High-temperature nitriding atmosphere concentration closed-loop control device and control process

Abstract

The invention discloses a high-temperature nitriding atmosphere concentration closed-loop control device and a high-temperature nitriding atmosphere concentration closed-loop control process. The device comprises a nitriding atmosphere supply module, a flow regulation module, a reaction device, a concentration detection module, a cooling device, a tail gas treatment device, a controller and an auxiliary detection module. A concentration detection module is arranged at the tail end of a reaction device to collect nitrogen concentration signals in real time, pressure and temperature signals collected by an auxiliary detection module are combined, and after the signals are processed by a controller with a built-in PID adjustment algorithm, the gas inlet flow of a flow adjustment module is fed back and adjusted, so that a flow-nitrogen concentration double-closed-loop control system is formed. The problems that an existing open-loop control device is low in nitrogen concentration control precision, poor in stability and weak in anti-interference capacity are solved, it can be ensured that the nitrogen concentration on the surface of the material is stabilized within an effective nitridation interval, and the device is suitable for various nitridation process scenes such as material nitridation and semiconductor device preparation.

Description

Technical Field

[0001] This invention relates to the fields of material surface treatment and semiconductor manufacturing technology, specifically to a closed-loop control device and control process for high-temperature nitriding atmosphere concentration in a material nitriding process. Background Technology

[0002] In industrial processes such as material nitriding and semiconductor device fabrication, the stability of nitrogen concentration on the material surface directly determines the product's performance indicators. For example, in the nitriding process of metal materials, fluctuations in the nitrogen concentration on the metal surface over time can lead to increased porosity, disordered growth of the compound layer, and consequently, uneven surface hardness and deviations in the thickness of the nitrided layer. In the silicon nitride thin film deposition process of semiconductor manufacturing, instability in the nitrogen concentration on the material surface can affect the film's density and electrical properties, thereby reducing device yield.

[0003] Existing nitriding atmosphere control devices mostly employ open-loop control, meaning the inlet flow rate is set based on preset process parameters, which cannot respond in real time to changes in nitrogen concentration within the reactor or on the material surface. Since the nitrogen concentration on the material surface is dynamically changing during the reaction, open-loop control struggles to maintain a constant nitriding atmosphere concentration. Summary of the Invention

[0004] To address the shortcomings of the prior art, the present invention aims to provide a closed-loop control device and control process for high-temperature nitriding atmosphere concentration. This device collects nitrogen concentration signals in real time by setting a concentration detection module at the tail end of the reaction device, and then processes the signals and feeds them back to the flow regulation module at the inlet to achieve dynamic closed-loop control of the nitriding atmosphere concentration, ensuring that the nitrogen concentration on the surface of the materials in the reaction device remains stable within the effective nitriding range.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A high-temperature nitriding atmosphere concentration closed-loop control device, characterized in that it comprises: a nitriding atmosphere supply module, a flow regulation module, a reaction device, a concentration detection module, a cooling device, and an exhaust gas treatment device connected in sequence.

[0007] The nitrogen atmosphere supply module is used to provide high-purity ammonia, nitrogen and argon, and its outlet is connected to the inlet of the flow regulation module through an inlet pipe.

[0008] The flow regulation module is used to regulate the proportion and flow rate of the gas entering the reaction device. Its outlet end is connected to the inlet of the reaction device through the inlet pipe. The signal output end of the flow regulation module is electrically connected to the controller to collect the actual inlet flow rate signal in real time.

[0009] The reaction device, which serves as the nitriding reaction site for the workpiece to be processed, has an exhaust port at its tail end and an auxiliary detection module inside.

[0010] A concentration detection module is installed at the exhaust port of the reaction device to detect the nitrogen concentration in the exhaust gas at the tail end of the reaction device in real time. Its signal output terminal is electrically connected to the signal input terminal of the controller.

[0011] The cooling device has its inlet end connected to the outlet end of the reaction device via an exhaust pipe and an outlet valve, and is used to cool the high-temperature mixed gas discharged from the reaction device.

[0012] The exhaust gas treatment device has an inlet end connected to the outlet end of the cooling device through an exhaust pipe and a check valve. It is used to absorb harmful gases in the exhaust gas and has an outlet valve at the tail end for venting harmless gases.

