Annealing process of annealing furnace

Abstract

The invention discloses an annealing process of an annealing furnace, and relates to the technical field of annealing of annealing furnaces. Comprising the steps of 1, conductor charging preparation; 2, placing a conductor and sealing the inner cover; 3, the furnace is vacuumized and filled with nitrogen; step 4, mounting an outer cover and raising the temperature; 5, atmosphere purification and heat preservation are conducted at the high temperature; 6, forcibly circulating nitrogen to accelerate cooling; and 7, discharging after cooling. The fifth step comprises the following steps that when the temperature of the outer cover reaches 330 DEG C, a heating power source is turned off, a vacuum valve is turned on, pumping is conducted to 0.01 MPa at the speed of 3-5 kPa / min, pressure maintaining is conducted for 10 min, then nitrogen is charged to 0.14 MPa, and after pressure maintaining is conducted for 5 min, the heating power source is restarted. According to the method, by means of forced circulation nitrogen accelerated cooling and the like, through inert nitrogen protection and precise parameter control in the whole process, the surface of the conductor is free of oxidation, the size precision is high, the resistance value fluctuation is small, the cooling time is shortened to 2-3 hours from 4-6 hours, and the equipment turnover rate is obviously increased in cooperation with standardized operation of all the steps.

Description

Technical Field

[0001] This invention relates to the field of annealing furnace technology, specifically to an annealing furnace process. Background Technology

[0002] Conductor annealing is a process for cold-worked metal conductors. By heating, holding at a specific temperature and controlling the cooling process, the recrystallization principle of metals is utilized to eliminate lattice distortion and internal stress caused by work hardening, thereby restoring the conductor's excellent conductivity, plasticity and toughness.

[0003] The original annealing process has a cooling time of 4-6 hours, which is long and the nitrogen protection at high temperature is easily weakened, resulting in slight oxidation of the conductor surface and dimensional deviation caused by local temperature difference. In order to address this issue, this invention proposes a novel annealing furnace process. Summary of the Invention

[0004] The purpose of this invention is to provide an annealing furnace process to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an annealing furnace process, comprising the following steps: Step 1: Conductor loading preparation; Step 2: Place the conductor and seal the inner cover; Step 3: Evacuate the furnace and fill it with nitrogen; Step 4: Install the outer cover and heat up; Step 5: Atmosphere purification and heat preservation at high temperatures; Step Six: Forced circulation of nitrogen to accelerate cooling; Step 7: Remove from oven after cooling; Step five includes the following steps: When the outer casing temperature reaches 330℃, turn off the heating power, open the vacuum valve, pump to 0.01MPa at a rate of 3-5kPa / min, maintain the pressure for 10 minutes, then purge with nitrogen to 0.14MPa, maintain the pressure for 5 minutes, then restart the heating power to maintain the outer casing temperature at 330℃, and then keep it at that temperature for 6-10 hours. Step six includes the following steps: After the heat preservation is completed, turn off the heating power of the outer cover, remove the outer cover, and introduce clean nitrogen into the furnace. Use a fan to force the nitrogen to circulate between the inner cover and the conductor, with the flow rate controlled at 20-25 m³ / h. The circulating gas is cooled by the cooler before entering the inner cover, continuously removing heat. Then, record the temperature inside the inner cover every 15 minutes. When the temperature drops to 100℃, reduce the nitrogen flow rate to 10-15 m³ / h until the temperature drops below 40℃.

[0006] Furthermore, the vacuuming process inside the furnace in step three includes the following steps: S1: Evacuate the furnace to -0.03MPa at a rate of 5-8kPa / min, maintain the pressure for 5 minutes, and observe the vacuum gauge reading. If the pressure drop is ≤0.002MPa, it is qualified. If it exceeds the standard, check for leaks. S2: Continue pumping at a rate of 3-5 kPa / min until -0.06 MPa is reached, maintain the pressure for 5 minutes, and then check the seal again; S3: Slowly pump to 0.01MPa, close the vacuum valve, maintain the pressure for 10 minutes, and ensure that the pressure fluctuation is ≤0.001MPa.

