Vacuum annealing process for low-coercive-force magnetic shell of low-carbon and environment-friendly automobile electronic control motor

Abstract

The invention provides a low-carbon green automobile electric control motor low-coercivity magnetic shell vacuum annealing process, and relates to the field of heat treatment, and the process sequentially comprises the following steps: 1, carrying out vacuum cleaning on a magnetic shell workpiece; 2, the magnetic shell workpiece is loaded into a vacuum gas quenching furnace, and the vacuum gas quenching furnace is pre-vacuumized; 3, protective gas is introduced into the vacuum gas quenching furnace, and first heating and heat preservation are conducted through convection heating; 4, heating for the second time by using convection heating, stopping introducing the protective gas after the temperature is reached, and vacuumizing and preserving heat; 5, the magnetic shell workpiece is slowly cooled by controlling the cooling speed; 6, a forced cooling system is started for gas quenching; and 7, the magnetic shell workpiece is taken out. Cracking gas such as methanol is not used as a protective atmosphere, so that raw materials are saved, and carbon emission is reduced; nitrogen is filled in the heating process, adhesion of the workpiece is reduced, the coercive force of the workpiece can be reduced, the structure of the workpiece is uniform, and oxidation of the workpiece is prevented.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment, in particular to a vacuum annealing process for a low-carbon, green automobile electronic control motor with a low coercive force magnetic shell. Background Art

[0002] The magnetic shell is a key component in various automotive electronic control motor systems. As a key component of these motors, the magnetic shell is made of DC04 (cold-rolled low-carbon steel). To improve motor efficiency, a uniform magnetic shell structure and low coercivity are required.

[0003] The existing cold-rolled low-carbon steel annealing process (such as CN119843023A, a low-cost production method for cold-rolled low-carbon steel strip with high plastic deformation ability) usually does not have a cleaning process that affects the quality of the workpiece, and uses radiation heating to affect temperature uniformity and thus affect the quality of the workpiece. The fixed heating rate can easily lead to uneven workpiece structure, and the environment is usually non-vacuum. These factors combined lead to obvious shortcomings in product performance and stability. Summary of the Invention

[0004] The present invention provides a vacuum annealing process for a low-coercivity magnetic shell of a low-carbon, green automotive electronic control motor, which is used to solve at least one of the technical problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention discloses a vacuum annealing process for a low-coercivity magnetic shell of a low-carbon, green automotive electronic control motor, which comprises the following steps in sequence:

[0006] Step 1: Vacuum clean the magnetic shell workpiece;

[0007] Step 2: Place the magnetic shell workpiece into a vacuum gas quenching furnace and pre-evacuate the vacuum gas quenching furnace;

[0008] Step 3: A protective gas is introduced into the vacuum gas quenching furnace, and convection heating is used for the first heating and heat preservation;

[0009] Step 4: Use convection heating to raise the temperature for the second time. After reaching the temperature, stop introducing the protective gas and evacuate to keep warm.

[0010] Step 5: Slowly cool the magnetic shell workpiece by controlling the cooling speed;

[0011] Step 6: Turn on the forced cooling system for gas quenching;

[0012] Step 7: Remove the magnetic shell workpiece.

[0013] Preferably, the step 1 comprises:

[0014] Step 11: Send the magnetic shell workpiece into the vacuum cleaning machine;

[0015] Step 12: Ultrasonic immersion of the magnetic shell workpiece for 400-600 seconds;

[0016] Step 13: Spray the magnetic shell workpiece for 440s~640s;

[0017] Step 14: Dry the magnetic shell workpiece for 800s~1200s.

[0018] Preferably, the step 2 comprises:

[0019] Step 21: Send the vacuum-cleaned magnetic shell workpiece into a vacuum gas quenching furnace;

[0020] Step 22: Pre-evacuate the vacuum gas quenching furnace to a vacuum degree of ≤1.0×10 -2 Pa.

[0021] Preferably, step 3 includes:

[0022] Step 31: introducing nitrogen gas with a purity of ≥99.99% into the vacuum gas quenching furnace to a pressure of 100-200 kPa;

[0023] Step 32: Raise the furnace temperature to 790-810°C at a heating rate of 10-20°C / min and keep it at that temperature for 25-35 minutes.

[0024] Preferably, step 4 includes:

[0025] Step 41: Continue to introduce nitrogen gas with a purity of ≥99.99% into the vacuum gas quenching furnace until the pressure reaches 100-200 kPa;

[0026] Step 42: After raising the furnace temperature to 830-850°C at a heating rate of 1-2°C / min, stop introducing nitrogen, continue vacuuming, and keep the temperature for 170-190 minutes.

[0027] Preferably, in step 5, the furnace temperature is cooled to 490-510° C. at a cooling rate of 1-2° C. / min;

[0028] Step 6 includes: introducing nitrogen with a purity of ≥99.99% and maintaining the pressure of the vacuum gas quenching furnace at 150-250 kPa for gas quenching;

[0029] In step 7, the magnetic shell workpiece is taken out after the furnace temperature is ≤50°C.

