CN112195423B

CN112195423B - Composite heat treatment method for optimizing magnetic property of amorphous wire

Info

Publication number: CN112195423B
Application number: CN202011043804.1A
Authority: CN
Inventors: 李广敏; 刘天成; 金晶
Original assignee: Advanced Technology and Materials Co Ltd
Current assignee: Advanced Technology and Materials Co Ltd
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2021-10-26
Anticipated expiration: 2040-09-28
Also published as: CN112195423A

Abstract

The invention discloses a composite heat treatment method for optimizing the magnetic property of an amorphous wire, which combines isothermal annealing and current annealing and comprises the following steps: in the presence of protective atmosphere, the amorphous wire is heated to the required temperature along with the furnace and then is subjected to heat preservation treatment, and during the heat preservation treatment, pulse current is applied to the amorphous wire, so that the amorphous wire obtains the required magnetic performance. The composite heat treatment method mainly comprises the steps of carrying out isothermal annealing, effectively releasing internal stress of the amorphous wire in a heating furnace cavity with protective atmosphere, further releasing the internal stress and realizing annular excitation of the amorphous wire by means of auxiliary heat treatment of pulse current, inducing annular anisotropy, effectively improving the magnetic performance of the amorphous wire, particularly optimizing the annular magnetic performance, meeting the key magnetic core performance requirement of an orthogonal fluxgate mode and improving the precision of a weak magnetic sensor. The amorphous wire obtained by the composite heat treatment method can be well applied to GMI, flux gates and other sensing soft devices.

Description

Composite heat treatment method for optimizing magnetic property of amorphous wire

Technical Field

The invention belongs to the key technical field of metal heat treatment, relates to a heat treatment method of a metal soft magnetic material, and particularly relates to a composite heat treatment method for a special metal soft magnetic material amorphous wire.

Background

The amorphous wire has a special magnetic domain structure, can show excellent magnetic performance, such as obvious giant magneto-impedance characteristic and typical large Barkhausen effect, and is widely applied to weak magnetic sensors or other anti-counterfeiting devices.

The Taylor method is the method which is firstly proposed by Taylor of England scientist in 1924, and the early Taylor method is to mount metal or alloy in a glass tube with the diameter of 2mm, heat the glass tube to be molten by air flame, and then produce wire with the diameter of 0.1-5.0 mm by a manual drawing mode. Ulitovsky improves the Taylor method on the basis of the original method, adopts a high-frequency induction coil to heat metal, and adds a micro-wire winding mechanism, thereby realizing semi-continuous production. At present, the preparation technology of glass-coated microfilaments in industrially developed countries is developed on the basis of the Taylor-Uliotvsky method. The diameter of the glass-coated amorphous wire prepared by the method is 10-200 μm. However, the amorphous wire prepared by the method has large residual internal stress, large internal magnetoelastic performance of the material and poor circumferential anisotropic performance, and the main reason is that in the preparation process, the liquid molten flow of the master alloy is solidified along the radial direction of the wire from outside to inside in the rapid solidification process, so that the internal residual internal stress is large, and the surface stress and the axial tensile stress of the amorphous wire are further increased by the amorphous wire after cold drawing. Because the internal stress not only affects the magnetic domain structure of the amorphous wire, but also increases domain wall energy, under the high-frequency excitation state, the magnetic core temperature is raised, the temperature drift is serious, the absolute value of the magnetostriction coefficient is large, and the sensor precision is affected; and the circumferential magnetic property can affect the overall performance of the sensor measurement. Therefore, the residual internal stress caused by rapid solidification or the surface stress and the axial tensile stress caused by later cold drawing influence the comprehensive magnetic core performance index of the amorphous wire as the core sensor material.

At present, in practical application, the amorphous wire needs to be subjected to proper modulation annealing treatment to eliminate internal stress, adjust structural relaxation, and improve the toroidal magnetic anisotropy and the toroidal magnetic permeability, so as to improve the magnetic performance of the amorphous wire. Isothermal annealing and current annealing are two common methods for modulating the performance of amorphous wires. Isothermal annealing can effectively release the residual stress of the amorphous wire and promote structural relaxation, but the method is not favorable for the formation of the annular magnetic domain of the amorphous wire. The current annealing passes through joule heat and a toroidal magnetization magnetic field, so that the residual internal stress of the amorphous wire is released, the volume of an axial magnetic domain is reduced, the volume of a toroidal magnetic domain is enlarged, and the toroidal magnetic anisotropy and the toroidal magnetic permeability are effectively improved.

