A heat treatment combined processing method and equipment for a thread rolling die

Abstract

The application relates to a heat treatment composite processing method and equipment of a thread rolling die, and relates to the technical field of fastener processing, which comprises the following steps: S1, placing a thread rolling die in a heat treatment equipment and vacuumizing; S2, heating the thread rolling die treated in the step S1 to a quenching temperature and keeping warm in a heating period; S3, spraying cooling gas to the thread rolling die treated in the step S2 to make the thread rolling die cool to a nitriding temperature in a gas quenching period; S4, introducing active gas into the heat treatment equipment to carry out nitriding treatment on the thread rolling die treated in the step S3 in a nitriding period; S5, stopping the introduction of the active gas into the heat treatment equipment, and cooling the thread rolling die treated in the step S4 to room temperature; S6, introducing liquid nitrogen to carry out deep cooling treatment on the thread rolling die treated in the step S5 in a deep cooling period; and S7, returning the thread rolling die treated in the step S6 to room temperature. The application has the effect of improving the heat treatment processing efficiency of the thread rolling die.

Description

Technical Field

[0001] This application relates to the field of fastener processing, and in particular to a heat treatment composite processing method and equipment for thread rolling plates. Background Technology

[0002] Thread rolling dies are important molds in the fastener cold forming industry, typically used for rolling threads. The manufacturing quality of thread rolling dies directly affects the forming accuracy and service life of threaded fasteners. Under high-speed impact, thread rolling dies need to possess both extremely high surface wear resistance and good core toughness, thus placing higher demands on the material of the thread rolling die and the heat treatment process during production.

[0003] Currently, traditional thread rolling dies manufacturing generally employs a segmented process: rough machining → vacuum quenching → cryogenic treatment → multiple tempering → precision grinding → nitriding. Each process relies on independent equipment such as vacuum furnaces, cryogenic chambers, tempering furnaces, and nitriding furnaces. Frequent transfers between processes result in workpieces repeatedly undergoing thermal cycles of heating, cooling, and reheating, leading to manufacturing cycles lasting tens of hours and extremely high energy consumption. Conventional nitriding easily creates a hardness abrupt change interface between the bright white layer and the martensitic matrix, which can easily cause peeling and chipping under the impact load of subsequent thread rolling. Moreover, the transfer of thread rolling dies between multiple machines increases the risk of damage, affecting the quality of the dies. The investment and space required for multiple machines are substantial, resulting in high costs.

[0004] In view of the above-mentioned technologies, the inventors believe that there is a need to provide a heat treatment processing method and equipment that improves the convenience of thread rolling plate processing and is more environmentally friendly and energy-saving. Summary of the Invention

[0005] In order to improve the heat treatment processing efficiency of thread rolling dies, this application provides a heat treatment composite processing method and equipment for thread rolling dies.

[0006] In a first aspect, this application provides a heat treatment composite processing method for thread rolling dies, employing the following technical solution: A heat treatment composite processing method for thread rolling dies includes the following steps: S1. Place the thread rolling plate in the heat treatment equipment and evacuate it; S2. During the heating period, heat the thread rolling plate processed in step S1 to the quenching temperature and keep it at that temperature. S3. During the gas quenching period, cooling gas is sprayed onto the thread rolling plate after step S2 to cool the thread rolling plate to the nitriding temperature. S4. During the nitriding period, an active gas is introduced into the heat treatment equipment to perform nitriding treatment on the wire rolling plate after step S3. S5. Stop introducing active gas into the heat treatment equipment and cool the wire rolling plate after step S4 to room temperature. S6. During the cryogenic period, liquid nitrogen is introduced to perform cryogenic treatment on the thread rolling plate after step S5. S7. Bring the wire rolling plate processed in step S6 back to room temperature.

[0007] By adopting the above technical solution, the entire process of heat treatment for thread rolling dies—including vacuuming, heating and quenching, gas quenching and cooling, nitriding, cryogenic treatment, and rewarming to room temperature—is completed sequentially within the same equipment. This reduces the frequent transfer of thread rolling dies between independent equipment and the repeated heating and cooling cycles in traditional step-by-step processes, shortens the heat treatment cycle of thread rolling dies, improves convenience, and reduces energy consumption. At the same time, since nitriding is performed directly after gas quenching, the residual heat of the thread rolling die can be used to assist the nitriding process, improving nitriding efficiency and achieving better heat treatment results.

[0008] Optionally, the cooling gas in step S3 is sprayed onto the surface of the thread rolling plate at a pressure of 5 to 20 bar, and the cooling rate of the thread rolling plate surface is 3 to 5 °C per second.

