Gearbox speed-increasing gear ring gas nitriding surface modification heat treatment device and method

Abstract

The application discloses a kind of gear box speed-increasing gear ring gas nitriding surface modification heat treatment device and method, belong to gear gas nitriding technical field, including sealed furnace body, gear ring special tool frame, control system, ammonia supply unit and ammonia closed-loop recovery circulation unit.Ammonia is sprayed from material plate side wall gas passage by base shaft airflow passage, blows jar body heating wall, disturbs the retention gas in furnace to realize forced mixing flow, balances temperature field and nitrogen potential field in furnace, solves the problem that the temperature field in furnace, ammonia cracking rate difference caused by traditional bottom single-point gas inlet is big, guarantees gear ring nitriding environment consistency, improves penetration layer uniformity, reduces heat treatment deformation.Unreacted ammonia tail gas in furnace is recycled after purification by recovery unit, reduces fresh ammonia dosage, reduces raw material consumption, while avoiding ammonia tail gas direct discharge to cause air pollution, equipment can realize heat treatment and tail gas recovery full-automatic linkage control, give consideration to gear ring nitriding processing precision and energy-saving environmental protection demand.

Description

Technical Field

[0001] This invention relates to the field of gear gas nitriding technology, specifically to a heat treatment apparatus and method for gas nitriding surface modification of gearbox speed-increasing gear rings. Background Technology

[0002] As a core precision component of the transmission system, the gear ring speed-increasing gear needs to possess high surface hardness, excellent wear resistance, and extremely low heat treatment deformation. Gas nitriding is currently the most mainstream process for surface modification of gear rings. However, existing conventional gas nitriding heat treatment equipment and supporting gas supply systems have the following two major technical defects, which have long restricted the mass production quality and economic efficiency of gear rings: 1. Poor airflow within the furnace, uneven distribution of temperature and nitrogen potential fields, making it difficult to ensure consistent nitriding of the gear ring; In traditional nitriding furnaces, the ammonia inlet is mostly concentrated at the center of the furnace bottom, with ammonia being transported upwards in a single direction. This results in extremely poor gas flow in the heating areas of the furnace side walls, easily creating stagnant zones. The temperature in the furnace wall heating coil area is too high, leading to excessively rapid ammonia decomposition, while the temperature in the furnace center is too low, resulting in slow ammonia decomposition. This leads to large radial and axial temperature differences and nitrogen potential differences throughout the furnace cavity. This problem directly results in significant variations in the thickness of the nitrided layer on different layers within the same furnace, and uneven surface hardness at different locations within the same layer. It also causes localized defects such as over-nitriding leading to thickened white layers and under-nitriding soft spots, while exacerbating thermal stress deformation of the gear rings, making it impossible to meet the requirements for mass production of high-precision speed-increasing gear rings.

[0003] Second, the single-use efficiency of ammonia is extremely low, the raw material consumption is large, and the direct discharge of tail gas causes environmental pollution and cost waste. In the gas nitriding process, the effective decomposition rate of ammonia is only 20% to 60%, with more than half of the ammonia not participating in the nitriding reaction and being discharged directly with the tail gas. Existing equipment does not have a matching closed-loop recovery and purification device, and most of the unreacted ammonia is directly incinerated or directly vented into the air. On the one hand, this results in a huge waste of high-purity liquid ammonia raw materials, and the ammonia procurement cost for enterprises remains high. On the other hand, ammonia is a toxic, harmful, and irritating gas, and direct discharge of tail gas will cause air pollution. Incineration will also generate secondary pollutants such as nitrogen oxides, which cannot meet the requirements of ultra-low emissions and green production in industrial workshops.

[0004] In summary, existing nitriding equipment cannot simultaneously solve the two major industry pain points of uneven furnace atmosphere temperature and high ammonia consumption. There is a lack of an integrated heat treatment device that can achieve active disturbance and mixing of gas in the furnace, balance the nitrogen potential of the entire temperature field, and at the same time be equipped with fully automatic closed-loop ammonia recovery to reduce raw material consumption. Summary of the Invention

[0005] The main objective of this invention is to provide a heat treatment device and method for gas nitriding surface modification of gearbox speed-increasing gear rings, aiming to solve the technical problems of existing nitriding equipment being unable to simultaneously address uneven furnace atmosphere temperature and high ammonia consumption.

[0006] To achieve the above objectives, the present invention proposes a gas nitriding surface modification heat treatment device for gearbox speed-increasing gear rings, comprising a sealed furnace body, a dedicated tooling frame for gear rings, a control system, an ammonia supply unit, and an ammonia closed-loop recovery and circulation unit. The sealed furnace body is equipped with a sealable and closable tank and a tank cover. A first heating coil is built into the side wall of the tank body to achieve uniform heating, and an exhaust port is provided in the tank cover. The dedicated tooling frame for gear rings is suspended inside the tank cover and includes a base shaft fixed to the inside of the tank cover and axially aligned with the tank body. Multiple parallel material plates are fixed at intervals from top to bottom on the base shaft, and each material plate is equipped with an independently supporting and positioning gear ring support assembly. The tank body... A base is fixed at the center of the bottom, and an exhaust connector is mounted on the base. The end of the base shaft away from the tank cover is recessed inward to form an axially continuous airflow channel. Multiple exhaust channels connected to the airflow channel are evenly opened around the outer circumference of each material plate to achieve uniform distribution of ammonia gas from bottom to top throughout the furnace. The ammonia supply unit is connected to the bottom of the tank and is used to quantitatively supply high-purity ammonia gas into the furnace. The ammonia closed-loop recovery and circulation unit is connected to the exhaust port of the tank cover and is used to collect ammonia-containing tail gas in the furnace and purify and reuse it to achieve ammonia closed-loop circulation. The control system is electrically connected to all electrical control components and integrates automatic control of the entire process of furnace heating, gas nitriding, tail gas recovery and ammonia reuse.

[0007] Preferably, the sealed furnace body includes a tank with the opening facing upwards and a tank cover that is detachably and sealingly connected to the opening; a first receiving cavity is formed inside the side wall of the tank, and a first heating coil is arranged inside the first receiving cavity to uniformly heat the entire side wall of the tank. The ammonia supply unit includes an ammonia tank for storing high-purity ammonia. The ammonia tank is connected to the bottom of the tank by a first gas supply pipe with a first solenoid valve and sealed to the gas outlet connector.

[0008] Preferably, the ammonia closed-loop recovery and circulation unit is provided with a tail gas pretreatment module, an ammonia absorption module, an ammonia desorption and purification module, a drying and pressure stabilization reuse module, and an adsorption liquid circulation module in sequence along the tail gas flow direction; after the ammonia-containing tail gas undergoes condensation and dehydration, pure water adsorption and enrichment, negative pressure low temperature desorption, and deep drying and purification treatment, the high-purity ammonia gas that meets the standards is returned to the ammonia tank.

[0009] Preferably, the exhaust gas pretreatment module includes multiple U-shaped first drying pipes arranged vertically and connected end to end in series. Each lower bend of the first drying pipe can be detachably fitted with a first water collection bottle for collecting condensed liquid water. Inside the first drying pipe, a first copper tube evaporator is arranged along the gas flow direction. Multiple first heat dissipation fins are uniformly welded to the outer wall of the first copper tube evaporator. The first heat dissipation fins are arranged vertically in parallel, and the extension direction of the fins is in the same direction as the gas flow direction of the first drying pipe, thereby enhancing the heat exchange and cooling effect. A first condensing compressor unit connected to the first copper tube evaporator is installed outside the first drying pipe. The first drying pipe's inlet end is connected to the exhaust port at the top of the sealed furnace body via a second gas supply pipe; a gas booster pump is installed on the second gas supply pipe; the first drying pipe's outlet end is connected to a dust filter via a third gas supply pipe; the dust filter's outlet end is connected to a gas buffer tank via a fourth gas supply pipe, and a first one-way valve is installed on the fourth gas supply pipe.

