Heat treatment process for motor iron core for new energy vehicle

Abstract

The invention discloses a heat treatment process for a motor iron core for a new energy vehicle, and particularly relates to the technical field of new energy vehicle motor treatment, a bionic channel is constructed through halophilic bacteria biological deposition and axial polarization, a composite coating is formed in combination with ferrite / silicon nitride double-target magnetron sputtering, and nitrogen element distribution is optimized by adopting multi-stage gradient nitriding treatment. Grain orientation is regulated and controlled through linear gradient magnetic field annealing, and an alternating attenuation magnetic field is innovatively introduced to assist silicone oil-based fluid cooling. Through the synergistic effect of magnetic field parameters and thermodynamic conditions in each process stage, the high-frequency magnetic hysteresis loss and eddy-current loss of the iron core are remarkably reduced, the interface bonding strength and mechanical bearing capacity of the coating are improved, meanwhile, a functional transition layer is formed, and the corrosion resistance is enhanced; and the iron core assembly with the characteristics of low loss and high reliability is provided for the driving motor of the new energy automobile.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle motor processing technology, and in particular to a heat treatment process for the iron core of a new energy vehicle motor. Background Technology

[0002] The core of motors used in new energy vehicles is generally made of silicon steel strip, which is stamped and then subjected to annealing, nitriding, and insulating coating processes to improve its electromagnetic performance. Existing technologies mostly employ step-by-step heat treatment, including conventional protective atmosphere annealing, plasma nitriding, and magnetron sputtering coating processes, to reduce iron loss by eliminating internal stress and optimizing grain structure.

[0003] Existing technologies suffer from drawbacks such as low nitriding efficiency, poor temperature uniformity during annealing, and insufficient adhesion between the insulating layer and the substrate. Traditional magnetic field annealing makes it difficult to precisely control grain boundary orientation, and bio-templating technology has not yet been effectively integrated with the nitriding process, resulting in high high-frequency losses and limited improvement in mechanical properties.

[0004] Therefore, the present invention provides a heat treatment process for the iron core of a motor for new energy vehicles. Summary of the Invention

[0005] The main objective of this invention is to provide a heat treatment process for motor cores in new energy vehicles. By constructing nitrogen diffusion channels through biomineralization and coupling gradient magnetic field dynamic annealing technology, the microstructure of the core is optimized and its performance is synergistically improved.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A heat treatment process for the iron core of a motor used in new energy vehicles includes the following steps:

[0008] Step 1: After cleaning the surface of the silicon steel strip substrate, biofilm deposition is carried out using halophilic bacteria culture medium, and polarization treatment is performed in an axial magnetic field environment;

[0009] Step 2: The substrate treated in Step 1 is subjected to dual-target co-sputtering using a ferrite target and a silicon nitride target in a vacuum magnetron sputtering equipment, and an alternating magnetic field is applied simultaneously to form a composite coating.

[0010] Step 3: Place the substrate treated in Step 2 into a plasma nitriding furnace and sequentially perform a preheating stage at 400°C, a main nitriding stage at 520°C, and a diffusion stage at 580°C.

[0011] Step 4: Place the nitrided iron core in a gradient magnetic field annealing furnace for dynamic annealing treatment, control the linear change of the axial magnetic field strength and maintain a constant radial magnetic field.

[0012] Step 5: Apply an alternating decaying magnetic field in an inert gas cooling chamber and spray silicone oil-based fluid. After cooling, the finished iron core is obtained.

[0013] Preferably, the thickness of the silicon steel strip in step 1 is 0.20-0.25 mm, the concentration of the halophilic bacteria culture medium is 3%-7%, and the polarization treatment axial magnetic field strength is 0.5 T.

[0014] Preferably, the biofilm deposition conditions in step 1 are a temperature of 38°C, a pH of 7.2, and a duration of 24 hours, after which the protein network forms biomimetic channels with a spacing of 200-300 nm.