[0013] The auxiliary detection module includes a pressure sensor and a temperature sensor, which are used to collect pressure and temperature signals in the reaction device in real time. The signal output terminals of the module are electrically connected to the controller.

[0014] The controller has a built-in PID control algorithm. Its signal input terminal is electrically connected to the concentration detection module and the auxiliary detection module, respectively, and its signal output terminal is electrically connected to the flow control module and the reaction device, respectively. It is used to receive the actual nitrogen concentration signal, pressure signal and temperature signal, compare and calculate with the preset concentration value, and then output the flow control signal to the flow control module.

[0015] The controller combines the nitrogen concentration signal collected by the concentration detection module, the pressure and temperature signals collected by the auxiliary detection module, and the actual intake flow signal collected by the flow regulation module to form a flow-nitrogen concentration dual closed-loop control system, which provides feedback to adjust the intake flow of the flow regulation module.

[0016] Preferably, the above-mentioned nitriding atmosphere supply module includes an ammonia storage tank, a nitrogen storage tank, an argon storage tank, and three corresponding pressure reducing valves. Each storage tank is connected to a corresponding pressure reducing valve at its outlet to achieve pressure regulation, and each pressure reducing valve is electrically connected to the controller.

[0017] Preferably, the above-mentioned flow regulation module adopts a gas flow controller, which can achieve flow regulation with an accuracy of ±0.1% according to the control signal.

[0018] Preferably, the above concentration detection module uses a high-precision nitrogen sensor with a detection range of 0-100%vol and a detection accuracy of ±0.1%vol.

[0019] Preferably, the controller is also connected to a human-machine interface unit, which includes a touch screen and buttons for setting the nitrogen gas ratio, nitrogen gas flow rate, preset nitrogen concentration value, and temperature curve, while displaying the actual nitrogen concentration, flow rate, pressure, and temperature parameters.

[0020] Preferably, the controller is also connected to an alarm unit, which includes an audible and visual alarm. When the nitrogen concentration deviates from the preset range by ±5%, the pressure exceeds the preset range, or the equipment malfunctions, the controller triggers the alarm unit to issue an alarm signal.

[0021] Preferably, the controller compensates and corrects the actual nitrogen concentration signal transmitted by the concentration detection module based on the pressure and temperature signals collected by the auxiliary detection module, and then compares and calculates it with the preset concentration value.

[0022] The high-temperature nitriding atmosphere concentration closed-loop control process of the present invention is characterized by comprising the following steps:

[0023] Step S1: Initialization settings: Set the target nitrogen concentration, temperature curve and pressure parameters on the material surface through the human-machine interaction unit. The controller calculates the initial gas flow rate of each component of the mixed gas according to the target nitrogen concentration and outputs the control signal to the flow regulation module to control the ammonia, nitrogen and argon to enter the reaction device in proportion.

[0024] Step S2: Real-time multi-parameter detection: The nitrogen concentration signal in the exhaust gas at the tail end of the reaction device is collected through the concentration detection module, the actual intake flow rate signal of each component is collected through the flow regulation module, and the pressure and temperature signals inside the reaction device are collected through the auxiliary detection module. All detection signals are transmitted to the controller in real time.

[0025] Step S3: Signal compensation and deviation calculation. The controller compensates and corrects the nitrogen concentration detection value based on the detection values ​​of the pressure sensor and temperature sensor, compares the corrected actual nitrogen concentration value with the tail concentration value corresponding to the target nitrogen concentration, and calculates the concentration deviation.

[0026] Step S4: PID feedback adjustment. The controller calculates the concentration deviation using the built-in PID adjustment algorithm and outputs a control signal to the flow regulation module in combination with the actual air intake flow signal to accurately adjust the air intake flow of each component.

[0027] Step S5: Continuous closed-loop control, repeating steps S2-S4, maintaining the nitrogen concentration on the surface of the material in the reaction device within the target range through real-time detection and dynamic adjustment;

[0028] The process achieves high-precision dynamic control of the nitriding atmosphere concentration through a dual closed-loop control logic of flow rate and nitrogen concentration.

