Fe-si soft magnetic material having excellent properties and method for manufacturing the same

Abstract

The application discloses a Fe-Si soft magnetic material with excellent performance, which contains Fe and inevitable impurities, and further contains the following chemical elements with mass percentage as follows: Si: 2.8%-3.4%, Mn: 0.2-0.5%, Al: 0.2-0.8%, Ti: 0.0005-0.1%. The application further discloses a manufacturing method of the Fe-Si soft magnetic material, which comprises the following steps: smelting and casting; hot rolling; annealing of the hot rolling plate; cold rolling; product annealing: in a heating temperature interval of 630 DEG C-820 DEG C, the temperature rising rate is controlled to be 175 DEG C / s-300 DEG C / s; and coating an insulating coating. The obtained Fe-Si soft magnetic material has ultrahigh strength and high-frequency low loss, and can meet the requirements of high power density driving motor, high efficiency, miniaturization and high reliability.

Description

Technical Field

[0001] This invention relates to a metallic material, and more particularly to an Fe-Si soft magnetic material. Background Technology

[0002] With the development of the new energy vehicle industry, the demand for electric drive motors is increasing, and the performance requirements are also getting higher. Taking permanent magnet synchronous drive motors as an example, the power density of the motors is getting higher and higher, the size of the motors is getting smaller and smaller, and at the same time, the safety and reliability of the motors must be guaranteed.

[0003] Increasing motor speed is a crucial means of improving performance. Under the same power conditions, an increase in rotor speed corresponds to a decrease in torque, allowing for a corresponding reduction in motor size. For the soft magnetic materials that make up the motor, when used in the rotor, they need to possess sufficiently high strength; when used in the stator, the material must exhibit high frequency and low loss characteristics. This is to meet the requirements of high-power-density drive motors under high-speed operating conditions, resisting the risk of fracture failure while minimizing energy loss.

[0004] Chinese patent document CN112635146A, published on April 9, 2021, entitled "A Soft Magnetic Hybrid Powder for High-Frequency Applications, Its Preparation Method and Uses," discloses a soft magnetic hybrid powder for high-frequency applications, its preparation method, and its uses. This method involves mixing soft magnetic powders with different magnetic properties, including Fe-Si soft magnetic alloys, Fe-Si-Cr soft magnetic alloys, and Fe-Si-Ni soft magnetic alloys, and homogenizing them in a three-dimensional mixer. The resulting magnetic core is obtained through processes such as coating, granulation, molding, and annealing. The product is mainly used in the field of inductive electronic components. However, the manufacturing process described in this patent document is lengthy, and the product size is limited, making it unsuitable for manufacturing drive motors. Summary of the Invention

[0005] One of the objectives of this invention is to provide a Fe-Si soft magnetic material with excellent performance. This soft magnetic material, through the control of the material's composition, microstructure, and special grain boundaries, possesses ultra-high strength, high frequency, and low loss, which can meet the requirements of high efficiency, miniaturization, and high reliability of high power density drive motors.

[0006] To achieve the above objectives, the present invention provides an Fe-Si soft magnetic material with excellent properties, which contains Fe and unavoidable impurities, and further contains the following chemical elements in the following mass percentages:

[0007] Si: 2.8%-3.4%, Mn: 0.2-0.5%, Al: 0.2-0.8%, Ti: 0.0005-0.1%.

[0008] Furthermore, in the Fe-Si soft magnetic material described in this invention, the mass percentage content of each chemical element is as follows:

[0009] Si: 2.8%-3.4%, Mn: 0.2%-0.5%, Al: 0.2%-0.8%, Ti: 0.0005%-0.1%; balance Fe and unavoidable impurities.

[0010] The design principles of each chemical element in the Fe-Si soft magnetic material with excellent performance described in this invention are as follows:

[0011] Si: In the Fe-Si soft magnetic material with excellent properties described in this invention, Si is an element that increases the resistivity of the alloy. Si can reduce iron loss and also plays a role in solid solution strengthening. To achieve the effects of this invention, the Si content needs to be above 2.8%. However, when the mass percentage of Si is too high, it will affect the cold rolling processability of the material. Therefore, in the Fe-Si soft magnetic material with excellent properties described in this invention, the mass percentage of Si is controlled between 2.8% and 3.4%.