[0015] Preferably, in step 2, the power ratio of the ferrite target to the silicon nitride target is 3:1, the substrate temperature is 150°C, the coating thickness is 1.2μm, and the applied alternating magnetic field strength is 0.8T with a frequency of 50Hz.

[0016] Preferably, in step 3: during the 400℃ preheating stage, a mixed gas of NH3 and Ar with a volume ratio of 1:(3-5) is introduced and maintained at 300Pa pressure for 30 minutes; during the 520℃ main diffusion stage, plasma with a volume ratio of H2 and N2 of 20%:80% is used and a 10kHz, 1.2T pulsed magnetic field is applied; during the 580℃ diffusion stage, a 0.5T DC magnetic field is switched to control the surface nitrogen potential KN to decrease from 0.35 to 0.15, and the total treatment time is 4 hours.

[0017] Preferably, in step 4, the axial magnetic field strength decreases linearly from 1.8T to 0.5T to form a gradient of 0.3T / cm, while the radial field remains constant at 0.3T. The protective atmosphere contains 0.03-0.007 vol% hexamethyldisilazane.

[0018] Preferably, in step 4, the heating rate is 15℃ / min, the holding temperature is 820℃, the holding time is 23 minutes, and the protective atmosphere dew point is -60℃.

[0019] Preferably, in step 5, the initial strength of the alternating decaying magnetic field is 0.6T and the frequency is 1kHz, and it decays to 0T at a rate of 0.1T per second within 6s. The silicone oil-based fluid contains 1-3wt% Y2O3 nanoparticles to form an 8-10μm functional transition layer.

[0020] Preferably, step 5 is initiated when the temperature drops to 740°C, and the cooling endpoint temperature is 150°C.

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

[0022] This invention constructs a biomimetic nitrogen diffusion channel using a halophilic bacteria biotemplate, combines it with dual-target magnetron sputtering to form a gradient composite coating, utilizes a pulsed magnetic field to regulate the plasma nitriding process, and employs dynamic annealing with an axial gradient magnetic field and stabilization treatment with an alternating decaying magnetic field. This significantly improves the nitrogen penetration efficiency while optimizing the grain boundary orientation distribution, effectively improving the temperature field uniformity during annealing, enhancing the interfacial bonding strength between the insulating coating and the substrate, and simultaneously reducing the high-frequency eddy current loss and hysteresis loss of the iron core. This achieves a synergistic improvement in electromagnetic performance and mechanical strength, while ensuring the controllability and repeatability of the process. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0024] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0025] like Figure 1 As shown, this invention discloses a heat treatment process for the iron core of a motor used in new energy vehicles, and the specific steps are as follows:

[0026] Step 1: After cleaning the surface of the silicon steel strip substrate, biofilm deposition is carried out using halophilic bacteria culture medium, and polarization treatment is performed in an axial magnetic field environment;

[0027] Step 2: The substrate treated in Step 1 is subjected to dual-target co-sputtering using a ferrite target and a silicon nitride target in a vacuum magnetron sputtering equipment, and an alternating magnetic field is applied simultaneously to form a composite coating.

[0028] Step 3: Place the substrate treated in Step 2 into a plasma nitriding furnace and sequentially perform a preheating stage at 400°C, a main nitriding stage at 520°C, and a diffusion stage at 580°C.

[0029] Step 4: Place the nitrided iron core in a gradient magnetic field annealing furnace for dynamic annealing treatment, control the linear change of the axial magnetic field strength and maintain a constant radial magnetic field.

[0030] Step 5: Apply an alternating decaying magnetic field in an inert gas cooling chamber and spray silicone oil-based fluid. After cooling, the finished iron core is obtained.

[0031] Example 1

[0032] Step 1: After cleaning the surface of the 0.20mm thick silicon steel strip substrate, biofilm deposition was carried out in a 3% concentration halophilic bacteria culture medium at 38℃ and pH 7.2 for 24 hours. Subsequently, polarization treatment was carried out in a 0.5T axial magnetic field environment to form a biomimetic protein network channel with a spacing of 200nm.

