Nitrogen protection heat treatment process and system suitable for iron-nickel alloy parts

Abstract

The application discloses a nitrogen protection heat treatment process and system suitable for iron-nickel alloy parts, relates to the technical field of heat treatment, and comprises the following steps: S1, feeding and nitrogen replacement; S2, preheating; S3, heating; and S4, cooling; wherein, in the continuous furnace formed by the preheating section, the heating furnace and the water cooling section, by controlling the nitrogen flow distribution, the nitrogen flow of the heating furnace region is greater than that of the inlet of the preheating section and the outlet region of the water cooling section, the continuous nitrogen flow is used to form a positive pressure in the furnace, air is driven away from the feeding port and the discharging port of the furnace, the furnace is ensured to be filled with nitrogen, and the iron-nickel alloy parts are limited to be oxidized in a physical isolation mode; and the workpiece temperature at the outlet of the curtain air cooling section is controlled to be lower than the oxidation temperature of the workpiece. The application can improve the heat treatment effect of the iron-nickel alloy parts.

Description

Technical Field

[0001] This application relates to the technical field of heat treatment, and in particular to a nitrogen-protected heat treatment process and system suitable for iron-nickel alloy parts. Background Technology

[0002] Iron-nickel alloy parts are metallic alloy materials with iron and nickel as the main components. By adjusting the nickel content, they can possess excellent soft magnetic properties, a low coefficient of thermal expansion, and good corrosion resistance and mechanical strength. In today's industrial fields, industries such as precision electronic components, aerospace structural parts, and high-precision instrument manufacturing are constantly developing, and the requirements for material properties are becoming increasingly stringent. Iron-nickel alloy parts, with their unique performance advantages, have been widely used in these fields. Their final performance is highly dependent on the heat treatment process. A suitable heat treatment process can optimize their microstructure and macroscopic properties, meeting the stringent requirements of different industrial applications. Therefore, heat treatment technology for iron-nickel alloy parts is of great significance for promoting the development of related industries.

[0003] In existing technologies, protective atmospheres are commonly used to address issues such as oxidation, decarburization, or nitriding of iron-nickel alloy parts during heat treatment. Ammonia decomposition atmosphere is a traditional protective gas solution. This process involves introducing ammonia gas into a decomposition furnace containing a catalyst, where the ammonia gas decomposes into a mixture of hydrogen and nitrogen at high temperatures. This mixture is then introduced into the heat treatment furnace to create a reducing environment. This reducing environment can remove oxides from the workpiece surface, maintain the chemical stability of the workpiece during heating and cooling, and thus ensure the surface finish, compositional uniformity, and functional consistency of the alloy parts. While other protective gas solutions may exist besides ammonia decomposition atmosphere, it is a commonly used one.

[0004] However, using ammonia decomposition as a protective gas has several drawbacks. First, the process is costly; ammonia is an expensive chemical raw material, the decomposition equipment requires continuous energy consumption and maintenance, and the storage and transportation of ammonia also incur additional expenses. Second, hydrogen, a product of ammonia decomposition, is a highly flammable and explosive gas. During heat treatment, improper control of hydrogen concentration or leakage can easily lead to fires or explosions, posing a serious threat to production safety. Furthermore, the strong reducing properties of hydrogen can cause excessive reduction reactions on the surface of iron-nickel alloy parts, inducing hydrogen embrittlement and reducing their toughness. Simultaneously, the instability of nitrogen partial pressure in the mixed gas can disrupt the redox balance, causing surface micro-defects or component segregation, ultimately affecting the mechanical properties, electromagnetic characteristics, and batch consistency of the product. Summary of the Invention

[0005] To improve the heat treatment effect of iron-nickel alloy parts, this application provides a nitrogen-protected heat treatment process and system suitable for iron-nickel alloy parts.

[0006] In a first aspect, this application provides a nitrogen-protected heat treatment process suitable for iron-nickel alloy parts, employing the following technical solution:

[0007] A nitrogen-protected heat treatment process suitable for iron-nickel alloy parts includes the following steps:

[0008] S1. Loading and nitrogen replacement: The iron-nickel alloy parts are loaded into a semi-sealed material box. The semi-sealed material box is placed at the loading station, and nitrogen is introduced into the semi-sealed material box to replace and remove the air inside the box.

[0009] S2. Preheating: The semi-sealed material box that has completed nitrogen purging is sent into the preheating section, and nitrogen is introduced into the heat treatment furnace.

[0010] S3. Heating: The semi-sealed material box is sent into a heating furnace for heat treatment, and nitrogen gas is introduced into the heating furnace.

[0011] S4. Cooling: The semi-sealed material box after heat treatment is cooled sequentially through a water cooling section and a door curtain air cooling section.

[0012] In the continuous furnace chamber formed by the preheating section, heating furnace, and water cooling section, the nitrogen flow distribution is controlled so that the nitrogen flow in the heating furnace area is greater than the nitrogen flow in the preheating section inlet and the water cooling section outlet area. The continuous nitrogen flow creates positive pressure in the furnace chamber, driving air away from the furnace inlet and outlet, ensuring that the furnace chamber is filled with nitrogen, and limiting the oxidation of iron-nickel alloy parts by physical isolation. In addition, the workpiece temperature at the outlet of the door curtain air cooling section is controlled to be lower than the workpiece oxidation temperature.

