High-saturation magnetic induction iron-based nanocrystalline alloy and magnetic performance optimization preparation method thereof

Abstract

The invention discloses a high-saturation magnetic induction iron-based nanocrystalline alloy and a magnetic performance optimization preparation method thereof, and relates to the technical field of iron-based nanocrystalline alloy materials. The method comprises the following steps: preparing materials according to atomic percent: 50-90% of Fe, 1-40% of Co, 1-10% of Ni, 1-20% of B, 0.1-5% of Cu and 0.1-5% of Si, putting the materials into a quartz tube, putting the quartz tube into a heating coil of a smelting furnace, introducing argon in a vacuum environment for smelting, crushing an obtained master alloy ingot into small blocks, polishing impurities and oxides on the surface, melting, and preparing a continuous iron-based amorphous alloy strip by adopting a rapid quenching method, and after cutting, a product is prepared by adopting a two-step annealing process of stress relief annealing and crystallization annealing in a longitudinal magnetic field. According to the invention, the iron-based nanocrystalline alloy with high saturation flux density and low coercive force can be obtained at lower cost by adopting an easy-to-control method.

Description

Technical Field

[0001] The present invention relates to the field of iron-based nanocrystalline alloy materials, in particular to a high-saturation magnetic induction iron-based nanocrystalline alloy and a method for optimizing its magnetic properties. Background Art

[0002] Energy shortages and environmental pollution have become major challenges hindering human survival and development, and developing a green and low-carbon economy has become a common concern worldwide. As an important energy material, the development of soft magnetic alloys plays a crucial role in minimizing wasteful energy dissipation. Among them, iron-based amorphous / nanocrystalline alloys offer significant development potential in high-frequency transformers and motors due to their superior soft magnetic properties, including high saturation magnetic induction, low coercivity, high effective permeability, and low losses. However, compared to traditional silicon steel, the saturation magnetic induction of currently commercially available iron-based nanocrystalline alloys remains relatively low, lacking a clear advantage in high-frequency technology. Furthermore, the addition of large amounts of iron to the alloy reduces the content of other elements, degrading the glass-forming ability and overall performance of iron-based amorphous / nanocrystalline alloys. Therefore, exploring new approaches to enhance the comprehensive magnetic and mechanical properties of iron-based amorphous / nanocrystalline alloys through alloy composition manipulation and process optimization is imperative.

[0003] Currently, researchers have conducted a series of studies on the optimization design of the comprehensive magnetic properties of iron-based nanocrystalline alloy strips and applied for a number of national invention patents, including:

[0004] The Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, disclosed a high-magnetic-induction, high-frequency iron-based nanocrystal and its preparation method in patent CN110387500A. The composition of the nanocrystal is FeSiBPNbVMoCu. The amorphous strip is prepared by rapid quenching and cooling-copper roller stripping method. The nanocrystalline alloy strip is annealed at 500-600 ° C and kept warm for 10 minutes. The saturation magnetic induction intensity of the alloy composition is 1.41-1.45 T and the coercive force is 2.3 A / m.

[0005] Guilin University of Electronic Technology disclosed a crystallization-controllable iron-based nanocrystalline soft magnetic alloy and its preparation method in patent CN110541116A. The chemical composition of the alloy is FeSiBCuP. After crystallization treatment, the saturation magnetic induction of the alloy can reach 1.57-1.85T, but the high volatility of the P element makes its preparation process difficult.

[0006] Guangdong University of Technology, in patent CN109112434A, discloses a novel iron-based amorphous nanocrystalline soft magnetic alloy and its preparation method. The paper states that heating the strip to 410-450°C at a rate of 10-20°C / min and then cooling it to room temperature can produce a high saturation magnetic flux density and low coercivity. The alloy also exhibits good bending toughness. However, the complex alloy system containing precious metal elements is not conducive to commercial strip production.