[0033] Step 2: Place the treated substrate in a vacuum magnetron sputtering equipment and perform dual-target co-sputtering using a ferrite target and a silicon nitride target with a power ratio of 3:1 to form a 1μm composite coating at a substrate temperature of 150℃. Simultaneously apply an alternating magnetic field with an intensity of 0.8T and a frequency of 50Hz.

[0034] Step 3: The substrate is placed in a plasma nitriding furnace for three stages of treatment: a preheating stage at 400℃, in which a mixed gas of NH3 and Ar in a volume ratio of 1:3 is introduced and maintained at 300Pa pressure for 30 minutes; a main nitriding stage at 520℃, in which plasma of H2 and N2 in a volume ratio of 20%:80% is used and a 10kHz, 1.2T pulsed magnetic field is applied; and a diffusion stage at 580℃, in which a 0.5T DC magnetic field is switched to control the surface nitrogen potential KN to decrease linearly from 0.35 to 0.15, with a total treatment time of 4 hours.

[0035] Step 4: After nitriding, the iron core is heated to 820℃ at a rate of 15℃ / min in a gradient magnetic field annealing furnace. The axial magnetic field strength is linearly reduced from 1.8T to 0.5T to form a gradient of 0.3T / cm, while the radial field is kept constant at 0.3T. The core is held for 23 minutes in a protective atmosphere containing 0.03 vol% hexamethyldisilazane, with the dew point controlled at -60℃.

[0036] Step 5: When the temperature drops to 740℃, the iron core is transferred to the inert gas cooling chamber, and an alternating decaying magnetic field with an initial strength of 0.6T and a frequency of 1kHz is applied, decaying to 0T within 6 seconds at a rate of 0.1T / s. At the same time, a silicone oil-based fluid containing 1wt% nanoparticles is sprayed, and finally cooled to 150℃ to form an 8μm functional transition layer, thus obtaining the motor iron core.

[0037] Example 2

[0038] Step 1: After cleaning the surface of the 0.22mm thick silicon steel strip substrate, biofilm deposition was carried out in a 4% concentration of halophilic bacteria culture medium at 38℃ and pH 7.2 for 24 hours. Subsequently, polarization treatment was carried out in a 0.5T axial magnetic field environment to form a biomimetic protein network channel with a spacing of 230nm.

[0039] Step 2: Place the treated substrate in a vacuum magnetron sputtering equipment and perform dual-target co-sputtering using a ferrite target and a silicon nitride target with a power ratio of 3:1 to form a 1μm composite coating at a substrate temperature of 150℃. Simultaneously apply an alternating magnetic field with an intensity of 0.8T and a frequency of 50Hz.

[0040] Step 3: The substrate is placed in a plasma nitriding furnace for three stages of treatment: a preheating stage at 400℃, in which a mixed gas of NH3 and Ar in a volume ratio of 1:4 is introduced and maintained at 300Pa pressure for 30 minutes; a main nitriding stage at 520℃, in which plasma of H2 and N2 in a volume ratio of 20%:80% is used and a 10kHz, 1.2T pulsed magnetic field is applied; and a diffusion stage at 580℃, in which a 0.5T DC magnetic field is switched to control the surface nitrogen potential KN to decrease linearly from 0.35 to 0.15, with a total treatment time of 4 hours.

[0041] Step 4: After nitriding, the iron core is heated to 820℃ at a rate of 15℃ / min in a gradient magnetic field annealing furnace. The axial magnetic field strength is linearly reduced from 1.8T to 0.5T to form a gradient of 0.3T / cm, while the radial field is kept constant at 0.3T. The core is held for 23 minutes in a protective atmosphere containing 0.04 vol% hexamethyldisilazane, with the dew point controlled at -60℃.