[0013] By adopting the above technical solution, the iron-nickel alloy parts are placed in a semi-sealed material box and nitrogen is introduced to replace the air, which can reduce the possibility of oxidation of the alloy parts when they come into contact with air during feeding. The nitrogen flow distribution is controlled in the continuous furnace formed by the preheating section, heating furnace and water cooling section, so that the nitrogen flow in the heating furnace area is large, forming a positive pressure to drive away the air, and limiting the oxidation of the alloy parts by physical isolation. Controlling the workpiece temperature at the outlet of the door curtain air cooling section to be lower than the oxidation temperature can reduce the possibility of oxidation of the alloy parts after cooling, ensure the chemical stability of the iron-nickel alloy parts in the whole heat treatment process, improve its surface smoothness, composition uniformity and functional consistency, and at the same time, there is no need to use ammonia decomposition atmosphere technology, which helps to reduce the possibility of problems such as high cost, flammability and explosion and affecting product performance.

[0014] Optionally, in step S1, the process of introducing nitrogen into the semi-sealed container is an automatic nitrogen filling process, until the oxygen content in the semi-sealed container is detected to be lower than a preset threshold.

[0015] By adopting the above technical solution, the automatic nitrogen filling process can accurately control the oxygen content in the semi-sealed material box, keeping it below the preset threshold, effectively expelling the air in the box, achieving efficient and precise air replacement, providing an oxygen-free or low-oxygen environment for subsequent heat treatment, and reducing the possibility of iron-nickel alloy parts being oxidized in the initial stage.

[0016] Optionally, in steps S2 and S3, the nitrogen flow rate introduced into the heating furnace is greater than the nitrogen flow rate introduced into the preheating section, and the nitrogen flow rate introduced into the preheating section is greater than the nitrogen flow rate introduced into the water cooling section.

[0017] By adopting the above technical solution and rationally allocating the nitrogen flow rate at different stages, a positive pressure can be better formed in the furnace, and air can be more effectively driven away from the furnace inlet and outlet, further ensuring that the furnace is filled with nitrogen and strengthening the physical isolation effect on the oxidation of iron-nickel alloy parts.

[0018] Optionally, in step S4, the workpiece temperature at the outlet of the air-cooled section of the door curtain is controlled to be below 60°C.

[0019] By adopting the above technical solution, the possibility of oxidation of iron-nickel alloy parts due to excessive temperature after cooling can be effectively reduced, further ensuring the surface quality and performance stability of the alloy parts and reducing the defect rate caused by oxidation.

[0020] Optionally, throughout the entire heat treatment process, from the inlet to the outlet, the iron-nickel alloy part is kept inside the semi-sealed material box and in a protective environment formed by nitrogen.

[0021] By adopting the above technical solution, the iron-nickel alloy parts are kept in a semi-sealed box and nitrogen protection environment throughout the heat treatment process. This reduces the possibility of the iron-nickel alloy parts coming into contact with the outside air, reduces the possibility of oxidation, decarburization or nitriding of the workpiece surface, ensures the surface finish, compositional uniformity and functional consistency of the alloy parts, improves the mechanical properties, electromagnetic properties and batch consistency of the products, and at the same time reduces the possibility of problems such as high cost, flammability and explosiveness of hydrogen and hydrogen embrittlement.

[0022] Secondly, this application provides a nitrogen-protected heat treatment system suitable for iron-nickel alloy parts, employing the following technical solution:

[0023] A nitrogen-protected heat treatment system for iron-nickel alloy parts includes a feeding device, a preheating furnace, a heating furnace, a water cooling device, and a curtain air cooling device arranged sequentially along the workpiece processing direction. The furnace chambers of the preheating furnace, the heating furnace, and the water cooling device are interconnected to form a continuous channel.

[0024] The feeding device includes a semi-sealed material box for accommodating the workpiece, and a nitrogen filling unit for providing nitrogen purging to the semi-sealed material box.

[0025] The heat treatment system also includes a nitrogen supply and control unit, which is connected to the nitrogen filling unit, the preheating furnace, the heating furnace and the water cooling device via pipelines, and is configured such that the nitrogen flow rate supplied to the heating furnace is greater than the nitrogen flow rate supplied to the inlet area of ​​the preheating furnace and the outlet area of ​​the water cooling device, so as to form a positive pressure nitrogen flow from the heating furnace to both ends in the continuous channel;

[0026] The curtain air-cooling device is configured to cool the workpiece to below its oxidation temperature before outputting it.