[0012] Mn: In the Fe-Si soft magnetic material with excellent properties described in this invention, the Mn element can improve the plasticity of the slab during hot rolling. However, when the mass percentage of Mn is too high, it will increase the alloy cost. Therefore, in the Fe-Si soft magnetic material with excellent properties described in this invention, the mass percentage of Mn is controlled between 0.2% and 0.5%.

[0013] Al: In the Fe-Si soft magnetic material with excellent performance described in this invention, Al element can increase the material resistivity and reduce losses. Simultaneously, Al element readily combines with N element to form AlN precipitates, and the ratio of the two needs to be strictly controlled. In this invention, to achieve the desired effects, the Al element content needs to be controlled at 0.2% or higher. Therefore, in the Fe-Si soft magnetic material with excellent performance described in this invention, considering both cost and the performance level achievable by this invention, the mass percentage of Al element is controlled between 0.2% and 0.8%.

[0014] Ti: In the Fe-Si soft magnetic material with excellent performance described in this invention, Ti acts as a solid solution strengthening element, which can improve the material strength. However, because Ti readily combines with C and N elements, it forms fine-sized TiC and TiN precipitates under uncontrolled conditions. These precipitates hinder grain boundary movement during annealing and recrystallization, resulting in grain refinement and iron loss degradation. Therefore, in order to utilize the strengthening effect of Ti while avoiding iron loss degradation, this invention requires controlling the content of Al and Ti elements and the ratio of C and N elements to sufficiently coarsen the AlN, TiC, and TiN precipitate particles, reducing their impact on grain growth and thus avoiding iron loss degradation while obtaining a relatively ideal high yield strength. Therefore, in the Fe-Si soft magnetic material with excellent performance described in this invention, the mass percentage of Ti element is controlled between 0.0005% and 0.1%.

[0015] Furthermore, in the Fe-Si soft magnetic material described in this invention, the mass percentage content of each chemical element also satisfies (Ti / 48+Al / 27) / (C / 12+N / 14)≥35.

[0016] In this invention, the content ratio of Al and Ti elements to C and N elements is controlled to conform to the relationship (Ti / 48+Al / 27) / (C / 12+N / 14)≥35, which can prevent the formation of fine AlN, TiC, and TiN precipitates and hinder grain growth during annealing.

[0017] Furthermore, the Fe-Si soft magnetic material described in this invention also contains at least one of the following:

[0018] Sn: 0.01-0.15%;

[0019] 0 < Mg ≤ 0.01%.

[0020] In the above technical solution of the present invention, in order to further optimize the performance of Fe-Si soft magnetic materials with excellent properties, the steel may also contain Sn and Mg elements. Wherein:

[0021] Sn: In the Fe-Si soft magnetic material with excellent performance described in this invention, Sn is a grain boundary segregation element that can improve the material texture and enhance the magnetic properties of the Fe-Si soft magnetic material. However, when the mass percentage of Sn is too high, it will refine the grain structure and increase the alloy cost. Therefore, in the Fe-Si soft magnetic material with excellent performance described in this invention, the mass percentage of Sn is controlled between 0.01% and 0.15%.

[0022] Mg: In the Fe-Si soft magnetic material with excellent performance described in this invention, Mg is chemically reactive. Furthermore, during the smelting process, adding an appropriate amount of Mg alloy can mitigate the formation of new spinel-like inclusions and the deterioration of the strip surface quality when the Mg content is too high. Therefore, in the Fe-Si soft magnetic material with excellent performance described in this invention, the mass percentage of Mg is controlled to be 0 < Mg ≤ 0.01%.

[0023] Furthermore, in the unavoidable impurities of the Fe-Si soft magnetic material described in this invention, C≤0.004%, P≤0.02%, S≤0.003%, and N≤0.003%.

