High-magnetic-induction-intensity non-oriented silicon steel thin strip for automobile driving motor and manufacturing method

Abstract

The invention provides a high-magnetic-induction-intensity non-oriented silicon steel thin strip for an automobile driving motor and a manufacturing method of the high-magnetic-induction-intensity non-oriented silicon steel thin strip, and belongs to the technical field of electrical steel manufacturing. (2) carrying out smelting and RH vacuum treatment according to the components; (3) carrying out normalizing pickling treatment on a hot-rolled coil in a pure nitrogen protective atmosphere; (4) rolling into a cold-rolled coil with the thickness of 0.10-0.30 mm by adopting a secondary cold rolling method; (5) recrystallization annealing is conducted at the temperature of 950-1050 DEG C in the H2 atmosphere (the ratio of H2 to N2 is larger than 1.2: 1), and (6) annealing is conducted on an annealed coil in a bell-type furnace, total magnetic field annealing is increased, the magnetic field intensity is 1.5 T, the annealing temperature is 760 DEG C, cooling is conducted after heat preservation is conducted for 1.5 h, and the non-oriented silicon steel thin strip with the medium-frequency iron loss P1.0 / 400 being 6-12 W / kg, the magnetic induction B5000 being 1.69-1.73 T, the yield strength Rp0.2 being 450-520 Mpa and the excellent performance is obtained. The steel grade developed by the invention can simultaneously meet the non-oriented silicon steel thin strip for the automobile driving motor, which has extremely high requirements on medium-frequency iron loss, magnetic induction and strength and extremely excellent comprehensive performance.

Description

Technical Field

[0001] The invention relates to the technical field of non-oriented silicon steel for driving motors, and in particular to a non-oriented silicon steel thin strip with high magnetic induction intensity for automobile driving motors and a manufacturing method thereof. Background Art

[0002] The automotive industry is one of the main areas of global greenhouse gas emissions. With the continuous increase in the number of cars in my country, how to reduce carbon emissions in the automotive industry is a very important link. In this context, reducing carbon emissions in the transportation sector mainly depends on the electrification of cars, and new energy vehicles will usher in a broad space for growth.

[0003] With the rapid development of economy and society, the performance requirements for new energy vehicles are getting higher and higher. The energy of automobile motors is mainly based on on-board batteries, which have limited energy storage, so the motors need to be as small, light and efficient as possible. Strong power is needed when starting a car, so the motor needs to provide strong torque. In order for a car to travel at high speed and save energy, the motor needs to have an extremely high speed to achieve it, so the motor should have a high comprehensive efficiency at high and low speeds. The high speed of automobile motors brings huge centrifugal force to the rotor, and the gap between the stator and the rotor needs to be closely matched. In summary, the silicon steel used for the motor is required to have high magnetic induction, low iron loss, high strength and other characteristics. In addition, in general, the stator of the drive motor is required to have good magnetic properties, and the rotor has high-strength mechanical properties. The production of the rotor alone requires precision machining, which will greatly increase the production cost of the core. From the perspective of reducing costs, it is more appropriate to use the same silicon steel sheet to stamp the stator and rotor cores, which requires the development of non-oriented silicon steel sheets that take both magnetic properties and mechanical properties into consideration. Therefore, in order to meet the development needs of the new energy vehicle industry, it is imperative to develop non-oriented silicon steel strips with low iron loss, high magnetic induction and high strength.

[0004] The patented technology of "A method for preparing high-strength non-oriented silicon steel strip containing cerium" (CN110129671A) is to make non-oriented silicon steel strip with low medium-frequency iron loss, high magnetic induction and strength of 600 MPa by adding a trace amount of rare earth element Ce and controlling the recrystallization annealing temperature and time. The process flow of this method is relatively short, but the production cost is relatively high due to the addition of rare earth elements; in terms of performance, although the magnetic induction and strength of the obtained material are relatively high, the medium-frequency iron loss is average, and the recrystallization annealing temperature cycle is long, the production efficiency is low, which is not conducive to the realization of industrial continuous production.