[0009] By employing the above technical solution, cooling gas is sprayed onto the surface of the thread rolling die at a pressure of 5 to 20 bar, and gas quenching is performed at a cooling rate of 3 to 5 °C / s. This results in a more uniform martensitic structure and improves the overall structural strength of the thread rolling die. Simultaneously, the high cooling rate generates higher compressive stress on the surface of the thread rolling die, which is beneficial for improving its fatigue resistance.

[0010] Optionally, the cooling gas in step S3 is nitrogen, and the injection direction is uniformly distributed along the surface of the thread rolling plate; nitrogen is continued to be introduced so that the thread rolling plate is in a nitrogen atmosphere; after the gas quenching period in step S3 ends, the nitrogen atmosphere is maintained as the protective atmosphere for the subsequent step S4.

[0011] By adopting the above technical solution, using nitrogen as the cooling gas and ensuring the spray direction is evenly distributed along the surface of the thread rolling plate, a more uniform cooling effect can be achieved in all parts of the thread rolling plate, reducing the risk of quenching deformation and cracking. After gas quenching, maintaining a nitrogen atmosphere as a protective atmosphere for subsequent nitriding treatment reduces the possibility of surface oxidation caused by contact with oxygen during process transitions, thus improving the quality and uniformity of the nitrided layer.

[0012] Optionally, the active gas in step S4 is a gas containing active nitrogen particles formed after the decomposition of an ammonia atmosphere; the nitriding treatment involves the active particles reacting with the surface of the filament rolling plate to form a nitrided layer, which is then maintained at a certain temperature for a period of time.

[0013] By adopting the above technical solution, active nitrogen particles generated from the decomposition of ammonia atmosphere are used for nitriding treatment. These active nitrogen particles have high chemical activity and can react with the surface of the thread rolling die at a relatively low temperature to form a nitrided layer. Compared with traditional ion nitriding or gas nitriding methods that rely on concentration gradient diffusion, this method achieves better nitriding results. Since the nitriding process is completed continuously within the same thermal cycle as the quenching and cryogenic processes, a hardness gradient transition layer can be formed between the nitrided layer and the substrate. This reduces the abrupt hardness change interface between the bright white layer and the martensitic matrix in traditional processes, lowering the risk of surface peeling and thread breakage under impact loads.

[0014] Optionally, the cryogenic treatment in step S6 involves stopping the flow of active gas, drawing a vacuum, and introducing liquid nitrogen to lower the temperature of the wire rolling plate to -190 to -200 °C and holding it at that temperature for 20 to 40 minutes.

[0015] By adopting the above technical solution, the temperature of cryogenic treatment is controlled at -190 to -200℃ and held for 20 to 40 minutes, which can promote the full transformation of residual austenite inside the thread rolling plate into martensite, further improve the hardness and dimensional stability of the thread rolling plate, help eliminate residual stress inside the thread rolling plate, and improve the impact toughness of the thread rolling plate.

[0016] Optionally, after step S7, a low-temperature tempering step is further included after the thread rolling plate has naturally cooled to room temperature, wherein the low-temperature tempering temperature is 150 to 200°C.

[0017] By adopting the above technical solution, after cryogenic treatment and warming to room temperature, a low-temperature tempering at 150 to 200°C can be performed, which can improve the stress relief effect inside the thread rolling plate, strengthen the maintenance of the high hardness of the thread rolling plate surface, and improve the overall toughness and impact resistance of the thread rolling plate.

[0018] Secondly, this application provides a heat treatment composite processing equipment for thread rolling plates, which adopts the following technical solution: A heat treatment composite processing equipment for thread rolling dies, used to realize the above-mentioned heat treatment composite processing method for thread rolling dies, includes a main body of the equipment, a heating module and a gas regulation module disposed in the main body of the equipment, and a control module electrically connected to both the heating module and the gas regulation module; the main body of the equipment has a heat treatment chamber; the main body of the equipment also includes a support base disposed in the heat treatment chamber for fixing the thread rolling die.

[0019] By adopting the above technical solution, the heating module, gas regulation module and control module are integrated into the same equipment body, and the thread rolling plate is fixed in the support base in the heat treatment chamber. This allows the quenching, nitriding and deep cooling processes of the thread rolling plate to be completed continuously in the same chamber without the need to transfer the thread rolling plate between different equipment. The equipment has a small footprint, low investment cost and is easier to operate.

[0020] Optionally, the heating module includes an induction heating unit and a temperature measuring element; the induction heating unit is arranged around the thread rolling plate on the support base; the temperature measuring element is electrically connected to the control module and is used to monitor the temperature of the thread rolling plate in real time and feed it back to the control module to adjust the output power of the induction heating unit.

