CN114058798A - Flash annealing process and device for La-Fe-Si series alloy - Google Patents

Flash annealing process and device for La-Fe-Si series alloy Download PDF

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CN114058798A
CN114058798A CN202111425084.XA CN202111425084A CN114058798A CN 114058798 A CN114058798 A CN 114058798A CN 202111425084 A CN202111425084 A CN 202111425084A CN 114058798 A CN114058798 A CN 114058798A
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cooling
alloy
heating
alloy plate
flash annealing
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CN114058798B (en
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郑红星
杨元奎
邓凯
徐智帅
翟长生
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Yanbai Additive Zhizao Xuzhou Technology Co ltd
University of Shanghai for Science and Technology
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Yanbai Additive Zhizao Xuzhou Technology Co ltd
University of Shanghai for Science and Technology
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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26Methods of annealing
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34Methods of heating
    • C21D1/40Direct resistance heating
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00Heat treatment of ferrous alloys
    • C21D6/008Heat treatment of ferrous alloys containing Si
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/012Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials adapted for magnetic entropy change by magnetocaloric effect, e.g. used as magnetic refrigerating material
    • H01F1/015Metals or alloys

Abstract

The invention discloses a flash annealing process and a flash annealing device for La-Fe-Si series alloy, belonging to the technical field of alloy heat treatment. The process comprises the following steps: firstly, heating the alloy plate to 1150 ℃ at a heating rate of 5-10 ℃/s, and then preserving heat for 5-15 s; secondly, heating the alloy plate to 1185-1225 ℃ by applying pulse current, then cooling to 1150-1165 ℃, and circularly heating and cooling at the stage for 5-15 s; in this stage, the pulse current parameters are: the pulse width is 0.5-2 ms, the peak current is 1000-2000A, and the frequency is 5-100 Hz; and thirdly, cooling to 300 ℃ at a cooling rate of 50-100 ℃/s, and then furnace-cooling to room temperature. The device is a heat treatment device designed by matching with the process. The method can greatly reduce the heat treatment time of the La-Fe-Si alloy, reduce the heat treatment energy consumption and simultaneously improve the stability of the heat treatment effect of the La-Fe-Si alloy.

Description

Flash annealing process and device for La-Fe-Si series alloy
Technical Field
The invention belongs to the technical field of alloy heat treatment, and particularly relates to a flash annealing process and a flash annealing device for La-Fe-Si series alloy.
Background
The magnetic refrigeration technology is a mode for realizing refrigeration by utilizing the magnetocaloric effect of the solid-state magnetic refrigeration functional alloy, and has the advantages of low energy consumption, no pollution, high efficiency and the like compared with the traditional gas compression refrigeration mode. The light rare earth iron-based alloy La-Fe-Si is considered to be one of the room-temperature magnetic refrigeration functional alloys with the most commercial application prospect due to the excellent cost performance. However, the conventional casting method cannot directly prepare the magnetic refrigeration functional phase (La (Fe, Si) with large volume fraction and giant magnetocaloric effect)13Phase), which must be subsequently treated using a high temperature heat treatment process.
At present, the problems of long heat treatment time (60-100 h), high-temperature energy consumption (the heat treatment temperature is more than 1000 ℃) and the like exist in the heat treatment annealing process of the La-Fe-Si series alloy, and the commercial application of the system alloy is severely restricted. Therefore, how to make a scientific heat treatment process to shorten the heat treatment time and reduce the consumption of energy and resources in the heat treatment process becomes one of the key bottlenecks in the large-scale application of the La-Fe-Si alloy.
The conventional heat treatment temperature range for La-Fe-Si alloy is generally between 1000 and 1150 ℃, and if the temperature is continuously raised to over 1150 ℃, partial phases are remelted, and the alloy may be subjected to large-area melting. However, when the La-Fe-Si alloy is heat-treated at a temperature of 1000 to 1150 ℃, it is difficult to reduce the heat treatment time while ensuring the heat treatment effect.