[0010] Preferably, the ammonia absorption module includes a fully enclosed pressure-bearing first water storage tank, the inside of which is pre-vacuumed to -0.08~-0.09MPa to complete vacuum degassing treatment, and the tank contains vacuum-treated pure water as the ammonia adsorption liquid; The top of the first water storage tank is connected to a gas buffer tank through a fifth gas supply pipe, and a second solenoid valve is installed on the fifth gas supply pipe; a first exhaust pipe is also opened at the top of the first water storage tank, an external air pump is connected to the first exhaust pipe, and a third solenoid valve is installed on the first exhaust pipe. The first water tank has a first water outlet pipe installed through the bottom. The first water outlet pipe is connected in sequence to the first water pump and the multi-way diversion second water outlet pipe. Each second water outlet pipe has an atomizing nozzle installed at the end. Multiple sets of atomizing nozzles are evenly distributed in a ring in the upper cavity of the first water tank. The first water storage tank is equipped with a first submerged evaporator, which is completely submerged below the surface of the adsorbent liquid and is connected to a second condensing compressor unit. The first water storage tank integrates multiple sets of online monitoring sensors: a first liquid level sensor and a first liquid phase ammonia sensor are installed at the bottom of the tank to monitor the liquid level of the adsorbent and the concentration of liquid ammonia in real time, and the infusion process is automatically triggered when the concentration reaches the standard; a gas phase ammonia concentration sensor and a gas pressure sensor are installed at the top of the tank.

[0011] Preferably, the ammonia desorption and purification module includes a second water tank; the top of the second water tank is provided with an upwardly contracting conical gas collecting section, and a gas collecting pipe with one end closed is sealed at the top of the conical gas collecting section, and a second one-way valve is installed through the closed end of the gas collecting pipe; The second water tank is connected to the bottom of the first water tank by a third water outlet pipe. Two fourth solenoid valves are arranged at intervals along the liquid flow direction on the third water outlet pipe. A second water pump is installed in the middle section of the pipe between the two sets of fourth solenoid valves. The second water storage tank has a second receiving cavity formed on its side wall and bottom, and the second receiving cavity is filled with a second heating coil. A second liquid-phase ammonia gas sensor is installed inside the second water storage tank.

[0012] Preferably, the drying and pressure-stabilizing recycling module includes a second drying tube composed of multiple vertically arranged U-shaped tubes connected in series end to end, with a second water collection bottle installed at the bend to collect condensed water vapor; a second copper tube evaporator and matching second heat dissipation fins are arranged inside the second drying tube, and it is externally connected to a fourth condensing compressor unit; The air inlet of the second drying tube is connected to the air outlet of the gas collecting tube through the sixth gas supply tube, and the second one-way valve is built into the air inlet section of the sixth gas supply tube; a molecular sieve for adsorbing water vapor is connected in series on the sixth gas supply tube. The outlet of the second drying pipe is connected to the ammonia tank via the seventh gas supply pipe; the seventh gas supply pipe is sequentially equipped with a screw gas compressor and a third one-way valve along the gas flow direction.

[0013] Preferably, the adsorption liquid circulation module includes a third water storage tank, a fourth water outlet pipe, and a fifth water outlet pipe; The fourth water outlet pipe connects the bottom of the third water storage tank and the bottom of the first water storage tank; the fifth water outlet pipe connects the bottom of the third water storage tank and the bottom of the second water storage tank. Two fifth solenoid valves are spaced apart on the fourth water outlet pipe, and a third water pump is installed between the two fifth solenoid valves. The third water pump drives the cooled pure water in the third water storage tank to flow back to the first water storage tank. Two sixth solenoid valves are spaced apart on the fifth water outlet pipe, and a fourth water pump is installed between the two sixth solenoid valves. The fourth water pump drives the adsorbent liquid that has completed ammonia removal in the second water storage tank to be transported to the third water storage tank. The third water storage tank is internally equipped with a second submerged evaporator and externally connected to a third condensing compressor unit; The second water storage tank is equipped with a second liquid level sensor that is linked to the start and stop of the second water pump, and the third water storage tank is equipped with a third liquid level sensor that is linked to the start and stop of the third water pump.

[0014] Preferably, the gear ring support assembly includes a sleeve column vertically disposed on the upper side of the material plate, and the outer wall of the sleeve column is provided with a plurality of support rods for supporting the gear ring at horizontal intervals.

[0015] Preferably, an annular plate is fitted on the outer wall of the end of the base shaft away from the can lid, and a positioning insert ring is provided on the side of the annular plate away from the can lid. A positioning groove is recessed on the base for the positioning insert ring to be inserted.

[0016] Preferably, the ammonia absorption module further includes a second exhaust pipe connected to the outlet of the air pump, the outlet of the second exhaust pipe facing upwards, and the outlet of the exhaust pipe is provided with an electronic igniter linked to the air pump.

[0017] This invention also proposes a method for gas nitriding surface modification heat treatment of gearbox speed-increasing gear rings, employing any one of the aforementioned gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus. The method includes the following steps: S1. Tooling clamping and furnace body sealing: The speed-increasing gear rings to be processed are sequentially fitted onto the outer side of the sleeve column of the gear ring special tooling frame. Line contact support is achieved by relying on the cylindrical support rod. The tank cover is closed to complete the overall sealing of the tank body. The base shaft is centered by the cooperation of the positioning ring and the positioning groove to ensure the overall coaxiality of the tooling. S2. Furnace preheating and gas distribution nitriding: Start the first heating coil to uniformly heat the side wall of the tank to the nitriding process temperature, open the first solenoid valve, and high-purity ammonia gas is sent into the internal airflow channel of the base shaft through the first gas supply pipe and gas outlet connector. Finally, it is radially sprayed out from the gas outlet channel of each material plate side wall, directly blowing the heated wall of the tank, disturbing the gas stagnant near the wall in the furnace to achieve full-area gas mixing, balancing the temperature field and nitrogen potential field in the furnace, and completing the gas nitriding modification treatment of the gear ring at a constant temperature. S3. Staged pretreatment of exhaust gas: The high-temperature ammonia-containing exhaust gas of 500~550℃ generated by the nitriding reaction is discharged from the exhaust port of the tank cover. After being pressurized by the gas booster pump, it is sent into the first drying tube. The exhaust gas is cooled to 30~40℃ by the first condenser compressor unit with heat exchange fins. Most of the saturated water vapor is removed by condensation. After passing through the dust filter to intercept solid impurities, it is buffered in the gas buffer tank. S4. Low-temperature vacuum adsorption enrichment of concentrated ammonia water: The pure water in the first water storage tank is evacuated to -0.08~-0.09MPa in advance to remove dissolved air, and the water temperature in the tank is maintained at 10~20℃. The buffered ammonia-containing tail gas is introduced into the first water storage tank and sprayed with pure water through atomizing nozzles to form water mist. The gas and liquid fully contact and adsorb the ammonia in the tail gas to generate concentrated ammonia water with a concentration of 18%~22%. Relying on multi-sensor linkage control, when the pressure in the tank is over-pressurized and the ammonia concentration reaches the standard, the air inlet is automatically closed and harmless inert gas is discharged. When the concentrated ammonia water is transported, a safety liquid seal level is maintained to prevent air from entering the downstream process. S5. Negative Pressure Low Temperature Desorption and Purification of Ammonia: Before the initial operation, the second water tank is evacuated to remove impurities, and no further evacuation is required. The qualified concentrated ammonia water is delivered to the second water tank and heated to boiling at a constant temperature of 95~105℃ through the second heating coil. Ammonia is automatically desorbed under negative pressure. The desorbed ammonia is discharged in one direction through the second one-way valve at the top. There is no continuous evacuation throughout the process to prevent ammonia escape. The ammonia content of the ammonia water is monitored in real time, and heating is stopped after the desorption meets the standard. S6. Ammonia deep drying and pressure stabilization reuse: The crude ammonia gas is condensed and dehydrated in the second drying tube, and the trace water vapor is deeply adsorbed by the molecular sieve. Then, the pressure is regulated by the screw gas compressor so that the pressure of the reused ammonia gas matches the gas supply pressure of the ammonia tank. The purified high-purity ammonia gas with a purity of ≥99.5% is returned to the ammonia tank to realize closed-loop recycling. S7. Closed-loop circulation of adsorbent and harmless treatment of tail gas: The lean liquid after the analysis is completed is transported to the third water storage tank for pre-cooling and cooling. After cooling, the pure water is returned to the first water storage tank for reuse in ammonia adsorption, realizing the whole process of adsorbent circulation without waste liquid discharge; the trace residual ammonia that is not adsorbed is burned and decomposed by electronic igniter and discharged after meeting the standards.