[0029] Preferably, it also includes an abnormal alarm step: when the nitrogen concentration, pressure or temperature exceeds the preset range, the controller triggers the alarm unit to issue an audible and visual alarm and display a fault prompt, while automatically adjusting the flow parameters to try to restore the normal state.

[0030] Preferably, the process also includes a tail gas treatment step: the mixed gas discharged from the reaction device is cooled by a cooling device and then enters the tail gas treatment device to absorb harmful gases such as ammonia and hydrogen. The treated harmless gases such as nitrogen and argon are discharged through an exhaust valve.

[0031] The core advantages of this application

[0032] 1. High-precision closed-loop control significantly improves stability. By constructing a dual closed-loop control system for flow rate and nitrogen concentration, and combining a flow regulation module and a nitrogen concentration detection module with ±0.1% accuracy, along with PID algorithm and pressure / temperature compensation correction mechanism, the pain points of traditional open-loop control, such as "inability to respond to changes in concentration in the cavity in real time, poor stability, and weak anti-interference", are completely solved. This ensures that the nitrogen concentration on the material surface is stably maintained within the target range, effectively improving the consistency and yield of nitrided products.

[0033] 2. The entire process is intelligent and designed for safety and environmental protection. It integrates real-time monitoring of multiple parameters (concentration, flow rate, pressure, temperature), visual human-machine interaction, automatic alarm for abnormalities and emergency adjustment functions. It is also equipped with a cooling device and a harmful gas absorption type exhaust gas treatment system, which reduces the difficulty of manual operation and meets the safety and environmental protection requirements of high-temperature nitriding process. Attached Figure Description

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings:

[0035] Figure 1 This is a technical roadmap of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of the device of the present invention;

[0037] In the diagram: 1-Ammonia storage tank, 2, 4, 6-Pressure reducing valve, 3-Nitrogen storage tank, 5-Argon storage tank, 7, 8, 9-Gas flow controller, 10-Inlet valve, 11-Reaction device, 12-Pressure sensor, 13-Temperature sensor, 14-Outlet valve, 15-Sampler pretreatment unit, 16-Nitrogen sensor, 17-Cooling device, 18-Check valve, 19-Tail gas treatment device, 20-Vacuum valve, 21-Human machine interaction unit, 22-Controller, 23-Alarm unit. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0039] As shown in the attached figure, a closed-loop control device for nitrogen concentration in a high-temperature nitriding atmosphere includes a nitriding atmosphere supply module 1-6, a flow regulation module 7-9, a reaction device 11, a concentration detection module 15-16, a cooling device 17, an exhaust gas treatment device 19, a controller 22, and an auxiliary detection module 12-13.

[0040] Nitrogenation atmosphere supply modules 1-6 are used to supply high-purity ammonia 1, nitrogen 3 and argon 5, and their outlet end is connected to the inlet end of flow regulation modules 7-9 through an inlet pipe.

[0041] The flow regulation module 7-9 is used to regulate the gas ratio and gas flow rate entering the reaction device 11. Its outlet end is connected to the gas inlet of the reaction device 11 through the gas inlet pipe. The flow regulation module adopts gas flow controller 7, gas flow controller 8, and gas flow controller 9, which can achieve flow regulation with an accuracy of ±0.1% according to the control signal. The signal output terminals of gas flow controller 7, gas flow controller 8, and gas flow controller 9 are electrically connected to controller 22 to collect the actual gas flow signal in real time and form a flow-nitrogen concentration dual closed-loop control.

[0042] The reaction device 11 is the nitriding reaction site for the workpiece to be processed. It is equipped with an exhaust port at its tail end, and a concentration detection module 15-16 is installed at the exhaust port. An auxiliary detection module 12-13 is installed inside.

[0043] The concentration detection module 15-16 is used to detect the nitrogen concentration in the exhaust gas at the tail end of the reaction device 11 in real time. The concentration detection module 15-16 adopts a high-precision nitrogen sensor 16 with a detection range of 0-100%vol and a detection accuracy of ±0.1%vol. The signal output terminal of the concentration detection module 15-16 is electrically connected to the signal input terminal of the controller 22 to ensure real-time transmission of the detection signal.