For example, the Chinese patent application number is: CN201811113587.1, published date: the patent literature 1 month and 25 days in 2019 discloses a La-Fe-Si-Cu magnetic refrigeration material with excellent magnetocaloric property and short preparation period and a preparation method thereof, wherein the chemical general formula of the La-Fe-Si-Cu magnetic refrigeration material is (La)yFe13-zSiz)100-xCux,0<x is less than or equal to 50, y is less than or equal to 2 and is less than or equal to 1, and z is less than or equal to 10 and is more than or equal to 0. The preparation method comprises the following steps: (1) mixing La, Fe, Si and Cu according to the mass percentage of each element in the general formula; (2) under the protection of high-purity argon, repeatedly smelting, cooling and turning the prepared raw materials in a vacuum electric arc furnace for four times; (3) and carrying out high-temperature heat treatment on the cast ingot in a high-purity argon atmosphere and then quenching the cast ingot in cold water.
Compared with the traditional method, the preparation period of the La-Fe-Si magnetic refrigeration material is shortened, but the La-Fe-Si-Cu alloy after vacuum melting needs to be back flushed with high-purity argon gas of 0.01-0.03 MPa under the vacuum condition, and isothermal annealing is carried out at 1050 ℃ for 6 days to obtain a large amount of La (Fe, Si)13And the energy consumption in the heat treatment process is still large.
Also, for example, the Chinese patent application number is: CN201210239559.0, published date: patent literature on 2013, 4 and 17 months discloses La (Fe, Si) prepared by taking high-Ce industrial pure misch metal as a raw material13The basic magnetic refrigeration material has a chemical general formula as follows: la1-x(Ce,Pr,Nd)x(Fe1-p-qCopMnq)13-ySiyHaving NaZn of13And (4) a mold structure. The preparation method comprises the following steps: preparing La by smelting and annealing with high Ce industrial pure mixed rare earth as raw material1-x(Ce,Pr,Nd)x(Fe1-p-qCopMnq)13-ySiyA magnetic refrigeration material.
Although the invention reduces the preparation cost of the material, the heat treatment annealing process used by the invention is as follows: the smelted alloy ingot is processed at 1000 ℃ and the vacuum degree is less than 10-3Annealing for 60 days under the condition of Pa, and then quenching in liquid nitrogen, so that the whole heat treatment process is long in period,The cost is high.
Flash heat treatment annealing is a heat treatment process which heats an alloy to a certain temperature in a very short time and rapidly reduces the temperature after short-time heat preservation, and the process greatly reduces the heat treatment time while ensuring the heat treatment effect, thereby saving the energy consumption. However, no technology for specially applying flash heat treatment annealing to La-Fe-Si system alloy exists in the prior art, so that the actual process steps and corresponding parameters are difficult to determine, and flash heat treatment annealing to La-Fe-Si system alloy is difficult to realize well through the existing device.
Meanwhile, the applicant discovers that when researching the heat treatment process of the La-Fe-Si alloy, the heating temperature of the La-Fe-Si alloy is increased to 1185-1225 ℃ through the flash heat treatment process, the temperature is rapidly reduced to 1150-1165 ℃ after short-time heat preservation, and the large-area melting of the alloy can be avoided. However, when La-Fe-Si system alloy is heat-treated by this method, if the holding time is too short, it is difficult to prepare a large volume fraction of magnetic refrigeration functional phase (La (Fe, Si)13Phase), if the holding time is too long, the alloy may be melted in a large area. Moreover, the optimal heat preservation time is changed due to different shapes, sizes and heating modes of the alloy, so that the optimal heat preservation time of the La-Fe-Si alloy during heat treatment is difficult to scientifically set, and the heat treatment effect is unstable.
Disclosure of Invention
1. Problems to be solved
Aiming at the problems of imperfect heat treatment process and unsatisfactory heat treatment effect of the existing La-Fe-Si series alloy, the invention provides a flash annealing process of the La-Fe-Si series alloy, which can greatly reduce the heat treatment time of the La-Fe-Si series alloy, reduce the heat treatment energy consumption and simultaneously improve the stability of the heat treatment effect of the La-Fe-Si series alloy.