[0024] In the Fe-Si soft magnetic material described in this invention, C, P, S, and N are all impurity elements in the Fe-Si soft magnetic material. Where technical conditions permit, to obtain steel with better performance and superior quality, the content of impurity elements in the steel should be reduced as much as possible. Specifically:

[0025] C: In the Fe-Si soft magnetic material with excellent performance described in this invention, element C is an impurity element, which is detrimental to the magnetism of the soft magnetic material. When the residual content of element C is too high, magnetic failure will occur, leading to deterioration of iron loss. Therefore, in the Fe-Si soft magnetic material with excellent performance described in this invention, the mass percentage content of element C is controlled to C≤0.004%.

[0026] P: In the Fe-Si soft magnetic material with excellent properties described in this invention, phosphorus (P) tends to segregate at grain boundaries, increasing the brittleness of the sheet and making cold rolling difficult. Therefore, in the Fe-Si soft magnetic material with excellent properties described in this invention, the mass percentage of phosphorus is controlled to P ≤ 0.02%.

[0027] S: In the Fe-Si soft magnetic material with excellent performance described in this invention, sulfur (S) is an impurity element. When S combines with manganese (Mn), it forms fine MnS precipitates, hindering grain growth and degrading magnetic properties. Therefore, in the Fe-Si soft magnetic material with excellent performance described in this invention, the mass percentage of sulfur is controlled to be S ≤ 0.003%.

[0028] N: In the Fe-Si soft magnetic material with excellent performance described in this invention, nitrogen (N) will form fine precipitates AlN with Al, which will hinder recrystallization grain growth and also cause magnetic aging. Therefore, in the Fe-Si soft magnetic material with excellent performance described in this invention, the mass percentage of nitrogen (N) is controlled to be N≤0.003%.

[0029] Furthermore, in the Fe-Si soft magnetic material described in this invention, its {001} <210> The orientation intensity of the texture is ≥2.0.

[0030] In this invention, the {001} of the Fe-Si soft magnetic material <210> The orientation intensity of the texture is ≥2.0, wherein the {100} crystal plane is parallel to the strip surface. During the magnetization process of rotating electrical machinery, the {100} crystal plane contains two easily magnetized elements. <100> A shaft helps reduce magnetic losses in materials.

[0031] Furthermore, in the Fe-Si soft magnetic material described in this invention, the iron loss P... 10 / 600 ≤50W / kg.

[0032] Furthermore, the yield strength of the Fe-Si soft magnetic material described in this invention is ≥445MPa.

[0033] In this invention, the Fe-Si soft magnetic material with excellent properties, after annealing, can be directly used as the rotor and stator of a drive motor core. The material exhibits high-frequency iron loss P at a frequency of 600Hz and a maximum magnetic polarization of 1.0T. 10 / 600 With a strength of ≤50W / kg and a yield strength of ≥445MPa, it can meet the requirements of high-speed rotor operation without breakage, while reducing motor iron loss.

[0034] Another objective of this invention is to provide a method for manufacturing Fe-Si soft magnetic materials, which can obtain Fe-Si soft magnetic materials with ultra-high strength and low frequency and low loss properties.

[0035] To achieve the above objectives, the present invention provides a method for manufacturing Fe-Si soft magnetic materials, comprising the following steps:

[0036] Smelting and casting;

[0037] Hot-rolled;

[0038] Annealing of hot-rolled steel sheet;

[0039] Cold rolling;

[0040] Finished product annealing: In the heating range of 630℃-820℃, the heating rate is controlled at 175℃ / s-300℃ / s;

[0041] Apply an insulating coating.

[0042] In the heating range of 630℃-820℃ in this invention, the heating rate is controlled within the range of 175℃ / s-300℃ / s. This is because: during the finished product annealing process, when the strip temperature reaches 630℃, recrystallization and nucleation begin inside the alloy strip. By controlling the heating rate in this heating range to be above 175℃ / s, it is beneficial to {001} <210> Oriented grain nucleation occurs; however, when the heating rate exceeds 300℃ / s, the residence time in the heating section is too short, which is not conducive to recrystallization nucleation.

[0043] Furthermore, in the finished product annealing step of the manufacturing method described in this invention: the homogenization temperature is controlled at 820℃-900℃, and the homogenization holding time is 10s-20s.