[0018] In the technical solution of this invention, the ammonia gas outlet channel is opened on the side wall of each material plate, which differs from the traditional single-point gas inlet structure at the bottom center of the furnace. Fresh ammonia gas is directly injected and blown directionally towards the heating coil area on the side wall of the tank, actively disturbing the stagnant gas around the heating wall, breaking the dead zone of the atmosphere on the side of the furnace wall, and realizing forced gas mixing in the furnace. This effectively balances the radial and axial temperature fields and nitrogen potential fields in the furnace, solving the problem of high furnace wall temperature, low furnace center temperature, and excessive difference in ammonia cracking rate in traditional nitriding furnaces from the source. It ensures a consistent nitriding environment for all gear rings in the same furnace, improves the uniformity of the gear ring diffusion layer, and reduces heat treatment deformation defects. At the same time, this device purifies the unreacted ammonia tail gas and directly returns it to the furnace for reuse, significantly reducing the amount of fresh ammonia gas replenishment, reducing raw material consumption, and preventing the direct discharge of ammonia tail gas, eliminating the risk of air pollution, and taking into account both the requirements of gear ring nitriding processing precision and energy-saving and environmentally friendly tail gas treatment. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the special tooling frame for the gear ring of the present invention; Figure 3 For the present invention Figure 2 A magnified schematic diagram of the structure of area A in the diagram; Figure 4 This is a schematic diagram of the material plate and gear ring support assembly of the present invention; Figure 5 This is a schematic diagram of the exhaust gas pretreatment module of the present invention; Figure 6 For the present invention Figure 5 A magnified schematic diagram of the partial structure of region B in the diagram; Figure 7 This is a schematic diagram of the ammonia absorption module structure of the present invention; Figure 8This is a schematic diagram of the ammonia desorption and purification module of the present invention; Figure 9 This is a schematic diagram of the adsorption liquid circulation module structure of the present invention; Figure 10 This is a schematic diagram of the drying, stabilizing, and reusing module structure of the present invention; Figure 11 For the present invention Figure 10 A magnified schematic diagram of the C region.

[0021] Explanation of icon numbers: 1. Sealed furnace body; 12. Tank cover; 13. First heating coil; 2. Gear ring special tooling frame; 21. Base shaft; 21a. Airflow channel; 22. Material plate; 22a. Gas outlet channel; 23. Base; 24. Gas outlet connector; 25. Ring plate; 26. Positioning ring; 27. Gear ring support assembly; 271. Sleeve column; 272. Support rod; 3. Ammonia supply unit; 31. Ammonia tank; 32. First gas transmission pipe; 33. 4. First solenoid valve; 5. Exhaust gas pretreatment module; 6. Second gas supply pipe; 7. First drying pipe; 8. Gas buffer tank; 9. Dust filter; 10. Third gas supply pipe; 11. Fourth gas supply pipe; 12. First condensing compressor unit; 13. First water collection bottle; 14. First copper tube evaporator; 15. First heat dissipation fins; 26. Ammonia absorption module; 37. First water storage tank; 48. Fifth gas supply pipe; 59. First exhaust gas pipe; 60. First exhaust gas pipe; 71. First exhaust gas pipe; 82. First exhaust gas pipe; 93. First exhaust gas pipe; 10. First exhaust gas pipe; 11. First exhaust gas pipe; 12. First exhaust gas pipe; 13. First exhaust gas pipe; 14. First exhaust gas pipe; 15. First exhaust gas pipe; 16. First exhaust gas pipe; 17. First exhaust gas pipe; 18. First exhaust gas pipe; 19 ... 54. Second exhaust pipe; 55. Second solenoid valve; 56. Air pump; 57. Third solenoid valve; 58. First water outlet pipe; 59. Second water outlet pipe; 510. First water pump; 511. Second condensing compressor unit; 512. First submerged evaporator; 6. Ammonia desorption and purification module; 61. Second water storage tank; 62. Gas collection pipe; 63. Second one-way valve; 64. Second heating coil; 65. Third water outlet pipe; 7. Adsorption liquid circulation module; 71. Third condensing compressor unit; 72. Second submerged evaporator; 73. Third water storage tank; 74. Fourth water outlet pipe; 75. Fifth water outlet pipe; 8. Drying, stabilizing, and recycling module; 82. Second drying pipe; 83. Molecular sieve; 84. Sixth gas supply pipe; 85. Seventh gas supply pipe; 86. Fourth condensing compressor unit; 87. Second water collection bottle; 88. Second copper tube evaporator; 89. Second heat dissipation fins.

[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0025] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0026] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0028] This invention proposes a heat treatment apparatus and method for gas nitriding surface modification of gearbox speed-increasing gear rings.

[0029] Please refer to Figures 1 to 11The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment device includes a sealed furnace body 1, a gear ring special tooling frame 2, a control system, an ammonia supply unit 3, and an ammonia closed-loop recovery and circulation unit. The sealed furnace body 1 is equipped with a sealable and closable tank and a tank cover 12. The tank side wall has a built-in first heating coil 13 to achieve uniform heating, and the tank cover 12 has an exhaust port. The gear ring special tooling frame 2 is suspended inside the tank cover 12 and includes a base shaft 21 fixed inside the tank cover 12 and axially aligned with the tank body. Multiple parallel material plates 22 are fixed on the base shaft 21 from top to bottom. Each material plate 22 is equipped with a gear ring support assembly 27 that independently supports and positions the speed-increasing gear ring. The bottom center of the tank is fixed. The furnace has a base 23, on which an exhaust connector 24 is mounted. The base shaft 21 is recessed inward at the end away from the tank cover 12 to form an axially penetrating airflow channel 21a. Multiple exhaust channels 22a connected to the airflow channel 21a are evenly opened around the outer circumference of each material plate 22, so as to achieve uniform gas distribution of ammonia gas from bottom to top throughout the furnace. The ammonia gas supply unit 3 is connected to the bottom of the tank and is used to quantitatively supply high-purity ammonia gas into the furnace. The ammonia gas closed-loop recovery and circulation unit is connected to the exhaust port of the tank cover 12 and is used to collect ammonia-containing tail gas in the furnace and purify and reuse it to achieve ammonia gas closed-loop circulation. The control system is electrically connected to all electrical control components and integrates automatic control of the entire process of furnace heating, gas nitriding, tail gas recovery and ammonia gas reuse.