[0030] Preferably, before the current batch of magnetic shell workpieces is placed in a vacuum gas quenching furnace for annealing, a target annealing parameter determination process is first performed. The target annealing parameter determination process includes:

[0031] Step 01: Obtain the required nitrogen pressure range and required Reynolds number range for the heating process of step 3 of the current magnetic shell workpiece, obtain a mapping table of the first nitrogen pressure-heat exchange efficiency-temperature non-uniformity of all workpiece placement areas, and obtain a mapping table of the first nitrogen pressure-theoretical speed of the fan that maintains the nitrogen Reynolds number in the vacuum gas quenching furnace at the median of the required Reynolds number range; the first nitrogen pressure is selected from the required nitrogen pressure range;

[0032] Step 02: The heating process of the magnetic shell workpiece in step 3 is divided into multiple temperature segments, and the corresponding median of the standard heating power range of the heating element in each temperature segment, the median of the required nitrogen pressure range, and the reference temperature non-uniformity and reference equivalent temperature matrix of all workpiece placement areas at the theoretical speed of the fan corresponding to the median of the required nitrogen pressure range are obtained;

[0033] Step 03: Select at least one test temperature section, control the heating element to the median of the standard heating power range of the test temperature section, the median of the required nitrogen pressure range, and the theoretical speed of the fan corresponding to the median of the required nitrogen pressure range, perform a preheating test on the vacuum gas quenching furnace, and obtain the actual temperature non-uniformity and actual equivalent temperature matrix of all workpiece placement areas through detection;

[0034] Step 04: Calculate the temperature non-uniformity coefficient H and the equivalent temperature difference value G of the heating process of step 3 of the current magnetic shell workpiece based on steps 02 and 03;

[0035] Step 05: Calculate the comprehensive evaluation value of each first nitrogen pressure based on the mapping table obtained in step 01 and step 04;

[0036] Step 06: Select the first nitrogen pressure whose comprehensive evaluation value is equal to 3, and the average value of the smallest L first nitrogen pressures as the target nitrogen pressure.

[0037] Preferably, based on the mapping table obtained in step 01, step 04 calculates the temperature unevenness evaluation value, heat exchange efficiency evaluation value, and fan speed evaluation value of each first nitrogen pressure, and obtains a comprehensive evaluation value of each first nitrogen pressure based on the temperature unevenness evaluation value, heat exchange efficiency evaluation value, and fan speed evaluation value of each first nitrogen pressure.

[0038] Preferably, the spraying in step 13 is performed by a spraying device, which includes a nozzle, a pipe, and a water pump. The nozzle is connected to the water outlet of the water pump through a pipe, the water inlet of the water pump is connected to a water source, and a regulating valve is installed in the pipe near the nozzle.

[0039] A pressure sensor and a flow sensor are installed at the outlet of the regulating valve to determine the target opening of the regulating valve of the current batch of magnetic shells before spraying the current batch of magnetic shells;

[0040] When spraying the current batch of magnetic shells of the current type, the water pump is controlled to work so that the water pressure at the water pump outlet is the maximum value of the benchmark spraying pressure range of each spraying period, and the actual opening of the control valve is controlled to be the target opening of the control valve of the current batch of magnetic shells of the current type.

[0041] Preferably, the process of determining the target opening of the regulating valve in the current batch and the current type of magnetic shell spraying process includes:

[0042] Step 131: Obtaining a reference spray parameter range for each spray period of the current magnetic shell; the spray process of the magnetic shell is divided into several spray periods, and the reference spray parameter range includes: a reference spray pressure range, a reference spray flow range, and a reference regulating valve opening;

[0043] Step 132: Obtain a fitting curve of regulating valve opening versus regulating valve outlet reference water pressure and a fitting curve of regulating valve opening versus regulating valve outlet reference flow rate when the water pump is in a reference operating state and the water pressure at the water pump outlet is the maximum value of the reference spraying pressure range for each spraying period; and select a plurality of first regulating valve openings that meet the reference spraying parameter range for each spraying period;

[0044] Step 134: Based on the first regulating valve opening in each spraying period and historical data of the spraying device, determine a corrected first regulating valve opening for each spraying period, determine a corrected first regulating valve opening that meets a plurality of first regulating valve openings as a second regulating valve opening, and determine the first regulating valve opening corresponding to the second regulating valve opening as a target first regulating valve opening;

[0045] Step 133: Controlling the water pump to operate for a first duration with the water pressure at the water pump outlet being the maximum value of the reference spray pressure range for each spray period and the regulating valve opening being the corresponding median value of the target first regulating valve opening, and controlling the pressure sensor and the flow sensor to conduct multiple tests within the first duration to determine the flow state value and the pressure state value;

[0046] Step 134: determining the median value of the target first regulating valve opening in each spraying period, in which the flow state value and the pressure state value are both within the corresponding preset range, as the target regulating valve opening for the corresponding spraying period;

[0047] Step 135 : Based on the median of the target first regulating valve opening corresponding to the spraying period for which the target regulating valve opening cannot be determined in step 134 and step 133 , determine the target regulating valve opening for the spraying period for which the target regulating valve opening cannot be determined in step 134 .