[0044] The controller 22 is the core control unit, with a built-in PID (proportional-integral-derivative) regulation algorithm. The signal input terminals of the controller 22 are electrically connected to the concentration detection modules 15-16 and the auxiliary detection modules 12-13, respectively, and the signal output terminals are electrically connected to the flow regulation module 7-9 and the reaction device 11, respectively. The controller 22 receives the actual nitrogen concentration signal transmitted by the concentration detection module 15-16, compares it with the preset concentration value, and outputs a precise flow regulation signal to the flow regulation module 7-9.

[0045] The auxiliary detection module 12-13 includes a pressure sensor 12 and a temperature sensor 13, which are respectively installed inside the reaction device 11 to collect pressure and temperature signals inside the reaction device 11 in real time. The signal output terminals of the pressure sensor 12 and the temperature sensor 13 are electrically connected to the controller 22. The controller 22 compensates and corrects the flow regulation signal according to the pressure and temperature signals, and compensates and corrects the temperature regulation signal in real time according to the temperature signal.

[0046] The inlet of the cooling device 17 is connected to the outlet of the reaction device 11 through an exhaust pipe and an outlet valve 14, and is used to cool the high-temperature mixed gas discharged from the reaction device 11.

[0047] The exhaust gas treatment device 19 is connected to the outlet of the cooling device 17 through an exhaust pipe and a check valve 18. It is used to absorb and remove harmful gases such as ammonia and hydrogen in the exhaust gas. The exhaust gas treatment device 19 is connected to an vent valve 20 at the tail end for venting harmless gases such as nitrogen and argon.

[0048] The gas supply modules 1-6 include an ammonia storage tank 1, a nitrogen storage tank 3, an argon storage tank 5, and three corresponding pressure reducing valves 2, 4, and 6. Each storage tank is connected to a corresponding pressure reducing valve at its front end to achieve pressure regulation.

[0049] The controller is also connected to a human-machine interface unit 21 and an alarm unit 23. The human-machine interface unit 21 includes a touch screen and buttons for setting the nitrogen gas ratio, nitrogen gas flow rate, preset nitrogen concentration value, and temperature curve, while displaying parameters such as actual nitrogen concentration, flow rate, pressure, and temperature. The alarm unit 23 includes an audible and visual alarm. When the nitrogen concentration deviates from the preset range by ±5%, the pressure exceeds the preset range, or the equipment malfunctions, the controller 22 will trigger the alarm unit 23 and issue an alarm signal.

[0050] In this embodiment, the nitriding process requires the nitrogen concentration on the material surface within the reaction device 11 to be stable within a preset range. The specific usage steps of the device of the present invention (i.e., the closed-loop control process of high-temperature nitriding atmosphere concentration) are as follows:

[0051] Step S1: Initialization settings. The nitrogen concentration, temperature curve, and pressure parameters on the material surface are set through the human-machine interaction unit 21. The controller 22 calculates the initial gas flow rate of each component of the mixed gas according to the preset value of the nitrogen concentration on the material surface and outputs control signals to the gas flow controller 7, gas flow controller 8, and gas flow controller 9. The ammonia in the ammonia storage tank 1 is depressurized by the pressure reducing valve 2 and the flow rate is adjusted by the gas flow controller 7. The nitrogen in the nitrogen storage tank 3 is depressurized by the pressure reducing valve 4 and the flow rate is adjusted by the gas flow controller 8. The argon in the argon storage tank 5 is depressurized by the pressure reducing valve 6 and the flow rate is adjusted by the gas flow controller 9. The mixed gas then enters the reaction device 11 through the inlet valve 10.

[0052] Step S2: Real-time detection. Nitrogen sensor 16 collects the nitrogen concentration signal in the exhaust gas at the tail end of the reaction device 11 in real time. Gas flow controller 7, gas flow controller 8, and gas flow controller 9 collect the inlet flow signals of each component in real time. Pressure sensor 12 and temperature sensor 13 collect the pressure and temperature signals in the reaction device 11 respectively. All detection signals are transmitted to controller 22 in real time.

[0053] Step S3: Signal processing. The controller 22 receives each detection signal. First, it compensates and corrects the nitrogen concentration detection value based on the detection values ​​of the pressure sensor 12 and the temperature sensor 13. Then, it compares the corrected actual concentration value with the tail-end concentration value corresponding to the preset nitrogen concentration on the material surface and calculates the concentration deviation.