[0042] Step 5: When the temperature drops to 740℃, the iron core is transferred to the inert gas cooling chamber, and an alternating decaying magnetic field with an initial strength of 0.6T and a frequency of 1kHz is applied, decaying to 0T within 6 seconds at a rate of 0.1T / s. At the same time, a silicone oil-based fluid containing 2wt% nanoparticles is sprayed, and finally cooled to 150℃ to form an 8μm functional transition layer, thus obtaining the motor iron core.

[0043] Example 3

[0044] Step 1: After cleaning the surface of the 0.23mm thick silicon steel strip substrate, biofilm deposition was carried out in a 5% concentration of halophilic bacteria culture medium at 38℃ and pH 7.2 for 24 hours. Subsequently, polarization treatment was carried out in a 0.5T axial magnetic field environment to form a biomimetic protein network channel with a spacing of 250nm.

[0045] Step 2: Place the treated substrate in a vacuum magnetron sputtering equipment and perform dual-target co-sputtering using a ferrite target and a silicon nitride target with a power ratio of 3:1 to form a 1.2μm composite coating at a substrate temperature of 150℃, while simultaneously applying an alternating magnetic field with an intensity of 0.8T and a frequency of 50Hz.

[0046] Step 3: The substrate is placed in a plasma nitriding furnace for three stages of treatment: a preheating stage at 400℃, in which a mixed gas of NH3 and Ar in a volume ratio of 1:4 is introduced and maintained at 300Pa pressure for 30 minutes; a main nitriding stage at 520℃, in which plasma of H2 and N2 in a volume ratio of 20%:80% is used and a 10kHz, 1.2T pulsed magnetic field is applied; and a diffusion stage at 580℃, in which a 0.5T DC magnetic field is switched to control the surface nitrogen potential KN to decrease linearly from 0.35 to 0.15, with a total treatment time of 4 hours.

[0047] Step 4: After nitriding, the iron core is heated to 820℃ at a rate of 15℃ / min in a gradient magnetic field annealing furnace. The axial magnetic field strength is linearly reduced from 1.8T to 0.5T to form a gradient of 0.3T / cm, while the radial field is kept constant at 0.3T. The core is held for 23 minutes in a protective atmosphere containing 0.05 vol% hexamethyldisilazane, with the dew point controlled at -60℃.

[0048] Step 5: When the temperature drops to 740℃, the iron core is transferred to the inert gas cooling chamber, and an alternating decaying magnetic field with an initial strength of 0.6T and a frequency of 1kHz is applied, decaying to 0T within 6 seconds at a rate of 0.1T / s. At the same time, a silicone oil-based fluid containing 2wt% nanoparticles is sprayed, and finally cooled to 150℃ to form a 9μm functional transition layer, thus obtaining the motor iron core.

[0049] Example 4

[0050] Step 1: After cleaning the surface of the 0.24mm thick silicon steel strip substrate, biofilm deposition was carried out in a 6% concentration of halophilic bacteria culture medium at 38℃ and pH 7.2 for 24 hours. Subsequently, polarization treatment was carried out in a 0.5T axial magnetic field environment to form a biomimetic protein network channel with a spacing of 270nm.

[0051] Step 2: Place the treated substrate in a vacuum magnetron sputtering equipment and perform dual-target co-sputtering using a ferrite target and a silicon nitride target with a power ratio of 3:1 to form a 1μm composite coating at a substrate temperature of 150℃. Simultaneously apply an alternating magnetic field with an intensity of 0.8T and a frequency of 50Hz.

[0052] Step 3: The substrate is placed in a plasma nitriding furnace for three stages of treatment: a preheating stage at 400℃, in which a mixed gas of NH3 and Ar in a volume ratio of 1:5 is introduced and maintained at 300Pa pressure for 30 minutes; a main nitriding stage at 520℃, in which plasma of H2 and N2 in a volume ratio of 20%:80% is used and a 10kHz, 1.2T pulsed magnetic field is applied; and a diffusion stage at 580℃, in which a 0.5T DC magnetic field is switched to control the surface nitrogen potential KN to decrease linearly from 0.35 to 0.15, with a total treatment time of 4 hours.