However, the conventional heat treatment of amorphous wire is generally current joule processing, the adopted current is mostly square wave, and in the heat treatment process, the pure current joule processing temperature is uncontrollable, and the stress elimination effect is not ideal because the high-temperature period time is short.

Patent CN 109402339 a discloses a pulse square wave current annealing method for modulating the performance of an amorphous alloy wire, which can not only make the amorphous alloy wire reach a proper annealing temperature by joule heat, but also generate a large enough toroidal magnetization magnetic field by instantaneous square wave current, so that the toroidal magnetic domain volume of the amorphous alloy wire is increased, and the toroidal magnetization purpose is achieved. However, it is not possible to control the annealing temperature by only the joule heat generated by the pulse current, and the joule heat generated by the current and the modulation effect of the ring magnetic property cannot be obtained at the same time.

Therefore, the heat treatment method which can perform stress relief treatment on the amorphous wire and can also increase circumferential anisotropy intervention means is provided, and the heat treatment method has important significance for realizing modulation of the performance of the amorphous wire.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a composite heat treatment method for optimizing the magnetic property of an amorphous wire, which solves various residual stresses caused by the preparation process and the post-drawing treatment of a quenched amorphous wire, optimizes the annular magnetic property of the amorphous wire, reduces the loss of a magnetic core and improves the annular rectangular ratio.

In order to achieve the above purpose, the invention provides the following technical scheme:

a composite heat treatment method for optimizing the magnetic performance of amorphous wire features that under the existance of protecting atmosphere, the temp of amorphous wire is raised to needed temp and then heat-insulating, and during the heat-insulating treatment, pulse current is applied to the amorphous wire to obtain needed magnetic performance.

In the above-described composite heat treatment method, as a preferred embodiment, the pulse current is a unidirectional pulse current, and a waveform of the pulse current is a triangular wave.

In the invention, during the heat preservation thermal treatment, unidirectional pulse current is applied to the amorphous wire, and the unidirectional pulse current generates magnetization in the annular direction or the transverse direction of the amorphous wire, so that the modulation of annular or transverse magnetic anisotropy is achieved, and the squareness ratio is improved.

The invention adopts triangular wave pulse current, the duty ratio of the triangular wave is low, the high-order pulse electrifying time is short, the heating is less, and the annular anisotropy is generated for the wire material only by the peak pulse.

In the above-mentioned composite heat treatment method, as a preferred embodiment, the pulse frequency of the pulse current is 50Hz to 2kHz (e.g., 100Hz, 200Hz, 500Hz, 1000Hz, 1200Hz, 1500Hz, 2kHz), and the pulse current amplitude is 50mA to 150mA (e.g., 80mA, 100mA, 115mA, 130mA, 140 mA); preferably, the energizing time of the pulse current is 0.5h-5h (e.g., 0.5h, 1h, 2h, 3h, 4h, 4.5 h).

In the above composite heat treatment method, as a preferred embodiment, the heat treatment temperature of the amorphous wire is an amorphous wire stress removal temperature; preferably, the heat treatment temperature of the amorphous wire is 150 ℃ to 300 ℃ (e.g., 150 ℃, 180 ℃, 200 ℃, 220 ℃, 260 ℃, 300 ℃) and the holding time is 0.5h to 5h (e.g., 0.5h, 1h, 2h, 3h, 4h, 4.5 h); more preferably, the heat preservation time is the same as the electrifying time of the pulse current, namely, the pulse current treatment is carried out at the same time of the heat preservation heat treatment of the amorphous wire.

Here, the heat-insulating treatment of the amorphous wire is an isothermal annealing process.