[0030] In the technical solution of this invention, the ammonia gas outlet channel 22a is opened on the side wall of each material plate 22. Unlike the traditional single-point gas inlet structure at the bottom center of the furnace, fresh ammonia gas is directly injected and blown towards the heating coil area on the side wall of the tank, actively disturbing the stagnant gas around the heating wall, breaking the dead zone of the atmosphere on the side of the furnace wall, and realizing forced gas mixing in the furnace. This effectively balances the radial and axial temperature fields and nitrogen potential fields in the furnace, solving the problem of high furnace wall temperature, low furnace center temperature, and excessive difference in ammonia cracking rate in traditional nitriding furnaces from the source. It ensures that the nitriding environment of all gear rings in the same furnace is consistent, improves the uniformity of the gear ring diffusion layer, and reduces heat treatment deformation defects. At the same time, this device can directly return the ammonia tail gas that has not participated in the reaction to the furnace after purification, which greatly reduces the amount of fresh ammonia gas replenishment, reduces raw material consumption, and eliminates the direct discharge of ammonia tail gas, eliminating the risk of air pollution. It takes into account both the requirements of gear ring nitriding processing precision and tail gas energy saving and environmental protection treatment.

[0031] Please refer to the appendix. Figure 2 The sealed furnace body 1 includes a tank with the opening facing upwards and a detachable and sealed tank cover 12 connected to the opening; a first receiving cavity is opened inside the side wall of the tank, and a first heating coil 13 is arranged inside the first receiving cavity to uniformly heat the entire side wall of the tank. The ammonia supply unit 3 includes an ammonia tank 31 for storing high-purity ammonia. The ammonia tank 31 is connected to the bottom of the tank through a first gas supply pipe 32 with a first solenoid valve 33 and is sealed to the gas outlet connector 24. The first solenoid valve 33 is used to precisely control the start and stop of the ammonia supply.

[0032] The first heating coil 13 is housed inside the first receiving cavity on the side wall of the tank. Unlike the conventional structure of external heating tubes and internally suspended heating tubes, it does not occupy the effective charging space inside the furnace, maximizes the matching of the charging requirements of the multi-layer gear ring tooling, and further increases the production quantity of a single furnace.

[0033] The can lid 12 is detachable and seals the can opening, which facilitates the overall hoisting of the tooling and the loading and unloading of the gear ring, making the loading and unloading of workpieces more efficient. At the same time, the overall sealed furnace body 1 can ensure the closed micro-positive pressure environment required for the nitriding process, prevent the outside air from entering the furnace cavity and causing the gear ring to oxidize and the nitriding layer to contain impurities, and ensure the purity of the nitriding process.

[0034] The sidewall-enclosed heating mode allows heat to radiate slowly from the furnace wall to the center of the furnace cavity, resulting in smaller temperature fluctuations inside the furnace. This precisely matches the process requirements of long-term constant temperature insulation for gas nitriding, avoiding stress deformation inside the gear ring caused by sudden temperature changes.

[0035] Ammonia is supplied uniformly from the gas outlet 24 at the bottom of the tank, perfectly matching the upward airflow channel 21a of the tooling. During the upward process, the ammonia flows fully through each layer of toothed rings, eliminating the problems of airflow short circuits and direct discharge of ammonia, thus further improving gas utilization.

[0036] The first solenoid valve 33 can be precisely started and stopped, and the ammonia supply flow rate and supply time can be adjusted. The control system can accurately match the ammonia flow rate according to the nitriding process parameters of different specifications of speed gear rings, and adapt to the personalized nitriding processing of gear rings with different modules and different hardness requirements.

[0037] Please refer to the appendix. Figure 1 The ammonia closed-loop recovery and recycling unit is arranged in sequence along the tail gas flow direction as follows: tail gas pretreatment module 4, ammonia absorption module 5, ammonia desorption and purification module 6, drying and stabilizing reuse module 8, and adsorption liquid circulation module 7. After the ammonia-containing tail gas undergoes condensation and dehydration, pure water adsorption and enrichment, negative pressure low temperature desorption, and deep drying and purification treatment, the high-purity ammonia gas that meets the standards is returned to the ammonia tank 31, realizing the closed-loop reuse of ammonia gas without waste.

[0038] The process involves four steps: condensation and dehydration, pure water adsorption and enrichment, negative pressure low-temperature desorption, and deep drying. These steps remove water vapor, process impurities, and pyrolysis byproducts from the exhaust gas. The purity of the reused ammonia gas meets the standards for gas nitriding processes, and it can be directly returned to the tank for reuse without secondary purification, thus not affecting the quality of subsequent nitriding processes.

[0039] The adsorption liquid can be recycled in a closed loop, eliminating the need for frequent replacement of the adsorption pure water, reducing the amount of hazardous waste generated, lowering the cost of exhaust gas treatment consumables, and meeting the environmental protection production requirements of industrial workshops.

[0040] The entire process of ammonia-containing exhaust gas is closed-loop and there is no direct discharge of waste gas. This avoids the problems of workshop air pollution and exceeding environmental protection standards caused by the emission of toxic and harmful ammonia exhaust gas. At the same time, it realizes the recycling of ammonia raw materials and significantly reduces the long-term production raw material procurement costs.

[0041] Please refer to the appendix. Figure 5-6 The exhaust gas pretreatment module 4 is used to pretreat high-temperature ammonia-containing exhaust gas by cooling, removing water, and removing dust. It precisely cools the 500-550℃ high-temperature nitrided exhaust gas to 30-40℃ and condenses to remove most of the saturated water vapor in the exhaust gas. It includes multiple U-shaped first drying pipes 42 arranged vertically and connected end to end. Each lower bend of the first drying pipe 42 can be detachably installed with a first water collection bottle 48 for collecting condensed liquid water. Inside the first drying pipe 42, a first copper tube evaporator 49 is arranged along the gas flow direction. Multiple first heat dissipation fins 410 are uniformly welded to the outer wall of the first copper tube evaporator 49. The first heat dissipation fins 410 are arranged vertically in parallel, and the extension direction of the fins is in the same direction as the gas flow of the first drying pipe 42 to enhance the heat exchange and cooling effect. A first condensing compressor unit 47 connected to the first copper tube evaporator 49 is installed outside the first drying pipe 42 to provide a cold source for the evaporator. The first drying pipe 42 has its inlet end connected to the exhaust port at the top of the sealed furnace body 1 via the second gas supply pipe 41. A gas booster pump is installed on the second gas supply pipe 41 to provide stable power for the exhaust gas. The first drying pipe 42 has its outlet end connected to a dust filter 44 via a third gas supply pipe 45 to intercept solid impurities such as metal oxide dust and refractory debris in the exhaust gas. The dust filter 44 has its outlet end connected to a gas buffer tank 43 via a fourth gas supply pipe 46. A first one-way valve is installed on the fourth gas supply pipe 46 to allow only one-way flow of exhaust gas into the buffer tank, preventing the gas in the buffer tank from flowing back to the furnace body and ensuring the one-way stability of the exhaust gas delivery.