[0044] In the finished product annealing step of the present invention, the grains inside the strip can grow appropriately, especially {001}. <210> The oriented grains grow further. Excessively high homogenization temperature or excessively long homogenization time may lead to overly large grains, reducing yield strength. Therefore, in this invention, it is best to control the homogenization temperature at 820℃-900℃ and the homogenization holding time at 10s-20s.

[0045] The Fe-Si soft magnetic material with excellent properties and its manufacturing method described in this invention have the following advantages and beneficial effects:

[0046] The Fe-Si soft magnetic material and its manufacturing method described in this invention, with its excellent performance, achieve ultra-high strength, high frequency and low loss through the design of the material composition. After the finished product is annealed, it can be used as the stator and rotor material of motors, meeting the requirements of high efficiency, miniaturization and high reliability of high power density drive motors.

[0047] In some embodiments, the iron loss P of the Fe-Si soft magnetic material with excellent performance described in this invention... 10 / 600 ≤50W / kg, yield strength ≥445MPa. Detailed Implementation

[0048] The following will further explain and illustrate the Fe-Si soft magnetic material with excellent performance and its manufacturing method according to the present invention with reference to specific embodiments. However, this explanation and illustration do not constitute an undue limitation on the technical solution of the present invention.

[0049] Examples 1-8 and Comparative Examples 1-3

[0050] The Fe-Si soft magnetic materials with excellent properties in Examples 1-8 of this invention and the comparative materials in Comparative Examples 1-3 were prepared using the following steps:

[0051] (1) Smelting and casting: blast furnace molten iron undergoes molten iron pretreatment, converter smelting, RH refining, and continuous casting and rolling to obtain cast billets.

[0052] (2) Hot rolling: The billet heating temperature can be 1150℃, the holding time is 2h, the final rolling temperature can be 930℃, and finally hot rolled to a thickness of 2.2mm.

[0053] (3) Annealing of hot-rolled plate: In order to fully recrystallize the grain structure of hot-rolled plate, the holding temperature can be 940℃ and the holding time can be 10min.

[0054] (4) Cold rolling: Cold rolling yields finished products with a thickness of 0.25 mm or 0.30 mm.

[0055] (5) Finished product annealing: In the heating and heating section between 630℃ and 820℃, the heating rate is controlled between 175℃ / s and 300℃ / s, the soaking temperature is controlled between 820℃ and 900℃, and the soaking time is 10s-20s.

[0056] (6) Applying an insulating coating: After the finished product is annealed, an insulating coating is applied to the surface of the strip.

[0057] Table 1 lists the mass percentage of each chemical element in the Fe-Si soft magnetic materials with excellent performance in Examples 1-8 of the present invention and the comparative materials in Comparative Examples 1-3.

[0058] Table 1. (wt%, balance Fe and unavoidable impurities other than C, P, S and N)

[0059]

[0060] Table 2 lists the specific process parameters of the Fe-Si soft magnetic materials with excellent performance in Examples 1-8 of the present invention and the comparative materials in Comparative Examples 1-3.

[0061] Table 2.

[0062]

[0063] Samples were taken from the Fe-Si soft magnetic materials with excellent properties obtained in Examples 1-8 and the comparative materials of Comparative Examples 1-3, and their {001} were analyzed. <210> Orientation intensity of texture, iron loss P 10 / 600 The yield strength was tested, and the results are listed in Table 3. The specific testing methods are as follows:

[0064] Texture strength testing method: Texture testing can be performed using X-ray diffraction. 25mm (transverse TD) × 25mm (rolling direction RD) sheet samples are randomly cut from the finished strip. These samples are then polished to half the thickness of the strip for observation. The observation surface is the TD-RD plane, and the radiation source is CoKα rays. Three incomplete pole figures ({110}, {200}, and {211}) are measured using the Schulz back reflection method. Then, {001} is calculated. <210> Orientation intensity.

[0065] Iron loss P 10 / 600 The testing method is based on the square circle method of the standard "GB / T10129-2019 Measurement Method of Medium Frequency Magnetic Properties of Electrical Steel Strips (Sheets)".