The invention also provides a flash annealing device for the La-Fe-Si alloy, which can be used for carrying out heat treatment on the La-Fe-Si alloy in the process so as to improve the performance of the La-Fe-Si alloy.
2. Technical scheme
In order to solve the above problems, the present invention adopts the following technical solutions.
A flash annealing process of La-Fe-Si series alloy comprises the following steps:
first, preheating stage
Heating the alloy plate to 1150 ℃ at the heating rate of 5-10 ℃/s, and then preserving heat for 5-15 s;
second, flash heating stage
Heating the alloy plate to 1185-1225 ℃ by applying pulse current, then cooling to 1150-1165 ℃, and circularly heating and cooling at the stage for 5-15 s; in this stage, the pulse current parameters are: the pulse width is 0.5-2 ms, the peak current is 1000-2000A, and the frequency is 5-100 Hz;
third, cooling stage
Cooling to 300 ℃ at a cooling rate of 50-100 ℃/s, and then furnace-cooling to room temperature.
As a further improvement of the technical scheme, in the second step, the average temperature rise rate is 7000-37500 ℃/s, and the average temperature drop rate is 100-5000 ℃/s.
As a further improvement of the technical scheme, the first step adopts a direct current heating mode, the power of a direct current power supply is kept constant after the heat preservation is finished, and the second step is carried out.
As a further improvement of the technical scheme, in the third step, the alloy plate is cooled by blowing cooling inert gas into the alloy plate.
As a further improvement of the technical scheme, the method also comprises the following steps: and C, performing phase content statistics and standard magnetic performance tests on the alloy plate treated in the step three.
As a further improvement of the technical scheme, the alloy plate is a La-Fe-Si alloy plate, and the thickness of the alloy plate is 0.5-2 mm.
As a further improvement of the technical scheme, the alloy sheet is an La-Fe-Si-X alloy sheet, and X is any one or more of RE, B, C, Co and H.
A flash annealing device of La-Fe-Si series alloy is used for the flash annealing process and comprises a vacuum cavity, a current heating mechanism, a graphite groove, a cooling mechanism and a pulse heating mechanism; the current heating mechanism is arranged in the vacuum cavity and used for electrifying and heating a graphite groove, and a space for placing an alloy plate is arranged in the graphite groove; the cooling mechanism is used for cooling the alloy plate in the graphite groove; and the coil of the pulse heating mechanism is wound on the surface of the alloy plate.
As a further improvement of the technical scheme, the cooling mechanism comprises an inert gas cylinder and a blowing nozzle, wherein the blowing nozzle is arranged above the graphite groove, and an inlet of the blowing nozzle is connected with the inert gas cylinder through a pipeline.
As a further improvement of the technical scheme, the coil is made of tungsten wires or molybdenum wires.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) compared with the conventional quartz tube packaging or vacuum indoor constant-temperature annealing treatment process method, the flash annealing process of the La-Fe-Si alloy greatly shortens the heat treatment time, can be completed within minutes, remarkably reduces the energy consumption in the heat treatment process, has higher practical value, particularly realizes the circulating flash temperature rise and temperature reduction of the alloy plate by pulse magnetic induction heating, can realize the local discontinuous flash melting, flash high-temperature synthesis and flash solidification in the alloy plate on the premise of ensuring that the alloy plate is not integrally melted in a large area, and solves the problem that the conventional constant-temperature heat treatment process method cannot heat the La-Fe-Si alloy plate to the temperature near 1200 ℃ so as to quickly obtain the large-proportion La (Fe, Si)13The problem of phase is solved, the problem that the optimal heat preservation time of the La-Fe-Si alloy plate in the flash heat treatment process is difficult to scientifically formulate is solved, the stability of the heat treatment effect of the La-Fe-Si alloy is improved, and the prepared La-Fe-Si alloy plate is excellent in magnetic refrigeration performance;
(2) according to the flash annealing device for the La-Fe-Si alloy, the structure of the device is uniquely designed, so that the flash annealing process can be well realized, and the La-Fe-Si alloy with excellent performance is prepared.