[0027] By adopting the above technical solution and employing a nitrogen-protected heat treatment process suitable for iron-nickel alloy parts, the problems of high cost, flammability, explosiveness, and impact on product performance caused by ammonia decomposition protective gas can be avoided. A feeding device, preheating furnace, heating furnace, water cooling device, and curtain air cooling device are sequentially arranged along the workpiece processing direction. The furnace chambers of the preheating furnace, heating furnace, and water cooling device are interconnected to form a continuous channel, allowing the heat treatment process of iron-nickel alloy parts to proceed continuously. The feeding device is equipped with a semi-sealed material box and a nitrogen filling unit, enabling the feeding and nitrogen replacement of iron-nickel alloy parts. The nitrogen supply and control unit supplies nitrogen to the heating furnace at a flow rate greater than that supplied to the preheating furnace inlet area and the water cooling device outlet area, creating a positive pressure nitrogen airflow from the heating furnace to both ends within the continuous channel. This displaces air from both ends of the channel, ensuring the channel is filled with nitrogen and physically isolating the iron-nickel alloy parts from oxidation. The curtain air cooling device cools the workpiece to below its oxidation temperature before outputting it, reducing the possibility of oxidation of the iron-nickel alloy parts after cooling.

[0028] Optionally, the end of the door curtain air-cooling device is equipped with a temperature monitoring unit for monitoring the temperature of the output workpiece.

[0029] By adopting the above technical solution, the temperature of the iron-nickel alloy parts after heat treatment can be accurately monitored, ensuring that the workpiece temperature is stably below 60℃, effectively reducing the possibility of oxidation of the workpiece at this stage, and ensuring the surface quality and performance stability of the iron-nickel alloy parts.

[0030] Optionally, the semi-sealed material box includes a lid and a box body, the box body having a material storage slot, and the lid covering the top of the box body;

[0031] The box lid has an air injection hole, and the box body has multiple vent holes that connect to the storage tank on its peripheral sidewalls and near the bottom.

[0032] The bottom of the box cover is provided with a support column, and a block is provided on the side of the support column away from the box cover, facing the air injection hole;

[0033] The box cover has multiple first ventilation holes along the trajectory surrounding the air injection hole, and the box body has multiple second ventilation holes that connect to the storage tank on its peripheral sidewalls and near the top.

[0034] A first sealing plate is slidably connected inside the box cover, and a first connecting hole is provided on the first sealing plate;

[0035] A second sealing plate is slidably connected inside the box, and a second connecting hole is provided on the second sealing plate;

[0036] The nitrogen filling unit includes a nitrogen filling tube, which is inserted into the gas injection hole;

[0037] The semi-sealed material box is equipped with a control component. When the nitrogen filling tube is inserted into the air injection hole, the control component controls the first sealing plate to slide and block the first air exchange hole, and controls the second sealing plate to slide and block the second air exchange hole.

[0038] When the nitrogen filling tube is detached from the gas injection hole, the control component controls the first sealing plate to slide to the first connecting hole and connect with the first air exchange hole, and controls the second sealing plate to slide to the second connecting hole and connect with the second air exchange hole.

[0039] By adopting the above technical solutions, the semi-sealed material box structure design facilitates nitrogen entry and air exhaust, achieving air replacement; the baffle can reduce the possibility of turbulence caused by direct nitrogen blowing, ensuring uniform airflow; when the nitrogen filling tube is inserted into the gas injection hole, the control component causes the first and second sealing plates to block the ventilation hole, reducing nitrogen leakage and improving nitrogen filling efficiency; when the nitrogen filling tube is removed from the gas injection hole, the control component connects the connecting hole with the ventilation hole, facilitating gas exchange during subsequent heat treatment, ensuring that the iron-nickel alloy parts are heat treated in a nitrogen-protected environment, reducing the possibility of oxidation, decarburization or nitriding, and ensuring the surface finish, compositional uniformity and functional consistency of the alloy parts.

[0040] Optionally, the control component includes a first spring and a second spring;

[0041] The first spring is installed inside the box cover. The first spring pushes the first sealing plate to slide into the air injection hole. The top of the first sealing plate is inclined and has a first pushing surface located inside the air injection hole.

[0042] When the nitrogen filling tube is inserted into the air injection hole, it slides on the first pushing surface, pushing the first sealing plate away from the air injection hole;

[0043] The first sealing plate has a clearance groove at its bottom, the second spring is installed inside the box, and the second sealing plate slides up and down on the box cover;

[0044] The second spring pushes the second sealing plate into the relief groove, at which point the second ventilation hole is connected to the second connecting hole;

[0045] The clearance groove has a sliding surface formed on the side wall near the air injection hole. When the first sealing plate moves away from the air injection hole, the second sealing plate slides on the sliding surface, pushing the second sealing plate downward until the second air exchange hole and the second connecting hole are misaligned.

[0046] By adopting the above technical solution, and utilizing the elastic action of the first and second springs, in conjunction with the sliding of the first and second sealing plates, the automatic opening and closing of the ventilation holes in the semi-sealed material box under nitrogen filling and non-nitrogen filling states is realized. This reduces manual operation, improves nitrogen filling efficiency and accuracy, and ensures the stability of the nitrogen protection environment inside the semi-sealed material box.

[0047] Optionally, the top of the second sealing plate is provided with mutually perpendicular fixing posts, and the sliding surface is provided with fixing grooves;

[0048] When the first sealing plate moves away from the air injection hole, the fixing post slides into the fixing groove until the first air exchange hole and the first connecting hole are misaligned, at which point the fixing post abuts against the bottom wall of the fixing groove.

