A high saturation magnetic induction intensity iron-based nanocrystalline soft magnetic alloy and a preparation method thereof

Abstract

The present invention discloses a high saturation magnetic induction iron-based nanocrystalline soft magnetic alloy and a preparation method thereof. The composition of the alloy is represented by the chemical formula: FeaCubSicBdNbeBef, where a, b, c, d, e, f are atomic percentages and satisfy the following conditions: 78% ≤ a ≤ 84%, 0.5% ≤ b ≤ 2%, 1% ≤ c ≤ 6%, 10% ≤ d ≤ 18%, 0.1% ≤ e ≤ 0.5%, 0% < f ≤ 0.3%. By increasing the Fe content to more than 78%, the high Bs value of the alloy is fundamentally ensured. The saturation magnetic induction Bs of the as-quenched alloy of the present invention can reach more than 1.60 T, and can reach more than 1.70 T after secondary heat treatment, and can reach more than 1.80 T in the preferred scheme. Moreover, through the preparation method of melting the master alloy, rapidly quenching to obtain amorphous ribbons, continuously heat-treating the ribbons, winding the cores, and performing secondary heat treatment, the invention significantly improves the saturation magnetic induction of the alloy (Bs ≥ 1.60 T) by optimizing the Fe content and synergistically adding trace amounts of Be and Nb while ensuring good amorphous formation ability.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic materials technology, specifically to a high saturation magnetic induction intensity iron-based nanocrystalline soft magnetic alloy and its preparation method. Background Technology

[0002] Iron-based nanocrystalline soft magnetic alloys have been widely used in power transformers, new energy vehicle motors and other fields due to their excellent comprehensive properties such as high saturation magnetic induction (Bs), high magnetic permeability (μ) and low iron loss (Pc).

[0003] To achieve excellent soft magnetic properties, iron-based nanocrystalline alloys are typically prepared using a process of "amorphous precursor + crystallization treatment". A typical example is the Finemet type alloy (Fe-Cu-Nb-Si-B), which obtains a uniform crystalline structure at the nanoscale by adding Cu and Nb to the Fe-Si-B system. Cu acts as a nucleating agent to promote the precipitation of the α-Fe(Si) phase, while Nb inhibits grain growth.

[0004] However, there is a common contradiction in the existing technology: in order to improve the saturation magnetic induction intensity (Bs), the iron (Fe) content needs to be increased; but the increase of Fe content will reduce the amorphous forming ability of the alloy, which will make it easy to form crystalline phases when preparing amorphous ribbons, deteriorating the soft magnetic properties, especially increasing the coercivity (Hc); in addition, the traditional Nb element addition is usually high (about 1-3 at%), which can effectively inhibit grain growth, but because it is a non-magnetic element, too high content will dilute the concentration of magnetic atoms, which will limit the further improvement of Bs value.

[0005] Therefore, there is an urgent need in this field to develop a novel iron-based nanocrystalline alloy that can achieve higher saturation magnetic induction intensity while ensuring good amorphous forming ability and excellent soft magnetic properties (especially low coercivity). Summary of the Invention

[0006] The purpose of this invention is to provide a high-saturation magnetic induction intensity iron-based nanocrystalline soft magnetic alloy and its preparation method, so as to overcome the above-mentioned shortcomings in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A high-saturation magnetic induction intensity iron-based nanocrystalline soft magnetic alloy is disclosed. The alloy's composition is expressed by the chemical formula: FeaCubSicBdNbeBef, where a, b, c, d, e, and f are atomic percentages and satisfy the following conditions: 78%≤a≤84%, 0.5%≤b≤2%, 1%≤c≤6%, 10%≤d≤18%, 0.1%≤e≤0.5%, 0%≤f≤0.5%. <f≤0.3%。

[0009] Preferably, 'a' satisfies 80% ≤ a ≤ 84%.

[0010] Preferably, f satisfies 0.1% ≤ f ≤ 0.3%.

[0011] Preferably, c and d satisfy 15% ≤ c + d ≤ 20%.

[0012] A method for preparing a high-saturation magnetic induction intensity iron-based nanocrystalline soft magnetic alloy, comprising the following steps:

[0013] S1: Master alloy smelting, the raw materials are batched according to the composition of the alloy, the batched raw materials are smelted to form a uniform molten steel, and then cast to obtain a master alloy ingot.