[0007] Although existing research has improved the soft magnetic properties of iron-based nanocrystalline alloy ribbons, the heat treatment process is demanding, and the overall magnetic properties (such as the balance between saturation magnetic induction and coercivity) are not optimal. Furthermore, to improve performance, researchers have added precious metals to the alloy composition, resulting in higher alloy costs. Furthermore, the addition of volatile elements such as phosphorus makes precise processing difficult, hindering industrial development and large-scale application. Summary of the Invention

[0008] The purpose of the present invention is to provide a high saturation magnetic induction iron-based nanocrystalline alloy and a method for optimizing its magnetic properties, so as to obtain an iron-based nanocrystalline alloy with high saturation magnetic induction intensity and low coercivity at a relatively low cost and by adopting an easily controllable method.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for optimizing the magnetic properties of a high saturation magnetic induction iron-based nanocrystalline alloy, comprising the following:

[0010] S1, based on the alloy molecular formula Fe a Co b Ni c B d Cu e Si f Ratio of raw materials, where a, b, c, d, e, and f represent the atomic percentage of the corresponding components, and satisfy the following conditions: 50≤a≤90, 1≤b≤40, 1≤c≤10, 1≤d≤20, 0.1≤e≤5, 0.1≤f≤5, and a+b+c+d+e+f=100;

[0011] S2. Put the proportioned raw materials into a quartz tube and place it in the heating coil of a smelting furnace. Put B, Ni, Cu, and Si into the bottom of the quartz tube and cover it with Fe and Co. Then, introduce argon gas into a vacuum environment for smelting. After melting, keep the temperature for a period of time. After the smelting is completed, cool it to obtain a master alloy ingot.

[0012] S3, crushing the master alloy ingot obtained in S2 into small pieces and polishing the impurities and oxides on the surface, placing the polished alloy block in a quartz tube, evacuating the quartz tube and introducing a protective gas; adjusting the rotation speed of the copper roller and the pressure difference between the inside and outside of the quartz tube; heating until the alloy block melts and turns bright red and rolls in the quartz tube, causing the solution to be rapidly sprayed along the nozzle at the bottom of the quartz tube onto the surface of the rapidly rotating copper roller due to the pressure difference, thereby rapidly solidifying to produce a continuous iron-based amorphous alloy strip;

[0013] S4. Cut the iron-based amorphous alloy strip obtained in S3 into suitable sizes, place the cut samples in a heat treatment device, and perform a two-step annealing process of stress relief annealing + crystallization annealing in a high vacuum state and a longitudinal magnetic field. Water quenching is performed immediately after each annealing. The stress relief annealing temperature is 250-300°C and the holding time is 5-30 min. The crystallization annealing temperature is 350-500°C and the holding time is 1-15 min.

[0014] Preferably, in step S2, the vacuum degree of the vacuum environment is 3×10 -3 Pa, the melting temperature is 1300-1500℃, keep warm for 5-30 minutes after melting, and cool for 5-30 minutes after melting.

[0015] Preferably, in step S3, the vacuum degree is 3×10 -3 Pa, the protective gas is argon, and the pressure difference between the inside and outside of the quartz tube is 0.01-0.03 Pa.

[0016] Preferably, in step S3, the length of the obtained iron-based amorphous alloy strip is 0.5-5 m, the width is 0.8-1.5 mm, and the thickness is 15-25 um.

[0017] Preferably, in step S4, the magnetic field strength of the longitudinal magnetic field is 0.05-0.1 T.

[0018] Preferably, in step S4, the temperature of the crystallization annealing is 360-400°C.

[0019] Another technical solution provided by the present invention is: a high saturation magnetic induction iron-based nanocrystalline alloy, which is prepared by the above preparation method.

[0020] Preferably, the saturation magnetic induction intensity of the iron-based nanocrystalline alloy can reach 1.80-1.91 T, and the coercive force can reach 0.5-10 A / m.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a high-saturation magnetic induction iron-based nanocrystalline alloy and a method for preparing the same with optimized magnetic properties. By optimizing the composition design of the iron-based nanocrystalline alloy, the iron-based amorphous alloy is alloyed. In a longitudinal magnetic field, the iron-based amorphous strip is subjected to a two-step annealing method of stress relief annealing + crystallization annealing. This method not only significantly reduces the coercive force of the strip but also further improves the saturation magnetic induction intensity of the strip by precipitating fine nanocrystals. No precious metals are required, which can effectively control costs, and no volatile elements that are difficult to control are added. This method provides a high-performance material foundation for energy-saving design in fields such as high-frequency transformers and high-efficiency motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The XRD patterns of the quenched amorphous ribbons prepared in Examples 1, 2, and 3 of the present invention are shown;