[0049] By adopting the above technical solution, the cooperation between the fixed column and the fixed groove can accurately control the sliding position of the first sealing plate and the second sealing plate, ensuring that the first ventilation hole and the first connecting hole, and the second ventilation hole and the second connecting hole are accurately connected or misaligned, thereby improving the accuracy and stability of gas flow control in the semi-sealed material box during nitrogen replacement and heat treatment.

[0050] In summary, this application includes at least one of the following beneficial effects:

[0051] 1. Using nitrogen instead of ammonia decomposition gas as a protective gas reduces the cost of heat treatment processes and decreases expenses related to ammonia raw materials, energy consumption, maintenance, storage, and transportation of decomposition equipment.

[0052] 2. It reduces the possibility of hydrogen embrittlement caused by the strong reducing properties of hydrogen and surface micro-defects or compositional segregation caused by unstable nitrogen partial pressure, thus ensuring the mechanical properties, electromagnetic characteristics and batch consistency of iron-nickel alloy parts. Attached Figure Description

[0053] Figure 1 This is a schematic flow diagram of the heat treatment process according to an embodiment of this application;

[0054] Figure 2 This is a schematic diagram of the overall structure of the heat treatment system according to an embodiment of this application;

[0055] Figure 3This is a schematic diagram of the feeding device in the heat treatment system of this application embodiment;

[0056] Figure 4 This is a schematic diagram of the external structure of the semi-sealed material box in the heat treatment system of this application embodiment;

[0057] Figure 5 This is a schematic diagram of the internal structure of the semi-sealed material box in the heat treatment system of this application embodiment;

[0058] Figure 6 This is a schematic diagram of the structure of the first sealing plate in the heat treatment system of this application embodiment;

[0059] Figure 7 This is a schematic diagram of the structure of the second sealing plate in the heat treatment system of this application embodiment;

[0060] Figure 8 This is a schematic diagram of the water-cooling device and the curtain air-cooling device in the heat treatment system of the present application embodiment.

[0061] Reference numerals: 1. Feeding device; 2. Preheating furnace; 3. Heating furnace; 4. Water cooling device; 5. Door curtain air cooling device; 51. Temperature monitoring unit; 6. Semi-sealed material box; 61. Box cover; 611. Air injection hole; 612. Support column; 613. Stop block; 614. First ventilation hole; 615. First sealing plate; 6151. First pushing surface; 6152. Leaving groove; 6153. Sliding surface; 6154. Fixing groove; 616. First connecting hole; 62. Box body; 621. Material storage tank; 622. Exhaust hole; 623. Second ventilation hole; 624. Second sealing plate; 6241. Fixing column; 625. Second connecting hole; 7. Nitrogen filling unit; 71. Nitrogen filling pipe; 8. Nitrogen supply and control unit; 9. Control component; 91. First spring; 92. Second spring. Detailed Implementation

[0062] The following is in conjunction with the appendix Figure 1-8 This application will be described in further detail.

[0063] This application discloses a nitrogen-protected heat treatment process and system suitable for iron-nickel alloy parts.

[0064] Example 1

[0065] This application mainly adopts a nitrogen-protected heat treatment process for iron-nickel alloy parts, which achieves the effects of reducing costs, improving safety and product quality. The following is a further detailed description of this application.

[0066] See Figure 1 and Figure 2The nitrogen-protected heat treatment process for iron-nickel alloy parts provided in this application includes feeding and nitrogen replacement, preheating, heating, and cooling steps. By controlling the nitrogen flow distribution to ensure that the nitrogen flow rate in zone 3 of the heating furnace is greater than that in the preheating section inlet and the water-cooling section outlet, a positive pressure is created within the furnace to drive away air. Furthermore, the workpiece temperature at the outlet of the air-cooling section is controlled to be lower than the workpiece oxidation temperature, achieving the effect of physically isolating the iron-nickel alloy parts from oxidation, thus improving product quality and safety. This is because the continuous nitrogen flow creates positive pressure, effectively limiting air entry into the furnace and reducing the possibility of contact between the iron-nickel alloy parts and oxygen, while controlling the workpiece temperature below the oxidation temperature further prevents oxidation.

[0067] Specifically, in the feeding and nitrogen purging steps, the iron-nickel alloy parts are placed into a semi-sealed material box 6. The semi-sealed material box 6 can be a metal box with good sealing properties but not completely sealed; for example, it can be made of stainless steel. The shape of the semi-sealed material box 6 can be square or round. An injection port 611 is provided on the top of the semi-sealed material box 6. After the semi-sealed material box 6 is placed at the feeding station, nitrogen is introduced into the semi-sealed material box 6 through the injection port 611 to replace and expel the air inside the box. The introduction of nitrogen into the semi-sealed material box 6 is an automatic nitrogen purging process, which can be carried out using an automatic nitrogen purging device. The automatic nitrogen purging device can be a pipeline system with flow control and valves, and the nitrogen supply is automatically controlled by a controller.

[0068] During the preheating step, the semi-sealed material box 6, after nitrogen purging, is sent into the preheating section, while nitrogen is simultaneously introduced into the heat treatment furnace. The preheating section can be a channel equipped with a heating device, which can be a resistance wire heating element or a gas heating device. The introduced nitrogen can be supplied by a nitrogen supply system, which can be a system consisting of a nitrogen storage tank and pipelines.