Drawings
FIG. 1 is a schematic structural view of a flash annealing apparatus for La-Fe-Si system alloy according to the present invention;
FIG. 2 is a pulse current input function of a flash annealing process of the La-Fe-Si system alloy of the present invention;
FIG. 3 is a schematic diagram of a flash annealing process of the La-Fe-Si system alloy of the present invention;
FIG. 4 is a SEM photograph of a heat-treated sample of example 1 of the present invention;
FIG. 5 is a graph showing an isothermal magnetization-demagnetization curve of a heat-treated sample according to example 1 of the present invention;
FIG. 6 is a schematic diagram showing isothermal magnetic entropy change of a heat-treated sample according to example 1 of the present invention;
FIG. 7 is a SEM photograph of a heat-treated sample of example 2 of the present invention;
FIG. 8 is a graph showing isothermal magnetization-demagnetization curves of a heat-treated sample according to example 2 of the present invention;
FIG. 9 is a schematic diagram showing isothermal magnetic entropy change of a heat-treated sample in example 2 of the present invention;
FIG. 10 is a SEM photograph of a heat-treated sample of example 3 of the present invention;
FIG. 11 is a graph showing isothermal magnetization-demagnetization curves of heat-treated samples according to example 3 of the present invention;
FIG. 12 is a schematic diagram showing isothermal magnetic entropy change of a heat-treated sample according to example 3 of the present invention;
in the figure: 1. a vacuum chamber; 2. a current heating mechanism; 3. a graphite groove; 4. a cooling mechanism; 5. a pulse heating mechanism; 6. alloy plate.
Detailed Description
The invention is further described with reference to specific embodiments and the accompanying drawings.
A flash annealing process of La-Fe-Si series alloy is used for carrying out high-temperature heat treatment on the La-Fe-Si series alloy to prepare the La-Fe-Si series alloy with excellent performance, but the flash annealing process of the invention is difficult to be perfectly realized by adopting the existing heat treatment device, and aiming at the problem, the invention designs a flash annealing device of the La-Fe-Si series alloy in a matching way.
As shown in fig. 1, the apparatus includes a vacuum chamber 1, a current heating mechanism 2, a graphite bath 3, a cooling mechanism 4, and a pulse heating mechanism 5. The current heating mechanism 2 is arranged in the vacuum cavity 1 and used for heating the graphite groove 3 in an electrified mode, and a space for placing the alloy plate 6 is arranged in the graphite groove 4. The cooling mechanism 4 is used for cooling the alloy plate 6 in the graphite groove 4, and the coil of the pulse heating mechanism 5 is wound on the surface of the alloy plate 6.
Specifically, the current heating mechanism 2 adopts a water-cooling copper electrode of an external power supply, the graphite groove 3 is fixedly arranged between the water-cooling copper electrodes, two ends of the graphite groove are fixedly connected with the copper electrodes, and the graphite groove 3 can be heated after the power supply connected with the water-cooling copper electrode is started. The graphite channels 3 may adopt the following arrangement: through holes penetrating through two opposite side surfaces of the graphite groove 3 are formed in the graphite groove along the width direction of the graphite groove, and before heat treatment work is started, the alloy plate 6 is inserted into the through holes and then the graphite groove 3 is placed between the water-cooling copper electrodes to be fixed. The cooling mechanism 4 comprises an inert gas cylinder and a blowing nozzle, the blowing nozzle is fixedly arranged at the top end of the vacuum cavity 1 above the graphite groove 3, an inlet of the blowing nozzle is connected with the inert gas cylinder through a pipeline, and the inert gas adopts common inert gases such as nitrogen, argon and the like. The pulse heating mechanism 5 is pulse magnetic induction heating, the coil material adopts tungsten wire or molybdenum wire, before heating, the outer surface of the alloy plate 6 is wound with the tungsten wire or molybdenum wire and then is placed in the graphite groove 3.
It is worth mentioning that in order to feed back the heating temperature in time and control the current heating mechanism 2 to adjust the heating temperature of the graphite bath according to the feedback temperature, the invention is provided with a hole groove in the central area of the bottom of the graphite bath 3, and a thermocouple is inserted into the hole groove and is externally connected with a temperature display device.