[0048] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The workpiece is annealed under vacuum conditions. Compared to conventional protective atmosphere annealing processes, this method eliminates the use of cracking gases such as methanol as a protective atmosphere, conserving raw materials while reducing carbon emissions. Nitrogen is introduced during the heating process to reduce workpiece adhesion. Furthermore, this magnetic shell annealing process effectively increases the size of recrystallized grains in the workpiece, reduces coercivity, and evens out the workpiece structure. It also prevents oxidation and maintains the workpiece's metallic color. Compared to existing technologies, the annealing method provided by this invention results in lower workpiece coercivity, less adhesion, and a better appearance. It also reduces carbon emissions and conserves raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0052] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0053] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0054] In addition, in the present invention, descriptions such as "first" and "second" are only used for descriptive purposes, and do not specifically refer to the order or sequence, nor are they used to limit the present invention. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions and technical features between the various embodiments can be combined with each other, but this must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0055] The present invention provides the following embodiments:

[0056] The present invention provides a low-carbon, green vacuum annealing process for low-coercivity magnetic shells in automotive electronically controlled motors. This process conserves raw materials while reducing carbon emissions. It also reduces the coercivity of the workpiece, evens out the workpiece structure, reduces adhesion, and ensures a high-quality appearance. Furthermore, the cleaning device in this embodiment requires no wastewater disposal.

[0057] It should be noted that the vacuum annealing process for low-carbon, green, low-coercivity magnetic shells for automotive electronic control motors provided in the embodiments of the present invention is primarily applicable to magnetic shells for automotive electronic control motor systems. These shells are typically made of DC04 material and exhibit a uniform microstructure and low coercivity after annealing. While this description uses the magnetic shells of automotive motor systems as an example, other preferred embodiments of the present invention can also be used for heat treatment of other workpieces, which are not specifically listed here.

[0058] Example 1, the embodiment of the present invention provides a low carbon, green automotive electronic control motor low coercivity magnetic shell vacuum annealing process, involving the vacuum annealing of metal materials, such as Figure 1 As shown, the following steps are included in sequence:

[0059] Step 1: Vacuum clean the magnetic shell workpiece;

[0060] Step 2: Place the magnetic shell workpiece into a vacuum gas quenching furnace and pre-evacuate the vacuum gas quenching furnace;

[0061] Step 3: A protective gas is introduced into the vacuum gas quenching furnace, and convection heating is used for the first heating and heat preservation;

[0062] Step 4: Use convection heating to raise the temperature for the second time. After reaching the temperature, stop introducing the protective gas and evacuate to keep warm.

[0063] Step 5: Slowly cool the magnetic shell workpiece by controlling the cooling speed;

[0064] Step 6: Turn on the forced cooling system for gas quenching;

[0065] Step 7: Remove the magnetic shell workpiece.

[0066] The step 1 comprises:

[0067] Step 11: Send the magnetic shell workpiece into the vacuum cleaning machine; use HWBV (vacuum degreasing cleaning machine);

[0068] Step 12: Ultrasonic immersion of the magnetic shell workpiece for 400-600 seconds;

[0069] Step 13: Spray the magnetic shell workpiece for 440s~640s;

[0070] Step 14: Dry the magnetic shell workpiece for 800s~1200s.

[0071] Alternatively, a vacuum degreasing machine can be used, with ultrasonic immersion for 400 seconds, spraying for 440 seconds, and rapid drying for 800 seconds. Using HWBV vacuum cleaning technology, the surface is clean and oil-free after cleaning, ensuring a good appearance. Furthermore, no aqueous solution is used for cleaning, achieving zero wastewater discharge.

[0072] The step 2 includes:

[0073] Step 21: Send the vacuum-cleaned magnetic shell workpiece into a vacuum gas quenching furnace;

[0074] Step 22: Pre-evacuate the vacuum gas quenching furnace to a vacuum degree of ≤1.0×10 -2 It should be noted that the vacuum condition mentioned in this embodiment refers to the use of a vacuum device to extract the gas in the furnace and make the vacuum degree in the furnace reach a certain requirement, the vacuum degree is 1.0×10 -2 Pa, there is less gas in the furnace, and it can be approximately considered that it has reached the vacuum condition.

[0075] Step 3 includes:

[0076] Step 31: After reaching the vacuum condition, nitrogen gas with a purity of ≥99.99% is introduced into the vacuum gas quenching furnace to a pressure of 100-200 kPa;

[0077] Step 32: Raise the furnace temperature to 790-810°C at a rate of 10-20°C / min and maintain this temperature for 25-35 minutes. Specifically, after achieving vacuum conditions, nitrogen can be introduced into the furnace to a pressure of 200 kPa. The furnace temperature is then raised to 800°C at a rate of 15°C / min and maintained for 30 minutes. It should be noted that heating the vacuum furnace here takes less than 55 minutes, and the nitrogen introduced must be pure nitrogen with a purity of at least 99.99%.

[0078] Step 4 includes:

[0079] Step 41: Continue to introduce nitrogen gas with a purity of ≥99.99% into the vacuum gas quenching furnace until the pressure reaches 100-200 kPa;

[0080] Step 42: After raising the furnace temperature to 830-850°C at a rate of 1-2°C / min, stop introducing nitrogen, continue evacuating, and maintain the temperature for 170-190 minutes. Fill the furnace with nitrogen to a pressure of 200 kPa. Raise the furnace temperature to 840°C at a rate of 1°C / min, then stop introducing nitrogen, continue evacuating, and maintain the temperature for 180 minutes. It should be noted that heating the vacuum furnace here takes 40 minutes, and the nitrogen introduced must be pure nitrogen with a purity of at least 99.99%.

[0081] In step 5, cool the workpiece to a furnace temperature of 490-510°C at a cooling rate of 1-2°C / min. After the second heating and holding period, the workpiece can be cooled to 500°C by setting the vacuum furnace cooling time to 170 minutes and controlling the cooling rate to 2°C / min. It should be noted that the workpiece cooling here is controlled cooling, strictly controlling the temperature drop rate to ensure uniform workpiece structure. The workpiece cooling time is 170 minutes.

