Annealing process of soft magnetic alloy

Abstract

The application discloses an annealing process for soft magnetic alloy, comprising: purifying and deeply drying the obtained protective hydrogen for pretreatment; establishing a vacuum environment in an annealing furnace and performing low-temperature pre-baking treatment on a soft magnetic alloy workpiece to be treated; rapidly feeding the protective hydrogen into the annealing furnace to build pressure, and performing gas replacement in an inlet-outlet gas dynamic balance mode; heating to a target annealing temperature interval, and maintaining the inlet-outlet gas dynamic balance mode during the heating and heat preservation stages; finally, performing multi-stage cooling operation, including a first cooling stage of canceling the dynamic balance and performing pulse exhaust by using exhaust pressure threshold control, and second and third cooling stages of restoring the inlet-outlet gas dynamic balance and performing forced fast cooling with large flow. The application significantly improves the consistency of magnetic properties and mechanical toughness of batch soft magnetic alloy products.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for iron-cobalt-vanadium soft magnetic alloys, and particularly to an annealing process for soft magnetic alloys. Background Technology

[0002] 1J22 (Fe-50Co-2V) is a commercially available soft magnetic alloy with extremely high saturation magnetic induction, widely used in key components such as aerospace motors, electromagnet poles, and precision sensors. Its comprehensive properties, such as permeability, coercivity, and plasticity, are highly dependent on the grain structure control, residual stress elimination, and material purity during the annealing process.

[0003] However, traditional heat treatment processes (such as conventional vacuum annealing or conventional atmosphere-protected annealing) often have serious limitations. Because traditional processes often employ static or imprecisely time-controlled annealing environments, they struggle to provide sustained and efficient microscopic impurity driving and removal capabilities during high-temperature annealing. This leads to the easy segregation of interstitial impurities such as carbon, oxygen, and sulfur at grain boundaries, resulting in magnetic domain pinning effects, which increases the material's coercivity and decreases its initial permeability. Simultaneously, the lack of precise dynamic control over fluid convection heat transfer and cooling rates throughout the entire heat treatment process results in uneven temperature field distribution within the furnace. The material is prone to developing significant internal stress due to uneven heating and deformation, and it is difficult to effectively prevent the precipitation of harmful brittle phases during subsequent cooling across specific temperature zones. This makes annealed workpieces highly susceptible to oxidation and embrittlement, leading to drastic fluctuations in grain structure, residual stress, and impurity content during mass production, resulting in large dispersion in magnetic properties and difficulty in guaranteeing yield.

[0004] In summary, traditional heat treatment processes struggle to achieve both deep purification and effective control of temperature field consistency and microstructure evolution throughout the entire heat treatment process, making it impossible to consistently obtain soft magnetic alloy workpieces with high magnetic properties, high microstructure consistency, and low brittleness. Summary of the Invention

[0005] The main objective of this invention is to propose a soft magnetic alloy annealing process, which aims to solve the problem that traditional heat treatment processes cannot simultaneously achieve deep purification and full-process microstructure control, resulting in poor magnetic properties and microstructure consistency, as well as high brittleness of soft magnetic alloy workpieces.

[0006] To achieve the above objectives, the soft magnetic alloy annealing process proposed in this invention includes:

[0007] Hydrogen is obtained and pretreated to obtain protective hydrogen that meets the preset purity and dew point indicators.

[0008] A vacuum environment is established in an annealing furnace containing a soft magnetic alloy workpiece to be processed, and a pre-baking treatment is performed on the soft magnetic alloy workpiece under the vacuum environment to remove moisture and impurities from the surface of the soft magnetic alloy workpiece.

[0009] The protective hydrogen gas is introduced into the annealing furnace to establish a first slightly positive pressure atmosphere inside the annealing furnace;

[0010] The furnace temperature inside the annealing furnace is raised to the target annealing temperature range, and protective hydrogen is introduced in a dynamic balance manner during the heating stage to establish a second micro-positive pressure atmosphere inside the annealing furnace.

[0011] The furnace is held at the target annealing temperature range for a first duration. During the holding period, the protective hydrogen is introduced in a dynamic balance manner to establish a third micro-positive pressure atmosphere in the annealing furnace with a furnace pressure lower than the second micro-positive pressure atmosphere.

[0012] After the heat preservation stage, a multi-stage cooling operation is performed on the annealing furnace to obtain the annealed soft magnetic alloy workpiece; wherein, the multi-stage cooling operation includes:

[0013] First cooling stage: Cooling to the second temperature range at a first cooling rate and holding at the temperature for a second duration, wherein the dynamic balance mode of inlet and outlet gas is cancelled during the first cooling stage, and the supply of protective hydrogen is maintained by exhaust pressure threshold control mode.

[0014] Second cooling stage: Cooling from the second temperature range to the third temperature range at a second cooling rate greater than the first cooling rate, wherein the supply of protective hydrogen is restored and maintained by the dynamic balance of inlet and outlet gas during the second cooling stage.

[0015] The third cooling stage: the temperature is reduced from the third temperature range to the furnace exit temperature at a third cooling rate, wherein the supply of protective hydrogen is maintained by the dynamic balance of inlet and outlet gas in the third cooling stage.

[0016] In one embodiment, hydrogen gas is obtained and pretreated to obtain protective hydrogen gas that meets preset purity and dew point indicators, including:

[0017] An initial hydrogen source is obtained, and phase separation and filtration operations are performed on the initial hydrogen source to remove liquid water and solid impurities from the initial hydrogen source and obtain intermediate hydrogen.

[0018] The intermediate hydrogen is subjected to a deep adsorption drying process to remove trace amounts of residual moisture from the intermediate hydrogen, thereby obtaining the protective hydrogen.

[0019] The preset purity index is a purity of not less than 99.999%, and the preset dew point index is a dew point of not higher than -40℃.

[0020] In one embodiment, after obtaining the protective hydrogen gas and before introducing the protective hydrogen gas into the annealing furnace, the process further includes:

[0021] Online dew point monitoring is performed on the protective hydrogen to obtain the real-time dew point characteristic value of the protective hydrogen;

[0022] The real-time dew point feature value is compared and evaluated with the preset dew point index;

[0023] In response to the evaluation result that the real-time dew point characteristic value deviates from the preset dew point index, a gas supply status intervention operation is triggered and executed to restrict hydrogen that does not meet the index from entering the annealing furnace.

[0024] In one embodiment, a vacuum environment is established within an annealing furnace containing a soft magnetic alloy workpiece to be processed, and a pre-baking treatment is performed on the soft magnetic alloy under said vacuum environment, including:

[0025] The absolute vacuum level inside the annealing furnace is controlled to be below 1.0 × 10⁻⁶. -3 Pa;

[0026] The soft magnetic alloy workpiece to be treated is heated to 150°C to 200°C at a heating rate of 5°C / min to 8°C / min, and held at that temperature for 1 hour to 2 hours to remove moisture and impurities from the surface of the soft magnetic alloy workpiece.

[0027] In one embodiment, the protective hydrogen gas is introduced into the annealing furnace to establish a first slightly positive pressure atmosphere within the annealing furnace, including:

[0028] The protective hydrogen gas is introduced into the annealing furnace, and the furnace pressure is increased to the initial slightly positive pressure range within 10 minutes, wherein the furnace pressure corresponding to the initial slightly positive pressure range is between 3 kPa and 5 kPa.

[0029] After reaching the initial slightly positive pressure range, the gas inlet and outlet dynamic balance method is adopted to introduce protective hydrogen at an inlet flow rate of 10 L / min to 15 L / min based on the furnace volume per cubic meter to perform gas replacement operation, so as to establish the first slightly positive pressure atmosphere with a furnace pressure of 5 kPa to 10 kPa in the annealing furnace.

[0030] In one embodiment, the furnace temperature of the annealing furnace is raised to the target annealing temperature range, and protective hydrogen is introduced during the heating stage using a dynamic balance of inlet and outlet gases to establish a second slightly positive pressure atmosphere within the annealing furnace, including:

[0031] The furnace temperature is raised to the target annealing temperature range of 850°C to 890°C at a heating rate of 5°C / min to 10°C / min.

[0032] During the heating stage, the gas flow rate is adjusted to 20 L / min to 25 L / min per cubic meter of furnace volume, and the protective hydrogen is introduced in a dynamic balance manner to establish a second slightly positive pressure atmosphere with a furnace pressure of 8 kPa to 12 kPa in the annealing furnace.

[0033] In one embodiment, the furnace is held at the target annealing temperature range for a first duration. During the holding period, protective hydrogen is introduced in a manner that maintains the dynamic balance between the incoming and outgoing gases, thereby establishing a third slightly positive pressure atmosphere in the annealing furnace with a furnace pressure lower than the second slightly positive pressure atmosphere. This includes:

[0034] After entering the heat preservation stage, the air inlet flow rate of the annealing furnace is reduced from the air inlet flow rate during the heating stage to 6 L / min to 8 L / min per cubic meter of furnace volume, so as to establish the third micro-positive pressure atmosphere with a furnace pressure of 2 kPa to 3 kPa in the annealing furnace.

[0035] The first duration ranges from 4 to 6 hours, and for every 1 kilogram increase in the weight of the soft magnetic alloy workpiece to be processed based on the preset benchmark weight, the corresponding first duration increases linearly by 5 minutes proportionally to the preset benchmark duration.

[0036] In one embodiment, the first cooling rate is 100°C / min to 150°C / min, the second temperature range is 740°C to 760°C, and the second duration is 1 hour to 2 hours; and

[0037] The supply of protective hydrogen is maintained by using an exhaust pressure threshold control method, including: setting the opening pressure threshold of the exhaust solenoid valve to 8 kPa to 10 kPa, setting the closing pressure threshold of the exhaust solenoid valve to 2 kPa to 3 kPa, and adjusting the inlet flow rate of the protective hydrogen to 3 L / min to 6 L / min per cubic meter of furnace volume.

[0038] In one embodiment, the second cooling rate is 250°C / min to 290°C / min, and the third temperature range is 440°C to 460°C; and

[0039] The supply of protective hydrogen is restored and maintained in the second cooling stage using the dynamic balance of inlet and outlet gas, including: maintaining the furnace pressure at 4 kPa to 6 kPa, and the inlet flow rate of the protective hydrogen is 10 L / min to 15 L / min per cubic meter of furnace volume.

[0040] In one embodiment, the third cooling rate is 220°C / min to 260°C / min, and the furnace exit temperature is not higher than 150°C; and

[0041] In the third cooling stage, the supply of protective hydrogen is maintained by the dynamic balance of inlet and outlet gas, including: maintaining the furnace pressure at 6 kPa to 8 kPa, and the inlet flow rate of the protective hydrogen is 15 L / min to 20 L / min per cubic meter of furnace volume.