[0005] The patented technology of "Non-oriented silicon steel for electric vehicle drive motor and its preparation method" (CN105950960B) adjusts recrystallization by controlling the reasonable ratio of Si, Al, and Mn, and controlling the soaking time and soaking temperature of incomplete recrystallization annealing to obtain a semi-process non-oriented silicon steel strip with a yield strength of 500MPa, which is used to make rotors. At the same time, the semi-process non-oriented silicon steel strip is used to make motor stators and rotors after stress relief annealing. The component system of this method is relatively simple, and no other alloy elements are added. Although the obtained rotor strength is higher and the magnetic properties of the stator are better, the non-oriented silicon steel for the stator must also use additional stress relief annealing, and the process is complicated. In addition, in order to obtain high strength, the non-oriented silicon steel used for the rotor adopts incomplete recrystallization annealing. Although the magnetic properties of the non-oriented silicon steel strip for the rotor are not disclosed in this patented technology, it can be inferred that its magnetic properties are not good due to its incomplete recrystallization.

[0006] The patented technology of "A method for manufacturing high-strength non-oriented silicon steel for new energy vehicle drive motor" (CN106435358B) and "A method for preparing high-magnetic induction and high-strength non-oriented silicon steel based on thin strip continuous casting" use thin strip continuous casting technology to prepare high-strength non-oriented silicon steel, whose composition is added with unconventional elements such as Ni, Cr, Nb, Sn, etc., and the composition system is more complex, and the requirements for smelting and each process are also higher; the obtained medium frequency iron loss P 1.0 / 400 Higher.

[0007] The patented technology of "A high-strength cold-rolled non-oriented silicon steel for drive motors and its manufacturing method" (CN107746941A) balances the magnetic induction intensity, iron loss and yield strength of the prepared non-oriented silicon steel by adding trace elements such as Cr and Nb and controlling the secondary cold rolling reduction and the two annealing processes. However, this method mainly uses high temperature and short time to rearrange dislocations, that is, to strengthen dislocations; at the same time, the pinning effect of Nb is used to retain part of the deformation structure, that is, the grains in the sample are not fully grown after annealing. Therefore, the mid-frequency iron loss performance is poor, P 1.0 / 400 It is 18.8~32.12W / kg.

[0008] The patented technology of "A high-strength copper-containing cold-rolled non-oriented silicon steel and its manufacturing method" (CN107130169A) obtains high-strength copper-containing non-oriented silicon steel by adding trace elements such as Cu and controlling the secondary cold rolling reduction and the two annealing processes. Although the strength is high, reaching 800Mpa, the magnetic induction intensity and medium-frequency iron loss are average, B 5000 It is 1.64-1.66T, W1.0 / 400 is 20.04-25.04W / kg, and it has one more aging treatment process than the conventional non-oriented silicon steel production process, with a long production cycle and complex process flow.

[0009] Patent CN102453838A discloses a "high-strength non-oriented electrical steel with higher magnetic induction and its manufacturing method". In the traditional production process, by improving the composition and adding 1%-8% Cr and 0.5%-5% Ni, a large amount of alloy elements are dissolved in the matrix to improve the mechanical properties of the non-oriented silicon steel, while also increasing the production cost of the high-strength non-oriented silicon steel.

[0010] The present invention aims to solve the technical bottleneck of the mutual restriction between the magnetic induction and iron loss of high-grade non-oriented silicon steel, and provide a method for preparing a high magnetic induction strength non-oriented silicon steel thin strip with relatively simple preparation process, low alloy cost and extremely excellent comprehensive performance. The high magnetic induction strength non-oriented silicon steel thin strip prepared by the method can be mass-produced and applied to automobile drive motors with extremely high requirements on medium-frequency iron loss, magnetic induction and strength. Summary of the invention

[0011] The purpose of the present invention is to solve the above problems and provide a high magnetic induction intensity non-oriented silicon steel strip for automobile drive motor and a manufacturing method thereof.

[0012] The object of the present invention is achieved in that the composition of the non-oriented silicon steel strip with high magnetic induction intensity for automobile drive motor is as follows: C≤0.003wt%, S≤0.001wt%, Si: 3.3~3.7wt%, Al: 0.7~1.5wt%, Mn: 0.1~0.5wt%, S+N+Ti≤0.005wt%, P≤0.01wt%, V+Zr≤0.004wt%, and the rest is Fe and unavoidable impurities.