[0021] By adopting the above technical solution, setting the induction heating unit around the thread rolling plate and cooperating with the temperature measuring element to provide real-time temperature feedback to the control module, the thread rolling plate can be precisely closed-loop temperature controlled, which improves the uniformity of heating and the accuracy of temperature control, reduces the probability of overheating or underheating of the thread rolling plate, and thus improves the heat treatment quality of the thread rolling plate.

[0022] Optionally, the gas regulation module includes a gas quenching control system; the gas quenching control system includes a gas injection assembly disposed in the heat treatment chamber, a gas injection pipe connected to the gas injection assembly, and a first gas supply source for supplying gas to the gas injection assembly; the gas injection assembly has a gas injection port arranged toward the surface of the thread rolling plate; the gas injection pipe is provided with a switch control valve electrically connected to the control module.

[0023] By adopting the above technical solution, the gas injection assembly installed in the heat treatment chamber has a gas nozzle arranged towards the surface of the thread rolling plate. In conjunction with the gas injection pipe connected to the first gas supply source and the switch control valve electrically connected to the control module, it is possible to achieve rapid and uniform gas quenching cooling of the thread rolling plate. The switch control valve makes the cooling rate of the thread rolling plate controllable, thereby improving the quenching effect and the stability of product quality.

[0024] Optionally, the gas regulation module includes a nitriding control system; the nitriding control system includes a second gas supply source, a third gas supply source, gas supply pipelines respectively connected to the second gas supply source and the third gas supply source, a flow regulation component installed on the gas supply pipeline for controlling the flow rate, and a homogenizing fan installed on the main body of the equipment; the gas supply pipeline has an outlet located in the heat treatment chamber, and the outlets are respectively arranged around the circumference of the thread rolling plate.

[0025] By adopting the above technical solution, a second and third air supply source are set up, and the air supply pipelines and flow regulation components connected to the second and third air supply sources respectively can control the timing and flow rate of the atmosphere introduction, meeting the different atmosphere requirements of different process stages. The homogenizing fan can homogenize the gas in the heat treatment chamber, improving the heat treatment effect and operational safety of the equipment.

[0026] In summary, this application includes at least one of the following beneficial technical effects: A composite heat treatment process for thread rolling dies integrates the entire process of vacuuming, heating and quenching, gas quenching and cooling, nitriding, cooling to room temperature, cryogenic treatment, and reheating to room temperature into a single heat treatment device for continuous completion. This allows the thread rolling die to complete quenching, nitriding, and cryogenic treatment sequentially in a single thermal cycle, reducing the frequent transfer of the thread rolling die between independent devices and the repeated heating and cooling thermal cycles required in traditional segmented processes. This improves processing efficiency and reduces energy consumption. Furthermore, since the nitriding treatment is performed directly after gas quenching, the residual heat of the thread rolling die can be used to assist the nitriding process, mitigating the hardness abrupt change problem between the traditional nitrided white layer and the martensitic matrix. This reduces the risk of peeling and chipping of the lower surface layer of the thread rolling die, thus improving the quality of the thread rolling die. By spraying cooling gas onto the surface of the thread rolling plate at a pressure of 5 to 20 bar and a cooling rate of 3 to 5 °C / s during the gas quenching stage, and with the spray direction evenly distributed along the surface of the thread rolling plate, the overall structural strength and fatigue resistance of the thread rolling plate are improved. By cooling the thread rolling plate to -190 to -200 °C and holding it at that temperature for 20 to 40 minutes for deep cryogenic treatment, the residual austenite inside the thread rolling plate is fully transformed into martensite, which further improves the hardness and dimensional stability of the thread rolling plate. Combined with low-temperature tempering at 150 to 200 °C after deep cryogenic treatment, the quenching and deep cryogenic stress are eliminated while maintaining high surface hardness, which is conducive to the thread rolling plate having both high surface wear resistance and excellent internal impact toughness. A heat treatment composite processing equipment for thread rolling dies integrates a heating module, a gas regulation module, and a control module into the same main body of the equipment, and sets up a support base in the heat treatment chamber to fix the thread rolling die. This allows the quenching, nitriding, and deep cooling processes of the thread rolling die to be completed continuously in the same chamber without the need to transfer the thread rolling die between different equipment. This reduces the risk of bumps and knocks during transportation, improves the production quality of heat treatment of thread rolling dies, and the equipment has a small footprint, low investment cost, and is easier to operate, thus reducing production costs. By arranging the induction heating unit of the heating module around the thread rolling plate on the support base and cooperating with the temperature sensing element to provide real-time temperature feedback to the control module to achieve closed-loop temperature control, the temperature of the thread rolling plate can be monitored, which is beneficial to the uniformity of the thread rolling plate heating. By setting up a gas quenching control system with jet nozzles, rapid and uniform gas quenching cooling of the thread rolling plate can be achieved, making the cooling rate more controllable. By setting up gas supply pipelines and flow regulation components connected to the second and third gas supply sources, the atmosphere ratio, timing of introduction and flow rate can be controlled to meet the different atmosphere requirements of each treatment stage of quenching, nitriding and deep cryogenic treatment. At the same time, the homogenizing fan ensures uniform gas distribution in the heat treatment chamber, improving the stability and consistency of heat treatment quality. Attached Figure Description