[0042] The soft magnetic alloy annealing process described in this application has the following beneficial effects:

[0043] 1. Deep purification of the alloy was achieved through a closed-loop system of high-purity hydrogen atmosphere throughout the entire process.

[0044] 2. Through multi-stage dynamic coupling control of temperature, pressure and flow, the precipitation of harmful phases is precisely suppressed.

[0045] 3. By employing a differentiated pressure control strategy, both temperature field uniformity and hydrogen embrittlement eradication are achieved.

[0046] 4. The active furnace pressure compensation mechanism ensures seamless connection of atmosphere protection across the entire temperature range.

[0047] 5. The strong convective heat transfer characteristics of hydrogen and the synergistic effect of staged pressure-flow regulation ensured the high consistency of magnetic properties of batch products. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of an embodiment of the soft magnetic alloy annealing process of the present invention.

[0050] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0052] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0053] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0054] This invention proposes a soft magnetic alloy annealing process, which is mainly used to heat-treat and control soft magnetic alloys with high saturation magnetic induction intensity such as 1J22, so as to achieve deep purification of the material, complete stress release and suppression of harmful brittle phases, thereby stably obtaining annealed soft magnetic alloy workpieces with high permeability, low coercivity, low brittleness and high batch consistency.

[0055] In embodiments of the present invention, such as Figure 1 As shown, the annealing process for this soft magnetic alloy includes the following steps:

[0056] S10. Obtain hydrogen and pre-treat it to obtain protective hydrogen that meets the preset purity index and preset dew point index.

[0057] Specifically, in the embodiments of this invention, the soft magnetic alloy workpieces to be processed mentioned above and below are all based on "1J22 soft magnetic alloy" as a typical example for process development. 1J22 soft magnetic alloy, as a high-saturation magnetic induction iron-cobalt-vanadium soft magnetic alloy, exhibits extremely high sensitivity to the purity of the atmosphere and the accuracy of temperature control throughout the heat treatment process. However, those skilled in the art should understand that "1J22 soft magnetic alloy" is only used here as a specific example to explain the process mechanism of this invention. The soft magnetic alloy annealing process of this invention is not only applicable to 1J22 soft magnetic alloy, but also to other iron-cobalt-based, iron-nickel-based, and other similar iron-cobalt-vanadium soft magnetic alloy materials that have high purity requirements, are prone to grain boundary oxidation segregation, or are sensitive to the precipitation of harmful phases.

[0058] In this embodiment, the 1J22 iron-cobalt-vanadium soft magnetic alloy is extremely sensitive to impurities in the atmosphere (such as oxygen, water vapor, carbon monoxide, etc.) during the high-temperature annealing stage. Even trace amounts of microscopic impurities can cause micro-oxidation on the alloy surface, and more seriously, induce side reactions such as hydrogen embrittlement and grain boundary pinning at high temperatures, severely pinning magnetic domain walls and leading to a dramatic increase in the coercivity and a significant decrease in the initial permeability of the final workpiece. Therefore, before the hydrogen gas is fed into the annealing furnace, it must undergo multi-stage deep pretreatment to ensure that its purity indicators in all dimensions reach extremely high physicochemical standards.

[0059] In some optional embodiments, the specific process flow of step S10 above can be achieved collaboratively through steps S11 to S12:

[0060] S11. Obtain an initial hydrogen source and perform phase separation and filtration operations on the initial hydrogen source to remove liquid water and solid impurities from the initial hydrogen source and obtain intermediate hydrogen.

[0061] Specifically, the initial hydrogen source can be an industrial high-purity hydrogen column, a containerized gas source, or a hydrogen flow directly supplied from a hydrogen production station. Although the initial hydrogen source has a certain basic purity, it will inevitably introduce trace amounts of free water, suspended condensate, and solid particulate impurities such as rust and microparticles that are liquid at room temperature and pressure during its storage, filling, or pipeline transportation.

[0062] To eliminate these macroscopic and microscopic impurities, in this embodiment, the initial hydrogen source is first introduced into a phase separation device (such as a gas-water separator or a cyclone separator). Utilizing the centrifugal force difference or gravitational sedimentation effect generated within the flow channel, high-density liquid water droplets are forcibly separated from the gas phase fluid and discharged by gravity, completing the initial dehydration operation. Subsequently, the dehydrated gas flow seamlessly through a precision filtration device. This precision filtration device is equipped with a microporous honeycomb sintered filter element or metal fiber sintered felt, with a filtration accuracy better than 0.5 μm. Through a composite physical capture mechanism of interception, diffusion, and Brownian motion interception, it blocks and removes tiny solid particles, dust, and other solid impurities entrained in the gas flow, ultimately outputting intermediate hydrogen with significantly improved purity at the outlet.

[0063] In this embodiment, through the aforementioned cascaded phase separation and precision filtration, the preset purity index is controlled to be no less than 99.999%. This high-purity gas environment can eliminate the tendency of interstitial atoms such as carbon, oxygen, and sulfur to segregate towards the grain boundaries of the soft magnetic alloy during subsequent high-temperature annealing, thus laying the foundation for obtaining an annealed microstructure with ultra-low coercivity.

[0064] S12. Perform a deep adsorption drying operation on the intermediate hydrogen gas to remove trace amounts of residual moisture from the intermediate hydrogen gas, thereby obtaining the protective hydrogen gas.

[0065] Although the intermediate hydrogen gas processed in step S11 has been stripped of liquid water and solid impurities, it still contains trace amounts of highly saturated gaseous volatile water molecules. If this trace residual moisture is directly introduced into the furnace with the gas flow during the annealing stage, it will undergo microscopic dissociation at temperatures above 800°C, and the released active oxygen atoms will cause severe oxidative damage to the iron-cobalt-vanadium matrix.

[0066] Therefore, in this embodiment, intermediate hydrogen gas is introduced into a deep adsorption drying system. This deep adsorption drying system preferably employs a pressure swing adsorption (PSA) dryer or a temperature swing adsorption (TSA) dryer, with its internal dual towers alternately packed with high-performance, high-specific-surface-area superhydrophilic microporous molecular sieves (such as 4A or 5A zeolite molecular sieves) and activated alumina adsorbent. When intermediate hydrogen gas flows through the adsorption bed under a preset pressure, the strong selective physical adsorption force of the molecular sieve micropores on polar water molecules deeply locks the trace amounts of residual gaseous moisture in the gas stream within the adsorbent lattice. Meanwhile, the extremely weakly polar hydrogen molecules easily penetrate the bed.

[0067] Through the aforementioned deep adsorption drying operation, the preset dew point is stably controlled to be no higher than -40℃ (preferably between -50℃ and -60℃). This means that the volume content of trace water vapor in the gas stream is suppressed to an extremely low PPM level. Finally, high-purity, low-dew-point protective hydrogen gas, which meets the production process requirements and possesses extremely high chemical inertness and microscopic reducing properties, is output from the drying system and used as the full-time gas phase carrier in the subsequent all-hydrogen protected annealing process.

[0068] In some optional embodiments, after obtaining the protective hydrogen in step S12 and before introducing the protective hydrogen into the annealing furnace, in order to ensure that the gas flow into the furnace body is always maintained at an ultra-low water vapor partial pressure, and to avoid micro-oxidation and hydrogen embrittlement of the alloy in the furnace due to adsorbent saturation and penetration, pipeline micro-leakage, or sudden process disturbances, the process of this application also includes an online gas supply quality closed-loop monitoring process, which can be achieved through the following steps S14 to S16 in a coordinated manner:

[0069] S14. Perform online dew point monitoring on the protective hydrogen to obtain the real-time dew point characteristic value of the protective hydrogen.

[0070] Specifically, a high-performance gas dew point tester (such as a capacitive high-precision dew point sensor, a thin-film alumina dew point meter, or a cold mirror dew point meter) is installed in series or in parallel on the main gas outlet of the deep adsorption drying system and the gas inlet control valve of the annealing furnace.

[0071] Due to the extreme sensitivity of 1J22 soft magnetic alloy annealing to water content, this dew point meter possesses rapid dynamic response characteristics and a measurement accuracy of no less than ±1℃. When the pretreated protective hydrogen gas flows through the measurement target area, the dew point meter captures and collects the trace water vapor partial pressure characteristics in the gas flow in real time. This data is then converted into a standard electrical signal or digital bus signal output via an internal conditioning circuit, thereby obtaining the real-time dew point characteristic value of the protective hydrogen gas (e.g., water content measured in degrees Celsius (℃) or PPMv).

[0072] S15. Compare and evaluate the real-time dew point feature value with the preset dew point index.

[0073] In this embodiment, the real-time dew point characteristic value obtained in step S14 is transmitted in real time to a centralized control unit (such as a PLC, DCS system, or intelligent control instrument). The control unit has a preset dew point index (i.e., the aforementioned dew point is not higher than -40℃) pre-stored inside. The control unit uses a built-in comparison and evaluation algorithm to continuously compare the received real-time dew point characteristic value with the preset dew point index at high frequency. The evaluation algorithm monitors in real time whether the hydrogen drying purity quality inside the current gas supply pipeline has deteriorated by determining whether "real-time dew point characteristic value ≤ -40℃" or "real-time dew point characteristic value > -40℃".

[0074] S16. In response to the evaluation result that the real-time dew point characteristic value deviates from the preset dew point index, trigger and execute the gas supply status intervention operation to restrict hydrogen that does not meet the index from entering the annealing furnace.

[0075] Specifically, when the evaluation algorithm determines that the real-time dew point characteristic value is greater than -40℃ (for example, when it suddenly deteriorates to -35℃ or -30℃), it means that the current real-time dew point characteristic value has seriously deviated from and exceeded the safety boundary of the preset dew point index, the adsorption drying bed may have undergone microscopic penetration, or the upstream filtration device has experienced instantaneous breakdown.

[0076] In response to the deviation assessment result, the central control unit immediately issues an intervention command, automatically triggering and dynamically executing a gas supply status intervention operation. In this embodiment, the gas supply status intervention operation includes at least one of the following cascaded control actions:

[0077] 1. Automatic alarm: The local control unit and the host computer interface in the central control room immediately trigger an audible and visual alarm, sending an abnormal gas supply warning signal to the on-site process personnel.

[0078] 2. Safety Interlock Cut-off: The control unit sends a hard interlock switch signal to instantly drive the fast-cut-off solenoid valve or pneumatic ball valve located on the main gas inlet pipe of the annealing furnace to perform valve closing action, completely blocking the input of high dew point hydrogen sources that do not meet the index into the annealing furnace from the physical pipeline, protecting the soft magnetic alloy workpieces that are already in a high-temperature state in the furnace from sudden oxidation.