[0069] During the heating step, the semi-sealed material box 6 is fed into the heating furnace 3 for heat treatment. The heating furnace 3 can be a box-type heating furnace 3 or a tunnel-type heating furnace 3. Nitrogen gas is also introduced into the heating furnace 3, and the flow rate of nitrogen gas introduced into the heating furnace 3 is greater than that introduced into the preheating section. This is because the temperature inside the heating furnace 3 is high, and the iron-nickel alloy parts are more prone to oxidation, requiring more nitrogen gas for protection.

[0070] In the cooling step, the heat-treated semi-sealed material box 6 is sequentially cooled through a water-cooling section and a curtain-cooling section. The water-cooling section can be a transport channel surrounding water-cooling pipes; as the semi-sealed material box 6 passes through this channel, the temperature within the channel is reduced by the cooling effect of the water-cooling pipes. The curtain-cooling section can be a channel with a curtain, where heat is carried away by airflow. The workpiece temperature at the outlet of the curtain-cooling section is controlled to be lower than the workpiece oxidation temperature, generally below 60°C. Temperature control can be achieved by adjusting the water temperature and flow rate in the water-cooling section and the airflow velocity in the curtain-cooling section.

[0071] Throughout the entire heat treatment process, from the inlet to the outlet, the iron-nickel alloy parts are kept in a semi-sealed material box 6 and a protective environment formed by nitrogen, which can prevent the oxidation of the iron-nickel alloy parts to the greatest extent.

[0072] The implementation principle of a nitrogen-protected heat treatment process for iron-nickel alloy parts according to Embodiment 1 of this application is as follows:

[0073] This embodiment uses nitrogen as a protective gas, which is less expensive than ammonia decomposition protective gas because nitrogen is widely available and inexpensive. It also reduces the risk of flammable and explosive hydrogen, improving production safety. By controlling the nitrogen flow distribution to create positive pressure, air is effectively isolated, reducing the possibility of oxidation of iron-nickel alloy parts. Furthermore, controlling the workpiece temperature at the outlet of the air-cooled section further reduces the risk of oxidation, improving product quality and batch consistency. This represents a significant improvement and contribution to existing technology.

[0074] Example 2

[0075] See Figure 2 The nitrogen-protected heat treatment system for iron-nickel alloy parts provided in this application includes a feeding device 1, a preheating furnace 2, a heating furnace 3, a water-cooling device 4, and a curtain air-cooling device 5 arranged sequentially along the workpiece processing direction. The furnace chambers of the feeding device 1, preheating furnace 2, heating furnace 3, and water-cooling device 4 are interconnected to form a continuous channel. The nitrogen flow distribution is controlled by a nitrogen supply and control unit 8, creating a positive pressure nitrogen airflow from the heating furnace 3 towards both ends within the continuous channel. The curtain air-cooling device 5 cools the workpiece to below its oxidation temperature before outputting it, effectively protecting the iron-nickel alloy parts from oxidation during heat treatment. This is because the positive pressure airflow drives air away from the furnace chamber, and the cooled workpiece temperature is below the oxidation temperature, further preventing oxidation.

[0076] See Figure 2 and Figure 3 Specifically, the feeding device 1 includes a semi-sealed material box 6 for accommodating the workpiece and a nitrogen filling unit 7 for providing nitrogen replacement for the semi-sealed material box 6.

[0077] The nitrogen purging unit 7 includes a nitrogen storage tank, sensors, pipes, valves, and a controller, used to achieve nitrogen purging. The nitrogen purging unit 7 is connected to an oxygen analyzer to monitor the oxygen concentration inside the semi-sealed container 6, and the nitrogen purging process is controlled based on the analyzer's readings. The oxygen analyzer provides real-time feedback on the oxygen content inside the semi-sealed container 6; when the oxygen content falls below a preset threshold, the controller closes the valves, stopping the nitrogen purging process.

[0078] See Figure 4 and Figure 5The semi-sealed material box 6 includes a lid 61 and a body 62. The body 62 has a storage groove 621 with its opening facing upwards. The lid 61 covers the top of the body 62 and seals the opening of the storage groove 621. A vertically extending air injection hole 611 is located in the center of the lid 61. Multiple horizontally extending vent holes 622, connecting to the storage groove 621, are located on the sidewalls of the body 62 near the bottom. The nitrogen filling unit 7 also includes a nitrogen filling pipe 71. During nitrogen filling, a sensor identifies the position of the semi-sealed material box 6, and then the nitrogen filling pipe 71 is inserted into the air injection hole 611 to inject nitrogen into the storage groove 621.

[0079] Two support pillars 612 are fixedly positioned at the bottom of the box cover 61. A stop block 613 is fixedly connected to the side of the support pillars 612 away from the box cover 61, facing the air injection hole 611. When nitrogen is injected through the air injection hole 611, the nitrogen first impacts the stop block 613, and then the stop block 613 changes the flow direction of the nitrogen, causing the nitrogen to diffuse in all directions along the top end of the stop block 613. At this time, the continuous injection of nitrogen causes the air in the storage tank 621 to be continuously discharged through the exhaust hole 622.