[0024] Figure 2 The DSC curves of the quenched amorphous ribbons prepared in Examples 1, 2, and 3 of the present invention are shown;

[0025] Figure 3 This is a flow chart of the heat treatment process of the embodiment of the present invention and the comparative example;

[0026] Figure 4 The microstructure organization diagram and grain size statistical diagram of Example 1 of the present invention and the comparative example under optimal heat treatment conditions. DETAILED DESCRIPTION

[0027] A method for optimizing the magnetic properties of a high-saturation magnetic induction iron-based nanocrystalline alloy comprises the following steps:

[0028] S1, based on the alloy molecular formula Fe a Co b Ni c B d Cu e Si f Ratio of raw materials, where a, b, c, d, e, and f represent the atomic percentage of the corresponding components, and satisfy the following conditions: 50≤a≤90, 1≤b≤40, 1≤c≤10, 1≤d≤20, 0.1≤e≤5, 0.1≤f≤5, and a+b+c+d+e+f=100;

[0029] S2. Put the proportioned raw materials into a quartz tube and place it in the heating coil of a smelting furnace. Put B, Ni, Cu, and Si into the bottom of the quartz tube and cover it with Fe and Co. Then, introduce argon gas into a vacuum environment for smelting. After melting, keep the temperature for a period of time. After the smelting is completed, cool it to obtain a master alloy ingot.

[0030] In a preferred embodiment, the vacuum degree of the vacuum environment is 3×10 -3Pa, the melting temperature is 1300-1500℃, keep warm for 5-30 minutes after melting, and cool for 5-30 minutes after melting.

[0031] S3, crushing the master alloy ingot obtained in S2 into small pieces and polishing the impurities and oxides on the surface, placing the polished alloy block in a quartz tube, evacuating the quartz tube and introducing a protective gas; adjusting the rotation speed of the copper roller and the pressure difference between the inside and outside of the quartz tube; heating until the alloy block melts and turns bright red and rolls in the quartz tube, so that the solution is rapidly sprayed along the nozzle at the bottom of the quartz tube onto the surface of the rapidly rotating copper roller by virtue of the pressure difference, thereby rapidly solidifying to obtain a continuous iron-based amorphous alloy strip. For reference, the obtained iron-based amorphous alloy strip can be 0.5-5 m in length, 0.8-1.5 mm in width, and 15-25 um in thickness;

[0032] In a preferred embodiment, the vacuum degree is 3×10 -3 Pa, the protective gas is argon, and the pressure difference between the inside and outside of the quartz tube is 0.01-0.03 Pa;

[0033] S4. Cut the iron-based amorphous alloy strip obtained in S3 into a suitable size, place the cut sample in a heat treatment device, and perform a two-step annealing process of stress relief annealing + crystallization annealing in a high vacuum state and a longitudinal magnetic field. Water quenching is performed immediately after each annealing, wherein the temperature of stress relief annealing is 250-300°C, the holding time is 5-30 min, the temperature of crystallization annealing is 350-500°C, and the holding time is 1-15 min. Further preferably, the temperature of crystallization annealing is 360-400°C. Lower coercive force performance can be obtained within this range.

[0034] In a preferred embodiment, the magnetic field strength of the longitudinal magnetic field is 0.05-0.1 T.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings, embodiments and comparative examples.

[0036] The smelting furnaces in the following examples and comparative examples all adopted the Beijing Wuke WK-II vacuum belt spinning equipment.

[0037] Example 1:

[0038] S1, based on the alloy molecular formula Fe 67.2 Co 16.8 Ni2B 12.5 Cu1Si 0.5 Proportioning of raw materials;

[0039] S2. Clean the interior of the smelting furnace and place the raw materials in a clean quartz tube. The raw materials with less mass, such as B particles, are placed at the bottom, and the top is covered with Fe and Co. Fix the quartz tube in the middle of the induction coil and evacuate it. First, use a mechanical pump to evacuate the low vacuum to 3 Pa, and then use a diffusion pump to evacuate the high vacuum to 3×10 -3 Pa. Once the required vacuum is reached, introduce an appropriate amount of argon into the melting furnace. Turn on the current switch and begin increasing the current intensity at a constant rate. Once the alloy is evenly melted, hold the temperature for 15 minutes, then uniformly reduce the current intensity to 0. After cooling for 20 minutes, remove the master alloy ingot and weigh it, ensuring the error with the raw materials does not exceed 0.5%.