[0079] 3. Regeneration Switching Control: The control unit simultaneously sends a control signal to the switching valve group of the deep adsorption drying system, forcing the currently operating, saturated adsorption drying tower to switch to bypass regeneration / desorption mode, and seamlessly switching the intermediate hydrogen flow to the other side of the fully activated and regenerated, standby deep drying tower for deep dehydration, until the real-time dew point characteristic value at the total outlet falls back below -40℃, before the interlock is released and the gas supply to the annealing furnace is restored.

[0080] Through the online dew point monitoring and closed-loop intervention control consisting of steps S14 to S16, this application cuts off the physical path of product scrapping due to gas quality fluctuations from the underlying equipment control architecture, ensuring that the furnace is always in a pure hydrogen protective atmosphere with ultra-low dew point during the soft magnetic alloy annealing process.

[0081] S20. A vacuum environment is established in the annealing furnace containing the soft magnetic alloy workpiece to be processed, and a pre-baking treatment is performed on the soft magnetic alloy workpiece to be processed in the vacuum environment to remove moisture and impurities from the surface of the soft magnetic alloy workpiece.

[0082] Specifically, after the preparation and quality control of protective hydrogen are completed, the annealing process enters the furnace pretreatment stage. During processing, transportation, and storage, the surface of soft magnetic alloy workpieces inevitably adsorbs impurities such as moisture, oil, and solid particles from the environment. If these surface contaminants are not removed beforehand in the subsequent high-temperature annealing stage, the oxygen generated by the decomposition of moisture at high temperatures will react with the alloy surface to undergo oxidation, and the carbonized residue of oil will contaminate the workpiece surface, both of which will severely degrade the surface quality and magnetic properties of the annealed workpiece. Therefore, before formally introducing protective hydrogen in step S20, a high vacuum environment is established in the annealing furnace, and the workpiece is pre-baked under vacuum. Utilizing the physical property that the boiling point of moisture and volatile impurities is significantly reduced under vacuum, they can be fully desorbed from the workpiece surface at a relatively low temperature and removed by the vacuum system, thus providing a clean workpiece surface foundation for subsequent high-temperature annealing.

[0083] In some embodiments, step S20 can be achieved through the following steps S21-S22:

[0084] S21. Control the absolute vacuum value inside the annealing furnace to be lower than 1.0 × 10⁻⁶. -3 Pa.

[0085] Specifically, after neatly stacking the 1J22 soft magnetic alloy workpieces to be processed on a rack made of high-temperature resistant nickel-chromium alloy and pushing them into the annealing furnace chamber, the furnace door is first locked to perform an airtightness check. Subsequently, the central control unit activates the external vacuum pumping assembly. This vacuum pumping assembly preferably uses a mechanical pump (such as a rotary vane pump or screw pump) as the forestage pump, and is cascaded with a high-discharge-pressure Roots pump and a high-vacuum diffusion pump or molecular pump.

[0086] Specifically, the system first activates the forestage mechanical pump and Roots pump for rough evacuation, rapidly reducing the pressure inside the furnace chamber to a low negative pressure state. Then, the diffusion pump or molecular pump is automatically interlocked to perform deep vacuum evacuation. Through continuous microscopic gas extraction by multiple pump sets, the absolute pressure inside the furnace is suppressed to an extremely low level, until the absolute vacuum value inside the annealing furnace is below 1.0 × 10⁻⁶. -3Pa (e.g., 0.8 × 10⁻⁶) -3 Pa, 0.5×10 -3 Pa, 0.2×10 -3 Pa, 0.1×10 -3 (Pa, etc.). In this deep high vacuum environment, the residual oxygen partial pressure and water vapor partial pressure in the furnace are close to zero, forming an excellent macroscopic negative pressure purification space, which fundamentally eliminates the possibility of any form of high-temperature oxidation damage to the workpiece during the subsequent preheating process.

[0087] S22. The soft magnetic alloy workpiece to be treated is heated to 150°C to 200°C at a heating rate of 5°C / min to 8°C / min, and held at the temperature range of 150°C to 200°C for 1 hour to 2 hours to remove moisture and impurities from the surface of the soft magnetic alloy workpiece to be treated.

[0088] Specifically, after the vacuum level stably meets the aforementioned high vacuum threshold, the centralized control unit drives the electric heating elements (such as molybdenum wire, graphite heating rod, or high-temperature alloy resistance wire) inside the annealing furnace to start heating according to the preset heating process curve. To ensure that heat can be radiated evenly and gently into the furnace cavity, the system controls the heating elements to start linear heating at a first preset heating rate (e.g., 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, etc.) between 5℃ / min and 8℃ / min. Limiting the heating rate helps prevent thermal stress cracking caused by excessive instantaneous temperature difference between the inside and outside of the workpiece, ensuring stable heating of the workpiece. The reason for selecting this heating rate range is that a heating rate that is too low will lead to an excessively long pre-baking cycle, reducing production efficiency; a heating rate that is too high may cause moisture and volatile impurities on the workpiece surface to escape rapidly in a short period of time, causing a sudden increase in local pressure, affecting the stable operation of the vacuum system, and even causing secondary deposition of impurities on the workpiece surface.

[0089] The fluid heating system drives the temperature to gradually increase until the soft magnetic alloy workpiece to be processed is heated to a temperature range of 150°C to 200°C (e.g., 150°C, 165°C, 180°C, 190°C, 200°C, etc.) and then in-situ static heat preservation is activated. Within this temperature range, the heating element is controlled to maintain the first time for 1 to 2 hours (e.g., 1.0h, 1.3h, 1.5h, 1.8h, 2.0h, etc.).

[0090] This process utilizes the physical principle that the phase transition point of a substance shifts under low pressure. Below 1.0 × 10⁻⁶... -3Under the absolute high vacuum environment of Pa, the boiling points of water and trace organic liquids drop sharply. This causes adsorbed free water molecules, water of crystallization, and volatile hydrocarbons remaining from processing residues on the surface, micro-layer gaps, and micro-channels of the 1J22 soft magnetic alloy workpiece to undergo intense microscopic desorption and vaporization phase transitions driven by low-temperature thermal energy at 150℃ to 200℃. The vaporized water vapor and harmful impurity gases, driven by the generated micro-pressure difference, continuously desorb from the workpiece surface and escape into the furnace cavity. They are then rapidly captured and discharged from the furnace by the continuously operating high-vacuum pump unit, thus achieving efficient surface dehydration and pre-purification of the soft magnetic alloy workpiece.

[0091] It is understandable that by performing the aforementioned low-temperature pre-baking treatment in a deep vacuum environment, the annealing process achieves low-consumption desorption and forced removal of impurities adsorbed on the workpiece surface before any process atmosphere is introduced. This pre-purification mechanism ensures that the subsequent introduction of high-purity hydrogen will not contaminate the gas supply circuit due to the instantaneous vaporization of residual moisture on the workpiece surface, guaranteeing that the dew point of the furnace atmosphere can be absolutely locked at an extremely low level below -40°C, eliminating the risk of high-temperature oxidation and embrittlement. Therefore, this application resolves the physical conflict between inherent impurities in the material and the maintenance of a high-quality atmosphere in the furnace from the underlying process flow, and ensures the surface quality and magnetic properties of the annealed workpiece from the process connection perspective.

[0092] S30. Introduce the protective hydrogen gas into the annealing furnace to establish a first slightly positive pressure atmosphere inside the annealing furnace.

[0093] After the high-vacuum pre-baking process in step S20 removes moisture and impurities from the surface of the soft magnetic alloy workpiece, the annealing furnace remains under high vacuum with extremely low residual gas content, and the workpiece surface is in a clean and highly active state. If the temperature is directly increased to the high-temperature annealing zone at this point, any minute atmospheric disturbance or infiltration of external air could trigger oxidation of the workpiece surface. Simultaneously, although the water vapor and volatile gases generated during the pre-baking stage have been removed by the vacuum system, trace amounts of residual impurity gases may still exist inside the furnace.

[0094] Therefore, in step S30, before the formal heating and annealing, pretreated high-quality protective hydrogen is introduced into the annealing furnace. The hydrogen is used as a reducing protective atmosphere to establish a first slightly positive pressure atmosphere with a certain positive pressure inside the furnace, in order to achieve the following dual purposes: First, by forming a positive pressure gradient between the inside and outside of the furnace through the slightly positive pressure atmosphere, the permeation channel of outside air into the furnace is fundamentally blocked, preventing the workpiece from oxidizing in the subsequent high-temperature stage; Second, by continuously introducing and discharging protective hydrogen, the trace impurity gases remaining in the furnace are effectively replaced and diluted, further improving the cleanliness of the atmosphere inside the furnace and creating good atmospheric conditions for the upcoming high-temperature annealing.

[0095] In some embodiments, step S30 can be achieved through the following steps S31-S32:

[0096] S31. Introduce the protective hydrogen gas into the annealing furnace and increase the furnace pressure to the initial slightly positive pressure range within 10 minutes, wherein the furnace pressure corresponding to the initial slightly positive pressure range is between 3 kPa and 5 kPa.

[0097] Specifically, when the vacuum pre-baking process in step S20 is completed and the furnace temperature stabilizes at the pre-baking set point (150℃ to 200℃), the centralized control unit closes the isolation valve between the high vacuum pump group and the furnace body. Subsequently, the system dynamically opens the flow regulating valve (such as a mass flow controller or piezoelectric regulating valve) at the furnace body's gas inlet end, continuously introducing high-purity protective hydrogen obtained from the pre-processing in steps S10 to S16, with a real-time dew point characteristic value that is stable at no higher than -40℃, into the annealing furnace chamber.

[0098] Specifically, in this embodiment, because the furnace was previously at a temperature below 1.0 × 10⁻⁶, -3 In an absolute vacuum state of Pa, a huge negative pressure difference exists between the furnace interior and the external atmosphere. Under this extreme negative pressure, microscopic reverse air leakage can easily occur at the micropores of the furnace sealing ring and the capillary gaps of the flange connection surface due to the compression of the external atmospheric pressure. If the gas intake and pressure building process is too slow and the high vacuum is maintained for too long, oxygen and moisture from the outside air will continuously mix into the furnace, directly contaminating the newly introduced high-purity hydrogen and causing the atmosphere dew point to collapse instantaneously.