[0007] Furthermore, the nitrogen purging process in step three includes the following steps: s1: Open the nitrogen cylinder valve and adjust the output pressure to 0.2-0.25MPa using the pressure reducing valve; s2: Open the inlet valve and charge nitrogen into the furnace at a flow rate of 8-12 m³ / h. When the pressure rises to 0.05 MPa, close the valve and maintain the pressure for 5 minutes. Then continue charging to 0.14 MPa and close the inlet valve. S3: Ensure that the pressure drop inside the furnace is ≤0.003MPa within 30 minutes. If the pressure drop exceeds the limit, nitrogen must be released and the inner cover seal must be rechecked.

[0008] Furthermore, in step five, the heat preservation stage needs to be entered after nitrogen is introduced and maintained for 6-10 hours. The furnace temperature is recorded every 2 hours, and the temperature difference between the outer and inner covers is controlled to be ≤10℃ and the nitrogen pressure fluctuation is controlled to be ≤0.005MPa to ensure parameter stability.

[0009] Furthermore, step six, which involves forced circulation of nitrogen to accelerate cooling, includes the following steps: F1: Introduce clean nitrogen into the furnace and force the nitrogen to circulate between the inner cover and the conductor using a fan. The flow rate is 20-25 m³ / h. The circulating gas passes through a cooler with an inlet water temperature of ≤25℃. After cooling, the gas enters the inner cover to continuously remove heat. F2: Record the temperature inside the inner cover every 15 minutes. When the temperature drops to 100℃, reduce the nitrogen flow rate to 10-15m³ / h until the temperature drops below 40℃. F3: Once the temperature stabilizes below 40℃, shut off the nitrogen circulation system and maintain a nitrogen positive pressure ≥0.1MPa inside the inner shroud.

[0010] Furthermore, in step four, the heating rate needs to be controlled at 5-8℃ / min to avoid rapid heating causing thermal stress in the inner cover or conductor.

[0011] Furthermore, the concentration of nitrogen gas introduced in steps three, five, and six is ​​consistent, and the purity of nitrogen gas is ≥99.99% in each step.

[0012] Furthermore, in step seven, the exhaust valve should be opened slowly to reduce the nitrogen pressure inside the inner shroud to 0 MPa. The surface temperature of the conductor should be measured at multiple points using an infrared thermometer to ensure that it is ≤40℃, while the ambient temperature is recorded.

[0013] Compared with the prior art, the beneficial effects of the present invention are: This annealing furnace process uses forced circulation of nitrogen to accelerate cooling, and is protected by inert nitrogen and controlled by precise parameters throughout the process. The conductor surface is free of oxidation, has high dimensional accuracy, and has small resistance fluctuations. The cooling time is shortened from 4-6 hours to 2-3 hours. With the standardized operation of each step, the equipment turnover rate is significantly improved.

[0014] At the same time, shortening the cooling time reduces the auxiliary energy consumption during the heat preservation stage. In addition, due to the improved conductor performance, the consumption of raw materials is reduced, which can ensure the surface quality and performance stability of the conductor when it comes out of the furnace and reduce the quality risks of subsequent processing. Detailed Implementation

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] This invention provides a technical solution: an annealing furnace annealing process, comprising the following steps: Step 1: Conductor loading preparation. Pre-treatment of the conductor and shaft disk is carried out in advance, such as cleaning the surface and checking the condition of the shaft disk, to avoid impurities being brought into the furnace, so as to prevent the generation of volatile substances that pollute the atmosphere during heating. At the same time, by standardizing the winding tension and density, it is ensured that the conductor is heated evenly.

[0017] Step 2: Place the conductor and seal the inner cover. The conductor should be placed in the center and kept at a safe distance from the furnace wall to ensure uniform heat radiation during heating. Sealing the inner cover with screws is a prerequisite for maintaining an inert atmosphere inside the furnace and preventing external air from seeping in, thus avoiding high-temperature oxidation of the copper conductor.

