A method for preparing soft magnetic material applied to electromagnetic nondestructive testing

Abstract

The application discloses a preparation method of soft magnetic material applied to electromagnetic nondestructive testing, and comprises the following steps: firstly, mixing multiple metal powders uniformly; secondly, loading the high-entropy alloy powder obtained in the first step into a cold spraying powder feeder, and starting a cold spraying device to spray; the spraying is performed in multiple layers, the spraying track of each layer is in a snake shape, and adjacent layers are staggered with each other; thirdly, processing; fourthly, heat treatment; fifthly, tightly winding an excitation coil on a yoke frame of the magnetic yoke obtained in the fourth step and fixing the excitation coil by using glue; or, tightly winding a detection coil on the magnetic core obtained in the fourth step and fixing the detection coil by using glue; and finally, installing the magnetic yoke with the wound excitation coil or the magnetic core with the wound detection coil in an electromagnetic nondestructive testing device. The prepared magnetic yoke and magnetic core have the advantages of high strength / hardness, corrosion resistance, oxidation resistance, good magnetization effect and long service life.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic nondestructive testing technology, and relates to a soft magnetic material, and more particularly to a method for preparing a soft magnetic material for electromagnetic nondestructive testing. Background Technology

[0002] Electromagnetic nondestructive testing (EDT) technology, as an emerging and promising NDT technique, possesses unique advantages in defect detection, crack prediction, and stress assessment of ferromagnetic materials. Using EDT equipment, the magnetic signal of the target sample can be obtained. Accurate and stable magnetic signals play a decisive role in assessing component damage, and the material properties of the yoke and core, such as soft magnetism and saturation magnetization, are key factors influencing the magnetic signal. To further advance EDT technology, it is necessary to develop a novel soft magnetic material.

[0003] High-entropy alloys (HEAs) are a class of advanced multi-principal element alloy materials proposed in 2004 by Ye Junwei, Cantor, and others. They are designed primarily based on configurational entropy and employ a method of introducing "chemical disorder" through multi-principal element mixing to prepare novel metallic materials. HEAs exhibit high mixing entropy effects, hysteresis diffusion effects, cocktail effects, and lattice distortion effects. Their solid solution structures are simple, with high strength / hardness, good structural stability, corrosion resistance, and oxidation resistance. Studies have shown that some HEAs possess excellent soft magnetic properties.

[0004] Currently, the main methods for preparing high-entropy alloy materials include: metallurgical methods, electric arc melting, laser cladding, and cold spraying. Cold spraying, as a low-temperature solid-state deposition technology, has achieved the deposition of various metals and their alloys, metal matrix composites, ceramics, polymers, and other materials. The resulting coatings or bulk materials can retain the original structure of the powder, avoiding metallurgical defects such as component oxidation, phase structure changes, thermal stress accumulation, and grain growth caused by "melt-solidification" preparation techniques. This provides a new approach for the preparation of high-performance high-entropy alloys. However, due to the mechanical bonding mechanism between the cold-sprayed powder and the substrate, materials prepared by cold spraying suffer from drawbacks such as low bonding strength and insufficient toughness. Summary of the Invention

[0005] This invention proposes a method for preparing soft magnetic materials for electromagnetic nondestructive testing (NDT). The prepared soft magnetic materials serve as the excitation yoke and the magnetic core within the detection coil of an NDT device. The excitation yoke and the magnetic core within the detection coil prepared by this method can obtain magnetic signals with low noise, good stability, and high accuracy. After processing and heat treatment, the excitation yoke exhibits advantages over traditional manganese-zinc ferrite yokes and nickel-zinc ferrite yokes, including higher strength / hardness, corrosion resistance, oxidation resistance, good magnetization effect, and long service life. Similarly, the magnetic core within the detection coil, after processing and heat treatment, exhibits advantages over traditional iron cores and hydrogen ferrite cores, including higher strength / hardness, corrosion resistance, oxidation resistance, good magnetic properties, and long service life. This invention further improves the accuracy of detection signals in electromagnetic NDT equipment, enabling the further promotion of electromagnetic NDT technology.