[0099] To mitigate this risk, this embodiment employs a "high flow rate, rapid pressure build-up" control strategy. The centralized control unit dynamically adjusts the opening of the main inlet valve based on the actual effective volume of the annealing furnace cavity, controlling the injection of protective hydrogen into the furnace at an extremely high volumetric flow rate. This forces the furnace pressure to rapidly cross the zero point from a negative pressure suction state within 10 minutes (e.g., 3 minutes, 5 minutes, 7 minutes, 10 minutes, etc.), and rigidly pressurize it to a preset initial slightly positive pressure range (i.e., the relative gauge pressure inside the furnace is between 3 kPa and 5 kPa, such as 3 kPa, 3.5 kPa, 4.2 kPa, 4.8 kPa, 5 kPa, etc.).

[0100] By strictly limiting the pressurization time to within 10 minutes, this process significantly shortens the sensitive period of high vacuum negative pressure in the annealing furnace. The rapid filling with hydrogen eliminates the internal and external negative pressure difference in a very short time, effectively limiting and blocking the amount of external air mixed in during the high vacuum intake stage due to slight leaks in the furnace body. Once the furnace pressure reaches an initial slight positive pressure of 3 to 5 kPa, the internal pressure is higher than the external atmospheric pressure, eliminating any possibility of physical leakage of external air into the furnace. The initial safety barrier within the furnace is thus established.

[0101] S32. After reaching the initial slightly positive pressure range, the gas inlet and outlet dynamic balance method is adopted to introduce protective hydrogen at an inlet flow rate of 10 L / min to 15 L / min based on the furnace volume per cubic meter to perform gas replacement operation, so as to establish the first slightly positive pressure atmosphere with a furnace pressure of 5 kPa to 10 kPa in the annealing furnace.

[0102] Specifically, once the pressure inside the furnace steadily enters the initial slightly positive pressure range of 3 kPa to 5 kPa, although external air cannot penetrate, because the previous fast charging stage was only a blind charging static pressure building without exhaust, there are still trace amounts of microscopic residual air masses in the dead corners and material gaps inside the furnace chamber that were not completely removed by the vacuum pump group.

[0103] To completely remove these residual trace impurities from the furnace chamber, in this embodiment, the centralized control unit, upon detecting that the pressure has reached the target level, interlocks and opens the electric regulating valve or back pressure valve at the furnace exhaust end, thereby initiating the dynamic balance mode for inlet and outlet gas. This dynamic balance mode refers to the simultaneous and continuous opening of both the main inlet valve and the main exhaust valve of the annealing furnace during gas replacement, heating, heat preservation, and specific cooling stages. The control system coordinates and decouples the mass flow controller at the inlet end and the electric back pressure valve at the exhaust end, ensuring that the inlet mass flow rate and the outlet mass flow rate are dynamically constant, thus overcoming the limitations of traditional static pressure holding or intermittent exhaust.

[0104] Specifically, the gas inlet control parameters during the gas replacement operation in this step are standardized according to the furnace volume of the annealing furnace: the inlet flow rate of the protective hydrogen is controlled to be stable between 10 L / min and 15 L / min per cubic meter of furnace volume (for example, for a 1 m³ furnace, the inlet flow rate is adjusted to 10 L / min, 11 L / min, 12.5 L / min, 14 L / min, 15 L / min, etc.; for a 2 m³ furnace, it is proportionally increased to 20 L / min to 30 L / min, and so on). The reason for selecting this inlet flow rate range is that if the flow rate is too low, the gas replacement efficiency will be insufficient, and the residual impurities in the furnace cannot be fully diluted and discharged within a reasonable time; if the flow rate is too high, it will cause excessive consumption of high-purity hydrogen, increasing production costs and potentially causing the furnace pressure to exceed the target range.

[0105] At the same time, the opening of the back pressure valve at the exhaust end is adjusted so that during the continuous flushing and replacement process, the pressure inside the furnace is steadily increased from the initial slightly positive pressure and maintained at the first slightly positive pressure atmosphere state of 5 kPa to 10 kPa (e.g., 5 kPa, 6.5 kPa, 8 kPa, 9.2 kPa, 10 kPa, etc.).

[0106] During this stage, a continuous flow of hydrogen gas at a rate of 10 L / min to 15 L / min per cubic meter of furnace volume, supported by a stable micro-positive pressure of 5 kPa to 10 kPa, forms a uniform micro-convective airflow field with a defined flow direction inside the furnace cavity. This dynamically flowing hydrogen airflow field can penetrate deep into the stacked layers of the soft magnetic alloy workpiece rack to be processed, and through diffusion and momentum transfer effects, thoroughly flushes away and dilutes the trace residual air molecules adhering to the intergranular gaps and dead corners of the furnace wall, and continuously carries them out of the furnace with the exhaust gas flow.

[0107] It is understandable that this step utilizes the dynamic convection of hydrogen at a specific spatial density to achieve deep gas replacement inside the furnace, reducing the residual impurity content of the furnace atmosphere to the limit. This creates a high-purity, high-stability all-hydrogen protective base before the furnace temperature rises significantly, providing an impeccable process environment for the subsequent high-temperature annealing stage.

[0108] S40. The furnace temperature of the annealing furnace is raised to the target annealing temperature range, and the protective hydrogen is introduced in a dynamic balance manner during the heating stage to establish a second micro-positive pressure atmosphere in the annealing furnace.

[0109] Specifically, after establishing the first micro-positive pressure atmosphere in step S30, a clean and stable protective hydrogen atmosphere has been formed in the annealing furnace. Residual impurities in the furnace have been fully replaced and discharged, and a positive pressure barrier has been established between the inside and outside of the furnace. At this point, the annealing process enters the core high-temperature treatment stage—raising the furnace temperature from the low temperature state after pre-baking to the target annealing temperature range of the soft magnetic alloy. However, the heating stage faces new technical challenges: on the one hand, as the furnace temperature continues to rise, the thermal motion of gas molecules intensifies, and the volume of gas in the furnace expands. If the inlet flow rate before heating remains unchanged, the furnace pressure will naturally decrease as the temperature rises, and the original micro-positive pressure barrier may be weakened, increasing the risk of external air infiltration; on the other hand, soft magnetic alloy workpieces are extremely sensitive to the cleanliness of the atmosphere in the high-temperature section, and the furnace atmosphere needs to be continuously renewed and purified with fresh protective hydrogen. Even trace amounts of residual oxygen or water vapor may cause irreversible oxidation on the surface of the workpiece at high temperatures. Therefore, in step S40, the supply parameters of protective hydrogen are adjusted in a targeted manner during the heating stage. By increasing the inlet flow rate and continuing to use the dynamic balance method of inlet and outlet gas, a second micro-positive pressure atmosphere with a higher furnace pressure level than the first micro-positive pressure atmosphere is established in the annealing furnace to meet the higher requirements of atmosphere protection strength and purification efficiency in the high-temperature section.

[0110] In some embodiments, step S40 can be achieved through the following steps S41-S42:

[0111] S41. The furnace temperature of the annealing furnace is raised to the target annealing temperature range of 850°C to 890°C at a heating rate of 5°C / min to 10°C / min.

[0112] Specifically, after the low-temperature (150°C to 200°C) full hydrogen replacement operation in step S32 is completed, the first slightly positive pressure atmosphere (5 kPa to 10 kPa) inside the furnace has been fully established. At this time, the central control unit starts the high-temperature heating program. The control system drives the electric heating element to increase the heating power and controls the furnace temperature of the annealing furnace to rise linearly at a second preset heating rate between 5°C / min and 10°C / min (e.g., 5°C / min, 6.5°C / min, 8°C / min, 9.2°C / min, 10°C / min, etc.).

[0113] Specifically, in this embodiment, the 1J22 iron-cobalt-vanadium soft magnetic alloy exhibits magnetic phase transformation and complex recrystallization grain nucleation and growth behavior at high temperatures. Strictly limiting the heating rate to the range of 5°C / min to 10°C / min ensures that large workpieces or batches of strips in the entire furnace can absorb heat synchronously from the surface inwards, minimizing micro-thermal stress fluctuations caused by uneven three-dimensional radiative temperature field within the furnace chamber. The furnace temperature continuously rises under the drive of the electric heating element until the furnace temperature is heated to the target annealing temperature range of 850°C to 890°C (e.g., 850°C, 860°C, 875°C, 885°C, 890°C, etc.). This target annealing temperature range represents the ideal thermodynamic temperature field for complete recrystallization of the 1J22 soft magnetic alloy, elimination of residual cold working stress, and prevention of abnormally coarse grain growth. In addition, for soft magnetic alloy workpieces of different grades and specifications, specific annealing temperature settings can be selected within this temperature range. For example, for iron-nickel high permeability alloys, 850℃ to 870℃ can be selected, and for iron-cobalt high saturation magnetic induction alloys, 870℃ to 890℃ can be selected.

[0114] S42. During the heating stage, the inlet flow rate is adjusted to 20 L / min to 25 L / min per cubic meter of furnace volume, and the protective hydrogen is introduced in a dynamic balance manner to establish a second slightly positive pressure atmosphere with a furnace pressure of 8 kPa to 12 kPa in the annealing furnace.

[0115] Specifically, as the furnace temperature rapidly and continuously climbs from 150℃~200℃ to a broad medium-high temperature range of 850℃~890℃, profound microscopic physicochemical evolution occurs in both the fluids and solids within the furnace. On the one hand, according to the ideal gas law, the gas inside the furnace expands upon heating, leading to a natural pressure surge for the same molar amount. On the other hand, and more critically, the harmful interstitial atoms such as carbon, oxygen, sulfur, and nitrogen dissolved within the 1J22 soft magnetic alloy workpiece matrix undergo exponentially enhanced diffusion under the drive of high-temperature thermal activation energy. These atoms begin to agglomerate, diffuse, and release in large quantities from the alloy interior to the workpiece surface, resulting in a sudden increase in microscopic volatiles and localized gaseous impurities on the workpiece surface.

[0116] In order to suppress pressure runaway caused by gas expansion, and to completely suppress and quickly remove the microscopic interstitial impurity gases that burst out as the temperature rises, the centralized control unit implements synchronous cascaded stabilization control of flow rate and pressure under the "dynamic balance mode of inlet and outlet gas" during the heating stage.

[0117] Specifically, the control system significantly increases the opening of the regulating valve at the inlet, increasing the inlet flow rate of protective hydrogen from the replacement stage to between 20 L / min and 25 L / min per cubic meter of furnace volume (for example, for a 1 m³ furnace, the inlet flow rate is increased to 20 L / min, 21 L / min, 22.5 L / min, 24 L / min, 25 L / min, etc.; for a 2 m³ furnace, it is proportionally increased to 40 L / min to 50 L / min, and so on). The reason for selecting this inlet flow rate range is that the increase in flow rate must match the rate of gas volume expansion within the furnace during the heating stage—if the inlet flow rate is insufficient, the furnace pressure will still decrease as the temperature rises, failing to effectively maintain and strengthen the micro-positive pressure barrier; if the inlet flow rate is increased too much, it will not only cause excessive consumption of high-purity hydrogen but may also create localized turbulence within the furnace due to excessively high gas velocity, affecting the uniformity of the temperature field.