[0080] Multiple sets of first ventilation holes 614 are formed along the trajectory surrounding the air injection hole 611 on the lid 61. Each set of first ventilation holes 614 has multiple holes and is evenly spaced away from the air injection hole 611. Multiple sets of second ventilation holes 623 communicating with the storage tank 621 are formed along the trajectory surrounding the storage tank 621 on the side wall of the box body 62 near the top. Each set of second ventilation holes 623 has multiple holes and is evenly spaced in the vertical direction.

[0081] See Figure 4 and Figure 6 The box cover 61 has a first sealing plate 615 slidably connected inside. Each first sealing plate 615 corresponds to a group of first ventilation holes 614. The first sealing plate 615 has a first connecting hole 616, and the first connecting hole 616 corresponds one-to-one with the first ventilation hole 614 in the same group.

[0082] See Figure 5 and Figure 7 A second sealing plate 624 is slidably connected inside the box body 62. Each second sealing plate 624 corresponds to a set of second ventilation holes 623. A second connecting hole 625 is opened on the second sealing plate 624. The second connecting hole 625 corresponds one-to-one with the second ventilation holes 623 in the same set.

[0083] See Figure 3 and Figure 5 The semi-sealed material box 6 is equipped with a control component 9. When the nitrogen filling tube 71 is inserted into the air injection hole 611, the control component 9 controls the first sealing plate 615 to slide and seal the first ventilation hole 614 (the first ventilation hole 614 is in Figure 4When the nitrogen filling pipe 71 is disconnected from the air injection hole 611, the control component 9 controls the first sealing plate 615 to slide to the first connecting hole 616 and connect with the first air exchange hole 614, and controls the second sealing plate 624 to slide to the second connecting hole 625 and connect with the second air exchange hole 623.

[0084] Control component 9 includes a first spring 91 and a second spring 92; the first spring 91 is installed inside the cover 61, with one end of the first spring 91 abutting against the end of the first sealing plate 615 away from the air injection hole 611, and the other end abutting against the cover 61. When the first spring 91 is released elastically, it pushes the first sealing plate 615 to slide into the air injection hole 611, at which time the first ventilation hole 614 (the first ventilation hole 614 is in) Figure 4 The first sealing plate 615 (marked out) is interconnected with the first connecting hole 616. The top of the first sealing plate 615 has an inclined first pushing surface 6151, which is located inside the gas injection hole 611. When the nitrogen filling tube 71 is inserted into the gas injection hole 611, the nitrogen filling tube 71 slides on the first pushing surface 6151. At this time, the nitrogen filling tube 71 pushes the first sealing plate 615 into the cover 61, causing the first sealing plate 615 to move away from the gas injection hole 611. At this time, the first ventilation hole 614 and the first connecting hole 616 are misaligned, achieving the sealing of the first ventilation hole 614 by the first sealing plate 615, reducing the possibility of nitrogen leakage during gas injection.

[0085] See Figure 5 and Figure 6 The second spring 92 is installed inside the box body 62, with its top abutting against the bottom of the second sealing plate 624 and its bottom abutting against the box body 62. When the second spring 92 is released elastically, it pushes the second sealing plate upward. In the initial state, the second spring 92 pushes the second sealing plate 624 upward to slide out of the box body 62. The bottom of the box cover 61 has a sliding groove, and the second sealing plate 624 slides up and down in the sliding groove. The bottom of the first sealing plate 615 has a clearance groove 6152, which is connected to the sliding groove. When the box cover 61 is placed on top of the box body 62, the second sealing plate 624 is positioned by sliding into the sliding groove, and the top of the second sealing plate 624 is simultaneously inserted into the clearance groove 6152. At this time, the second ventilation hole 623 is connected to the second connecting hole 625.

[0086] A sliding surface 6153 is formed on the side wall of the clearance groove 6152 near the air injection hole 611. When the first sealing plate 615 moves away from the air injection hole 611, the second sealing plate 624 slides on the sliding surface 6153, pushing the second sealing plate 624 to slide downward until the second air exchange hole 623 is misaligned with the second connecting hole 625.

[0087] See Figure 6 and Figure 7The second sealing plate 624 has mutually perpendicular fixing posts 6241 at its top. The fixing posts 6241 slide up and down in a sliding groove and a clearance groove 6152, and the shape of the sliding groove is adapted to the second sealing plate 624 and the fixing posts 6241. A fixing groove 6154 is formed on the sliding surface 6153, corresponding to the fixing post 6241. When the first sealing plate 615 moves away from the air injection hole 611 (the air injection hole 611 is in...), Figure 5 When the bid is won, the fixing post 6241 slides into the fixing groove 6154 until the first ventilation hole 614 (the first ventilation hole 614 is in Figure 4 When the first connecting hole 616 is misaligned with the winning bid, the second sealing plate 624 drives the fixing post 6241 to slide downward and abut against the bottom wall of the fixing groove 6154. At this time, the cover 61 and the box body 62 are fixedly connected, reducing the amount of nitrogen gas flowing out of the cover 61 during gas injection. Figure 5 (Winning bid) and box 62 (box 62 in) Figure 5 The gap between the marked points may overflow.