According to the invention, the triangular wave of 50Hz-2kHz is adopted to carry out heat treatment on the amorphous wire, and under the frequency, the heat quantity brought by eddy current loss is small, and the disturbance on the heat preservation temperature is not large, so that the influence of the frequency on the annular rectangular ratio is small; the heat caused by eddy current loss is obvious at high frequency (such as 2kHz-100kHz), and the heating of the wire material and the furnace temperature are superposed, thus being not beneficial to the heat treatment effect. Therefore, in the invention, the frequency (50-2kHz) adopted by the triangular wave comprehensively considers the influence of the eddy current loss on the heat preservation temperature and the circular squareness ratio, and is a frequency band selection which is considered at the same time.

In the composite heat treatment method, as a preferred embodiment, the amorphous wire is a cobalt-based amorphous wire, and preferably, the amorphous wire may be a round-section wire or a thin-strip wire; still preferably, when the amorphous wire is a round-section wire, the diameter of the amorphous wire is 10 μm to 180 μm.

In the above composite heat treatment method, as a preferred embodiment, the protective atmosphere may be any one of argon, nitrogen, and hydrogen.

In the invention, the amorphous wire is subjected to heat treatment in a protective atmosphere, so that the surface of the amorphous wire can be prevented from being oxidized to further influence the magnetic property.

In the above composite heat treatment method, as a preferred embodiment, in the heat treatment furnace, the amorphous wire is fixed on a non-metal substrate in a heating furnace, the non-metal substrate is a non-magnetic conductive and non-conductive material, and a wire length direction of the amorphous wire is identical to a furnace body length direction of the heating furnace.

In the present invention, the amorphous wire must be fixed on a non-magnetic and non-conductive non-metallic substrate during the heat-insulating treatment. The purpose of adopting the non-magnetic and non-conductive non-metallic matrix is to prevent the magnetic field generated by the current passing through the amorphous wire from failing, and the purpose of fixing the amorphous wire is to prevent the flow of protective gas from disturbing the amorphous wire due to the light weight of the amorphous wire. And the method of placing the amorphous wire in the length direction consistent with the length direction of the furnace chamber is adopted, so that the amorphous wire is not easily disturbed, and the effect of preventing the surface of the amorphous wire from being oxidized is achieved.

In the above composite heat treatment method, as a preferred embodiment, the amorphous wire is placed in a middle region in the heating furnace, and a temperature difference between two ends of the amorphous wire is less than ± 1 ℃.

In the invention, the amorphous wire is placed in the middle area in the heating furnace, so that the large temperature difference at the two ends of the amorphous wire is avoided, and the temperature difference at the two ends of the amorphous wire in the heating furnace is ensured to be less than +/-1 ℃.

In the above-mentioned composite heat treatment method, as a preferred embodiment, after the heat treatment and heat preservation are completed, the sample is taken out and air-cooled to room temperature, thereby achieving the purpose of stress relief.

In the invention, the technical characteristics can be freely combined to form a new technical scheme under the condition of not conflicting with each other.

Compared with the prior art, the invention has the following beneficial effects:

(1) compared with the joule heat generated by adopting single current, the composite heat treatment method can control the temperature better and achieve the effect of uniform temperature of the surface and the core of the wire material;

(2) the composite heat treatment method combining isothermal annealing and current annealing is adopted, the isothermal annealing is taken as a main point, the effective release of the internal stress of the amorphous wire in a heating furnace cavity with protective atmosphere is realized, meanwhile, the auxiliary heat treatment of the pulse current is used for further releasing the internal stress and realizing the circumferential excitation of the amorphous wire, the circumferential anisotropy is induced, the magnetic performance of the amorphous wire is effectively improved, the key heat treatment technology of the amorphous wire is solved, particularly the optimization of the circumferential magnetic performance is realized, the requirement of a fluxgate sensor on the circumferential rectangular ratio can be met, and the precision of the weak magnetic sensor is improved.

(3) The bottleneck problem of the key magnetic core material of the high-precision sensor in China is solved, and the substitution of the domestic key soft magnetic material product for the imported soft magnetic material product is also completed.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:

FIG. 1 is an SEM photograph of the diameter of an amorphous wire used in an embodiment of the present invention.