[0013] The invention discloses a non-oriented silicon steel strip with high magnetic induction strength for automobile drive motor and a manufacturing method thereof, comprising the following steps: step 1: smelting and continuous casting: the composition is as follows: C≤0.003wt%, S≤0.001wt%; Si: 3.3-3.7wt%, Al: 0.7-1.5wt%, Mn: 0.1-0.5wt%, S+N+Ti≤0.005wt%, P≤0.01wt%, V+Zr≤0.004wt%, and the rest is Fe and unavoidable impurities; smelting, RH vacuum treatment and casting into a 220-230mm thick ingot are carried out according to the above composition, and the ingot is heated to 1100℃~1200℃, keep warm for 50-70min, and quickly hot-roll to a hot-rolled coil with a thickness of 1.0mm~2.0mm; Step 2: The hot-rolled coil is normalized and pickled in a pure nitrogen protective atmosphere, the normalization temperature is maintained at 850℃~950℃, the speed is ≤20m / min, and then cooled to room temperature; Step 3: Cold rolling and first annealing process: The cold-rolled coil with a thickness of 0.10~0.25mm is rolled by the secondary cold rolling method, the first cold rolling reduction rate is controlled at 50%~70%, the intermediate annealing temperature is 800℃-900℃, and the intermediate annealing time is 2-5min; Step 4: Second annealing process: in H2 Atmosphere H 2 :N 2 Ratio: 1.2-1.5:1, 950℃~1050℃ recrystallization annealing, annealing time 3-10min, cooling at a speed of less than 40℃ / s, coating and coiling; Step 5: annealing and coiling in a bell-type furnace, adding full magnetic field annealing, magnetic field strength of 1.5-1.8T, annealing temperature of 720-780℃, keeping warm for 1.5-2h and then cooling, so as to obtain a non-oriented silicon steel strip with medium frequency iron loss P1.0 / 400 of 6~12W / kg, magnetic induction of 1.69~1.73T and yield strength of 450~520Mpa.

[0014] The beneficial effects of the present invention are as follows: under the premise of high Si and Al alloy components and extremely low S, N, Ti, V and Zr, the present invention adopts a secondary cold rolling method, reasonably designs normalization and two annealing processes, and cold rolling reduction rate parameters, and uses a bell-type furnace plus a magnetic field to perform annealing for a certain period of time to improve the strength of favorable textures such as {100} surface texture components, Gaussian texture components and η texture components, thereby greatly improving the magnetic induction intensity and continuing to reduce the iron loss; the problems that the preparation process of the existing non-oriented silicon steel strip is difficult and the magnetic properties and mechanical properties are difficult to take into account are solved, the bottleneck of continuing to improve the magnetic properties is broken, and on the basis of the existing high-efficiency and high-strength non-oriented silicon steel performance with excellent comprehensive performance, the performance improvement potential is extremely excavated, and the magnetic properties of the non-oriented silicon steel strip are continued to be improved, and the magnetic induction intensity of the produced strip is increased by more than 0.02T compared with conventional high-strength silicon steel, the medium-frequency iron loss is reduced by more than 1W / kg, and the strength is still maintained at a relatively high level. DETAILED DESCRIPTION

[0015] The present invention designs a non-oriented silicon steel thin strip with high magnetic induction intensity for automobile drive motors and a brand-new manufacturing method, designs a new component system with relatively high main alloy elements such as Si and Al and low steel purity elements such as C, S, N, Ti, V and Zr; and produces it by a secondary cold rolling method with reasonable distribution of cold rolling reduction rate and reasonable design of two annealing process parameters, and then performs magnetic field annealing in a bell-type furnace to obtain silicon steel products for automobile drive motors with extremely excellent comprehensive properties such as medium frequency iron loss, magnetic induction and strength.

[0016] A non-oriented silicon steel strip with a high magnetic induction strength and a special composition design has the following composition: C≤0.003wt%, S≤0.001wt%; Si: 3.3~3.7wt%, Al: 0.7~1.5wt%, Mn: 0.1~0.5wt%, S+N+Ti≤0.005wt%, P≤0.01wt%, V+Zr≤0.004wt%, and the rest is Fe and unavoidable impurities.

[0017] 1. According to the above composition, the steel is smelted, RH vacuum treated, and cast into a 220 mm thick ingot. The ingot is heated to 1100°C~1200°C, kept warm for 60 minutes, and quickly hot-rolled to a 1.0 mm~2.0 mm thick hot-rolled coil.