[0088] See Figure 2 The preheating furnace 2 can be a tunnel furnace body that uses resistance wire heating, and has a temperature sensor and heating controller inside, which can accurately control the preheating temperature.

[0089] See Figure 8 The heating furnace 3 can be a gas-fired box furnace with high heating efficiency. The water cooling device 4 can be a unit with a circulating water pump, a cooling water tank, and water supply pipes. Water flow holes are opened inside the walls of the water cooling pipes. There are two water supply pipes, each connected to one of the two openings of the water flow holes in the water cooling pipes. One water supply pipe extends into the cooling water tank, and the other is connected to the outlet of the circulating water pump, which is installed inside the cooling water tank. During cooling, the circulating water pump draws water from the cooling water tank and transmits it to the water flow holes in the water cooling pipes through the water supply pipes. The water then flows from the water supply pipe on the other side of the water flow holes into the cooling water tank, achieving water circulation and removing heat. The curtain air cooling device 5 can be a passageway with a curtain and a fan inside. The fan accelerates airflow to cool the workpiece.

[0090] See Figure 2 and Figure 3 The nitrogen supply and control unit 8 is connected to the nitrogen filling unit 7, preheating furnace 2, heating furnace 3, and water cooling device 4 via pipelines. This unit can be a pipeline system with flow control valves and pressure sensors, adjusting the nitrogen flow rate by controlling the valve opening. The nitrogen flow rate supplied to the heating furnace 3 is greater than the nitrogen flow rate supplied to the inlet area of ​​the preheating furnace 2 and the outlet area of ​​the water cooling device 4, so as to form a positive pressure nitrogen flow from the heating furnace 3 to both ends in a continuous channel.

[0091] The end of the door curtain air-cooling device 5 is equipped with a temperature monitoring unit 51, such as an infrared temperature sensor, to monitor the output workpiece temperature and ensure that the temperature is below 60°C. When the temperature is above 60°C, the fan speed or the water flow rate of the water-cooling device 4 can be adjusted to further reduce the workpiece temperature.

[0092] The implementation principle of a nitrogen-protected heat treatment system for iron-nickel alloy parts according to Embodiment 2 of this application is as follows:

[0093] The heat treatment system in this embodiment utilizes nitrogen gas to protect iron-nickel alloy parts from oxidation during heat treatment through the coordinated operation of various devices. The nitrogen supply and control unit 8 precisely controls the nitrogen flow rate, creating a positive pressure airflow and effectively reducing air entering the furnace. The cooperation between the temperature monitoring unit 51 and the cooling device ensures that the workpiece temperature is below the oxidation temperature after cooling, improving product quality and production safety. Compared with existing systems that use ammonia decomposition as a protective gas, this system is lower in cost, has better performance, and represents a significant improvement over existing technologies.

[0094] 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 nitrogen-protected heat treatment process suitable for iron-nickel alloy parts, characterized in that, Includes the following steps: S1. Loading and nitrogen replacement: Load the iron-nickel alloy parts into the semi-sealed material box (6), place the semi-sealed material box (6) at the loading station, and introduce nitrogen into the semi-sealed material box (6) to replace and expel the air in the box. S2. Preheating: The semi-sealed material box (6) that has completed nitrogen replacement is sent into the preheating section, and nitrogen is introduced into the heat treatment furnace. S3. Heating: The semi-sealed material box (6) is sent into the heating furnace (3) for heat treatment, and nitrogen gas is introduced into the heating furnace (3). S4. Cooling: The semi-sealed material box (6) after heat treatment is cooled sequentially through a water cooling section and a door curtain air cooling section; In the continuous furnace chamber formed by the preheating section, heating furnace (3) and water cooling section, the nitrogen flow distribution is controlled so that the nitrogen flow in the heating furnace (3) area is greater than the nitrogen flow in the preheating section inlet and the water cooling section outlet area. The continuous nitrogen flow creates positive pressure in the furnace chamber, driving air away from the furnace inlet and outlet, ensuring that the furnace chamber is filled with nitrogen, and limiting the oxidation of iron-nickel alloy parts by physical isolation. In addition, the workpiece temperature at the outlet of the door curtain air cooling section is controlled to be lower than the workpiece oxidation temperature. The semi-sealed material box (6) includes a lid (61) and a body (62). The body (62) has a storage slot (621), and the lid (61) covers the top of the body (62). The box cover (61) has an air injection hole (611), and the box body (62) has multiple exhaust holes (622) that connect to the storage tank (621) on its peripheral side wall and near the bottom. The bottom of the box cover (61) is provided with a support column (612), and a stop block (613) is provided on the side of the support column (612) away from the box cover (61) facing the air injection hole (611). The lid (61) has a plurality of first ventilation holes (614) along the trajectory surrounding the air injection hole (611), and the box body (62) has a plurality of second ventilation holes (623) connecting the storage tank (621) on its periphery and near the top. The box cover (61) is slidably connected to a first sealing plate (615), and a first connecting hole (616) is provided on the first sealing plate (615). A second sealing plate (624) is slidably connected inside the box body (62), and a second connecting hole (625) is provided on the second sealing plate (624). In step S1, nitrogen gas is introduced into the semi-sealed material box (6) by inserting the nitrogen filling tube (71) of a nitrogen filling unit (7) into the gas injection hole (611); The semi-sealed material box (6) is provided with a control component (9). When the nitrogen filling tube (71) is inserted into the air injection hole (611), the control component (9) controls the first sealing plate (615) to slide and seal the first air exchange hole (614), and controls the second sealing plate (624) to slide and seal the second air exchange hole (623). When the nitrogen filling tube (71) is disengaged from the air injection hole (611), the control component (9) controls the first sealing plate (615) to slide to the first connecting hole (616) and connect with the first air exchange hole (614), and controls the second sealing plate (624) to slide to the second connecting hole (625) and connect with the second air exchange hole (623).