[0027] Figure 1This is a schematic diagram of the heat treatment composite processing equipment for the thread rolling plate in the embodiments of this application.

[0028] Figure 2 This is a schematic diagram of the heating module in an embodiment of this application.

[0029] Figure 3 This is a schematic diagram of the structure of the support base in the embodiments of this application.

[0030] Figure 4 This is a schematic diagram of the gas regulation module in an embodiment of this application.

[0031] Explanation of reference numerals in the attached drawings: 1. Main body of equipment; 11. Heat treatment tank; 12. Sealing door; 13. Vacuum pump group; 14. Support base; 141. Base frame; 1411. Limiting groove; 142. Limiting plate; 15. Homogenizing fan; 2. Heating module; 21. Induction heating unit; 211. Induction coil; 22. Temperature measuring element; 3. Gas regulation module; 31. Gas quenching control system; 311. Gas injection assembly; 3111. Ring pipe; 3112. Jet nozzle; 312. Jet pipe; 32. Nitriding control system; 321. Ammonia decomposition device; 322. Gas transmission pipeline; 3221. First gas transmission pipe; 3222. Second gas transmission pipe; 323. Flow regulation assembly; 4. Control module; 5. Tail gas treatment device. Detailed Implementation

[0032] The following is in conjunction with the appendix Figure 1-4 This application will be described in further detail.

[0033] This application discloses a heat treatment composite processing equipment for thread rolling dies. (Refer to...) Figure 1 and Figure 2 A heat treatment composite processing equipment for wire rolling plates includes a main body 1, a heating module 2 and a gas regulation module 3 disposed on the main body 1, and a control module 4 electrically connected to both the heating module 2 and the gas regulation module 3.

[0034] Reference Figure 1 and Figure 2The main body 1 is a horizontal stainless steel shell structure, with a heat treatment tank 11 inside, containing a sealed heat treatment chamber. The main body 1 is equipped with an openable sealing door 12 for easy insertion and removal of the thread rolling plate. The walls of the main body 1 are provided with a water-cooled jacket, through which circulating cooling water is supplied to cool the chamber walls during operation, protecting the main body 1 and maintaining a stable temperature within the heat treatment chamber. The main body 1 is connected to a vacuum pump group 13, preferably including a mechanical pump and a Roots pump, for evacuating the heat treatment chamber. The main body 1 is also equipped with a pressure sensor for real-time monitoring of the chamber pressure, and a safety relief valve that automatically opens to release pressure when the chamber pressure exceeds a set threshold, ensuring safe operation of the equipment.

[0035] Reference Figure 2 and Figure 3 The main body 1 of the equipment also includes a support base 14 disposed within the heat treatment chamber for fixing the thread rolling plate. The support base 14 includes base frames 141 spaced apart and installed on the inner wall of the main body 1, and a limiting plate 142 detachably installed on the top of the base frames 141. The base frames 141 have limiting grooves 1411 for inserting the limiting plates 142. Multiple limiting grooves 1411 are provided along the length of the base frames 141 to adjust the insertion of the limiting plates 142 according to different thread rolling plate shapes. In use, the thread rolling plate is inserted into the heat treatment chamber, with one end abutting against the limiting plate 142 and the bottom against the top of the base frames 141, thus supporting the thread rolling plate. In this application, the number of base frames 141 is three.