When the flash annealing device is adopted, the flash annealing process comprises the following steps of firstly, placing a La-Fe-Si alloy plate with the thickness of 0.5-2 mm, the outer surface of which is wound with a tungsten wire or a molybdenum wire, in a graphite groove 3, fixedly connecting two ends of the graphite groove 3 with a current heating mechanism 2, inserting a thermocouple into a bottom hole groove of the graphite groove 3, and then entering a heat treatment part, wherein the preparation part comprises the following specific steps:
first, preheating stage
And the current heating mechanism 2 is connected with a direct current power supply to heat the graphite groove 3, the temperature of the alloy plate 6 is raised to 1150 ℃ at the temperature raising rate of 5-10 ℃/s, the heat is preserved for 5-15 s, then the power of the direct current power supply is kept constant, and the next stage is started.
Second, flash heating stage
And (3) switching on a pulse magnetic induction power supply to the tungsten wire or the molybdenum wire surrounding the alloy plate 6, so that the alloy plate is heated to 1185-1225 ℃ in a flash manner, then rapidly cooling to 1150-1165 ℃, and circularly heating and cooling for 5-15 s at the stage. The high-frequency pulse current in the tungsten wire or the molybdenum wire can generate a pulse type skin-friendly heating effect on the surface of the alloy plate 6. The pulse magnetic induction heating power supply has three input ends, namely pulse width, peak current and pulse frequency, and parameters of the input ends are set in the supply equipment of the pulse heating power supply before heating begins, so that a certain current input function can be generated, and a pulse current waveform as shown in fig. 2 is generated. In this stage, the pulse current parameters are: the pulse width is 0.5-2 ms, the peak current is 1000-2000A, and the frequency is 5-100 Hz.
As shown in FIG. 2, tpFor the pulse width, i.e. the duration of the arrival of the pulse current within a pulse period T, at TpAnd in the section, the pulse current enables the alloy plate to generate a pulse skin-seeking heating effect, and the alloy plate is subjected to heat treatment. f is pulse frequency, the pulse period T is 1/f, T-TpThe time when the pulse current is 0 in a pulse period T, namely the cooling stage in the flash heat treatment process, is adjusted by f and TpThe minimum temperature during the flash heat treatment can be controlled. I ispFor peak current, the ratio of the peak to the trough of the current is 1: 0.5 by adjusting the peak current IpCan control the highest temperature of the flash heat treatment.
When a pulse current comes, the temperature rises, so the maximum heating temperature is controlled by the peak current and the pulse width, and after the pulse current passes, namely when the pulse current is 0, the temperature falls, so the minimum temperature is controlled by the pulse width and the pulse period (pulse frequency), and the longer the pulse period, the longer the cooling time, and the lower the minimum temperature.
It should be noted that, because the pulse current is not uniform in magnitude during heating, the specific temperature increase and decrease rate during the flash heating stage is not constant and is difficult to control, so the method controls the maximum temperature and the minimum temperature that can be reached in one pulse period. In the stage, the average heating rate can be calculated to be 7000-37500 ℃/s according to the pulse width and the highest temperature, and the average cooling rate can be calculated to be 100-5000 ℃/s according to the pulse period and the lowest temperature.
The alloy plate is processed by the pulse magnetic induction heating mode of flash cycle temperature rise and temperature fall, the duration time is not strictly limited, and the situation that the optimal heat preservation time is difficult to control in the conventional flash heat treatment heating is not existed. The reason is that the duration of the pulse magnetic induction heating is prolonged, the times of the heat treatment are increased, and the single heat treatment process does not stay for too long time at the highest temperature, so that each heat treatment process is safe, and even if the duration is increased, the times of the heat treatment are increased, so that the whole process is safe, the condition of integral melting of the alloy cannot occur, and the heat treatment effect is good. The duration of the conventional flash heat treatment is kept at the highest temperature, and the alloy can be integrally melted after being slightly prolonged.
In this stage, the pulse power supply device can be realized by any commercially available device, and the specific structure thereof is not described in detail.