[0018] Step 3: Evacuate the furnace and fill it with nitrogen; Step 4: Install the outer cover and heat up; Step 5: Atmosphere purification and heat preservation at high temperatures; Step Six: Forced circulation of nitrogen to accelerate cooling; Step 7: Remove from the oven after cooling.

[0019] Step five includes the following steps: When the outer casing temperature reaches 330℃, turn off the heating power, open the vacuum valve, and evacuate to 0.01MPa at a rate of 3-5kPa / min. Hold the pressure for 10 minutes, then purge with nitrogen to 0.14MPa and hold for 5 minutes. After that, restart the heating power and maintain the outer casing temperature at 330℃. Then keep it at that temperature for 6-10 hours. The second vacuuming at high temperature can remove trace amounts of volatile substances released by the conductor due to high temperature, such as residual oil, and prevent them from contaminating the protective atmosphere.

[0020] Step six includes the following steps: After the heat preservation is completed, turn off the heating power of the outer cover, remove the outer cover, and introduce clean nitrogen into the furnace. Use a fan to force the nitrogen to circulate between the inner cover and the conductor, with the flow rate controlled at 20-25 m³ / h. The circulating gas is cooled by the cooler before entering the inner cover, continuously removing heat. Then, record the temperature inside the inner cover every 15 minutes. When the temperature drops to 100℃, reduce the nitrogen flow rate to 10-15 m³ / h until the temperature drops below 40℃.

[0021] Furthermore, step three, which involves evacuating the furnace, includes the following steps: S1: Evacuate the furnace to -0.03MPa at a rate of 5-8kPa / min, maintain the pressure for 5 minutes, and observe the vacuum gauge reading. If the pressure drop is ≤0.002MPa, it is qualified. If it exceeds the standard, check for leaks.

[0022] S2: Continue pumping at a rate of 3-5 kPa / min until -0.06 MPa is reached, maintain the pressure for 5 minutes, and then check the seal again; S3: Slowly pump to 0.01MPa, close the vacuum valve, maintain the pressure for 10 minutes, and ensure that the pressure fluctuation is ≤0.001MPa.

[0023] Step-by-step vacuuming can gradually identify sealing defects. The first stage is pressure holding to test the initial seal, and the third stage confirms the high vacuum seal. This avoids directly pumping to the target pressure, which could cause the seal to deform due to the instantaneous pressure difference. At the same time, slowly reducing the pressure can reduce the residual air in the furnace.

[0024] Step three, purging the furnace with nitrogen, includes the following steps: s1: Open the nitrogen cylinder valve and adjust the output pressure to 0.2-0.25MPa using the pressure reducing valve; s2: Open the inlet valve and charge nitrogen into the furnace at a flow rate of 8-12 m³ / h. When the pressure rises to 0.05 MPa, close the valve and maintain the pressure for 5 minutes. Then continue charging to 0.14 MPa and close the inlet valve. S3: Ensure that the pressure drop inside the furnace is ≤0.003MPa within 30 minutes. If the pressure drop exceeds the limit, nitrogen must be released and the inner cover seal must be rechecked.

[0025] Controlling the purity and filling rate of nitrogen can prevent the inner cover seal from loosening due to airflow impact. Staged pressure holding tests can further verify the reliability of the seal, ensuring that compressed nitrogen effectively isolates air. By vacuuming and deoxygenating and then filling with nitrogen for protection, the risk of oxygen oxidation to copper conductors is completely eliminated, providing an inert environment for high-temperature annealing.