[0006] To achieve the above objectives, this invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, characterized by the following steps: Step 1: Mixing various metal powders uniformly to obtain high-entropy alloy powder; Step 2: Loading the high-entropy alloy powder obtained in Step 1 into a cold spray powder feeder and starting the cold spray device for spraying; Spraying multiple layers of coating, with each layer having a serpentine spraying trajectory and adjacent layers interleaving; After spraying, a high-entropy alloy blank is obtained; The high-entropy alloy blank is a high-entropy alloy magnetic yoke blank or a high-entropy alloy detection coil inner magnetic core blank; Step 3: The high-entropy alloy obtained in Step 2... The magnetic yoke blank or the high-entropy alloy detection coil inner core blank is processed to obtain a high-entropy alloy magnetic yoke or a high-entropy alloy detection coil inner core; Step four: The high-entropy alloy magnetic yoke or the high-entropy alloy detection coil inner core obtained in step three is heat-treated to obtain a magnetic yoke or a magnetic core; heat treatment can enhance the crack resistance of the magnetic yoke and the magnetic core; Step five: The excitation coil is tightly wound around the yoke frame of the magnetic yoke obtained in step four and fixed with glue; or, the detection coil is tightly wound around the magnetic core obtained in step four and fixed with glue; The magnetic yoke with the excitation coil wound or the magnetic core with the detection coil wound is installed in the electromagnetic non-destructive testing equipment.

[0007] Furthermore, the present invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: wherein, in step one, the various metal powders include, by molar proportion: Co 10-30%, Cu 10-30%, Fe 10-30%, Mn 10-30%, and Ni 10-30%.

[0008] Furthermore, the present invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: in step one, multiple metal powders are mixed in the following molar ratios: Co 18%, Cu 18%, Fe 23%, Mn 19%, and Ni 22%.

[0009] Furthermore, the present invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: in step one, multiple metal powders are mixed by mechanical stirring, the stirring temperature is room temperature, the relative air humidity is not greater than 70%, the stirring speed is 60 r / min, and the mixing time is 2-3 h.

[0010] Furthermore, this invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: In step two, the specific process of spraying is as follows: the nozzle moves a distance W along the positive X-axis from the starting point position 0 to position 1, then moves a distance M along the positive Y-axis to position 2, then moves a distance W along the negative X-axis from position 2 to position 3, then moves a distance M along the positive Y-axis to position 4; this operation is repeated until the total distance the nozzle moves along the positive Y-axis reaches the size of the high-entropy alloy blank, completing the spraying of the first coating layer; and the ending position and the starting point are both located at the same position on the X-axis; then, the nozzle moves a distance M / 2 along the Y-axis to position k, then rises a distance G along the positive Z-axis to begin spraying the second coating layer; the nozzle moves a distance W along the positive X-axis from the raised position k to position m, then... The nozzle moves a distance M along the negative Y-axis to position j, then moves a distance W along the negative X-axis to position i, and then moves a distance M along the negative Y-axis to position h. This process is repeated until the total distance the nozzle moves along the negative Y-axis reaches the size of the high-entropy alloy blank, completing the second coating layer. This process is repeated until the Nth coating layer is completed. The coating layers are staggered, with odd-numbered layers following the same trajectory as the first layer and even-numbered layers following the same trajectory as the second layer. This staggered coating method avoids stress concentration and powder accumulation. The distance W along the X-axis and the number of coatings N are set according to the size of the high-entropy alloy blank. Specifically, the distance W along the X-axis, the total distance along the Y-axis when spraying each coating layer (related to the number of repeated movements), and the distance G multiplied by the number of coatings N constitute the width, length, and height of the high-entropy alloy blank, respectively.

[0011] Furthermore, the present invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: wherein the distance M is 3-8 mm; and the distance G is 0.1-0.6 mm.

[0012] Furthermore, the present invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: in step two, during the spraying process, the moving speed of the nozzle is 0.5 mm / s-1 mm / s; the spraying is cold spraying, and its process parameters are: the working gas is nitrogen, helium or compressed air, the carrier gas pressure is 0.7-1 MPa, the carrier gas temperature is 200-600℃, the powder particle velocity is 600-1000 m / s, the powder particle size is 15-40 μm, and the lift-off height is 5-10 mm.