Third, cooling stage
And (3) closing the pulse magnetic induction power supply, starting cooling inert gas to blow the alloy plate 6, cooling to 300 ℃ at a cooling rate of 50-100 ℃/s, and then cooling to room temperature in the furnace. Staged cooling is used because cooling to room temperature at a constant cooling rate wastes cooling gas and thus the furnace cools to room temperature after cooling to 300 c.
Fourthly, performing phase content statistics and standard magnetic performance tests on the alloy plate processed in the third step.
Compared with the conventional quartz tube packaging or vacuum packaging processThe process method for constant-temperature annealing treatment in the hollow chamber greatly shortens the heat treatment time, can be completed in a few minutes, remarkably reduces the energy consumption in the heat treatment process, has higher practical value, particularly realizes the circulating flash temperature rise and the temperature reduction of the alloy plate by pulse magnetic induction heating, can realize the local discontinuous flash melting, the flash high-temperature synthesis and the flash solidification in the alloy plate on the premise of ensuring that the alloy plate is not integrally melted in a large area, and solves the problem that the conventional constant-temperature heat treatment process method cannot heat the La-Fe-Si alloy plate to the temperature near 1200 ℃ so as to quickly obtain the large-proportion La (Fe, Si)13The problem of phase is solved, the problem that the optimal heat preservation time of the La-Fe-Si alloy plate in the flash heat treatment process is difficult to scientifically formulate is solved, the stability of the heat treatment effect of the La-Fe-Si alloy is improved, and the prepared La-Fe-Si alloy plate is excellent in magnetic refrigeration performance.
Specific examples are given below.
Example 1
Selecting LaFe for heat treatment sample11.6Si1.4The alloy plate is 0.5mm in thickness and comprises the following specific processes:
firstly, LaFe with a thickness of 0.5mm and with tungsten wire or molybdenum wire wound on the outer surface11.6Si1.4Alloy plate 6 is arranged in graphite groove 3, and 3 both ends of graphite groove and copper electrode fixed connection to with 3 both ends of graphite groove and 2 fixed connection of electric current heating mechanism, and insert the thermocouple in the bottom hole groove of graphite groove 3, then get into the thermal treatment part, specifically as follows:
first, preheating stage
The current heating mechanism 2 is connected with a direct current power supply to heat the graphite groove 3, the temperature of the alloy plate 6 is raised to 1150 ℃ from room temperature at the temperature raising rate of 5 ℃/s, the temperature is kept for 10s, then the power of the direct current power supply is kept constant, and the next stage is started.
Second, flash heating stage
And (3) connecting a pulse magnetic induction power supply with a tungsten wire or a molybdenum wire surrounding the alloy plate 6 to enable the alloy plate to be heated to 1185 ℃ in a flash speed, then rapidly cooling to 1150 ℃, and circularly heating and cooling for 5s at the stage. In this stage, the pulse current parameters are: pulse width 0.5ms, peak current 1000A, frequency 5 Hz. The highest temperature which can be reached in the flash cycle heating process of the alloy plate is 1185 ℃, and the lowest flash cycle cooling temperature is 1150 ℃.
Third, cooling stage
And (3) closing the pulse magnetic induction power supply, starting the cooling inert gas to blow the alloy plate 6, cooling to 300 ℃ at the cooling rate of 50 ℃/s, and then cooling to room temperature in the furnace.
Fourthly, performing phase content statistics and standard magnetic performance tests on the alloy plate processed in the third step.
As a result, FIG. 4 is a photograph of the structure of the heat-treated sample of this example under a scanning electron microscope, and it can be seen that the heat-treated sample formed a large number of La (Fe, Si)13The image processing software ipp is adopted to carry out magnetic refrigeration on the functional phase La (Fe, Si)13Phase content statistics is carried out on the phases to obtain La (Fe, Si)13The volume fraction of the phase is more than 95%, then the sample is subjected to magnetic performance test, the test result is respectively shown in fig. 5 and fig. 6, the maximum magnetic entropy change of the sample under the 3T magnetic field reaches 27J/(kg. K), and the corresponding effective refrigerating capacity reaches 227.10J/kg.