[0082] Step 6 includes: introducing nitrogen with a purity of ≥99.99% and maintaining the pressure of the vacuum gas quenching furnace at 150~250kPa for gas quenching; wherein, after the furnace temperature drops to 500°C, nitrogen can be introduced into the vacuum gas quenching furnace and the pressure of the vacuum gas quenching furnace can be maintained at 200kPa for gas quenching; it should be noted that the nitrogen filled here is pure nitrogen with a purity of 99.99% or more.

[0083] In step 7, the magnetic shell workpiece is taken out after the furnace temperature is ≤50°C, wherein the workpiece can be taken out when the furnace temperature is 20°C.

[0084] The present invention provides a low-carbon, green, low-coercivity magnetic shell vacuum annealing process for automotive electronic control motors, which can reduce carbon emissions, effectively increase the size of recrystallized grains, reduce the coercivity of workpieces, uniformize the magnetic shell structure, reduce workpiece adhesion, prevent metal oxidation, and ensure that the workpiece has the original metallic color.

[0085] The vacuum annealing process provided in this embodiment adopts a vacuum recrystallization annealing process. The vacuum recrystallization annealing process cycle is about 600 minutes. The surface hardness is (95-100) HV1, the coercivity is (66-73) A / m, the microstructure is uniformly distributed, and the workpiece after annealing has no adhesion, good appearance, and the original metal color. The annealing process does not consume methanol and natural gas.

[0086] In summary, the annealing process method provided in this embodiment is used to anneal the magnetic shell of the automotive electronic control motor. During annealing, a vacuum recrystallization annealing process is adopted. The workpiece is annealed under vacuum conditions, and there is no need to use cracking gases such as methanol as a protective atmosphere, and there is no need to consume natural gas, thereby saving raw materials and reducing carbon emissions. Nitrogen is introduced during the heating process to reduce the adhesion of the workpiece. In addition, the vacuum recrystallization annealing process can effectively uniform the structure of the workpiece, increase the size of the recrystallized grains of the workpiece grains, and thus effectively reduce the coercive force of the workpiece.

[0087] The beneficial effects of the above technical solution are:

[0088] The workpiece is annealed under vacuum conditions. Compared to conventional protective atmosphere annealing processes, this method eliminates the use of cracking gases such as methanol as a protective atmosphere, conserving raw materials while reducing carbon emissions. Nitrogen is introduced during the heating process to reduce workpiece adhesion. Furthermore, this magnetic shell annealing process effectively increases the size of recrystallized grains in the workpiece, reduces coercivity, and evens out the workpiece structure. It also prevents oxidation and maintains the workpiece's metallic color. Compared to existing technologies, the annealing method provided by this invention results in lower workpiece coercivity, less adhesion, and a better appearance. It also reduces carbon emissions and conserves raw materials.

[0089] Example 2, based on Example 1, before the current batch of magnetic shell workpieces is placed in a vacuum gas quenching furnace for annealing, a target annealing parameter determination process is first performed. The target annealing parameter determination process includes:

[0090] Step 01: Obtain the required nitrogen pressure range and required Reynolds number range for the heating process of step 3 of the current magnetic shell workpiece, obtain a mapping table of the first nitrogen pressure-heat exchange efficiency-temperature non-uniformity of all workpiece placement areas, and obtain a mapping table of the first nitrogen pressure-theoretical speed of the fan that maintains the nitrogen Reynolds number in the vacuum gas quenching furnace at the median of the required Reynolds number range; the first nitrogen pressure is selected from the required nitrogen pressure range;

[0091] Step 02: The heating process of the magnetic shell workpiece in step 3 is divided into multiple temperature segments, and the corresponding median of the standard heating power range of the heating element in each temperature segment, the median of the required nitrogen pressure range, and the reference temperature non-uniformity and reference equivalent temperature matrix of all workpiece placement areas at the theoretical speed of the fan corresponding to the median of the required nitrogen pressure range are obtained;

[0092] Step 03: Select at least one test temperature section, control the heating element to the median of the standard heating power range of the test temperature section, the median of the required nitrogen pressure range, and the theoretical speed of the fan corresponding to the median of the required nitrogen pressure range, perform a preheating test on the vacuum gas quenching furnace, and obtain the actual temperature non-uniformity and actual equivalent temperature matrix of all workpiece placement areas through detection;

[0093] Step 04: Calculate the temperature non-uniformity coefficient H and the equivalent temperature difference value G of the heating process of step 3 of the current magnetic shell workpiece based on steps 02 and 03;

[0094] Step 05: Calculate the comprehensive evaluation value of each first nitrogen pressure based on the mapping table obtained in step 01 and step 04;

[0095] Step 06: Select a comprehensive evaluation value of the first nitrogen pressure equal to 3, and the average value of the smallest L (value ranges from 1 to 5) first nitrogen pressures is the target nitrogen pressure (the theoretical speeds of the fan corresponding to the smallest L (value ranges from 1 to 5) first nitrogen pressures can be averaged to obtain the target fan speed, and the above-mentioned target annealing parameters include the target fan speed).

[0096] Among them, based on the mapping table obtained in step 01, step 04 calculates the temperature non-uniformity evaluation value, heat exchange efficiency evaluation value, and fan speed evaluation value of each first nitrogen pressure, and based on the temperature non-uniformity evaluation value, heat exchange efficiency evaluation value, and fan speed evaluation value of each first nitrogen pressure, a comprehensive evaluation value of each first nitrogen pressure is obtained.