FIG. 2 is a schematic view of the heat treatment of an amorphous wire according to the present invention. Wherein, the part names represented by the numbers are as follows: 1 is amorphous wire, 2 is pulse current, 3 is a non-metallic material matrix, 4 is protective gas, and 5 is a heating furnace.

FIG. 3 is a graph showing the rectangular ratio of the amorphous wire after heat treatment according to the present invention in example 1 as a function of the current value.

FIG. 4 is a graph showing the rectangular ratio of an amorphous wire as a function of heat treatment time in example 2 of the present invention.

FIG. 5 is a graph showing the variation rate of the resistance of the amorphous wire with the temperature of the heat treatment in example 3 of the present invention.

FIG. 6 is a graph showing the rectangular ratio of amorphous wire as a function of the frequency of the triangular wave current in example 4 of the present invention.

FIG. 7 shows the variation of the magnetic field sensitivity of the amorphous wire with the squareness ratio in example 5 of the present invention.

Detailed Description

The invention will be described in detail below with reference to the drawings attached to the specification and embodiments. The various examples are provided by way of explanation of the invention, and not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. It is therefore intended that the present invention encompass such modifications and variations as fall within the scope of the appended claims and equivalents thereof.

The invention provides a composite heat treatment method for optimizing the magnetic property of an amorphous wire, which adopts a composite heat treatment method combining isothermal annealing and current annealing, and carries out heat preservation heat treatment after the temperature of the amorphous wire is raised to a heat preservation temperature along with a furnace in the presence of a protective atmosphere, and during the heat preservation heat treatment, pulse current is applied to the amorphous wire so as to ensure that the amorphous wire obtains the required magnetic property. The amorphous wire used in the following examples of the present invention is a cobalt-based amorphous wire of a grade of 1k201, i.e., a Co-Fe-Si-B amorphous wire, and fig. 1 is a diameter SEM photograph of an untreated glass-coated amorphous wire prepared by a Taylor-Ulitovsky method, and the surface of the amorphous wire is smooth and neat. The specific operation is as follows:

the method comprises the steps of coating amorphous wires with glass with the length of 6cm as shown in figure 1, fixing two ends of the amorphous wires on a refractory substrate (namely, a non-metallic substrate), leading out wires welded and fixed at two ends of the amorphous wires out of a furnace body, introducing argon protective gas into the furnace chamber, heating the furnace chamber to 150-300 ℃, preserving heat, applying pulse current to the amorphous wires by adopting a pulse power supply, wherein the pulse current is unidirectional triangular wave, the frequency is 50Hz-2kHz, the amplitude of the pulse current is 40-150 mA, and the heat preservation time and the electrifying time are both 0.5-5 h.

The heat treatment principle of the amorphous wire adopted by the invention is shown in figure 2, the amorphous wire 1 is placed on a non-metallic material substrate 3 in a heating furnace 5 for heat treatment, protective gas 4 is introduced into a furnace chamber, leads are welded and fixed at two ends and led out of the furnace body, pulse current 2 is applied at two ends of the amorphous wire, the pulse current is a one-way triangular wave, the current generates a magnetic field in the annular direction of the amorphous wire, the internal stress of the amorphous wire is reduced, the annular induction strengthening is realized along the annular direction, the annular magnetic conductivity and the annular rectangular ratio are improved, the annular magnetic performance is optimized, and the purpose of optimizing the giant magneto-impedance characteristic of the amorphous wire is further realized.

Example 1

In this embodiment, two ends of a 6cm long glass-coated amorphous wire are fixed on a refractory substrate (i.e., a non-metallic substrate), two ends of the glass-coated amorphous wire are welded and fixed with wires and led out of a furnace body, argon gas is introduced into a furnace chamber, the temperature is maintained at 220 ℃, and triangular wave currents (current I) with different amplitudes of 50Hz are applied to the amorphous wire_ac0mA-145mA), and the heat preservation time is 2 h. Here, the current annealing is performed simultaneously with the isothermal annealing, that is, the energization time of the pulse current is 2 h.

The change of the amorphous wire rectangular ratio along with the change of the current value is shown in fig. 3, the annular rectangular ratio of the amorphous wire gradually increases along with the change of the current value, the current amplitude is 115mA and then basically tends to be stable, and the annular rectangular ratio of the amorphous wire is about 0.975 at the moment; and in the range of pulse current amplitude of 40-145 mA, the annular rectangular ratio of the amorphous wire is 0.87-0.975.