Example 2
Selecting LaFe for heat treatment sample11.6Si1.4B0.06The alloy plate is 1mm thick, and the specific heat treatment steps are as follows:
firstly, 1mm thick LaFe with tungsten or molybdenum wire wound on the outer surface11.6Si1.4B0.06Alloy plate 6 is arranged in graphite groove 3, and 3 both ends of graphite groove and copper electrode fixed connection to with 3 both ends of graphite groove and 2 fixed connection of electric current heating mechanism, and insert the thermocouple in the bottom hole groove of graphite groove 3, then get into the thermal treatment part, specifically as follows:
first, preheating stage
The current heating mechanism 2 is connected with a direct current power supply to heat the graphite groove 3, the temperature of the alloy plate 6 is raised to 1150 ℃ from room temperature at the heating rate of 7 ℃/s, the heat is preserved for 10s, then the power of the direct current power supply is kept constant, and the next stage is started.
Second, flash heating stage
And (3) connecting a pulse magnetic induction power supply to the tungsten wire or the molybdenum wire surrounding the alloy plate 6 to enable the alloy plate to be heated to 1200 ℃ in a flash manner, then rapidly cooling to 1160 ℃, and circularly heating and cooling for 10s at the stage. In this stage, the pulse current parameters are: pulse width 1ms, peak current 1500A, frequency 25 Hz. The highest temperature which can be reached in the flash cycle heating process of the alloy plate is 1200 ℃, and the lowest temperature of flash cycle cooling is 1160 ℃.
Third, cooling stage
And (3) closing the pulse magnetic induction power supply, starting the cooling inert gas to blow the alloy plate 6, cooling to 300 ℃ at the cooling rate of 70 ℃/s, and then cooling to room temperature in the furnace.
Fourthly, performing phase content statistics and standard magnetic performance tests on the alloy plate processed in the third step.
As a result, FIG. 7 is a photograph of a structure of a heat-treated sample of this example under a scanning electron microscope, and it can be seen from the photograph that the heat-treated sample formed a large number of La (Fe, Si)13The image processing software ipp is adopted to carry out magnetic refrigeration on the functional phase La (Fe, Si)13Phase content statistics is carried out on the phases to obtain La (Fe, Si)13The volume fraction of the phase is more than 94%, then the sample is subjected to magnetic performance test, the test result is respectively shown in fig. 8 and fig. 9, the maximum magnetic entropy change of the sample under the 3T magnetic field reaches 21J/(kg. K), and the corresponding effective refrigerating capacity reaches 243.10J/kg.
Example 3
Selecting LaFe for heat treatment sample11.6Si1.4C0.06The alloy plate is 2mm thick, and the specific heat treatment steps are as follows:
firstly, 2mm thick LaFe with tungsten or molybdenum wire wound on the outer surface11.6Si1.4C0.06Alloy plate 6 is arranged in graphite groove 3, and 3 both ends of graphite groove and copper electrode fixed connection to with 3 both ends of graphite groove and 2 fixed connection of electric current heating mechanism, and insert the thermocouple in the bottom hole groove of graphite groove 3, then get into the thermal treatment part, specifically as follows:
first, preheating stage
The current heating mechanism 2 is connected with a direct current power supply to heat the graphite groove 3, the temperature of the alloy plate 6 is raised to 1150 ℃ from room temperature at the heating rate of 10 ℃/s, the heat is preserved for 10s, then the power of the direct current power supply is kept constant, and the next stage is started.
Second, flash heating stage
And (3) connecting a pulse magnetic induction power supply to the tungsten wire or the molybdenum wire surrounding the alloy plate 6 to enable the alloy plate to be heated to 1225 ℃ in a flash manner, then rapidly cooling to 1165 ℃, and circularly heating and cooling for 15s at the stage. In this stage, the pulse current parameters are: pulse width 2ms, peak current 2000A, frequency 50 Hz. The highest temperature which can be reached in the flash cycle heating process of the alloy plate is 1225 ℃, and the lowest temperature of flash cycle cooling is 1165 ℃.
Third, cooling stage
And (3) closing the pulse magnetic induction power supply, starting the cooling inert gas to blow the alloy plate 6, cooling to 300 ℃ at the cooling rate of 100 ℃/s, and then cooling to room temperature in the furnace.