[0118] While a large flow of gas is being introduced, the control system uses a precision electric back pressure valve installed at the exhaust end for closed-loop pressure feedback regulation. By dynamically increasing the cross-sectional area of ​​the exhaust channel of the back pressure valve, excess gas volume caused by the large flow of gas injection and thermal expansion is offset. Thus, in a continuously convective and refreshed dynamic flow field, the gauge pressure inside the furnace is stably maintained at a second slightly positive pressure atmosphere of 8 kPa to 12 kPa (e.g., 8 kPa, 9 kPa, 10.5 kPa, 11.5 kPa, 12 kPa, etc.).

[0119] In this step, under a high relative gauge pressure of 8 kPa to 12 kPa, high-purity protective hydrogen gas is injected at a rate of 20 L / min to 25 L / min per cubic meter of furnace volume, creating a directional fluid wind field with extremely high kinetic energy within the furnace cavity. This design possesses multiple significant microscopic physicochemical effects: on the one hand, the high-pressure, high-flow-rate hydrogen gas with a dew point not exceeding -40°C creates an extremely low microscopic partial pressure environment of water vapor and oxygen on the workpiece surface. When carbon and oxygen impurities inside the alloy diffuse to the surface at high temperatures of 850°C to 890°C, the highly reactive hydrogen gas flow can rapidly undergo a microscopic interfacial reduction reaction with them (e.g., Before the generated trace gaseous products could aggregate or re-aggregate towards the grain boundaries, they were instantly entrained and directionally carried away by the high-kinetic-energy all-hydrogen convection wind field, thereby breaking the chemical equilibrium of the interfacial reaction and forcing harmful interstitial impurities inside the matrix to continuously desorb outward, thus achieving deep purification of the soft magnetic alloy.

[0120] On the other hand, due to the extremely high thermal conductivity of hydrogen among all gases, and the significant increase in gaseous molecular density as the furnace pressure rises to 8-12 kPa during this stage, the fluid forms intense high-temperature convective heat transfer within the furnace under the high-velocity convection state resulting from the "dynamic balance of inlet and outlet gases." This greatly overcomes the limitations of traditional vacuum furnaces or low-velocity furnaces that rely solely on radiative heat transfer, achieving extremely high uniformity in the microscopic temperature field across all dimensions of the workpiece throughout the furnace. This prevents grain inhomogeneity and thermal deformation stress retention caused by localized overheating or underheating.

[0121] It is understandable that this step, by skillfully binding the high flow rate (20~25 L / min / m³) with the blast furnace pressure (8~12 KPa) in a dynamic balance during the heating stage, achieves perfect decoupling and synergistic control of the "heat-flow-phase reaction" during the sensitive period of high-temperature evolution, ensuring the purity and isotropy of the microstructure of the alloy when it climbs to the target annealing temperature.

[0122] S50. Hold the furnace at the target annealing temperature range for a first duration. During the holding period, maintain the dynamic balance between the incoming and outgoing gases and introduce the protective hydrogen gas to establish a third micro-positive pressure atmosphere in the annealing furnace with a furnace pressure lower than the second micro-positive pressure atmosphere.

[0123] Specifically, after raising the furnace temperature to the target annealing temperature range of 850°C to 890°C and establishing a second slightly positive pressure atmosphere in step S40, the annealing process enters the core holding stage. The holding stage is the key stage in the annealing process of soft magnetic alloys, which determines the evolution of the material's microstructure and the recovery of its magnetic properties. In this stage, a series of physical metallurgical processes occur inside the alloy, such as recrystallization, grain growth, residual stress elimination, and microstructure homogenization. It is necessary to keep the furnace temperature stable within the target annealing temperature range and maintain a clean and reducing atmosphere.

[0124] However, the heat preservation stage faces different technical requirements than the heating stage: On the one hand, the furnace temperature has stabilized in the high-temperature range, and the workpiece has already completed the high-temperature desorption of residual impurities on its surface during the initial heating process. The generation rate of impurity gases in the furnace is significantly lower than in the heating stage, thus reducing the need for high-flow-rate flushing purification of protective hydrogen. On the other hand, the heat preservation stage lasts for a long time (usually several hours). If the high inlet flow rate of the heating stage is maintained, it will not only result in a large amount of ineffective consumption of high-purity protective hydrogen and a significant increase in production costs, but also the excessively high airflow velocity may disturb the uniformity of the temperature field in the furnace over a long period of time, which is not conducive to the homogeneous evolution of the internal structure of the workpiece. In addition, under high-temperature heat preservation conditions, excessively high furnace pressure levels will also increase the load on the furnace sealing components, increasing safety hazards. Therefore, in step S50, the supply parameters of protective hydrogen are adaptively optimized and adjusted during the heat preservation stage—the inlet flow rate is appropriately reduced from the high flow rate level during the heating stage, and a third micro-positive pressure atmosphere with a lower furnace pressure level than the second micro-positive pressure atmosphere is established while maintaining the dynamic balance between inlet and outlet gas, so as to achieve a reasonable balance between effectively maintaining the protective atmosphere and controlling production costs.

[0125] Specifically, after entering the heat preservation stage, the control system actively reduces the air inlet flow rate of the annealing furnace from the high flow rate (20 L / min / m³ to 25 L / min / m³) during the heating stage to 6 L / min to 8 L / min per cubic meter of furnace volume (for example, for a 1 m³ furnace, the air inlet flow rate is adjusted to 6 L / min, 6.5 L / min, 7.2 L / min, 7.8 L / min, 8 L / min, etc.; for furnaces of other volumes, the flow rate is scaled proportionally). Simultaneously, the precision electric back pressure valve at the exhaust end performs closed-loop adjustment based on the feedback signal from the pressure transmitter, reducing the furnace pressure from the high gauge pressure of the heating stage and maintaining it stably at a third slightly positive pressure atmosphere of 2 kPa to 3 kPa (for example, 2 kPa, 2.2 kPa, 2.5 kPa, 2.8 kPa, 3 kPa, etc.).

[0126] In this embodiment, the reason why the air intake flow rate during the heat preservation stage is strictly limited to 6 L / min to 8 L / min per cubic meter of furnace volume, and the furnace pressure is limited to 2 kPa to 3 kPa, is as follows:

[0127] On the one hand, during the core heat preservation stage from 850℃ to 890℃, the grains of the 1J22 soft magnetic alloy are in a high-temperature dynamic equilibrium period of nucleation and growth. At this time, the requirement for the uniformity of the three-dimensional temperature field in the furnace reaches its limit (usually, the furnace temperature uniformity is required to be better than ±3℃). If the high flow rate of protective hydrogen above 20 L / min / m³ during the heating stage is continued, due to the huge micro-temperature difference between the room temperature or preheated hydrogen and the high-temperature environment in the furnace, the high-speed, high-flow-rate non-uniform convection flow field will generate severe high-temperature heat loss in local areas of the furnace (such as near the gas inlet), thereby destroying the furnace temperature uniformity and causing the magnetic properties of the workpieces in the same furnace to fluctuate due to local grain size dispersion. By finely reducing the gas inlet flow rate to 6~8 L / min / m³, the extremely high thermal conductivity of the low-flow-rate hydrogen is utilized to help maintain the temperature field balance, and the local cooling effect caused by high-speed convection is completely eliminated, ensuring the isotropy of the entire furnace workpiece.

[0128] On the other hand, although the flow rate was reduced, the "dynamic balance of inlet and outlet gas" was not eliminated, and the furnace remained a flowing "living water" environment. Under the support of a third micro-positive pressure of 2 kPa to 3 kPa, a hydrogen flow rate of 6 to 8 L / min / m³ was just enough to meet the minimum kinetic requirements for entraining and carrying away the harmful gaseous products (such as unreacted trace amounts of water and hydrocarbon molecules) that continuously precipitated from the surface of the workpiece during the heat preservation period. Furthermore, the furnace pressure of 2 to 3 kPa was higher than the atmospheric pressure outside the furnace, ensuring that external air could not possibly leak back. If the inlet flow rate was lower than 6 L / min / m³ or the furnace pressure was lower than 2 kPa, the kinetic energy of the gas phase fluid inside the furnace would be insufficient, and a gas stagnation dead zone would easily form in the center of the material rack, leading to the enrichment of local impurity gases and back-seeping and pinning of alloy grain boundaries. If the inlet flow rate was higher than 8 L / min / m³ or the furnace pressure was higher than 3 kPa, the aforementioned problem of uneven temperature field would be introduced, resulting in unnecessary waste of hydrogen resources.

[0129] Furthermore, during the aforementioned high-temperature insulation phase, the baseline range for the first duration (i.e., the total core high-temperature insulation time) is set to 4 to 6 hours (e.g., 4.0h, 4.5h, 5.0h, 5.5h, 6.0h, etc.).

[0130] In this embodiment, 4 to 6 hours is selected as the reference range for the first duration because: for soft magnetic alloys such as 1J22, the energy release, stress relief, and normal grain growth at the grain boundaries at 850°C to 890°C have specific time dependencies. If the holding time is less than 4 hours, the high-density dislocations and stress fields introduced by cold working inside the alloy cannot be completely released and annihilated, and the retention of some residual stress will lead to a significantly higher coercivity of the final workpiece; if the holding time blindly exceeds 6 hours, although the stress is completely released, the alloy grains will become abnormally coarse at the microscopic level due to the long-term high-temperature thermal drive (severe overheating phenomenon). This will not only lead to a significant increase in the mechanical brittleness of the material and make it extremely easy to crack during subsequent processing or use, but will also deteriorate the high-frequency magnetic properties of the material due to the excessively large grains.

[0131] Furthermore, during the aforementioned heat preservation stage, the first duration (i.e., the total core high-temperature heat preservation time) is associated with a preset algorithm compensation mechanism. In this embodiment, the process is pre-set with a specific loading starting point, namely a preset reference weight (exemplarily set to 20.00 kg) and a preset reference duration corresponding to that weight (exemplarily set to 240.00 minutes, i.e., 4 hours).

[0132] To address the industry challenge of fluctuating heat capacity of the entire furnace material and implicitly shortening or lengthening the actual heating and holding time of the furnace core due to changes in the overall mass of the workpiece loaded in a single furnace, this application introduces an adaptive workpiece weight adjustment algorithm based on the coupling of fluid dynamics and thermodynamics.