[0040] S3. Crush the smelted master alloy ingot into small pieces and polish the surface impurities and oxides, then clean it with alcohol. Place the cleaned alloy block in the quartz tube and fix it in the middle of the induction coil. Adjust the distance between the nozzle at the bottom of the quartz tube and the copper roller to 1-2 mm. Open the high vacuum manual baffle valve to pump the low vacuum to 5 Pa. Open the isolation solenoid valve and the ultra-high vacuum baffle valve to pump the high vacuum to 3×10 -3 Pa. Once the vacuum reaches the required level, the valve is closed and an appropriate amount of argon is introduced to adjust the internal and external pressure differential to 0.025 Pa. The copper roller speed is then adjusted to 8000 r / min. Once the copper roller speed stabilizes, the current switch is turned on to begin heating. Once the alloy block melts, turns bright red, and tumbles within the quartz tube, the injection button is pressed. This pressure differential causes the solution to be rapidly injected through a 1 mm diameter nozzle at the bottom of the quartz tube onto the rapidly rotating copper roller surface, resulting in rapid solidification and amorphous alloy ribbon. The resulting amorphous alloy ribbon has a width of 1 ± 0.1 mm and a thickness of 20 ± 2 μm.

[0041] S4. Cut the amorphous alloy strip produced in the experiment into 50 mm lengths and place it in the quartz tube of an annealing furnace. Apply a longitudinal magnetic field with an intensity of 0.08 T. After the annealing furnace temperature stabilizes at 280°C, place the quartz tube in the annealing furnace and hold it there for 10 minutes. Immediately after the holding period, remove the tube and water quench it. After the annealing furnace temperature is set and stabilized at 400°C, place the annealed sample in the quartz tube and hold it in the annealing furnace for 5 minutes. Immediately after the holding period, water quench it. The amorphous alloy strip is kept in a high vacuum during the heat treatment process.

[0042] Example 2:

[0043] The only difference from Example 1 is that in step S1, the raw materials are proportioned according to the alloy molecular formula Fe 75.6 Co 8.4 Ni2B 12.5 Cu1Si 0.5 The rest of the preparation method and heat treatment process are the same as those in Example 1.

[0044] Example 3:

[0045] The only difference from Example 1 is that in step S1, the raw materials are proportioned according to the alloy molecular formula Fe 79.8 Co 4.2 Ni2B 12.5 Cu1Si 0.5 The rest of the preparation method and heat treatment process are the same as those in Example 1.

[0046] Comparative Example:

[0047] This comparative example differs from Example 1 in that the heat treatment process in this comparative example is as follows: the amorphous alloy strip produced in the experiment was cut into 50 mm lengths and placed in a quartz tube in an annealing furnace. After the annealing furnace temperature stabilized at 400°C, the amorphous alloy strip was placed in the quartz tube and held in the annealing furnace for 5 minutes. Water quenching was performed immediately after the holding period. The amorphous alloy strip was kept in a high vacuum during the heat treatment process.

[0048] Figure 1 The XRD patterns of the quenched amorphous ribbons prepared in Examples 1, 2, and 3 of the present invention are shown. XRD measurements were performed using a polycrystal X-ray diffractometer. As can be seen, the XRD patterns of these examples all exhibit a diffuse scattering peak, with no distinct crystallization diffraction peaks, a characteristic characteristic of a typical amorphous structure.

[0049] Figure 2 The following are DSC graphs of the quenched amorphous ribbons prepared in Examples 1, 2, and 3 of the present invention. The DSC curves were measured using a NETZSCH DSC 404C differential scanning calorimeter with a heating rate of 0.67°C / s. The DSC curves show that the crystallization heat treatment window ΔT (ΔT = T x2 -T x1 ) is 143°C. This ΔT is the optimal heat treatment temperature range for obtaining the nanocrystalline structure required for excellent soft magnetic alloys.