[0097] Required nitrogen pressure range: Based on the quenching process requirements of the workpiece material, consult the process manual or conduct simulation calculations and tests to determine the range that the nitrogen pressure needs to cover;

[0098] Temperature non-uniformity requirements: Determine the allowable temperature deviation range based on industry standards or customer quality requirements;

[0099] Required Reynolds number range: The Reynolds number is calculated based on fluid mechanics theory, and based on testing, the required Reynolds number range is determined to ensure that the heat transfer efficiency and uniformity meet the requirements;

[0100] A mapping table of first nitrogen pressure, heat exchange efficiency, and temperature nonuniformity across all workpiece placement areas is implemented based on the initial heating elements and fans used, using a combination of simulation and experimentation (experimental and simulation data can be compared to take a weighted average). The first nitrogen pressure is selected within the required nitrogen pressure range according to preset selection rules.

[0101] The parameters obtained in step 01 can be determined and stored before batch heat treatment.

[0102] A mapping table between the first nitrogen pressure and the theoretical speed of the fan for maintaining the nitrogen Reynolds number in the vacuum gas quenching furnace within the midpoint of the required Reynolds number range is implemented by combining simulation and experiment based on the initially used heating elements and fans (the experimental data and the simulation data can be compared and a weighted average taken);

[0103] The heat generated by the heating elements connected to the vacuum gas quenching furnace is first transferred to the nitrogen, and then the fan is used to make the nitrogen convect and bring the heat to the surface of the workpiece to achieve heating of the workpiece.

[0104] in, ;

[0105] is the actual equivalent temperature of the i-th workpiece placement area in the current temperature segment; The average detection value of the jth temperature detection point in the i-th workpiece placement area during the preheating detection process of the current temperature segment (obtained during the preheating test);

[0106] The actual temperature non-uniformity of all workpiece placement areas in the current temperature segment is: the standard deviation of the actual equivalent temperatures of all workpiece placement areas ÷ the average value of the actual equivalent temperatures of all workpiece placement areas in the current temperature segment;

[0107] The first row of the actual equivalent temperature matrix is ​​the number of the workpiece placement area, and the second row is the actual equivalent temperature of the workpiece placement area corresponding to the first row (obtained during the preheating test).

[0108] ;

[0109] ;

[0110] M is the total number of test temperature segments selected in step 03 (several consecutive test temperature segments (M can be 2-5), where the test temperature segments are selected from the divided temperature segments); is the average value of the reference equivalent temperature of all placement areas at the end of the kth test temperature section; is the average value of the reference equivalent temperature of all placement areas at the beginning of the kth test temperature segment; for Corresponding benchmark values ​​(obtained through testing based on initially used qualified heating elements and fans); is the actual temperature non-uniformity of the kth test temperature section; is the reference temperature non-uniformity of the kth test temperature segment (obtained by testing based on the initially used qualified heating elements and fans); H is the temperature non-uniformity difference coefficient; G is the equivalent temperature difference value;

[0111] ;

[0112] is the temperature non-uniformity of the workpiece placement area corresponding to the rth first nitrogen pressure in the first nitrogen pressure-heat exchange efficiency-temperature non-uniformity of all workpiece placement areas mapping table; is the heat exchange efficiency corresponding to the rth first nitrogen pressure in the mapping table of first nitrogen pressure-heat exchange efficiency-temperature non-uniformity of all workpiece placement areas; is the temperature non-uniformity evaluation value corresponding to the rth first nitrogen pressure, in the middle Less than or equal to 1, then The value is 1, otherwise The value is 0; is the minimum allowable heat transfer efficiency of nitrogen in a vacuum gas quenching furnace; is the heat exchange efficiency evaluation value corresponding to the rth first nitrogen pressure. Greater than or equal to 1, then The value is 1, otherwise The value is 0; is the fan speed evaluation value corresponding to the rth first nitrogen pressure; The first nitrogen pressure is the theoretical speed of the fan corresponding to the rth first nitrogen pressure in the mapping table of the theoretical speed of the fan maintaining the nitrogen Reynolds number in the vacuum gas quenching furnace at the middle value of the required Reynolds number range; n is the maximum allowable speed of the fan. If greater than 1, then The value is 1, otherwise, The value is 0; is the comprehensive evaluation value of the rth first nitrogen pressure;

[0113] The beneficial effects of the above technical solution are:

[0114] During the heating process of the magnetic shell workpiece in step 3, maintaining the required heating rate requires adjusting the power of the heating element to ensure the required heating rate at different workpiece temperatures. Therefore, the temperature segments are divided according to the power requirements of the heating element. Precise control of each temperature segment is achieved by establishing baseline parameters for each temperature segment and comparing them with the actual test parameters. The temperature non-uniformity coefficient H and the equivalent temperature difference G are calculated to quantify the temperature deviation. This reduces the temperature non-uniformity within the furnace compared to traditional processes, significantly improving the hardness and metallographic consistency of the workpiece after heat treatment, significantly improving quality, and effectively reducing the scrap rate of parts.

[0115] Leveraging a system that maps primary nitrogen pressure, heat exchange efficiency, and temperature nonuniformity across all workpiece placement areas, as well as primary nitrogen pressure and the theoretical fan speed required to maintain the nitrogen Reynolds number within the required range within the vacuum gas quenching furnace, a system with pre-stored process parameter mappings for multiple materials enables rapid switching between heat treatment processes for different materials. This allows for rapid parameter adaptation when switching workpieces, eliminating the need for traditional manual trial and error.