[0018] 2. Hot rolled coil normalizing process: The hot rolled coil is normalized and pickled in a pure nitrogen protective atmosphere, the normalizing temperature is maintained at 850℃~950℃, the speed is ≤20m / min, and then quickly cooled to room temperature.

[0019] 3. First cold rolling and annealing process: The secondary cold rolling method is used to roll the cold rolled coil into a thickness of 0.10~0.25mm, in which the first cold rolling reduction rate is controlled at 50%~70%, and the intermediate annealing temperature is 800℃-900℃.

[0020] 4. Second annealing process: in H 2 Atmosphere (H 2 :N 2 Ratio: 1.2:1) 950℃~1050℃ recrystallization annealing, annealing time 3-10min, slowly cooling at a speed of less than 40℃ / s, coating and coiling.

[0021] 5. A special magnetic field annealing process: annealing coil in a bell-type furnace, adding full magnetic field annealing, magnetic field strength of 1.5T, annealing temperature of 760℃, 1.5h insulation and then cooling, to obtain non-oriented silicon steel thin strip with excellent performance of medium frequency iron loss P1.0 / 400 of 6~12W / kg, magnetic induction B5000 of 1.69~1.73T, and yield strength Rp0.2 of 450~520Mpa.

[0022] The steel type developed by the present invention can simultaneously meet the extremely high requirements on medium frequency iron loss, magnetic induction and strength and has extremely excellent comprehensive performance for non-oriented silicon steel thin strips for automobile drive motors.

[0023] The present invention improves the strength of the non-oriented silicon steel strip by utilizing the solid solution strengthening effect of relatively high Si and Al alloy components; prevents the cooling precipitation of fine dispersed second phases by controlling the elements affecting the purity of steel such as C, S, N, Ti, V, Zr, etc. during smelting, thereby reducing the rotation resistance of magnetic domains; improves the comprehensive favorable texture ratio by adopting a secondary cold rolling method, designing a reasonable normalizing process, an intermediate annealing process, and a cold rolling reduction rate; reduces iron loss and improves magnetic induction by reasonably matching the temperature parameters of the two annealings; improves the strength of favorable textures such as {100} surface texture components, Gaussian texture components, and η texture components by using a bell-type furnace with a magnetic field for a certain period of time to carry out heat preservation annealing, thereby continuing to improve the magnetic induction intensity and appropriately reducing the iron loss; and comprehensively utilizing the above multiple control means, a high magnetic induction intensity non-oriented silicon steel strip with extremely excellent comprehensive performance of medium-frequency iron loss, magnetic induction, and strength can be prepared.

[0024] The present invention is a new technical attempt to develop the high magnetic induction non-oriented silicon steel strip for automobile drive motors, which combines the smelting composition, normalizing process, cold rolling reduction rate, double annealing process and magnetic field annealing process. The produced high magnetic induction non-oriented silicon steel for automobile drive motors has excellent comprehensive performance in medium-frequency iron loss, magnetic induction and strength.

[0025] In order to make the purpose, technical points and advantages of the invention more clear and easy to understand, the specific implementation methods of the present invention are described in detail below, and the present invention is not limited to the specific embodiments disclosed below. Example 1

[0026] A high magnetic induction strength non-oriented silicon steel strip for automobile drive motor and a manufacturing method thereof. The preparation method described in this embodiment is: the chemical composition of the high magnetic induction strength non-oriented silicon steel strip is: C is 0.003wt%, S is 0.001wt%, Si is 3.45wt%; Al is 1.2wt%; Mn is 0.40wt%; S+N+Ti=0.004wt%, P is 0.01wt%, V+Zr=0.003wt%; the rest is Fe and unavoidable impurities.

[0027] The preparation method of the non-oriented silicon steel strip with high magnetic induction strength is as follows: smelting according to the chemical composition of the non-oriented silicon steel strip, RH vacuum treatment, casting into a 220mm thick ingot; heating the ingot to 1150°C, keeping it warm for 1h, and then hot rolling it to a hot-rolled coil with a thickness of 1.8mm; then the hot-rolled coil is subjected to normalizing pickling treatment in a pure nitrogen protective atmosphere, the normalizing temperature is 880°C, the speed is 15m / min, and then it is quickly cooled to room temperature; the hot-rolled plate after normalizing treatment is cold-rolled to 0.80mm at room temperature; then the cold-rolled plate is first annealed at 900°C for 3min; the annealed cold-rolled plate is secondarily cold-rolled to 0.25mm, and then it is heated at 1000°C and dried with 60% H 2 +40%N 2 Recrystallization annealing in protective atmosphere for 5 minutes and slowly cooling at 35℃ / s to coat the coating and coil it; annealing in a bell furnace with a magnetic field strength of 1.5T and an annealing temperature of 760℃ for 1.5h; the magnetic properties of the obtained product are B 5000 =1.73T, iron loss W 1.0 / 400 =11.9W / kg, mechanical properties: Rp 0.2 =483MPa. Example 2