[0036] Reference Figure 1 and Figure 4 Heating module 2 is used to heat the thread rolling plate. Heating module 2 includes an induction heating unit 21 and a temperature sensing element 22. The induction heating unit 21 consists of an induction coil 211 and a power supply electrically connected to the induction coil 211. The induction coil 211 surrounds the heat treatment tank 11, thus heating the thread rolling plate on the support base 14. When energized, the induction coil 211 generates an electromagnetic field, thereby heating the thread rolling plate. The temperature sensing element 22 is an infrared thermometer, positioned to accurately detect the surface temperature of the thread rolling plate. The infrared thermometer is electrically connected to the control module 4, used to monitor the thread rolling plate temperature in real time and feed the temperature signal back to the control module 4. The control module 4 adjusts the output power of the induction heating unit 21 in real time based on the deviation between the feedback signal and the set temperature, thereby controlling the heating temperature of the thread rolling plate.

[0037] Reference Figure 3 and Figure 4The gas regulating module 3 is used to supply different types of gases to the heat treatment chamber and control the gas flow rate. The gas regulating module 3 includes a gas quenching control system 31. The gas quenching control system 31 includes a first gas supply source, a gas injection assembly 311, a jet pipe 312, and a switch control valve. The first gas supply source is preferably a high-pressure nitrogen storage tank, which stores high-pressure, high-purity nitrogen. The gas injection assembly 311 is disposed within the heat treatment chamber and has an annular tubular structure, including an annular pipe 3111 and jet heads 3112 spaced apart on the pipe wall of the annular pipe 3111. The outer peripheral wall of the annular pipe 3111 abuts against the inner wall of the heat treatment tank 11. The jet heads 3112 have jet nozzles arranged towards the surface of the thread rolling plate, and the jet nozzles are evenly arranged along the surface of the thread rolling plate so that the cooling gas can be evenly injected onto the surface of the thread rolling plate. The jet pipe 312 connects the first gas supply source and the gas injection assembly 311 for transporting nitrogen. The switch control valve is located on the jet pipe 312, preferably a fast-response solenoid valve, and is electrically connected to the control module 4. It is used to quickly open or close according to the control command during the gas quenching period to control the timing and duration of high-pressure nitrogen injection.

[0038] Reference Figure 3 and Figure 4 The gas regulation module 3 also includes a nitriding control system 32. The nitriding control system 32 includes a second gas source, a third gas source, an ammonia decomposition device 321, a gas transmission pipeline 322, and a flow regulation component 323. The second gas source is preferably a high-purity nitrogen source, and the third gas source is preferably an ammonia source. The ammonia source is connected to the ammonia decomposition device 321 via the gas transmission pipeline 322. The ammonia decomposition device 321 is preferably a catalytic decomposition device, containing a catalyst for decomposing ammonia into active nitrogen particles and hydrogen. The gas transmission pipeline 322 has a first gas transmission pipe 3221 for transporting active nitrogen particles and a second gas transmission pipe 3222 for transporting hydrogen. The decomposed mixed gas is separated, and the active nitrogen particles enter the heat treatment chamber through the first gas transmission pipe 3221. A flow regulation component 323 is installed on the gas transmission pipeline 322, and the flow regulation component 323 has multiple flow controllers and multiple channel control capabilities. The flow regulating component 323 is electrically connected to the control module 4 and is used to control the flow rate of nitrogen and ammonia. The gas supply pipeline 322 has an outlet located within the heat treatment chamber. The outlet is arranged in a ring-shaped gas distribution pipeline around the thread rolling plate, with multiple outlets facing the thread rolling plate to achieve uniform atmosphere distribution. In this embodiment, to facilitate monitoring of the gas flow rate, the jet pipe 312 is also connected to the flow regulating component 323 for unified monitoring and management.

[0039] Reference Figure 1 and Figure 3The main body 1 of the equipment is also equipped with a tail gas treatment device 5. The inlet of the tail gas treatment device 5 is connected to the exhaust port of the heat treatment chamber, and it is also connected to the hydrogen outlet of the ammonia decomposition device 321 through a second gas supply pipe 3222. This is used for the combustion treatment of hydrogen and the absorption treatment of waste gas in the heat treatment chamber, reducing harmful gas emissions and improving equipment safety. The main body 1 of the equipment is also equipped with a homogenizing fan 15, which is driven by a servo motor. During operation, the homogenizing fan promotes gas flow within the heat treatment chamber, making the temperature field and atmosphere concentration field within the chamber more uniform, further improving the uniformity and consistency of the heat treatment.

[0040] This application discloses a heat treatment composite processing method for thread rolling dies, implemented using the aforementioned heat treatment composite processing equipment for thread rolling dies. Combined with... Figures 1 to 4 A heat treatment composite processing method for a thread rolling die includes the following steps: S1. Place the thread rolling dies in the heat treatment equipment and evacuate the chamber. Place the thread rolling die blank to be treated in the heat treatment chamber of the heat treatment equipment and fix the thread rolling die with the support base 14. After closing the sealing door 12 of the heat treatment chamber, the control module 4 starts the vacuum pump group 13 to evacuate the heat treatment chamber to remove air from the chamber and prevent surface oxidation of the thread rolling die during subsequent heating. The vacuum level is controlled according to actual needs. During this process, the pressure sensor monitors the pressure in the chamber in real time and feeds the signal back to the control module 4.