Fourthly, performing phase content statistics and standard magnetic performance tests on the alloy plate processed in the third step.
As a result, FIG. 10 is a photograph of the structure of the heat-treated sample of this example under a scanning electron microscope, and it can be seen that the heat-treated sample formed a large number of La (Fe, Si)13The image processing software ipp is adopted to carry out magnetic refrigeration on the functional phase La (Fe, Si)13Phase content statistics is carried out on the phases to obtain La (Fe, Si)13The volume fraction of the phase is more than 95%, then the sample is subjected to magnetic performance test, the test result is respectively shown in fig. 11 and fig. 12, the maximum magnetic entropy change of the sample under a 3T magnetic field reaches 22.5J/(kg. K), and the corresponding effective refrigerating capacity reaches 257.10J/kg.
The examples described herein are merely illustrative of the preferred embodiments of the present invention and do not limit the spirit and scope of the present invention, and various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A flash annealing process of La-Fe-Si series alloy comprises the following steps:
first, preheating stage
Heating the alloy plate to 1150 ℃ at the heating rate of 5-10 ℃/s, and then preserving heat for 5-15 s;
second, flash heating stage
Heating the alloy plate to 1185-1225 ℃ by applying pulse current, then cooling to 1150-1165 ℃, and circularly heating and cooling at the stage for 5-15 s; in this stage, the pulse current parameters are: the pulse width is 0.5-2 ms, the peak current is 1000-2000A, and the frequency is 5-100 Hz.
Third, cooling stage
Cooling to 300 ℃ at a cooling rate of 50-100 ℃/s, and then furnace-cooling to room temperature.
2. Flash annealing process of La-Fe-Si based alloys according to claim 1, characterized in that: in the second step, the average temperature rise rate is 7000-37500 ℃/s, and the average temperature drop rate is 100-5000 ℃/s.
3. Flash annealing process of La-Fe-Si based alloys according to claim 2, characterized in that: and step one, adopting a direct current heating mode, keeping the power of a direct current power supply constant after heat preservation is finished, and entering a step two stage.
4. The flash annealing process of La-Fe-Si based alloy according to claim 3, characterized in that: and in the third step, the alloy plate is cooled by blowing cooling inert gas into the alloy plate.
5. Flash annealing process of a La-Fe-Si based alloy according to any of the claims 1 to 4, characterized in that: the method also comprises the following four steps: and C, performing phase content statistics and standard magnetic performance tests on the alloy plate treated in the step three.
6. Flash annealing process of a La-Fe-Si based alloy according to any of the claims 1 to 4, characterized in that: the alloy sheet is a La-Fe-Si alloy sheet with a thickness of 0.5 to 2 mm.
7. Flash annealing process of La-Fe-Si based alloys according to claim 6, characterized in that: the alloy sheet is La-Fe-Si-X alloy sheet, and X is any one or more of RE, B, C, Co and H.
8. A flash annealing apparatus of La-Fe-Si based alloy for use in the flash annealing process of any one of claims 1 to 7, characterized in that: comprises a vacuum cavity (1), a current heating mechanism (2), a graphite groove (3), a cooling mechanism (4) and a pulse heating mechanism (5); the current heating mechanism (2) is arranged in the vacuum cavity (1) and is used for electrifying and heating the graphite groove (3), and a space for placing an alloy plate (6) is arranged in the graphite groove (4); the cooling mechanism (4) is used for cooling the alloy plate (6) in the graphite groove (4); and the coil of the pulse heating mechanism (5) is wound on the surface of the alloy plate (6).
9. The flash annealing device of La-Fe-Si based alloy according to claim 8, wherein: the cooling mechanism (4) comprises an inert gas cylinder and a blowing nozzle, the blowing nozzle is arranged above the graphite groove (3), and an inlet of the blowing nozzle is connected with the inert gas cylinder through a pipeline.
10. The flash annealing device of La-Fe-Si based alloy according to claim 9, wherein: the coil is made of tungsten wires or molybdenum wires.
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