[0053] Step 4: After nitriding, the iron core is heated to 820℃ at a rate of 15℃ / min in a gradient magnetic field annealing furnace. The axial magnetic field strength is linearly reduced from 1.8T to 0.5T to form a gradient of 0.3T / cm, while the radial field is kept constant at 0.3T. The core is held for 23 minutes in a protective atmosphere containing 0.06 vol% hexamethyldisilazane, with the dew point controlled at -60℃.

[0054] Step 5: When the temperature drops to 740℃, the iron core is transferred to the inert gas cooling chamber, and an alternating decaying magnetic field with an initial strength of 0.6T and a frequency of 1kHz is applied, decaying to 0T within 6 seconds at a rate of 0.1T / s. At the same time, a silicone oil-based fluid containing 2wt% nanoparticles is sprayed, and finally cooled to 150℃ to form a 10μm functional transition layer, thus obtaining the motor iron core.

[0055] Example 5

[0056] Step 1: After cleaning the surface of the 0.25mm thick silicon steel strip substrate, biofilm deposition was carried out in a 7% concentration halophilic bacteria culture medium at 38℃ and pH 7.2 for 24 hours. Subsequently, polarization treatment was carried out in a 0.5T axial magnetic field environment to form a biomimetic protein network channel with a spacing of 200-300nm.

[0057] Step 2: Place the treated substrate in a vacuum magnetron sputtering equipment and perform dual-target co-sputtering using a ferrite target and a silicon nitride target with a power ratio of 3:1 to form a 1.2μm composite coating at a substrate temperature of 150℃, while simultaneously applying an alternating magnetic field with an intensity of 0.8T and a frequency of 50Hz.

[0058] Step 3: The substrate is placed in a plasma nitriding furnace for three stages of treatment: a preheating stage at 400℃, in which a mixed gas of NH3 and Ar in a volume ratio of 1:4 is introduced and maintained at 300Pa pressure for 30 minutes; a main nitriding stage at 520℃, in which plasma of H2 and N2 in a volume ratio of 20%:80% is used and a 10kHz, 1.2T pulsed magnetic field is applied; and a diffusion stage at 580℃, in which a 0.5T DC magnetic field is switched to control the surface nitrogen potential KN to decrease linearly from 0.35 to 0.15, with a total treatment time of 4 hours.

[0059] Step 4: After nitriding, the iron core is heated to 820℃ at a rate of 15℃ / min in a gradient magnetic field annealing furnace. The axial magnetic field strength is linearly reduced from 1.8T to 0.5T to form a gradient of 0.3T / cm, while the radial field is kept constant at 0.3T. The core is held for 23 minutes in a protective atmosphere containing 0.05 vol% hexamethyldisilazane, with the dew point controlled at -60℃.

[0060] Step 5: When the temperature drops to 740℃, the iron core is transferred to the inert gas cooling chamber, and an alternating decaying magnetic field with an initial strength of 0.6T and a frequency of 1kHz is applied, decaying to 0T within 6 seconds at a rate of 0.1T / s. At the same time, a silicone oil-based fluid containing 3wt% nanoparticles is sprayed, and finally cooled to 150℃ to form a 10μm functional transition layer, thus obtaining the motor iron core.

[0061] Comparative Example 1

[0062] The similarities between this comparative example and Example 1 will not be repeated; only the differences between this comparative example and Example 1 will be described:

[0063] Step 1: Acid washing with 5% hydrochloric acid solution instead of biodeposition; Step 2: Single-target ferrite sputtering; Step 4: Conventional annealing; Step 5: Natural cooling without magnetic field treatment. This is equivalent to Example 1.

[0064] Comparative Example 2

[0065] The similarities between this comparative example and Example 1 will not be repeated; only the differences between this comparative example and Example 1 will be described:

[0066] Step 3: Cancel the pulsed magnetic field and use conventional nitriding; Step 4: Isothermal magnetic field annealing, other steps are the same as in Example 1.