[0041] S2. During the heating period, the thread rolling plate processed in step S1 is heated to the quenching temperature and held at that temperature. After vacuuming is completed, the heating stage begins. Control module 4 activates the induction heating unit 21 of heating module 2 to heat the thread rolling plate, thereby heating it to the quenching temperature. The quenching temperature is determined according to the material of the thread rolling plate. During the heating process, an infrared thermometer monitors the surface temperature of the thread rolling plate in real time and feeds the temperature signal back to control module 4. Control module 4 adjusts the output power of induction heating unit 21 in real time according to the deviation between the feedback signal and the set quenching temperature, forming a closed-loop control to ensure that the thread rolling plate is accurately heated to the target quenching temperature. After the quenching temperature is reached, control module 4 controls induction heating unit 21 to maintain the temperature at a lower power. The holding time is usually 1 to 2 minutes, preferably 2 minutes, to allow the internal structure of the thread rolling plate to be fully austenitized.

[0042] S3. After the heat preservation period, the gas quenching stage begins. During the gas quenching period, the control module 4 shuts down the induction heating unit 21 and simultaneously opens the switch control valve of the gas quenching control system 31. High-pressure, high-purity nitrogen from the first gas supply source is delivered to the gas injection assembly 311 in the heat treatment chamber via the jet pipe 312. The gas is then injected onto the surface of the thread rolling plate from jet nozzles evenly distributed towards the surface of the thread rolling plate, ensuring uniform cooling of all parts of the thread rolling plate, reducing the risk of quenching deformation and cracking, and cooling the thread rolling plate to the nitriding temperature. Preferably, the cooling gas is injected onto the surface of the thread rolling plate at a pressure of 5 bar to 20 bar, preferably 20 bar. The high-speed flowing nitrogen carries away the heat from the thread rolling plate, causing it to cool to the nitriding temperature at a cooling rate of 3 to 5 °C / second, preferably 4 °C / second. The higher cooling rate can suppress grain growth, resulting in a fine and uniform martensitic structure on the thread rolling plate. At the same time, the surface of the thread rolling plate receives higher residual compressive stress, which is beneficial for improving fatigue resistance. After the gas quenching period in step S3 ends, nitrogen gas is continued to be introduced to keep the thread rolling plate in a nitrogen atmosphere, reducing the possibility of oxidation on the surface of the thread rolling plate and maintaining the nitrogen atmosphere as a protective atmosphere for the subsequent step S4.

[0043] S4. During the nitriding period, active gas is introduced into the heat treatment equipment to nitrid the thread rolling plate after step S3. Control module 4 switches the nitrogen injection channel of gas quenching control system 31 to a low flow rate to maintain a protective atmosphere and turns on nitriding control system 32. Ammonia from the third gas supply source is transported to ammonia decomposition device 321 via gas pipeline 322. In ammonia decomposition device 321, ammonia is catalytically decomposed to generate active nitrogen particles and hydrogen. After separation, the active nitrogen particles are precisely metered via first gas pipeline 3221 and flow regulating component 323 and transported to the heat treatment chamber via annular gas distribution pipeline, and evenly released from the outlets distributed around the thread rolling plate. Active nitrogen particles can be adsorbed, enriched and react with iron on the surface of the thread rolling plate to form a nitrided layer. The hydrogen produced by decomposition is directly transported to tail gas treatment device 5 via second gas pipeline 3222 for combustion treatment, reducing the risk of hydrogen entering the heat treatment chamber or accumulating in the equipment.

[0044] The control module 4 precisely controls the flow rate and pressure of the active nitrogen particles through the flow regulation component 323. Simultaneously, it can activate a second gas supply source to introduce nitrogen gas as needed to adjust the atmosphere composition and partial pressure within the chamber. The nitriding treatment is maintained for a holding period, the length of which is determined based on the required nitriding layer depth, generally 15 to 30 minutes, preferably 30 minutes. The deeper the nitriding layer required, the longer the holding period should be.