[0054] Step S4: Feedback adjustment. The controller 22 calculates the concentration deviation using a PID algorithm and, combined with the intake flow signal collected by the gas flow controller, outputs a control signal to the flow regulation module 7-9 to precisely adjust the intake flow of each component.

[0055] Step S5: Continue the closed loop and repeat steps S2-S4. The controller 22 continuously adjusts the inlet flow of the gas flow controllers 7, 8, and 9 according to the real-time detected nitrogen concentration signal to ensure that the nitrogen concentration on the surface of the material in the reaction device 11 is stable within the preset range.

[0056] Step S6: Cooling the mixed gas. The mixed gas discharged from the reaction device 11 enters the cooling device 17 through the outlet valve 14, and the cooling device 17 achieves the cooling treatment.

[0057] Step S7: Exhaust gas treatment. The mixed gas cooled by the cooling device 17 enters the exhaust gas treatment device through the exhaust pipe and the check valve 18. The harmful gas is absorbed by the exhaust gas absorption device 19, and the treated harmless gas is discharged through the vent valve 20.

[0058] Step S8: Abnormal alarm. If the pressure, temperature or nitrogen concentration of the exhaust gas in the reaction device 11 exceeds the preset alarm range, the controller 22 will immediately trigger the alarm 23 to issue an audible and visual alarm signal, and display the corresponding fault prompt on the human-machine interaction unit 21. At the same time, it will automatically make appropriate adjustments to try to restore each parameter to the normal value.

[0059] Example: High-temperature nitriding process for 310S stainless steel

[0060] Process parameter settings:

[0061] Target material: 310S stainless steel workpiece (80mm×80mm×10mm, surface roughness ≤0.8μm)

[0062] Target nitrogen concentration: 10% vol (material surface)

[0063] Preset temperature curve: Room temperature → 500℃ (heating rate 4℃ / min) → Hold for 6 hours → Natural cooling

[0064] Preset pressure: 0.1 MPa (absolute pressure)

[0065] Initial gas ratio: ammonia: nitrogen: argon = 4:2:1 (total flow rate 6 L / min)

[0066] Device operation process:

[0067] Step S1: Initialization settings. Input the above parameters through the human-machine interaction unit 21. The controller 22 outputs control signals to the reaction device 11 according to the target nitrogen concentration and process model. After the reaction device 11 is heated to 500℃ and kept at that temperature, the initial gas flow rate is calculated based on the nitriding reaction kinetic model of 310S stainless steel: ammonia 3.43L / min, nitrogen 1.71L / min, argon 0.86L / min. The control signals are output to the flow regulation module (gas flow controller 7-9). The gas is depressurized by the corresponding pressure reducing valves (2, 4, 6) and enters the reaction device 11 in proportion.

[0068] Step S2: Real-time detection. The high-precision nitrogen sensor (16) of the concentration detection module (15-16) collects the nitrogen concentration at the exhaust port in real time. The initial detection value is 8.3% vol. The auxiliary detection module (12-13) provides feedback on the temperature inside the reaction device as 500℃±1.5℃ and the pressure as 0.1MPa±0.004MPa. The flow regulation module (7-9) provides feedback on the deviation between the actual intake flow rate and the initial set value as ≤±0.03L / min, which meets the accuracy requirement of 0.1%.

[0069] Step S3: Signal processing and feedback adjustment: The controller 22 compensates and corrects the nitrogen concentration detection value based on the temperature and pressure signals. The correction formula (1) is as follows:

[0070] (1)

[0071] In the formula, p0 = 0.1 MPa (standard atmospheric pressure), T0 = 273.15 K (standard temperature), p = 0.103 MPa (actual pressure), and T = 773.15 K (actual temperature).

[0072] The corrected actual nitrogen concentration is 8.12% vol, which deviates from the target value of 10% vol by 1.88% vol.

[0073] The controller has a built-in PID algorithm (2):

[0074] (2)

[0075] In the formula, the initial value is set to K. p =1.0、T i =7s,T d =2s.

[0076] The controller 22 outputs the calculated adjustment signal to the flow regulation module (7-9): the ammonia flow rate is increased to 4.2 L / min, the nitrogen flow rate is maintained at 1.71 L / min, and the argon flow rate is adjusted to 0.59 L / min.