[0067] The samples obtained from Examples 1-5 and Comparative Examples 1-2 were subjected to the following tests, and the test results are shown in Table 1:

[0068] I. Core loss test: The Epstein square ring tester conforming to IEC 60404-8 standard was used for testing. Under the conditions of magnetic flux density of 1.5T and frequency of 400Hz, the sample was placed in a constant temperature environment of 120℃, and the specific loss value (W / kg) of the core per unit mass was determined by power analysis method. This test can effectively characterize the hysteresis loss characteristics of the material under high frequency conditions.

[0069] II. High-frequency eddy current loss characteristics were tested using a PPMS-9T BH analyzer. In the wide frequency range of 1kHz to 20kHz, the proportion of eddy current loss components when the magnetic flux density B = 1.0T was measured using lock-in amplifier technology. During the test, the sample temperature was kept at 25±0.5℃ to eliminate measurement errors caused by temperature rise.

[0070] III. Mechanical Strength Test: In accordance with ASTM E8 standard specifications, an electronic universal testing machine equipped with a ring clamp was used to conduct a radial compression test on a ring core specimen with a specification of Φ50×Φ30×10mm. The displacement rate of the crosshead was controlled at 1mm / min, and the compressive strength value when the specimen underwent 0.2% plastic deformation was recorded. This parameter can reflect the deformation resistance of the core assembly during the motor assembly process.

[0071] Table 1: Test results data for Examples 1-5 and Comparative Examples 1-2.

[0072]

[0073] Experimental data show that the embodiments of the present invention exhibit significant performance advantages compared to traditional processes. Example 3 achieved an excellent specific loss of 10.5 W / kg, a reduction of over 13 W / kg compared to Comparative Example 1's 23.6 W / kg. This is attributed to the biomimetic channels formed by biofilm deposition effectively optimizing the magnetic domain structure, and the gradient annealing process improving grain orientation consistency, thus significantly reducing energy loss. Comparative Example 2, due to the elimination of pulsed magnetic field nitriding, still showed a significantly higher loss value of 18.7 W / kg compared to all other examples, demonstrating the crucial role of magnetic field control in achieving uniform nitriding.

[0074] In the coating adhesion test, the critical load of Example 3 reached 47.8 N, nearly 30 N higher than that of Comparative Example 1 (18.3 N). This is attributed to the chemical bonding between the three-dimensional protein network formed by biodeposition and the magnetron sputtered coating. Although Comparative Example 2 used biodeposition but did not undergo gradient annealing, its critical load of 32.6 N was still significantly lower than that of the Example group, indicating that dynamic magnetic field treatment is irreplaceable for eliminating interfacial stress.

[0075] High-frequency eddy current loss data show that Example 3, with a loss ratio of 6.5% at 20kHz, is significantly lower than Comparative Example 2's 15.3%. This is attributed to the effective suppression of eddy current paths by the insulating network structure formed by the composite coating. Comparative Example 1, lacking magnetic field-assisted cooling, exhibits a loss value of 22.4%, revealing severe electron scattering, further validating the innovative value of the cooling process of this invention.

[0076] In terms of mechanical strength, Example 5 exhibited the best compressive strength of 391 MPa, an improvement of over 170 MPa compared to Comparative Example 1's 215 MPa. The application of the pulsed magnetic field during the plasma nitriding stage increased the depth of the reinforcing layer, and the surface compressive stress system formed by the protective atmosphere significantly enhanced structural stability. Comparative Example 2, due to isothermal annealing, showed a strength value of 298 MPa that decreased by nearly 100 MPa compared to Example 5, demonstrating the crucial role of the gradient magnetic field in eliminating internal stress in the material.

[0077] Table 1 data confirms that the present invention achieves performance breakthroughs through the synergistic effect of multiple processes. Example 3 achieves the optimal balance between specific loss and binding force, with its synergistic advantage of a loss value of 10.5 W / kg and a binding force of 47.8 N stemming from the complete biofilm formed at a concentration of 5% halophilic bacteria, the electromagnetic optimization of the 1.2 μm composite coating, and the fine grain structure controlled by a gradient magnetic field. Comparative data further validate the necessity of core processes such as biodeposition, dual-target sputtering, and dynamic annealing.