[0045] The homogenizing fan 15 operates during the nitriding period, promoting gas flow within the heat treatment chamber and ensuring a uniform distribution of active nitrogen particles around the thread rolling plate, which is beneficial for the uniformity of the nitrided layer formation. Since the nitriding process is performed directly after gas quenching, the thread rolling plate retains residual heat, which can be used to assist atomic diffusion during the nitriding process, improving nitriding efficiency. Because quenching and nitriding are completed continuously within the same thermal cycle, a hardness gradient transition layer can be formed between the nitrided layer and the martensitic matrix, alleviating the abrupt hardness interface problem between the bright white layer and the martensitic matrix in traditional processes.

[0046] S5. Cool the thread rolling plate processed in step S4 to room temperature. After the nitriding process is completed, control module 4 shuts off the nitrogen supply from the second gas source and the ammonia supply from the third gas source. The thread rolling plate continues to cool to room temperature under a nitrogen protective atmosphere. In this embodiment, this process is natural cooling.

[0047] S6. After the thread rolling plate cools to room temperature, it enters the cryogenic treatment stage. During the cryogenic period, vacuum pump unit 13 is activated to evacuate the heat treatment chamber to remove residual gas. Control module 4 opens the liquid nitrogen supply valve to introduce liquid nitrogen into the heat treatment chamber. The liquid nitrogen vaporizes in the heat treatment chamber and absorbs a large amount of heat, causing the temperature in the heat treatment chamber to drop to -190℃ to -200℃, preferably -200℃. The thread rolling plate is kept at this low temperature for 20 to 40 minutes, preferably 40 minutes. The length of the holding period is adjusted and controlled by control module 4 according to requirements. The residual austenite inside the thread rolling plate further transforms into martensite, improving the hardness and wear resistance of the thread rolling plate and eliminating residual stress.

[0048] S7. The thread rolling plate processed in step S6 is brought back to room temperature. After the heat treatment is completed, control module 4 closes the liquid nitrogen supply valve, stopping the flow of liquid nitrogen. Control module 4 then introduces air into the heat treatment chamber through gas regulation module 3, allowing the thread rolling plate to gradually return to room temperature. During the temperature recovery process, control module 4 adjusts the air flow rate to control the heating rate, reducing the risk of deformation or cracking of the thread rolling plate due to thermal stress caused by excessive temperature differences.

[0049] After the thread rolling plate naturally warms to room temperature, it can be subjected to low-temperature tempering treatment as needed. The low-temperature tempering temperature is 150℃ to 200℃, preferably 200℃. Control module 4 activates induction heating unit 21 to heat the thread rolling plate to 200℃. After holding at this temperature for a certain period of time, induction heating unit 21 is turned off, and nitrogen or air is introduced to cool the thread rolling plate to room temperature. Low-temperature tempering can further eliminate the quenching stress and cryogenic stress inside the thread rolling plate, improving the overall toughness and impact resistance of the thread rolling plate.

[0050] Combination Figures 1 to 4The implementation principle of the heat treatment composite processing method and equipment for a thread rolling plate according to an embodiment of this application is as follows: First, the thread rolling plate is transferred to the heat treatment chamber and placed on the support base 14; after the sealing door 12 is closed, the control module 4 starts the vacuum pump group 13 to evacuate the vacuum. Then, the control module 4 controls the induction coil 211 of the induction heating unit 21 to be energized to heat and keep the thread rolling plate at a certain temperature. During this period, the infrared thermometer feeds back the temperature to the control module 4 in real time for monitoring. After the heat preservation is completed, the gas quenching stage begins: the control module 4 opens the switch control valve, and the nitrogen in the first gas supply source is transported to the annular pipe 3111 through the jet pipe 312. The nitrogen is then sprayed onto the surface of the thread rolling plate at a pressure of 20 bar through the jet nozzle, rapidly cooling it to the nitriding temperature and maintaining the nitrogen protective atmosphere. Following this, nitriding is performed: ammonia gas is catalytically decomposed into active nitrogen particles and hydrogen by the ammonia decomposition device 321. The hydrogen is then transported to the tail gas treatment device 5 for combustion. The active nitrogen particles, metered by the flow regulating component 323, are introduced into the heat treatment chamber through the annular gas distribution pipe, forming a nitrided layer on the surface of the thread rolling plate. Simultaneously, the homogenizing fan 15 operates to ensure a uniform atmosphere. After nitriding, the plate is cooled to room temperature, then evacuated, and then subjected to deep cryogenic treatment at -200°C using liquid nitrogen, held at this temperature for 40 minutes. Finally, air is introduced to restore the temperature to room temperature, followed by low-temperature tempering at 200°C, achieving efficient and continuous heat treatment of the thread rolling plate.

