0.01wt%-0.05wt% C, with the balance being Fe and unavoidable impurities; The raw materials are melted and cast into ingots to form a billet (S104); the oxide scale on the billet is removed (S106); the billet after oxide scale removal is heated (S108); the heated billet is rolled into a strip (S110); the strip is water-quenched and solution-treated to form a finished strip (S112); the finished strip is cold-rolled at least once until a set first thickness is reached (S114), wherein the total deformation is controlled at 50-65%; softening annealing is performed (S116); the finished strip of the first thickness is cold-rolled at least once again until a set second thickness is reached (S118); the finished strip of the second thickness is heat-treated and annealed to obtain a set hardness value (S120).

2. The method (100) according to claim 1, wherein, The raw materials comprise: 5.0wt%-9.0wt% Co, 0.3wt%-0.7wt% Cr, 1.0wt%-2.0wt% Si, 0.035wt%-0.055wt% Nb, 0.3wt%-0.7wt% Mn, 0.015wt%-0.03wt% C, with the balance being Fe and unavoidable impurities.

3. The method (100) according to any one of claims 1 or 2, characterized in that, The unavoidable impurities, calculated as a percentage of the weight of the raw materials, include: P ≤ 0.02 wt%, S ≤ 0.02 wt%.

4. The method (100) according to any one of claims 1 to 2. in, The process of melting and casting the raw materials to form a billet includes: placing the raw materials in a vacuum induction melting furnace; evacuating to 5×10⁻² Pa; filling with high-purity argon for protection; heating to 1500℃-1600℃ to completely melt the raw materials; refining for 35 minutes to ensure uniform composition; and pouring the molten raw materials into a water-cooled copper mold to obtain an ingot, thus forming the billet. The heating of the billet after removing the oxide scale includes: holding the billet at 1150±30℃ for 2 hours; The process of rolling the heated square billet into a strip includes: forging the heated square billet into a 60mm thick slab, reheating the slab to 1100-1180℃, holding it for 1 hour, and hot rolling it at least once to form the strip, with a final rolling thickness of 3-5mm and a final rolling temperature of not less than 900℃. The process of water quenching and solution treatment of the strip blank to form the finished strip includes: quenching in ice-salt water below 0°C after hot rolling.

5. The method (100) according to any one of claims 1 to 3, wherein, The finished strip of the second thickness is subjected to heat treatment and annealing to obtain the set hardness value, including: heating to 800-900°C at 5-10°C / min under vacuum or protective atmosphere, holding at that temperature for 2-5 hours, cooling to below 500°C at a rate of 100-400°C / h, and finally furnace cooling or air cooling to room temperature.

6. The method (100) according to claim 5, characterized in that, The finished strip of the second thickness is subjected to heat treatment and annealing to obtain the set hardness value, including: heating to 870°C at a rate of 8°C / min; holding at 800°C for 4 hours; cooling to 600°C at a rate of 200°C / hour; cooling from 600°C to below 80°C at a rate of 400°C / hour; and air cooling to room temperature after removal from the furnace.

7. The method (100) according to any one of claims 1 to 2, characterized in that, Also includes: The finished strip of the second thickness is processed into a sample ring; the sample ring is cleaned and dried; the sample ring is placed in a stainless steel heat treatment box with Al2O3 powder at the bottom; the stainless steel heat treatment box is placed in the constant temperature zone of a vacuum heat treatment furnace for heat treatment.

8. A low-cobalt soft magnetic alloy strip, characterized in that, Made by the method described in any one of claims 1 to 7.

9. A low-cobalt soft magnetic alloy material, characterized in that, By weight percentage, it comprises: 3wt%-12wt% Co, 0.2wt%-0.8wt% Cr, 0.6wt%-2.5wt% Si, 0.03wt%-0.06wt% Nb, 0.2wt%-0.8wt% Mn, 0.01wt%-0.05wt% C, with the balance being Fe and unavoidable impurities.

10. The low-cobalt soft magnetic alloy material according to claim 10, characterized in that, By weight percentage, it comprises: 5.0wt%-9.0wt% Co, 0.3wt%-0.7wt% Cr, 1.0wt%-2.0wt% Si, 0.035wt%-0.055wt% Nb, 0.3wt%-0.7wt% Mn, 0.015wt%-0.03wt% C, with the balance being Fe and unavoidable impurities.

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