[0050] Figure 3 The flowchart of the heat treatment process of the embodiment of the present invention and the comparative example. Compared with the comparative example, the embodiment adds a stress relief annealing process before the crystallization annealing, and adds a longitudinal magnetic field during the entire heat treatment process, which not only reduces the internal stress of the amorphous alloy strip due to rapid solidification, but also inhibits the growth of grains in the subsequent crystallization process. Among them, the selection range of T1 is T x1 The temperature around -100°C ensures that the amorphous alloy strip can eliminate internal stress and prevent the precipitation of nano-crystals during stress relief annealing. T2 is between the initial crystallization temperature and the second crystallization temperature to meet the precipitation of single α-Fe nanocrystals.

[0051] Table 1 below lists the coercivity data for examples and comparative examples of the present invention subjected to different crystallization annealing temperatures. As the heat treatment temperature increases, the coercivity of the examples decreases and then increases, reaching a minimum value (0.8-1 A / m) at 380°C. Within the crystallization temperature window, the coercivity of the comparative examples increases significantly relative to the quenched amorphous alloy, indicating that traditional heat treatment methods are ineffective in improving the coercivity of these alloys.

[0052] Table 1 Coercivity data under different crystallization annealing temperature heat treatment conditions

[0053]

[0054] Table 2 below lists the saturation magnetic induction (B) of the embodiments of the present invention and the comparative examples under different temperature crystallization annealing heat treatment conditions. s ). As can be seen from the table, the saturation magnetic flux density of the examples and comparative examples generally increases with increasing heat treatment temperature. This is because high temperatures promote the precipitation of α-Fe nanocrystals in the amorphous alloy ribbon. The decrease in saturation magnetic flux density in Example 1 during annealing at 460°C is due to the precipitation of hard magnetic phases such as Fe-B in the amorphous ribbon, which deteriorates its soft magnetic properties. Compared to the comparative example, the saturation magnetic flux density of Example 1 increases slightly.

[0055] Table 2 Saturation magnetic induction data under different crystallization annealing temperature heat treatment conditions

[0056]

[0057] Considering the two magnetic properties of saturation magnetic induction intensity and coercive force, the iron-based nanocrystalline alloy prepared at a crystallization annealing temperature of 400°C has the best comprehensive magnetic properties. The saturation magnetic induction intensity of the iron-based nanocrystalline alloy can reach 1.80-1.91 T, and the coercive force can reach 0.5-10 A / m. The performance of Example 1 is the best.

[0058] In addition, the present invention also controlled the variables to conduct a large number of raw material ratio adjustment tests, heat treatment time tests, and magnetic field intensity adjustment tests. 50～90 Co 1～40 Ni 1～10 B 1～20 Cu 0.1～5 Si 0.1～5The coercive force can be maintained at 0.5-10 A / m, and the saturation magnetic induction intensity is between 1.70-1.90 T under the conditions of stress relief annealing temperature of 250-300°C, holding time of 5-30 min, crystallization annealing temperature of 360-400°C, holding time of 1-15 min, and magnetic field strength of 0.05-0.1 T. Under any conditions, the iron-based nanocrystalline alloy obtained at a crystallization annealing temperature of 400°C has the best comprehensive magnetic properties.

[0059] In summary, compared with the traditional annealing process, the two-step magnetic field annealing process of stress relief annealing + crystallization annealing adopted in the present invention can significantly improve the soft magnetic properties of amorphous strips, and is an effective and feasible method for regulating the magnetic properties of amorphous alloys.

[0060] Figure 4 The microstructure organization diagram and grain size statistics diagram of Example 1 of the present invention and the comparative example under the optimal heat treatment conditions. It can be seen from the figure that the grain size of Example 1 is significantly smaller than that of the comparative example. The grain size statistics of the two are obtained, and it is found that the average grain size of Example 1 is 20.2 nm, and the average grain size of the comparative example is 40.4 nm. The large grain size is the reason for the deterioration of the coercive force of the comparative example. Therefore, the results show that after the alloy is treated with appropriate time and temperature after the magnetic field assists in stress relief, the number and size of nanocrystals precipitated from the amorphous matrix are reduced. This structure can ensure that the alloy has good comprehensive magnetic properties, that is, high saturation magnetic induction intensity and low coercive force.