[0013] Furthermore, this invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: The dimensions of the high-entropy alloy magnetic yoke blank obtained in step two are: length 50-140 mm, width 30-100 mm, and height 50-120 mm; the dimensions of the magnetic core blank inside the high-entropy alloy detection coil are: length 23-30 mm, width 23-30 mm, and height 30-55 mm. The dimensions of the high-entropy alloy magnetic yoke obtained in step three are: length 30-120 mm, width 10-80 mm, and height 30-100 mm; the dimensions of the magnetic core inside the high-entropy alloy detection coil are: bottom diameter 3-10 mm and height 10-30 mm; the processing error does not exceed 1 mm, and the surface roughness does not exceed 6.3 μm.

[0014] Furthermore, the present invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: in step three, the processing is performed by using a CNC machine tool to perform roughing and finishing in sequence.

[0015] Furthermore, the present invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: in step four, the heat treatment is normalizing at 800-900℃ for 2-2.5h.

[0016] Furthermore, the present invention provides a method for preparing soft magnetic materials for electromagnetic nondestructive testing, which may also have the following characteristics: in step five, the excitation coil wound on the yoke frame of the magnetic yoke has 200-600 turns; the detection coil wound on the magnetic core has 400-1000 turns.

[0017] The magnetic yokes and cores prepared by the above-mentioned method for preparing soft magnetic materials for electromagnetic nondestructive testing can be used in electromagnetic nondestructive testing equipment, including magnetic Barkhausen, magnetic probe, differential permeability, eddy current, and leakage magnetic field testing equipment.

[0018] The beneficial effects of this invention are as follows:

[0019] First, the excitation yoke prepared by this invention exhibits better soft magnetism, lower coercivity, and higher saturation magnetization compared to traditional manganese-zinc ferrite yokes and nickel-zinc ferrite yokes, resulting in better magnetization of ferromagnetic samples. Similarly, the magnetic core prepared by this invention exhibits better soft magnetism, lower coercivity, and higher saturation magnetization compared to traditional iron cores and ferrooxide cores, resulting in better magnetization of the core. Using the high-entropy alloy material prepared by this invention as the excitation yoke and magnetic core of electromagnetic nondestructive testing equipment can yield magnetic signals with low noise, good stability, and high accuracy.

[0020] Second, the excitation yoke and magnetic core prepared by this invention, after being normalized at 800-900℃, produce annealed twins, and the size of the Cr-rich second phase precipitated at the grain boundaries and twin boundaries further increases. Compared with the as-cast condition, the cold-sprayed high-entropy alloy after heat treatment maintains its wear resistance and plastic deformation ability, and its resistance to crack damage is improved.

[0021] Third, the excitation yoke obtained by this invention has higher strength / hardness, corrosion resistance, oxidation resistance, good magnetization effect, and long service life compared with traditional manganese-zinc ferrite yokes and nickel-zinc ferrite yokes; the magnetic core obtained by this invention has higher strength / hardness, corrosion resistance, oxidation resistance, good magnetization effect, and long service life compared with traditional iron cores and ferrooxide cores.

[0022] Fourth, traditional manganese-zinc ferrite yokes, nickel-zinc ferrites, iron cores, and ferrooxide are all brittle materials, prone to breakage and fracture during processing. In contrast, the excitation yoke and core produced by this invention have good toughness and are easier to process into different shapes, thus saving production costs.

[0023] Fifth, the cold spraying process of this invention adopts an interlaced layering method, which avoids the stress concentration effect caused by continuous powder accumulation during the spraying process, and at the same time slows down the erosion and wear of the accumulated powder.

[0024] VI. The high-entropy alloy soft magnetic material prepared by this invention is mainly used in the excitation yoke and the iron core inside the detection coil in electromagnetic non-destructive testing equipment, and can also be applied to other technical fields. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the nozzle movement path for spraying to prepare the high-entropy alloy blank in step two of this invention;

[0026] Figure 2 This is a schematic diagram of the magnetic Barkhausen device in the embodiment;

[0027] Figure 3 This is a field emission scanning electron microscope (SEM) image of the high-entropy alloy magnetic yoke blank prepared in step two of Example 1;

[0028] Figure 4 This is a hysteresis loop diagram measured by a magnetometer on a VSM vibrating sample of a high-entropy alloy yoke blank prepared in step two of Example 1.