[0133] The specific control rules are as follows: the control system obtains the total weight of the workpieces actually loaded into the furnace in the current batch through weighing sensors or manual input, and compares the actual total weight with the preset benchmark weight in real time; for every 1 kg increase in the weight of the soft magnetic alloy workpiece to be processed based on the preset benchmark weight, the corresponding first time duration is linearly increased by 5 minutes proportionally on the preset benchmark time duration.

[0134] For example, if the total weight of the soft magnetic alloy workpieces loaded in a single furnace is 20.00 kg (equal to the baseline weight), the control system strictly controls the first duration to be 240.00 minutes (4 hours). If, due to production scheduling adjustments, the total weight of the workpieces loaded in a single furnace increases to 21.00 kg (i.e., 1 kg more than the baseline weight), the corresponding first duration is automatically adjusted to 245.00 minutes. Similarly, when the total weight of the workpieces increases to 22.00 kg, 25.00 kg, 30.00 kg, and 32.00 kg respectively, the control system calculates and drives the first duration to be precisely and adaptively extended to 250.00 minutes, 265.00 minutes, 290.00 minutes, and 300.00 minutes (5 hours) respectively.

[0135] The reason for this design is that 1J22 soft magnetic alloy blocks or strip stacks have a high density and a specific heat capacity. When the total weight of the workpieces loaded in the furnace exceeds 20.00 kg, the macroscopic thermal resistance and total heat capacity of the entire furnace material increase linearly. Under the same radiative and convective heating power, the heat transfer delay (i.e., heat penetration time) from the outer surface of the workpiece to the dead corner at the center of the loading rack increases with weight. If a uniform fixed holding time is used regardless of weight, the workpieces at the furnace core will not actually reach the true holding time requirement when loaded with heavy weights (because most of the time is consumed in the heat conduction delay), resulting in incomplete annealing of the furnace core products. This application uses an algorithm that provides 5 minutes of linear hard compensation for every 1 kg of material added to accurately compensate for the microscopic heat penetration delay caused by the increase in material. This ensures that no matter how the furnace load fluctuates, every soft magnetic alloy workpiece in the furnace (especially the workpiece located at the geometric center of the rack) undergoes an absolutely sufficient and uniform high-temperature reduction and purification process in the dimension of microscopic grain reorganization. This results in the batch products leaving the factory exhibiting extremely high consistency in coercivity and permeability, eliminating performance dispersion.

[0136] S60. After the heat preservation stage is completed, perform multi-stage cooling operation on the annealing furnace to obtain the annealed soft magnetic alloy workpiece.

[0137] Specifically, after the heat treatment is completed in the target annealing temperature range in step S50, the soft magnetic alloy workpiece has undergone physical metallurgical processes such as recrystallization, grain growth, and microstructure homogenization, and the residual stress has been fully eliminated. At this time, the annealing process enters the cooling stage—gradually reducing the furnace temperature from the high-temperature range of 850°C to 890°C to the furnace exit temperature.

[0138] The cooling stage is not a simple process, but a crucial step that has a decisive impact on the final magnetic properties of the annealed workpiece. Improper cooling control may lead to the following problems:

[0139] Firstly, excessively rapid cooling will cause a significant temperature gradient between the core and surface of the workpiece, resulting in secondary thermal stress, which will cause the eliminated residual stress to regenerate, and may even cause workpiece deformation.

[0140] Secondly, if the furnace atmosphere pressure is not properly controlled during the cooling process, outside air may seep into the furnace due to the negative pressure formed by the cooling and contraction of the gas inside the furnace, causing the workpiece to undergo surface oxidation in the high-temperature section, resulting in failure.

[0141] Third, soft magnetic alloys need to go through a specific order-disorder transition temperature range and an ordered phase precipitation temperature range during the cooling process. If the cooling rate is not appropriate within this temperature range, it will affect the final order and magnetocrystalline anisotropy of the alloy, thereby deteriorating the soft magnetic properties.

[0142] To this end, step S60 employs a multi-stage cooling operation, dividing the cooling process into three stages with differentiated cooling rates, gas supply methods, and furnace pressure control strategies, in order to achieve coordinated matching among cooling rate, atmosphere protection, and organizational regulation.

[0143] Specifically, the multi-stage cooling operation includes the following steps S61-S63.

[0144] S61. First cooling stage: Cooling to the second temperature range at a first cooling rate and holding at the temperature for a second duration, wherein the dynamic balance mode of inlet and outlet gas is cancelled during the first cooling stage, and the supply of protective hydrogen is maintained by using exhaust pressure threshold control mode.

[0145] Specifically, the first cooling stage includes the following coordinated control process: the control system drives the system to rapidly cool the furnace temperature from the target annealing temperature range of 850℃~890℃ to a second temperature range of 740℃~760℃ at a first cooling rate between 100℃ / min and 150℃ / min (e.g., 100℃ / min, 115℃ / min, 125℃ / min, 140℃ / min, 150℃ / min, etc.), and in the second temperature range, in-situ static heat preservation is initiated and maintained for a second duration of 1 hour to 2 hours (e.g., 1.0h, 1.2h, 1.5h, 1.8h, 2.0h, etc.).

[0146] It is important to note that the second temperature range of 740°C to 760°C in this embodiment is chosen because this temperature range represents the optimal characteristic eutectic and phase transformation thermodynamic window for beneficial ordered phase nucleation and growth or lattice matrix stress relaxation in 1J22 and other iron-cobalt-vanadium soft magnetic alloys. If the cooling endpoint is significantly higher than 760°C, the thermal motion of matrix atoms becomes too intense, making it impossible to spontaneously nucleate and construct a highly isotropic ordered phase, and the grains are prone to unnecessary secondary coarsening in the early stages of cooling. If the cooling endpoint is significantly lower than 740°C, the diffusion-driven energy for lattice restructuring drops precipitously and is highly likely to directly intrude into the initiation boundary of harmful brittle phases. Simultaneously, a cooling rate of 100°C / min to 150°C / min prevents the introduction of microscopic thermal distortion dislocations due to rapid thermal shock. Therefore, in-situ heat preservation for 1 to 2 hours within the temperature range of 740℃ to 760℃ can enable the lattice atoms after recrystallization to undergo local microscopic perfect rearrangement under the thermodynamic equilibrium field, so that the degree of ordering reaches a saturated state, thereby maximizing the reduction of coercivity of the final workpiece and improving its initial permeability.

[0147] In addition, during the first cooling phase, the control system performed a very special fluid control transformation: it forcibly canceled the previous dynamic balance mode of inlet and outlet gas and switched to exhaust pressure threshold control mode (i.e., pulse exhaust pressure holding control) to maintain the supply of protective hydrogen.

[0148] Specifically, the control system reduces the inlet flow rate of protective hydrogen to between 3 L / min and 6 L / min per cubic meter of furnace volume (e.g., 3 L / min, 4 L / min, 5 L / min, 6 L / min, etc.). Simultaneously, it closes the existing continuous electric back pressure valve at the exhaust end and activates the hard-interlocked fast exhaust solenoid valve. The control system sets the opening pressure threshold of the exhaust solenoid valve to 8 kPa to 10 kPa (e.g., 8 kPa, 9 kPa, 10 kPa, etc.) and the closing pressure threshold to 2 kPa to 3 kPa (e.g., 2 kPa, 2.5 kPa, 3 kPa, etc.).

[0149] It is understandable that in step S61, by rapidly cooling the annealing furnace from the high-temperature zone to the second temperature range of 740°C to 760°C using a first cooling rate of 100°C to 150°C to 150°C and holding it at that temperature, the temperature of each part of the workpiece is homogenized in the higher temperature range before the precipitation of harmful phases. The dynamic balance of inlet and outlet gas is eliminated, replaced by a zoned exhaust control based on a preset upper pressure limit (8KPa to 10KPa) and lower pressure limit (2KPa to 3KPa). This reduces the switching frequency of the exhaust solenoid valve, minimizing the escape of high-temperature hydrogen and the heat carried away by frequent exhaust, ensuring the consistency of the cooling rate of each workpiece in the furnace, and avoiding thermal stress and deformation introduced by localized overcooling. Reducing the inlet gas flow rate to a lower level of 3L / min to 6L / min also reduces the disturbance of the furnace thermal field by cold hydrogen. Together with the zoned exhaust control, a relatively static, slow-cooling microenvironment is constructed, providing a uniform workpiece state as a basis for subsequent rapid traversal of the harmful phase precipitation temperature zone.

[0150] S62, Second cooling stage: Cooling from the second temperature range to the third temperature range at a second cooling rate greater than the first cooling rate, wherein the supply of protective hydrogen is restored and maintained by the inlet and outlet gas dynamic balance method during the second cooling stage.

[0151] Specifically, the second cooling stage includes the following coordinated control process: After the second holding time of step S61 ends, the process flow enters the extremely dangerous sensitive temperature zone for brittle phase precipitation (below 740°C to 460°C). In order to forcibly intercept the nucleation of harmful phases, the control system controls the annealing furnace to perform forced rapid cooling at an extremely high second cooling rate between 250°C / min and 290°C / min (e.g., 250°C / min, 260°C / min, 275°C / min, 285°C / min, 290°C / min, etc.), rapidly cooling from the second temperature range to a third temperature range of 440°C to 460°C (e.g., 440°C, 445°C, 450°C, 455°C, 460°C, etc.).

[0152] Meanwhile, during the second cooling phase, the control system resumes and adopts a dynamic balance mode for incoming and outgoing gas. By coordinating the adjustment of the opening of the inlet and outlet valves, the pressure inside the furnace is stably maintained between 4 kPa and 6 kPa (e.g., 4 kPa, 4.8 kPa, 5.5 kPa, 6 kPa, etc.), and the inlet flow rate of protective hydrogen is significantly increased to between 10 L / min and 15 L / min per cubic meter of furnace volume (e.g., 10 L / min, 11.5 L / min, 13 L / min, 15 L / min, etc.).

[0153] It is understandable that in step S62, increasing the second cooling rate to an extremely high range of 250℃ / min to 290℃ / min aims to rapidly reduce the temperature of the alloy workpiece from around 750℃ to around 450℃. This effectively suppresses the nucleation and growth of brittle intermetallic compounds such as the σ phase in the sensitive temperature range of 700℃ to 500℃, thus preventing grain boundary embrittlement. To complement this rapid cooling action, restoring the dynamic balance of inlet and outlet gas and maintaining the furnace pressure at 4KPa to 6KPa, while increasing the inlet gas flow rate to 10L / min to 15L / min, allows a large flow of fresh cryogenic protective hydrogen to continuously flush the workpiece surface and remove a significant amount of heat. This forced convection heat transfer ensures the achievement of the aforementioned rapid cooling rate, while the dynamic pressure control prevents drastic fluctuations in furnace pressure. This stage, through the synergistic combination of "rapid cooling" and "enhanced convection," ensures that the workpiece quickly passes through the precipitation temperature range of harmful phases, providing a decisive guarantee for obtaining a final alloy structure with high plasticity and low brittleness.