[0078] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A heat treatment process for the iron core of a motor used in new energy vehicles, characterized in that, The steps include: Step 1: After cleaning the surface of the silicon steel strip substrate, biofilm deposition is carried out using halophilic bacteria culture medium, and polarization treatment is performed in an axial magnetic field environment; Step 2: The substrate treated in Step 1 is subjected to dual-target co-sputtering using a ferrite target and a silicon nitride target in a vacuum magnetron sputtering equipment, and an alternating magnetic field is applied simultaneously to form a composite coating. Step 3: Place the substrate treated in Step 2 into a plasma nitriding furnace and sequentially perform a preheating stage at 400°C, a main nitriding stage at 520°C, and a diffusion stage at 580°C. Step 4: Place the nitrided iron core in a gradient magnetic field annealing furnace for dynamic annealing treatment, control the linear change of the axial magnetic field strength and maintain a constant radial magnetic field. Step 5: Apply an alternating decaying magnetic field in an inert gas cooling chamber and spray silicone oil-based fluid. After cooling, the finished iron core is obtained.

2. The heat treatment process for the core of a motor for new energy vehicles according to claim 1, characterized in that, The thickness of the silicon steel strip in step 1 is 0.20-0.25 mm, the concentration of the halophilic bacteria culture medium is 3%-7%, and the polarization treatment axial magnetic field strength is 0.5 T.

3. The heat treatment process for the motor core of a new energy vehicle according to claim 2, characterized in that, In step 1, the biofilm deposition conditions are 38°C, pH 7.2, and duration of 24 hours. After polarization treatment, the protein network forms biomimetic channels with a spacing of 200-300 nm.

4. The heat treatment process for the core of a motor for new energy vehicles according to claim 1, characterized in that, In step 2, the power ratio of the ferrite target to the silicon nitride target is 3:1, the substrate temperature is 150℃, the coating thickness is 1.2μm, and the applied alternating magnetic field strength is 0.8T with a frequency of 50Hz.

5. The heat treatment process for the core of a motor for new energy vehicles according to claim 1, characterized in that, In step 3: during the 400℃ preheating stage, a mixed gas of NH3 and Ar with a volume ratio of 1:(3-5) is introduced and maintained at 300Pa pressure for 30 minutes; during the 520℃ main diffusion stage, plasma with a volume ratio of H2 and N2 of 20%:80% is used and a 10kHz, 1.2T pulsed magnetic field is applied; during the 580℃ diffusion stage, a 0.5T DC magnetic field is switched to control the surface nitrogen potential KN to decrease from 0.35 to 0.15, and the total treatment time is 4 hours.

6. The heat treatment process for the core of a motor for new energy vehicles according to claim 1, characterized in that, In step 4, the axial magnetic field strength decreases linearly from 1.8T to 0.5T to form a gradient of 0.3T / cm, while the radial field remains constant at 0.3T. The protective atmosphere contains 0.03-0.007 vol% hexamethyldisilazane.

7. The heat treatment process for the core of a motor for new energy vehicles according to claim 6, characterized in that, Step 4: Heating rate 15℃ / min, holding temperature 820℃, holding time 23 minutes, protective atmosphere dew point -60℃.

8. The heat treatment process for the core of a motor for new energy vehicles according to claim 1, characterized in that, In step 5, the initial strength of the alternating decaying magnetic field is 0.6T and the frequency is 1kHz. It decays to 0T at a rate of 0.1T per second within 6s. The silicone oil-based fluid contains 1-3wt% Y2O3 nanoparticles to form an 8-10μm functional transition layer.

9. The heat treatment process for the core of a motor for new energy vehicles according to claim 8, characterized in that, Step 5 is initiated when the temperature drops to 740°C, and the final cooling temperature is 150°C.

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