[0029] Figure 5 This is a partially enlarged view of the hysteresis loop measured by a magnetometer on a VSM vibrating sample of a high-entropy alloy yoke blank prepared in step two of Example 1. Detailed Implementation

[0030] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] Example 1

[0032] This embodiment provides a method for preparing an excitation magnetic yoke for electromagnetic nondestructive testing, comprising the following steps:

[0033] Step 1: Mix the metal powders according to the following molar ratios: Co 18%, Cu 18%, Fe 23%, Mn 19%, Ni 22%. To keep the metal powders dry, mechanically stir and mix them at room temperature on a sunny day for 2.5 hours at a stirrer speed of 60 r / min. The mixture should be homogeneous to obtain high-entropy alloy powder.

[0034] Step 2: Load the high-entropy alloy powder obtained in Step 1 into the cold spray powder feeder. The nozzle moving speed is 0.8 mm / s and the lift-off height is 8 mm. The cold spray process parameters are: the working gas is compressed air, the carrier gas pressure is 0.8 MPa, the carrier gas temperature is 500℃, the powder particle velocity is 800 m / s, and the powder particle size is 30 μm.

[0035] Start the cold spraying equipment to spray, such as Figure 1As shown: The nozzle moves a distance W along the positive X-axis from the starting point 0 to position 1, then moves 5mm (distance M) along the positive Y-axis to position 2. From position 2, it moves a distance W along the negative X-axis to position 3, then moves another 5mm along the positive Y-axis to position 4. This movement is repeated until the nozzle reaches position 11, completing the first coating layer. Next, the nozzle moves 2.5mm (distance M / 2) along the Y-axis to position k, then rises 0.5mm (distance G) along the positive Z-axis to begin the second coating layer. From the raised position k, the nozzle moves a distance W along the positive X-axis to position m, then moves 5mm along the negative Y-axis to position j, then moves a distance W along the negative X-axis to position i, then moves another 5mm along the negative Y-axis to position h. This process is repeated until the nozzle reaches position a, completing the second coating layer. Position a is 2.5mm from position 0 along the positive Y-axis. To avoid stress concentration and powder buildup, the sprayed coatings are staggered, with odd-numbered layers following the same trajectory as the first layer and even-numbered layers following the same trajectory as the second layer.

[0036] Repeat the above operation, with each coating layer having an average thickness (distance G) of 0.5 mm, until the 200th coating layer is applied. Then, turn off the cold spraying device to obtain a high-entropy alloy magnetic yoke blank with dimensions of 100 mm in length, 80 mm in width, and 100 mm in height. The SEM image of this high-entropy alloy magnetic yoke blank is shown below. Figure 3 As shown, the hysteresis loop measured by the VSM vibrating sample magnetometer is as follows: Figure 4 and 5 As shown. From Figure 4 It can be seen that the saturation magnetization of this high-entropy alloy magnetic yoke blank under a magnetic field strength of 2T is 7.8 emu / g. Figure 5 It can be seen that the coercivity of the high-entropy alloy blank under a magnetic field strength of 2T is 24.4Oe, that is, the high-entropy alloy yoke blank has a high saturation magnetization and a low coercivity.

[0037] Step 3: Machining the high-entropy alloy yoke blank obtained in Step 2. Using a CNC machine tool, perform roughing and finishing in sequence to obtain the required U-shaped high-entropy alloy yoke. The U-shaped high-entropy alloy yoke is 80mm long, 60mm wide, and 80mm high, with a machining error not exceeding 1mm.

[0038] Step 4: The U-shaped high-entropy alloy yoke obtained in Step 3 is normalized at 850℃ for 2 hours to enhance the crack resistance of the U-shaped high-entropy alloy yoke. The yoke is obtained after heat treatment.

[0039] Step 5: Tightly wind 300 turns of the excitation coil onto the yoke frame of the magnetic yoke obtained after heat treatment in Step 4, and fix it with glue. Then install it in the electromagnetic non-destructive testing equipment. In this embodiment, the electromagnetic non-destructive testing equipment is a magnetic Barkhausen device, such as... Figure 2 As shown, the device includes: a signal generator 1, a power amplifier 2, an excitation yoke 3, an excitation coil 4, a magnetic core 5, a detection coil 6, a voltage amplifier 7, a data acquisition card 8, and a host computer 9.