Example 2

In the embodiment, two ends of a glass-coated amorphous wire with the length of 6cm are fixed on a refractory substrate (namely, a non-metallic substrate), two ends of the glass-coated amorphous wire are welded and fixed with leads to be led out of a furnace body, triangular wave currents with different amplitudes of 50Hz and 115mA are introduced into the amorphous wire for current annealing, and the current annealing is simultaneously carried out along with isothermal annealing. The heat preservation temperature of the heat treatment is 220 ℃, and the amorphous wire is subjected to heat treatment by adopting different heat preservation time.

The change of the amorphous wire rectangular ratio along with the heat preservation time is shown in figure 4, the amorphous wire annular rectangular ratio is gradually increased along with the increase of the heat preservation time, and the annular rectangular ratio of the amorphous wire is basically stabilized at about 0.975 after the heat preservation time reaches 2 hours; when the heat preservation time reaches 4h, the amorphous wire ring begins to descend towards the rectangular ratio; when the holding time is 5h, the squareness ratio is reduced to 0.95. In general, when the heat preservation time is 0.5h-5h, the annular rectangular ratio of the amorphous wire can reach more than 0.950.

Example 3

In this embodiment, two ends of a glass-coated amorphous wire having a length of 6cm are fixed on a refractory substrate (i.e., a non-metallic substrate), two ends are welded with fixed wires and led out of a furnace body, a triangular wave current of 50Hz and 115mA is applied to the amorphous wire to perform heat treatment, and heat preservation is performed simultaneously, with the heat preservation time being 2 hours.

The stress resistance change rate of the amorphous wire after the heat treatment was tested at 100kHz, and fig. 5 shows a graph of the stress resistance change rate of the amorphous wire according to the heat treatment temperature.

As can be seen from fig. 5, as the heat treatment temperature increases, the stress resistance change rate gradually increases, and when the heat treatment temperature reaches 220 ℃, the stress resistance change rate reaches the highest value, and the resistance change rate at 100kHz reaches 97%; as the heat treatment temperature continues to increase, the stress resistance change rate decreases slightly. As can be seen from fig. 5, when the heat treatment temperature is 150 ℃ to 300 ℃, the stress annealing increases the stress impedance change rate of the amorphous wire, enhances the magnetic anisotropy of the amorphous wire, and reduces or eliminates the residual stress inside the amorphous wire, so that the soft magnetic property of the amorphous wire is improved.

Example 4

In the embodiment, triangular wave currents with different frequencies of 50Hz-2kHz are applied to the amorphous wire for current annealing while heat preservation heat treatment is carried out on the amorphous wire, the current amplitude is 115mA, the heat preservation temperature of the heat treatment is 220 ℃, and the heat preservation time is 2 hours. The change of the amorphous wire rectangular ratio along with the triangular wave current frequency is shown in figure 6, the annular amorphous wire rectangular ratio is stabilized at about 0.97 along with the increase of the current frequency, and the main reason is that compared with the heat generated by the square wave wide pulse, the triangular wave has less heat brought by eddy current loss under the frequency of 50Hz-2kHz, and the temperature rise caused by frequency rising has no obvious change due to the flowing soaking of inert gas. However, at high frequency, eddy current loss is obvious, and wire heating and furnace temperature are superposed, so that the heat treatment effect is not good.

Similarly, when the conditions of the holding temperature and the heat treatment time are changed, the frequency (in the range of 50Hz-2 kHz) of the triangular wave current does not have great influence on the annular rectangular ratio of the amorphous wire.

When the frequency of the triangular wave current applied to the amorphous wire is 50Hz, the variation of the magnetic field sensitivity of the amorphous wire along with the hoop squareness ratio is shown in FIG. 7, the magnetic field sensitivity of the amorphous wire is gradually increased along with the increase of the hoop squareness ratio, and when the hoop squareness ratio is 0.97, the magnetic field sensitivity is up to 153% according to the magnetic impedance variation rate.