[0014] S2: Amorphous ribbon preparation: The master alloy ingot is remelted and spun into a strip using a single-roll quenching method to obtain a quenched alloy ribbon.

[0015] S3: Initial heat treatment, the quenched strip obtained in step S2 is subjected to initial nanocrystallization heat treatment in a continuous heat treatment furnace;

[0016] S4: Secondary heat treatment. The strip obtained in step S3 is wound into an iron core and placed in a vacuum or protective atmosphere heat treatment furnace for secondary heat treatment.

[0017] Preferably, in step S3, the continuous heat treatment is a tension continuous heat treatment, and it is carried out under a protective atmosphere.

[0018] Preferably, in step S4, the secondary heat treatment is a segmented isothermal heat treatment.

[0019] Preferably, in step S4, the secondary heat treatment is a magnetic field isothermal heat treatment.

[0020] Preferably, in step S2, the thickness of the amorphous ribbon is 18-30 μm.

[0021] In the above technical solution, the beneficial effects of the high saturation magnetic induction intensity iron-based nanocrystalline soft magnetic alloy and its preparation method provided by the present invention are as follows:

[0022] 1. By increasing the Fe content to over 78%, this invention fundamentally ensures that the alloy has a high Bs value. The saturation magnetic induction intensity Bs of the quenched alloy of this invention can reach over 1.60 T, and can reach over 1.70 T after secondary heat treatment. The preferred scheme can reach over 1.80 T.

[0023] 2. This invention employs a strategy of adding Nb and Be in extremely low amounts. Nb primarily inhibits grain growth and is added in trace amounts of 0.1% ≤ e ≤ 0.5%. This prevents both excessive dilution of the magnetic atom concentration and abnormal grain growth during initial nanocrystallization. The addition of small-atom-sized Be improves the amorphous forming ability of the alloy, enabling the successful preparation of amorphous ribbons with minimal quenched nanocrystal volume content even with high Fe content. Furthermore, Be can form intermetallic compounds with impurity Co, becoming nucleation sites, increasing the nucleation rate, and easily accumulating at grain boundaries, thus inhibiting grain growth. This synergistic effect with Nb further refines the nanocrystals, resulting in a more uniform nanocrystalline structure.

[0024] 3. The present invention uses relatively low Si and B contents, which facilitates further increase of Fe content in the alloy. It is preferred to keep the Si and B contents at 15%≤c+d≤20% to ensure suitable amorphous formation capability. The Cu content is the key to forming a large number of Cu atom clusters and providing nucleation cores. The content is comparable to that of traditional nanocrystals.

[0025] 4. This invention employs a two-step method of "initial heat treatment of the strip + secondary heat treatment of the iron core". The initial tension continuous heat treatment ensures that the strip has a flat shape and uniform performance during the nanocrystallization process. Furthermore, the strip heating rate exceeding 50°C / min can be ensured by adjusting the strip speed and heat treatment temperature, thereby suppressing the aggregation of Cu atom clusters during the heating process, providing more nucleation sites, and forming more and finer initial nanocrystals. The secondary heat treatment can effectively eliminate winding stress, obtain a higher volume fraction of nanocrystalline phase, improve the saturation magnetic induction intensity of the alloy, and induce magnetic anisotropy through magnetic field heat treatment, further reducing the high-frequency loss of the iron core and other properties. This process is stable, controllable, and suitable for industrial production.

[0026] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit this disclosure.

[0027] This application provides an overview of various implementations or examples of the technology described in this disclosure, and is not a full disclosure of the entire scope or all features of the disclosed technology. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0029] Figure 1The XRD patterns of the amorphous ribbon on the roller surface and the free surface are provided in the embodiments of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0031] A high-saturation magnetic induction intensity iron-based nanocrystalline soft magnetic alloy is disclosed. The alloy's composition is expressed by the chemical formula: FeaCubSicBdNbeBef, where a, b, c, d, e, and f are atomic percentages and satisfy the following conditions: 78%≤a≤84%, 0.5%≤b≤2%, 1%≤c≤6%, 10%≤d≤18%, 0.1%≤e≤0.5%, 0%≤f≤0.5%. <f≤0.3%。

[0032] Furthermore, a satisfies 80%≤a≤84%. By increasing the Fe content to over 78%, the alloy is guaranteed to have a high Bs value, enabling its magnetic induction intensity Bs to reach over 1.60 T. Moreover, when the Fe content reaches 80%-82%, it can reach over 1.80 T.