[0040] Example 2

[0041] This embodiment provides a method for preparing a magnetic core inside a detection coil for electromagnetic nondestructive testing, comprising the following steps:

[0042] Step 1: Mix the metal powders according to the following molar ratios: Co 18%, Cu 18%, Fe 23%, Mn 19%, Ni 22%. To keep the metal powders dry, mechanically stir and mix them at room temperature on a sunny day for 2.5 hours at a stirrer speed of 60 r / min. The mixture should be homogeneous to obtain high-entropy alloy powder.

[0043] Step 2: Load the high-entropy alloy powder obtained in Step 1 into the cold spray powder feeder. The nozzle moving speed is 0.8 mm / s and the lift-off height is 8 mm. The cold spray process parameters are: the working gas is compressed air, the carrier gas pressure is 0.9 MPa, the carrier gas temperature is 550℃, the powder particle velocity is 850 m / s, and the powder particle size is 30 μm.

[0044] Start the cold spraying equipment to spray, such as Figure 1 As shown: The nozzle moves a distance W along the positive X-axis from the starting point 0 to position 1, then moves 5mm (distance M) along the positive Y-axis to position 2. From position 2, it moves a distance W along the negative X-axis to position 3, then moves another 5mm along the positive Y-axis to position 4. This movement is repeated until the nozzle reaches position 11, completing the first coating layer. Next, the nozzle moves 2.5mm (distance M / 2) along the Y-axis to position k, then rises 0.5mm (distance G) along the positive Z-axis to begin the second coating layer. From the raised position k, the nozzle moves a distance W along the positive X-axis to position m, then moves 5mm along the negative Y-axis to position j, then moves a distance W along the negative X-axis to position i, then moves another 5mm along the negative Y-axis to position h. This process is repeated until the nozzle reaches position a, completing the second coating layer. Position a is 2.5mm from position 0 along the positive Y-axis. To avoid stress concentration and powder buildup, the sprayed coatings are staggered, with odd-numbered layers following the same trajectory as the first layer and even-numbered layers following the same trajectory as the second layer.

[0045] Repeat the above operation, with an average coating thickness (distance G) of 0.5 mm for each layer, until the 80th layer is completed. Then turn off the cold spraying device to obtain a high-entropy alloy detection coil inner core blank with dimensions of 25 mm in length, 25 mm in width, and 40 mm in height.

[0046] Step 3: Machining the high-entropy alloy detection coil inner core blank obtained in Step 2. Using a CNC machine tool, perform roughing and finishing processes sequentially to obtain the required high-entropy alloy detection coil inner core. The bottom diameter of the high-entropy alloy detection coil inner core is 5mm, and its height is 20mm, with a machining error not exceeding 1mm.

[0047] Step 4: The high-entropy alloy detection coil core obtained in Step 3 is normalized at 900℃ for 2.5 hours to enhance the crack resistance of the high-entropy alloy detection coil core. The core is obtained after heat treatment.

[0048] Step 5: Tightly wind 600 turns of the detection coil onto the magnetic core obtained after heat treatment in Step 4, and fix it with glue. Then install it in the electromagnetic non-destructive testing equipment. In this embodiment, the electromagnetic non-destructive testing equipment is a magnetic Barkhausen device, such as... Figure 2 As shown, the device includes: a signal generator 1, a power amplifier 2, an excitation yoke 3, an excitation coil 4, a magnetic core 5, a detection coil 6, a voltage amplifier 7, a data acquisition card 8, and a host computer 9.