[0042] The first condensing compressor unit 47 includes a compressor, a condenser and a throttling device. The installation and connection method between the components in the condensing compressor unit is an existing technical solution. This exhaust gas pretreatment module 4 employs a series-connected U-shaped drying tube combined with a copper tube evaporator and a composite heat exchange structure with heat dissipation fins. Coupled with a standardized condensing compressor unit for stable cooling, it can rapidly and precisely cool the 500–550°C high-temperature nitriding exhaust gas discharged from the furnace to 30–40°C, maximizing the condensation and removal of saturated water vapor from the exhaust gas. Compared to conventional straight-tube cooling structures, the heat dissipation fins significantly increase the heat exchange area, resulting in higher cooling and dehumidification efficiency. Simultaneously, the pre-filter 44 intercepts solid impurities such as metal oxide dust and refractory debris from the furnace in the exhaust gas, preventing dust from entering the downstream recovery module and causing pipeline blockage or adsorption unit failure. Combined with a one-way valve and a gas booster pump, it ensures stable unidirectional delivery of the exhaust gas, preventing backflow that could affect the nitriding gas pressure inside the furnace. This structure removes both water and solid impurities from the exhaust gas in advance, reducing the operating load on the downstream ammonia absorption and desorption module, preventing water vapor from diluting the ammonia water and impurities from contaminating the recovered ammonia, ensuring the purity of subsequent ammonia recovery and purification, indirectly improving the overall ammonia recovery rate, and reducing ineffective ammonia loss.

[0043] Please refer to the appendix. Figure 7 The ammonia absorption module 5 includes a fully enclosed pressurized first water storage tank 51. The first water storage tank 51 is pre-vacuumed to -0.08 to -0.09 MPa to complete vacuum degassing, thoroughly removing dissolved oxygen, nitrogen and other air components from the pure water. The vacuum-treated pure water in the tank serves as the ammonia adsorption liquid, preventing air impurities from being mixed into the subsequent ammonia desorption. The working temperature of the adsorption liquid is kept constant at 10 to 20°C, utilizing the low-temperature environment to improve the ammonia adsorption solubility, which increases the adsorption efficiency by more than 30% compared to room temperature adsorption. The top of the first water storage tank 51 is connected to the gas buffer tank 43 through the fifth gas supply pipe 52. The fifth gas supply pipe 52 is equipped with a second solenoid valve 55 to control the opening and closing of ammonia-containing tail gas entering the water storage tank. The top of the first water storage tank 51 is also provided with a first exhaust pipe 53. The first exhaust pipe 53 is connected to an external air pump 56. A third solenoid valve 57 is installed on the first exhaust pipe 53. A first water outlet pipe 58 is installed through the bottom of the first water storage tank 51. The first water outlet pipe 58 is connected in sequence to the first water pump 510 and the multi-channel diversion second water outlet pipe 59. Each second water outlet pipe 59 is equipped with an atomizing nozzle at its end. Multiple sets of atomizing nozzles are evenly distributed in a ring in the upper cavity of the first water storage tank 51 to realize the atomization and spraying of the adsorbent liquid, thereby increasing the gas-liquid contact area. The atomized pure water fully absorbs the ammonia in the exhaust gas to form saturated concentrated ammonia water with a concentration of 18% to 22%. The first water storage tank 51 is equipped with a first submerged evaporator 512, which is completely submerged below the surface of the adsorbent liquid and is connected to a second condensing compressor unit 511 to continuously maintain a low temperature constant environment of 10-20°C for the adsorbent liquid inside the tank. The first water storage tank 51 integrates multiple sets of online monitoring sensors: a first liquid level sensor and a first liquid phase ammonia sensor are installed at the bottom of the tank to monitor the liquid level of the adsorption liquid and the concentration of liquid ammonia in real time. When the concentration reaches the standard, the infusion process is automatically triggered; a gas phase ammonia concentration sensor and a gas pressure sensor are installed at the top of the tank to monitor the residual ammonia concentration and negative pressure in the tank in real time. All sensor signals are connected to the control system to realize fully automatic closed-loop control of the adsorption process.

[0044] The second condensing compressor unit 511 includes a compressor, a condenser and a throttling device. The installation and connection method between the components in the condensing compressor unit is the existing technical solution. This ammonia absorption module 5 features a multi-optimized structure to specifically improve ammonia adsorption efficiency and the purity of recovered ammonia: First, the adsorption pure water is pre-vacuumed to -0.08 to -0.09 MPa to complete vacuum degassing, thoroughly removing dissolved oxygen and nitrogen from the water and preventing air impurities from entering the desorption process with the ammonia water, thus ensuring the purity of the recovered ammonia from the source; Second, relying on the condenser compressor unit to maintain a constant low-temperature adsorption environment of 10-20℃, combined with atomizing nozzles to increase the gas-liquid contact area, the ammonia absorption efficiency is improved by more than 30% compared to room temperature adsorption, maximizing the capture of residual ammonia in the exhaust gas, reducing ammonia escape, and further reducing ammonia raw material consumption; Third, it is equipped with multi-sensor linkage automatic control logic for gas pressure, gas phase ammonia concentration, liquid phase ammonia concentration, and liquid level. The system can automatically start and stop the air intake, exhaust, and liquid delivery processes according to the real-time operating conditions inside the tank. It automatically closes the air intake valve when the tank is under overpressure, and automatically discharges any unadsorbed harmless nitrogen-containing gases. Fourthly, all water storage tanks in the entire recovery system maintain a fixed safe liquid level during liquid delivery. During the process of delivering concentrated ammonia water from the first water storage tank 51 in this module, the liquid level is monitored in real time by the first liquid level sensor, ensuring that sufficient adsorbent liquid is always maintained to form a sealed liquid seal. This prevents the first water storage tank 51 from emptying, eliminates the direct intrusion of residual ammonia-containing gas into the downstream second water storage tank 61, and prevents impurities from entering the negative pressure desorption chamber, interfering with the desorption environment, and reducing the purity of the produced ammonia. The entire absorption process operates fully automatically without manual intervention, exhibiting strong operational stability and ensuring that the ammonia enrichment effect is always at its optimal state.

[0045] Please refer to the appendix. Figure 8 The ammonia gas desorption and purification module 6 includes a second water storage tank 61; the top of the second water storage tank 61 is provided with an upwardly contracting conical gas collecting section, and a gas collecting pipe 62 with one end closed is sealed at the top of the conical gas collecting section. A second one-way valve 63 is installed through the closed end of the gas collecting pipe 62, which is used to allow only the ammonia gas generated during the desorption process to be discharged outward in one direction, completely preventing the outside air from flowing back into the tank; The second water storage tank 61 is connected to the bottom of the first water storage tank 51 by a third water outlet pipe 65. Two fourth solenoid valves are arranged at intervals along the liquid flow direction on the third water outlet pipe 65. A second water pump is installed in the middle section of the two sets of fourth solenoid valves to realize the automatic delivery of concentrated ammonia water from the absorption module to the analysis module. The second water storage tank 61 has a second receiving cavity on its side wall and bottom. The second receiving cavity is filled with a second heating coil 64. Low-temperature constant temperature heating controls the temperature of the concentrated ammonia water in the tank at 95-105℃, and the ammonia water desorption efficiency is ≥98%. The second water storage tank 61 is equipped with a second liquid phase ammonia sensor to monitor the remaining ammonia content in the tank in real time, determine whether the ammonia desorption reaction is complete, and feed the signal back to the control system to automatically start and stop the heating and liquid delivery processes.