[0077] Step S4: Continuous closed-loop control, repeating the above detection-correction-adjustment process, completing one cycle every 8 seconds. During the heat preservation stage, the nitrogen concentration on the material surface remains stable at 10% vol ± 0.1% vol, the pressure remains stable at 0.1 MPa ± 0.002 MPa, and the temperature fluctuation is ≤ ±1℃. The flow regulation module (7-9) provides real-time feedback on the actual flow rate, and the controller 22 dynamically corrects the adjustment signal to ensure that the flow deviation is always controlled within ±0.05 L / min.

[0078] Step S5: Exhaust gas treatment: The cooling device reduces the exhaust temperature from 500℃ to below 60℃. The ammonia absorption rate of the exhaust gas treatment device is ≥99.5%. The ammonia concentration in the gas discharged from the vent valve is less than or equal to 0.01 vol, which complies with GB 3095-2012 "Ambient Air Quality Standard".

[0079] Final result:

[0080] Surface hardness: HV850±25;

[0081] Nitriding layer thickness: 0.4mm ± 0.02mm (layer depth uniformity deviation ≤ 5%);

[0082] The nitrided layer has a fibrous structure with no obvious pores and uniformly distributed nitrides.

[0083] Corrosion resistance: No rust was observed in the neutral salt spray test (NSS) for 72 hours (pitting corrosion appeared in the salt spray test of unnitrided 310S stainless steel after 24 hours).

[0084] Product consistency: The hardness deviation of 20 workpieces in the same batch is ≤3%, and the nitriding layer thickness deviation is ≤4%.

[0085] Comparative example: High-temperature nitriding process of 310S stainless steel using a traditional open-loop control device.

[0086] Equipment configuration: No concentration detection module, no auxiliary detection module, the intake flow rate is controlled only by manually setting the flow meter opening, and there is no closed-loop feedback adjustment function.

[0087] Process parameters: consistent with the example (target nitrogen concentration 10% vol, treatment temperature 500℃, holding time 6h, pressure 0.1MPa).

[0088] Control method: The initial gas flow rate (ammonia 3.5L / min, nitrogen 1.7L / min, argon 0.8L / min) is set based on experience. There is no dynamic adjustment throughout the process. Temperature and pressure data are recorded manually only once every 2 hours.

[0089] Final result:

[0090] Nitrogen concentration fluctuation during nitriding: 10% vol ± 4% vol (maximum deviation up to 6.2% vol)

[0091] Surface hardness: HV700-950 (deviation ≥18%)

[0092] Nitriding layer thickness: 0.3-0.55mm (deviation ≥37.5%)

[0093] Microstructure of the nitrided layer: Porosity reaches 2%-3% in some areas, and nitrides are unevenly distributed.

[0094] Corrosion resistance: Pitting corrosion occurred after 48 hours of neutral salt spray test (NSS).

[0095] Product consistency: The hardness deviation of 20 workpieces in the same batch is ≥15%, and the nitriding layer thickness deviation is ≥28%.

[0096] Core performance comparison table:

[0097] Table 1

[0098] Comparison indicators This application (executive) Traditional open-loop control (comparative proportional) Performance improvement Nitrogen concentration control accuracy ±0.1% vol ±41% vol 40 times Uniformity of nitrided layer thickness Deviation ≤4% Deviation ≤28% 7 times Surface hardness consistency Deviation ≤3% Deviation ≤15% 5 times Corrosion resistance ≥99.8% ≤85% 17.4% Intensity of artificial intervention Only initial parameter settings are required; no further operations are needed. Manual inspection every 2 hours, flow rate needs to be adjusted manually. Completely liberate human labor

[0099] Enhancement of Creativity and Practicality:

[0100] The technical advantages of this application are particularly prominent in light of the processing characteristics of 310S stainless steel (high chromium nickel austenitic stainless steel, which has great difficulty in nitrogen atom diffusion and requires extremely high stability in the nitriding atmosphere):

[0101] 1. Dual-loop control system adapts to challenging nitriding scenarios: The nitrogen atom diffusion coefficient of 310S stainless steel is only 1 / 5 to 1 / 3 that of ordinary carbon steel. Traditional open-loop control cannot cope with the dynamic changes in nitrogen concentration during diffusion, resulting in uneven nitrided layers and high porosity. This application uses a dual-loop system of "real-time flow calibration - dynamic concentration control" combined with pressure / temperature compensation correction to ensure that the nitrogen concentration on the surface of 310S stainless steel remains stable within the target range at 500℃, solving the industry pain point of poor uniformity of nitrided layers in high-chromium-nickel austenitic stainless steel.