[0028] A high magnetic induction intensity non-oriented silicon steel strip for automobile drive motor and a manufacturing method thereof. The preparation method described in this embodiment is: the chemical composition of the high magnetic induction intensity non-oriented silicon steel strip is: C is 0.002wt%, S is 0.001wt%, Si is 3.5wt%; Al is 1.0wt%; Mn is 0.25wt%; S+N+Ti=0.0045wt%, P is 0.006wt%, V+Zr=0.003wt%; the rest is Fe and unavoidable impurities.

[0029] The preparation method of the non-oriented silicon steel strip with high magnetic induction strength is as follows: smelting the non-oriented silicon steel strip according to its chemical composition, RH vacuum treatment, and casting into a 220mm thick ingot; heating the ingot to 1150°C, keeping it warm for 1h, and then hot rolling it to a hot-rolled coil with a thickness of 1.8mm; then normalizing the hot-rolled coil in a pure nitrogen protective atmosphere, with a normalizing temperature of 900°C and a speed of 20m / min, and then rapidly cooling it to room temperature; cold rolling the hot-rolled plate after normalizing treatment to 0.70mm at room temperature, and then annealing the cold-rolled plate for the first time at 860°C for 3min; cold rolling the annealed cold-rolled plate for the second time to 0.20mm, and then annealing the cold-rolled plate at 970°C and dry 60% H 2 +40%N 2 Recrystallization annealing in protective atmosphere for 5 minutes and slowly cooling at 35℃ / s to coat the coating and coil it; annealing in a bell furnace with magnetic field intensity of 1.5T, annealing temperature of 760℃, 1.5h. Magnetic properties of the obtained product B 5000 =1.71T, iron loss W 1.0 / 400 =10.6W / kg, mechanical properties Rp 0.2 =467MPa. Example 3

[0030] A non-oriented silicon steel strip with high magnetic induction intensity for automobile drive motor and a manufacturing method thereof. The preparation method described in this embodiment is as follows: the chemical composition of the non-oriented silicon steel strip with high magnetic induction intensity is: C is 0.003wt%, S is 0.0005wt%, Si is 3.45wt%; Al is 0.9wt%; Mn is 0.15wt%; S+N+Ti=0.0040wt%, P is 0.005wt%, V+Zr=0.003wt%; the rest is Fe and unavoidable impurities.

[0031] The preparation method of the non-oriented silicon steel strip with high magnetic induction strength is as follows: smelting according to the chemical composition of the non-oriented silicon steel strip, RH vacuum treatment, casting into a 220mm thick ingot; heating the ingot to 1150°C, keeping it warm for 1h, and then hot rolling it to a hot-rolled coil with a thickness of 1.8mm; then normalizing the hot-rolled coil in a pure nitrogen protective atmosphere, the normalizing temperature is 850°C, the speed is 15m / min, and then rapidly cooled to room temperature, the hot-rolled plate after normalization is cold-rolled to 0.6mm at room temperature, and then the cold-rolled plate is first annealed at 850°C for 3min. The annealed cold-rolled plate is cold-rolled for a second time to 0.15mm, and then heated at 970°C and dry 60% H 2 +40%N 2 Recrystallization annealing in protective atmosphere for 6 minutes and slowly cooling at 35℃ / s to coat the coating and coil it; annealing in a bell furnace with magnetic field intensity of 1.5T, annealing temperature of 760℃, 1.5h. Magnetic properties of the obtained product B 5000 =1.70T, iron loss W 1.0 / 400 =9.4W / kg, mechanical properties: Rp 0.2 =453MPa. Example 4

[0032] A non-oriented silicon steel strip with high magnetic induction intensity for automobile drive motor and a manufacturing method thereof. The preparation method described in this embodiment is as follows: the chemical composition of the non-oriented silicon steel strip with high magnetic induction intensity is: C is 0.0015wt%, S is 0.001wt%, Si is 3.6wt%; Al is 1.4wt%; Mn is 0.20wt%; S+N+Ti=0.0030wt%, P is 0.003wt%, V+Zr=0.002wt%; the rest is Fe and unavoidable impurities.