[0116] Through preheating tests, the relationship between heating power, fan speed and temperature field is calibrated in advance to avoid ineffective energy consumption caused by heating the entire furnace. Comprehensive evaluation is used to screen out the appropriate nitrogen pressure, effectively improving the high energy consumption and long cycle of traditional quenching.

[0117] Example 3, based on Example 1 or 2,

[0118] The spraying in step 13 is based on spraying by a spraying device, which includes a nozzle, a pipe, and a water pump. The nozzle is connected to the water outlet of the water pump through a pipe, the water inlet of the water pump is connected to a water source, and a regulating valve is installed in the pipe near the nozzle;

[0119] A pressure sensor and a flow sensor are installed at the outlet of the regulating valve to determine the target opening of the regulating valve of the current batch of magnetic shells before spraying the current batch of magnetic shells;

[0120] When spraying the current batch of magnetic shells of the current type, the water pump is controlled to work so that the water pressure at the water pump outlet is the maximum value of the benchmark spraying pressure range of each spraying period, and the actual opening of the control valve is controlled to be the target opening of the control valve of the current batch of magnetic shells of the current type.

[0121] The process of determining the target opening of the regulating valve for the current batch of magnetic shell spraying processes includes:

[0122] Step 131: Obtaining a reference spray parameter range for each spray period of the current magnetic shell; the spray process of the magnetic shell is divided into several spray periods, and the reference spray parameter range includes: a reference spray pressure range, a reference spray flow range, and a reference regulating valve opening;

[0123] Step 132: Obtain a fitting curve of regulating valve opening versus regulating valve outlet reference water pressure and a fitting curve of regulating valve opening versus regulating valve outlet reference flow rate when the water pump is in a reference operating state (an initially used and qualified water pump) and the water pressure at the water pump outlet is the maximum value of the reference spraying pressure range for each spraying period; and select a plurality of first regulating valve openings that meet the reference spraying parameter range for each spraying period;

[0124] Step 134: Based on the first regulating valve opening in each spraying period and historical data of the spraying device, determine a corrected first regulating valve opening for each spraying period, determine a corrected first regulating valve opening that meets a plurality of first regulating valve openings as a second regulating valve opening, and determine the first regulating valve opening corresponding to the second regulating valve opening as a target first regulating valve opening;

[0125] Step 133: Controlling the water pump to operate for a first duration with the water pressure at the water pump outlet being the maximum value of the reference spray pressure range for each spray period and the regulating valve opening being the corresponding median value of the target first regulating valve opening, and controlling the pressure sensor and the flow sensor to conduct multiple tests within the first duration to determine the flow state value and the pressure state value;

[0126] Step 134: determining the median value of the target first regulating valve opening in each spraying period, in which the flow state value and the pressure state value are both within the corresponding preset range, as the target regulating valve opening for the corresponding spraying period;

[0127] Step 135 : Based on the median of the target first regulating valve opening corresponding to the spraying period for which the target regulating valve opening cannot be determined in step 134 and step 133 , determine the target regulating valve opening for the spraying period for which the target regulating valve opening cannot be determined in step 134 .

[0128] The reference spray parameter range of each spray period of the current magnetic shell; the spray process of the magnetic shell is divided into several spray periods, such as:

[0129] The first spraying period (pre-spraying): 1-2 minutes, quickly wash away the dust and liquid on the surface of the workpiece after ultrasonic immersion, preliminary cleaning, and lay the foundation for deep spraying; spraying pressure 0.1-0.2MPa, flow rate 15-20L / min

[0130] The second spraying period (main spraying): 3-6 minutes; spraying pressure 0.8-1.2MPa, flow rate 20-30L / min;

[0131] The third spraying period (fine spraying): 2-3 minutes; spraying pressure 0.1-0.2MPa, flow rate 10-15L / min;

[0132] The benchmark spray parameters and benchmark spray flow range can be determined based on theoretical foundation (theoretical values ​​determined based on fluid mechanics and historical experience) and experimental calibration:

[0133] In this embodiment, a plurality of first regulating valve openings that meet the reference spray parameter range in each spraying period are screened, wherein the plurality of first regulating valve openings may be continuous first regulating valve opening segments (from which a plurality of first regulating valve openings may be selected for the following calculation) or individual first regulating valve openings;

[0134] ;

[0135] in, is the corrected opening of the mth first regulating valve; is the opening of the mth first regulating valve; S is the total number of historical spraying periods contained in the latest historical data of the spraying device obtained in step 134; The target opening degree of the regulating valve in the yth historical spraying period in the latest historical data of the spraying device obtained in step 134; for The corresponding reference opening of the regulating valve;

[0136] ;

[0137] ;

[0138] is the pressure state value corresponding to the first duration of the current spraying period in step 133; is the average detection value of the pressure sensor during the first duration of the current spraying period in step 133; The reference water pressure corresponding to the median of the target first regulating valve opening in the current spraying period in the fitting curve of the regulating valve opening and the regulating valve outlet reference water pressure in the current spraying period obtained in step 132;