[0102] 2. Targeted optimization of PID algorithm parameters: For the 500℃ high-temperature nitriding scenario, the controller’s built-in PID parameter self-tuning logic can automatically adapt to the nitrogen diffusion characteristics of 310S stainless steel, and can achieve rapid convergence of deviation without manual adjustment (the concentration deviation converges from 1.88%vol to ±0.1%vol in only 3 adjustment cycles, taking 24s), which is significantly better than the “lag adjustment” mode of traditional open-loop control.

[0103] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the spirit of the invention. The scope of this invention is not limited to the contents of the specification; its protection scope must be determined according to the scope of the claims.

Claims

1. A closed-loop control device for high-temperature nitriding atmosphere concentration, characterized in that, include: The nitrogen atmosphere supply module (1-6), flow regulation module (7-9), reaction device (11), concentration detection module (15-16), cooling device (17) and exhaust gas treatment device (19) are connected in sequence. Among them, the nitriding atmosphere supply module (1-6) is used to provide high-purity ammonia, nitrogen and argon, and its outlet end is connected to the inlet end of the flow regulation module (7-9) through the inlet pipe; The flow regulation module (7-9) is used to regulate the gas ratio and gas flow rate entering the reaction device (11). Its outlet end is connected to the inlet of the reaction device (11) through the inlet pipe. The signal output end of the flow regulation module (7-9) is electrically connected to the controller (22) for real-time acquisition of the actual inlet flow rate signal. The reaction device (11) serves as the nitriding reaction site for the workpiece to be processed. It has an exhaust port at its tail end and an auxiliary detection module (12-13) inside. The concentration detection module (15-16) is installed at the exhaust port of the reaction device (11) and is used to detect the nitrogen concentration in the exhaust gas at the tail end of the reaction device (11) in real time. Its signal output terminal is electrically connected to the signal input terminal of the controller (22). The cooling device (17) is connected to the outlet of the reaction device (11) through an exhaust pipe and an outlet valve (14) at its inlet end, and is used to cool the high-temperature mixed gas discharged from the reaction device (11). The exhaust gas treatment device (19) has an inlet end connected to the outlet end of the cooling device (17) through an exhaust pipe and a check valve (18) to absorb harmful gases in the exhaust gas. The tail end is connected to an exhaust valve (20) to exhaust harmless gases. The auxiliary detection module (12-13) includes a pressure sensor (12) and a temperature sensor (13), which are used to collect pressure and temperature signals in the reaction device (11) in real time, and their signal output terminals are electrically connected to the controller (22); The controller (22) has a built-in PID control algorithm. Its signal input terminal is electrically connected to the concentration detection module (15-16) and the auxiliary detection module (12-13) respectively, and its signal output terminal is electrically connected to the flow control module (7-9) and the reaction device (11) respectively. It is used to receive the actual nitrogen concentration signal, pressure signal and temperature signal, compare and calculate with the preset concentration value, and output the flow control signal to the flow control module (7-9). The controller (22) combines the nitrogen concentration signal collected by the concentration detection module (15-16), the pressure and temperature signals collected by the auxiliary detection module (12-13), and the actual air intake flow signal collected by the flow regulation module (7-9) to form a flow-nitrogen concentration dual closed-loop control system, and provides feedback to regulate the air intake flow of the flow regulation module (7-9).

2. The high-temperature nitriding atmosphere concentration closed-loop control device according to claim 1, characterized in that, The nitrogen atmosphere supply module (1-6) includes an ammonia storage tank (1), a nitrogen storage tank (3), an argon storage tank (5), and three corresponding pressure reducing valves. Each storage tank is connected to a corresponding pressure reducing valve at its outlet to achieve pressure regulation. Each pressure reducing valve is electrically connected to the controller (22).