[0033] Furthermore, f satisfies 0.1%≤f≤0.3%.

[0034] Furthermore, c and d satisfy 15%≤c+d≤20%.

[0035] Nb plays a role in inhibiting grain growth. By adding trace amounts, it prevents excessive dilution of the magnetic atom concentration and abnormal grain growth during initial nanocrystallization. The small atomic size of Be is beneficial to improving the amorphous forming ability of the alloy. It also enables the successful preparation of amorphous ribbons with minimal quenched nanocrystal volume content even with high Fe content. Furthermore, Be can form intermetallic compounds with impurity Co, becoming nucleation cores, increasing the nucleation rate, and easily aggregating at grain boundaries, inhibiting grain growth. This creates a synergistic effect with Nb, which can more effectively refine nanocrystals and obtain a more uniform nanocrystalline structure. Through this "high Fe + trace Nb / Be" approach, the contradiction between high Bs and good amorphous forming ability and fine grain structure is balanced. This invention achieves high Bs while also having low coercivity (Hc < 10 A / m), exhibiting excellent comprehensive performance.

[0036] In this invention, the values ​​of a, b, c, d, e, and f are any values ​​within their respective ranges, and are not limited to the integers or specific patterns selected in the usual experimental verification of ingredients.

[0037] A method for preparing a high-saturation magnetic induction intensity iron-based nanocrystalline soft magnetic alloy, comprising the following steps:

[0038] S1: Master alloy smelting, the raw materials are batched according to the composition of the alloy, the batched raw materials are smelted to form a uniform molten steel, and then cast to obtain a master alloy ingot.

[0039] S2: Amorphous ribbon preparation: The master alloy ingot is remelted and spun into a strip using a single-roll quenching method to obtain a quenched alloy ribbon.

[0040] S3: Initial heat treatment, the quenched strip obtained in step S2 is subjected to initial nanocrystallization heat treatment in a continuous heat treatment furnace;

[0041] S4: Secondary heat treatment. The strip obtained in step S3 is wound into an iron core and placed in a vacuum or protective atmosphere heat treatment furnace for secondary heat treatment.

[0042] In step S3, the continuous heat treatment is a tension continuous heat treatment, and it is carried out under a protective atmosphere.

[0043] In step S4, the secondary heat treatment is a segmented isothermal heat treatment.

[0044] In step S4, the secondary heat treatment is a magnetic field isothermal heat treatment.

[0045] In step S2, the thickness of the amorphous ribbon is 18-30 μm.

[0046] Master alloy smelting: The raw materials are batched according to the composition formula of the iron-based nanocrystalline alloy. High-purity raw materials can be selected for batching, preferably industrial-purity raw materials. B and Be can be transitioned using FeB and BeCu alloys. Inevitably, impurities such as Co, Ni, P, C, and S will be introduced into the batching, with a total content of less than 0.1%. The batched raw materials are smelted in an induction melting furnace or an electric arc melting furnace, preferably under vacuum or a protective atmosphere, to form a uniform molten steel, which is then cast to obtain the master alloy ingot.

[0047] Amorphous ribbon preparation: The master alloy ingot is remelted and spun into a strip using a single-roll quenching method to obtain a quenched alloy ribbon. Depending on the alloy composition and preparation process parameters, the quenched alloy ribbon is either completely amorphous or has a small amount of initial nanocrystals. The preferred ribbon thickness is 18-30 μm.

[0048] Primary heat treatment: The quenched alloy strip is subjected to initial nanocrystallization heat treatment in a continuous heat treatment furnace, preferably tension continuous heat treatment, and carried out under a protective atmosphere. The furnace temperature is between the crystallization temperature Tx1 and Tx2 of the alloy. The time for the strip to pass through the furnace is 2-15s, and the tension is 1MPa-22MPa. The application of tension may induce certain anisotropy. Furthermore, the main purpose of the primary heat treatment is to generate a large number of initial refined nanocrystalline phases in the quenched strip through rapid heat treatment.