[0139] is the flow state value corresponding to the first duration of the current spraying period in step 133; is the average detection value of the flow sensor during the first duration of the current spraying period in step 133; The reference water flow rate corresponding to the median of the target first regulating valve opening in the current spraying period in the fitting curve of the regulating valve opening and the regulating valve outlet reference flow rate obtained in step 132;

[0140] Step 135: Based on the median value of the target first regulating valve opening corresponding to the spraying period for which the target regulating valve opening cannot be determined in step 134 and step 133, the target regulating valve opening for the spraying period for which the target regulating valve opening cannot be determined in step 134 is determined, specifically:

[0141] First condition: , ;

[0142] The first value of the current spraying period in which the target regulating valve opening cannot be determined by step 134, in the regulating valve opening-regulating valve outlet reference water pressure fitting curve, is: a regulating valve outlet reference water pressure corresponding to a target first regulating valve opening greater than a median value of the corresponding target first regulating valve opening;

[0143] The first value of the current spray period during which the target regulating valve opening cannot be determined by step 134 is the first value of the current spray period during which the target regulating valve opening cannot be determined by step 134. a reference flow rate at a regulating valve outlet corresponding to a target first regulating valve opening greater than a median value of the corresponding target first regulating valve opening;

[0144] is the median value of the reference spray pressure range during the current spray period during which the target regulating valve opening cannot be determined in step 134; is the median value of the reference spray pressure and flow rate during the current spray period during which the target regulating valve opening cannot be determined in step 134;

[0145] The minimum target first regulating valve opening that satisfies the first condition during the current spraying period for which the target regulating valve opening cannot be determined by step 134 is determined as the target regulating valve opening during the current spraying period for which the target regulating valve opening cannot be determined by step 134 .

[0146] The "fuzzy parameters" of traditional spraying magnetic shell cleaning rely on the "master's experience", and large pressure fluctuations and flow deviations lead to: uneven cleaning (excessive local residues); magnetic performance fluctuations (excessive pressure damages the magnetic circuit).

[0147] The beneficial effects of the above scheme are:

[0148] The magnetic shell spraying is divided into "pre-spraying, main spraying, and fine spraying" periods, and the upper / lower pressure limit, flow range, and opening range of each spraying period are determined by "theory + experiment" to ensure the cleaning effect of the current magnetic shell.

[0149] By using the "regulating valve opening-regulating valve outlet benchmark water pressure fitting curve and regulating valve opening-regulating valve outlet benchmark flow fitting curve when the water pump is in the benchmark working state and the water pressure at the water pump outlet is the maximum value of the benchmark spraying pressure range for each spraying period" instead of "adjusting the opening based on feeling", the equipment characteristics can be accurately matched and the control accuracy of the regulating valve opening can be improved.

[0150] Based on the "historical data of the sprinkler device", the opening of the regulating valve is corrected to ensure the sprinkler effect.

[0151] Small batch tests are conducted using the "maximum reference pressure + median opening value" to collect the "stable value / state value" of pressure and flow. This allows for early detection of "theoretical parameters ≠ actual results." If the target control valve opening cannot be calculated in step 134, the state value is used to redetermine the target control valve opening.

[0152] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors, characterized by: The following steps are included in sequence: Step 1: Vacuum clean the magnetic shell workpiece; Step 2: Place the magnetic shell workpiece into a vacuum gas quenching furnace and pre-evacuate the vacuum gas quenching furnace; Step 3: A protective gas is introduced into the vacuum gas quenching furnace, and convection heating is used for the first heating and heat preservation; Step 4: Use convection heating to raise the temperature for the second time. After reaching the temperature, stop introducing the protective gas and evacuate to keep warm. Step 5: Slowly cool the magnetic shell workpiece by controlling the cooling speed; Step 6: Turn on the forced cooling system for gas quenching; Step 7: Remove the magnetic shell workpiece.

2. The vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors according to claim 1, characterized in that: The step 1 comprises: Step 11: Send the magnetic shell workpiece into the vacuum cleaning machine; Step 12: Ultrasonic immersion of the magnetic shell workpiece for 400-600 seconds; Step 13: Spray the magnetic shell workpiece for 440s~640s; Step 14: Dry the magnetic shell workpiece for 800s~1200s.

3. The vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors according to claim 1, characterized in that: The step 2 includes: Step 21: Send the vacuum-cleaned magnetic shell workpiece into a vacuum gas quenching furnace; Step 22: Pre-evacuate the vacuum gas quenching furnace to a vacuum degree of ≤1.0×10 -2 Pa.

4. The vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors according to claim 1, characterized in that: Step 3 includes: Step 31: introducing nitrogen gas with a purity of ≥99.99% into the vacuum gas quenching furnace to a pressure of 100-200 kPa; Step 32: Raise the furnace temperature to 790-810°C at a heating rate of 10-20°C / min and keep it at that temperature for 25-35 minutes.

5. The vacuum annealing process for low coercivity magnetic shell of low-carbon, green automotive electronic control motor according to claim 1, characterized in that: Step 4 includes: Step 41: Continue to introduce nitrogen gas with a purity of ≥99.99% into the vacuum gas quenching furnace until the pressure reaches 100-200 kPa; Step 42: After raising the furnace temperature to 830-850°C at a heating rate of 1-2°C / min, stop introducing nitrogen, continue vacuuming, and keep the temperature for 170-190 minutes.