[0049] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for preparing soft magnetic materials for electromagnetic nondestructive testing, characterized in that: Includes the following steps: Step 1: Mix the various metal powders evenly to obtain high-entropy alloy powder; the various metal powders include, according to the molar ratio: Co 10-30%, Cu 10-30%, Fe 10-30%, Mn 10-30%, and Ni 10-30%. Step 2: Load the high-entropy alloy powder obtained in Step 1 into the cold spray powder feeder, and start the cold spray device for spraying; spray multiple layers of coating, with the spraying trajectory of each layer being serpentine and the adjacent layers intersecting each other; after spraying is completed, a high-entropy alloy blank is obtained. The high-entropy alloy blank is either a high-entropy alloy magnetic yoke blank or a high-entropy alloy detection coil inner magnetic core blank. Step 3: Process the high-entropy alloy yoke blank or the high-entropy alloy detection coil inner core blank obtained in Step 2 to obtain the high-entropy alloy yoke or the high-entropy alloy detection coil inner core. Step 4: Heat-treat the high-entropy alloy yoke or the magnetic core inside the high-entropy alloy detection coil obtained in Step 3 to obtain the yoke or the magnetic core. Step 5: Tightly wind the excitation coil around the yoke frame of the magnetic yoke obtained in Step 4 and fix it with glue; or, tightly wind the detection coil around the magnetic core obtained in Step 4 and fix it with glue; install the magnetic yoke with the excitation coil wound or the magnetic core with the detection coil wound in the electromagnetic non-destructive testing equipment.

2. The method for preparing soft magnetic materials for electromagnetic nondestructive testing according to claim 1, characterized in that: in, In step one, multiple metal powders are mixed in the following molar ratios: Co 18%, Cu 18%, Fe 23%, Mn 19%, and Ni 22%.

3. The method for preparing soft magnetic materials for electromagnetic nondestructive testing according to claim 1, characterized in that: in, In step one, multiple metal powders are mixed by mechanical stirring at room temperature, relative humidity not exceeding 70%, stirring speed of 60 r / min, and mixing time of 2-3 h.

4. The method for preparing soft magnetic materials for electromagnetic nondestructive testing according to claim 1, Its features are: In step two, the specific process of spraying is as follows: The nozzle moves a distance W along the positive X-axis from the starting point, then a distance M along the positive Y-axis, then a distance W along the negative X-axis, and then a distance M along the positive Y-axis. This process is repeated until the total distance the nozzle moves along the positive Y-axis reaches the size of the high-entropy alloy blank, thus completing the application of the first coating layer. Then, move the nozzle a distance M / 2 along the Y-axis, and then move it a distance G along the positive Z-axis to begin spraying the second coating layer; move the nozzle a distance W along the positive X-axis, then a distance M along the negative Y-axis, then a distance W along the negative X-axis, and then a distance M along the negative Y-axis; repeat the above operation until the total distance the nozzle moves along the negative Y-axis reaches the size of the high-entropy alloy blank, and the spraying of the second coating layer is completed; Repeat the above operation until the Nth layer of coating is applied; the coatings are interleaved, with odd-numbered layers following the same trajectory as the first layer, and even-numbered layers following the same trajectory as the second layer. The distance W along the X-axis and the number of coatings N are set according to the size of the high-entropy alloy blank.

5. The method for preparing soft magnetic materials for electromagnetic nondestructive testing according to claim 4, characterized in that: in, The distance M is 3-8 mm; the distance G is 0.1-0.6 mm.

6. The method for preparing soft magnetic materials for electromagnetic nondestructive testing according to claim 1, characterized in that: in, In step two, during the spraying process, the nozzle moving speed is 0.5 mm / s-1 mm / s; The spraying is a cold spraying, and its process parameters are as follows: the working gas is nitrogen, helium or compressed air, the carrier gas pressure is 0.7-1 MPa, the carrier gas temperature is 200-600℃, the powder particle velocity is 600-1000 m / s, the powder particle size is 15-40μm, and the lift-off height is 5-10 mm.

7. The method for preparing soft magnetic materials for electromagnetic nondestructive testing according to claim 1, characterized in that: in, In step three, the machining process involves using a CNC machine tool to perform roughing and finishing in sequence.

8. The method for preparing soft magnetic materials for electromagnetic nondestructive testing according to claim 1, characterized in that: in, In step four, the heat treatment is normalizing at 800-900℃ for 2-2.5 hours.

9. The method for preparing soft magnetic materials for electromagnetic nondestructive testing according to claim 1, characterized in that: in, In step five, the excitation coil wound on the yoke frame of the yoke has 200-600 turns; the detection coil wound on the magnetic core has 400-1000 turns.

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