[0049] Secondary heat treatment: The strip obtained after the primary heat treatment is wound into an iron core and placed in a vacuum or protective atmosphere heat treatment furnace for secondary heat treatment. The purpose of secondary heat treatment is mainly to remove the stress generated during the winding of the strip into the iron core, and to further increase the volume fraction of the nanocrystalline phase through the controllable growth of nanocrystals. Therefore, the maximum holding temperature should be lower than the Tx1 temperature. One-stage isothermal heat treatment can be selected, but segmented isothermal heat treatment is better, as the stress relief effect is more significant. According to the performance requirements of the magnetic core, longitudinal or transverse magnetic field heat treatment can also be applied.

[0050] Regarding the embodiments of the present invention;

[0051] Master alloy smelting: Industrial purity raw materials are used according to the composition ratio, with Be using BeCu alloy as a transition material. Inevitably, impurities such as Co, Ni, P, C, and S are introduced into the raw materials, with a total content of less than 0.1%. The materials are smelted in a vacuum induction melting furnace to ensure uniform composition, and then cast to obtain master alloy ingots.

[0052] Amorphous ribbon preparation: The master alloy ingot is crushed and spun in a single-roll quenching method with a roller surface linear speed of about 35 m / s to obtain an amorphous alloy ribbon with a width of about 35 mm and a thickness of about 25 μm.

[0053] Initial heat treatment: The amorphous ribbon is treated in a continuous tension heat treatment furnace with high-purity nitrogen gas. The heat treatment temperature is 460℃, the ribbon passes through the furnace for 10s, and a tension of 1MPa is applied.

[0054] Secondary heat treatment: The strip after the initial heat treatment is wound into a ring-shaped iron core with an inner diameter of 20mm, an outer diameter of 30mm, and a height of 35mm. The core is then placed in a vacuum heat treatment furnace for segmented isothermal heat treatment. First, the temperature is increased to 300℃ at a rate of 5℃ / min and held for 30 minutes. Then, the temperature is increased to 400℃ at a rate of 3℃ / min and held for 60 minutes. The core is then cooled to room temperature in the furnace.

[0055] Examples 1-6 were all prepared using the alloy preparation process described above. The difference between Examples 1-6 lies in the different raw material composition ratios. The specific composition ratios, DC magnetic properties, and crystallization temperatures of each example are described in Table 1.

[0056] Regarding the comparative example:

[0057] Comparative Example 1 is a conventional 1K107B nanocrystalline alloy, which is subjected to segmented heat treatment. First, the temperature is raised to 480℃ at 10℃ / min and held for 30 minutes; then the temperature is raised to 540℃ at 3℃ / min and held for 60 minutes, and then cooled to room temperature in the furnace.

[0058] Furthermore, the composition ratio of Comparative Example 1, as well as its DC magnetic properties and crystallization temperature, are also described in Table 1.

[0059] serial number Composition (at%) Bs(T) Hc (A / m) Tx1 (°C) Tx2 (°C) ΔTx Example 1 Fe80.4Cu1Si4B14Nb0.3Be0.3 1.82 8.0 420 512 92 Example 2 Fe80.4Cu1Si4B14Nb0.5Be0.1 1.78 7.2 432 514 82 Example 3 Fe80.75Cu1Si4B14Nb0.1Be0.15 1.73 8.3 422 508 86 Example 4 Fe81.1Cu1.5Si2B15Nb0.2Be0.2 1.79 9.1 423 516 93 Example 5 Fe78.6Cu1Si6B14Nb0.2Be0.2 1.65 12.4 430 515 85 Example 6 Fe83.6Cu1Si5B10Nb0.2Be0.2 1.80 25.5 401 490 89 Comparative Example 1 Fe73.5Cu1Nb3Si15.5B7 1.24 0.9 515 565 50

[0060] Table 1 (Comparison of DC magnetic properties and crystallization temperature of embodiments and comparative examples of the present invention)

[0061] The above comparison shows that, compared with traditional nanocrystalline alloys, the iron-based nanocrystalline alloy of this invention has a very high saturation magnetic induction intensity and maintains a relatively low coercivity, resulting in good overall magnetic properties. Thermodynamically, the iron-based nanocrystalline alloy of this invention has a relatively low crystallization temperature and a wider crystallization temperature range, and good controllability in heat treatment.

[0062] Instruction manual attached Figure 1 The XRD pattern of Example 1 in the quenched state is given. It can be seen that the alloy has good amorphous formation ability. Both the iron rod surface and the free surface have not obvious sharp peaks near 2θ of 44°, indicating that there may be some initial nanocrystallization in the quenched strip.