[0046] This ammonia desorption and purification module 6 distinguishes between two operating conditions: initial startup and continuous operation, adapting to actual production operation logic. It employs a closed negative pressure desorption structure without continuous vacuuming: before initial operation, the second water tank 61 is evacuated to remove internal impurities, ensuring a constant ammonia atmosphere during subsequent continuous production, eliminating the need for repeated vacuuming and reducing energy consumption. Low-temperature heating (95-105℃) achieves negative pressure boiling desorption of concentrated ammonia water, efficiently releasing ammonia without high-temperature pyrolysis, achieving a desorption efficiency of over 98%. A top one-way valve enables differential pressure self-venting, allowing only desorbed ammonia to escape in one direction, preventing backflow of external air. Simultaneously, when the second water tank 61 delivers desorbed lean solution, a certain safety level is maintained to prevent the cooling pure water and residual gas in the third water tank 73 from flowing back into the desorption tank, disrupting the negative pressure environment. The entire process eliminates the need for a vacuum pump to continuously extract ammonia, completely preventing ammonia escape and loss problems common in conventional desorption equipment. In addition, the ammonia concentration is monitored in real time by a second liquid phase ammonia sensor. Heating is automatically stopped after the analysis is complete to avoid unnecessary energy consumption. The lean liquid after analysis can be recycled and reused without waste liquid discharge, further reducing production consumables and operating costs.

[0047] Please refer to the appendix. Figure 10-11 The drying and pressure-stabilizing recycling module 8 includes a second drying tube 82 composed of multiple vertically arranged U-shaped tubes connected end to end, with a second water collection bottle 87 installed at the bend to collect condensed water vapor; a second copper tube evaporator 88 and a matching second heat dissipation fin 89 are arranged inside the second drying tube 82, and it is externally connected to a fourth condensing compressor unit 86 to achieve low-temperature deep water removal. The air inlet of the second drying pipe 82 is connected to the air outlet of the gas collecting pipe 62 through the sixth gas supply pipe 84, and the second one-way valve 63 is built into the air inlet section of the sixth gas supply pipe 84; a molecular sieve 83 for adsorbing water vapor is connected in series on the sixth gas supply pipe 84. The outlet of the second drying pipe 82 is connected to the ammonia tank 31 via the seventh gas supply pipe 85 to achieve closed-loop reuse of ammonia. The seventh gas supply pipe 85 is sequentially equipped with a screw gas compressor and a third check valve along the gas flow direction. The screw gas compressor is used to increase the pressure of the returned ammonia to match the gas supply pressure of the ammonia tank 31. The third check valve is used to prevent the high-pressure ammonia in the ammonia tank 31 from flowing back to the second drying pipe 82.

[0048] This drying, pressure stabilizing, and recycling module 8 employs a dual dehydration structure of secondary condensation drying and deep dehydration using molecular sieve 83. This thoroughly removes trace amounts of water vapor carried in the ammonia gas, ensuring the dryness of the recycled ammonia meets standards. Equipped with multi-stage one-way valves, it separately blocks the backflow of furnace tail gas and high-pressure gas from the high-purity ammonia tank 31, preventing cross-contamination between processes and ensuring process stability. A screw-type gas compressor precisely regulates the pressure of the recycled ammonia, ensuring a perfect match between the recovered ammonia pressure and the supply pressure from the fresh ammonia tank 31. This guarantees a smooth integration of the recycled ammonia into the supply pipeline without disturbing the original nitrogen potential and temperature field within the furnace, and without affecting the normal nitriding process of the gear ring. The purified and dried high-purity ammonia can be directly recycled back to the ammonia tank 31 in a closed loop for reuse, achieving ammonia recycling and continuously reducing the amount of fresh ammonia fed, thus implementing cost reduction and environmental protection requirements from the end of the process.

[0049] Please refer to the appendix. Figure 9 The adsorption liquid circulation module 7 includes a third water storage tank 73, a fourth water outlet pipe 74 and a fifth water outlet pipe 75; The fourth water outlet pipe 74 connects the bottom of the third water storage tank 73 and the bottom of the first water storage tank 51 to realize the reflux replenishment of the adsorbent; the fifth water outlet pipe 75 connects the bottom of the third water storage tank 73 and the bottom of the second water storage tank 61 to realize the transport of the adsorbent after desorption. Two fifth solenoid valves are spaced apart on the fourth water outlet pipe 74, and a third water pump is installed between the two fifth solenoid valves. The third water pump drives the cooled pure water in the third water storage tank 73 to flow back to the first water storage tank 51. Two sixth solenoid valves are spaced apart on the fifth water outlet pipe 75, and a fourth water pump is installed between the two sixth solenoid valves. The fourth water pump drives the adsorbent liquid that has completed ammonia removal in the second water storage tank 61 to be transported to the third water storage tank 73. The third water storage tank 73 is internally installed with a second submerged evaporator 72 and externally connected to a third condensing compressor unit 71 to cool and stabilize the reflux adsorption liquid to meet the requirements of the re-adsorption condition. The second water storage tank 61 is equipped with a second liquid level sensor that links the start and stop of the second water pump, and the third water storage tank 73 is equipped with a third liquid level sensor that links the start and stop of the third water pump. The water pumps are automatically controlled by the liquid level signal to achieve unattended closed-loop circulation; the entire adsorption liquid circulation system has no production waste liquid discharged.

[0050] The third condensing compressor unit 71 includes a compressor, a condenser, and a throttling device. The installation and connection methods between the components in the condensing compressor unit are existing technical solutions. The adsorption liquid circulation module 7 establishes a complete closed-loop water system, realizing fully automatic circulation of lean liquid and cooling pure water after desorption, with no production waste liquid discharged externally, completely avoiding pollution from ammonia-containing wastewater. The third condensing compressor unit 71 can pre-cool the return high-temperature adsorption liquid in advance, ensuring that the adsorption liquid returning to the absorption module always meets the low-temperature adsorption conditions, and the ammonia adsorption efficiency will not decrease due to the increase in water temperature. Simultaneously, relying on the three sets of water storage tanks equipped with liquid level sensors, the bottom safety liquid seal level is maintained during the liquid transportation process of all tanks. The third water storage tank 73 is not completely emptied during the pure water replenishment and lean liquid buffering process to prevent the cooled gas in the tank from flowing back to the first water storage tank 51 and the second water storage tank 61, achieving complete isolation of gas in the entire water circuit and completely avoiding the problem of gas crossflow and pollution between water storage tanks at all levels. Moreover, the system automatically completes liquid transportation and replenishment according to the changes in the liquid level in the tanks, realizing unattended, fully automatic closed-loop operation of the water circuit. The pure water loss rate of the entire water circulation system is extremely low, eliminating the need for frequent pure water replenishment, reducing water treatment costs, and ensuring the stable operation of the entire water circuit for ammonia absorption and desorption, supporting the long-term continuous and stable operation of the ammonia recovery system.

[0051] Please refer to the appendix. Figure 4 The gear ring support assembly 27 includes a sleeve post 271 vertically arranged on the upper side of the material plate 22, and multiple support rods 272 for supporting the gear ring are arranged horizontally and spaced around the outer wall of the sleeve post 271.

[0052] This gear ring support assembly 27 adopts a multi-point support structure with cylindrical support rods 272, changing the traditional surface contact support to line contact support, which significantly reduces the contact area between the gear ring and the tooling. On the one hand, it reduces heat conduction between the tooling and the gear ring, avoiding excessive heat dissipation at the support points and the occurrence of nitriding soft spots, thus ensuring the overall uniformity of nitriding of the gear ring. On the other hand, it reduces clamping contact stress, reduces stress deformation during the heat treatment process of the gear ring, further improves the dimensional accuracy of the gear ring machining, and adapts to the production requirements of high-precision and high-speed gear rings. At the same time, the gear ring is easy to disassemble and assemble, and the tooling structure is simple and durable, making it suitable for mass production of gear rings in furnaces.

[0053] Please refer to the appendix. Figure 3 The outer wall of the base shaft 21 opposite to the can cover 12 is fitted with a ring plate 25, and the side of the ring plate 25 opposite to the can cover 12 is provided with a positioning ring 26. The base 23 has a recessed positioning groove for the positioning ring 26 to be inserted.