[0154] S63. Third cooling stage: Cooling from the third temperature range to the furnace exit temperature at a third cooling rate, wherein the supply of protective hydrogen is maintained by the dynamic balance of inlet and outlet gas in the third cooling stage.

[0155] Specifically, the third cooling stage includes the following coordinated control process: once the furnace temperature has stably passed the brittle phase danger zone and safely decreased to the third temperature range, the thermodynamic driving force for the precipitation of harmful phases has completely disappeared. The control system controls the furnace temperature to continue cooling rapidly and safely from the third temperature range to a furnace exit temperature not exceeding 150°C (e.g., 150°C, 140°C, 125°C, 110°C, 90°C, etc.) at a third cooling rate between 220°C / min and 260°C / min (e.g., 220°C / min, 235°C / min, 245°C / min, 255°C / min, 260°C / min, etc.) between 220°C / min and 260°C / min.

[0156] During this period, the furnace maintains a dynamic balance between incoming and outgoing gas. The control system tightens the opening of the exhaust back pressure valve to steadily raise the furnace pressure and maintain it at a slightly positive pressure level of 6 kPa to 8 kPa (e.g., 6 kPa, 6.8 kPa, 7.5 kPa, 8 kPa, etc.). At the same time, the flow rate of the protective hydrogen gas is further adjusted and increased to between 15 L / min and 20 L / min per cubic meter of furnace volume (e.g., 15 L / min, 16.5 L / min, 18 L / min, 20 L / min, etc.).

[0157] It is understandable that in step S63, when the workpiece temperature has dropped below 450℃, the thermodynamic window for the precipitation of harmful phases such as the σ phase has essentially closed, and the ordered transformation of the alloy is nearing completion. Continuing to use a higher cooling rate of 220℃ / min to 260℃ / min, and limiting the furnace exit temperature to no higher than 150℃, aims to quickly lock in the high-temperature, superior microstructure formed at the end of step S62, preventing the aging precipitation of fine, brittle precipitates such as carbides in the low-temperature region, and avoiding oxidation of the workpiece upon contact with the atmosphere when exiting the furnace at a higher temperature (e.g., >150℃). Combined with a maintained furnace pressure of 6KPa to 8KPa and a large-flow dynamic equilibrium gas supply of 15L / min to 20L / min, the cooling efficiency of forced convection heat transfer is maintained, ensuring the continuous execution of the aforementioned cooling rate, while also significantly shortening the production cycle and improving process efficiency. Thus, the multi-stage cooling operation of step S60 is completed, resulting in an annealed soft magnetic alloy with high magnetic properties, low brittleness, and consistent performance.

[0158] To further verify the substantial technological advancements of the soft magnetic alloy annealing process of this invention (hereinafter referred to as the "new process") compared to the traditional vacuum or conventional hydrogen-protected annealing process (hereinafter referred to as the "old process"), this application specifically used 1J22 iron-cobalt-vanadium soft magnetic alloys smelted and rolled to the same specifications in the same batch as test samples. Annealing was performed using both the old process and the new process of this application, and a rigorous comparative test was conducted on the static magnetic induction intensity and high-frequency loss of the annealed finished products.

[0159] 1. Comparative Testing and Mechanism Analysis of Magnetic Induction Intensity (Jm)

[0160] Under standard conditions with a test frequency of 50 Hz, a series of representative test magnetic field strengths (H, from 100 A / m to 4000 A / m) were selected. Magnetic induction intensity tests were conducted on the 1J22 soft magnetic alloy self-adhesive core products prepared by annealing using both the old process and the new process of this embodiment. The magnetic induction intensity (Jm) of the 1J22 soft magnetic alloy samples treated by the old and new processes was tested. Specific comparative data are shown in Table 1 below.

[0161] Table 1: Comparison of magnetic induction intensity of 1J22 soft magnetic alloy self-bonded iron cores prepared by new and old annealing processes. Table 1: Comparison of magnetic induction intensity (Jm) of 1J22 soft magnetic alloy prepared by new and old annealing processes.

[0162] As shown in Table 1, the 1J22 soft magnetic alloy annealed using the new process of this application achieves a comprehensive improvement in magnetic induction intensity compared to the old process under all applied magnetic field strengths. Especially in the low to medium magnetic field range of 100 A / m to 400 A / m, the magnetic induction intensity of the new process shows a significant leap compared to the old process (for example, at 100 A / m, it jumps from 0.370 T to 0.5166 T, an increase of approximately 39.6%).

[0163] At the physical mechanism level, the magnetization process in the low-to-medium field region mainly depends on the displacement of the magnetic domain walls within the alloy. The surge in magnetic induction intensity in this region demonstrates that the "high-flow-rate dynamic equilibrium replacement mechanism of gas inlet and outlet" introduced in this application during the heating and holding stages, as well as the "gas-phase breathing pulse exhaust dehydrogenation mechanism" created in the first cooling stage, successfully achieved extremely deep decarburization, deoxygenation, and dehydrogenation purification. Because interstitial impurity atoms at grain boundaries and within the lattice are thoroughly swept away, the "impurity pinning effect" of the magnetic domain walls during movement is significantly weakened, resulting in extremely high initial permeability and extremely low coercivity in the material. Simultaneously, the extremely high saturation magnetic induction of 2.2799 T in the high-field region (4000 A / m) also confirms that the adaptive weight compensation algorithm in the holding stage ensured the complete release of residual stress within the alloy and the perfect construction of the ordered phase.

[0164] 2. Comparative Testing and Mechanism Analysis of Core Loss (Ps)

[0165] Under a stringent 2 T (Tesla) high operating magnetic induction intensity, specific total loss tests were performed on the 1J22 soft magnetic alloy self-adhesive core products prepared by annealing using both the old process and the new process of this embodiment in the mid-to-high frequency operating ranges of 400 Hz, 800 Hz, 1000 Hz, and 2000 Hz. Specific total loss (Ps) tests were conducted on the 1J22 soft magnetic alloy samples treated by the old and new processes. The specific comparison data are shown in Table 2 below.

[0166] Table 2: Comparison of high-frequency losses (Ps) of 1J22 soft magnetic alloy prepared by new and old annealing processes

[0167] As shown in Table 2, the new process in this application demonstrates a particularly significant effect in suppressing high-frequency losses in the self-adhesive core as the operating frequency of the alternating magnetic field increases. In all frequency bands from 400 Hz to 2000 Hz, the loss value of the new process is consistently 20% to 26% lower than that of the old process (for example, at the extremely high frequency of 2000 Hz, the loss drops dramatically from 549.8081 W / kg to 438.6210 W / kg).

[0168] At the microscopic phase transition dynamics level, the core loss under a medium-to-high frequency alternating magnetic field depends on the uniformity of the material grains and the presence of hard and brittle precipitates at the grain boundaries. This set of high-frequency, low-loss experimental data directly confirms that the "ultra-high cooling rate (250~290℃ / min) combined with high-flow-rate convective heat dissipation" mechanism implemented in the second cooling stage of this application played a decisive role. This powerful cooling mechanism instantaneously crosses the harmful phase transition region in a hard-landing manner, completely intercepting the nucleation and precipitation of vanadium-rich σ-brittle intermetallic phases, ensuring a highly disordered soft magnetic state of the crystal lattice, thereby significantly reducing the envelope area of ​​the hysteresis loop (hysteresis loss) and effectively homogenizing local abnormal eddy currents (eddy current loss).

[0169] The experimental data in summary demonstrate that the complete set of full-time "temperature-pressure-flow" cascaded soft magnetic alloy annealing processes proposed in this application not only possesses extremely high originality in control logic, but also achieves outstanding technical results in the macroscopic properties of the final soft magnetic material (ultra-high and low field magnetic induction, ultra-low and high frequency iron loss), breaking through the performance bottleneck of the traditional 1J22 soft magnetic alloy heat treatment process.

[0170] In summary, the soft magnetic alloy all-hydrogen annealing process provided by the present invention has the following beneficial effects:

[0171] 1. Deep purification of the alloy was achieved through a closed-loop system of high-purity hydrogen atmosphere throughout the entire process.

[0172] This process uses high-purity hydrogen with a dew point ≤ -40℃ as a protective atmosphere throughout the annealing process, and establishes a continuous closed-loop guarantee of hydrogen quality through online dew point monitoring and interlocking. A dynamic balance method for the inlet and outlet gases is fully introduced during the replacement, heating, and holding stages. The furnace pressure and the large flow rate of inlet gas are physically decoupled by adjusting the resistance of the back pressure valve at the exhaust end. This maintains a strongly reducing atmosphere with extremely low water vapor and oxygen partial pressures within the annealing furnace. Harmful interstitial atoms such as carbon and oxygen that diffuse and agglomerate to the surface within the alloy matrix at high temperatures can undergo efficient interfacial reduction reactions. Furthermore, the trace amounts of gaseous products generated are instantly entrained and forcibly discharged by the directional convection flow field, disrupting the chemical equilibrium. Therefore, this process eliminates the pinning effect of impurity agglomeration on magnetic domain walls, significantly reducing the coercivity of the workpiece and improving its magnetic permeability.

[0173] 2. Through multi-stage dynamic coupling control of temperature, pressure and flow, the precipitation of harmful phases is precisely suppressed.

[0174] To address the problem of harmful phase precipitation such as the σ phase caused by an unreasonable cooling regime, this process designs a multi-stage cooling regime with differentiated cooling rates. In the first cooling stage, dynamic equilibrium is eliminated, and interval-type exhaust control based on preset upper and lower pressure limits is adopted to achieve uniform and slow cooling with a low flow rate, ensuring the consistency of workpiece temperature. In the second cooling stage, the cooling rate is rapidly increased to 250℃ / min to 290℃ / min, restoring the dynamic equilibrium of inlet and outlet gases, and using a large flow rate of high-purity hydrogen as the forced heat dissipation coolant to provide hydrodynamic support for the ultra-high cooling rate. Through the above mechanism, the alloy instantaneously crosses the sensitive temperature zone for σ phase precipitation in an extremely short time before microscopic atoms have time to undergo long-range diffusion, completely freezing the excellent soft magnetic structure at high temperature, forcibly intercepting the nucleation and precipitation of vanadium-rich σ intermetallic phase at grain boundaries, avoiding the pinning of magnetic domain walls, and minimizing the brittleness of the alloy.