3. The high-temperature nitriding atmosphere concentration closed-loop control device according to claim 1, characterized in that, The flow regulation module (7-9) uses a gas flow controller to achieve flow regulation with an accuracy of ±0.1% based on the control signal.

4. The high-temperature nitriding atmosphere concentration closed-loop control device according to claim 1, characterized in that, The concentration detection module (15-16) uses a high-precision nitrogen sensor (16), which has a detection range of 0-100%vol and a detection accuracy of ±0.1%vol.

5. The high-temperature nitriding atmosphere concentration closed-loop control device according to claim 1, characterized in that, The controller (22) is also connected to a human-machine interaction unit (21), which includes a touch screen and buttons for setting the nitrogen gas ratio, nitrogen gas flow rate, preset nitrogen concentration value, and temperature curve, while displaying the actual nitrogen concentration, flow rate, pressure, and temperature parameters.

6. The high-temperature nitriding atmosphere concentration closed-loop control device according to claim 1, characterized in that, The controller (22) is also connected to an alarm unit (23), which includes an audible and visual alarm. When the nitrogen concentration deviates from the preset range by ±5%, the pressure exceeds the preset range, or the equipment malfunctions, the controller (22) triggers the alarm unit (23) to issue an alarm signal.

7. The high-temperature nitriding atmosphere concentration closed-loop control device according to claim 1, characterized in that, The controller (22) compensates and corrects the actual nitrogen concentration signal transmitted by the concentration detection module (15-16) based on the pressure and temperature signals collected by the auxiliary detection module (12-13), and then compares and calculates it with the preset concentration value.

8. A closed-loop control process for high-temperature nitriding atmosphere concentration, characterized in that, Includes the following steps: Step S1: Initialization settings: Set the target nitrogen concentration, temperature curve and pressure parameters on the material surface through the human-machine interaction unit (21). The controller (22) calculates the initial gas flow rate of each component of the mixed gas according to the target nitrogen concentration and outputs the control signal to the flow regulation module (7-9) to control ammonia, nitrogen and argon to enter the reaction device (11) in proportion. Step S2: Real-time multi-parameter detection: The nitrogen concentration signal in the exhaust gas at the tail end of the reaction device (11) is collected through the concentration detection module (15-16), the actual intake flow rate signal of each component is collected through the flow regulation module (7-9), and the pressure and temperature signals inside the reaction device (11) are collected through the auxiliary detection module (12-13). All detection signals are transmitted to the controller (22) in real time. Step S3: Signal compensation and deviation calculation. The controller (22) compensates and corrects the nitrogen concentration detection value based on the detection values ​​of the pressure sensor (12) and the temperature sensor (13), and compares the corrected actual nitrogen concentration value with the tail concentration value corresponding to the target nitrogen concentration to calculate the concentration deviation. Step S4: PID feedback adjustment, the controller (22) calculates the concentration deviation through the built-in PID adjustment algorithm, and outputs the control signal to the flow adjustment module (7-9) in combination with the actual air flow signal to accurately adjust the air flow of each component; Step S5: Continuous closed-loop control, repeating steps S2-S4, and maintaining the nitrogen concentration on the surface of the material in the reaction device (11) within the target range through real-time detection and dynamic adjustment; The process achieves high-precision dynamic control of the nitriding atmosphere concentration through a dual closed-loop control logic of flow rate and nitrogen concentration.

9. The high-temperature nitriding atmosphere concentration closed-loop control process according to claim 8, characterized in that, It also includes an abnormal alarm step: when the nitrogen concentration, pressure or temperature exceeds the preset range, the controller (22) triggers the alarm unit (23) to issue an audible and visual alarm and display a fault prompt, while automatically adjusting the flow parameters to try to restore the normal state.

10. The high-temperature nitriding atmosphere concentration closed-loop control process according to claim 8, characterized in that, It also includes a tail gas treatment step: the mixed gas discharged from the reaction device (11) is cooled by the cooling device (17) and then enters the tail gas treatment device (19) to absorb harmful gases such as ammonia and hydrogen. The treated harmless gases such as nitrogen and argon are discharged through the vent valve (20).

Images