6. The vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors according to claim 1, characterized in that: Step 5: Cooling at a cooling rate of 1-2°C / min to a furnace temperature of 490-510°C; Step 6 includes: introducing nitrogen with a purity of ≥99.99% and maintaining the pressure of the vacuum gas quenching furnace at 150-250 kPa for gas quenching; In step 7, the magnetic shell workpiece is taken out after the furnace temperature is ≤50°C.

7. The vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors according to claim 1, characterized in that: Before the current batch of magnetic shell workpieces is placed in a vacuum gas quenching furnace for annealing, a target annealing parameter determination process is first performed. The target annealing parameter determination process includes: Step 01: Obtain the required nitrogen pressure range and required Reynolds number range for the heating process of step 3 of the current magnetic shell workpiece, obtain a mapping table of the first nitrogen pressure-heat exchange efficiency-temperature non-uniformity of all workpiece placement areas, and obtain a mapping table of the first nitrogen pressure-theoretical speed of the fan that maintains the nitrogen Reynolds number in the vacuum gas quenching furnace at the median of the required Reynolds number range; the first nitrogen pressure is selected from the required nitrogen pressure range; Step 02: The heating process of the magnetic shell workpiece in step 3 is divided into multiple temperature segments, and the corresponding median of the standard heating power range of the heating element in each temperature segment, the median of the required nitrogen pressure range, and the reference temperature non-uniformity and reference equivalent temperature matrix of all workpiece placement areas at the theoretical speed of the fan corresponding to the median of the required nitrogen pressure range are obtained; Step 03: Select at least one test temperature section, control the heating element to the median of the standard heating power range of the test temperature section, the median of the required nitrogen pressure range, and the theoretical speed of the fan corresponding to the median of the required nitrogen pressure range, perform a preheating test on the vacuum gas quenching furnace, and obtain the actual temperature non-uniformity and actual equivalent temperature matrix of all workpiece placement areas through detection; Step 04: Calculate the temperature non-uniformity coefficient H and the equivalent temperature difference value G of the heating process of step 3 of the current magnetic shell workpiece based on steps 02 and 03; Step 05: Calculate the comprehensive evaluation value of each first nitrogen pressure based on the mapping table obtained in step 01 and step 04; Step 06: Select the first nitrogen pressure whose comprehensive evaluation value is equal to 3, and the average value of the smallest L first nitrogen pressures as the target nitrogen pressure.

8. The vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors according to claim 7, characterized in that: Based on the mapping table obtained in step 01, step 04 calculates the temperature non-uniformity evaluation value, heat exchange efficiency evaluation value, and fan speed evaluation value of each first nitrogen pressure, and obtains a comprehensive evaluation value of each first nitrogen pressure based on the temperature non-uniformity evaluation value, heat exchange efficiency evaluation value, and fan speed evaluation value of each first nitrogen pressure.

9. The vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors according to claim 2, characterized in that: The spraying in step 13 is based on spraying by a spraying device, which includes a nozzle, a pipe, and a water pump. The nozzle is connected to the water outlet of the water pump through a pipe, the water inlet of the water pump is connected to a water source, and a regulating valve is installed in the pipe near the nozzle; A pressure sensor and a flow sensor are installed at the outlet of the regulating valve to determine the target opening of the regulating valve for the current batch of magnetic shells before spraying the current batch of magnetic shells; When spraying the current batch of magnetic shells of the current type, the water pump is controlled to work so that the water pressure at the water pump outlet is the maximum value of the benchmark spraying pressure range of each spraying period, and the actual opening of the control valve is controlled to be the target opening of the control valve of the current batch of magnetic shells of the current type.

10. The vacuum annealing process for low-coercivity magnetic shells of low-carbon, green automotive electronic control motors according to claim 9, characterized in that: The process of determining the target opening of the regulating valve for the current batch of magnetic shell spraying processes includes: Step 131: Obtaining a reference spray parameter range for each spray period of the current magnetic shell; the spray process of the magnetic shell is divided into several spray periods, and the reference spray parameter range includes: a reference spray pressure range, a reference spray flow range, and a reference regulating valve opening; Step 132: Obtain a fitting curve of regulating valve opening versus regulating valve outlet reference water pressure and a fitting curve of regulating valve opening versus regulating valve outlet reference flow rate when the water pump is in a reference operating state and the water pressure at the water pump outlet is the maximum value of the reference spraying pressure range for each spraying period; and select a plurality of first regulating valve openings that meet the reference spraying parameter range for each spraying period; Step 134: Based on the first regulating valve opening in each spraying period and historical data of the spraying device, determine a corrected first regulating valve opening for each spraying period, determine a corrected first regulating valve opening that meets a plurality of first regulating valve openings as a second regulating valve opening, and determine the first regulating valve opening corresponding to the second regulating valve opening as a target first regulating valve opening; Step 133: Controlling the water pump to operate for a first duration with the water pressure at the water pump outlet being the maximum value of the reference spray pressure range for each spray period and the regulating valve opening being the corresponding median value of the target first regulating valve opening, and controlling the pressure sensor and the flow sensor to conduct multiple tests within the first duration to determine the flow state value and the pressure state value; Step 134: determining the median value of the target first regulating valve opening in each spraying period, in which the flow state value and the pressure state value are both within the corresponding preset range, as the target regulating valve opening for the corresponding spraying period; Step 135 : Based on the median of the target first regulating valve opening corresponding to the spraying period for which the target regulating valve opening cannot be determined in step 134 and step 133 , determine the target regulating valve opening for the spraying period for which the target regulating valve opening cannot be determined in step 134 .

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