[0061] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims.

[0062] Any matters not described in detail in the present invention are well-known technologies to those skilled in the art.

Claims

1. A method for optimizing the magnetic properties of a high saturation magnetic induction iron-based nanocrystalline alloy, characterized in that: Includes the following: S1, based on the alloy molecular formula Fe a Co b Ni c B d Cu e Si f Ratio of raw materials, where a, b, c, d, e, and f represent the atomic percentage of the corresponding components, and satisfy the following conditions: 50≤a≤90, 1≤b≤40, 1≤c≤10, 1≤d≤20, 0.1≤e≤5, 0.1≤f≤5, and a+b+c+d+e+f=100; S2. Put the proportioned raw materials into a quartz tube and place it in the heating coil of a smelting furnace. Put B, Ni, Cu, and Si into the bottom of the quartz tube and cover it with Fe and Co. Then, introduce argon gas into a vacuum environment for smelting. After melting, keep the temperature for a period of time. After the smelting is completed, cool it to obtain a master alloy ingot. S3, crushing the master alloy ingot obtained in S2 into small pieces and polishing the impurities and oxides on the surface, placing the polished alloy block in a quartz tube, evacuating the quartz tube and introducing a protective gas; adjusting the rotation speed of the copper roller and the pressure difference between the inside and outside of the quartz tube; heating until the alloy block melts and turns bright red and rolls in the quartz tube, causing the solution to be rapidly sprayed along the nozzle at the bottom of the quartz tube onto the surface of the rapidly rotating copper roller due to the pressure difference, thereby rapidly solidifying to produce a continuous iron-based amorphous alloy strip; S4. Cut the iron-based amorphous alloy strip obtained in S3 into suitable sizes, place the cut samples in a heat treatment device, and perform a two-step annealing process of stress relief annealing + crystallization annealing in a high vacuum state and a longitudinal magnetic field. Water quenching is performed immediately after each annealing. The stress relief annealing temperature is 250-300°C and the holding time is 5-30 min. The crystallization annealing temperature is 350-500°C and the holding time is 1-15 min.

2. The method for optimizing the magnetic properties of a high saturation magnetic induction iron-based nanocrystalline alloy according to claim 1, characterized in that: In step S2, the vacuum degree of the vacuum environment is 3×10 -3 Pa, the melting temperature is 1300-1500℃, keep warm for 5-30 minutes after melting, and cool for 5-30 minutes after melting.

3. The method for optimizing the magnetic properties of a high saturation magnetic induction iron-based nanocrystalline alloy according to claim 1, characterized in that: In step S3, the vacuum degree is 3×10 -3 Pa, the protective gas is argon, and the pressure difference between the inside and outside of the quartz tube is 0.01-0.03 Pa.

4. The method for optimizing the magnetic properties of a high saturation magnetic induction iron-based nanocrystalline alloy according to claim 1, characterized in that: In step S3, the obtained iron-based amorphous alloy strip has a length of 0.5-5 m, a width of 0.8-1.5 mm, and a thickness of 15-25 um.

5. The method for optimizing the magnetic properties of a high saturation magnetic induction iron-based nanocrystalline alloy according to claim 1, characterized in that: In step S4, the magnetic field strength of the longitudinal magnetic field is 0.05-0.1 T.

6. The method for optimizing the magnetic properties of a high saturation magnetic induction iron-based nanocrystalline alloy according to claim 1, characterized in that: In step S4, the temperature of the crystallization annealing is 360-400°C.

7. A high saturation magnetic induction iron-based nanocrystalline alloy, characterized by: The method is prepared according to any one of claims 1 to 6.

8. The high saturation magnetic induction iron-based nanocrystalline alloy according to claim 7, characterized in that: The saturation magnetic induction intensity of the iron-based nanocrystalline alloy can reach 1.80-1.91 T, and the coercive force can reach 0.5-10 A / m.

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