[0033] The preparation method of the non-oriented silicon steel strip with high magnetic induction strength is as follows: smelting according to the chemical composition of the non-oriented silicon steel strip, RH vacuum treatment, casting into a 220mm thick ingot; heating the ingot to 1150°C, keeping it warm for 1h, and then hot rolling it to a hot-rolled coil with a thickness of 1.3mm; then normalizing the hot-rolled coil in a pure nitrogen protective atmosphere, with a normalizing temperature of 860°C and a speed of 10m / min, and then rapidly cooling it to room temperature; the hot-rolled plate after normalization is cold-rolled to 0.40mm at room temperature, and then the cold-rolled plate is annealed for the first time at 820°C for 3min. The annealed cold-rolled plate is cold-rolled for the second time to 0.10mm, and then annealed at 990°C and dry 60% H 2 +40%N 2 Recrystallization annealing in protective atmosphere for 3 minutes and slowly cooling at 35℃ / s to apply the coating and coil it; annealing in a bell furnace with a magnetic field strength of 1.5T and an annealing temperature of 760℃ for 1.5h. Magnetic properties of the obtained product B5000 =1.69T, iron loss W 1.0 / 400 =6.5W / kg, mechanical properties: Rp 0.2 =515MPa.

[0034] Although the present invention is described in conjunction with the above embodiments, the present invention is not limited to the above embodiments but is only limited by the appended claims and can be easily modified and varied by a person skilled in the art without departing from the essential concept and scope of the present invention.

Claims

1. High magnetic induction strength non-oriented silicon steel strip for automobile drive motor, characterized by: The composition is as follows: C≤0.003wt%, S≤0.001wt%, Si: 3.3~3.7wt%, Al: 0.7~1.5wt%, Mn: 0.1~0.5wt%, S+N+Ti≤0.005wt%, P≤0.01wt%, V+Zr≤0.004wt%, and the rest are Fe and unavoidable impurities.

2. A method for manufacturing a non-oriented silicon steel strip with high magnetic induction intensity for automobile drive motors, characterized in that: The following steps are involved: Step 1: smelting, continuous casting: the composition is as follows: C≤0.003wt%, S≤0.001wt%; Si: 3.3~3.7wt%, Al: 0.7~1.5wt%, Mn: 0.1~0.5wt%, S+N+Ti≤0.005wt%, P≤0.01wt%, V+Zr≤0.004wt%, and the rest is Fe and unavoidable impurities; smelting, RH vacuum treatment, and casting into a 220-230mm thick ingot according to the above composition, heating the ingot to 1100℃~1200℃, keeping warm for 50-70min, and rapidly hot rolling to a 1.0mm~2.0mm thick hot rolled coil; Step 2: The hot rolled coil is subjected to normalized pickling treatment in a pure nitrogen protective atmosphere, the normalizing temperature is maintained at 850°C~950°C, the speed is ≤20m / min, and then cooled to room temperature; Step 3: Cold rolling and first annealing process: The cold rolled coil is rolled into a thickness of 0.10-0.25 mm by the secondary cold rolling method. The first cold rolling reduction rate is controlled at 50%-70%, the intermediate annealing temperature is 800℃-900℃, and the intermediate annealing time is 2-5min. Step 4: Second annealing process: recrystallization annealing at 950℃~1050℃ in H2 atmosphere (i.e. H2:N2 ratio: 1.2-1.5:1), annealing time 3-10min, cooling the coating at a speed of less than 40℃ / s and coiling; Step 5: Annealing: The coil is placed in a bell-type furnace and full magnetic field annealing is added. The magnetic field strength is 1.5-1.8T, the annealing temperature is 720-780℃, and the temperature is kept for 1.5-2h before cooling. Then, a non-oriented silicon steel strip with a medium frequency iron loss P1.0 / 400 of 6-12W / kg, a magnetic induction of 1.69-1.73T, and a yield strength of 450-520Mpa is obtained.