[0054] By interlocking the ring plate 25, the positioning ring 26, and the positioning groove of the base 23, the lower end of the tooling base shaft 21 is precisely centered and limited, ensuring the coaxiality of the base shaft 21 with the furnace body. This prevents the base shaft 21 from radially shifting or shaking under long-term high-temperature heating and airflow scouring conditions. Consequently, it ensures that the gas outlet angle and gas flow rate of the gas outlet channel 22a on the side wall of each material plate 22 remain consistent, and the ammonia gas disturbance and mixing effect in the furnace remains stable over a long period. This prevents the problem of furnace atmosphere deviation and temperature field unevenness after long-term operation, and improves the long-term operational stability and process consistency of the equipment.

[0055] Please refer to the appendix. Figure 7 The ammonia absorption module 5 further includes a second exhaust pipe 54 connected to the outlet of the air pump 56. The outlet of the second exhaust pipe 54 faces upward, and the outlet of the exhaust pipe is equipped with an electronic igniter that is linked to the air pump 56.

[0056] During the gas nitriding reaction, ammonia is decomposed by heat to produce active nitrogen atoms that penetrate into the surface of the gear ring. The byproducts are hydrogen and unpenetrated nitrogen. Nitrogen does not participate in the reaction and is non-flammable, while hydrogen is a flammable reducing gas. Both are difficult to dissolve in low-temperature adsorption pure water and cannot be captured by the pure water in the ammonia absorption module. After the ammonia-containing tail gas enters the first water storage tank 51 of the ammonia absorption module, the low-temperature atomized pure water selectively absorbs only the ammonia, while nitrogen and hydrogen continuously accumulate in the gas phase space at the top of the water storage tank. The first water storage tank 51 is equipped with a pressure sensor and a gas phase ammonia concentration sensor for coordinated detection. When the pressure inside the tank is higher than the set threshold and the gas phase ammonia concentration is lower than the preset value, the control system automatically opens the third solenoid valve 57 and starts the air pump 56. The air pump 56 extracts the unadsorbed hydrogen and nitrogen mixture from the tank and delivers it to the second exhaust pipe 54. The electronic igniter at the end of the second exhaust pipe 54 is activated simultaneously: the mixture contains trace amounts of residual ammonia, and the hydrogen is burned and decomposed under the action of the electronic igniter; the nitrogen is non-flammable and does not participate in the combustion reaction, and is discharged with the flue gas after combustion in compliance with standards; at the same time, the air pump extracts the gas under positive pressure, which will not cause backfire or explosion.

[0057] This invention also proposes a method for gas nitriding surface modification heat treatment of gearbox speed-increasing gear rings, employing any one of the aforementioned gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus. The method includes the following steps: S1. Tooling clamping and furnace body sealing: The speed-increasing gear rings to be processed are sequentially fitted onto the outer side of the sleeve column 271 of the gear ring special tooling frame 2. Line contact support is achieved by relying on the cylindrical support rod 272. The tank cover 12 is closed to complete the overall sealing of the tank body. The base shaft 21 is centered by the positioning ring 26 cooperating with the positioning groove to ensure the overall coaxiality of the tooling. S2. Furnace preheating and gas distribution nitriding: Start the first heating coil 13 to uniformly heat the side wall of the tank to the nitriding process temperature, open the first solenoid valve 33, and high-purity ammonia gas is sent into the internal airflow channel 21a of the base shaft 21 through the first gas supply pipe 32 and the gas outlet connector 24. Finally, it is radially sprayed out from the gas outlet channel 22a on the side wall of each material plate 22, directly blowing the heated wall of the tank, disturbing the gas stagnant near the wall in the furnace to achieve full-area gas mixing, balancing the temperature field and nitrogen potential field in the furnace, and completing the gas nitriding modification treatment of the gear ring at a constant temperature. S3. Staged pretreatment of exhaust gas: The high-temperature ammonia-containing exhaust gas at 500-550℃ generated by the nitriding reaction is discharged from the exhaust port of the tank cover 12. After being pressurized by the gas booster pump, it is sent into the first drying tube 42. The exhaust gas is cooled to 30-40℃ by the first condenser compressor unit 47 with heat exchange fins. Most of the saturated water vapor is removed by condensation. After passing through the dust filter 44 to intercept solid impurities, it is buffered in the gas buffer tank 43. S4. Low-temperature vacuum adsorption enrichment of concentrated ammonia water: The pure water in the first water storage tank 51 is evacuated to -0.08 to -0.09 MPa in advance to remove dissolved air, and the water temperature in the tank is maintained at 10 to 20°C. The buffered ammonia-containing tail gas is introduced into the first water storage tank 51 and sprayed with pure water through atomizing nozzles to form water mist. The gas and liquid fully contact and adsorb the ammonia in the tail gas to generate concentrated ammonia water with a concentration of 18% to 22%. Relying on multi-sensor linkage control, when the pressure in the tank is over-pressurized and the ammonia concentration reaches the standard, the air inlet is automatically closed and harmless inert gas is discharged. When the concentrated ammonia water is transported, a safety liquid seal level is maintained to prevent air from entering the downstream process. S5. Negative Pressure Low Temperature Desorption and Purification of Ammonia: Before the initial operation, the second water storage tank 61 is evacuated to remove impurities, and no further evacuation is required. The qualified concentrated ammonia water is transported to the second water storage tank 61 and heated to boiling at a constant temperature of 95-105℃ through the second heating coil 64. Ammonia is desorbed autonomously under negative pressure. The desorbed ammonia is discharged in one direction through the top second one-way valve 63. There is no continuous evacuation throughout the process to prevent ammonia escape. The ammonia content of the ammonia water is monitored in real time, and heating is stopped after the desorption meets the standard. S6. Deep drying and pressure stabilization of ammonia gas for reuse: The crude ammonia gas is condensed and dehydrated in the second drying tube 82 and deeply adsorbed by molecular sieve 83. Then, the pressure is regulated by a screw gas compressor to match the pressure of the reused ammonia gas to the gas supply pressure of ammonia tank 31. The purified high-purity ammonia gas with a purity of ≥99.5% is returned to ammonia tank 31 to achieve closed-loop recycling. S7. Closed-loop circulation of adsorbent and harmless treatment of tail gas: The lean liquid after the analysis is completed is transported to the third water storage tank 73 for pre-cooling and cooling. After cooling, the pure water is returned to the first water storage tank 51 for reuse in ammonia adsorption, realizing the whole process of adsorbent circulation without waste liquid discharge; the trace residual ammonia that is not adsorbed is burned and decomposed by electronic igniter and discharged after meeting the standards.

[0058] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A heat treatment apparatus for gas nitriding surface modification of gearbox speed-increasing gear rings, characterized in that, The system includes a sealed furnace body, a dedicated gear ring fixture, a control system, an ammonia supply unit, and an ammonia closed-loop recovery and circulation unit. The sealed furnace body is equipped with a sealable and closable tank and a tank cover. A first heating coil is built into the side wall of the tank body for uniform heating, and an exhaust port is provided in the tank cover. The dedicated gear ring fixture is suspended inside the tank cover and includes a base shaft fixed to the inside of the tank cover and axially aligned with the tank body. Multiple parallel material plates are fixed to the base shaft at intervals from top to bottom. Each material plate is equipped with an independent gear ring support assembly for supporting and positioning the speed-increasing gear ring. A base is fixed at the center of the bottom of the tank body, and an exhaust port is mounted on the base. The furnace has a central shaft; the base axis is recessed inward at the end away from the tank cover to form an axially continuous airflow channel. Multiple air outlet channels connected to the airflow channel are evenly opened around the outer circumference of each material plate to achieve uniform distribution of ammonia gas from bottom to top throughout the furnace. The ammonia supply unit is connected to the bottom of the tank and is used to quantitatively supply high-purity ammonia gas into the furnace. The ammonia closed-loop recovery and circulation unit is connected to the exhaust port of the tank cover and is used to collect ammonia-containing tail gas in the furnace and purify and reuse it to achieve ammonia closed-loop circulation. The control system is electrically connected to all electrical control components and integrates automatic control of the entire process of furnace heating, gas nitriding, tail gas recovery and ammonia reuse.

2. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 1, characterized in that, The sealed furnace body includes a tank with the opening facing upwards and a detachable and sealed tank cover connected to the opening; a first receiving cavity is opened inside the side wall of the tank, and a first heating coil is arranged inside the first receiving cavity to uniformly heat the entire side wall of the tank. The ammonia supply unit includes an ammonia tank for storing high-purity ammonia. The ammonia tank is connected to the bottom of the tank by a first gas supply pipe equipped with a first solenoid valve and sealed to the gas outlet connector.

3. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 1, characterized in that, The ammonia closed-loop recovery and recycling unit includes a tail gas pretreatment module, an ammonia absorption module, an ammonia desorption and purification module, and a drying, stabilizing and recycling module arranged sequentially along the tail gas flow direction. The ammonia closed-loop recovery and recycling unit also includes an adsorption liquid circulation module. After the ammonia-containing tail gas undergoes condensation and dehydration, pure water adsorption and enrichment, negative pressure low-temperature desorption, and deep drying and purification treatment, the high-purity ammonia gas that meets the standards is returned to the ammonia tank.

4. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 3, characterized in that, The exhaust gas pretreatment module includes multiple U-shaped first drying pipes arranged vertically and connected end to end. Each lower bend of the first drying pipe can be detachably fitted with a first water collection bottle for collecting condensed liquid water. Inside the first drying pipe, a first copper tube evaporator is arranged along the gas flow direction. Multiple first heat dissipation fins are uniformly welded to the outer wall of the first copper tube evaporator. The first heat dissipation fins are arranged vertically in parallel, and the extension direction of the fins is in the same direction as the gas flow of the first drying pipe, thereby enhancing the heat exchange and cooling effect. A first condensing compressor unit connected to the first copper tube evaporator is installed outside the first drying pipe. The first drying pipe's inlet end is connected to the exhaust port at the top of the sealed furnace body via a second gas supply pipe; a gas booster pump is installed on the second gas supply pipe; the first drying pipe's outlet end is connected to a dust filter via a third gas supply pipe; the dust filter's outlet end is connected to a gas buffer tank via a fourth gas supply pipe, and a first one-way valve is installed on the fourth gas supply pipe.

5. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 4, characterized in that, The ammonia absorption module includes a fully enclosed pressure-bearing first water storage tank. The first water storage tank is pre-vacuumed to -0.08~-0.09MPa to complete the vacuum degassing treatment. The tank contains vacuum-treated pure water as the ammonia adsorption liquid. The top of the first water storage tank is connected to a gas buffer tank through a fifth gas supply pipe, and a second solenoid valve is installed on the fifth gas supply pipe; a first exhaust pipe is also opened at the top of the first water storage tank, an external air pump is connected to the first exhaust pipe, and a third solenoid valve is installed on the first exhaust pipe. The first water tank has a first water outlet pipe installed through the bottom. The first water outlet pipe is connected in sequence to the first water pump and the multi-way diversion second water outlet pipe. Each second water outlet pipe has an atomizing nozzle installed at the end. Multiple sets of atomizing nozzles are evenly distributed in a ring in the upper cavity of the first water tank. The first water storage tank is equipped with a first submerged evaporator, which is completely submerged below the surface of the adsorbent liquid and is connected to a second condensing compressor unit. The first water storage tank integrates multiple sets of online monitoring sensors: a first liquid level sensor and a first liquid phase ammonia sensor are installed at the bottom of the tank to monitor the liquid level of the adsorbent and the concentration of liquid ammonia in real time, and the infusion process is automatically triggered when the concentration reaches the standard; a gas phase ammonia concentration sensor and a gas pressure sensor are installed at the top of the tank.

6. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 5, characterized in that, The ammonia desorption and purification module includes a second water tank; the top of the second water tank is provided with an upwardly contracting conical gas collecting section, and a gas collecting pipe with one end closed is sealed at the top of the conical gas collecting section, and a second one-way valve is installed through the closed end of the gas collecting pipe; The second water tank is connected to the bottom of the first water tank by a third water outlet pipe. Two fourth solenoid valves are arranged at intervals along the liquid flow direction on the third water outlet pipe. A second water pump is installed in the middle section of the pipe between the two sets of fourth solenoid valves. The second water storage tank has a second receiving cavity formed on its side wall and bottom, and the second receiving cavity is filled with a second heating coil. A second liquid-phase ammonia gas sensor is installed inside the second water storage tank.

7. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 6, characterized in that, The drying, stabilizing, and recycling module includes a second drying tube consisting of multiple vertically arranged U-shaped tubes connected end to end in series, with a second water collection bottle installed at the bend to collect condensed water vapor; the second drying tube is equipped with a second copper tube evaporator and matching second heat dissipation fins, and is externally connected to a fourth condensing compressor unit. The air inlet of the second drying tube is connected to the air outlet of the gas collecting tube through the sixth gas supply tube, and the second one-way valve is built into the air inlet section of the sixth gas supply tube; a molecular sieve for adsorbing water vapor is connected in series on the sixth gas supply tube. The outlet of the second drying pipe is connected to the ammonia tank via the seventh gas supply pipe; the seventh gas supply pipe is sequentially equipped with a screw gas compressor and a third one-way valve along the gas flow direction.

8. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 6, characterized in that, The adsorption liquid circulation module includes a third water storage tank, a fourth water outlet pipe, and a fifth water outlet pipe; The fourth water outlet pipe connects the bottom of the third water storage tank and the bottom of the first water storage tank; the fifth water outlet pipe connects the bottom of the third water storage tank and the bottom of the second water storage tank. Two fifth solenoid valves are spaced apart on the fourth water outlet pipe, and a third water pump is installed between the two fifth solenoid valves. The third water pump drives the cooled pure water in the third water storage tank to flow back to the first water storage tank. Two sixth solenoid valves are spaced apart on the fifth water outlet pipe, and a fourth water pump is installed between the two sixth solenoid valves. The fourth water pump drives the adsorbent liquid that has completed ammonia removal in the second water storage tank to be transported to the third water storage tank. The third water storage tank is internally equipped with a second submerged evaporator and externally connected to a third condensing compressor unit; The second water storage tank is equipped with a second liquid level sensor that is linked to the start and stop of the second water pump, and the third water storage tank is equipped with a third liquid level sensor that is linked to the start and stop of the third water pump.

9. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 1, characterized in that, The gear ring support assembly includes a sleeve column vertically arranged on the upper side of the material plate, and multiple support rods for supporting the gear ring are arranged horizontally and spaced around the outer wall of the sleeve column.

10. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 1, characterized in that, A ring plate is fitted on the outer wall of the end of the base shaft away from the can lid. A positioning insert ring is provided on the side of the ring plate away from the can lid. A positioning groove is formed in the base for the positioning insert ring to be inserted.

11. The gearbox speed-increasing gear ring gas nitriding surface modification heat treatment apparatus according to claim 5, characterized in that, The ammonia absorption module also includes a second exhaust pipe connected to the outlet of the air pump. The outlet of the second exhaust pipe faces upward, and the outlet of the exhaust pipe is equipped with an electronic igniter that is linked to the air pump.

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