[0063] Table 2 lists the magnetic performance data of Example 1 under different conditions. The experimental steps are as follows:

[0064] 1. The quenched strip is wound into a toroidal core with an inner diameter of 20mm, an outer diameter of 30mm, and a height of 35mm, and then tested.

[0065] 2. The quenched strip was subjected to initial heat treatment in a continuous tension heat treatment furnace filled with high-purity nitrogen. The heat treatment temperature was 460℃, the strip passed through the furnace for 10 seconds, and a tension of 1MPa was applied. The treated strip was then wound into a toroidal core with an inner diameter of 20mm, an outer diameter of 30mm, and a height of 35mm, and then tested.

[0066] 3. Perform ordinary segmented isothermal heat treatment on some of the iron cores obtained in step 2: first, heat to 300℃ at 5℃ / min and hold for 30 minutes; then heat to 400℃ at 3℃ / min and hold for 60 minutes; then cool to room temperature with the furnace; perform segmented isothermal heat treatment with transverse magnetic field on some of the iron cores: first, heat to 300℃ at 5℃ / min and hold for 30 minutes; then heat to 400℃ at 3℃ / min and hold for 60 minutes, applying a transverse magnetic field of 100A / m during the holding process, and after the holding is completed, turn off the magnetic field and cool to room temperature with the furnace.

[0067] Alloy heat treatment state Bs (T) Hc (A / m) Quenched state 1.62 55.3 Primary heat treatment 1.75 21.8 Primary heat treatment + secondary ordinary segmented heat treatment 1.82 8.0 Primary heat treatment + secondary transverse magnetic segmented heat treatment 1.83 7.8

[0068] Table 2 (Comparison of magnetic core performance between the examples and the comparative examples)

[0069] The results show that through secondary heat treatment, the saturation magnetic induction of the iron-based nanocrystalline alloy will be further increased, the coercivity will be decreased, and the overall magnetic properties will be further optimized.

[0070] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A high saturation magnetic induction iron-based nanocrystalline soft magnetic alloy, characterized by, The composition of this alloy is expressed by the chemical formula: FeaCubSicBdNbeBef, where a, b, c, d, e, and f are atomic percentages and satisfy the following conditions: 80%≤a≤84%, 0.5%≤b≤2%, 1%≤c≤6%, 10%≤d≤18%, 0.1%≤e≤0.5%, 0.1%≤f≤0.5%. <f≤0.3%; The values ​​of c and d satisfy 15% ≤ c + d ≤ 20%.

2. A method for producing a high saturation magnetic induction iron-based nanocrystalline soft magnetic alloy for producing the high saturation magnetic induction iron-based nanocrystalline soft magnetic alloy according to claim 1, characterized by, Includes the following steps: S1: Master alloy smelting, the raw materials are batched according to the composition of the alloy, the batched raw materials are smelted to form a uniform molten steel, and then cast to obtain a master alloy ingot. S2: Amorphous ribbon preparation: The master alloy ingot is remelted and spun into a strip using a single-roll quenching method to obtain a quenched alloy ribbon. S3: Initial heat treatment, the quenched strip obtained in step S2 is subjected to initial nanocrystallization heat treatment in a continuous heat treatment furnace; S4: Secondary heat treatment. The strip obtained in step S3 is wound into an iron core and placed in a vacuum or protective atmosphere heat treatment furnace for secondary heat treatment.

3. The method of claim 2, wherein the soft magnetic alloy has a saturation magnetic flux density of 1.8 T or more. In step S3, the continuous heat treatment is a tension continuous heat treatment, and it is carried out under a protective atmosphere.

4. The method of claim 2, wherein the soft magnetic alloy has a saturation magnetic flux density of 1.8 T or more. In step S4, the secondary heat treatment is a segmented isothermal heat treatment.

5. The method of claim 2, wherein the soft magnetic alloy has a saturation magnetic flux density of 1.8 T or more. In step S4, the secondary heat treatment is a magnetic field isothermal heat treatment.

6. The method of claim 2, wherein the soft magnetic alloy has a saturation magnetic flux density of 1.8 T or more. In step S2, the thickness of the amorphous ribbon is 18-30 μm.

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