[0026] Furthermore, in step five, the heat preservation stage needs to begin after nitrogen is introduced and be maintained for 6-10 hours. The furnace temperature should be recorded every 2 hours, and the temperature difference between the outer and inner covers should be controlled to be ≤10℃ and the nitrogen pressure fluctuation to be ≤0.005MPa. This ensures stable parameters, allows for sufficient recrystallization of the internal structure of the copper conductor, eliminates cold working stress, restores conductivity, and ensures stable heat preservation. Monitoring parameters every 2 hours also ensures stable heat preservation. Atmosphere purification enhances the protective effect, and sufficient heat preservation time ensures that the conductor performance meets the standards.

[0027] Furthermore, step six, which involves forced nitrogen circulation to accelerate cooling, includes the following steps: F1: Introduce clean nitrogen into the furnace and force the nitrogen to circulate between the inner cover and the conductor using a fan. The flow rate is 20-25 m³ / h. The circulating gas passes through a cooler with an inlet water temperature of ≤25℃. After cooling, the gas enters the inner cover to continuously remove heat. F2: Record the temperature inside the inner cover every 15 minutes. When the temperature drops to 100℃, reduce the nitrogen flow rate to 10-15m³ / h until the temperature drops below 40℃. F3: Once the temperature stabilizes below 40℃, shut off the nitrogen circulation system and maintain a nitrogen positive pressure ≥0.1MPa inside the inner shroud.

[0028] By utilizing the fluidity of nitrogen to quickly remove heat, the efficiency of natural cooling is increased by 40%-60%, shortening the production cycle. Furthermore, by controlling the nitrogen flow rate in stages, condensation on the conductor surface due to excessive cooling at low temperatures can be avoided. This significantly shortens the cooling time and improves equipment utilization while ensuring conductor quality.

[0029] The annealing process using forced nitrogen circulation for accelerated cooling was compared with that of the original process in terms of cooling time, conductor surface condition, conductor resistance, conductor dimensional accuracy, conductor mechanical properties, and batch yield. The results are shown in the table below:

[0030] Compared with the original process, the conductor obtained by the newly added seventh step has a cooling time that is shortened by about 50%, no surface oxidation, a dimensional deviation that is reduced by about 50%, smaller fluctuations in resistance and mechanical properties, and a batch pass rate that is increased to over 99%, thus comprehensively optimizing quality, efficiency and cost.

[0031] Furthermore, in step four, the heating rate needs to be controlled at 5-8℃ / min to avoid rapid heating causing thermal stress in the inner cover or conductor. Copper has a high coefficient of thermal expansion, and rapid heating can easily lead to local stress concentration. Controlling the heating rate at 5-8℃ / min can prevent the inner cover and conductor from deforming due to excessive thermal stress.

[0032] Furthermore, the concentration of nitrogen introduced in steps three, five, and six is ​​consistent, and the purity of nitrogen is ≥99.99% in all steps.

[0033] Furthermore, in step seven, the exhaust valve should be opened slowly after the conductor is removed from the furnace to reduce the nitrogen pressure inside the inner shroud to 0 MPa. The surface temperature of the conductor should be checked at multiple points using an infrared thermometer to ensure that it is ≤40℃. At the same time, the ambient temperature should be recorded to prevent oxidation of the high-temperature conductor when it comes into contact with air. Recording the ambient temperature can also help track the stability of the cooling process.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended embodiments and their equivalents.

Claims

1. An annealing furnace process, characterized in that, Includes the following steps: Step 1: Conductor loading preparation; Step 2: Place the conductor and seal the inner cover; Step 3: Evacuate the furnace and fill it with nitrogen; Step 4: Install the outer cover and heat up; Step 5: Atmosphere purification and heat preservation at high temperatures; Step Six: Forced circulation of nitrogen to accelerate cooling; Step 7: Remove from oven after cooling; Step five includes the following steps: When the outer casing temperature reaches 330℃, turn off the heating power, open the vacuum valve, pump to 0.01MPa at a rate of 3-5kPa / min, maintain the pressure for 10 minutes, then purge with nitrogen to 0.14MPa, maintain the pressure for 5 minutes, then restart the heating power to maintain the outer casing temperature at 330℃, and then keep it at that temperature for 6-10 hours. Step six includes the following steps: After the heat preservation is completed, turn off the heating power of the outer cover, remove the outer cover, and introduce clean nitrogen into the furnace. Use a fan to force the nitrogen to circulate between the inner cover and the conductor, with the flow rate controlled at 20-25 m³ / h. The circulating gas is cooled by the cooler before entering the inner cover, continuously removing heat. Then, record the temperature inside the inner cover every 15 minutes. When the temperature drops to 100℃, reduce the nitrogen flow rate to 10-15 m³ / h until the temperature drops below 40℃.