2. The nitrogen-protected heat treatment process for iron-nickel alloy parts according to claim 1, characterized in that: In step S1, nitrogen gas is introduced into the semi-sealed material box (6) as an automatic nitrogen filling process until the oxygen content in the semi-sealed material box (6) is detected to be lower than a preset threshold.

3. The nitrogen-protected heat treatment process for iron-nickel alloy parts according to claim 1, characterized in that: In steps S2 and S3, the nitrogen flow rate introduced into the heating furnace (3) is greater than the nitrogen flow rate introduced into the preheating section, and the nitrogen flow rate introduced into the preheating section is greater than the nitrogen flow rate introduced into the water cooling section.

4. The nitrogen-protected heat treatment process for iron-nickel alloy parts according to claim 1, characterized in that: In step S4, the workpiece temperature at the outlet of the air-cooling section of the door curtain is controlled to be below 60°C.

5. A nitrogen-protected heat treatment process for iron-nickel alloy parts according to any one of claims 1-4, characterized in that: Throughout the entire heat treatment process, from the inlet to the outlet, the iron-nickel alloy part remains inside the semi-sealed material box (6) and in a protective environment formed by nitrogen.

6. A nitrogen-protected heat treatment system for iron-nickel alloy parts, employing a nitrogen-protected heat treatment process for iron-nickel alloy parts as described in any one of claims 1-5, characterized in that: The device includes a feeding device (1), a preheating furnace (2), a heating furnace (3), a water cooling device (4), and a door curtain air cooling device (5) arranged sequentially along the workpiece processing direction. The furnace chambers of the preheating furnace (2), the heating furnace (3), and the water cooling device (4) are interconnected to form a continuous channel. The feeding device (1) includes a semi-sealed material box (6) for accommodating the workpiece, and a nitrogen filling unit (7) for providing nitrogen replacement for the semi-sealed material box (6). The heat treatment system also includes a nitrogen supply and control unit (8), which is connected to the nitrogen filling unit (7), the preheating furnace (2), the heating furnace (3) and the water cooling device (4) via pipelines, and is configured such that the nitrogen flow rate supplied to the heating furnace (3) is greater than the nitrogen flow rate supplied to the inlet area of ​​the preheating furnace (2) and the outlet area of ​​the water cooling device (4), so as to form a positive pressure nitrogen flow from the heating furnace (3) to both ends in the continuous channel; The door curtain air-cooling device (5) is configured to cool the workpiece to below its oxidation temperature before outputting it.

7. A nitrogen-protected heat treatment system for iron-nickel alloy parts according to claim 6, characterized in that: The end of the door curtain air cooling device (5) is provided with a temperature monitoring unit (51) for monitoring the temperature of the output workpiece.

8. A nitrogen-protected heat treatment system for iron-nickel alloy parts according to claim 7, characterized in that: The control component (9) includes a first spring (91) and a second spring (92); The first spring (91) is installed inside the cover (61). The first spring (91) pushes the first sealing plate (615) to slide into the air injection hole (611). The top of the first sealing plate (615) is inclined to have a first pushing surface (6151) located in the air injection hole (611). When the nitrogen filling tube (71) is inserted into the gas injection hole (611), it slides on the first pushing surface (6151) and pushes the first sealing plate (615) away from the gas injection hole (611). The first sealing plate (615) has a clearance groove (6152) at the bottom, the second spring (92) is installed in the box body (62), and the second sealing plate (624) slides up and down on the box cover (61). The second spring (92) pushes the second sealing plate (624) into the relief groove (6152), at which time the second ventilation hole (623) is connected to the second connecting hole (625); The clearance groove (6152) has a sliding surface (6153) formed on the side wall of the groove near the air injection hole (611). When the first sealing plate (615) moves away from the air injection hole (611), the second sealing plate (624) slides on the sliding surface (6153), pushing the second sealing plate (624) to slide down until the second air exchange hole (623) and the second connecting hole (625) are misaligned.

9. A nitrogen-protected heat treatment system for iron-nickel alloy parts according to claim 8, characterized in that: The second sealing plate (624) is provided with mutually perpendicular fixing posts (6241) at the top, and the sliding surface (6153) is provided with fixing grooves (6154). When the first sealing plate (615) moves away from the air injection hole (611), the fixing post (6241) slides into the fixing groove (6154) until the first air exchange hole (614) and the first connecting hole (616) are misaligned, the fixing post (6241) abuts against the bottom wall of the fixing groove (6154).

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