[0051] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A heat treatment composite processing method for thread rolling dies, wherein heat treatment is performed in the same equipment, characterized in that, Includes the following steps: S1. Place the thread rolling plate in the heat treatment equipment and evacuate it; S2. During the heating period, heat the thread rolling plate processed in step S1 to the quenching temperature and keep it at that temperature. S3. During the gas quenching period, cooling gas is sprayed onto the thread rolling plate after step S2 to cool the thread rolling plate to the nitriding temperature. S4. During the nitriding period, an active gas is introduced into the heat treatment equipment to perform nitriding treatment on the wire rolling plate after step S3. S5. Stop introducing active gas into the heat treatment equipment and cool the wire rolling plate after step S4 to room temperature. S6. During the cryogenic period, liquid nitrogen is introduced to perform cryogenic treatment on the thread rolling plate after step S5. S7. Bring the wire rolling plate processed in step S6 back to room temperature.

2. The heat treatment composite processing method for a thread rolling plate according to claim 1, characterized in that, In step S3, the cooling gas is sprayed onto the surface of the thread rolling plate at a pressure of 5 to 20 bar, and the cooling rate of the thread rolling plate surface is 3 to 5 °C per second.

3. The heat treatment composite processing method for a thread rolling plate according to claim 2, characterized in that, The cooling gas in step S3 is nitrogen, and the spray direction is evenly distributed along the surface of the thread rolling plate; nitrogen is continued to be introduced so that the thread rolling plate is in a nitrogen atmosphere; after the gas quenching period in step S3 ends, the nitrogen atmosphere is maintained as the protective atmosphere for the subsequent step S4.

4. The heat treatment composite processing method for a thread rolling plate according to claim 1, characterized in that, The active gas mentioned in step S4 is a gas containing active nitrogen particles formed after the decomposition of an ammonia atmosphere; the nitriding treatment is the reaction of the active particles with the surface of the filament rolling plate to form a nitrided layer, which is then maintained at a certain temperature for a period of time.

5. The heat treatment composite processing method for a thread rolling plate according to claim 1, characterized in that, The cryogenic treatment described in step S6 involves stopping the flow of active gas, drawing a vacuum, and introducing liquid nitrogen to lower the temperature of the wire rolling plate to -190 to -200°C and holding it at that temperature for 20 to 40 minutes.

6. The heat treatment composite processing method for a thread rolling plate according to claim 1, characterized in that, After step S7, the process further includes a low-temperature tempering step after the wire rolling plate has naturally cooled to room temperature, wherein the low-temperature tempering temperature is 150 to 200°C.

7. A heat treatment composite processing equipment for thread rolling plates, characterized in that, The method for heat treatment composite processing of the thread rolling plate according to any one of claims 1-6 includes a main body (1), a heating module (2) disposed in the main body (1), a gas regulating module (3) disposed in the main body (1), and a control module (4) electrically connected to both the heating module (2) and the gas regulating module (3); the main body (1) has a heat treatment chamber; the main body (1) further includes a support base (14) disposed in the heat treatment chamber and used to fix the thread rolling plate.

8. The heat treatment composite processing equipment for a thread rolling plate according to claim 7, characterized in that, The heating module (2) includes an induction heating unit (21) and a temperature measuring element (22); the induction heating unit (21) is arranged around the thread rolling plate on the support base (14); the temperature measuring element (22) is electrically connected to the control module (4) and is used to monitor the temperature of the thread rolling plate in real time and feed it back to the control module (4) to adjust the output power of the induction heating unit (21).

9. The heat treatment composite processing equipment for a thread rolling plate according to claim 7, characterized in that, The gas regulation module (3) includes a gas quenching control system (31); the gas quenching control system (31) includes a gas injection assembly (311) disposed in the heat treatment chamber, a jet pipe (312) connected to the gas injection assembly (311), and a first gas supply source for supplying gas to the gas injection assembly (311); the gas injection assembly (311) has a jet nozzle arranged toward the surface of the thread rolling plate; the jet pipe (312) is provided with a switch control valve electrically connected to the control module (4).

10. The heat treatment composite processing equipment for a thread rolling plate according to claim 7, characterized in that, The gas regulation module (3) includes a nitriding control system (32); the nitriding control system (32) includes a second gas supply source, a third gas supply source, a gas transmission pipeline (322) connected to the second gas supply source and the third gas supply source respectively, a flow regulation component (323) installed on the gas transmission pipeline (322) for controlling the flow rate, and a homogenizing fan (15) installed on the main body of the equipment (1); the gas transmission pipeline (322) has an outlet located in the heat treatment chamber, and the outlets are respectively arranged around the circumference of the thread rolling plate.

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