2. The annealing furnace process according to claim 1, characterized in that: The vacuuming process inside the furnace in step three includes the following steps: S1: Evacuate the furnace to -0.03MPa at a rate of 5-8kPa / min, maintain the pressure for 5 minutes, and observe the vacuum gauge reading. If the pressure drop is ≤0.002MPa, it is qualified. If it exceeds the standard, check for leaks. S2: Continue pumping at a rate of 3-5 kPa / min until -0.06 MPa is reached, maintain the pressure for 5 minutes, and then check the seal again; S3: Slowly pump to 0.01MPa, close the vacuum valve, maintain the pressure for 10 minutes, and ensure that the pressure fluctuation is ≤0.001MPa.

3. The annealing furnace process according to claim 1, characterized in that: Step three, which involves purging the furnace with nitrogen, includes the following steps: s1: Open the nitrogen cylinder valve and adjust the output pressure to 0.2-0.25MPa using the pressure reducing valve; s2: Open the inlet valve and charge nitrogen into the furnace at a flow rate of 8-12 m³ / h. When the pressure rises to 0.05 MPa, close the valve and maintain the pressure for 5 minutes. Then continue charging to 0.14 MPa and close the inlet valve. S3: Ensure that the pressure drop inside the furnace is ≤0.003MPa within 30 minutes. If the pressure drop exceeds the limit, nitrogen must be released and the inner cover seal must be rechecked.

4. The annealing furnace process according to claim 1, characterized in that: In step five, the heat preservation stage should begin after nitrogen is introduced and last for 6-10 hours. The furnace temperature should be recorded every 2 hours. The temperature difference between the outer and inner covers should be controlled to be ≤10℃ and the nitrogen pressure fluctuation to be ≤0.005MPa to ensure parameter stability.

5. The annealing furnace process according to claim 1, characterized in that: Step six, which involves forced nitrogen circulation to accelerate cooling, includes the following steps: F1: Introduce clean nitrogen into the furnace and force the nitrogen to circulate between the inner cover and the conductor using a fan. The flow rate is 20-25 m³ / h. The circulating gas passes through a cooler with an inlet water temperature of ≤25℃. After cooling, the gas enters the inner cover to continuously remove heat. F2: Record the temperature inside the inner cover every 15 minutes. When the temperature drops to 100℃, reduce the nitrogen flow rate to 10-15m³ / h until the temperature drops below 40℃. F3: Once the temperature stabilizes below 40℃, shut off the nitrogen circulation system and maintain a nitrogen positive pressure ≥0.1MPa inside the inner shroud.

6. The annealing furnace process according to claim 1, characterized in that: In step four, the heating rate needs to be controlled at 5-8℃ / min to avoid rapid heating causing thermal stress in the inner cover or conductor.

7. The annealing furnace process according to claim 1, characterized in that: The concentration of nitrogen gas introduced in steps three, five, and six is ​​consistent, and the purity of nitrogen gas is ≥99.99% in all of them.

8. The annealing furnace process according to claim 1, characterized in that: In step seven, the exhaust valve should be opened slowly after the furnace is unloaded to reduce the nitrogen pressure inside the inner shroud to 0 MPa. The surface temperature of the conductor should be measured at multiple points using an infrared thermometer to ensure that it is ≤40℃, and the ambient temperature should be recorded at the same time.

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