[0066] The method for testing yield strength is based on the standard GB / T 228.1-2010 Metallic materials, tensile testing – Part 1: Test method at room temperature.

[0067] Table 3 lists the performance test results of the Fe-Si soft magnetic materials with excellent properties in Examples 1-8 of the present invention and the comparative materials in Comparative Examples 1-3.

[0068] Table 3.

[0069]

[0070]

[0071] As can be seen from Table 3 above, in Examples 1-8 of the present invention, the key parameters of alloy chemical composition control during the smelting process, heating rate in a specific range during the finished product annealing process, and holding temperature and time are all within the design range of the present invention, thus obtaining finished Fe-Si alloy strip {001}. <210> Orientation intensities are all greater than or equal to 2.0, and high-frequency iron loss P 10 / 600 All values ​​are less than 50 W / kg, and the yield strength is greater than or equal to 445 MPa, which can meet the requirements of high-speed rotation of the rotor core without the risk of fracture failure.

[0072] In contrast, although the manufacturing processes and finished product annealing processes of Comparative Examples 1 and 2 are within the scope of this invention, their chemical composition design is not within the scope of this invention. Therefore, the high-frequency iron loss and yield strength of the finished products are not within the scope of this invention.

[0073] Furthermore, although the chemical composition of Comparative Example 3 is within the scope of this invention, its heating rate, homogenization temperature, and holding time are not within the scope of this invention, resulting in a favorable texture for the finished strip {001}. <210> The strength is low, and the high-frequency iron loss of the material exceeds 45W / kg.

[0074] It should be noted that the scope of protection of the prior art in this invention is not limited to the embodiments given in this application. All prior art that does not contradict the solution of this invention, including but not limited to prior patent documents, prior publications, prior public uses, etc., can be included in the scope of protection of this invention.

[0075] Furthermore, the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0076] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A Fe-Si soft magnetic material with excellent properties, containing Fe and unavoidable impurities, characterized in that, It also contains the following chemical elements in the following mass percentages: Si: 2.8%-3.4%, Mn: 0.2-0.5%, Al: 0.2-0.8%, Ti: 0.0005-0.1%.

2. The Fe-Si soft magnetic material as described in claim 1, characterized in that, Its mass percentage content of each chemical element is as follows: Si: 2.8%-3.4%, Mn: 0.2-0.5%, Al: 0.2-0.8%, Ti: 0.0005-0.1%; The balance is Fe and unavoidable impurities.

3. The Fe-Si soft magnetic material as described in claim 1, characterized in that, The mass percentage of each chemical element also satisfies (Ti / 48+Al / 27) / (C / 12+N / 14)≥35.

4. The Fe-Si soft magnetic material as described in claim 1 or 2, characterized in that, It also contains at least one of the following: Sn: 0.01-0.15%; 0 < Mg ≤ 0.01%.

5. The Fe-Si soft magnetic material as described in claim 1 or 2, characterized in that, Among the unavoidable impurities, C ≤ 0.004%, P ≤ 0.02%, S ≤ 0.003%, and N ≤ 0.003%.

6. The Fe-Si soft magnetic material as described in claim 1 or 2, characterized in that, Its {001} <210> The orientation intensity of the texture is ≥2.

0.

7. The Fe-Si soft magnetic material as described in claim 1 or 2, characterized in that, Its iron loss P 10 / 600 ≤50W / kg.

8. The Fe-Si soft magnetic material as described in claim 1 or 2, characterized in that, Its yield strength is ≥445MPa.

9. A method for manufacturing Fe-Si soft magnetic material as described in any one of claims 1-8, characterized in that, Including the following steps: Smelting and casting; Hot-rolled; Annealing of hot-rolled steel sheet; Cold rolling; Finished product annealing: In the heating range of 630℃-820℃, the heating rate is controlled at 175℃ / s-300℃ / s; Apply an insulating coating.

10. The manufacturing method as described in claim 9, characterized in that, In the finished product annealing step: control the heat spread temperature to 820℃-900℃, and the heat spread holding time to 10s-20s.

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