[0175] 3. By employing a differentiated pressure control strategy, both temperature field uniformity and hydrogen embrittlement eradication are achieved.

[0176] In the sensitive temperature range of 740℃ to 760℃ for ordered phase transformation and stress relaxation, this process eliminates the dynamic balance of inlet and outlet gases. The protective hydrogen flow rate is reduced to 3L / min to 6L / min for passive charging, and an exhaust solenoid valve is used for interval switching control between a preset upper and lower pressure limit. When the furnace pressure reaches the upper limit threshold, the exhaust valve opens instantaneously, creating a transient pressure pulse. This generates a significant transient hydrogen partial pressure gradient between the workpiece matrix and the surface fluid, driving the desorption of supersaturated hydrogen atoms deep within the alloy lattice and expelling them from the furnace with the gas flow. In this way, this process eliminates the risk of hydrogen embrittlement in soft magnetic alloys during all-hydrogen annealing, significantly enhancing the material's mechanical toughness. Simultaneously, the ultra-low inlet flow rate avoids disturbances to the high-temperature uniform temperature field caused by external cold airflow.

[0177] 4. The active furnace pressure compensation mechanism ensures seamless connection of atmosphere protection across the entire temperature range.

[0178] In the final stage of cooling from approximately 440℃ to below 150℃, this process actively increases the hydrogen flow rate to 15L / min to 20L / min and tightens the back pressure valve, thus forcibly raising the furnace pressure to 6KPa to 8KPa. The high-density, all-hydrogen gas completely offsets the fluid thermal contraction negative pressure effect caused by the drastic temperature drop within the furnace, ensuring that the furnace pressure remains at an absolutely safe, slightly positive pressure level throughout the entire rapid cooling process at medium and low temperatures, completely preventing external oxygen from entering the furnace. Consequently, the annealed soft magnetic alloy workpiece exhibits near-zero deformation and a mirror-like, highly polished surface quality after exiting the furnace.

[0179] 5. The strong convective heat transfer characteristics of hydrogen and the synergistic effect of staged pressure-flow regulation ensured the high consistency of magnetic properties of batch products.

[0180] This process utilizes the higher thermal conductivity and strong convective heat transfer characteristics of hydrogen compared to vacuum. During the heating and holding stages, a dynamic balance of incoming and outgoing gas is employed to maintain a slight positive pressure within the furnace, ensuring a highly uniform temperature field, consistent heating across all parts of the workpiece, and uniform grain growth. Consequently, the consistency of the magnetic properties of the annealed alloy and the yield rate for mass production are significantly improved, effectively overcoming the sheet deformation and performance dispersion problems caused by uneven thermal fields in traditional annealing processes.

[0181] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An annealing process for soft magnetic alloys, characterized in that, include: Hydrogen is obtained and pretreated to obtain protective hydrogen that meets the preset purity and dew point indicators. A vacuum environment is established in an annealing furnace containing a soft magnetic alloy workpiece to be processed, and a pre-baking treatment is performed on the soft magnetic alloy workpiece under the vacuum environment to remove moisture and impurities from the surface of the soft magnetic alloy workpiece. The protective hydrogen gas is introduced into the annealing furnace to establish a first slightly positive pressure atmosphere inside the annealing furnace; The furnace temperature inside the annealing furnace is raised to the target annealing temperature range, and protective hydrogen is introduced in a dynamic balance manner during the heating stage to establish a second micro-positive pressure atmosphere inside the annealing furnace. The furnace is held at the target annealing temperature range for a first duration. During the holding period, the protective hydrogen is introduced in a dynamic balance manner to establish a third micro-positive pressure atmosphere in the annealing furnace with a furnace pressure lower than the second micro-positive pressure atmosphere. After the heat preservation stage, a multi-stage cooling operation is performed on the annealing furnace to obtain the annealed soft magnetic alloy workpiece; wherein, the multi-stage cooling operation includes: First cooling stage: Cooling to the second temperature range at a first cooling rate and holding at the temperature for a second duration, wherein the dynamic balance mode of inlet and outlet gas is cancelled during the first cooling stage, and the supply of protective hydrogen is maintained by exhaust pressure threshold control mode. Second cooling stage: Cooling from the second temperature range to the third temperature range at a second cooling rate greater than the first cooling rate, wherein the supply of protective hydrogen is restored and maintained by the dynamic balance of inlet and outlet gas during the second cooling stage. The third cooling stage: cooling from the third temperature range to the furnace exit temperature at a third cooling rate, wherein the supply of protective hydrogen is maintained by the dynamic balance of inlet and outlet gas during the third cooling stage.

2. The soft magnetic alloy annealing process as described in claim 1, characterized in that, Hydrogen gas is obtained and pretreated to obtain protective hydrogen gas that meets preset purity and dew point indicators, including: An initial hydrogen source is obtained, and phase separation and filtration operations are performed on the initial hydrogen source to remove liquid water and solid impurities from the initial hydrogen source and obtain intermediate hydrogen. The intermediate hydrogen is subjected to a deep adsorption drying operation to remove trace amounts of residual moisture from the intermediate hydrogen, thereby obtaining the protective hydrogen. The preset purity index is a purity of not less than 99.999%, and the preset dew point index is a dew point of not higher than -40℃.

3. The soft magnetic alloy annealing process as described in claim 2, characterized in that, After obtaining the protective hydrogen gas but before introducing it into the annealing furnace, the process further includes: Online dew point monitoring is performed on the protective hydrogen to obtain the real-time dew point characteristic value of the protective hydrogen; The real-time dew point feature value is compared and evaluated with the preset dew point index; In response to the evaluation result that the real-time dew point characteristic value deviates from the preset dew point index, a gas supply status intervention operation is triggered and executed to restrict hydrogen that does not meet the index from entering the annealing furnace.

4. The soft magnetic alloy annealing process as described in claim 1, characterized in that, A vacuum environment is established within an annealing furnace containing the soft magnetic alloy workpiece to be processed, and a pre-baking treatment is performed on the soft magnetic alloy under this vacuum environment, including: The absolute vacuum level inside the annealing furnace is controlled to be below 1.0 × 10⁻⁶. -3 Pa; The soft magnetic alloy workpiece to be treated is heated to 150°C to 200°C at a heating rate of 5°C / min to 8°C / min, and held at that temperature for 1 hour to 2 hours to remove moisture and impurities from the surface of the soft magnetic alloy workpiece.

5. The soft magnetic alloy annealing process as described in claim 1, characterized in that, Introducing the protective hydrogen gas into the annealing furnace to establish a first slightly positive pressure atmosphere within the furnace includes: The protective hydrogen gas is introduced into the annealing furnace, and the furnace pressure is increased to the initial slightly positive pressure range within 10 minutes, wherein the furnace pressure corresponding to the initial slightly positive pressure range is between 3 kPa and 5 kPa. After reaching the initial slightly positive pressure range, the gas inlet and outlet dynamic balance method is adopted to introduce protective hydrogen at an inlet flow rate of 10 L / min to 15 L / min based on the furnace volume per cubic meter to perform gas replacement operation, so as to establish the first slightly positive pressure atmosphere with a furnace pressure of 5 kPa to 10 kPa in the annealing furnace.

6. The soft magnetic alloy annealing process as described in claim 1, characterized in that, The furnace temperature is raised to the target annealing temperature range, and protective hydrogen is introduced during the heating phase using a dynamic balance method for inlet and outlet gas to establish a second slightly positive pressure atmosphere within the annealing furnace, including: The furnace temperature of the annealing furnace is raised to the target annealing temperature range of 850°C to 890°C at a heating rate of 5°C / min to 10°C / min. During the heating stage, the gas flow rate is adjusted to 20 L / min to 25 L / min per cubic meter of furnace volume, and the protective hydrogen is introduced in a dynamic balance manner to establish a second slightly positive pressure atmosphere with a furnace pressure of 8 kPa to 12 kPa in the annealing furnace.

7. The soft magnetic alloy annealing process as described in claim 1, characterized in that, Holding the furnace at the target annealing temperature range for a first duration, and during the holding phase, maintaining the dynamic balance between the incoming and outgoing gases while introducing protective hydrogen, to establish a third slightly positive pressure atmosphere in the annealing furnace with a furnace pressure lower than the second slightly positive pressure atmosphere, including: After entering the heat preservation stage, the air inlet flow rate of the annealing furnace is reduced from the air inlet flow rate during the heating stage to 6 L / min to 8 L / min per cubic meter of furnace volume, so as to establish the third micro-positive pressure atmosphere with a furnace pressure of 2 kPa to 3 kPa in the annealing furnace. The first duration ranges from 4 to 6 hours, and for every 1 kilogram increase in the weight of the soft magnetic alloy workpiece to be processed based on the preset benchmark weight, the corresponding first duration increases linearly by 5 minutes proportionally to the preset benchmark duration.

8. The soft magnetic alloy annealing process as described in claim 1, characterized in that, The first cooling rate is 100℃ / min to 150℃ / min, the second temperature range is 740℃ to 760℃, and the second duration is 1 hour to 2 hours; as well as The supply of protective hydrogen is maintained by using an exhaust pressure threshold control method, including: setting the opening pressure threshold of the exhaust solenoid valve to 8 kPa to 10 kPa, setting the closing pressure threshold of the exhaust solenoid valve to 2 kPa to 3 kPa, and adjusting the inlet flow rate of the protective hydrogen to 3 L / min to 6 L / min based on the furnace volume per cubic meter.

9. The soft magnetic alloy annealing process as described in claim 1, characterized in that, The second cooling rate is 250°C / min to 290°C / min, and the third temperature range is 440°C to 460°C. as well as The supply of protective hydrogen is restored and maintained in the second cooling stage using the dynamic balance of inlet and outlet gas, including: maintaining the furnace pressure at 4 kPa to 6 kPa, and the inlet flow rate of the protective hydrogen is 10 L / min to 15 L / min per cubic meter of furnace volume.

10. The soft magnetic alloy annealing process as described in claim 1, characterized in that, The third cooling rate is 220℃ / min to 260℃ / min, and the furnace exit temperature is not higher than 150℃; and In the third cooling stage, the supply of protective hydrogen is maintained by the dynamic balance of inlet and outlet gas, including: maintaining the furnace pressure at 6 kPa to 8 kPa, and the inlet flow rate of the protective hydrogen is 15 L / min to 20 L / min per cubic meter of furnace volume.

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