Comparative example 1

In the comparative example, only the amorphous wire is subjected to isothermal annealing heat treatment, the heat preservation temperature is 220 ℃, and the heat preservation time is 2 hours. The annular rectangular ratio of the amorphous wire is 0.818, and the magnetic impedance change rate is 43.3%. The amorphous wire magnetic field sensitivity reaches 93.5%.

Comparative example 2

In the comparative example, only the amorphous wire was subjected to current heat treatment with a 50Hz triangular current, the current amplitude was 115mA, and the heat treatment time was 2 hours. The annular rectangular ratio of the amorphous wire is 0.915, and the magnetic impedance change rate is 86%. The amorphous wire magnetic field sensitivity reaches 113%.

Comparative example 3

In the comparative example, two ends of a glass-coated amorphous wire with the length of 6cm are fixed on a refractory substrate, two ends of the glass-coated amorphous wire are welded and fixed with leads to the outside of a furnace body, argon protective gas is introduced into a furnace chamber, the temperature is kept at 220 ℃, a square wave current of 50Hz and a current I are applied to the amorphous wire_ac115mA, and the heat preservation time is 2 h. Here, the current annealing is performed simultaneously with the isothermal annealing. The annular rectangular ratio of the amorphous wire is less than 0.8, the magnetic impedance change rate is 80%, and the magnetic field sensitivity of the amorphous wire is very low.

In summary, the invention adopts a composite heat treatment method combining isothermal annealing and current annealing, mainly combines isothermal annealing and pulse current auxiliary heat treatment of amorphous wires to realize annular excitation and induced annular anisotropy of the amorphous wires, and compared with the single isothermal annealing heat treatment, the composite heat treatment method can realize temperature control, make the temperature treatment more uniform and achieve the effect of uniform temperature of the surface and the core of the wire material.

The above is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made to the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite heat treatment method for optimizing the magnetic performance of amorphous wires is characterized in that,

a composite heat treatment method adopting combination of isothermal annealing and current annealing, comprising the following steps: in the presence of protective atmosphere, heating the amorphous wire to a required temperature along with a furnace, and then carrying out heat preservation treatment, wherein during the heat preservation treatment, pulse current is applied to the amorphous wire so as to enable the amorphous wire to obtain required magnetic performance;

the temperature of the heat preservation heat treatment is the stress relief temperature of the amorphous wire, the heat preservation temperature of the heat preservation heat treatment is 150-300 ℃, and the heat preservation time is 0.5-5 h;

the pulse frequency of the pulse current is 50Hz-2kHz, and the amplitude of the pulse current is 50mA-150 mA;

during the heat preservation heat treatment, the amorphous wire is fixed on a non-metal matrix in a heating furnace, and the non-metal matrix is made of non-magnetic conductive and non-conductive materials;

the amorphous wire is a cobalt-based amorphous wire.

2. The thermal processing method of claim 1, wherein said pulsed current is a unidirectional pulsed current.

3. The thermal processing method of claim 1, wherein said pulse current is a triangular wave pulse.

4. The heat treatment method according to claim 1,

the electrifying time of the pulse current is 0.5h-5 h.

5. The heat treatment method according to claim 4,

the heat preservation time of the heat preservation heat treatment is the same as the electrifying time of the pulse current.

6. The heat treatment method according to any one of claims 1 to 5,

the amorphous wire is a round section wire or a thin strip wire.

7. The heat treatment method according to claim 6, wherein when the amorphous wire is a round-section wire, the diameter of the amorphous wire is 10 μm to 180 μm.

8. The heat treatment method according to any one of claims 1 to 5, wherein the protective atmosphere is any one of argon, nitrogen and hydrogen.

9. The heat treatment method according to any one of claims 1 to 5, wherein a wire length direction of the amorphous wire is coincident with a furnace body length direction of the heating furnace.

10. The heat treatment method according to claim 9, wherein the amorphous wire is placed in a middle region in the heating furnace, and a temperature difference at both ends of the amorphous wire is less than ± 1 ℃.

11. The heat-treating method according to any one of claims 1 to 5, wherein the sample is taken out and air-cooled to room temperature after the heat-treating incubation is completed.